High throughput screening of complex biological samples with mass spectrometry – from bulk measurements to single cell analysis

We review the state of the art in HTS using mass spectrometry with minimal sample preparation from complex biological matrices. We focus on industrial and biotechnological applications.

Analysis of whole-blood cyclosporin G by liquid chromatography in renal transplant recipients

Cyclosporin G (CsG) is less nephrotoxic than Cyclosporin A (CsA) and is undergoing clinical trials for use as an immunosuppressive agent after renal transplantation. In this study, CsG was measured by a rapid high-performance liquid chromatography (HPLC) technique in blood samples (n = 107) received from renal transplant recipients. The HPLC assay proved to be analytically suitable in that it was sensitive, linear, and precise and had high recovery (102%). However, interference was observed from some potentially co-administered drugs such as calcitriol, ferrous sulfate, hydrazaline, and minoxidil. The HPLC assay for CsG correlated well with a FPIA (Abbott TDx), FPIA = 0.964 (HPLC) + 33.59, r = 0.9819, Sy/x = 36.66 for patients receiving a low dose of CsG (5 mg/kg/day) and a high dose (10 mg/kg/day). Furthermore, the HPLC technique was capable of measuring predictable CsG concentrations when the drug was tapered to lower doses at various stages of the 16 week clinical trial. The HPLC for CsG has the further advantage that the same system and mobile phase can be used to measure CsA while using CsC as the interval standard.

Novel strategies for clinical drug analysis with new column technology in liquid chromatography

Clinical drug analysis has been the focus of much attention and controversy because of the increase in substance abuse testing of addicts, patients, employees and others, in addition to the rapidly growing fields of therapeutic drug monitoring and clinical toxicology. This review focuses on the latest methodological and technological advances in liquid chromatography (LC) as it is applied to clinical drug analysis. Based on the author's experience, key chromatographic parameters such as carbon load, functionalities and temperature are proposed for the separation of structurally similar metabolites and for resolving chromatographic interferences by other drugs and metabolites. Novel sample preparation for cyclosporine and gradient elution of its metabolites are reviewed, followed by an update on monitoring of 3'-azido-3'-deoxythymidine with emphasis on automated sample preparation. Various approaches of direct sample analysis are advocated for increased efficiency as a result of minimal sample preparation and potential advantages such as decreased exposure of personnel to infectious samples. An update of microbore LC indicates that 2-mm columns may be readily used for clinical paediatric and neonatal analysis without dedicated chromatographs. Potential applications of multidimensional-multimodal chromatography include analyses of a cocaine impurity, anticonvulsants, antidepressants, and five ingredients of a common cold medication.

Determination of cyclosporin A in the serum of kidney transplant patients by rapid-flow fractionation and normal-phase high-performance liquid chromatography

High-performance liquid chromatography was used to determine cyclosporin A (CsA) concentrations in the serum of kidney transplant patients by rapid-flow fractionation (RFF) followed by silica gel normal-phase high-performance liquid chromatography (HPLC). The extraction of CsA from serum was achieved by RFF using a short diatomaceous earth column eluted with diethyl ether-n-hexane (50:50, v/v). The recovery was more than 80% at concentrations of 50-150 micrograms/l. The concentration of this compound was determined by HPLC using a conventional silica gel column with 3.3 M ammonia solution-ethanol-n-hexane (0.31:10.69:89, v/v) as eluent. Concentration calibration was made on the basis of the peak-height ratio of CsA to CsD as the internal standard. The coefficient of variation of this assay was less than 6.5% and the results were used for the therapeutic drug monitoring of CsA administered to kidney transplant patients. Measurements of the CsA concentrations in 160 serum specimens were also made by conventional radioimmunoassay (RIA) using commercial kits. The data obtained by RIA were on average 2.5 times those obtained by HPLC. Higher values in RIA were observed characteristically with patients with severe disfunction resulting from CsA hepatotoxicity. From the results, it appeared that HPLC rather than RIA provides more precise and reliable values for the concentration of this drug.

Advances in liquid chromatography and related methodologies for therapeutic drug monitoring

In this article the merits of current liquid chromatography (LC) columns and techniques are reviewed, to include the following topics: (1) a brief introduction to rational therapeutic drug monitoring (TDM) to justify drug measurements; (2) selected recent survey results from the College of American Pathologists (CAP) to establish the current utilization pattern of LC for TDM in the USA; (3) LC analyses of major classes of drugs--antiarrhythmics, antidepressants, antiepileptics, antimicrobials, cyclosporine, and others--with emphasis on analysis of these drugs in human serum or plasma, by focusing on the less usual, reversed-phase functional groups such as CN and phenyl, and by the use of "mini" columns, silica and polymeric columns, the emphasis being reduced on the well-established C-18 columns; (4) high-speed LC; (5) various approaches of direct sample analysis--solvent extraction, automated sample processing, column switching, micro-injections, micellar chromatography, electrochemical detection with photolytic derivation, and the internal surface reversed-phase column of Pinkerton; (6) microbore LC drug analysis; (7) clinical chiral separation; and (8) overall conclusions.