Hwang Eui Cho

Separation and determination of polyethylene glycol fatty acid esters in cosmetics by a reversed-phase HPLC/ELSD

A comprehensive analytical method was established for the separation of polyethylene glycol (PEG) stearates according to the distribution of ethylene oxide (EO) and subsequent determination of the surfactants in cosmetic samples by using a high-performance liquid chromatography-evaporative light scattering detection. Separation of the PEG stearates comprising approximately up to 82 EO adducts was performed on a reversed-phase YMC-Pack C(8) column using water-acetonitrile gradient elution. The PEG oligomers were separated in order of the increasing number of EO adducts. Quantitation of the PEG fatty acid esters, which was separated as single peak per each component, was performed by chromatography on a reversed-phase Wakosil 10 C(18) column using water-methanol gradient elution. The standard curve to quantify the PEG stearates was constructed by the log-log plot, which showed good linearity with the correlation coefficients (R(2)) 0.998 and more. Working range, repeatability, limit of detection and recovery were acceptable for analysis of the surfactants in cosmetic products. The analytical methods were applied to characterize the PEG stearates according to the EO distributions, then to quantify the surfactants in cosmetic products.

Determination of Flavonoid Glycosides, Polymethoxyflavones, and Coumarins in Herbal Drugs of Citrus and Poncirus Fruits by High Performance Liquid Chromatography–Electrospray Ionization/Tandem Mass Spectrometry

A high-performance liquid chromatography–electrospray ionization–tandem mass spectrometry method was developed and validated for the determination of flavonoid glycosides, polymethoxyflavones, and coumarins in herbal medicines of Citrus fruits and peels and Poncirus fruits. The analytes were rutin, narirutin, naringin, hesperidin, neohesperidin, neoponcirin, poncirin, naringenin, sinensetin, isosinensetin, nobiletin, heptamethoxyflavone, tangeretin, imperatorin, phellopterin, and isoimperatorin, and, together with puerarin (the internal standard), were separated in short run time using a gradient flow of acetonitrile and 0.1% formic acid. Mass spectrometry detection was performed in the multiple reaction monitoring mode. Ion detection was operated alternately between negative and positive ion modes in a single injection. The main fragmentation characteristics of the analytes were investigated to discriminate between isomeric pairs. Validation of the analytical method showed linearity, r > 0.999; accuracy, 96.2 to 103.4%; and precision, relative standard deviation <4.2%. The method was employed to determine these compounds in the following herbal drugs: Citri Unshius Pericarpium, Citri Unshius Pericarpium Immaturus, Ponciri Fructus Immaturus, Aurantii Fructus Immaturus, and Aurantii Fructus. The analytical results showed that there were significant differences between different varieties, different herbal origins, and production areas. This study demonstrated that this method may be used to monitor quality control of the herbal drugs and perform chemotaxonomic investigations.

Development of a liquid chromatography-tandem mass spectrometry method for the determination of Grayanotoxins in rat blood and its application to toxicokinetic study.

A sensitive and specific high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the determination of Grayanotoxin I (GTX I) and Grayanotoxin III (GTX III) in rat whole blood. Grayanotoxins (GTXs) and clindamycin as internal standard (IS) were extracted from rat blood via solid-phase extraction using PEP solid-phase extraction cartridges. Chromatographic separation of the analytes was achieved on a Kinetex C18 (100 × 2.1 mm, 2.6 µm) reversed-phase column using a gradient elution with the mobile phase of 1% acetic acid in water and methanol at a flow rate of 0.2 mL/min. Electrospray ionization mass spectrometry was operated in the positive ion mode with multiple reaction monitoring. The calibration curves obtained were linear over the concentration range of 1-100 ng/mL with a lower limit of quantification of 1 ng/mL for GTXs. The relative standard deviation of intra-day and inter-day precision was below 6.8% and accuracy ranged from 94.8 to 106.6%. The analytes were stable in the stability studies. The validated method was successfully applied to the quantification and toxicokinetic study of GTXs in rats for the first time after oral administration of 11.52 mg/kg mad honey and 0.35 mg/kg GTX III, respectively.