Precise determination of the molybdenum isotopic composition of urine by multiple collector inductively coupled plasma mass spectrometry.

RATIONALE: Molybdenum (Mo) is predominantly expelled from the human body in urine. Consequently, urinary variability in the concentration and isotopic composition of Mo may encode valuable clinical information. To access this information, however, it is first necessary to develop and demonstrate a rapid, accurate and precise methodology capable of concentrating Mo from urine for isotope analysis. METHODS: The utility of N-benzoyl-N-phenylhydroxylamine (BPHA) to effectively separate and purify Mo from urine samples without the need for acid digestion was tested. Following this approach, applying a double-spike mass bias correction, we determined the Mo isotopic compositions of a set of urine samples by multiple collector inductively coupled plasma mass spectrometry (MC-ICP-MS). RESULTS: Based on replicate analyses of an in-house urine standard, this approach demonstrates an external precision on δ98/95 Mo values of better than 0.08‰ (2SD, n = 15). Application to a sample set collected from healthy individuals in Guangzhou, China, provides the first suite of δ98/95 Mo measurements from urine samples. Samples from the female participants show δ98/95 Mo (‰) values (1.31 ± 0.19‰, Ave ± 2SD, n = 14) that are consistently lower than those from the male participants (1.55 ± 0.16‰, Ave ± 2SD, n = 17). CONCLUSIONS: The employed methodology is suitable for rapid, low-blank and high-throughput Mo isotope analysis of urine samples. Although resolvable δ98/95 Mo variability is seen in this preliminary dataset, the mechanism driving this variability is unknown. High-precision Mo isotopic analysis might be added to the urinalysis tool-kit, with the potential to provide valuable clinical information in the future.

[Study on D-glucosamine-zn (II) complexes by IR spectral analysis].

In this paper, a series of glucosamine-Zn(II) complexes were synthesized by the reaction of D-glucosamine hydrochloride with ZnSO4 at different pH values. The physical properties and the IR spectra of glucosamine-ZnSO4 complexes were investigated. The absorption at 3346 and 3292 cm(-1) shifted to 3300 cm(-1) due to O--H and N--H stretching, one at 1617 cm(-1) shifted to 1530 cm(-1) due to N-H stretching, and one at 1094 cm(-1) disappeared due to secondary alcohol --OH stretching. But 1033 cm(-1) with primary alcohol --OH did not shift, suggesting that both the amino and secondary hydroxyl groups of glucosamine are coordinated to Zn(II). The results showed that the coordination ability of Zn(II) to glucosamine was enhanced with the pH value increasing, however, the coordination ability weakened when pH value was more than 6.5. So pH 6.5 is an optimal coordination condition for glucosamine-ZnSO4 complexes. The complexes of D-glucosamine with different zinc salts (zinc sulfate, zinc nitrate, zinc acetate, and zinc chloride) were also synthesized at the same pH value, and zinc chloride had weaker coordination ability than other zinc salts. Their IR spectra indicated that glucosamine-Zn(II) complexes with different zinc salts had different coordination model, and only glucosamine-ZnSO4 complex had fixed ratio of coordination under the condition of pH 6.5. The structure of the complex seems to correspond to [Zn(glucosamine)]SO4 7H2O at pH 6.5.