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31.
A highly sensitive spectrophotometric method has been developed for determination of chromium(VI), based on oxidation of I(-) to I(-)(3) in acid medium, then formation of a 1:1 ion-association compound of I(-)(3) with a basic xanthene dye in the presence of poly(vinyl alcohol). The molar absorptivity is 1.79 x 10(5) 1.mole(-1).cm(-1) at 600 nm for the Rhodamine B system, 1.56 x 10(5) 1.mole(-1).cm(-1) at 600 nm with Ethylrhodamine B, 1.56 x 10(5) 1.mole(-).cm(-1) at 570 nm with Rhodamine 6G and 2.01 x 10(5) 1.mole(-1).cm(-1) at 590 nm with Butylrhodamine B, respectively. Preconcentration of chromium(VI) by an improved trioctylamine extraction procedure greatly increases the selectivity of the method and can be applied in the spectrophotometric determination of trace amounts of chromium(VI) in tap water, hot-spring water and river water. 相似文献
32.
多波长叠加近红外吸收光谱法直接测定酒精饮料中的乙醇 总被引:17,自引:0,他引:17
利用乙醇在1382nm,1691nm和1730nm处的吸光度值,采用多波长叠加近红外吸收光谱法测定乙醇的含量。结果表明,乙醇在0%~24%(V/V)浓度范围内呈良好的线性关系;回归方程为: A= 0. 01754+ 0. 04747C;相关系数r=0. 9994。用该法可直接测定葡萄酒、啤酒和黄酒中乙醇的含量,6次平行测定的RSD分别为;葡萄酒4.0%,啤酒2.5%,黄酒2.4%。回收率为97.5%~105.0%,本方法具有操作简便,准确和快速等优点。 相似文献
33.
Zhengwen Liu Shaopu Liu Lei Wang Juanjuan Peng Youqiu He 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,74(1):36-41
In pH 6.6 Britton–Robinson buffer medium, the CdS quantum dots capped by thioglycolic acid could react with aminoglycoside (AGs) antibiotics such as neomycin sulfate (NEO) and streptomycin sulfate (STP) to form the large aggregates by virtue of electrostatic attraction and the hydrophobic force, which resulted in a great enhancement of resonance Rayleigh scattering (RRS) and resonance non-linear scattering such as second-order scattering (SOS) and frequency doubling scattering (FDS). The maximum scattering peak was located at 310 nm for RRS, 568 nm for SOS and 390 nm for FDS, respectively. The enhancements of scattering intensity (ΔI) were directly proportional to the concentration of AGs in a certain ranges. A new method for the determination of trace NEO and STP using CdS quantum dots probe was developed. The detection limits (3σ) were 1.7 ng mL−1 (NEO) and 4.4 ng mL−1 (STP) by RRS method, were 5.2 ng mL−1 (NEO) and 20.9 ng mL−1 (STP) by SOS method and were 4.4 ng mL−1 (NEO) and 25.7 ng mL−1 (STP) by FDS method, respectively. The sensitivity of RRS method was the highest. The optimum conditions and influence factors were investigated. In addition, the reaction mechanism was discussed. 相似文献
34.
Tetracycline antibiotics (TCs) such as doxycycline (DOTC), chlortetracycline (CTC), oxytetracycline (OTC), and tetracycline
(TC) react with Cu(II) in pH 3.5 BR buffer medium to form 1:1 cationic chelates, which further react with titan yellow to
form 2:1 ion association complexes. These result in great enhancement of resonance Rayleigh scattering (RRS) and the appearance
of new RRS spectra. The ion association complexes of DOTC, CTC, OTC, and TC have similar spectral characteristics and their
maximum RRS wavelengths are all located at 464 nm. The quantitative determination ranges and the detection limits (3σ) of the four TCs are 0.037–4.8 μg mL−1 and 11.2 ng mL−1 for DOTC, 0.041–5.2 μg mL−1 and 12.4 ng mL−1 for CTC, 0.050–4.8 μg mL−1 and 15.1 ng mL−1 for TC, and 0.088–5.0 μg mL−1 and 26.3 ng mL−1 for OTC, respectively. The optimum reaction conditions, the effects of foreign substances, the structure of ternary complexes,
and the reaction mechanism are discussed. A sensitive, rapid, and simple RRS method for the determination of DOTC has been
developed. 相似文献
35.
本文讨论了Girsanov 变换下两个Gauss概率空间中Malliavin 计算及算子之间的关系 相似文献
36.
本文考虑了如下Hilbert空间中半线性随机发展方程(1)的Cauchy问题,在两组不同的条件下,分别得到了该问题的适度解的整体存在唯一性。 相似文献
37.
钒(Ⅴ)-硫氰酸盐-碱性三芳基甲烷染料的显色反应研究 总被引:3,自引:0,他引:3
研究了在表面活性剂存在下,钒(V)与硫氰酸盐和结晶紫、孔雀绿、灿烂绿、甲基紫及维多利亚蓝4R等碱性三芳基甲烷染料形成离子缔合物的显色反应.讨论了钒(V)-硫氰酸盐-结晶紫-阿拉伯树胶体系的反应条件和分析特性。摩尔吸光系数为2.55×105L·mol-1·cm-1.此法可用于铝合金中微量钒的测定。 相似文献
38.
Let v, k be positive integers and k ≥ 3, then Kk = : {v: v ≥ k} is a 3‐BD closed set. Two finite generating sets of 3‐BD closed sets K4 and K5 are obtained by H. Hanani [5] and Qiurong Wu [12] respectively. In this article we show that if v ≥ 6, then v ∈ B3(K,1), where K = {6,7,…,41,45,46,47,51,52,53,83,84}\{22,26}; that is, we show that K is a generating set for K6. Finally we show that v ∈ B3(6,20) for all v ∈ K\{35,39,40,45}. © 2007 Wiley Periodicals, Inc. J Combin Designs 16: 128–136, 2008 相似文献
39.
40.
A flow injection analysis (FIA) method coupled to resonance Rayleigh scattering (RRS) detection for the determination of verapamil hydrochloride (VP) was proposed. In pH 1.0 acidic medium, 12-tungstophosphoric acid (TP) reacted with VP to form an ion-association complex, which resulted in a significant enhancement of RRS intensity. The maximum scattering peak was located at 293 nm. RRS intensity was proportional to the concentration of VP in the range of 0.017-13.0 μg mL−1, and the detection limit (3σ) was 5.1 ng mL−1. The proposed method exhibited satisfactory reproducibility with a relative standard derivation (R.S.D.) of 2.1% for 11 successive determinations of 5.0 μg mL−1 VP. Therefore, a novel method for the determination of VP by FIA-RRS was developed. The optimum reaction conditions and the parameters of the FIA operation such as flow rate, injection volume, reactor length, and so on had been optimized in this paper. The present method had been applied to the determination of VP in serum samples and pharmaceuticals with satisfactory results. The maximal sample throughput in the optimized system was 80 h−1. 相似文献