On-line coupling of a miniaturized bioreactor with capillary electrophoresis, via a membrane interface, for monitoring the production of organic acids by microorganisms.

Capillary electrophoresis (CE) can be a valuable tool for on-line monitoring of bioprocesses. Production of organic acids by phosphorus-solubilizing bacteria and fermentation of UHT milk were monitored and controlled by use of a membrane-interfaced dialysis device and a home-made microsampler for a capillary electrophoresis unit. Use of this specially designed sampling device enabled rapid consecutive injections without interruption of the high voltage. No additional sample preparation was required. The time resolution of monitoring in this particular work was approximately 2 h, but could be reduced to 2 min. Analytes were detected at low microg mL(-1) levels with a reproducibility of approximately 10%. To demonstrate the potential of CE in processes of biotechnological interest, results from monitoring phosphate solubilization by bacteria were submitted to qualitative and quantitative analysis. Fermentation experiments on UHT milk showed that monitoring of the processes by CE can provide good resolution of complex mixtures, although for more specific, detailed characterization the identification of individual substances is needed.

Therapeutic drug monitoring of antiepileptics by capillary electrophoresis. Characterization of assays via analysis of quality control sera containing 14 analytes.

Quality assurance is an important aspect in therapeutic drug monitoring (TDM). Capillary electrophoresis (CE) assays for determination of (i) ethosuximide via direct injection of serum or plasma, (ii) lamotrigine after protein precipitation by acetonitrile and analysis of an aliquot of the acidified supernatant, and (iii) carbamazepine and carbamazepine-10,11-epoxide after solute extraction followed by analysis of the reconstituted extract are characterized via analysis of a large number of commercial quality control sera containing up to 14 analytes (9 of them are anticonvulsants) in sub-therapeutic, therapeutic and toxicologic concentration levels. CE data obtained in single determinations are shown to compare well with the spike values and the mean of data determined in other laboratories using immunoassays and/or high-performance liquid chromatography, values that are reported by the external quality control scheme. Carbamazepine and ethosuximide drug levels are also shown to agree well with those determined in our departmental drug assay laboratory using automated immunoassays. The presented data reveal the effectiveness of assay assessment via analysis of quality control sera and confirm the robustness of the assays for TDM in a routine setting.

Determination of carbamazepine and carbamazepine-10,11-epoxide in human serum and plasma by micellar electrokinetic capillary chromatography in the absence of electroosmosis.

Therapeutic drug monitoring of carbamazepine (CBZ), a widely used antiepileptic drug, is required for optimization of pharmacotherapy with this drug and for assessment of the patient's compliance to therapy. The suitability of employing micellar electrokinetic capillary chromatography (MEKC) in the absence of electroosmosis for the determination of CBZ and its main metabolite carbamazepine-10,11-epoxide (CBZE) in extracts of human serum and plasma is reported. Using micelles formed by dodecyl sulfate, analyses performed in untreated fused-silica capillaries at acidic pH and in commercially available coated capillaries under application of reversed polarity are compared. Uncoated and polyvinyl alcohol coated capillaries proved to be unsuitable for this purpose, whereas capillaries coated with linear polyacrylamide and N-acryloylaminoethoxyethanol and operated at pH 7.6 are shown to provide high-quality and reliable data on a short time scale. Assay performance is discussed via statistical analysis of the data produced from a set of quality control sera that contain up to 14 different drugs and via analysis of patient samples. Intraday and interday imprecision data for concentrations between 4.0 and 84 microM are demonstrated to be < 10%. Run times are shown to be < 50% compared to those observed in conventional MEKC at alkaline pH (i.e., in the presence of electroosmosis).

Head column field-amplified stacking from the flow: stabilization of the sample plug position by using backpressure.

Head column-field amplified sample stacking (HC-FASS) is one of the most powerful concentration techniques in capillary electrophoresis. In the present work we demonstrate that a laboratory-designed pneumatic sampler not only enables us to easily perform HC-FASS from stagnant sample solutions but also permits us to carry out HC-FASS from sample stream, which creates an opportunity to lower the detection limit of analytes further. The influence of stacking time in case of the flowing sample on peak efficiencies and resolution is discussed. It is demonstrated that the sample plug length can be kept constant by monitoring the current in the capillary, which controls a feedback system based on backpressure at the capillary outlet.

Stacking from the Sample Stream in CZE Using a Pneumatically Driven Computerized Sampler.

It is demonstrated that a pneumatically driven computerized sampling device for capillary electrophoresis facilitates sample stacking by the head-column field amplification (HCFA) technique. This device utilizes a rapid exchange between buffer and sample in a narrow channel at the separation capillary inlet and makes possible the combination of two classical injection modes [Formula: see text] the electrokinetic and hydrodynamic modes. Detection limits obtained were about 9 nM for alkylbenzylamine cations with common UV detection.