The role of the acquisition methods in the analysis of natural and synthetic steroids and cholic acids by gas chromatography-mass spectrometry.

An exhaustive GC-MS acquisition study was performed, for the simultaneous analysis of natural and synthetic steroids and cholic acids (in order to insert them into the last tierce of our multiresidue analysis system), such as androsterone, ß-estradiol, transdehydroandro-sterone, transdehyroandrosterone, mestranol, dihydrotestosterone, ethinylestradiol, testosterone, norethisterone, estriol, 4-androstene-3,17-dione, gestodene, levonorgestrel, etonogestrel, coprostanol, progesterone, cholesterol, medroxyprogesterone-acetate, lithocholic acid, stigmasterol, cholic acid, chenodeoxycholic acid, ß-sitosterol, ursodeoxycholic acid, 3-hydroxy-7-ketocholic acid and dehydrocholic acid, in total 26 compounds. As novelties to the field, for the trimethylsilyl (TMS) oxime ether/ester derivatives of steroids and cholic acids, at first, a tandem mass spectrometric (MS/MS), multiple reaction monitoring (MRM) type acquisition method has been developed in a single run; also for the first time, the three acquisition techniques, the full scan (FS), the selective ion monitoring (SIM), in our case the multiple ion monitoring (MIM) and the currently optimized MRM methods, have been compared; all three, in parallel, under strictly the same derivatization/instrumental conditions, both in matrix free solutions and municipal wastewater from two Hungarian wastewater treatment plants (WWTPs). Critical evaluation of the three acquisition protocols was collated on their analytical performances and validated under the same conditions. The data of six point calibration curves for FS, MIM and MRM methods, showed that both R² (0.9995, 0.9858, 0.9975) and RSD (5.3, 5.8, 5.0), for two parallel derivatizations, each injected three times, proved to be independent of the acquisition processes. Whereas, for the method limit of quantification (LOQ) and the instrument limit of quantification (ILQ) values showed considerable differences. LOQ data, were decreasing in the FS, MIM, MRM line (expressed in ng/L), for all steroids and cholic acids. The same trend was determined in terms of the ILQ values. The practical utility of the optimized acquisition techniques was confirmed by the quantitation of the steroids and cholic acids contents of wastewater samples. Results confirmed the importance of the MRM acquisition method, even in comparison to the MIM one: with particular interest in selected cases: avoiding the extreme overestimation of the ß-estradiol (156-1325%) and that of the ethinylestradiol (582-831%) concentrations in the wastewater samples.

Derivatization and fragmentation pattern analysis of natural and synthetic steroids, as their trimethylsilyl (oxime) ether derivatives by gas chromatography mass spectrometry: analysis of dissolved steroids in wastewater samples.

This paper reports the extension of our multiresidue analysis (MA) procedure with 18 natural and synthetic steroids; permitting the identification and quantification, in total of 81 pollutants from one solution, by a single injection, as their trimethylsilyl (TMS)-oxime ether/ester derivatives, by gas chromatography-mass spectrometry (GC-MS), within 31 min. As a novelty to the field, basic researches, such as fragmentation pattern analysis and derivatization optimization studies were performed for androsterone, transdehydroandrosterone, transandrosterone, mestranol, dihydrotestosterone, ethinylestradiol, testosterone, norethisterone, estriol, 4-androstene-3,17-dione, gestodene, levonorgestrel, etonogestrel, coprostanol, progesterone, cholesterol, medroxy-progesterone-acetate, stigmasterol and ß-sitosterol. Results confirmed that (i) the TMS oxime-ether derivatives of the keto steroids provide from 1.40 times (gestodene) up to 4.25 times (norethisterone) higher responses compared to their TMS-ether ones, and (ii) the distribution of syn/anti oximes is characteristic to the ketosteroid species examined. Based on our optimized mass fragmentation, solid phase extraction (SPE) and derivatization studies separations have been performed in the total ion current (TIC) mode, identification and quantification of compounds have been carried out on the basis of their selective fragment ions. Responses, obtained with derivatized standards proved to be linear (hydroxysteroids), or have been calculated from calibration curves (ketosteroids) in the range of 1.88-750ng/L levels. Limit of quantitation (LOQ) values varied between 1.88ng/L and 37.5ng/L concentrations. The most important practical messages of this work are the high androsterone (0.744-4.28µg/L), transandrosterone (0.138-4.00µg/L), coprostanol (2.11-302µg/L), cholesterol (0.308-41µg/L), stigmasterol (1.21-8.40µg/L) and ß-sitosterol (1.12-11.0µg/L) contents of influent wastewaters. ß-Estradiol (100ng/L) and estriol (54ng/L) were found in one influent sample, only. Reproducibilities, characterized with the relative standard deviation percentages (RSD%) of measurements, varied between 1.73 RSD% (ß-estradiol) and 5.4 RSD% (stigmasterol), with an average of 4.82 RSD%.

The role of the acquisition methods in the analysis of the non-steroidal anti-inflammatory drugs in Danube River by gas chromatography-mass spectrometry.

In this paper authors describe a GC-MS acquisition study, relating to the most common, non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, naproxen, ketoprofen and diclofenac. As novelties to the field, for the trimethylsilyl (TMS) oxime ester derivatives of NSAIDs, at first, a tandem mass spectrometric (MS/MS) acquisition method has been developed, and, also for the first time, the three acquisition techniques, the full scan (FS), the selective ion monitoring (SIM) and the currently optimized MS/MS ones, have been compared: all three in parallel, under strictly the same derivatization/instrumental conditions, both from model solutions and from the Danube River samples. Critical evaluation of the three acquisition protocols was collated on their analytical performances and validated with the same characteristics like the six point calibration curve, the relative standard deviation percentages (RSD%) of parallel tests, the limit of quantitation (LOQ) and the instrumental limit of quantitation (ILQ) values. Data of six point calibration (r(2)>or=0.997) and RSD% (average: 5.8 RSD%) values proved to be independent on the acquisition methods, while, LOQ and ILQ values furnished considerable differences. Decreasing LOQ data, (expressed in ng/L concentrations) were obtained in the FS, SIM, MS/MS line for ibuprofen (1.0, 0.43, 0.41), naproxen (1.1, 1.0, 0.42), ketoprofen (2.6, 1.0, 0.49) and diclofenac (1.4, 0.41, 0.21), respectively. The same trend was determined in terms of the ILQ values. The practical utility of the optimized MS/MS technique was confirmed by the quantitation of the NSAID contents of the Danube River samples, determined by all three acquisition techniques. Results obtained confirmed the primary importance of the MS/MS acquisition method, even in comparison to the SIM one: avoiding the extreme overestimation of the ibuprofen (approximately 100%) and ketoprofen (approximately 400%) concentrations in the Danube River samples.

Multiresidue analysis of pollutants as their trimethylsilyl derivatives, by gas chromatography-mass spectrometry.

This paper reports a multiresidue analysis procedure which permits the identification and quantification of sixty-three water-soluble pollutants. Subsequent to their solid-phase extraction (SPE) enrichment, analyses of species have been carried out from one solution, by a single injection, as their trimethylsilyl-oxime ether/ester derivatives, by gas chromatography-mass spectrometry, within 31min. Based on our optimized extraction, derivatization and mass fragmentation studies separation have been performed in the total ion current mode, identification and quantification of compounds have been carried out on the basis of their selective fragment ions. Including various pharmaceuticals, benzoic acid, its substituted species, different aromatic carboxylic acids, cholic acids, unsaturated and saturated fatty acids, aliphatic dicarboxylic acids, as well as synthetic pollutants of various origins (2,4-di-tert-butylphenol, different phthalates). Standard compounds were added to 500 mL effluent wastewater samples, at three concentrations (1-5 microg/L, 5-10 microg/L and 10-20 microg/L). Recoveries, using the Waters Oasis cartridges performing extractions at pH 2, pH 4 and pH 7 proved to be the optimum at pH 4 (average recoveries (94.5%), except for cholesterol (10%), paracetamol (18%) and 2,5-dihydroxybenzoic acid (25%). Carbamazepine could be recovered at pH 7, only. Responses, obtained with derivatized standards proved to be linear in the range of 4-80 microg/L levels. Limit of quantitation values varied between 0.92 ng/L (4-hydroxyphenylacetic acid) and 600 ng/L (dehydrocholic acid) concentrations. One of the most important messages of this work is the confirmation of the origin of blank values. It was shown that contaminants, mainly 2,4-di-tert-butylphenol, different phthalates and fatty acids, are sourced both from the reagents and mainly from the SPE procedure, independent on the cartridge applied. Reproducibilities, characterized with the relative standard deviations (RSDs) of measurements, varied between 0.71% and 10%, with an average of 4.38% RSD. The practical utility of the method was shown by the identification and quantification of the pollutant contents of Hungarian influent and effluent wastewaters (for six consecutive months and that of the Danube River for 2 months).

Gas chromatography-mass spectrometry of the trimethylsilyl (oxime) ether/ester derivatives of cholic acids: their presence in the aquatic environment.

This paper presents a derivatization, mass fragmentation study relating to the most common six cholic acids, such as cholic, lithocholic, chenodeoxycholic, ursodeoxycholic, 3-hydroxy,7-ketocholanic and dehydrocholic acids, identified and quantified as pollutants in the aquatic environment at the first time. Derivatizations have been performed with the two-step process (1: oximation, 2: silylation) varying the time and temperature of both reactions. Optimum responses have been obtained after 30 min oximation with hydroxylamine.HCl and 90 min silylation with hexamethyldisilazane and trifluoroacetic acid at 70 degrees C. Fragmentation patterns of the trimethylsilyl (oxime) ether/ester derivatives of all six cholic acids provided the theoretically expected, fully derivatized compounds. Reproducibility/linearity of derivatives calculated on the basis of the corresponding selective fragment ions, characterized by the relative standard deviation percentages of measurements, proved to be < or =4.9 (RSD%). The practical utility of the method was shown by the identification and quantification of cholic acids as pollutants in the aquatic environment. Subsequently to a solid phase extraction study varying the pH of extractions (pH 2, pH 4 and pH 7), applying the OASIS cartridges, it has been confirmed that the recoveries for all six cholic acids are acceptable, varying between 77% and 104%, and are independent on the pH. The total cholic acid content of a Hungarian wastewater plants' influent wastewater varied between 184 microg/L and 356 microg/L, while the Danube rivers' cholic acid content was 4.1 microg/L, only.