In-line preconcentration capillary zone electrophoresis for the analysis of haloacetic acids in water.

Two in-line enrichment procedures (large volume sample stacking (LVSS) and field amplified sample injection (FASI)) have been evaluated for the CZE analysis of haloacetic acids (HAAs) in drinking water. For LVSS, separation on normal polarity using 20 mM acetic acid-ammonium acetate (pH 5.5) containing 20% ACN as BGE was required. For FASI, the optimum conditions were 25 s hydrodynamic injection (3.5 kPa) of a water plug followed by 25 s electrokinetic injection (-10 kV) of the sample, and 200 mM formic acid-ammonium formate buffer at pH 3.0 as BGE. For both FASI and LVSS methods, linear calibration curves (r(2) >0.992), limit of detection on standards prepared in Milli-Q water (49.1-200 µg/L for LVSS and 4.2-48 µg/L for FASI), and both run-to-run and day-to-day precisions (RSD values up to 15.8% for concentration) were established. Due to the higher sensitive enhancement (up to 310-fold) achieved with FASI-CZE, this method was selected for the analysis of HAAs in drinking water. However, for an optimal FASI application sample salinity was removed by SPE using Oasis WAX cartridges. With SPE-FASI-CZE, method detection limits in the range 0.05-0.8 µg/L were obtained, with recoveries, in general, higher than 90% (around 65% for monochloroacetic and monobromoacetic acids). The applicability of the SPE-FASI-CZE method was evaluated by analyzing drinking tap water from Barcelona where seven HAAs were found at concentration levels between 3 and 13 µg/L.

Fast liquid chromatography/multiple-stage mass spectrometry of coccidiostats.

Drugs that are used as medicines and also as growth promoters in veterinary care are considered as emerging environmental contaminants and in recent years concern about their potential risk to ecosystems and human health has risen. In this paper we used a method based on liquid chromatography/electrospray tandem mass spectrometry to analyze eight coccidiostatic compounds: diclazuril, dinitrocarbanilide (the main metabolite of nicarbazin), robenidine, lasalocid, monensin, salinomycin, maduramicin and nasarin. Multiple-stage mass spectrometry (MSn) based on the precursor ions [M+Na]+ (polyether ionophores), [M+H]+ (robenidine) and [M-H]- (diclazuril and dinitrocarbanilide) was used to study the fragmentation of these compounds. MSn data and genealogical relationships were used to propose a tentative assignment of the different fragment ions. Loss of water, decarboxylations, ketone beta-cleavages and rearrangement of cyclic ethers and amide groups were some of the fragmentations observed for these compounds. Liquid chromatography with a sub-2 microm particle size column was coupled to tandem mass spectrometry (LC/MS/MS) allowing the separation of these compounds in less than 7 min. Method detection limits ranging from 11 to 71 ng L(-1) and run-to-run values in terms of relative standard deviation (RSD) (up to 12%) were obtained.

Liquid chromatography/multi-stage mass spectrometry of bisphenol A and its halogenated derivatives.

We report a liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for analyzing bisphenol A (BPA) and its halogenated derivatives. Since only tetrachlorobisphenol A and tetrabromobisphenol A (TBBPA) are commercially available, mono-, di- and trichlorobisphenol A were synthesized and purified in order to be used as analytical standards. This family of compounds was studied using electrospray ionization and an ion trap mass analyzer in order to characterize the new compounds and to propose fragmentation pathways. Multi-stage mass spectrometry was used to confirm the genealogical relationship between the ions. Some product ions were traced from MS/MS to MS(4) and the labelled compounds BPA-d(16) and TBBPA-(13)C(12) were used to assign some product ion structures. In general, the deprotonated molecule [M--H](-) loses a methyl and/or a halogen group during both MS/MS and MS(3), while the neutral loss of CO was also observed in MS(3) spectra. We selected the most intense and characteristic MS/MS transitions for LC/MS/MS analysis. LC separation was performed in a reversed-phase column; methanol/water (no additives) was used as the mobile phase in gradient elution mode; and BPA-d(16) was chosen as the internal standard. Solid-phase extraction (SPE) was used to pre-concentrate and to clean up water samples. The SPE LC/MS/MS method allows BPA and its halogenated derivatives to be detected at a few parts-per-billion (ppb) in surface water.

Microemulsion electrokinetic chromatography for the analysis of acrylamide in food.

The influence of microemulsion electrokinetic chromatography (MEEKC) operating conditions, such as the type of water-immiscible alcohol, aqueous phosphate buffer concentration, pH, as well as the addition of methanol and 2-propanol, on acrylamide migration has been studied. These parameters have been optimized taking into account the presence of matrix signals, in order to avoid the interference of these peaks in acrylamide determination. The best separations were achieved using a microemulsion consisting of 0.8% m/v n-amyl alcohol, 3.3% m/v sodium dodecyl sulfate (SDS), 6.6% m/v 1-butanol, and 89.3% m/v 40 mM phosphate buffer at pH 6.5 working at 15 kV in uncoated silica capillaries. Linear calibration curves over the range studied (1.25-125 microg x mL(-1)), the detection limit (0.70 microg x mL(-1)), and both run-to-run (up to 3.4% for concentration and 1.6% for time values) and day-to-day precision (lower than 11.6% for concentration) have been established. Finally, the applicability of the MEEKC method developed has been demonstrated by analyzing levels of acrylamide present in samples of home-made French fries.

Multimodal open-tubular capillary electrochromatographic analysis of amines and peptides.

This study describes a comparison of different modes of open-tubular electrochromatography (OTCEC) in bare and etched capillaries. To carry out the investigation, the separation of impurities of two synthetic peptides and the separation of a mixture of five heterocyclic aromatic amines were studied. Three different types of stationary phase were evaluated: (i) fluorosurfactants (anionic and zwitterionic) adsorbed in the inner wall of the capillary (electrochromatography with dynamically modified stationary phases (DMS)CEC); (ii) physically adsorbed polymers (DMA-SO(3-) and DMA-N(+)(CH(3))(3)) and (iii) chemically modified capillaries (C(18), cholesteryl 10-undecanoate and diol). The results confirm that electrochromatography can be a viable alternative to capillary electrophoresis (CE) and liquid chromatography, more established separation techniques. It is possible to differentiate some minor species for the synthetic peptides that cannot be resolved by CE or high-performance liquid chromatography (HPLC). Moreover the separation of the amine mixture depends strongly on the stationary phase used.