Determination of carbohydrates by capillary electrophoresis with electrospray-mass spectrometric detection.

A method for the determination of underivatized carbohydrates using capillary electrophoresis (CE) with detection by electrospray ionization-mass spectrometry (ESI-MS) presented. Highly alkaline carrier electrolytes based on volatile organic bases like is diethylamine (DEA) combined with MS detection in the negativ-ion mode proved to be the optimum solution for the separation and detection of these analytes. Optimization of the carrier electrolyte composition has been performed with respect to its pH, ionic strength as well as the addition of an organic modifier. The influence of the DEA concentration in the sheath liquid on parameters like peak shapes or signal-to-noise (S/N) ratios was also investigated. Limits of detection (LOD) were in the range of 0.5-3.0 mgL(-1) and calibration was linear over an order of magnitude for almost all solutes investigated. Finally, the applicability of this method for the analysis of real samples was demonstrated with wine samples.     

Capillary Electrochromatography of Pyrimidine Derivatives Using UV and Mass Spectrometric Detection

Summary.  The separation of pyrimidine derivatives by capillary electrochromatography (CEC) using either UV or mass spectrometric detection is described. For UV detection an aqueous phosphate carrier electrolyte containing acetonitrile is employed. The results are compared to the analysis of the same compounds by micellar electrokinetic chromatography in terms of selectivity, migration times, linearity, and detection limits. For the combination of CEC and mass spectrometry (MS) an inexpensive way to couple commercially available instruments is presented; the interface consists of an electrically grounded stainless steel connector (containing a stainless steel frit) serving as the electrode and coupling the CEC capillary with a fused silica transfer capillary to the MS instrument. Alternatively, a PEEK adapter combining the CEC capillary and a grounded stainless steel transfer capillary serving as the electrode is employed. To avoid the formation of hydrogen gas at the coupling piece or the transfer capillary, p-benzoquinone is added to the carrier electrolyte consisting of aqueous ammonium acetate and acetonitrile. Received July 21, 1999. Accepted July 29, 1999     

Comparison of different extraction methods for the determination of statin drugs in wastewater and river water by HPLC/Q-TOF-MS

Three preconcentration techniques including solid phase extraction (SPE), dispersive liquid-liquid microextraction (DLLME) and stir-bar sorptive extraction (SBSE) have been optimized and compared for the analysis of six hypolipidaemic statin drugs (atorvastatin, fluvastatin, lovastatin, pravastatin, rosuvastatin and simvastatin) in wastewater and river water samples by high performance liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry (HPLC/Q-TOF-MS). Parameters that affect the efficiency of the different extraction methods such as solid phase material, sample pH and elution solvent in the case of SPE; the type and volume of the extracting and dispersive solvent, pH of sample, salt addition and number of extraction steps in the case of DLLME; and the stirring time, pH of sample, sample volume and salt addition for SBSE were evaluated. SPE allowed the best recoveries for most of the analytes. Pravastatin was poorly extracted by DLLME and could not be determined. SBSE was only applicable for lovastatin and simvastatin. However, despite the limitations of having poorer recovery than SPE, DLLME and SBSE offered some advantages because they are simple, require low organic solvent volumes and present low matrix effects. DLLME required less time of analysis, and for SBSE the stir-bar was re-usable. SPE, DLLME and SBSE provided method detection limits in the range of 0.04-11.2 ng L⁻¹, 0.10-17.0 ng L⁻¹ for 0.52-2.00 ng L⁻¹, respectively, in real samples. To investigate and compare their applicability, SPE, DLLME and SBSE procedures were applied to the detection of statin drugs in effluent wastewater and river samples.     

Development of a highly sensitive gas chromatography–mass spectrometry method preceded by solid‐phase microextraction for the analysis of propofol in low‐volume cerebral microdialysate samples

To date, the commonly used intravenous anesthetic propofol has been widely studied, and fundamental pharmacodynamic and pharmacokinetic characteristics of the drug are known. However, propofol has not yet been quantified in vivo in the target organ, the human brain. Here, cerebral microdialysis offers the unique opportunity to sample propofol in the living human organism. Therefore, a highly sensitive analytical method for propofol quantitation in small sample volumes of 30 μL, based on direct immersion solid‐phase microextraction was developed. Preconcentration was followed by gas chromatographic separation and mass spectrometric detection of the compound. This optimized method provided a linear range between the lower limit of detection (50 ng/L) and 200 μg/L. Matrix‐matched calibration was used to compensate recovery issues. A precision of 2.7% relative standard deviation between five consecutive measurements and an interday precision of 6.4% relative standard deviation could be achieved. Furthermore, the permeability of propofol through a cerebral microdialysate system was tested. In summary, the developed method to analyze cerebral microdialysate samples, allows the in vivo quantitation of propofol in the living human brain. Additionally the calculation of extracellular fluid levels is enabled since the recovery of the cerebral microdialysis regarding propofol was determined.     

Versuche zur elektrochemischen Detektion von Zuckern

Ohne Zusammenfassung     

Determination of organic UV filters in water by stir bar sorptive extraction and direct analysis in real-time mass spectrometry

A screening method for analyzing environmental waters contaminated with UV filters using direct analysis in real-time mass spectrometry (DART-MS) was developed. To demonstrate the suitability of DART-MS a test set of seven organic UV filters, namely benzophenone-3 (BP-3), ethylhexyl dimethyl p-aminobenzoate (OD-PABA), 4-t-butyl-4′-methoxydibenzoylmethane (BM-DBM), homomethyl salicylate (HMS), 2-(ethylhexyl) salicylate (EHS), octocrylene (OC), and 4-methylbenzylidene camphor (4-MBC), was defined. In the first step, standard solutions of the analytes prepared in methanol were investigated in order to determine optimum parameters for the DART-MS. Because of the very low concentrations of UV filters expected in environmental water samples, a pre-concentration step using stir bar sorptive extraction was performed. DART-MS allows the direct, simple and rapid semi-quantitative analysis of the analytes enriched on the surface of the polydimethylsiloxane-coated stir bars. The optimized method provided calibration curves with correlation coefficients R > 0.959, repeatability from 5% (for 4-MBC) to 30% (for BM-DBM) relative standard deviation and limits of detection lower than 40 ng L⁻¹ for all analytes. Finally, real lake water samples from locations with typical leisure activities were analyzed. Results obtained with the developed DART-MS method were cross-checked by confirmatory analysis using thermodesorption gas chromatography mass spectrometry (TD-GC-MS). Thereby, it could be demonstrated that both analytical methods provide comparable concentrations for the UV filters in the lake water samples.