Method for the simplified analysis of deproteinized plasma and urinary isoproterenol by high-performance liquid chromatography

Post-column reactors for sensitive and selective detection in high-performance liquid chromatography: categorization and applications

The increasing interest in the rapid trace analysis of large series of biomedical samples using column liquid chromatographic techniques requires the use of well balanced combinations of sample pretreatment, separation and detection techniques. In such work, selectivity, sensitivity and reproducibility are the key parameters. The application of automated or semi-automated on-line pre-column technology and/or post-column reaction detection are excellent ways to meet these requirements. A critical review is presented of the theoretical background of on-line post-column reactors with emphasis on their categorization, viz., open-tubular, packed-bed, segmented-stream and hollow-fibre membrane reactors. The evaluation of these reactor systems is performed by discussing selected applications of, for instance, systems based on electrochemical and redox, hydrolytic, photochemical, ion-pairing, true chemical derivatization, peroxyoxalate chemiluminescence and solid-phase reactions. As automation is becoming even more important, a number of labelling procedures, which can be performed in an on-line pre-column mode, are briefly discussed and a comparison is made between the potential of on-line pre- and post-column procedures.

High-performance liquid chromatography of plasma catecholamines using 1,2-diphenylethylenediamine as precolumn fluorescence derivatization reagent

A simple, rapid and highly sensitive method for the determination of catecholamines (norepinephrine, epinephrine and dopamine) in human plasma is described which employs high-performance liquid chromatography with fluorescence detection. After cation-exchange chromatography on a Toyopak SP cartridge, the catecholamines and isoproterenol (internal standard) in 500 microliters of plasma are converted into the corresponding fluorescent compounds by reaction with 1,2-diphenylethylenediamine in aqueous acetonitrile. These compounds are separated within 8 min on a reversed-phase column, TSK-gel ODS-120T, with isocratic elution using a mixture of water, methanol and acetonitrile containing a Tris--hydrochloric acid buffer (pH 7.0). The detection limit for each catecholamine is ca. 2 fmol in a 100-microliters injection volume. N-Methyldopamine can also be used as internal standard.

Drug level monitoring of antiasthmatic drugs

In general assays pertaining to drug level monitoring (DLM) of antiasthmatic agents (except theophylline), published during the period 1978-1983, used mostly high-performance liquid chromatographic (HPLC) methodology (approximately 45%) with mass spectrometric (MS) based assays in second place (approximately 30%) followed by immunochemical techniques (approximately 25%). Whenever nanogram or subnanogram antiasthmatic drug concentrations had to be measured such as for the adrenergic stimulants or for the prophylactic agents, then both HPLC-and MS-based methodologies were employed with about equal frequency. The trend in DLM for the phosphodiesterase inhibitor class (theophyllines) seemed to be shifting towards the HPLC methodologies. In part, this was justified by the need for improved selectivity. This criterion appears to have been better satisfied by HPLC, but for all practical purposes the immunochemical methods are and will probably continue to prevail in the clinical laboratory setting until HPLC procedures become truly automated. In the case of DLM of corticosteroids used for the asthmatic, the situation is in our opinion still unclear. This is caused by the presence of endogenous corticosteroids and metabolites, the levels of which in man are known to vary. The current immunochemical procedures offer a facile but less selective option. The future for selective routine corticosteroid assays may well be in HPLC or gas chromatography coupled with MS.

Determination of d-isoproterenol sulphate by high-performance liquid chromatography with amperometric detection

The application of reversed-phase high-performance liquid chromatography (HPLC) to the determination of isoproterenol sulphate in human plasma and urine was investigated. Sulphoconjugation of the inactive isomer of isoproterenol was chosen as an experimental model to study individual variations in the rate of sulphation of phenols in man. This approach allowed the ingestion of relatively large amounts of drug and detection of the conjugated material after acid hydrolysis, using alumina clean-up and HPLC with amperometric detection. This method was found to be rapid, sensitive, precise and suited to pharmacokinetic studies in man.