High pressure liquid chromatography in clinical chemistry

Chiral separation and molecular simulation study of six antihistamine agents on a coated cellulose tri-(3,5-dimethylphenycarbamate) column (Chiralcel OD-RH) and its recognition mechanisms

Enantiomeric separation of six antihistamine agents was first systematically investigated on a cellulose-based chiral stationary phase (CSP), that is, cellulose tris-(3,5-dimethyl phenyl carbamate) (Chiralcel OD-RH), under the reversed-phase mode. Orphenadrine, meclizine, terfenadine, dioxopromethazine, and carbinoxamine enantiomers were completely separated under the optimized mobile phase conditions with resolutions of 5.02, 1.93, 1.68, 1.67, and 1.54, respectively. Mequitazine was partially separated with a resolution of 0.77. The influences of type and concentration of buffer salt, the pH of buffer solution, and the type and ratio of organic modifier on the chiral separation were evaluated and optimized. For a better insight into the enantiorecognition mechanisms, molecular docking was carried out via the Autodock software. The lowest binding energy and the optimal conformations of the analytes/CSP complexes were supplied, and the mechanisms of chiral recognition were determined. According to the results, the key interactions for the chiral recognition of these six analytes on CDMPC were π-π interactions, hydrophobic interactions, hydrogen bond interactions, and some special interactions.

Enantiomeric resolution of quinolones on crown ether CSP: Thermodynamics, chiral discrimination mechanism and application in biological samples

The enantiomers of quinolone racemates were resolved using chiral crown ether within 8 min. Thermodynamics data and modeling results were used to determine chiral recognition mechanism. The column used was (+)-Crownpack column (250 mm × 4.6 mm, 5 µm) with three mobile phases I: ACN:Water (80:20) + 10 mM H₂SO₄ and 10 mM CH₃COONH₄, II: ACN:Water (80:20) + 20 mM perchloric acid and III: EtOH:Water (80:20) + 20 mM perchloric acid. The flow rate of the mobile phases was 1.0 mL/min with UV detection at different wavelengths. The ranges of retention (k), separation (α), and resolution (Rs) factors were 1.00-5.40, 1.37-2.00 and 1.50-3.30. The tailing factor was 1.o for all peaks with 900-2325 as the number of theoretical plates were 8.0-10.0 and 32.4-22.1 µg. The difference in enthalpy, entropy and free energy varied in the range of -0.350 to -0.024, 18.74 × 10^-4 to 3.94 × 10^-4 and -0.918 to -0.143, respectively. The thermodynamic and docking results showed chiral discrimination due to physical forces of amnio group cations penetration into the chiral cavity of the chiral selector following hydrogen bindings. The binding energy of S-enantiomers was higher than R-enantiomers; confirming stronger binding of S-enantiomers with CSP than R-enantiomers. The described chiral-HPLC method was used for the analysis of the quinolone enantiomers in urine samples and the results were quite satisfactory. Therefore, the reported method may be used for the enantiomeric separation of quinolone enantiomers in urine samples.

Separation, quantification and identification of non-volatile organic acids in body fluids by gas chromatography

The present paper concentrates on the analysis of non-volatile organic acids in physiological fluids. The solvent extraction and DEAE-Sephadex extraction of organic acids, respectively, seem to be the most widely used methods for isolation of this group of compounds from the biological matrix. Gas chromatography-mass spectrometry (GC/MS) is the preferred method for the separation, quantification and identification. In three tables organic acids are divided into the classes according to a functional group, a survey of alkylation methods is given and retention indices of common urinary organic acids on various GC columns are summarized.

Mycolic acid analysis by high-performance liquid chromatography for identification of Mycobacterium species

Mycobacterium tuberculosis is the etiologic agent of tuberculosis and can be accurately detected by laboratories using commercial genetic tests. Nontuberculosis mycobacteria (NTM) causing other mycobacterioses can be difficult to identify. The identification processes are confounded by an increasing diversity of newly characterized NTM species. The ubiquitous nature of NTM, combined with their potential to be opportunistic pathogens in immunocompromised as well as nonimmunodeficient patients, further complicates the problem of their identification. Since clinical case management varies depending on the etiologic agent, laboratories must identify the species in a timely manner. However, only a few identification methods can detect the species diversity within the Mycobacterium genus. Over the last decade, high-performance liquid chromatography analysis of the mycolic acids has become an accepted method for identification of mycobacteria. In this review, we assess its development and usefulness as an identification technique for Mycobacterium species.

A simple, optimised and rapid assay for urinary free catecholamines by HPLC with electrochemical detection

A rapid method is described for the determination of urinary free catecholamines by HPLC with electrochemical detection. Optimised and equilibrium assay conditions are assessed for sample preparation, separation and detection. Catecholamine stability is maintained during the assay procedure by the addition of a combined reducing agent. Variability in recovery between aqueous standards and urine samples is minimised by dilution of samples with a concentrated Tris buffer solution. Ethyl acetate washing of an acid eluate is performed after and not before an alumina adsorption step in order to make the procedure as simple and rapid as possible. The method is evaluated and has thus far identified two cases of phaeochromocytoma and one case of neuroblastoma.