Simultaneous analysis of antioxidants and preservatives in cosmetics by supercritical fluid extraction combined with liquid chromatography-mass spectrometry

Counterfeit homeopathic medicinal products: syrups. A simple and rapid LC-ESI-MS method to detect preservatives not declared in label

A rapid and simple LC-ESI-MS method for the simultaneous detection and quantitation of six preservatives in homeopathic syrups has been developed. Counterfeit homeopathic syrups are suspected to contain preservatives that are not declared in label. For this reason a method to ascertain the absence of sorbic and benzoic acids, methyl-, ethyl-, propyl- and butyl-parabens, as the most frequently utilised preservatives, has been developed. Analytes were eluted with a linear gradient of acetonitrile-5mM ammonium acetate in 12 min using 2,4-dichlorobenzylalchol as Internal Standard. The HPLC separation was performed on an Eclipse XDB-C18 (2.1 mm x 50 mm-5 microm) column and the ESI-MS detection was performed in negative ion mode. Linearity of the method was studied in the range of 2 pg to 10 ng injected and correlation coefficients r2 > or =0.9992 were obtained. LOD ranged from 0.04 to 0.4 ng mL(-1).

Comparison of reversed-phase liquid chromatography–mass spectrometry with electrospray and atmospheric pressure chemical ionization for analysis of dietary tocopherols

ESI and APCI ionization techniques in both negative and positive ion modes were evaluated for simultaneous LC-MS analysis of the four tocopherol homologues (alpha, beta, gamma and delta). The ESI and APCI ionization of tocopherols in positive ion mode was not efficient and proceeded via two competitive mechanisms, with the formation of protonated pseudo-molecular ions and molecular ions, which adversely influenced the repeatability of MS signal. Ionization in negative ion mode in both ESI and APCI was more efficient as it only produced target deprotonated pseudo-molecular ions. The APCI in negative ion mode showed larger linearity range, lower detection limits and was less sensitive to the differences in chemical structure of analytes and nature of applied solvents than negative ion ESI. Negative ion APCI was, therefore, chosen for the development of LC-MS method for simultaneous determination of the four tocopherols in foods. A baseline separation of the tocopherols was achieved on novel pentafluorophenyl silica-based column Fluophase PFP. The use of methanol-water (95:5, v/v) as a mobile phase was preferable to the use of acetonitrile-water due to considerable gain in MS signal. The limits of quantifications were 9 ng/mL for alpha-tocopherol, 8 ng/mL for beta- and gamma- and 7.5 ng/mL for delta-tocopherol when 2 microL was injected. This method was successfully applied to determination of tocopherols in sunflower oil and milk.

Determination of tocopherols and tocotrienols in cereals by pressurized liquid extraction–liquid chromatography–mass spectrometry

A rapid analytical method including pressurized liquid extraction (PLE) and liquid chromatography-electrospray ionisation-mass spectrometry (LC-ESI-MS) has been developed for the determination of tocopherols and tocotrienols in cereals. The pressurized liquid extraction parameters were optimized in order to maximize the extraction efficiency. The use of methanol as extraction solvent at a temperature of 50 degrees C and a pressure of 110 bar, using one cycle of extraction with a static time of 5 min, provided the best results. A good LC separation was achieved using a C(18) column and a solution of 6.0 mM ammonia in methanol/water (97:3, v/v) as the mobile phase at a flow rate of 0.2 mL min(-1). MS coupling with an ESI interface in the negative ion mode was used as the detection technique. In the present work, it is shown that the addition of a base to the mobile phase is required to enhance the ionization of tocopherols and tocotrienols in negative ion mode electrospray ionization. The applicability of the method to cereal samples was confirmed. The reproducibility of the procedure was good, with relative standard deviations in the 6-10% range. The recoveries of added tocopherols from cereal samples ranged from 91 to 109%.