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1.
An ion chromatographic method was developed for the determination of nitrate and nitrite in vegetable and fruit baby foods. The introduction of nitrate or nitrite to food may be natural or artificial as a preservative. Because of the higher pH found in babies' stomachs, nitrate can act as a reservoir for the production of nitrite by nitrate-reducing bacteria that can be harbored in the intestinal tract. This problem does not exist in adults because of the lower pH of the adult stomach. Exposure to nitrite by infants can result in methemoglobinemia (blue baby syndrome). There are also indications that carcinogenic nitrosamines can be formed from nitrates at the higher pH. These gastric conditions disappear at approximately 6 months of age. In this method, nitrate and nitrite were separated on a hydroxide-selective anion exchange column using online electrolytically generated high-purity hydroxide eluant and detected using suppressed conductivity detection. Average recoveries of spiked nitrite residue ranged from 91 to 104% and spiked nitrate residue ranged from 87 to 104%. This method and the AOAC Official Method yield comparable results for samples containing incurred nitrate residue. In addition, this method eliminates the hazardous waste associated with the use of cadmium found in the AOAC Official Method. 相似文献
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Single crystals of Ca3Cu3(PO4)4 synthesized hydrothermally at 420°C and 55 kpsi (3.8 kbar) were found to occur in the space group (No. 14) with a = = 17.619(2), b = 4.8995(4), c = 8.917(1)Å, β = 124.08(1)°, and Z = 2. Full-matrix least-squares refinement of the structure using diffractometer data converged to a final anisotropic R = 0.037 (Rw = 0.046). The two calcium atoms are in six- and nine-coordination and the two copper-containing polyhedra (four- and five-coordinated) are similar to those previously found in Cu3(PO4)2. 相似文献
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Methoxypalladation of C-6 substituted pyranoside glycals followed by addition of sodium cyanoborohydride gives allylic rearrangement products in good yield with excellent regio-and stereoselectivity. 相似文献
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Lois Mansfield 《Numerische Mathematik》1974,22(2):89-97
For a triangulated polygon Ω, classes of piecewise rational functions are defined which are inC p?1 (Ω). A basis of these functions which contains all polynomials of degree 2p?1 or less is considerably smaller than a similar basis of piecewise polynomial functions. 相似文献
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The rates of hydrogenation of several styrene derivatives by stoichiometric hydridocobalt tetracarbonyl [HCo(CO)4] were measured and compared. The relative rates are discussed in terms of conjugative and steric effects on the geminate radical pair mechanism. An improved method for determining HCo(CO)4 concentration is described. 相似文献
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