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Coprecipitation magnesium(II) hydroxide as a strategy of pre-concentration for trace elemental determination by microwave-induced plasma optical emission spectrometry
Abstract and Figures
In this work, a method employing coprecipitation procedure with magnesium hydroxide as a carrier for separation/preconcentration of arsenic(V), cadmium(II), chromium(III), cobalt(II), copper(II), manganese(VII), mercury(II), nickel(II), and vanadium(V) was developed. The method was applied in fish and shellfish samples, and the elements were determined by microwave-induced plasma optical emission spectrometry (MIP OES). Complete two-level factorial design for four variables and a mixture design were employed to evaluate and optimize the factors involved in this system. Under optimized conditions, the accuracy of the procedure was assessed using certified reference material, obtaining recoveries of 92 to 105% for the elements studied. The proposed method presented the detection limits in the range of 0.01–0.33 μg g⁻¹, and enrichment factors of 5; 17; 6; 25; 24; 25; 25; 25; and 13 for the analytes As⁵⁺, Cd²⁺, Cr³⁺, Co²⁺, Cu²⁺, Mn⁷⁺, Hg²⁺, Ni²⁺, and V⁵⁺, respectively. The applied chemometric tools were effective to optimize the important variables involved in the developed coprecipitation route. The proposed method presented simplicity, low cost, high sensitivity, allowing the determination of the analytes by MIP OES.
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... These include liquid-liquid extraction, 17 cloud point extraction, 6,18 solid-phase extraction (SPE) 7,[19][20][21][22] and co-precipitation. 23 Recently Ninwong, et al. 24 demonstrated a paper-based method coupled with heating pre-concentration for the determination of Ni in water samples to enhance the analytical signal. However, the use of heating would incur complexity and time in the procedure. ...
... 25,26 Among the cited procedures, coprecipitation stands out for its advantages in its implementation, such as simplicity, speed, low solvent consumption, and ability to achieve high enrichment factors. 23,[26][27][28] Co-precipitation of Ni ion using Mg(OH) 2 has been previously demonstrated as a sample preparation technique prior to analysis with the conventional method. 23 In the co-precipitation procedure, a precipitate is formed by combining a carrier element and a suitable inorganic ligand. ...
... 23,[26][27][28] Co-precipitation of Ni ion using Mg(OH) 2 has been previously demonstrated as a sample preparation technique prior to analysis with the conventional method. 23 In the co-precipitation procedure, a precipitate is formed by combining a carrier element and a suitable inorganic ligand. 9 The co-precipitation can be associated with metal adsorption on the precipitate surface or metal incorporation onto the precipitate structures. ...
A simple, fast, low-cost and sensitive microfluidic paper-based analytical device (u-PADs) integrated with the co-precipitation enrichment procedure was developed to analyse Ni(II) in tap and mineral water samples. The impacting factors, including pH, centrifugation (5 min at 4000 rpm), and amounts of reagents were optimized. The limit of detection of 0.009 mg L-1 and linear range of 0.03-2.00 mg L-1 were achieved with good intra- and inter-day precision (4.7 and 5.6% RSD, respectively). The recovery tests were conducted by spiking tap and mineral water samples and analyzed using the u-PADs after co-precipitation enrichment. The results obtained by the proposed method were validated by inductively coupled plasma-optical emission spectrometry (ICP-OES). The recoveries of the present method and ICP-OES were ranged from 92.4-106.8% and 92.9-97.2%, respectively. The two sets of (u-PADs and ICP-OES) results were in good agreement, as a paired t-test indicated no significant differences. The proposed method could be utilized for analyzing trace levels of Ni(II) in water samples in developing countries where the availability of conventional analytical instruments are significant problems.
... However, in most circumstances, the sensitivity of FAAS and also other instrumental methods may not be adequate for accurately analyzing metal ions at very low levels in complex sample matrices. To overcome this limitation, a variety of separation and preconcentration procedures including flotation , cloud point extraction (Li et al. 2022), membrane filtration (Xiang et al. 2022), liquid-liquid extraction (Nyamato et al. 2022), solid phase extraction (Zhao et al. 2021), and co-precipitation (Moreira et al. 2020) are applied in conjunction with FAAS to enhance sensitivity and improve the precision of metal ion determination. ...
... The inclusion, occlusion, and surface adsorption mechanisms are effective in the accumulation of the HMs ). In the case of inorganic co-precipitation, trace elements are deposited onto the precipitate formed by different metal hydroxides (Saracoglu et al. 2012;Mohammadi et al. 2019;Moreira et al. 2020). Conversely, organic co-precipitation involves the addition of a significant quantity of carrier element (Bi, Cu, Co, and Ni) to the medium, resulting in the formation of water-insoluble complexes with ligands like N-benzoyl-N-phenyl-hydroxylamine (Saçmacı & Kartal 2010), 4-(2-Pyridylazo)-resorcinol (Tokalıoglu & Dasḑelen 2011), pyrrolidine dithiocarbamate (Baysal et al. 2008), and 8-Hydroxyquinoline (Feist & Mikula 2014). ...
Elimination of the matrix effect is a major challenge in developing a method for the quantification of heavy metals (HMs) in water samples. In this regard, the current research describes the simultaneous analyses of Cu(II), Cd(II), and Ni(II) ions in water matrices through flame atomic absorption spectrophotometry (FAAS) after preconcentration with carrier element-free co-precipitation (CEFC) technique by the help of an organic co-precipitant, 3-{[5-(4-Chlorobenzyl)-3-(4-chlorophenyl)-1H-1,2,4-triazol-1-yl]-methyl}-4-[2,4-(dichlorobenzylidene)amino]-1H-1,2,4-triazole-5(4H)-thione (CCMBATT). Based on our literature research, CCMBATT was employed for the first time in this study as an organic co-precipitant for the preconcentration of HMs. Factors such as solution pH, concentration of co-precipitant, sample volume, standing time, centrifugation rate, and time were thoroughly examined and optimized to achieve the highest efficiency in terms of HM recovery. The limits of detection (LODs) (with 10 number of tests) of 0.54, 0.34, and 1.95 μg L−1 and the relative standard deviations (RSD %) of 2.1, 3.3, and 3.0 were determined for Cu(II), Cd(II) and Ni(II) ions, respectively. Recovery results of HMs for the spiked samples were in the range of 92.8–101.0%, demonstrating the trueness of the method and its applicability to the water samples matrix.
... Sediment could act as a reservoir o elements, which may provide the (re)availability o mercury and increase bioaccumulation and biomagnication in the marine aune. 5,13,15,16 Studies on uncontaminated areas show values o Hg in the order o 10 μg kg −1 or lower than 130 μg kg −1 , that is, the threshold eects level (TEL) dened as the upper limit o contaminant concentrations in sediments without adverse eects on the biota. 17,18 For contaminated areas, contamination o Hg in sediments can vary rom TEL up to values as high as 19,800 μg kg −1 . ...
Mercury (Hg) determination in marine sediment is an analytical challenge due to the toxicity of this element even at low concentrations (up to 130 μg kg–1 in marine sediments) and complex matrices. Therefore, it is necessary to use analytical techniques that have high sensitivity, selectivity, and low limits of quantification (LoQ). In this study, two methods that require sample treatment and one method with direct sampling were studied. The techniques studied were inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectrometry with cold vapor generation (CV-ICP-OES), and atomic absorption spectrometry with thermodecomposition and amalgamation (TDA AAS) for Hg determination in marine sediment samples. Since ICP-MS has more studies in the literature, optimization with design of experiments was developed for CV-ICP-OES and TDA AAS. Although it was found to have low levels of instrumental LoQ for all three techniques, differences were found once the method LoQ was calculated. The calculation for method LoQ considers all analytical procedures executed, including sample treatment, which provides a 100-fold dilution for ICP-MS and CV-ICP-OES. The method LoQ obtained were 1.9, 165, and 0.35 μg kg–1 for ICP-MS, CV-ICP-OES, and TDA AAS, respectively. Comparing marine sediment sample analyses, Hg concentrations had no statistical difference when determined by ICP-MS and TDA AAS. It was not possible to determine Hg in marine sediment samples by CV-ICP-OES due to the high method LoQ obtained (165 μg kg–1). Although ICP-MS has the advantage of being a multielemental technique, it is high-value equipment and needs a large volume of argon, which has a high cost in the market, and it requires sample treatment. On the other hand, TDA AAS-based spectrometer DMA-80 performs direct sampling, avoiding the pretreatment stage, and has a relatively lower cost, both in terms of initial investment and maintenance, while maintaining the high sensitivity, accuracy, and precision required for Hg determination on marine sediment samples.
... Metal hydroxides using co-precipitation of a single M 2+ (e.g., Mg 2+ ) or M 3+ (e.g., Al 3+ ) ion under alkaline conditions have been highlighted for their ability to modify and become attractive as green adsorbents due to their nontoxicity, simplicity, rapidity, and in situ formation process. A Mg(OH) 2 co-precipitate form is the most frequently used for preconcentration or removal of various inorganic species (Zhu 2020;Moreira et al. 2020;Tsuchiya et al. 2020), and organic compound (Tsai et al. 2010). Meanwhile, Al(OH) 3 coprecipitation strategies were initially developed for the purpose of determining organic compounds, such as organophosphorus pesticides (Mammana et al. 2017), estrogen (Xiao et al. 2013), and tetracyclines . ...
A magnesium hydroxide co-precipitation sorbent-based method in the presence of an anionic surfactant (e.g., sodium dodecylbenzenesulfonate) and high-performance liquid chromatography were used to preconcentrate and analyze fungicides in water and apple juice samples. The preconcentration procedure can be accomplished in a single step based on the co-precipitation of target fungicides and magnesium chloride in the presence of surfactant in a sodium hydroxide solution (pH 11) and a white precipitate gel was simply obtained after centrifugation. The property of precipitate phase was subsequently characterized using Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray diffractometry. Under the optimum conditions, the developed method exhibited good sensitivity, with an enrichment factor of 11–18 and limits of detection of approximately 1–5 μg/L for water samples and 7–10 μg/L for apple juices. High reproducibility was achieved with a relative standard deviation of less than 11%, and a good recovery range of 72% to 120% was also obtained. The proposed method was shown to be a simple preconcentration procedure for concentrating fungicides in the samples investigated.
... Several enrichment procedures involving various analytical techniques, such as membrane filtration [13,14], coprecipitation [15][16][17][18][19][20][21], solid-phase extraction [22][23][24][25][26][27][28][29], cloud point extraction [30][31][32][33][34][35], and liquidliquid microextraction [36][37][38][39][40][41], have been developed for the determination of Co(II) and Ni(II). ...
A new, green, simple, and validated ultrasound-assisted dispersive microsolid-phase extraction method applying unprecedented adsorbent-modified multiwalled carbon nanotubes was achieved for preconcentration and separation of trace cobalt (Co(II)) and nickel (Ni(II)) ions in diverse ecological samples before determination by flame atomic absorption spectrometry. The suggested approach uses a novel chelating agent named 3-(2,4-dihydroxyphen-1-ylazo)-1,2,4-triazole, which is chelated with Co(II) or Ni(II) ions as efficient and selective sorbent at pH 8.0. The impact of many parameters has been studied and optimized. Under ideal conditions, the calibration curves were linear within 1.0–200 and 2.0–300 μg/L ranges, with limits of detection equaling 0.30 and 0.60 μg/L for Co(II) and Ni(II) ions, respectively. The preconcentration factor attained 200, while the highest sorption capacities of Co(II) and Ni(II) are around 300 and 380 mg/g, respectively. The relative standard deviation (%RSD) regarding repeatability for Co(II) and Ni(II) upon calculation was 1.30 and 1.70% for intraday, and 1.750 and 1.95% for interday. To ensure the correctness of the suggested preconcentration approach, certified reference materials (SRM 1570A spinach leaves and TMDA-52.3 enriched water) were employed. The proposed approach was applied to determine the concentration of Co(II) and Ni(II) ions in a range of genuine water, juice, and food samples, and the findings were excellent.
... In this context, several strategies have been investigated to minimize these limitations, such as hydride generation, cold vapor (Lima et Coprecipitation is a remarkable separation/preconcentration method, MIP OES still requires research. It has advantages such as simplicity, low consumption of reagents, and high preconcentration factor, which are essential in the determination of trace elements (Moreira et al. 2020). In addition, multiple analytes can be separated and pre-concentrated in a single matrix step using different organic or inorganic precipitants Tuzen Table 9. ...
A Box-Behnken design approach was used to plan the experiments for As and Cd determination in fish samples. It combines microwave-induced plasma optical emission spectrometry (MIP OES) with silver nitrate and potassium chromate coprecipitation. Multiple Response methodology (MR) has been adopted to express the output parameters (responses) that are decided by the input process parameters. MR also quantifies the relationship between the variable input parameters and the corresponding output parameters. Factors that directly affect the coprecipitation procedure, such as silver and chromate concentrations and solvent volume, were optimized. The optimized conditions were 5.46 x10 − 4 mol L − 1 [CrO 4 ²⁻ ] and 1.16 x10 − 3 [Ag ⁺ ], without needed of solvent addition. The procedure provided preconcentration factors of 25 and 11 for As and Cd, respectively, and LOD adequate to the international legislation. The trueness was assessed with the analysis of certified reference materials (CRMs) and compared with inductively coupled plasma mass spectrometry (ICP-MS). Relative standard deviations < 9% and 3.5% and recoveries > 91% and 88% were obtained for As and Cd, respectively. The method was applied to local market fish samples and showed suitability for As and Cd determination by MIP OES.
... Multiple approaches to preconcentrate and separate Ni(II) have lately been published in the literature, including cloud point extraction [4][5][6][7][8][9][10][11][12], solid-phase extraction [13][14][15][16], membrane filteration [17], and co-precipitation [18][19][20]. ...
An eco-friendly and easy ultrasound-assisted liquid phase microextraction approach using deep eutectic solvent (UA-DES-LPME) was established to preconcentrate and separate trace amount of nickel (Ni(II)) in various environmental samples before flame atomic absorption spectrometric estimation. In this method, Ni(II) was complexed with 2-(benzothiazolyl azo) orcinol reagent. The impacts various parameters on the microextarction of Ni(II) was investigated. The calibration graph is linear in the range of 1–500 µg L ⁻¹ and limits of detection and quantification were determined as 0.27 and 0.90 μg L ⁻¹ , respectively. The RSD% and preconcentration factor were 2.30% and 100, respectively. The analysis of certified reference materials demonstrated the validity of the established procedure. The microextraction method provided here simple, rapid, cheap, green and was effectively used to determine nickel levels in a variety of environmental samples with recoveries ranged of 95.0–98.54%.
... 2 The coprecipitation technique is based on the accumulation of metal ions on water-insoluble precipitates of various organic or inorganic characters. 17 In general, in the coprecipitation method two types of reagents are used; i) inorganic coprecipitants such as hydroxides and sulphides [18][19][20][21][22][23] ii) organic coprecipitants such as some chelates or chelating ligands. 1,9 However, in both cases, the carrier element, which is added to the medium in excessive amounts for precipitate formation, may have interference effects during the analysis step. ...
In the present investigation, the application of an organic coprecipitant, 2- [5,6-dichloro-2-(2-bromobenzyl)-1H-benzimidazole-1-yl]acetohydrazide (DIBBA), for separation and preconcentration of Cu(II) ions in fruit and water samples through a new carrier element free coprecipitation (CEFC) method was researched for the first time. Flame atomic absorption spectrometer (FAAS) was utilized for the analyses of Cu(II) ions. The main effective experimental factors such as solution pH, DIBBA quantity, waiting time, centrifuge speed and duration and volume of sample on the recovery efficiency of Cu(II) ions were explored in detail. Under the optimized conditions the preconcentration factor (PF), relative standard deviation (RSD), and limits of detection (LOD) was achieved as 50, 3.4 %, and 0.44 ?g L-1, respectively. No interference effects were detected by virtue of the presence of various foreign ions. Satisfactory recoveries (in the range of 94.4 to 103.0 %) in the environmental sample matrix were acquired. After being validated the recommended selective, low cost, simple and rapid CEFC method by spike/recovery tests, it was featly implemented for the low levels detection of Cu(II) ions in sour cherry, mulberry, apple, and peach as fruit samples and stream and sea water samples without any significant matrix effects.
... These strategies showed good results and demonstrated excellent analytical capacity and robustness. The MIP OES has already been used in different applications in elementary quantification in samples of fish (Gallego Ríos et al. 2017;Nyeste et al. 2019;Moreira et al. 2020;Sá et al. 2020) and food (Ozbek et al. 2019;Bonemann et al. 2020;Carvalho et al. 2020). ...
In this study, the concentrations of macro- and microelement in different tissues (liver, gill, and muscle) of fish collected (Mugil cephalus) in Pontal Bay (Ilhéus, Bahia) were determined. A simplex-centroid mixture design was used to obtain the mixture applied to the decomposition of the samples. The elementary determination was made by microwave-induced plasma optical emission spectrometry (MIP OES), and the Kohonen self-organizing map (KSOM) was applied as an exploratory analysis tool. The accuracy of the procedure was assessed using certified reference material. Recoveries were obtained in the range of 99–103% and without a statistical difference (95% confidence level). Precision was estimated from the relative standard deviation, which ranged from 0.3 to 2.2%, and the limits of detection (mg kg−1) were 0.145 (Cu), 1.53 (Fe), 1.61 (K), 0.250 (Mg), 0.040 (Mn), 4.84 (P), and 2.12 (Zn). The KSOM provided efficient and precise separation of the studied tissues into three groups. The concentrations of Cu, Fe, and Zn were higher in the liver, while in the gills, they were the Mn.
This 4-th edition of the chapter "Microwave Plasma Systems in Optical and Mass Spectrometry" is probably the most comprehensive and up-to-date paper on analytical applications of surprisingly many microwave plasma spectrometric techniques.
also published on-line
https://onlinelibrary.wiley.com/doi/book/10.1002/9780470027318
A facile and sensitive method predicated on carrier element free coprecipitation (CEFC) using 2-(2-(2-(4-bromobenzyl)-1H-benzo[d]imidazole-1-yl)acetyl)-N-ethylhydrazine-1-carbothioamide (BIMANEC) is reported for trace determination of Cu(II) and Cd(II) in vegetables and water. BIMANEC was used for the first time for the quantitative determination of these trace heavy metals. Flame atomic absorption spectrometer (FAAS) was used for quantitation. The preconcentration conditions were optimized with respect to pH (8.0), BIMANEC mass (4.0 mg), volume of sample (100 mL), standing time (5 min), and centrifugation time and rate (3 min and 2500 rpm). The influence of potentially interfering ions was scrutinized for the recovery of analyte ions. Under the optimum conditions, the limits of detection (LODs) were 0.51 and 2.28 µg L⁻¹ for Cu(II) and Cd(II), respectively. The relative standard deviations were < 5% for both. The recoveries from the spiked vegetable samples were from 94.9 to 102.8% and from the spiked water samples between 93.2 and 101.6%. Consequently the developed new, facile, rapid, and highly efficient CEFC process was employed for the trace determination of Cu(II) and Cd(II).
Eichornia crassipes is an atypical plant in the various regions of the Caribbean’s Central America e South American Countries. This plant causes severe problems in the aquatic environment of these places. Thus, it is necessary to remove this plant from the aquatic ecosystem causing immense environmental benefit. One alternative is transforming this plant into a solid low-cost phase for analytical methodologies and enabling cost reduction in the analysis of environmental pollutants. Toxic metal elements like lead have not function in the human body. It is crucial to determine lows concentrations of metals in water, foods, and beverages to assess daily consumption permissibility. Flame atomic absorption spectrometry (FAAS), compared to more sensitive equipment, is low-cost, easy-to-operate equipment, above all high precision and specificity. Their lack of sensitivity can be overcome with a preconcentration methodology. This work aims to transform the leaves of Eichornia crasipes into a new green solid-phase and find the best extraction conditions for Pb (II) determination by solid phase extraction (SPE) online with FAAS. The leaves of the plant were collected, washed with water, dried at room temperature, oven, milled, and sifted. The solid-phase extraction parameters, such as pH, type of eluent, sample flow rate, amount of sorbent, and eluent flow rate, were optimized. An experimental factorial design 2⁴ was applied with the sample flow, eluent flow, column mass, and volume of complexing agent. The two-dimensional central and rotating composite design was applied to the variables that obtained significance through experimental design. The elimination of a complexing agent allowed the methodology to become more compatible with the principles of green chemistry. The enrichment factor and the limit of detection were 48.5 and 2.35 μg L⁻¹, respectively. The method was validated with SRM 1515 certified reference material. The SPE-FAAS online methodology with a minicolumn of Eichhornia crassipes is a simple, fast, economical, safe, and eco-friendly alternative for the determination of Pb(II).
The dispersive liquid–liquid microextraction (DLLME) was evaluated as a strategy to improve the MIP OES sensitivity for molybdenum determination in lamb meat. Initially, the dispersive (methanol) and extracting (tetrachloromethane) solvents were selected based on a mixture design. The best results were achieved with methanol and carbon tetrachloride as dispersive and extracting solvent, respectively. The operational parameters, such as pH, volume of dispersive and extractant solvents, and complexing agent concentration (8-hydroxyquinoline) were optimized using a Box-Behnken design. The optimal conditions were established as pH 3.8, 90 μL of carbon tetrachloride, 480 μL of methanol, and 1.09 mmol L⁻¹ of 8-hydroxyquinoline. Besides, the use of external gas module control (EGCM) was explored to minimize the matrix effects caused by the organic solvent introduction. The accuracy of the proposed method was estimated employing a certificate reference material (bovine liver, NIST 1577c) and the obtained recovery was 92%. The limit of detection was found to be 0.20 μg g⁻¹, and the enrichment factor was 4.5. The DLLME-MIP OES was applied for six samples of lamb meat, and the results compared to ICP-MS presented no statistical difference. Therefore, the proposed method showed satisfactory accuracy and suitable sensitivity.
Graphical abstract
An ultrasound-assisted magnetic solid phase microextraction procedure was developed for separation and enrichment of trace levels of patent blue V in different syrups, waters and artificial sweat samples prior to its determination by UV– Vis spectrophotometry. Three mg magnetic multiwalled carbon nanotube (mMWCNT) was used as solid phase. Several variables affecting microextraction efficiency such as sample volume, pH, matrix effect, volume and type of eluent, sample volume were investigated and optimized. The developed SPME method presents a limit of detection (LOD, N=10) of 3,5 μgL⁻¹, analyte recoveries were 98-100%, preconcentration factor of 250 and a relative standard deviation (RSD, %, N=10) of 1,5 % under the optimum conditions. The proposed procedure for determination of patent blue V in different environments samples is precise, accurate, very simple, practical, fast, easy to apply and economical.
The present review deals with microwave-induced plasma optical emission spectrometry (MIP OES) with focus on MIP sustained by nitrogen. Advances of MIP OES as an analytical tool and nitrogen-MIP OES application in elemental analysis are highlighted. The novel microwave inductively coupled atmospheric-pressure plasma (MICAP) is also presented and the nitrogen-MICAP discussed. The assertion of MIP OES as an atomic spectrometry technique for elemental analysis occurred mainly due to development of nitrogen-MIP generated in a cavity embedded in a narrow width waveguide. The precise location of the cavity as a function of the wavelength associated with the 2450 MHz frequency maximizes the magnetic field and generates almost entirely H-type excitation, similar to that occurring in argon inductively coupled plasma (Ar-ICP). Microwave induced plasma optical emission spectrometry based on the use of nitrogen-MIP is in general more sensitive, in terms of detection limits, than flame atomic absorption spectrometry (FAAS) and almost comparable to inductively coupled plasma optical emission spectrometry (ICP OES). Since the introduction of a commercial nitrogen-MIP OES instrument in the last decade, which allows metals and non-metal determination, applications of the technique for analysis of samples with different matrices have increased as demonstrated in the present review.
Coprecipitation with magnesium hydroxide was investigated as a pretreatment method for the determination of rare earth elements (REEs) in seawater samples, both for separation of the salt contents and for the enrichment of REEs. The precipitate of magnesium hydroxide was collected on a syringe filter and then subjected to the on-line measurement of REEs by an inductively coupled plasma tandem quadrupole mass spectrometer (ICP-MS/MS). Coprecipitation resulted in a separating rate of over 99% for salt contents, while the on-line measurement of REEs in the magnesium hydroxide provided an enhancement factor of 130-fold for the transient peak height of signal intensities. Mass-shift mode was applied to the measurement of REEs by ICP-MS/MS, where each isotope of the REEs was permitted to pass the first QMS and to react with oxygen gas in the reaction cell so as to form a monoxide ion, which was permitted to pass the second QMS and then measured by the detector. Mass-shift to monoxide ion effectively removed the spectral interferences in the measurement of REEs and permitted the correct determination of REEs in seawater samples. Detection limits were calculated based on the results of 10-set of the replicated blank test, which were low enough for the determination of REEs in natural seawater samples. The effectiveness of the present method was confirmed by the analysis of three certified reference materials of seawater, i.e. CASS-4, CASS-5, and NASS-6.
A new procedure for the determination of As, Cd, Cr, Cu, Hg, Pb, and Zn in fish and meat (bovine and ovine) samples by microwave-induced plasma optical emission spectrometry (MIP OES) was developed. The procedure is based on separation and preconcentration of analytes by solid-phase extraction (SPE), composed from the functionalization of silica with p-aminobenzoic acid (PABA-MCM-41). Factors that directly affect the SPE procedure as pH, buffer concentration, sample flow, and elution flow were evaluated through a factorial design (24). The optimized conditions employed at the proposed procedure were as follows: pH 9.5, 0.01 mol L−1 borate buffer concentration, sampling, and 6.0 mL min−1 of elution flow. Linear models were treated regarding the weighted regression, an optional strategy of the equipment, the weighted fit. The proposed procedure provides limits of quantification (LOQ) of 9.6, 2.8, 0.1, 0.2, 1.5, 13.3, and 3.9 μg g−1 for As, Cd, Cr, Cu, Hg, Pb, and Zn, respectively. Accuracy was assessed from the analysis of the certified reference materials (CRM) of dogfish liver (DOLT-5, NRC) and bovine liver (1577c, NIST), and a reference material of bovine liver (RM-Agro E3001a, EMBRAPA). The procedure was applied in local market meats (bovine and ovine) and fish (tilapia) samples, and it showed adequate for the determination of As, Cd, Cr, Cu, Hg, Pb, and Zn by MIP OES.
Platinum Group Metals (PGM) are modern, technologically relevant elements for which (i) the anthropogenic cycle has outcompeted the natural cycles and (ii) environmental behavior, fate and impact are still widely unknown. Stripping voltammetry was used for accurate determinations of platinum (Pt) in historical records of river sediments and estuarine oysters from the Gironde fluvial-estuarine continuum (SW France) comprising the Lot River. Sediment cores from the Lot River, dated from 1952 to 2001, showed past Pt contamination due to former industrial (smelter) activities in the Lot River watershed. These samples revealed the phasing-out of a historical Pt contamination with Pt/Th (Thorium) values of 11 × 10− 5 ± 0.79 × 10− 5 for the deepest part of the core which is clearly greater than the regional geochemical background value (Pt/Th ~ 2.2 × 10− 5 ± 0.68 × 10− 5). Wild oyster samples from the mouth of the Gironde Estuary collected from 1981 to 2013 showed Pt concentrations ranging from 0.80 ± 0.01 pmol.g− 1 to 3.10 ± 0.14 pmol.g− 1. Oyster samples have recorded the phasing-out of the smelter-related historical industrial Pt contamination and empirical modelling suggests the recent rise of a new source of Pt to the system. Temporal variations of Pt in oysters attributed to this recent source reflect the exponential increase of Pt demand for car catalytic converters, pointing towards the increasing importance of this emerging source to the aquatic system. Estuarine oysters prove to be suitable bioindicators for Pt contamination providing sensitive monitoring of emission variations over time. Furthermore, oysters may bioconcentrate Pt (Bioconcentration Factor, BCF ~ 103) and transfer this metal contamination to the higher food chain. These findings highlight the need for a deeper understanding of environmental Pt contamination, processes and possible adverse effects to biota.
A new, simple and rapid coprecipitation method has been developed to separate and preconcentrate traces of Co(II), Cu(II), Fe(III), Pb(II) and Mn(II) in different samples prior to their determinations by flame atomic absorption spectrometry (FAAS). 2-[(E)-(8-hydroxy-2-methylquinolin-5-yl) diazenyl] benzoic acid (QAN) was firstly synthesized and characterized as a new chelating reagent for determination of some metals. IR spectra, 1H-NMR spectrum and elemental analysis were evaluated for the characterization of the reagent. These metals were quantitatively recovered with Ni(II)/QAN precipitate in pH range of 8–10. Different factors such as sample volume, amount of QAN, and Ni(II) as carrier element, sample volume, and matrix effects for improving the quality of the preconcentration procedure were optimized. Under optimized experimentally established conditions, analytical detection limits were in the range of 0.03–0.83 μg L−1, while precision (RSD) was <3.5%, and enrichment factor was obtained as 100. The accuracy of the presented coprecipitation method was verified by the analysis of certified reference materials. The method was applied to the determination of the analytes in real samples such as food samples and make up products, and accuracy was found high (recoveries >95%).
The aim of the present work is to broaden our knowledge on the variability of trace
metals in mussel tissues, focusing on seasonal
fluctuations in the three different sampling sites of
Algerian west coast (Oran Harbor (S1), Ain Defla (S2) and Hadjaj (S3)). For this purpose, the
bioavailability (metal indices) and bioaccumulation (metal concentrations in soft tissues) of
heavy metals (Zn, Cu, Pb, and Cd), and the physiological characteristics (e.g. biological indices
such as condition index (CI)) of mussels Mytilus galloprovincialis have been assessed and related
to seasons and sites. In S1, the highest levels of metal concentrations and indices were obtained in
mussels sampled in winter for Zn, Cu and Cd, but in summer for Pb. The biological indices
significantly decreased in winter. In S2, the levels of concentrations and indices of all metals
varied whatever the seasons, excepting in summer where the values were the lowest. In summer and spring, the biological indices were lower than in autumn and winter. The low growth of
organisms in spring and summer might be correlated to the reproductive period and the low
trophic level known in S2. S3, considered as a “pristine” area, showed low metal concentrations
and indices, and high biological indices, reflecting the favorable physiological conditions for the
mussel growth. This approach might be used in the monitoring of the quality of coastal waters and
the present work provided a useful data set for Mediterranean monitoring network.
Although fish intake has potential health benefits, the presence of metal contamination in seafood has raised public health concerns. In this study, levels of mercury, cadmium, lead, tin and arsenic have been determined in fresh, canned and frozen fish and shellfish products and compared with the maximum levels currently in force. In a further step, potential human health risks for the consumers were assessed. A total of 485 samples of the 43 most frequently consumed fish and shellfish species in Andalusia (Southern Spain) were analyzed for their toxic elements content. High mercury concentrations were found in some predatory species (blue shark, cat shark, swordfish and tuna), although they were below the regulatory maximum levels. In the case of cadmium, bivalve mollusks such as canned clams and mussels presented higher concentrations than fish, but almost none of the samples analyzed exceeded the maximum levels. Lead concentrations were almost negligible with the exception of frozen common sole, which showed median levels above the legal limit. Tin levels in canned products were far below the maximum regulatory limit, indicating that no significant tin was transferred from the can. Arsenic concentrations were higher in crustaceans such as fresh and frozen shrimps. The risk assessment performed indicated that fish and shellfish products were safe for the average consumer, although a potential risk cannot be dismissed for regular or excessive consumers of particular fish species, such as tuna, swordfish, blue shark and cat shark (for mercury) and common sole (for lead).
Multivitamin/mineral (MVM) supplements possess highly saline matrix which, unless eliminated, precludes accurate determination of trace amounts of toxic metal impurities by inductively coupled plasma mass spectrometry (ICP-MS). Multi-step separations (up to four-steps) are described in literature; often for single element determinations due to the difficulties in removing the matrix components. In this study, we developed a three-step sequential coprecipitation procedure for simultaneous separation of As and Cd impurities from MVM supplements for determination by ICP-MS. The procedure provided effective elimination of salt matrix, including Ca, Mg and KCl along with the interfering molybdenum (Mo) and tin (Sn) from MVM solutions. KCl, Mo and Sn were reduced by two-step Mg(OH)2 coprecipitation to about 34 μg mL⁻¹ K (ca. 31 μg mL⁻¹ Cl) and 0.4 μg mL⁻¹ Mo. Levels of Sn and Na were not significant. A third coprecipitation of the resulting MVM solution with HF + NH4OH mixture precipitated virtually all Ca and Mg to as low as 1 and 10 μg mL⁻¹, respectively. The recoveries for As and Cd in the spiked MVM solutions were about 96% and 95%, respectively. The accuracy of the method was validated with analysis of multivitamin/multielement tablets certified reference material (SRM 3280). Experimental values were 112 ± 37 ng g⁻¹ for ⁷⁵As, and 76 ± 5, 79 ± 5, and 78 ± 7 ng g⁻¹ for ¹¹⁰Cd, ¹¹¹Cd and ¹¹⁴Cd isotopes, respectively, that were not significantly different from the certified values of As (132 ± 44 ng g⁻¹) and Cd (80.2 ± 0.9 ng g⁻¹) at 95% confidence level. Several commercially available MVM supplements were analyzed with the procedure. Mean As levels measured in the tablets varied between 24 and 128 ng g⁻¹ and that for Cd were between 28 and 125 ng g⁻¹ indicating total amount of As or Cd ingested per serving size were below the safe daily exposure limits. In addition, the results obtained for As and Cd with the procedure were lower in comparison to the values reported in literature indicating that ICP-MS analysis of complex MVM supplements could be prone to higher risks of inaccuracy without removal of interfering matrix.
Chaohu Lake is one of the five largest freshwater lakes in China situated in Anhui Province. Water, sediment and aquatic organisms were collected from Chaohu Lake. Trace metals were measured to investigate their bioaccumulation pattern and trophic transfer in the food web as well as potential health risk assessment through fish consumption. Trophic interactions were investigated by stable nitrogen isotope. Linear regression of log metal concentration versus δ¹⁵N was used to determine whether there is biomagnification or biodilution. Results showed that concentrations of trace metals in water were rather low except Hg, some of which surpassed the scope of quality standard. Trace metals in sediment exceeded background values nevertheless within the range for the protection of aquatic life. Therein, geochemical fractionation showed that Cd would pose a considerable potential ecological risk. Trace metals were higher in plankton except for Cu and Zn was higher in shrimp due to metabolic needs. Decreasing trend was observed in Pb, Cr, Cd, As and Hg levels with increasing trophic level whereas increasing trend was observed in Zn. Trace metals in fish were lower than legislation thresholds except for Cr in two samples that exceeded the threshold value. Nonetheless, total target hazard quotient values and target cancer risk were lower than unit and within acceptable range, indicating there was no health risk for inhabitants from trace metals through fish consumption.
In this paper, we report an improved magnesium hydroxide, Mg(OH)2, coprecipitation method for the determination of 16 trace elements (Al, V, Cr, Mn, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Sb, Sn and Pb) and 18 rare earth elements (REEs), including Sc, Y, U and Th in seawater and estuarine water samples. The procedure involves coprecipitation of the trace elements and REEs on Mg(OH)2 upon addition of a small volume of triethylamine (TEA) followed by analysis of the dissolved pellet solutions by inductively coupled plasma mass spectrometry (ICP-MS). Three-step sequential coprecipitation was carried out on 10 mL aliquots of seawater to eliminate the matrix ions and to preconcentrate the analytes of interest into a 1 mL final volume. Spike recoveries varied from 85% (Th) to 105% (Y). Calcium (Ca), sodium (Na) and potassium (K) matrices were virtually eliminated from the analysis solutions. Collision reaction interface (CRI) technology utilizing H2 and He gases was employed to determine its effectiveness in removing the spectral interferences originating from the residual Mg matrix, TEA and plasma gases. H2 was more effective than He in reducing spectral interferences from TEA and plasma gases. Limits of detection (LODs) ranged from 0.01 ng L-1 (Ho) to 72 ng L-1 (Al). The method was validated by using certified seawater (CASS-4) and estuarine water (SLEW-3) reference materials. Precision for five (n = 5) replicate measurements were between 1.2% (Pr) and 18% (Lu). Fe, Pb, Sn, and Zn impurities in TEA were significant in comparison to the levels in CASS-4 and SLEW-3, while relatively high background signals impacted determinations of low levels of Sc and Th. The effects of these hurdles on precision and accuracy were alleviated by measuring these elements in spiked CASS-4 and SLEW-3.
Background:
The persistent sample circulation microextraction (PSCME) joined with the graphite furnace atomic absorption spectrometry (GFAAS) was developed as a high preconcentration technique for the determination of heavy metals in fish species. In this method, a few microliter of organic solvent (40.0 µl carbon tetrachloride) was transferred to the bottom of a conical sample cup. Then a 10.0 ml of aqueous solution transformed to fine droplets while passing through an organic solvent. At this stage, metal-ligand hydrophobic complex was extracted into the organic solvent. After extraction, 20 µl of extraction solvent was injected into the graphite tube using an auto-sampler.
Results:
Under the optimum conditions, enrichment factors and enhancement factor were in the range of 180-240 and 155-214, respectively. The calibration curves were linear in the range of 0.03-200 µg kg(-1) and the limits of detections (LODs) were in the range of 0.01-0.05 µg kg(-1) . The Repeatability (intra-day) and reproducibility (inter-day) for 0.50 µg l(-1) of Hg and 0.10 µg l(-1) of Cd and Pb were in the range of 3.1-4.2% (n = 7) and 4.3-6.1% (n = 7), respectively.
Conclusion:
A potential human health risk assessment was conducted by calculating estimated weekly intake (EWI) of the metals from eating fish and comparison of these values with provisional tolerable weekly intake (PTWI) values. EWI data for the studied metals through fish consumption were lower than the PTWI values.
This study was conducted to determine and compare the concentrations of mercury (Hg), cadmium (Cd), arsenic (As), lead (Pb), nickel (Ni), iron (Fe), zinc (Zn), copper (Cu), manganese (Mn), cobalt (Co), and selenium (Se) in the muscle of wild and farmed carp (Cyprinus carpio) and wild and farmed Caspian kutum (Rutilus frisii kutum) collected from south-western Caspian Sea areas of Iran between December 2014 and March 2015. In addition, risk assessment of consumers to exposure to metals through fish consumption was estimated. In all the samples, the arsenic concentration was lower than the detection limit. The Pb, Cd, Hg and Mn concentrations were significantly higher in the wild fish samples compared to the farmed fish samples. There was no significant difference in the Fe, Zn, Cu, Co, Ni and Se concentrations of the wild and farmed carp and the wild and farmed Caspian kutum. Iron displayed the highest concentration of all the analysed metals in both the wild and farmed fish, followed by Zn and Cu. The highest Hg, Cd, Pb, Ni, Fe, Zn, Cu, Mn, Co and Se concentrations were 0.056, 0.011, 0.065, 0.120, 4.151, 3.792, 2.948, 2.690, 0.037 and 0.162 μg g⁻¹, respectively. The estimated daily intake of all metals was acceptable, and the hazard quotient values showed that consumption of the analysed fish posed no health risk to consumers.
In this work, we use the Boltzmann plot, Saha's equation and the Mg II/Mg I signal ratio to determine temperature (T), electron number density (ne) and robustness of different regions of a microwave-induced nitrogen plasma. A 2-D profile based on plasma observation position and nebulization flow rate is generated for each of these properties and their effects on sensitivity, accuracy and matrix-related interferences in microwave-induced plasma optical emission spectrometry (MIP OES) are evaluated. Plasma temperatures vary between 4220 and 5360 K by changing nebulization flow rate and plasma observation position. These same instrumental parameters are varied to produce ne values in the 0.47-3.72 × 1013 cm-3 range, and Mg II/Mg I ratios between 0.26 and 2.01. Limits of detection (LODs) were calculated for different T and ne conditions, and for analytes with a wide range of Esum values (Esum = ionization energy + excitation energy). The best LODs were calculated for determinations at high ne plasma regions. More robust plasma conditions allowed for more accurate results when determining analytes with Esum > 9 eV or < 3 eV. For intermediate Esum elements, the best recoveries in complex sample analyses were obtained at high ne conditions. Although the microwave applied power is fixed at 1000 W for the commercial MIP OES evaluated, one can still control plasma conditions by varying other operating parameters, which may contribute to fewer matrix effects, better accuracies and lower LODs.
A preconcentration/separation system for cadmium(II), nickel(II), copper(II), lead(II), iron(II), cobalt(II), and manganese(II) ions has been established prior to their atomic absorption spectrometric determinations. The procedure is based on the co-precipitation of these ions by the aid of a praseodymium hydroxide (Pr(OH)3) precipitate. The precipitate was dissolved in 0.5 mL of concentrated HNO3, and made up to 10.0 mL with water. The analytes were determined by a flame atomic absorption spectrometer. The effects of analytical parameters including pH, amounts of praseodymium as carrier element, sample volume, etc. on the recoveries of heavy metals were investigated. The effects of matrix ions were also examined. The limits of detection for analyte ions were found in the range between 0.7–5.2 μg/L. The validation of this present procedure was verified by the analysis of certified reference materials, TMDA-54.4 (fortified water) and NIST 1570a (spinach leaves). The proposed co-precipitation procedure was applied for the determination of cadmium(II), nickel(II), copper(II), lead(II), iron(II), cobalt(II), and manganese(II) ions in various environmental water samples.
A new preconcentration method, magnetic dispersive micro solid phase extraction (MDMSPE) developed for separation and determination of mercury. In this technique, an appropriate mixture of extraction solvent, disperser solvent and nanomagnetite (Fe3O4)/chelating agent 1-(2-ethoxyphenyl)-3-(4-ethoxyphenyl) triazene functionalized multi-walled carbon nanotubes with silica shell, as an adsorbent injected rapidly into an aqueous solution containing mercury. After the proper contact time, the nano-adsorbent separated from the aqueous phase by applying magnetic field outside of the vial and transferred to another vial with the elution solvent. The residual solution determined by cold vapour atomic absorption spectroscopy. The main factors affected the preconcentration of mercury investigated and optimized, such as extraction and disperser solvent type, adsorbed amount, sample pH value, effluent concentration, extraction time, the volume of chelating agents and temperature. The adsorption equilibrium data obeyed the Langmuir isotherm models and the kinetic data were well suited to the pseudo-second-order model. Thermodynamic studies revealed the endothermic nature of the procedure. Under the optimum experimental conditions, the detection limit for Hg(II) found to be 1.5 ± 0.27 ng mL− 1 and its limit of quantification (LOQ) was 5.0 ± 0.32 ng mL− 1 (n = 5). The linear range of the calibration curve was 9 ± 0.51–1000 ± 0.03 ng mL− 1with a correlation coefficient of 0.9994.
A new simple and sensitive preconcentration, separation and environmentally friendly method based on carrier element free coprecipitation (CEFC) was developed using 4-(2-hydroxybenzylideneamino)-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one (APSAL) as a new organic co-precipitant to precipitate Cr3+, Cu2+, Fe3+, Pb2+ and Zn2+ ions from water and food samples. The levels of the studied elements were detected by flame atomic absorption spectrometry (FAAS). The impact of several analytical parameters, such as pH, sample volume and coprecipitant amount as well as centrifugation rate and time was investigated to recover the examined metal ions. The influence of matrix ions was also tested, and no interferences were observed. The recovery values of the analyte ions were calculated and found to be in the range of 95-101%. The detection limits, corresponding to three times the standard deviation of the blank (N=10), were found to be in the range of 0.2-1.2 μg L-1. The relative standard deviation (RSD) was calculated to evaluate the precision of the proposed method and was found to be 5.0%. The calculated preconcentration factor was 100. The proposed method was successfully applied to separate and preconcentrate trace amounts of ions in several water and food samples. To confirm the accuracy and validate the proposed method, certified reference materials were analyzed with satisfactory results.
In this work, the application of dispersive liquid-liquid microextraction (DLLME) for the extraction and preconcentration of Cd and Pb in honey and subsequent determination by flame atomic absorption spectrometry (FAAS) is proposed. Parameters such as type and volume of dispersive solvent (300μL of acetonitrile for Cd and 900μL of acetone for Pb), type and volume of extraction solvent (140μL of carbon tetrachloride), concentration of complexing agent (sodium diethyldithiocarbamate, 0.25gL-1 for Cd and 0.50gL-1 for Pb), pH (7.0), temperature (35°C), washing cycles of extract (2 times), centrifugation speed (840g for Cd and 4600g for Pb) and sample mass (500mg) were evaluated. The limits of detection (LODs) were 20 and 140ngg-1 for Cd and Pb, respectively. These limits are lower than those established by the Brazilian Ministry of Agriculture, Livestock and Supply (500ngg-1 for both elements) for honey and for food in European Community. Samples were also digested in a microwave-assisted digestion system followed by element determination by inductively coupled plasma mass spectrometry (ICP-MS). Therefore, the proposed method is promising for routine analysis and quality control of Cd and Pb in honey.
A method of isotope dilution coupled with inductively coupled plasma mass spectrometry (ID-ICP-MS) after Mg(OH)2 coprecipitation was employed to determine trace lead (Pb) in fish sauces. The pH values and the amounts of Mg2+ in the coprecipitation system and the amounts of isotopically enriched 206Pb reagent added in the measurement were optimized. Results showed that a recovery by adding standard was 92.0% with a relative standard deviation (RSD) of 0.39%. The detection limit estimated with the calculated method used in the study was 7.65 ng g−1. Through the Mg(OH)2 coprecipitation, more than 80% of matrix ions such as K+, Na+, and Ca2+ in the samples were effectively removed, and the trace Pb in fish sauces was largely enriched. The concentrations of Pb measured in 12 fish sauces ranged from 0.068 to 0.299 μg g−1, which was completely within the Pb limit (0.50 μg g−1), a hygienic standard for aquatic flavorings set in China (GB 10133-2005). It has been well demonstrated that the method of ID-ICP-MS coupled with Mg(OH)2 coprecipitation is suitable for determining trace Pb in fish sauces containing high levels of salt matrices.
In this study, Cu(II), Pb(II), Zn(II), Fe(III) and Cr(III) were determined in some food and water samples after development 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) coprecipitation procedure using flame atomic absorption spectrometry (FAAS). Effects of some analytical parameter including pH, sample volume, reagent amount, centrifuge rate and time, etc. on the presented coprecipitation system were studied for the quantitative recoveries of Cu(II), Pb(II), Zn(II), Fe(III) and Cr(III) ions. The influences of matrix ions were examined. The recovery values for analyte ions were calculated ⩾95%. The relative standard deviation was found 8.0% and the preconcentration factor was found as 25 for all analyte ions. The detection limits (k = 3, N = 21) were found to be as 0.80 μg L−1 Cu(II), 3.08 μg L−1 Pb(II), 0.28 μg L−1 Zn(II), 0.91 μg L−1 Fe(III) and 1.82 μg L−1 Cr(III). NIST SRM 1515 Apple leaves and GBW-07605 Tea certified reference materials were used to confirm the accuracy of the method. The simultaneous coprecipitation method was applied to various water and microwave digested food samples.
A coprecipitation method was developed for the quantitative separation and preconcentration of Pb(II), Cr(III) and Cu(II) ions. Analytes were coprecipitated using a triazole derivative (2-{4-[2-(1H-indol-3-yl)ethyl]-3-(4-chlorobenzyl)-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl}-N-aryl methylidene acetohydrazid). The analytes were analyzed by flame atomic absorption spectrometry. The parameters such as sample pH, amount of reagent, sample volume, matrix effects etc. were investigated. The enrichment factor for the analyzed metal ions was obtained as 50. The relative standard deviations (RSD) were in the range of 2.8-4.1%. The accuracy of the proposed procedure was checked by the analysis of the CRM-CSandy Soil C. The method was successfully applied to real samples.
This paper reviews the most common methods of generation of plasmas using microwaves with special emphasis on recently developed microwave plasma (MWP) sources for analytical applications. The art and science of microwave plasma optical and mass spectroscopy instrumentation (MWP-OES/MS) and application is briefly presented including very recent advances in the field as of 2012. The design and operation of MWPs is discussed to provide a basic understanding of the most important selection criteria when designing MWP systems. The various plasma generation systems described include single-electrode capacitive microwave plasmas, electrodeless inductively coupled plasmas, multi-electrode systems energized with stationary or rotating fields. We also discuss various technical realizations of MWP sources for selected applications. Examples of technical realizations of plasmas in closed structures (cavities), in open structures (surfatrons, planar plasma sources), and in magnetic fields (Hammer cavity) are discussed in detail. Finally, we mention micro- and mini- discharges as convenient sources for miniaturized spectrometric systems. Specific topics include fundamental aspects of MWP i.e., recent advances in the construction of analytical MWPs (coaxially coupled cavities, strip-line technology, multi-point energizing, power combining, rotating field-excited plasmas), operational characteristics, analytical characteristics and applications. Special reference is made to coupling with OES for determination of chromatographic effluents and particle sizing. The developments in elemental and molecular MS applications in both low-power and high-power MWPs are discussed.
Concentrations of eight trace elements [iron (Fe), manganese (Mn), zinc (Zn), chromium (Cr), mercury (Hg), cadmium (Cd), lead (Pb), and arsenic (As)] were measured in a total of 198 samples covering 24 fish species collected from Taihu Lake, China, in September 2009. The trace elements were detected in all samples, and the total mean concentrations ranged from 18.2 to 215.8μg/gdw (dry weight). The concentrations of the trace elements followed the sequence of Zn>Fe>Mn>Cr>As>Hg>Pb>Cd. The measured trace element concentrations in fish from Taihu Lake were similar to or lower than the reported values in fish around the world. The metal pollution index was used to compare the total trace element accumulation levels among various species. Toxabramis swinhonis (1.606) accumulated the highest level of the total trace elements, and Saurogobio dabryi (0.315) contained the lowest. The concentrations of human non-essential trace elements (Hg, Cd, Pb, and As) were lower than the allowable maximum levels in fish in China and the European Union. The relationships between the trace element concentrations and the δ(15)N values of fish species were used to investigate the trophic transfer potential of the trace elements. Of the trace elements, Hg might be biomagnified through the food chain in Taihu Lake if the significant level of p-value was set at 0.1. No biomagnification and biodilution were observed for other trace elements.
Coprecipitation is one of the classical, but quite useful, techniques for separation/preconcentration for trace element analysis. Many elements can be easily collected with a carrier precipitate, and the handling is simpler and easier compared to that of other techniques such as solvent extraction and solid-phase extraction. In addition, selective separation can also be designed by controlling of chemical and physical conditions in the procedure. In this section, mechanisms of coprecipitation, selection of a carrier precipitates, selectivity in coprecipitation, and typical examples of coprecipitation in trace element analysis are described.
A new, simple, and rapid separation and preconcentration procedure, for determination of Pb(II), Cd(II), Zn(II), and Co(II) ions in environmental real samples, has been developed. The method is based on the combination of coprecipitation of analyte ions by the aid of the Mo(VI)-diethyldithiocarbamate-(Mo(VI)-DDTC) precipitate and flame atomic absorption spectrometric determinations. The effects of experimental conditions like pH of the aqueous solution, amounts of DDTC and Mo(VI), standing time, centrifugation rate and time, sample volume, etc. and also the influences of some foreign ions were investigated in detail on the quantitative recoveries of the analyte ions. The preconcentration factors were found to be 150 for Pb(II), Zn(II) and Co(II), and 200 for Cd(II) ions. The detection limits were in the range of 0.1-2.2 μg L(-1) while the relative standard deviations were found to be lower than 5 % for the studied analyte ions. The accuracy of the method was checked by spiked/recovery tests and the analysis of certified reference material (CRM TMDW-500 Drinking Water). The procedure was successfully applied to seawater and stream water as liquid samples and baby food and dried eggplant as solid samples in order to determine the levels of Pb(II), Cd(II), Zn(II), and Co(II) ions.
This paper describes a simple method for simultaneous preconcentration and matrix reduction during the analysis of rare earth elements (REEs) in water samples through laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). From a systematic investigation of the co-precipitation of REEs using magnesium hydroxide, we optimized the effects of several parameters - the pH, the amount of magnesium, the shaking time, the efficiency of Ba removal, and the sample matrix - to ensure quantitative recoveries. We employed repetitive laser ablation to remove the dried-droplet samples from the filter medium and introduce them into the ICP-MS system for determinations of REEs. The enrichment factors ranged from 8 to 88. The detection limit, at an enrichment factor of 32, ranged from 0.03 to 0.20 pg mL(-1). The relative standard deviations for the determination of REEs at a concentration of 1 ng mL(-1) when processing 40 mL sample solution were 2.0-4.8%. We applied this method to the satisfactory determination of REEs in lake water and synthetic seawater samples.
A novel preconcentration procedure based coprecipitation of Cu(II), Co(II), Cd(II), Ni(II), Mn(II), Fe(III) and Pb(II) on thulium hydroxide precipitate has been presented prior to flame atomic absorption spectrometric determination of them in environmental samples. The analytical parameters that influenced the quantitative coprecipitation of analytes including amount of thulium, pH, duration time, etc. were investigated. The effects of alkali, earth alkali, and some transition metals on the recoveries were also studied. Under the optimized conditions, the detection limits (3 sigma, N=10) for the analytes were in the range of 0.1-1.6 μg/L, respectively. The validation of the presented coprecipitation method was checked by the analysis of certified reference materials (TMDA 54.4 fortified lake water and HR-1 Humber river sediment). The proposed coprecipitation method has been successfully applied for the determination of traces of copper, cobalt, cadmium, nickel, manganese, iron and lead in food and environmental samples.
A procedure for simultaneous separation/preconcentration of copper, zinc, cadmium, and nickel in water samples, based on cloud point extraction (CPE) as a prior step to their determination by inductively coupled plasma optic emission spectrometry (ICP-OES), has been developed. The analytes reacted with 4-(2-pyridylazo)-resorcinol (PAR) at pH 5 to form hydrophobic chelates, which were separated and preconcentrated in a surfactant-rich phase of octylphenoxypolyethoxyethanol (Triton X-114). The parameters affecting the extraction efficiency of the proposed method, such as sample pH, complexing agent concentration, buffer amount, surfactant concentration, temperature, kinetics of complexation reaction, and incubation time were optimized and their respective values were 5, 0.6 mmol L(-1), 0.3 mL, 0.15% (w/v), 50 degrees C, 40 min, and 10 min for 15 mL of preconcentrated solution. The method presented precision (R.S.D.) between 1.3% and 2.6% (n=9). The concentration factors with and without dilution of the surfactant-rich phase for the analytes ranged from 9.4 to 10.1 and from 94.0 to 100.1, respectively. The limits of detection (L.O.D.) obtained for copper, zinc, cadmium, and nickel were 1.2, 1.1, 1.0, and 6.3 microg L(-1), respectively. The accuracy of the procedure was evaluated through recovery experiments on aqueous samples.
A simple and new coprecipitation procedure is developed for the determination of trace quantities of heavy metals (lead, cobalt, copper, cadmium, iron and nickel) in natural water and food samples. Analyte ions were coprecipitated by using zirconium(IV) hydroxide. The determination of metal levels was performed by flame atomic absorption spectrometry (FAAS). The influences of analytical parameters including pH, amount of zirconium(IV), sample volume, etc. were investigated on the recoveries of analyte ions. The effects of possible matrix ions were also examined. The recoveries of the analyte ions were in the range of 95-100%. Preconcentration factor was calculated as 25. The detection limits for the analyte ions based on 3 sigma (n=21) were in the range of 0.27-2.50 microgL(-1). Relative standard deviation was found to be lower than 8%. The validation of the presented coprecipitation procedure was performed by the analysis certified reference materials (GBW 07605 Tea and LGC 6010 Hard drinking water). The procedure was successfully applied to natural waters and food samples like coffee, fish, tobacco, black and green tea.
A magnesium hydroxide coprecipitation technique for determination of Cd, Co, Cu, Mn, Ni in dialysis concentrate is described. The analytes are concentrated from 10 ml of dialysis concentrate into 1 ml of 1 M HNO(3) and subsequently determined by graphite furnace atomic absorption spectrometry. Coprecipitation parameters and matrix effects are discussed. The precision, based on replicate analysis, is around 5% for the analytes, and recovery is quantitative, based on analysis of spiked samples and solutions including matrix components.
A review about the application of response surface methodology (RSM) in the optimization of analytical methods is presented. The theoretical principles of RSM and steps for its application are described to introduce readers to this multivariate statistical technique. Symmetrical experimental designs (three-level factorial, Box-Behnken, central composite, and Doehlert designs) are compared in terms of characteristics and efficiency. Furthermore, recent references of their uses in analytical chemistry are presented. Multiple response optimization applying desirability functions in RSM and the use of artificial neural networks for modeling are also discussed.
setting maximum levels for certain contaminants in foodstuffs (Text with EEA relevance)
EC, Commission Regulation (EC) N o 1881/2006 of 19 december 2006 setting
maximum levels for certain contaminants in foodstuffs (Text with EEA relevance),
Official Journal of the European Union, Bruxelas, European Union, 2006. http://
data.europa.eu/eli/reg/2006/1881/oj (accessed May 15, 2020).
amending Regulation (EC) N o 1881/2006 setting maximum levels for certain contaminants in foodstuffs (Text with EEA relevance)
EC, Commission regulation (EC) N o 629/2008 of 2 july 2008 amending Regulation
(EC) N o 1881/2006 setting maximum levels for certain contaminants in foodstuffs
(Text with EEA relevance), Official Journal of the European Union, Bruxelas,
European Union, 2008. https://eur-lex.europa.eu/eli/reg/2008/629/oj (accessed
May 15, 2020).