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A single laboratory validation (SLV) study was conducted for a liquid chromatography (LC) method for the determination of total and all-trans-beta-carotene in a variety of dietary supplements, including multivitamin tablets, softgels, capsules, and beadlet raw materials. Extraction variants were developed for the different types of supplements tested based upon the supplement type and level of beta-carotene. Water dispersible formulations such as powders, emulsions, tablets, and capsules were enzymatically digested with protease and extracted with dichloromethane-ethanol. Oily suspensions were directly dissolved in dichloromethane-ethanol. After appropriate dilution or concentration, the extracts were chromatographed by using either a reversed-phase C18 column or, in products containing high amounts of alpha-carotene, a reversed-phase C30 column. The LC systems provided linear responses in the range of 0.1-50 microg beta-carotene/mL. The main geometrical isomers of beta-carotene (all-trans, 9-cis, 13-cis, and 15-cis) were well separated from each other and from other carotenoids such as a-carotene, cryptoxanthin, lutein, lycopene, and zeaxanthin. Duplicate determinations of total beta-carotene performed by 2 technicians in 8 different test materials on 5 different days resulted in relative standard deviations of 1.2-4.4%. Recoveries determined for supplements and beadlet raw material spiked with beta-carotene levels of 10 microg to 100 mg/test portion and 0.2-40%, respectively, ranged from 97.5 to 102.1%. On the basis of the accuracy, precision, and recovery results from the SLV study, the method is suggested for a collaborative study on the determination of total and all-trans-beta-carotene in dietary supplements. 相似文献
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Angie?S?Mah Andrew?EH?Elia Geeta?Devgan Jason?Ptacek Mike?Schutkowski Michael?Snyder Michael?B?Yaffe Raymond?J?DeshaiesEmail author 《BMC biochemistry》2005,6(1):22
Background
The mitotic exit network (MEN) is a group of proteins that form a signaling cascade that is essential for cells to exit mitosis in Saccharomyces cerevisiae. The MEN has also been implicated in playing a role in cytokinesis. Two components of this signaling pathway are the protein kinase Dbf2 and its binding partner essential for its kinase activity, Mob1. The components of MEN that act upstream of Dbf2-Mob1 have been characterized, but physiological substrates for Dbf2-Mob1 have yet to be identified. 相似文献4.
A high-pressure liquid chromatographic method has been developed for use as a stability-indicating assay for mecillinam. Seven related compounds and at least one unknown degradation product are well separated and easily determined. The accuracy of the method is in good agreement with the published UV assay and the precision of a series of seven replicate determinations is +/- 1.0% R.S.D. 相似文献
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Stability-indicating assay for pivmecillinam hydrochloride and pivmecillinam hydrochloride capsules.
A high-pressure liquid chromatographic assay has been developed for pivmecillinam hydrochloride and pivmecillinam hydrochloride capsules. The method separates five reported degradation products and a number of esterified, related compounds. The accuracy of this method is comparable to the published ultraviolet assay and the relative standard deviation of a series of six replicate assays was better than +/- 0.7%. 相似文献
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Rednikov AY; Zhao Hong; Sadhal SS; Trinh EH 《The Quarterly Journal of Mechanics and Applied Mathematics》2006,59(3):377-397
The steady (acoustic) streaming associated with a sphericaldrop displaced from the velocity antinode of a standing waveis studied. The ratio of the particle size to the acoustic wavelengthis treated as small but non-zero, and the solution is developedin the form of a two-term expansion in terms of the correspondingsmallness parameter. The drop viscosity is assumed to be muchhigher than that of the surrounding fluid, which is the casefor a drop in a gas medium. There are essentially three distinctregions where the steady streaming flow is analysed: insidethe drop (internal circulation), in the Stokes shear-wave layerat the surface on the gas side, and the gas outside the Stokeslayer (the outer streaming region). Solutions for the internalcirculation and the outer streaming are obtained in the limitof small Reynolds number. Despite the gas-to-liquid viscosity ratio being small, the outerstreaming may be dramatically affected by the fact that thesphere is liquid as opposed to solid. The parameter that measuresthe effect of liquidity is essentially the viscosity ratio dividedby the relative (to the particle size) thickness of the Stokeslayer. The case of a solid sphere is recovered by letting thisparameter go to zero. 相似文献
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Rimmer CA Howerton SB Sharpless KE Sander LC Long SE Murphy KE Porter BJ Putzbach K Rearick MS Wise SA Wood LJ Zeisler R Hancock DK Yen JH Betz JM Nguyenpho A Yang L Scriver C Willie S Sturgeon R Schaneberg B Nelson C Skamarack J Pan M Levanseler K Gray D Waysek EH Blatter A Reich E 《Analytical and bioanalytical chemistry》2007,389(1):179-196
A suite of three ginkgo-containing dietary supplement Standard Reference Materials (SRMs) has been issued by the National
Institute of Standards and Technology (NIST) with certified values for flavonoid aglycones, ginkgolides, bilobalide, and selected
toxic trace elements. The materials represent a range of matrices (i.e., plant, extract, and finished product) that provide
different analytical challenges. The constituents have been determined by at least two independent analytical methods with
measurements performed by NIST and at least one collaborating laboratory. The methods utilized different extractions, chromatographic
separations, modes of detection, and approaches to quantitation. The SRMs are primarily intended for method validation and
for use as control materials to support the analysis of dietary supplements and related botanical materials.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献