An Ultra-High Performance Liquid Chromatography-Electrospray Tandem Mass Spectrometric Method for Screening and Simultaneous Determination of Anorexic, Anxiolytic, Antidepressant, Diuretic, Laxative and Stimulant Drugs in Dietary Supplements Marketed for Weight Loss.

The consumption of dietary supplements is increasing every year all over the world and has been accompanied by an increased frequency of adulteration of these products with synthetic pharmaceuticals. Analytical methods that allow testing for the presence of synthetic drugs in dietary supplements are needed to detect such fraudulent practices. To investigate the adulteration of dietary supplements marketed for weight loss using different commercial appeals, we developed an analytical method using ultra-high-performance liquid chromatography-electrospray tandem mass spectrometry (UHPLC-ESI-MS/MS) for simultaneous determination of 32 drugs, including anorexics, anxiolytics, antidepressants, diuretics, laxatives and stimulants. Separation was accomplished in 19 minutes using a Zorbax SB-C18 column and a gradient elution program with 0.05% formic acid in water/acetonitrile as a mobile phase. Limits of quantification ranged from 0.14 to 3.92 µg L-1, and accuracy ranged from 80.00 to 119.48%. A simple extraction procedure was used in the pretreatment step by dissolving the samples in 100% methanol followed by a 1000 to 10,000-fold dilution in the mobile phase and filtration through a Teflon membrane (0.2 µm). The method was applied to the screening and quantification of the drugs in 108 formulations marketed as food supplements for slimming, weight loss, thermogenics, and supplements for meal replacement. Caffeine and p-synephrine were found as stimulants in 80 samples, listed or not on the label.

Determination of diuretics and laxatives as adulterants in herbal formulations for weight loss.

A new method is described for the determination of the most common diuretic and laxative adulterants found in formulations of anorexics and antidepressants. The method is based on the separation of furosemide, hydrochlorothiazide, chlorthalidone and amiloride (diuretics), phenolphthalein (laxative), amfepramone (anorexic) and fluoxetine and paroxetine (antidepressants) by capillary zone electrophoresis with capacitively coupled contactless conductivity detection. The method showed a precision ranging from 1.9% to 6.9% for a concentration of 25 mg/L, 0.6% to 5.3% for a concentration of 50 mg/L and 1.6% to 6.0% for a concentration of 100 mg/L for all analytes. The accuracy was 99% for amiloride, 102% for chlorthalidone, 101% for hydrochlorothiazide, 101% for furosemide, 94% for phenolphthalein, 105% for fluoxetine, 114% for paroxetine and 117% for amfepramone. The method allowed the drugs to be determined in the formulations at concentrations higher than 5.1 mg/kg for amiloride, 7.7 mg/kg for chlorthalidone, 6.8 mg/kg for hydrochlorothiazide, 10.7 mg/kg for furosemide, 8.4 mg/kg for phenolphthalein, 11.0 mg/kg for fluoxetine, 9.4 mg/kg for paroxetine and 11.0 mg/kg for amfepramone. Three of the 26 analysed herbal formulations were found to be adulterated (not declared on the label) with the diuretic hydrochlorothiazide. Five other samples contained diuretics declared on the label on the formulation. Thus, a total of eight samples, which were marketed as natural products, contained diuretics (declared or not) on the formulation.