Determination of twenty pharmaceutical contaminants in soil using ultrasound-assisted extraction with gas chromatography-mass spectrometric detection.

In this paper, an analytical method for the simultaneous determination of twenty pharmaceuticals (eight non-steroidal anti-inflammatory drugs, five oestrogenic hormones, two antiepileptic drugs, two ß-blockers, and three antidepressants) in soils was developed. The optimal method included ultrasound-assisted extraction, a clean-up step on a silica gel column, derivatization using N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and 1% trimethylchlorosilane (TMCS) in pyridine and ethyl acetate (2:1:1, v/v/v) for 30 min at 60 °C, and determination by gas chromatography-mass spectrometry working in the selected ion monitoring mode. This affords good resolution, high sensitivity and reproducibility, and freedom from interferences even from complex matrices such as soils. The method detection limits ranged from 0.3 to 1.7 ng g-1, the intra-day precision represented as RSDs ranged from 1.1 to 10.0%, and the intra-day accuracy from 81.3 to 119.7%. The absolute recoveries of the target compounds were above 80%, except for valproic acid and diethylstilbestrol. The developed method was successfully applied in the analysis of the target compounds in soils collected in Poland. Among the 20 pharmaceuticals, 12 compounds were detected at least once in the soils. The determination of antiepileptic drugs, ß-blockers, and antidepressants was also performed for the first time.

A new silylation reagent dimethyl(3,3,3-trifluoropropyl)silyldiethylamine for the analysis of estrogenic compounds by gas chromatography-mass spectrometry.

In this study we applied DIMETRIS (dimethyl(3,3,3-trifluoropropyl)silyldiethylamine), a new silylating reagent, to derivative natural estrogens such as estrone (E1), 17ß-estradiol (E2) and estriol (E3), as well as the synthetic 17α-ethinylestradiol (EE2) and the non-steroid diethylstilbestrol (DES). Its derivatizing properties were compared with those of the commonly used mixture of BSTFA (N,O-bis(trimethylsilyl)trifluoroacetamide)+1% trimethylchlorosilane (TMCS) and with MTBSTFA (N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide). The use of DIMETRIS for the silylation all of them is reported for the first time. The nucleophilic properties of DIMETRIS were found to be superior to those of MTBSTFA, but slightly inferior to those of BSTFA. It was used to derivatize steroid (E1, E2, E3 and EE2) and non-steroid (DES) estrogens at 30°C prior to GC/MS analysis. These DMTFPS-derivatives exhibited good separation (low retention times despite the high molecular masses) and ionization properties in GC/MS analyses (the highest relative response factors for DMTFPS-derivatives among those tested). However, DIMETRIS and MTBSTFA (which produce mono-O-silyl derivatives of EE2) should not be used for the simultaneous analysis of EE2 and E1. Only a mixture of BSTFA+1% TMCS in pyridine, which generates the fully derivatized EE2 product (stable in GC injector), permits the determination of these two estrogenic compounds during one GC-MS run. On the other hand, because DIMETRIS requires a lower derivatization temperature than BSTFA, it could be very useful for the derivatization of thermally unstable estrogenic compounds. In the next step of this study, the SPE-GC-MS method based on DIMETRIS derivatization for the analysis of DES, E2 and E3 in aqueous samples was evaluated and validated. The MQL values: 1.4, 1.6 and 1.5ngL(-1) for DES, E2 and E3, respectively, proved its suitability to determine target compounds in environmental samples. Finally, the proposed method was successfully applied to the analysis of selected estrogenic compounds in real seawater and wastewater samples in Poland.

Chemometric optimization of derivatization reactions prior to gas chromatography-mass spectrometry analysis.

Derivatization is a methodological technique that can be used to make an organic compound more suitable for qualitative and/or quantitative analysis (e.g. pharmaceuticals). However, many analysts try to avoid this analytical procedure as it is time-consuming and labour-intensive. On the other hand, an inter-laboratory study demonstrated that with regard to sensitivity and measurement uncertainty, gas chromatography coupled to mass-spectrometry was superior to liquid chromatography coupled to mass spectrometry for the trace analysis of organic compounds in matrices of greater complexity. In our previous paper (Kumirska et al., J. Chemometr. 25 (2011) 636-643) we suggested using principal component analysis (PCA) to optimize the derivatization of six compounds (5 oestrogenic steroids and diethylstilbestrol) prior to GC-MS analysis. In the present work we applied a highly sophisticated model - 24 pharmaceuticals derived from six classes of drugs. The efficiency of different derivatization reactions was evaluated by PCA and compared with that obtained from cluster analysis (CA), the latter method being applied in this context for the first time. Derivatization using N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and 1% trimethylchlorosilane (TMCS) in pyridine and ethyl acetate (2:1:1, v/v/v) for 30min at 60°C was found to be optimal. The SPE-GC-MS method was also validated and successfully applied to the analysis of selected pharmaceuticals in wastewater and surface waters in Poland.

Unexpected photoproduct generated via the acetone-sensitized photolysis of 5-bromo-2'-deoxyuridine in a water/isopropanol solution: experimental and computational studies.

The acetone-sensitized photolysis of 5-bromo-2'-deoxyuridine (5-BrdU) in a water/isopropanol solution with 300 nm photons leads to the formation of 2'-deoxyuridine (dU) and a comparable amount of another photoproduct that has not been reported in the literature so far. The negative and positive mass spectra recorded for this species indicate that they originate from the molecular mass of 286 Da, which corresponds to an adduct of 2'-deoxyuridine and 2-propanol. Quantum chemical calculations carried out at the DFT and TDDFT levels reveal both the structure and the UV spectrum of that adduct. The latter computational characteristic matches well the experimental UV spectrum of the new photoproduct. Our findings indicate that the acetone-sensitized photolysis of 5-BrdU is more complicated than has hitherto been assumed. Nevertheless, since electron transfer is one of the pathways responsible for 5-BrdU decay, acetone-sensitized photolysis of the halogen derivatives of nucleobases could be a convenient tool for studying their radiosensitivity in aqueous solutions.