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ABSTRACT: Concurrent solvent recondensation-large volume injection (CSR-LVI) is a gas chromatography injection technique that is particularly suitable for determining volatile compounds. In the present work, we evaluated the applicability of this technique for the analysis of linear and cyclic methylsiloxanes in sewage sludges and soils after solvent extraction to prevent losses of low-molecular-weight compounds. The CSR-LVI injection method was optimised to achieve maximum sensitivity and good chromatographic peak shapes. A liner packed with deactivated glass wool and a 5m×0.32mm I.D. uncoated fused-silica precolumn was used. This made it possible to inject extract volumes of up to 30μl. Good linearity (r>0.9993) and precision (RSD <15%), with recoveries ranging from 80 to 100% and method limits of quantification from 0.03 to 0.4ngg(-1) wet weight (0.04-1.5ngg(-1) dry weight for sewage sludges and 0.01-0.5ngg(-1) dry weight for soils) were obtained. The developed method was applied to the analysis of linear and cyclic methylsiloxanes in sewage sludges collected from several wastewater treatment plants in Catalonia (NE Spain) and urban soils from the city of Barcelona.
Journal of chromatography. A 10/2012; · 4.19 Impact Factor
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ABSTRACT: This paper proposes a new method for the analysis of linear and cyclic methylsiloxanes in water samples based on headspace-solid phase microextraction (HS-SPME) coupled to gas chromatography-mass spectrometry (GC-MS). The extraction efficiency of four commercially available SPME-fibres was evaluated and it was found that a 65 μm polydimethylsiloxane/divinylbenzene (PDMS/DVB) coating was the most suitable for the extraction of siloxanes. The method provided good linearity (r>0.999) and precision (RSD % <17%), and low limits of quantification ranging from 0.01 to 0.74 ng L(-1) for linear siloxanes and between 18 and 34 ng L(-1) for cyclic siloxanes. The HS-SPME-GC-MS method was applied to the analysis of linear and cyclic siloxanes in river waters from Catalonia (NE, Spain) and the results showed concentrations of linear and cyclic siloxanes ranging from 0.09 to 3.94 ng L(-1) and 22.2 to 58.5 ng L(-1), respectively.
Talanta 01/2012; 89:63-9. · 3.79 Impact Factor
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ABSTRACT: This paper describes a fast and simple pressurized liquid extraction (PLE) method combined with gas chromatography coupled to ion trap tandem mass spectrometry (GC-ITMS-MS) for the determination of polybrominated biphenyls (PBBs) in fish samples. The method is based on a simultaneous extraction/clean-up step to reduce analysis time and solvent consumption. The effect of several PLE operating conditions, such as solvent type, extraction temperature and time, number of cycles, and lipid retainer, was optimized to obtain maximum recovery of the analytes with the minimum presence of matrix-interfering compounds. The best conditions were obtained at 100°C with n-hexane using 15 g of silica modified with sulphuric acid (44%, w/w) as sorbent for lipid removal. Quality parameters of the GC-ITMS-MS method were established, achieving good linearity (r>0.998), between 1 and 500 ng ml(-1), and low instrumental limits of detection (0.14-0.76 pg injected). For the whole method, limits of detection ranging from 0.03 to 0.16 ng g(-1) wet weight and good precision (RSD<16%) were obtained.
Talanta 05/2011; 84(4):1155-62. · 3.79 Impact Factor
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ABSTRACT: A one-step extraction and clean-up method using pressurized liquid extraction (PLE) (selective PLE) combined with gas chromatography-ion-trap tandem mass spectrometry (GC-ITMS-MS) was evaluated for the analysis of polybrominated diphenyl ethers (from tri- to hepta-PBDEs) at low concentrations in fish and shellfish samples. To this end, the performance of an on-line PLE extraction/clean-up method and of a classical Soxhlet extraction and clean-up method using a multi-layer modified silica column were compared. The two sample treatment methods provided similar results, although an important reduction in the sample treatment time (40 min per sample) was achieved using the selective PLE method. In addition, the suitability of the PLE combined with GC-ITMS-MS method was evaluated by comparing the results obtained in the analysis of fish samples with those obtained by gas chromatography-high resolution mass spectrometry (GC-HRMS). Good agreement between both techniques was obtained with differences between the mean values of less than 16%. The selective PLE method coupled to GC-ITMS-MS produced accurate results for PBDE determination with low limits of detection (1.0-16.8 pg g(-1) wet weight) and quantification (3.1-51 pg g(-1) wet weight) as well as good precision (RSD<16%). This method has been applied to the analysis of PBDEs in fish and shellfish samples collected at fish markets in Catalonia (NE Spain).
Analytica chimica acta 09/2010; 678(1):73-81. · 4.31 Impact Factor
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ABSTRACT: Gas chromatography coupled to ion trap tandem mass spectrometry (GC-ITMS-MS) is proposed for the analysis of methoxylated polybrominated diphenyl ethers (MeO-PBDEs) in fish and shellfish. MS-MS operating parameters related to the isolation and fragmentation of the precursor ions were optimized to achieve maximum sensitivity and selectivity. This new method allows the determination of both MeO-PBDEs and PBDEs in a single run. Low limits of detection (0.4-2.5 pg injected) and high precision (RSD<13%) were achieved. A sample treatment based on a selective pressurized liquid extraction (PLE) using Florisil as fat retainer was applied for the analysis of these compounds in fish samples. Method limits of quantification ranged from 0.11 to 0.95 ng g(-1) lipid weight for MeO-PBDEs and between 0.18 and 0.50 ng g(-1) lipid weight for PBDEs. In addition, good repeatability of the whole method was achieved (RSD<15%). The suitability of the method was evaluated by analyzing a certified reference material (SRM 1945, whale blubber) with satisfactory results. The developed method was applied to the simultaneous analysis of MeO-PBDEs and PBDEs in fish and shellfish samples from the Mediterranean Sea.
Journal of chromatography. A 08/2010; 1217(32):5253-60. · 4.19 Impact Factor
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ABSTRACT: A fast and simple method for the analysis of polybrominated diphenyl ethers (PBDEs) in fish samples was developed using a one-step extraction and clean-up by means of pressurized liquid extraction (PLE) combined with gas chromatography-ion trap tandem mass spectrometry (GC-ITMS-MS). The selective PLE method provided to obtain ready-to-analyse extracts without any additional clean-up step, using a sorbent as fat retainer inside the PLE cell. Several PLE operating conditions, such as solvent type, extraction temperature and time, number of cycles and type of fat retainer, were studied. Using Florisil as fat retainer, maximum recoveries of PBDEs (83-108%) with minimum presence of matrix-interfering compounds were obtained using a mixture of n-hexane:dichloromethane 90:10 (v/v) as solvent, an extraction temperature of 100 degrees C and a static extraction time of 5 min in combination with three static cycles. Quality parameters of the method were established using standards and fish samples. Limits of detection and quantification ranged from 10 to 34 pg g(-1) wet weight and between 34 and 68 pg g(-1) wet weight, respectively. In addition, good linearity (between 1 and 500 ng ml(-1)) and high precision (RSD %<15%) were achieved. The method was validated using the standard reference material SRM-1945 (whale blubber) and was then applied to the analysis of PBDEs in fish samples.
Talanta 12/2009; 80(2):839-45. · 3.79 Impact Factor
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ABSTRACT: The preparation of a laboratory reference material (LRM) for the determination of naturally occurring heterocyclic amines (HAs) in processed foods is presented in this work. A LRM was prepared from raw chicken breast meat, which was fried under controlled cooking temperature and time. The cooked meat was ground, lyophilised, sieved, homogenised, bottled, and labelled. The HAs DMIP, PhIP, MeIQx, 4,8-DiMeIQx, Norharman and Harman were analysed in the LRM. Homogeneity and stability studies of the bulk LRM were carried out and no statistical differences were observed in the content of the studied HAs in between-bottle and within-bottle comparisons at different storage temperatures (-18, +4, +25 and +40 degrees C) and times (1, 3, 6 and 9 months) by means of HAs determination and analysis of the results. Consequently, the material can be considered homogeneous and stable and can be used in intercomparison exercises for the determination of HAs as well as for quality control purposes in the routine analysis of HAs in foodstuffs. This is the first LRM for the analysis of HAs where these analytes were naturally formed in the material.
Journal of chromatography. B, Analytical technologies in the biomedical and life sciences 06/2009; 877(22):1997-2002. · 2.78 Impact Factor
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ABSTRACT: A simple, fast and fully automated method based on headspace solid-phase microextraction coupled on-line with gas chromatography-ion trap mass spectrometry (HS-SPME-GC-ITMS) is proposed for furan determination in foods. The performance of the proposed method was compared to the automated headspace-GC-MS method, proposed by the US Food and Drugs Administration (US FDA), in terms of repeatability, limits of the detection and quantification. Both methods gave similar results for furan determination in selected food samples, although slightly worse precision (RSD%, 9-12%) and higher limits of detection (from 5 to 20 times higher) were obtained by the headspace method. In addition, higher sample throughput in routine furan analysis was obtained using the proposed HS-SPME-GC-ITMS method with isotope dilution than using the US FDA method, which recommends standard addition for quantification. The proposed method provides good precision (RSD% <10%) and low limits of detection, ranging from 0.02 to 0.12 ng g(-1) depending on the sample. The developed HS-SPME-GC-MS method was used to analyse furan in several Spanish food commodities and concentrations ranging from 0.1 ng g(-1) to 1.1 microg g(-1) were found.
Talanta 06/2009; 78(4-5):1315-20. · 3.79 Impact Factor
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ABSTRACT: Heterocyclic amines (HAs) were analysed in meat extract samples using a new method based on pressurised liquid extraction (PLE) and liquid chromatography-tandem mass spectrometry. This method combines the use of a pressurised fluid with a triple quadrupole MS/MS system, resulting in benefits from both systems: high extraction efficiency and sensitivity. The effects of solvent type and PLE operational parameters, such as temperature and extraction time, were studied to obtain maximum recovery of the analytes with minimum contamination. HA extraction was best achieved using dichloromethane/acetone (50/50, v/v) at 80 degrees C for 10 min. Recoveries ranged from 45% to 79% with good quality parameters: limit of detection values between 0.02 and 1 ng g(-1), linearity (r(2)>0.997), and run-to-run and day-to-day precisions with relative standard deviations lower than 13% achieved at both low (0.20 microg g(-1)) and medium (1.0 microg g(-1)) concentrations. This method reduces sample manipulation and total extraction time by nearly four-fold compared to conventional solid phase extraction. The optimised method was validated using laboratory reference material based on a meat extract, and was successfully applied to HA analysis in several cooked beef samples.
Journal of Chromatography 06/2008; 1194(2):155-60. · 4.53 Impact Factor
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ABSTRACT: Two gas chromatography-mass spectrometry systems equipped with an ion-trap mass analyzer working in tandem mode (GC-MS-MS) were evaluated for the determination of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (PCBs) in food samples. The performance of the two ion-trap instruments, which dispose of an external ion source (ThermoFinnigan GCQ/Polaris) and internal ionization (Varian Saturn 2,200), have been compared in terms of linearity, repeatability, limit of detection and long-term precision. Both instruments provided similar run-to-run and day-to-day precisions, ranging from 2% to 8% and between 2% and 13%, and instrumental limits of detection between 0.09 and 0.36 pg injected for PCDD/Fs and from 0.03 to 0.09 pg injected for dioxin-like PCBs. Although both instruments seem to be suitable for food analysis, only the use of external ionization allowed to achieve reliable results for PCDD/F determination at concentrations close to the maximum residue levels established by the EU for foods. Internal ionization provides high limits of detection (from 10- to 30-fold higher) and worse precision (RSD, 14-43%). In contrast, for dioxin-like PCBs both instruments allowed to obtain excellent results with precisions lower than 15%.
Journal of Chromatography 05/2008; 1186(1-2):302-11. · 4.53 Impact Factor
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ABSTRACT: Polychlorinated naphthalenes (PCNs), short-chain chlorinated paraffins (SCCPs) and polychlorinated biphenyls (PCBs) were analysed in marine sediment samples collected from the coastal area of Barcelona (Spain) and near of a submarine emissary coming from a waste water treatment plant located at the mouth of the Besòs River (Barcelona). An integrated sample treatment based on Soxhlet extraction followed by a simple clean-up with Florisil and graphitized carbon cartridge was employed. Gas chromatography coupled to ion-trap tandem mass spectrometry (GC-MS/MS) and gas chromatography-mass spectrometry in electron capture negative ionization mode, were used for PCN and SCCP determinations, respectively, while for PCB analysis gas chromatography with electron capture detection (GC-ECD) was used. The method developed provided low limits of detection (0.001-0.003 ng g(-1) dry weight (dw) for PCNs, 1.8 ng g(-1) for SCCPs and 0.006-0.014 ng g(-1)dw for PCBs) and good run-to-run precisions (lower than RSD 8%) for the analysis of sediment samples. Concentration levels ranging from 0.17 to 3.27 ng g(-1)dw for PCNs, between 0.21 and 1.17 microg g(-1)dw for SCCPs, and from 2.33 to 44.00 ng g(-1) (dw) for PCBs, were found in the coastal sediments, while for samples collected near to the submarine emissary higher levels (from 2.02 to 6.56 ng g(-1)dw for PCNs, between 1.25 and 2.09 microg g(-1)dw for SCCPs and from 22.34 to 37.74 ng g(-1)dw for PCBs) were obtained. The results obtained provide new data about the occurrence of PCN and SCCP in the coastal area of Barcelona.
Chemosphere 03/2008; 70(9):1552-62. · 3.21 Impact Factor
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Food Chemistry 01/2008; · 3.65 Impact Factor
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ABSTRACT: Gas chromatography coupled to ion trap tandem mass spectrometry (CG-MS-MS) has been evaluated for the analysis of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dl-PCBs) in vegetable oil samples containing different concentration levels (0.2-6 pg WHO-TEQ g(-1) for both PCDD/Fs and dl-PCBs) of the 29 toxic congeners of PCDD/F and dioxin-like PCBs. The effect of potential interfering compounds such as polychlorinated naphthalenes (PCNs), polychlorinated biphenyls (PCBs) and polychlorinated diphenylethers (PCDEs) on the quantification of mono-ortho PCBs has been investigated. In addition, the influence of the clean-up procedure on the final determination by CG-MS-MS was studied, showing that the quality of the results depends to a great extent on this analytical step. Quality parameters have been established and good precisions (CV: 3-19%) and low limits of detection for PCDD/Fs (0.04-0.20 pg g(-1) oil) and dl-PCBs (0.08-0.64 pg g(-1) oil) were obtained. The method was validated by a comparison of the CG-MS-MS results with those obtained by GC-HRMS.
Journal of Chromatography 05/2007; 1149(2):321-32. · 4.53 Impact Factor
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ABSTRACT: A headspace-solid-phase microextraction (HS-SPME) coupled to gas chromatography-ion trap mass spectrometry (GC-IT-MS) method is proposed for the analysis of furan in different heat-treated carbohydrate-rich food samples. The extraction efficiency of six commercially available fibres was evaluated and it was found that a 75mum carboxen/polydimethylsiloxane coating was the most suitable for the extraction of the furan. Parameters affecting the efficiency of HS-SPME procedure such as extraction temperature and time, ionic strength, headspace and aqueous volume ratio (V(h)/V(w)), desorption temperature and time, were optimized. Quality parameters were established using spiked water and food samples. Linearity ranged between 0.02 and 0.5ngg(-1) and run-to-run and day-to-day precisions for food samples were lower than 6% and 10%, respectively. The limit of detection (LOD) of the method is sample dependent and ranged from 8 to 70pgg(-1), while the limit of quantification is from 30 to 250pgg(-1). Isotope dilution using furan-d(4) is proposed for furan determination providing similar results to those obtained by standard addition with internal standard (US Food and Drug Administration method). The developed HS-SPME-GC-IT-MS method was applied to the analysis of furan in different Spanish food samples from a local market, and concentrations ranging from 0.17 to 2279ngg(-1) were found.
Journal of Chromatography 04/2007; 1146(1):103-9. · 4.53 Impact Factor
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ABSTRACT: A new, simple and selective method for the analysis of 5-hydroxymethylfurfural (HMF) in foods by gas chromatography coupled to mass spectrometry (GC-MS) is proposed. Several derivatising procedures based on the formation of an HMF silylated derivative using different reagents were studied. Among the derivatising reagents examined, N,O-bis-trimethylsilyltrifluoroacetamide (BSTFA) provided the best derivatisation yield. Sample clean-up was also optimised, using either liquid-liquid extraction with dichloromethane or solid-phase extraction (SPE) with several commercially available cartridges, and the best results were obtained using ENV+ cartridges. Quality parameters such as day-to-day and run-to-run precision (RSD<10%), linearity (between 25 and 700 ng g(-1)) and detection limit (6 ng g(-1)) were established. This method was successfully applied to the analysis of HMF content in several Spanish food samples from a local market, such as jam, honey, orange juice and bakery products.
Journal of Chromatography 11/2006; 1135(1):85-90. · 4.53 Impact Factor
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ABSTRACT: Polychlorinated n-alkanes (PCAs), also known as chlorinated paraffins (CPs), are highly complex technical mixtures that contain a huge number of structural isomers, theoretically more than 10,000 diastereomers and enantiomers. As a consequence of their persistence, tendency to bioaccumulation, and widespread and unrestricted use, PCAs have been found in aquatic and terrestrial food webs, even in rural and remote areas. Recently, these compounds have been included in regulatory programs of several international organizations, including the US Environmental Protection Agency and the European Union. Consequently, there is a growing demand for reliable methods with which to analyze PCAs in environmental samples. Here, we review current trends and recent developments in the analysis of PCAs in environmental samples such as air, water, sediment, and biota. Practical aspects of sample preparation, chromatographic separation, and detection are covered, with special emphasis placed on analysis of PCAs using gas chromatography-mass spectrometry. The advantages and limitations of these techniques as well as recent improvements in quantification procedures are discussed.
Analytical and Bioanalytical Chemistry 11/2006; 386(4):837-57. · 3.78 Impact Factor
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ABSTRACT: Comprehensive two-dimensional gas chromatography with electron-capture negative ionization time-of-flight mass spectrometry (GC x GC-ECNI-TOF-MS) is used to study the composition and characteristics of short-, medium- and long-chain polychlorinated n-alkane (PCA) mixtures. Distinct ordered structures, which enable the highlighting and interpretation of group and sub-group separations are observed when using a DB-1 x 007-65HT column combination. The analysis of a number of, mutually rather different, technical mixtures and 35 individual standard compounds provides information on the role of chlorine substitution (number of substituents as well as their position), the contribution of carbon versus chlorine atoms to analyte volatility, i.e. GC x GC behaviour, and the influence of the chain length of the carbon skeleton. Two dust samples are analyzed to illustrate the practical usefulness of the proposed procedure.
Journal of Chromatography 10/2005; 1086(1-2):71-82. · 4.53 Impact Factor
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ABSTRACT: Gas chromatography coupled with ion trap tandem mass spectrometry (GC-MS-MS) has been compared to gas chromatography-high-resolution mass spectrometry (GC-HRMS) for the analysis of non-ortho-chlorinated biphenyl (CB) congeners in fish samples. The MS-MS operating parameters related to the isolation and fragmentation of the precursor ions by resonant collision induced dissociation (CID) were optimised in order to achieve maximum sensitivity and selectivity. Analytical procedure consisting of Soxhlet extraction, clean-up using a multilayer silica column and the isolation of the target compounds with SPE commercial carbon cartridges packed with Carbopack B has been applied. Quality parameters have been established using standard solutions and fish samples. Good repeatability, long-term precision (lower than 10%), and limits of detection between 0.12 and 0.16 pg g(-1) were obtained. The effect of potential interfering compounds such as polychlorinated naphthalenes in the quantification of non-ortho-CBs has been investigated. Using selective CID fragmentation conditions, the effect of these compounds was minimised. The GC-MS-MS method was validated by comparing the results with those obtained in two European intercomparison exercises.
Journal of Chromatography 12/2004; 1056(1-2):171-8. · 4.53 Impact Factor
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ABSTRACT: Microwave-assisted extraction (MAE) was evaluated as a possible alternative to Soxhlet extraction for analysing short-chain chlorinated alkanes (commonly called short-chain chlorinated paraffins, SCCPs) in river sediment samples, using gas chromatography coupled to negative chemical ionisation mass spectrometry. For MAE optimisation, several extraction parameters such as solvent extraction mixture, extraction time and extraction temperature were studied. Maximum extraction efficiencies for SCCPs (90%) and for 12 polychlorinated biphenyl (PCB) congeners (91-95%) were achieved using 5 g of sediment sample, 30 ml of n-hexane-acetone (1:1, v/v) as solvent extraction, and 15 min and 115 degrees C of extraction time and temperature, respectively. Activated Florisil was used to clean-up the extracts, allowing highly selective separation of SCCPs from other organic contaminants such as PCBs. MAE was compared with a conventional extraction technique such as Soxhlet and good agreement in the results was obtained. Quality parameters of the optimised MAE method such as run-to-run (R.S.D. 7%) and day-to-day precision (R.S.D. 9%) were determined using spiked river sediment samples, with LODs of 1.5 ng g(-1). This method was successfully applied to the analysis of SCCPs in river sediment samples at concentrations below the ng g(-1) level. O 2004 Elsevier B.V. All rights reserved.
Journal of Chromatography 09/2004; 1046(1-2):19-26. · 4.53 Impact Factor
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ABSTRACT: The present paper describes the preparation of a suitable laboratory reference material (LRM) to validate analytical methods for the determination of heterocyclic amines (HAs) in foods. Three different lots of reference material were prepared using a beef extract which was contaminated with a well-known quantity of amines at different levels ranging from 10 to 75 ng/g. These materials were then lyophilised under determined conditions and, after grinding and sieving, homogenised and, finally, bottled and labelled. Homogeneity and stability studies were performed and no statistical differences were observed in the analysis of variances for within- and between-bottle results, thus demonstrating the homogeneity of the material. Stability at different storage temperatures (-18, +4, +25 and +40 degrees C) and times (1, 2, 3 and 6 months) was also tested. Therefore, the material can be considered homogeneous and stable and can be proposed for use in inter-comparison exercises for the determination of HAs.
Journal of Chromatography B 04/2004; 802(1):61-8. · 2.89 Impact Factor
