Antonio Sanz

Simultaneous determination of doxorubicin, daunorubicin, and idarubicin by capillary electrophoresis with laser-induced fluorescence detection.

The separation and simultaneous determination of doxorubicin, daunorubicin and ida‐rubicin was investigated using capillary electrophoresis with laser‐induced fluorescence detection. Because the three anthracycline antibiotics were similar in structure and mass, careful manipulation of the electroosmotic flow and electrophoretic mobilities was required. A buffer consisting of 100 mM borate, adjusted to pH 9.5, containing 30% acetonitrile was found to provide a very efficient and stable electrophoretic system for the analysis of the three anthracyclines. The method was applied to the determination of three anthracyclines in serum samples. Responses were linear in the range of 10 — 500 ng·mL−1 and the detection limits were lower than 0.9 ng·mL−1.

Flow-injection chemiluminometric determination of ascorbic acid based on its sensitized photooxidation

The chemiluminescent reaction, in alkaline solution, of lucigenin with the products from the photooxidation of ascorbic acid sensitized by toluidine blue has been studied. A flow-injection configuration is proposed for the determination of ascorbic acid over a concentration range of 1 × 10−9 −3 × 10−4 M with a throughput of 80 samples/h. The method has been used for the simple and rapid determination of ascorbic acid in pharmaceuticals, fruit juices, soft drinks and blood serum.

Successive determination of thiamine and ascorbic acid in pharmaceuticals by flow injection analysis.

A simple and rapid fluorimetric method for the determination of mixtures of thiamine and ascorbic acid is proposed. The procedure is based on the oxidation with mercury(II) of the B1 and C vitamins to form thiochrome (TC) and quinoxaline derivate, respectively. Both reaction products exhibit fluorescence at the same wavelengths (lambdaex = 356 and lambdaem = 440 nm). The procedure is optimised in a flow injection (FI) system and applied with excellent results in the determination of B1 and C vitamins in commercial pharmaceutical preparations. The calibration graphs were linear over the range 2-100 microg ml(-1) for thiamine and 5-100 microg ml(-1) for ascorbic acid. The throughput was 25 samples per hour.

Flow-injection extraction-spectrophotometric method for the determination of ranitidine in pharmaceutical preparations

The spectrophotometric determination of trace amounts of ranitidine was carried out by liquid-liquid extraction using bromothymol blue with a flow system. The determination of ranitidine in the range of 1 x 10(-5) - 1 x 10(-4) mol l(-1) was possible with a sampling frequency of 40 samples h(-1). The method was satisfactorily applied to the determination of ranitidine in pharmaceutical preparations and the recovery was quantitative and no interferences from excipients were observed.

Determination of riboflavin, flavin mononucleotide and flavin adenine dinucleotide in biological tissues by capillary zone electrophoresis and laser‐induced fluorescence detection

The separation of riboflavin, flavin mononucleotide and flavin adenine dinucleotide was investigated by capillary zone electrophoresis using laser‐induced fluorescence detection. In the systematic approach developed, the differential electrophoretic mobilities were first maximized by adjusting the pH. Increasing the buffer concentration improved the separation at the expense of migration times. A buffer consisting of 50 mM phosphate adjusted to pH 8.5 was found to provide a very efficient and stable electrophoretic system. Responses were linear within the range 0.1—100 μmol L−1, and the detection limits of B2 vitamers were 0.23 nmol L−1 or less. The method was successfully applied to a variety of biological tissues from different animals.

Separation and simultaneous determination of quinolone antibiotics by capillary zone electrophoresis

SummaryThe potential of capillary zone electrophoresis has been investigated for the separation and quantitative determination of some quinolone antibiotics. The influence of different conditions, such as the nature and concentration of the electrophoretic electrolyte, on migration time, peak symmetry, efficiency and resolution was studied. A buffer consisting of 100mm HEPES adjusted to pH 8.5 containing 10% (v/v) acetonitrile was found to furnish a very efficient and stable electrophoretic system for the separation of exoxacin, ciprofloxacin, ofloxacin, oxolinic acid, nalidixic acid and pipemedic acid. A linear relationship between concentration and peak area for each compound was obtained in the concentration range 0.25–40 μg mL−1; detection limits were approximately 0.25 ng mL−1. It was demonstrated that the method can be used for the simultaneous determination of these six antibiotics in serum and urine samples.

Simultaneous determination of diquat and paraquat residues in various matrices by capillary zone electrophoresis with diode array detection

SummaryThe separation of diquat and paraquat by CZE has been investigated. The addition of acetonitrile (10 %, v/v) to a phosphate buffer (100 mM, pH 4.0) is necessary for effective separation of both herbicides at an optimum applied voltage of around 12 kV; the current and migration times were stable and reproducible under these conditions. The method was validated for linearity and reproducibility. The detection level calculated for diquat and paraquat was 30 and 40 nM, respectively in the injection solution. By use of stacking, these detection levels were improved by a factor of 120. The method is suitable for the determination both herbicides in samples such as herbicidal formulations, water, soil, potatoes, urine and serum. Photodiode-array detection permitted the rapid identification of both compounds.

Sensitive method for the determination of ambroxol in body fluids by capillary electrophoresis and fluorescence detection

A sensitive and rapid capillary electrophoretic method combined with laser-induced fluorescence detection has been developed for the determination of ambroxol. Samples were derivatized with 5 x 10(-4) M fluorescein isothiocyanate. A linear relationship between concentration and peak area was obtained in the concentration range 0.008-42 microg ml(-1) with a correlation coefficient of 0.9999. The applicability of the method to serum and urine samples was demonstrated. The method is also useful for the determination of ambroxol in pharmaceutical preparations.

Determination of flufenamic, meclofenamic and mefenamic acids by capillary electrophoresis using β-cyclodextrin

The possibility of separating flufenamic, meclofenamic and mefenamic acids by capillary electrophoresis was studied. The best approach involved combining a suitable pH of the carrier electrolyte (pH 12.0) with the host-guest complexation effects of beta-cyclodextrin. A running buffer consisting of 30 mM phosphate buffer (pH 12.0), 2 mM beta-CD and 10% (v/v) acetonitrile was found to provide a very efficient and stable electrophoresis system for the analysis of fenamic acids by capillary zone electrophoresis. Responses were linear from 0.4 to 40 microg/ml for the three drugs with detection limits of about 0.3 ng/ml. Intra- and inter-day precision values of about 1-2% R.S.D. (n = 11) and 3-4% R.S.D. (n = 30), respectively, were obtained. The method is highly robust and no breakdowns of the current or capillary blockings were observed for several weeks. The general applicability of this rapid CZE procedure (migration times less than 12 min) is demonstrated for several practical samples, including serum, urine and pharmaceuticals.

Flow extraction spectrophotometric method for the determination of diclofenac sodium in pharmaceutical preparations

The spectrophotometric determination of trace amounts of diclofenac was carried out by liquid-liquid extraction using acridine yellow with a flow system. The determination of diclofenac sodium in the range of 3-80 micrograms ml-1 was possible with a sampling frequency of 40 samples h-1. The method was satisfactorily applied to the determination of diclofenac in pharmaceutical preparations.