A LC/UV/Vis method for determination of cyanocobalamin (VB12) in multivitamin dietary supplements with on-line sample clean-up

A HPLC-UV/Vis method using a two-column strategy with a switching valve for on-line sample cleanup was developed for the determination of cyanocobalamin (CN–Cbl/Vitamin B12) in multivitamin dietary supplement tablets. The method uses two columns: an Agilent Zorbax C8 (150 mm 4.6 mm, 5 mm particle size) reversed-phase column and a Waters Symmetry C18 (150 mm 4.6 mm, 5 mm particle size) reversed-phase column. Chromatographic separation was achieved using a programmed gradient mobile phase consisting of (A) 0.1% formic acid in water and (B) 0.1% formic acid in acetonitrile. Because of the low levels of Vitamin B12 in the samples, large injection volumes, and thus much interfering material, must be used to exceed the limit of quantitation (LOQ) by UV detection. A switching valve was used to divert most of these early eluting interfering materials to waste, effecting on-line sample clean-up without excessive sample preparation steps. The recovery of CN–Cbl in the method was 99.5% and the LOQ was 10 ng per injection. The method was successfully applied to the analysis of the NIST SRM 3280 multivitamin/multimineral dietary supplement tablet. The method is specific, precise, and accurate for the intended use. Compared to off-line sample clean-up procedures, it offers the advantage of being easier, more economical, and less time-consuming

THE STUDY OF THE INFLUENCE OF CHEMICAL DISORDER ON MECHANICAL PROPERTIES OF BINARY ALLOYS OF THE TYPE AND (A = Au; Ag) USING COMPUTER MODELING

In this work, computer simulations of binary alloys of nickel with gold and silver were performed using the Sutton-Chen mathematical model. The simulation was conducted using the general lattice program (GULP) software package [9]. For the alloys, a simulation of ordered and chemically disordered structures were carried out. Elastic moduli, Poisson’s ratio, intrinsic hardness and ductility coefficient were estimated for both ordered and disordered structures. The influence of chemical disorder on the mechanical properties of the alloys was estimated. An attempt was made to assess the significance of the ratio of nickel in the alloys to their mechanical properties. The study found that the influence of chemical disorder on all studied mechanical properties of the metals is significant. In particular, the influence is much higher in shear modulus, on the elastic constant , intrinsic hardness and coefficient of ductility.</jats:p

Computer simulations of the influence of atomic structure disorder on the hardness of Cu − Ag and Au − Ag alloys

Abstract In this paper, computer simulations of the hardness of ordered and disordered alloys of Cu−Ag and Au−Ag were performed using the Sutton-Chen potential and the GULP software package within several models. In addition, Poisson ratios were estimated. When simulating a chemical disorder, a super-cell containing 108 atoms was built. Numerical experiments have shown that chemical disorder in the studied alloys leads to hardness degradation.</jats:p

Prevalence of brucellosis and associated risk factors in dairy cattle in Maekel and Debub regions, Eritrea

IntroductionBrucellosis is a zoonotic disease with worldwide distribution. It is considered endemic in Eritrea, however, the current prevalence status and related risk factors in animals are unknown. The objective of this study was to determine the prevalence of and risk factors for brucellosis in dairy cattle in Maekel and Debub regions, Eritrea.MethodsA cross sectional study was conducted between August 2021 and February 2022. A total of 2,740 dairy cattle from 214 herds in 10 sub-regions of Eritrea were selected for blood and data collection. Blood samples were tested using Rose Bengal Plate Test (RBPT) and positive samples were confirmed using competitive (c-ELISA). Data on risk factors was collected using questionnaire and analyzed using logistic regression.ResultsIn total, 34/2740 animals tested positive by RBPT. Of these, 29 were confirmed positive by c-ELISA, giving an apparent and estimated true individual-level prevalence of 1.1% (95% CI: 0.7, 1.5%) and 1.3% (95% CI: 0.9, 1.8%), respectively. Sixteen herds (7.5%) tested positive by RBPT and of these 15 herds (7.0%) were confirmed positive by c-ELISA, giving an estimated true herd-level prevalence of 7.0% (95% CI: 4.0, 10.7). Animal and herd-level apparent prevalence was 1.6 and 9.2% in Maekel, while in Debub it was 0.6 and 5.5%, respectively. Multivariable regression analysis indicated that non-pregnant lactating cows (adjusted odds ratio [aOR] = 3.35; p = 0.042) were more likely to be Brucella sero-positive. History of abortion on the farm (aOR = 5.71; p = 0.026) and larger number of cows in the herd (aOR = 1.14; p &amp;lt; 0.001) were associated with brucellosis sero-positivity in herds.ConclusionBrucellosis prevalence was low in the study areas. Nonetheless, this low prevalence may increase if the disease is not controlled. Therefore, testing animals before movement, good farming practices, sanitary measures, and an awareness raising program on brucellosis are recommended.</jats:sec

Potential cobalt limitation of vitamin B12 synthesis in the North Atlantic Ocean

While recent studies have confirmed the ecological importance of vitamin B12, it is unclear whether the production of this vitamin could be limited by dissolved Co, a trace metal required for B12 biosynthesis, but found at only subnanomolar concentrations in the open ocean. Herein, we demonstrate that the spatial distribution of dissolved B12 (range: 0.13-5 pmol L−1) in the North Atlantic Ocean follows the abundance of total dissolved Co (range: 15-81 pmol L−1). Similar patterns were observed for bacterial productivity (range: 20-103 pmol 3H leucine L−1 hr−1) and algal biomass (range: 0.4-3.9 μg L−1). In contrast, vitamin B1 concentrations (range: 0.7-30 pM) were decoupled from both Co and B12 concentrations. Cobalt amendment experiments carried out in low-dissolved Co waters (∼20 pmol L−1) enhanced B12 production two-fold over unamended controls. This study provides evidence that B12 synthesis could be limited by the availability of Co in some regions of the world ocean