Rapid simultaneous determination of 7 fat-soluble vitamins in human serum by ultra high performance liquid chromatography tandem mass spectrometry.

Accurate detection of vitamins is critically important for clinical diagnosis, metabolomics and epidemiological studies. However, the amounts of different vitamins vary dramatically in human serum. It is a challenge to achieve simultaneous detection of multiple vitamins rapidly. Herein, we developed and validated a sensitive and specific method using ultra high-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) for simultaneous quantification of 7 fat-soluble vitamins (FSVs) across their physiological concentrations in serum for the first time, which was subjected to protein precipitation, liquid-liquid extraction to an organic phase, evaporation to dryness and reconstitution with acetonitrile. In the present procedure, retinol (vitamin A), ergocalciferol (25-OH-D2), cholecalciferol (25-OH-D3), α-tocopherol (vitamin E), phylloquinone (vitamin K1), menatetrenone-4 (MK-4), and menaquinone-7 (MK-7) were detected in one analytical procedure for the first time within 5.0 min by triple quadrupole tandem mass spectrometry. The limit of quantification (LOQ) for vitamin A was 10.0 ng mL-1, LOQs for 25-OH-D2 and 25-OH-D3 were 1.0 ng mL-1, LOQ for vitamin E was 100.0 ng mL-1, and LOQs for vitamin K1, MK-4 and MK-7 were 0.10 ng mL-1, respectively, with a correlation (R2) of 0.995-0.999. Recoveries ranged from 80.5% to 118.5% and the intra-day and inter-day coefficients of variance (CVs) were 0.72-8.89% and 3.2-9.0% respectively. The method was validated according to the European Medicines Agency (EMA) and U.S. Food and Drug guidelines and C62-A on bioanalytical methods, and was used for clinical routine determination.

Urinary metabolites of organophosphate esters and implications for exposure pathways in adolescents from Eastern China.

Ten urinary biomarkers of organophosphate esters (OPEs) from six parent OPEs were analyzed in urine from adolescents students in Eastern China. Bis (1,3-dichloro-2-propyl) phosphate, urinary biomarker of tris (1,3-dichloro-2-propyl) phosphate (TDCIPP), was detected in all urine samples with the highest residual concentration of 6.2 ng/mL (median). Bis (1-chloro-propyl) hydroxyl-2-propyl phosphate, dibutyl phosphate, biomarkers of tris (1-chloro-2-propyl) phosphate (TCIPP), tri-n-butyl phosphate (TNBP), respectively, and tris (2-chloroethyl) phosphate (TCEP), were also frequently detected with median concentrations of 1.5, 2.6 and 0.3 ng/mL, respectively. Results indicate that exposure to OPEs, in particular to TDCIPP, TNBP, TCIPP and TCEP, was highly prevalent for adolescent students. The exposure pathways of OPEs were then evaluated according to the OPE internal body burdens (IBBs). Three pathways were identified as the main pathways for adolescents exposed to OPEs including dermal absorption, oral intake of food and dust and inhalation.

Residuals of organophosphate esters in foodstuffs and implication for human exposure.

Foodstuffs may be contaminated by organophosphate esters (OPEs) and become an important source of human exposure since OPEs are ubiquitous in the environment. In the present study, 10 OPEs were analyzed in various food matrices collected from a city in Eastern China including chicken, pork, fishes, vegetables, tofu, eggs, milk and cereals. The concentrations of Σ10OPEs ranged from 1.1 to 9.6 ng g-1 fresh weight (fw) in the foodstuffs. Cereals had the highest residual level of total OPEs with a mean value of 5.7 ng g-1 fw. Tris(2-ethylhexyl) phosphate was detected in all foodstuff samples and showed the highest median residual concentration of 1.3 ng g-1 fw among the OPE analogs. The daily dietary intake of OPEs was calculated as 3.6 and 2.4 µg d-1 for adults and children. Cereals were identified as the major contributor to the total OPEs among different types of foodstuffs. Preliminary exposure assessment revealed that the current non-cancer health risks of OPEs via dietary intake were in the range of 10-5-10-3, indicating low risk levels. Moreover, the hazard index of OPEs indicated that the risk for children (3 × 10-3) was higher than adults (2 × 10-3).