17a-Estradiol(3) [HRP]

Matrix effect-free UHPLC-MS/MS method was developed and validated for the determination of cholesterol-lowering lovastatin in food samples represented by Pu-erh tea, oyster mushroom, and red yeast rice. The resulting method was fully validated in terms of intra-day and inter-day precision, accuracy, linearity, range, LOD, LOQ and matrix effects. The matrix effect phenomenon evaluated by comparison of slopes of calibration curves was completely eliminated by solid-phase extraction based on the technique of molecularly imprinted polymers (MIPs). Comparison of elution profiles obtained on the MIP and corresponding control non-imprinted polymer (NIP) showed selectivity of the extraction procedure. In addition, selectivity of the MIP material and the molecularly imprinted solid-phase extraction (MISPE) was also proved by experiments evaluating retention of analytes physico-chemically similar to the target molecule. Extraction recoveries of these analytes represented by estrogen derivatives (estrone, estriol, 17 alpha-ethinylestradiol, and (beta-estradiol) were very low or even null. Synthesis and preparation of the resulting MIP sorbent was characterized by excellent repeatability expressed as RSD 7.7% (n = 9) of extraction recoveries. The determined capacity of the MIP material reaching 375 ng/mg is sufficient for analysis of the evaluated statin in its natural sources. Suitability of the resulting MISPE-UHPLC-MS/MS procedure for real sample analysis was verified by the determination of lovastatin in one dietary supplement based on the red yeast rice with a given amount of the target analyte. Finally, three mushroom and fifteen tea samples obtained in Czech food stores and tearooms were subjected to analysis. Low or null amount of lovastatin was found in these samples. (C) 2017 Elsevier B.V. All rights reserved.

A bundled hollow fiber array (BHF)-liquid-phase microextraction (LPME) approach has been developed for the ultra-high performance liquid chromatography tandem mass spectrometric determination of estrone, 17 beta-estradiol, estriol, and 17 alpha-ethinylestradiol. The BHF was dipped in n-octanol to impregnate only the wall pores of the hollow fibers without deliberate loading of extractant solvent in the lumens, before placing it in the sample for extraction. Parameters influencing extraction efficiency, such as number of bundled hollow fibers, type of extraction and desorption solvent, agitation mode, extraction temperature and duration, and the salting out effect were examined. Under the most favourable experimental conditions, the enrichment factors were between 77 and 137-fold for the target compounds. The developed method offered high sensitivity and reproducibility. Low limits of detection and limits of quantification were achieved, i.e., between 0.251 and 0.440 ng/L, and 0.995 and 1.82 ng/L, respectively. Good intra and inter-day precision were obtained with relative standard deviations (RSDs) of less than 9%. BHF-LPME provided a new perspective on using membrane solvent-supported hollow fiber-mediated LPME. Raman spectroscopy was also introduced in this study to reaffirm that the polypropylene BHF did not play any role in the extraction; only the solvent was responsible. (C) 2017 Elsevier B.V. All rights reserved.