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11.
12.
A novel titrimetric method with amplification has been developed for the determination of 0.05–2.0 mg of salicylic, acetylsalicylic, or p-hydroxybenzoic acid. It depends on bromination of these compounds by bromine to tribromophenylhypobromite, which liberates iodine when treated with iodide. The liberated iodine is extracted with chloroform, reduced to iodide, oxidation of the resulting iodide with bromine, and iodometric titration of the iodate produced gives the sixfold amplification method. The coefficient of variation does not exceed 1% for above 0.5 mg of the studied compounds, but increases to 2.8% at the 0.05-mg level. 相似文献
13.
Tellurium was determined by introducing a solid membrane for the selective determination of tellurite ion. An electrode composed of a compressed disk containing a mixture of HgTeO3and Hg2Cl2was found to give a typical Nernstian response of 29 mV/concentration decade for the concentration range 10−5to 10−1M). The connection was made by Hg metal instead of aqueous inner filling. The optimum pH was 3.5–10.5. The selectivity of the electrode toward several inorganic and organic anions was estimated. The electrode was applied to the determination of tellurium in binary mixtures with a mean recovery of 98.99% and relative standard deviation range of 0.19–0.51%. 相似文献
14.
A titrimetric and spectrophotometric methods for cerium(IV) determination have worked out. The first method relies upon the treatment of cerium(IV) solution with an excessive amount of iodide; the liberated iodine is extracted into chloroform, then reduced to iodide. The latter is iodometrically determined after 6- or 36-fold amplification. The spectropho-tometric finish is based upon the reaction of the titled ion with iron(II), in the presence of hexacyanoferrate(II), to form an intense prussian blue color suitable for the trace determination of cerium(IV) ion. 相似文献
15.
A simple, rapid and sensitive Spectrophotometric method is proposed for the determination of cephadroxil (I), cephalexin (II) and cephradine (III). The method is based on ion-pair complex formation between these derivatives and Chromotrope 2B (C2B) or Chromotrope 2R (C2R), to give a highly coloured radical anion. The coloured products are quantified spectrophotometrically at 542 and 564 nm for C2B and C2R, respectively. The optimization of the experimental conditions is described. The method has been used for the determination of 0.4–15, 0.4–14 and 0.4–18 g/ml of drugs I, II and III, respectively. The accuracy of the method is indicated by the excellent recovery (100.0±1.7%) and the precision is supported by the low relative standard deviations 1.5%. The sensitivity of the method is discussed and the results are compared with the official method. The interference from common degradation products and excipients was also studied. The proposed method was applied successfully to the determination of the different cephalosporins in dosage forms, with good precision and accuracy. The results were compared with those given by the official B.P. 1993 method. 相似文献
16.
M. S. Marthas S. G. Amin H. P. S. Chawk Ajay K. Bose 《Journal of heterocyclic chemistry》1978,15(4):601-604
A convenient synthesis of α-hydroxy-β-lactams has been devised that involves the annelation of an inline with benzyloxyacetyl chloride and triethylamine and subsequent hydrogenolysis in the presence of palladium on carbon. In most cases a cis-β-lactam was obtained. A thioimidate can also be used as the imino component in the annelation reaction but the hydrogenolysis step fails. The annelation of the appropriate thiazoline to a 6-epi-penicillin derivative occurred much more readily with benzyloxyacetyl chloride than with azidoacetyl chloride. 相似文献
17.
A spectrophotometric procedure for the determination of six pharmaceutical sulfonamides containing a primary aromatic amino group using alizarine (I), alizarine blue (II), alizarine red (III), and quinalizarine (IV), that offers advantages of simplicity, rapidity, sensitivity, precision, and stability, has been developed. The proposed method is based on the formation of colored products with the chromogenic reagents (I-IV). A linear correlation was found between absorbance at λmax and the concentration. For more accurate results, Ringbom optimum concentration ranges are evaluated. The molar absorptivities (ε), absorptivities (a), and Sandell sensitivities for all sulfonamides derivatives with the chromogenic reagents tested were calculated. The procedures developed are applied for bulk sulfa drugs and some of their dosage forms. 相似文献
18.
A. A. Abd El Raheem Abdel Aziz Amin A. S. Moustafa 《Fresenius' Journal of Analytical Chemistry》1960,172(5):347-356
Summary Omega Chrome Fast Blue 2G has been found to be a suitable indicator for the detection of the equivalence point of calcium, magnesium and manganese in the presence of cadmium, nickel, and aluminium, when they are masked by the addition of cyanide or triethanolamine. It is also a suitable indicator for the back titration of aluminium using calcium or magnesium as a back titrant.This dye has also been found to be a suitable reagent for the colorimetric determination of calcium, magnesium, manganese and thorium. 相似文献
19.
A method for the determination of boron concentration in extracted (NH4)2 U2O7·H2O (ADU) has been used. One ml of the aqueous solution is irradiated with thermal neutrons from a 10 Ci Am/Be neutron source with a flux of 0.2·105 n·cm–2·s–1 and thermal column in the IRT-5000 with a flux of about 107 n·cm–2·s–1. The alpha-activity due to the reaction10B(n, )7Li is recorded by a CR-39 alpha track detector. After the exposure, the alpha tracks are made visible in an optical microscope at magnification of 800X by etching the detector in 6N NaOH, and the track density is determined using calibration curves of known concentrations of boron. The boron concentration of the extracted ADU was found to be 5 ppm. 相似文献
20.
In this work, the enzymatic degradation of poly(butylene succinate-co-butylene terephthalate) (PBST) copolyesters was studied using the lipase from Pseudomonas (Lipase PS®). The biodegradation behavior was found to strongly depend on the overall impacts of several important factors as the BT comonomer structure and molar content, thermal characteristics, morphology, the enzyme-substrate, and so forth. Further, the biodegraded residual film samples were allowed to be analyzed by means of gel permeation chromatography (GPC), proton nuclear magnetic resonance (1H NMR), differential scanning calorimeter (DSC), small angle X-ray scattering (SAXS), and scanning electron microscope (SEM). On the experimental evidences, an exo-type mechanism of enzymatic chain hydrolysis preferentially occurring in the amorphous region was suggested for the PBST film samples. 相似文献