Liquid chromatography-mass spectrometry with on-line solid-phase extraction by a restricted-access C18 precolumn for direct plasma and urine injection.

In this paper, the on-line coupling of solid-phase extraction, based on a restricted-access support with liquid chromatography-mass spectrometry (LC-MS), for the analysis of biological samples is described. The system was tested with cortisol and prednisolone for plasma analysis and arachidonic acid for urine analysis. A precolumn packed with a 25-micron C18 alkyl-diol support is used for direct plasma or urine injection. Using column-switching techniques, the analytes enriched on the precolumn are eluted to the analytical column without transfer loss. An on-line heart-cut technique was employed and only the analyte-containing fraction eluting from the LC column is directed to the MS to protect the LC-MS interface and ion-source from contamination. The whole system is operated in a parallel mode, that is, sample pre-treatment and LC-MS analysis are performed simultaneously to provide the shortest possible analysis time. The only off-line sample pre-treatment step required was centrifugation to remove particulate matter. With the fully automated system, total analysis times of 5 and 9.5 min were achieved for cortisol in serum and arachidonic acid in urine, respectively. Cortisol and related compounds were quantitatively recovered from plasma with a detection limit for prednisolone (direct injection of 100 microliters on restricted-access precolumn) of 2 ng/ml.

Identification of 4-hydroxyandrost-4-ene-3,17-dione metabolites in prostatic cancer patients by liquid chromatography-mass spectrometry.

Liquid chromatography with thermospray mass spectrometry has proved to be an invaluable technique for the study of metabolic degradation of xenobiotics in complex biological fluids. This paper describes the detection of 4-hydroxyandrost-4-ene-3,17-dione and its metabolites in urinary extracts from prostatic cancer patients. Several metabolites were detected including 4 beta,5 alpha-dihydroxyandrostan-3,17-dione, 3,17-dihydroxyandrostan-4-ones and 3 alpha-hydroxy-5 beta-androstan-4,17-dione.

On-line continuous-flow dialysis thermospray tandem mass spectrometry for quantitative screening of drugs in plasma: rogletimide.

The application of a continuous-flow dialysis system, consisting of a membrane dialyser and a trace enrichment column, in on-line combination with tandem mass spectrometry via a thermospray interface is described. The method is applied to the quantitation of drugs in complex biological matrices containing macromolecular interferences. The potential of the method is demonstrated by the quantitative analysis of the anti-cancer drug rogletimide in the plasma of patients after treatment.

On-line liquid chromatography/thermospray mass spectrometry in the analysis of oligosaccharides.

The analysis of intact neutral oligosaccharides by on-line liquid chromatography/thermospray mass spectrometry is described. Molecular-weight information on oligomers up to a degree of polymerization of 10 is obtained using an aqueous mobile phase containing 10(-4) mol/L sodium acetate, which was found to be compatible with thermospray interfacing and ionization. Ions due to sodiated and disodiated oligosaccharides are observed under these conditions without fragmentation. The aqueous 10(-4) mol/L sodium acetate mobile phase is demonstrated to be applicable in the separation of mixtures of oligosaccharides on a reversed-phase octadecyl-modified silica column.

Thermospray liquid chromatography/mass spectrometry of polar beta-blocking drugs: preliminary results.

The use of thermospray liquid chromatography for the screening of polar beta-blocking drugs is evaluated. The influence of instrumental parameters on the fragmentation pattern of labetalol, acebutolol, diacetolol, sotalol and atenolol is described. A short biomedical application is presented.

Liquid chromatography-thermospray tandem mass spectrometry for identification of a heptabarbital metabolite and sample work-up artefacts.

An unknown heptabarbital metabolite, observed in the liquid chromatogram of rat plasma and urine samples after administration of heptabarbital, was identified by liquid chromatography-thermospray tandem mass spectrometry. By applying the parent scan mode for screening and the daughter scan mode for structure elucidation, the metabolite was determined to be 5-ethyl-5-(1'-, 3'- or 6'-cycloheptadienyl)barbituric acid. It was demonstrated that artefact formation occurred when hydrochloric acid was used for conjugate hydrolysis in the sample clean-up. Identification of the artefacts was achieved by the same method. Confirmation of the structures of the metabolite and the artefacts was obtained by gas chromatography-electron impact mass spectrometry.

Structure elucidation of mitomycin C metabolites. I. The applicability of various mass spectrometric techniques in metabolic studies on mitomycin C.

Knowledge of the metabolism of the anticancer drug mitomycin C (MMC) is necessary in order to optimize the administration schemes of this drug. The present study concentrates on the metabolism of MMC in liver homogenates. Various mass spectrometric methods have been investigated for their usefulness in the metabolic studies on MMC by comparing the mass spectral data. Data from electron impact, direct probe chemical ionization, direct chemical ionization, field desorption and thermospray ionization have been obtained. One of the soft ionization methods, i.e. direct chemical ionization, has been applied to the detection of MMC in a spiked piglet liver sample. It appears to be necessary to enhance the selectivity of the method by using tandem mass spectrometry, owing to the high biological background.

Automated analysis of mitomycin C in body fluids by high-performance liquid chromatography with on-line sample pre-treatment.

A fully automated liquid chromatographic system for the bioanalysis of mitomycin C has been described. The isolation of the analyte from the biological matrix (plasma, ascites and urine) is performed using a continuous-flow system equipped with a dialysis membrane in order to remove proteins. The samples are concentrated on a reversed-phase pre-column and subsequently introduced on to a reversed-phase analytical column by applying column-switching techniques. The drug is detected by absorbance measurements at 360 nm. Using the described system up to 100 samples a day can be analysed with determination limits of the order of 1 ng/ml, with a linear dynamic range of at least three decades for plasma and urine samples. The procedure was applied to pharmacokinetic studies of ovarian cancer patients treated intraperitoneally with mitomycin C.