Wolfgang Buchberger

Determination of drug residues in water by the combination of liquid chromatography or capillary electrophoresis with electrospray mass spectrometry.

Methods for the determination of drug residues in water have been developed based on the combination of liquid chromatography (LC) or capillary electrophoresis (CE) with mass spectrometry (MS). For HPLC-MS two types of interfaces (pneumatically assisted electrospray ionization interface or an atmospheric pressure chemical ionization interface, respectively) were employed and compared in terms of detection limits. 2 mM Ammonium acetate at pH 5.5 and a methanol gradient was used for the HPLC-MS allowing the separation of a number of drugs such as paracetamol, clofibric acid, penicillin V, naproxen, bezafibrate, carbamazepine, diclofenac, ibuprofen and mefenamic acid. A 20 mM ammonium acetate solution, pH 5.1 was employed for the separation of clofibric acid, naproxen, bezafibrate, diclofenac, ibuprofen and mefenamic acid by CE-MS. Sample pretreatment was performed by solid-phase extraction (SPE) for HPLC-MS or by a combination of liquid-liquid extraction and SPE for CE-MS. The applicability of both the HPLC-MS and CE-MS method was demonstrated for several river water samples.

Current approaches to trace analysis of pharmaceuticals and personal care products in the environment.

A large number of xenobiotics including pharmaceuticals and personal care products are continuously released into the environment. Effluents from sewage treatment plants are well known to be the major source for introduction of pharmaceuticals and personal care products into the aquatic system. In recent years, reliable methods have been established for residue analysis of these pollutants down to low ng/L levels. In this review, the different approaches to their trace determination are reviewed with special attention being paid to sample preparation procedures, state-of-the-art high-performance separation methods hyphenated with mass spectrometry, and immunochemical methods.

Effects of carrier electrolyte composition on separation selectivity in capillary zone electrophoresis of low- molecular-mass anions

Abstract A systematic investigation was carried out on the influence of carrier electrolyte composition on separation selectivity in capillary zone electrophoresis of inorganic anions. Chromate, chloride, sulphate or nitrate was used as the carrier electrolyte, each containing a quaternary ammonium salt to reverse the electro-osmotic flow. The concentration and nature of the carrier electrolyte salt affected the separation order only to a minor degree. Much more pronounced effects could be achieved by adding organic solvents to the carrier electrolyte or by using different quaternary ammonium salts. Chemical modification of the inner wall of the fused-silica capillary did not affect the migration order significantly. There is no indication of retention by effects similar to ion-interaction chromatography as long as capillaries with an inner diameter of 75 μm are used. Nevertheless, such effects might play an important role for capillaries with diameters of 10 μm or less.

Metal ion capillary zone electrophoresis with direct UV detection: determination of transition metals using an 8-hydroxyquinoline- 5-sulphonic acid chelating system

Abstract The application of capillary zone electrophoresis to the separation and determination of metal ions after the precolumn formation of negatively charged chelates is described. Multi-component mixtures of transition metal complexes with 8-hydroxyquinoline-5-sulphonic acid (HQS) were separated in about 10 min in a fused-silica capillary column with a borate buffer of pH 9.2 at an applied voltage of 15 kV followed by direct UV detection. The capillary pretreatment with an electroosmotic flow modifier, namely a tetraalkylammonium salt, is necessary to achieve resonable migration times of these metal complexes. Incorporating the chelating reagent in the electrophoretic buffer markedly improves the detectability of relatively unstable chelates, such as those of Co(II), Zn(II) and Cd(II), and allows the separation of metal ions that form unstable HQS chelates, such as Mn(II) and alkaline earth metals. The effects of electrophoretic buffer parameters affecting the complexation reaction and migration behaviour are discussed. Linearity of calibration graphs is observed for about three orders of magnitude with sub-ppm detection limits. The applicability of the method to the analysis of real samples is demonstrated.

Evaluation of carrier electrolytes for capillary zone electrophoresis of low-molecular-mass anions with indirect UV detection

Abstract Indirect UV detection in capillary zone electrophoresis has been investigated with respect to transfer ratios for low-molecular-mass analyte anions and chromate or various aromatic carboxylic acids acting both as carrier electrolytes and detection probes. The transfer ratio can be regarded as a measure of the effectiveness by which analyte ions displace the UV-absorbing probe ions and has been found to depend on the relative mobilities of the analyte and the carrier. Highest values of transfer ratios have occurred when the carrier ion had a higher mobility than the analyte ion. This trend follows the Kohlrausch theory, but still considerable deviations between calculated and experimental data have been encountered. Consideration of the transfer ratio, the molar absorptivity of the probe and the degree of separation achieved, suggests that chromate is the best electrolyte for high-mobility inorganic anions. The results obtained enable predictions of the most suitable carrier electrolyte for various applications with indirect UV detection.

Analysis of melamine in milk powder by CZE using UV detection and hyphenation with ESI quadrupole/TOF MS detection

An easy to employ method for the determination of melamine in milk powder samples using CZE with either UV or MS detection is presented. The separation capabilities of CZE allowed keeping sample preparation rather simple. Before analysis, milk powder samples were dissolved in water, de‐fatted with dichloromethane and diluted with ACN to precipitate the protein, filtrated and injected without further pretreatment. The developed CZE method allowed the determination of melamine in milk powder down to a level of 0.50 mg/kg using UV detection and 0.25 mg/kg when ESI quadrupole/TOF MS was employed for detection.

Determination of organic acids in food samples by capillary zone electrophoresis

A comprehensive survey of the use of capillary zone electrophoresis for the determination of organic acids in food and beverage samples is presented. The analytes discussed in this paper include low-molecular-mass organic acids, amino acids, vitamin related compounds and free fatty acids.

Separation of metallo-cyanide complexes by capillary zone electrophoresis

Abstract The optimisation of electrolyte systems for the separation and detection of cyanide complexes of Au, Pt, Fe(II), Fe(III), Pd, Cu(I), Co, Ag, Cr and Ni using capillary zone electrophoresis is described. A phosphate-tri-ethanolamine buffer at pH 8.5 was chosen for the separation. The factors affecting resolution and analysis time include the addition of ion-pairing reagents (which also act as electroosmotic mobility modifiers) as well as organic solvents to the carrier electrolyte. Less stable cyano complexes [such as those of copper(I)] require the presence of low concentrations of free cyanide in the electrolyte in order to achieve acceptable peak shapes. Direct UV detection at 214 nm is feasible for most of the metallo-cyanide complexes although some of them giver higher response in an indirect mode at 254 nm using trimellitate as the carrier electrolyte. Approaches for preconcentration are discussed in order to achieve detection limits necessary for environmental samples and other applications.

Application of HPLC-ICP-MS to speciation of cisplatin and its degradation products in water containing different chloride concentrations and in human urine

Cisplatin, mono- and diaquacisplatin were measured in aquatic samples and in diluted urine of a cancer patient by HPLC-ICP-MS. On-line IDMS was applied for accurate, species unspecific quantification. Limits of detection of 0.74, 0.69 and 0.65 µg L−1 (3 s criterion) were calculated for cisplatin, monoaqua- and diaquacisplatin, respectively. Degradation kinetics of 6 × 10−6 M cisplatin were determined over a period of 48 h in solutions containing 100, 50 and 0 mg L−1 chloride, showing the suitability of the HPLC-ICP-MS method for kinetic model studies. The first order rate constants k1 of cisplatin aquation for the three chloride concentrations were 1.79 × 10−5, 1.68 × 10−5 and 2.06 × 10−5 s−1. For cisplatin anatation (second order reverse reaction), rate constants of k−1 = 6.5 × 10−3, 5.8 × 10−3 and 4.1 × 10−3 M−1 s−1 could be assessed. At low chloride levels, no equilibrium was established between cisplatin and its degradation products. It was found that the intermediately formed mono- and diaquacisplatin-products started to decay after several hours. Diluted urine of a cancer patient contained the parent drug cisplatin and a considerable fraction of highly active monoaquacisplatin, as well as several unknown platinum species.

Prospects for detection and sensitivity enhancement of inorganic ions in capillary electrophoresis

While capillary electrophoresis (CE) is now a well established technique for the determination of inorganic ions, the current sensitivity limitations of the method are an evident obstacle to progress. The advances in CE methodology to compensate for these limitations are reviewed in this paper with particular attention payed to non-absorbance-based detection techniques. Recently developed detection modes for inorganic cationic and anionic species are compared in terms of applicability, effects on separation efficiency, costs and manufacturing concerns. A comprehensive survey of sensitivity enhancements based on on-capillary and pre-electrophoresis concentration techniques and on chemical derivatization is also presented along with the most typical application examples.