Micellar electrokinetic capillary chromatography theory based on conventional chromatography.

From the definitions of retention time (tR) and resolution (Rs) in conventional chromatography, two fundamental equations for the retention behaviour and resolution of neutral solutes are derived and proved to be valid in all cases of micellar electrokinetic capillary chromatography (MECC). Two parameters, phase velocity ratio (Pr) and column availability (Aco), are introduced to reveal clearly the relationships and differences between MECC and conventional chromatography. The tR and Rs values may be either positive or negative in MECC. A negative tR indicates that the solute migrates toward the positive electrode and a positive tR toward the negative electrode. Rs > 0 means that the solute with a smaller value of the capacity factor (k') in the pair of solutes reaches the detector first, while Rs < 0 means that the elution order is the opposite. MECC can be classified into eight cases depending on the values of Pr for convenience of discussion. So far, MECC was usually performed in case IV and the resolution was poorer than that in conventional chromatography for given values of theoretical plate number, selectivity and k'. However, a better resolution can be obtained in cases II, VI and VIII when Pr < (1-k')/2. Cases VI, VIII and II are preferable to case IV for high resolution and should be more frequently employed in the future.

[Application of Pirkle-type chiral column to the resolution of enantiomeric drugs: resolution and identification of alpha-naphthyl isocyanate derivatives of alprenolol and some other beta-blockers].

alpha-Naphthyl isocyanate (NI) as a derivatizing agent to separate several beta-blockers was described. This procedure is simple, rapid and gives good resolution. Experiments with NI derivatives of alprenolol showed that the isocyanate group reacted with the amino group on the analyte to form urea under mild conditions and with the hydroxyl group to form carbamate under relatively vigorous conditions. The results also indicated that the derivatized reactions is 1:1 between NT and analytes.

[Studies on the chemical constituents of Fritillaria in Hubei. X. Isolation and identification of alkaloids from Fritillaria ebeiensis var.purpurea G.D.Yu et P.Li].

The bulb of Fritillaria ebeiensis var. purpurea G.D. Yu et P. Li (Liliaceae) are commercially available as the substitute for the principal Chinese traditional medicine "Beimu". This plant is easily cultivated, has high alkaloid content and conspicuous antitussive and expectorant effects. Seven C-nor-D-homo steroidal alkaloids (I-VII) were isolated from the bulb cultivated in Suizhou district, Hubei. I-IV have been identified as the known alkaloids peimine, peiminine, ebeinine and ebeinone on the basis of spectral data and by TLC and mixed mp comparison with authentic samples. The alkaloid VI, C27H43NO2, mp 186-188 degrees C, named ziebeimine, is a new alkaloid isolated from the title plant. The structure of VI has been established as 5 alpha, 14 alpha-cevanine-13, 17-dehydro-3 alpha, 6 beta-diol on the basis of its IR, 1H-NMR, 13C-NMR and mass spectra. The structure of alkaloids V and VII is still under investigation.

[Chemical studies on the constituents of radix Ophiopogonis].

In this paper four compounds isolated from Radix Ophiopogonis are described. Their structures have been identified as beta-sitosterol (I), 6-aldehydo-7-methoxy-isoophiopogonanone B (II), beta-sitosterol-beta-D-glucopyranoside (III) and 1-borneol-beta-D-apisyl-beta-D-glucopyranoside (IV) on the basis of spectral data and hydrolytic reaction.

Separation of sulphonamides and determination of the active ingredients in tablets by micellar electrokinetic capillary chromatography.

The separation and determination of seven sulphonamides and trimethoprim by micellar electrokinetic capillary chromatography were successfully achieved, employing sodium dodecyl sulphate (SDS) as a micellar phase and tetrabutylammonium bromide as additive. The effects of surfactant and modifier concentrations, pH and applied voltage on the retention behaviour of the solutes and the column efficiency were studied. The migration time of sulponamides increase with increasing SDS concentration and decreasing the applied voltage, but varies only slightly with pH. There is an optimum applied voltage at which a higher theoretical plate number is achieved, in contrast to the sulphonamides, the retention behaviour of trimethoprim gave a more obvious response to changes in the experimental conditions. The determination of three active ingredients in tablets was performed using sulphathiazole as an internal standard with good results. The theoretical plate number ranged between 2.0 x 10(5) and 2.8 x 10(5) with a 50-cm capillary.

Determination of 3-methylflavone-8-carboxylic acid, the main metabolite of flavoxate, in human urine by capillary electrophoresis with direct injection.

The effects of tetraalkylammonium salts and sodium dodecyl sulphate on the migration behaviour of human urinary components and other negatively charged or neutral solutes were investigated. The sulphate acted mainly on hydrophobic and positively charged substances, whereas the ammonium salts acted mainly on negatively charged solutes. By choosing the components of the eluent carefully, the free and conjugate forms of 3-methylflavone-8-carboxylic acid (MFA) in human urine, the major metabolites of flavoxate, could be simultaneously determined without pretreatment, using fenprofen as an internal standard. The calibration curve of MFA was linear in the range 1-50 micrograms/ml and the detection limit was 0.2 microgram/ml, which covered the urine levels encountered in pharmacokinetic studies. The intra-day and inter-day precisions of the method, expressed as the relative standard deviation, were less than 2 and 3%, respectively. This method was successfully applied to an excretion study of MFA in eight healthy volunteers, and the results were in agreement with data in the literature obtained by gas chromatography.