A highly sensitive procedure to detect multiple pesticides at trace levels in foods is presented. Initially a comparative study between capillary electrophoresis (CE)-UV and CE-mass spectrometry (MS) is carried out analyzing five pesticides not studied up to now (pyrimethanil, pyrifenox, cyprodinil, cyromazine, and pirimicarb). The comparison between CE-UV and CE-MS is established in terms of separation efficiency, speed of analysis, reproducibility, and sensitivity. A good separation of these compounds is achieved by both techniques using a volatile aqueous buffer containing 0.3 M ammonium acetate/acetic acid at pH 4. Time analysis reproducibility is studied for the same day (n = 5) and three different days (n = 15), showing no significant differences between CE-UV and CE-MS. The study on peak areas reproducibility shows a slightly worse reproducibility for CE-MS compared with CE-UV. The best limit of detection (LOD) that can be achieved for these pesticides using CE-UV was 0.6 microg/mL. CE-MS provides LODs one order of magnitude better than CE-UV. Chemometrics are used to optimize the multiple parameters that play a role in solid-phase microextraction (SPME) and CE-MS analysis (e.g., extraction and desorption times, nebulizer pressure, dry gas flow, dry gas temperature, percentage of organic solvent and acid in the sheath liquid, etc.). The combined use of chemometrics and SPME-CE-MS clearly improves the LODs that can be achieved allowing the detection of pesticides at concentrations down to 15 ng/mL. The usefulness of this approach is demonstrated detecting multiple pesticides in different food samples as grapes and orange juice in a single run. The concentrations detected are below the maximum residue limits (MRLs) permitted for these pesticides in foods corroborating the value of our approach. This work demonstrates, to our knowledge for the first time, the good possibilities of the combined use of SPME-CE-MS and chemometrics.

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Chiral analysis of pollutants and their metabolites by capillary electromigration methodsChiral separation of enantiomers is one of the most challenging tasks for any analytical technique including CE. Since the first report in 1985 showing the great possibilities of CE for the separation of chiral compounds, the amount of publications concerning this topic has quickly increased. Although chiral electromigration methods have mainly been used for enantioseparation of drugs and pharmaceuticals, they have also been applied to analyze chiral pollutants. This article intends to provide an updated overview, including works published till January 2005, on the principal applications of CE to the chiral analysis of pollutants and their metabolites, with especial emphasis on articles published in the last 10 years. The main advantages and drawbacks regarding the use of CE for chiral separation of pollutants are addressed including some discussion on the foreseen trends of electromigration procedures applied to chiral analysis of contaminants. IntroductionSeparation of chiral compounds is an interesting and challenging topic of research in many analytical chemistry areas, especially in the biomedical, pharmaceutical, and environmental fields where pure enantiomeric forms are widely required. It is already well-known that enantiomers, in spite of their very similar structure, when exposed to an identical biological environment can show very different biological activity. Furthermore, as a general rule, when the toxicological effect of an active substance is directly related to its desired biological activity, the most active isomer is usually the most toxic one Abbreviations: Allyl-TER, 1-allylterguride; ANDSA, 7-aminonaphthalene-1,3-disulfonic acid; ANSA, 5-aminonaphthalene-1-sulfonic acid; ANTS, 8-aminonaphthalene-1,3,6-trisulfonic acid; CA, chrysanthemic acid; CM-ª-CD, carboxymethylated-g-CD; CMBA, 2-(4-chlorophenyl)-3-methylbutanoic acid; 2,2-CPPA, 2-(2-chlorophenoxy)-propionic acid; 2,3-CPPA, 2-(3-chlorophenoxy)-propionic acid; 2,4-CPPA, 2-(4-chlorophenoxy)-propionic acid; â-CD-NH 2 , 6-monodeoxy-6-monoamino-b-CD; â-CD- (NH 3 )

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In this work, the determination of a group of triazolopyrimidine sulfoanilide herbicides (cloransulam-methyl, metosulam, flumetsulam, florasulam and diclosulam) in soy milk by capillary electrophoresis-mass spectrometry (CE-MS) is presented. The main electrospray interface (ESI) parameters (nebulizer pressure, dry gas flow rate, dry gas temperature and composition of the sheath liquid) are optimized using a central composite design. To increase the sensitivity of the CE-MS method, an off-line sample preconcentration procedure based on solid-phase extraction (SPE) is combined with an on-line stacking procedure (i.e. normal stacking mode, NSM). Samples could be injected up to 100 seconds, providing limits of detection (LODs) down to 74 μg/L, i.e., in the low ppb level, with relative standard deviation values (RSD, %) between 3.8% and 6.4% for peak areas for the same day, and between 6.5% and 8.1% for three different days. The usefulness of the optimized SPE-NSM-CE-MS procedure is demonstrated through the sensitive quantification of the selected pesticides in soy milk samples.