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ABSTRACT: A quick, miniaturized and on-line method has been developed for the determination in water of the predominant homologue of benzalkonium chloride, dodecyl dimethyl benzyl ammonium chloride or lauralkonium chloride (C(12)-BAK). The method is based on the formation of an ion-pair in both in-tube solid-phase microextraction (IT-SPME) and capillary liquid chromatography. The IT-SPME optimization required the study of the length and nature of the stationary phase of capillary and the processed sample volume. Because to the surfactant character of the analyte both, the extracting and replacing solvents, have played a decisive role in the IT-SPME optimized procedure. Conditioning the capillary with the mobile phase which contains the counter ion (acetate), using an organic additive (tetrabutylammonium chloride) added to the sample and a mixture water/methanol as replacing solvent (processed just before the valve is switched to the inject position), allowed to obtain good precision of the retention time and a narrow peak for C(12)-BAK. A reversed-phase capillary based TiO(2) column and a mobile phase containing ammonium acetate at pH 5.0 for controlling the interactions of cationic surfactant with titania surface were proposed. The optimized procedure provided adequate linearity, accuracy and precision at the concentrations interval of 1.5-300 μg L(-1) .The limit of detection (LOD) was 0.5 μg L(-1) using diode array detection (DAD). The applicability of proposed IT-SPME-capillary LC method has been assessed in several water samples.
Journal of chromatography. A 06/2012; 1248:55-9. · 4.19 Impact Factor
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ABSTRACT: Haloacetic acids (HAAs) are organic pollutants originated from the drinking water disinfection process, which ought to be controlled and minimized. In this work a method for monitoring haloacetic acids (HAAs) in water samples is proposed, which can be used in quality control laboratories using the techniques most frequently available. Among its main advantages we may highlight its automated character, including minimal steps of sample preparation, and above all, its improved selectivity and sensitivity in the analysis of real samples. Five haloacetic acids (HAA5) were analyzed using solid-phase extraction (SPE) combined with ion-pair liquid chromatography and tandem mass spectrometry. For the optimization of the chromatographic separation, two amines (triethylamine, TEA and dibutylamine, DBA) as ion pair reagents were compared, and a better selectivity and sensitivity was obtained using DBA, especially for monohaloacetic acids. SPE conditions were optimized using different polymeric adsorbents. The electrospray source parameters were studied for maximum precursor ion accumulation, while the collision cell energy of the triple quadrupole mass spectrometer was adjusted for optimum fragmentation. Precursor ions detected were deprotonated, dimeric and decarboxylated ions. The major product ions formed were: ionized halogen atom (chloride and bromide) and decarboxylated ions. After enrichment of the HAAs in Lichrolut EN adsorbent, the limits of detection obtained by LC-MS/MS analysis (between 0.04 and 0.3 ng mL(-1)) were comparable to those obtained by GC-MS after derivatization. Linearity with good correlation coefficients was obtained over two orders of magnitude irrespective of the compound. Adequate recoveries were achieved (60-102%), and the repeatability and intermediate precision were in the range of 2.4-6.6% and 3.8-14.8%, respectively. In order to demonstrate the usefulness of the method for routine HAAs monitoring, different types of water samples were analyzed. In swimming pool water samples the ∑HAAs were determined between 76 and 154 ng mL(-1).
Talanta 05/2012; 94:90-8. · 3.79 Impact Factor
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ABSTRACT: A new device for carbonyl compounds based on coupling on-line and miniaturizing both, sample pretreatment and chromatographic separation, is reported. Two capillary columns, a GC capillary column (95% methyl-5% phenyl substituted backbone, 70 cm × 0.32 mm i.d., 3 μm film thickness) in the injection valve for in-tube solid-phase microextraction (IT-SPME) and a Zorbax SB C18 (150 mm × 0.5 mm i.d., 5 μm particle diameter) LC capillary column were employed. Different combinations of IT-SPME and derivatization using 2,4-dinitrophenylhydrazine (DNPH) were examined for mixtures containing 15 carbonyl compounds (aliphatic, aromatic and unsaturated aldehydes and ketones). A screening analysis of aqueous extracts of atmospheric particulate PM(10) was carried out. Moreover, the possibility of coupling IT-SPME and conventional liquid chromatography is also tested. Derivatization solution and IT-SPME coupled to capillary liquid chromatography provided the best results for achieving the highest sensitivity for carbonyl compounds in atmospheric particulate analysis. Detection limits (LODs) using a photodiode array detector (DAD) were ranged from 30 to 198 ng L(-1), improving markedly those LODs reported by conventional SPME-LC-DAD.
Journal of chromatography. A 06/2011; 1218(30):4834-9. · 4.19 Impact Factor
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ABSTRACT: Simultaneous analysis of 24 carbonyl compounds (alkanals, unsaturated, dicarbonylic and aromatic aldehydes and ketones) derivatized with 2,4-dinitrophenylhydrazine and 16 polycyclic aromatic hydrocarbons (PAHs) using a photodiode-array (PDA) and a fluorescence (FL) detector in series is proposed. The separation is carried out with a reversed-phase column and gradient elution using four solvents (acetonitrile, water, tetrahydrofuran and methanol) in less than 35 min. Several critical pairs of carbonyl compounds with 3 and 4 carbon atoms and different functional groups, isomers of tolualdehyde, aromatic and aliphatic aldehydes were conditional on the gradient elution. Common pre-treatment for two groups of compounds consists in a step of extraction and derivatization in aqueous medium and a further clean-up using a polymeric phase SPE and concentration in a mixture of dichloromethane:methanol. A pre-concentration factor of 50 was achieved by this procedure. Acetone and formaldehyde blanks were minimized and remain controlled with a specific cleaning of glass material and washing the SPE cartridge. The limits of detection (LOD) ranged from 0.006 to 0.18 ng mL(-1) for PAHs and from 2.4 to 10.1 ng mL(-1) for carbonyl compounds and method precision was <or=15% for all analysed compounds. Recoveries were within the range of 95-104% for PAHs except for more volatile compounds (acenaphthene and fluorene) and within the range of 72-113% for carbonyl compounds. The method was applied in water-soluble fraction of PM(10) (atmospheric particulate matter with an aerodynamic diameter less than 10 microm) and the spectral contrast technique was used in the identification of carbonyl compounds.
Talanta 03/2010; 80(5):2083-92. · 3.79 Impact Factor
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ABSTRACT: The selective determination of the diamine ethylenediamine (EDA) in the presence of a higher amount of residual dimethylamine in cationic polymers has been developed. The strategy uses both a solution derivatization with a selective agent of primary amines such as o-phthaldialdehyde-N-acetyl-L-cysteine (OPA-NAC) and an in-tube solid-phase microextraction (IT-SPME) coupled to liquid chromatography (LC). A 70 cm long, 0.32 mm internal diameter, and 3 microm thick commercially available capillary column coated with 95% polydimethylsiloxane and 5% polydiphenylsiloxane was employed to replace the injection loop of a Rheodyne injection valve. A volume of 1 mL of derivatized sample was passed through the capillary, and 100 microL of water was later used for cleaning and filling the capillary. After, the injection was effected and the desorption of the derivative from the capillary was carried out in the dynamic mode using the mobile phase. Chromatographic separation was performed in less than 2 min using a monolithic silica column Onyx (100 mm x 3.0 mm i.d.) under isocratic conditions. The effect of several parameters affecting derivatization and IT-SPME was investigated. The quantification of EDA was realized over the range of 0.07-2 microg/mL with adequate linearity, accuracy, and reproducibility, and the limit of detection was 20 ng/mL. The method is rapid and low in cost, and sample handling and organic solvent consumption have been minimized. Its application to polymeric cationic surfactants used in water treatment allowed the selective quantification of residual EDA at low microgram per milliliter levels of concentration without off-line preconcentration.
Analytical Chemistry 07/2009; 81(14):5827-32. · 5.86 Impact Factor
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ABSTRACT: In industrial and pharmaceutical processes, the study of residual products becomes essential to guarantee the quality of compounds and to eliminate or minimize toxic residual products. Knowledge about the origin of impurities (raw materials, processes, the contamination of industrial plants, etc.) is necessary in preventive treatment and in the control of a product's lifecycle. Benzyl chloride is used as raw material to synthesize several quaternary ammonium compounds, such as benzalkonium chloride, which may have pharmaceutical applications. Benzaldehyde, benzyl alcohol, toluene, chloro derivatives of toluene, and dibenzyl ether are compounds that may be found as impurities in technical benzyl chloride. We proposed a high-performance liquid chromatography method for the separation of these compounds, testing two stationary phases with different dimensions and particle sizes, with the application of photodiode array-detection. The linearity for four possible impurities (benzaldehyde, toluene, alpha,alpha-dichlorotoluene, and 2-chlorotoluene) ranged from 0.1 to 10 microg/mL, limits of detection from 11 to 34 ng/mL, and repeatability from 1% to 2.9% for a 0.3-1.2 microg/mL concentration range. The method was applied to samples of technical benzyl chloride, and alpha,alpha-dichlorotoluene and benzaldehyde were identified by spectral analysis and quantitated. The selection of benzyl chloride with lower levels of impurities is important to guarantee the reduction of residual products in further syntheses.
Journal of chromatographic science 03/2009; 47(2):121-6. · 0.88 Impact Factor
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ABSTRACT: A method for the analysis of dimethylamine (DMA) by automated in-tube solid-phase microextraction (IT-SPME)-supported chemical derivatization coupled with high-performance liquid chromatography was developed. Extraction, derivatization and desorption were studied by using a capillary coated with 95% polydimethylsiloxane and 5% polydiphenylsiloxane. Solution derivatization and automated IT-SPME derivatization using 9-fluorenylmethyl chloroformate (FMOC) were compared. The proposed procedure provided adequate linearity, accuracy and precision in the 0.2-2.0 microg/mL concentration interval, and the limit of detection (LOD) was 50 ng/mL. The main advantages of the proposed procedure are: (i) no off-line sample manipulation, (ii) rapidity, as the total analysis time is about 10 min, (iii) specificity for the samples assayed, (iv) minimal consumption of FMOC reagent and (v) minimal residues. Therefore, the proposed method is an environmental-friendly and cost-effective alternative for the control of residual DMA in polymeric cationic surfactants used like flocculants in water treatment.
Journal of Chromatography 05/2008; 1188(2):118-23. · 4.53 Impact Factor
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ABSTRACT: A 80-cm length commercially available capillary coated with 95% polydimethylsiloxane and 5% polydiphenylsiloxane (TBR-5) was employed to carry out on-line extraction and preconcentration of dibuthyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP) in the chromatographic system. The coated capillary was placed between the sample injection loop and the injection needle of an autosampler. Variables affecting the automatic in-tube solid-phase microextraction (SPME) were optimized. A Genesis C(18) (5 cm x 4.6 mm i.d., 4 microm particle size) was employed as analytical column. The achieved limits of detection by use of diode array detection were 1 and 2.5 microg L(-1), respectively. The proposed conditions have been applied to determine those compounds at low ppb levels (< or =250 microg L(-1)) in aqueous samples. No matrix effect was found, and recoveries between 85 and 115% were obtained. The precision of the method was good, and the achieved intra- and inter-day variation coefficients were between 5 and 20%. The analysis time per sample was 20 min and any off-line pre-treatment of the samples was needed. The taken sample volume was 100 microL. Data on the application of the described method to the analysis of different water samples are presented.
Analytica chimica acta 03/2008; 610(2):268-73. · 4.31 Impact Factor
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ABSTRACT: The control of industrial products for minimization of their impact on the environment and human health requires the development of specific analysis methods. Information provided by these methods about toxic components, by-products, and other derivatives may also be useful to reduce the possible impact of industrial products. The studied compound in this paper, triethylbenzylammonium chloride (TEBA), is mainly used in industrial synthesis. This quaternary compound and its residual products coming from quaternization reaction (benzyl chloride, benzaldehyde, and benzyl alcohol) are analyzed by HPLC. The separation is based on control of the silanophilic contribution to TEBA retention because of the quaternary nature of this compound. The effect of the three buffers (sodium acetate, ammonium acetate, and sodium formate) and their concentrations in the chromatographic behavior of the quaternary compound is examined. The buffer cation and anion regulate TEBA retention. Also, the concentration of the quaternary compound is another parameter that had influence in some aspects of its chromatographic behavior (e.g., retention and symmetry). The proposed method is applied to TEBA synthesis along, with the formation and removal of impurities with the results compared with those obtained for the quaternary compound benzalkonium chloride.
Journal of chromatographic science 05/2006; 44(4):187-92. · 0.88 Impact Factor
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ABSTRACT: A systematic investigation of operational buffer systems, sample preparation and instrument parameters for achieving the best
possible performance for determinating an homologous series of N-benzyl-N-alkyl-N,N-dimethylammonium chloride compounds by
capillary zone electrophoresis with direct UV detection. The most effective separation was achieved within 3.5 min with the
addition of acetonitrile (40%) in a phosphate buffer (20 mM pH 5.2) using a 40 cm fused-silica capillary operating at 25 KV
and 20°C. Degassing of all electrolyte solutions and samples was very important. The linearity and repeatability for each
compounds were satisfactory. To improve detection limits, on-column sample preconcentration, sample stacking, was investigated
achieving a tenfold enrichment factor and quantitation limits about 10−7M.
Chromatographia 12/1999; 51(1):77-82. · 1.20 Impact Factor
