Analysis of potential adulteration in herbal medicines and dietary supplements for the weight control by capillary electrophoresis

Abstract

Four different phytopharmaceutical dosage forms for use in weight control programs were analyzed. Two different ground herbal blends and their correspondent infusions, a capsule and a tincture were investigated for the presence of compounds used as adulterants in these products. A capillary electrophoresis (CE) method was developed and validated. The optimized experimental conditions were: BGE, sodium tetraborate buffer 20 mM, pH 9.2, voltage applied 30 kV, capillary temperature 25 °C, injection sample at 0.5 Psi during 5 s. Ephedrine, norephedrine, caffeine and furosemide were baseline separated in less than 7 min; the migration times were found to be 2.65, 2.90, 3.75 and 6.58 min, respectively. The analysis showed in sample 3 concentrations of 0.45 ± 0.03 mg g-1 (ephedrine), 0.33 ± 0.02 mg g-1 (norephedrine), 1.09 ± 0.41 mg g-1 (caffeine) and 0.80 ± 0.17 mg g-1 (furosemide). Caffeine content in samples 1, 2 and 4 was 0.61 ± 0.06 mg g-1, 15.66 ± 1.05 mg g-1 and 2.27 ± 0.13 mg ml-1, respectively. Linearity was obtained in the concentration range of 1-1000 μg ml-1. Limits of detection (LOD) and quantification (LOQ) were determined as 0.42 μg ml-1 and 1.40 μg ml-1 (ephedrine), 0.47 μg ml-1 and 1.40 μg ml-1 (norephedrine), 0.12 μg ml-1 and 0.48 μg ml-1 (caffeine), 0.22 μg ml-1 and 0.73 μg ml-1 (furosemide). The common constituents of the samples did not interfere with the potential adulterants. Repeatability was better than 0.24% RSD for the retention time and 1.43% for the peak area. Intermediate precision was tested by changing the capillary, the day of operation and the operator, in all the cases the %RSD was better than 3.06. © 2007 Elsevier Ltd. All rights reserved.