Estimation of the breakthrough volume of selected steroids for C-18 solid-phase extraction sorbent using retention data from micro-thin layer chromatography
Institute of Technology and Chemical Engineering, Poznań University of Technology, Poznań, Poland.Journal of Separation Science (Impact Factor: 2.74). 03/2013; 36(6). DOI: 10.1002/jssc.201200917
SPE method is a very popular technique, and is commonly used for the prepurification, concentration, and isolation of different organic compounds from variable matrices. In this work, the optimization of SPE process was carried out. The breakthrough volume of solid sorbents based on octadecylsilane was determined and three methods were compared: (1) calculation one - the breakthrough volume was calculated using retention factor k determined with micro-TLC method, frontal analysis - (2) breakthrough volume was determined as volume of whole elution peak, and (3) breakthrough volume was determined as the center of peak gravity. For calculation method, the k values of key estrogens and progestogens were derived from the micro-TLC experiment reported previously. By combining these three methods, we can point the start of elution, the maximum concentration of analyte in eluate, and the whole eluent volume, which is necessary to achieve an appropriate selectivity and high extraction recovery. Proposed calculation method allows to estimate the beginning of the steroid peak, when the analyte appears in the eluate flowing from the sorbent. Such observation advances the SPE optimization protocol that was described before and was based on the correlation between raw k(SPE) and k(micro-TLC) data.
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ABSTRACT: There have been great concerns about the persistence of steroid hormones in surface water. Since the concentrations of these compounds in water samples are usually at a trace level, the efficient enrichment of steroid hormones is vital for further analysis. In this work, a porous and hydrophobic polymer was synthesized and characterized. The composition of solvent used as porogen in the synthetic process was shown to have an effect on the morphology of the polymer, which was successfully used as a solid-phase extraction sorbent for simultaneously enriching steroid hormones in surface water samples. The recoveries of the steroid hormones on the custom-made polymer ranged from 93.4 to 106.2%, whereas those on commercialized ENVI-18, LC-18, and Oasis HLB ranged from 54.8-104.9, 66-93.6 and 77.2-106%, respectively. Five types of steroid hormones were simultaneously measured using HPLC-UV after they were enriched by the custom-made sorbents. Based on these findings, the SPE-HPLC method was developed. The limits of detection of this method for estriol, estradiol, estrone, androstenedione, progesterone were 0.07, 0.43, 0.61, 0.27 and 0.42 μg/L, respectively, while precision and reproducibility RSDs were below 6.40 and 7.49%, respectively. This article is protected by copyright. All rights reserved.
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ABSTRACT: A reliable multiclass method has been developed and validated for the determination of eight antibiotics from distinct classes (sulfonamides, macrolides, fluoroquinolones, tetracyclines, cephalosporins and dihydrofolate reductase inhibitors) in wastewater – influent and effluent – and surface water from Porto Alegre, Brazil. The pre-concentration and clean-up was conducted with a simple and fast protocol using solid-phase extraction allowing a 100-fold concentration factor. The proposed method was validated by using spiked blank wastewater samples in terms of linearity, repeatability, reproducibility, recovery, matrix effects and limits of detection and quantification. Recovery was obtained in the range of 66–149%. Method limit of quantification ranged between 1.6 and 61.7 ng L−1. Samples (n = 16) were taken from January to August 2011 in one wastewater treatment plant, which uses conventional biological treatment. Sulfamethoxazole and trimethoprim show higher concentration, ranging from >10 to <6500 ng L−1, whereas erythromycin presented the lower amount. Differences between influent and effluent profiles were discussed. Surface water samples (n = 8) were collected in Arroio Diluvio, in four sampling points, in February 2012. From the eight antibiotics analysed, five were detected: sulfamethoxazole, trimethoprim, azythromicyn, ciprofloxacin and norfloxacin, in a concentration range of 376–572 ng L−1, 27–94 ng L−1, 24–40 ng L−1, 16–66ng L−1 and 30–54 ng L−1, respectively.
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ABSTRACT: The traditional direct bioautography workflow was substantially altered to yield narrow, sharp-bounded effective zones. For the first time, microorganisms quantitatively detected the single effective compounds in complex samples, separated in parallel on a planar chromatogram. This novel effect-directed workflow was demonstrated and optimized for the discovery of endocrine disrupting compounds (EDCs) reacting with the human estrogen receptor down to the femtogram-per-zone range, like 250fg/zone for 17β-estradiol (E2). For application volumes of up to 0.5mL, estrogen-effective compounds could directly be detected in complex samples at the ultratrace level (ng/kg-range). Sharp-bounded, estrogen-effective zones discovered were further characterized by direct elution into the mass spectrometer. HPTLC-ESI-MS mass spectra of (xeno)estrogens were shown for the first time. Owed to the substantially improved zone resolution, compound assignment was reliable and a comparison of the receptor affinities was conducted for six (xeno)estrogens. Also, long-term cell cultivation of the genetically modified yeast was demonstrated on the HPTLC plate. The optimized HPTLC-pYES workflow was proven for real food samples, exemplarily shown for beer. The general applicability of generating sharp-bounded zones was successfully proven by transfer of the fundamentally improved workflow to the Bacillus subtilis bioassay used for discovery of antibiotics in plant extracts. This new era of quantitative direct bioautography in combination with mass spectrometry will accelerate the scientific understanding in a wide application field via the streamlined access to fast and reliable information on effective components in complex samples.
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