Electrokinetic supercharging in CE for the separation and preconcentration of barbiturate drugs in urine samples

10.1002/jssc.20120069

Different strategies for the preconcentration and separation of parabens by capillary electrophoresis

10.1002/elps.201200147Several strategies, namely large volume sample stacking (LVSS), field-amplified sample injection (FASI), sweeping, and in-line SPE-CE, were investigated for the simultaneous separation and preconcentration of a group of parabens. A background electrolyte (BGE) consisting of 20 mM sodium dihydrogenphosphate (pH 2.28) and 150 mM sodium dodecyl sulphate (SDS) with 15 % ACN was used for the separation and preconcentration of the compounds by sweeping, and a BGE consisting of 30 mM sodium borate (pH 9.5) was used for the separation and preconcentration of the compounds by LVSS, FASI, and in-line SPE-CE. Several factors affecting the preconcentration process were investigated in order to obtain the maximum enhancement of sensitivity. The limits of detection (LODs) obtained for parabens were in the range of 18-27 ng/mL, 3-4 ng/mL, 2 ng/mL, and 0.01-0.02 ng/mL, and the sensitivity evaluated in terms of peak areas was improved up to 28-, 109-, 232-, and 19,000-fold for sweeping, LVSS, FASI, and in-line SPE-CE, respectively. These preconcentration techniques showed potential as good strategies for focusing parabens. The four methods were validated with standard samples to show the potential of these techniques for future applications in real samples, such as biological and environmental samples

On-line trace enrichment of polar pesticides in environmental waters by reversed-phase liquid chromatography-diode array detection-particle beam mass spectrometry.

The determination of a group of pesticides by RPLC-diode array detection, coupled on-line to particle beam MS, is developed for the analysis of different environmental water. On-line trace enrichment of 100 ml of sample on a PLRP-S precolumn allows the determination of most pesticides at levels between 0.2 and 5 μg

Determination of UV filters in river water samples by in-line SPE-CE-MS

10.1002/elps.201200267The use of SPE coupled in-line to CE using electrospray MS detection (in-line SPECE- ESI-MS) was investigated for the preconcentration and separation of four UV filters: benzophenone-3 (BP-3), 2,2-dihydroxy-4-methoxybenzophenone (DHMB), 2,4- dihydroxybenzophenone (DHB) and 2-phenylbenzimidazole sulphonic acid (PMDSA). First, a CE-ESI-MS method was developed and validated using standard samples, obtaining LODs between 0.06 g/mL and 0.40 g/mL. For the in-line SPE-CE-ESI-MS method, three different sorbents were evaluated and compared: Oasis HLB, Oasis MCX, and Oasis MAX. For each sorbent, the main parameters affecting the preconcentration performance, such as sample pH, volume, and composition of the elution plug, and sample injection time were studied. The Oasis MCX sorbent showed the best performance and was used to validate the in-line SPE-CE-ESI-MSmethodology. The LODs reached for standard samples were in the range between 0.01 and 0.05 ng/mL with good reproducibility and the developed strategy provided sensitivity enhancement factors between 3400-fold and 34 000-fold. The applicability of the developed methodology was demonstrated by the analysis of UV filters in river water samples