The determination of xenobiotics in keratinized matrices, such as nails and hair, has received considerable attention because of the relatively long detection window for compounds. The distribution of xenobiotics in fingernails, unlike hair, was equivocal. The main aim of this study was to use follow-up surveys to measure zolpidem profiles in nails after subjects consumed a single dose of the drug. In addition, the zolpidem concentrations in nails were compared with data for different biosamples, such as hair and blood from previous work. With these preconditions, a high-performance liquid chromatography-tandem mass spectrometry method was developed and validated for the determination of zolpidem in nails. Nails underwent alkaline hydrolysis and were extracted with diethyl ether. A Capcell Pak C18 MGII column was used to separate the target compound, and an API 4000 Qtrap mass spectrometer was used as a detector. The results for nail samples from seven subjects who had taken a single 10 mg zolpidem dose were significant: two relatively high zolpidem concentrations were observed in the long-term follow-up analysis of nails. The zolpidem concentration was less than 1.74 pg/mg and less than 3.29 pg/mg in fingernails and toenails, respectively. The subsequent peak concentration of zolpidem was observed between 10 and 15 weeks after each subject took a single dose of the drug. This result suggested that the germinal matrix area was a primary in vivo pathway for zolpidem secretion into the nail. The analysis of biosamples, such as nails, may be a useful adjunct to conventional methods of drug testing and hair analysis. Further research is needed concerning the contamination risk in analysis of nail biosamples.
Production
of phosphoric acid by using wet process technology in
China is challenging due to high impurities (P2O5 present is less than 25 wt %). Extraction of phosphoric acid from
such low concentration mixtures needs to be improved. Moreover, the
separation of chloride and phosphate ions is also important for the
subsequent production of phosphate fertilizers. In this study, an
organic solvent composed of trialkyl amine (N235), isoamyl alcohol,
and sulfonated kerosene was developed to extract phosphoric acid.
Pseudoternary phase equilibria, two phase densities, and the viscosities
were determined at 298.15 K and atmospheric pressure. Results show
that unlike other common organic solvents, the proposed solvent exhibits
relatively higher extraction capacity even at low phosphoric acid
concentration (P2O5 less than 25 wt %). The
separation factor of chloride and phosphate ions reaches up to 39.45
and is several orders of magnitude lager than other common organic
solvents including alcohols, cyclohexane, and tri-n-butyl phosphate (TBP). In addition, the solubility of organic solvent
in the aqueous phase is close to zero, while the water content in
the organic phase keeps nearly constant at a low concentration of
around 5 wt %. All of these indicated that the developed solvent mixture
is efficient for the extraction of phosphoric acid.
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