In this work three analytical methods were developed and applied to determine a broad spectrum of selenium species in human urine. The methods are based on different liquid chromatographic separation techniques (ion pairing, anion exchange and cation exchange chromatography) coupled to an inductively coupled plasma-mass spectrometer (ICP-MS) for selenium specific detection. They were adjusted for the determination of nine species named selenate (Se(VI)), selenite (Se(IV)), trimethylselenium ion (TMSe),, methylselenocysteine (SeMCys) and provide detection limits between 0.10 and 0.19 mg Se per L. The procedures were applied to 45 urine samples of individuals of the general population. SeSug1 was detected in 100% (median: 1.79 mg g À1 creatinine; range: 0.47-8.97 mg g À1 creatinine) and SeSug3 (0.80; 0.07-3.53 mg Se per g creatinine) in 80% of the study population. SeSug1 and SeSug3 were strongly correlated; however a shift of their relation was observed in dependence of the exposure level. In 20% of the samples compounds were detected, which could be related to Se(VI) (0.12; 0.03-1.12 mg Se per g creatinine) and SeMCys (0.13; 0.03-0.41 mg Se per g creatinine). TMSe was detected in 18% of the samples. But whenever TMSe was detected, it was found in considerable concentrations (2.91; 2.72-4.42 mg Se per g creatinine). The species SeMet, SeEt, SeMeG and Se(IV) were not detected in any of the samples. The results of the study are consistent with the literature in which SeSug1 is well-established as major selenium species in human urine since years. Moreover, the results show that the composition of urinary eliminated Se-species might change depending on the Se exposure level. Finally, the results indicate a polymorphic selenium metabolism related to the formation of TMSe.D-glucosamine (SeSug2) and methyl-2-amino-2-deoxy-1-seleno-b-D-galactopyranoside (SeSug3), are major urinary eliminated selenium metabolites. 11-15 Furthermore, Klein et al.

An in vivo metabolism study in humans was carried out to investigate the toxicokinetics and metabolism of sodium selenate differentiating by the trimethylselenium (TMSe) status. Therefore, the changes in blood plasma concentration and the urinary excretion within 24 h of seven healthy subjects after oral administration of a dietary supplement containing sodium selenate (50 μg selenium) were analyzed. Three subjects belong to the subgroup of TMSe eliminators, and four subjects were related to the non-TMSe eliminators subgroup. The concentrations of total selenium in blood plasma and urine samples were determined by inductively coupled plasma-mass spectrometry (ICP-MS). Additionally, speciation analysis of urine samples was performed using ICP-MS coupled to a liquid chromatography system. Plasma selenium concentration changed from 82.5 ± 12.5 μg Se/L before to 85.1 ± 12.0 μg Se/L 2-3 h after supplementation. Considering the individual 24-hour background amounts of renal excreted selenium, the ingestion caused an additional excretion of 15.4 ± 3.3 μg Se/24 h (≙31.1 ± 7.6 % of the administered dose) with a maximum elimination already 2 h after exposure. The differentiated analysis revealed that in all subjects, the main elimination product (30.1 ± 6.9 % of the administered dose) was unmetabolized selenate. TMSe was only detected in the urine of the TMSe eliminators. This subgroup excreted in comparison with the non-TMSe eliminators a significantly lower amount of selenate. Only one subject metabolized selenate to a larger portion to methyl-2-acetamido-2-deoxy-1-seleno-β-D-galactopyranoside (SeSug1) and methyl-2-amino-2-deoxy-1-seleno-β-D-galactopyranoside (SeSug3). All other subjects showed only a minor metabolism of selenate to selenium-containing carbohydrates. By individuals, which do not excrete TMSe in urine basically, selenate is metabolized only marginally and is excreted rapidly via urine generally. In contrast, a considerable portion of this inorganic selenium compound is metabolized by individuals, which eliminate TMSe basically. An elevated metabolism may also be provided by individuals, which eliminate high levels of selenium-containing carbohydrates basically. The difference in metabolism may imply a different disposition for pharmacological or toxic effects by exposure to inorganic selenium compounds.

A human in vivo metabolism study was carried out to investigate the impact of the trimethylselenium ion (TMSe) status on metabolism and toxicokinetics of sodium selenite and selenized yeast. Nine healthy human volunteers were orally exposed to 200 µg selenium as sodium selenite and seven with selenized yeast (100 µg selenium). In each intervention group, three subjects belong to TMSe eliminators. Blood samples were withdrawn before and up to 6 h after administration. Urine samples were collected before and within 24 h after administration. Total selenium (Se) was quantified in blood plasma and urine and low molecular Se species in urine. Selenium concentration in plasma increased from 84.5 ± 13.2 µg Se/L before to 97.4 ± 13.2 µg Se/L 2-3 h after selenite supplementation and 89.5 ± 12.9 µg Se/L to 92.1 ± 13.9 µg Se/L after selenized yeast intake. The oral ingestion caused an additional Se elimination via urine of 16.9 ± 10.6 µg/24 h (TMSe elim.: 10.8 ± 6.9 µg/24 h; non-TMSe elim.: 20.0 ± 11.3 µg Se/24 h) after selenite exposure and 11.8 ± 4.1 µg/24 h (TMSe elim.: 10.8 ± 4.6 µg/24 h; non-TMSe elim.: 12.6 ± 4.2 µg Se/24 h) after selenized yeast exposure. Methyl-2-acetamido-2-deoxy-1-seleno-β-D-galactopyranoside (SeSug1) was the main metabolite in all urine samples, whereas TMSe was another main metabolite in TMSe eliminators' urine. After selenite exposure, a small amount of the dose (0.5 ± 0.2 %) was oxidized to selenate and rapidly excreted via urine. With the exception of selenite exposure in TMSe eliminators, the comparison of total Se and the sum of quantified Se species revealed a high renal portion of unidentified species. The study indicated a different metabolism of inorganic and organic Se compounds in human, but also crucial differences of Se metabolism in TMSe eliminators and non-TMSe eliminators.

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Geraniol is a fragrance which occurs in natural terpene oil or is chemically synthesized on a large scale. It is used in a wide variety of consumer products such as...