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51.
高效离子排斥色谱法测定饮料中的糖精钠 总被引:3,自引:0,他引:3
提出了一种用高效离子排斥色谱法测定饮料中糖精钠的新方法。以IonPac ICE-AS 6柱为分离柱,0.10 mmol/LH2SO4+甲醇(9+1)为淋洗液,202nm波长下紫外检测。在1-100mg/L范围内,糖精钠的含量与峰面积呈 良好线性关系。检出限为0.60ng,灵敏度优于以往采用离子交换色谱-电导检测法的结果。在实验条件下,饮料 中常见有机酸以及其它人工合成甜味剂等均不产生干扰。方法用于饮料中糖精钠的测定,加标回收率为98%~ 105%。此外还比较了电导检测、紫外检测和经化学抑制系统后紫外检测等三种检测方式对测定灵敏度的影响。 相似文献
52.
Controlled potential coulometric (CPC) studies were carried out for developing a method to determine gallium at milligram levels, in the mixed supporting electrolyte medium (4 M NaClO4 + 0.5 M NaSCN), employing stirring mercury as a working electrode. Investigations for optimization of working electrode potentials, quantity of charge, level of background current and electrolysis time for achieving quantitative reduction of Ga(III) to Ga and its oxidation back to Ga(III), were undertaken. Effect of gallium content and interference of zinc in of gallium determination were also studied. The developed methodology was employed for the determination of gallium in pure Ga as well as in synthetic U + Ga mixture solutions. Accuracy and precision values of better than 0.5% were obtained at 1-2 mg levels. 相似文献
53.
54.
Behzad Zeynizadeh 《中国化学会会志》2005,52(3):525-530
α,β‐Unsaturated aldehydes and ketones were reduced readily and exclusively to their corresponding allylic alcohols with NaBH4 and catalytic amounts of titanyl acetylacetonate at room temperature. Reduction reactions were carried out in CH3CN or THF. This reducing system was also efficient for the reduction of α‐diketones and acyloins to their corresponding vicinal diols in CH3CN. 相似文献
55.
The diffusion coefficient of sodium hexadecanoate micelles was studied by polarography at 63°C, and the size and aggregation number of the micelles was computed. At concentrations above 0.01 mol·L–1 rodlike micelles exist, which become flexible at 0.040 mol·L–1 and entangle at 0.043 mol·L–1 相似文献
56.
57.
铝酸钠溶液的紫外吸收峰 总被引:4,自引:0,他引:4
分别用量子化学MNDO和DV-X_α方法计算了二聚铝酸离子[Al_2O(OH)_6]~(2-)和Al(OH)_4~-。结果表明前者旋转势垒很低, 只有10.08 kJ·mol~(-1), 最稳定平衡构型为C_s。用X_α过渡态理论计算获得这两个离子紫外吸收峰的理论值分别为266.6 nm和234.4 nm, 与实验值270.0 nm和230.0 nm相当接近。因此可以认为, 紫外吸收峰270.0 nm和230.0 nm分别为[Al_2O(OH)_6]~(2-)和Al(OH)_4~-离子的最高占有轨道电子向最低空轨道跃迁时产生的吸收峰。计算结果支持铝酸钠溶液中存在二聚铝酸离子的观点。 相似文献
58.
Mohammad Ali Zolfigol Khodabakhsh Niknam Mojtaba Bagherzadeh Arash Ghorbani‐Choghamarani Nadiya Koukabi Maryam Hajjami Eskandar Kolvari 《中国化学会会志》2007,54(5):1115-1118
Tribromoisocyanuric acid (TBCA) and Oxone®‐MX systems were used as effective oxidizing agents for the oxidation of thiols to their corresponding disulfides under mild conditions at room temperature with good to excellent yields. 相似文献
59.
Conditions for converting a set of five standard proteins to electrochemically active sodium dodecylsulfate (SDS) complexes were worked out with the aim of using such complexes for conductivity detection with a a chip electrophoresis system. The results obtained were compared with standard capillary electrophoresis (37 cm (effective length 30 cm)×75 μm I.D. capillary, 10 kV, negative polarity at the inlet). The chip separations were run at 500 V per chip (100 V/cm) as compared to the standard capillary arrangement, which was run at 266.6 V/cm. For the capillary set-up the protein complexes were prepared in aqueous solution (Milli-Q water) made 10 mM with respect to SDS. If the SDS concentration was increased to 50 mM, the separation in the capillary was incomplete. On the other hand with the chip system both approaches yielded acceptable results. The chip separations were slightly (but not distinctly) shorter and offered better separations than the standard set-up. The concentration of the surfactant used for the preparation the complexes results in alternations of the elution sequence, which is preserved if the chip separation is used instead of the capillary set-up. Apparently the full capacity of protein–SDS binding is not exploited for the preparation of the adducts. 相似文献
60.
《Electroanalysis》2006,18(11):1081-1089
This paper describes the voltammetric behavior of As(III) at the hanging mercury drop electrode (HMDE) in the presence of sodium diethyl dithiocarbamate (SDDC) and a new voltammetric method for the determination of As(III) at trace levels. The method is based on the adsorptive deposition of a As(III) complex with SDDC at ?0.45 V (vs. Ag/AgCl) on the HMDE in acidic medium of 0.01 mol L?1 HCl (pH 2.0) and its cathodic stripping during the potential scan (100 mV s?1). The linear range for the determination of As(III) in the presence of SDDC (4 μmol L?1) in water samples was between 1 and 10 μg L?1 for a deposition time of 300 s (r=0.994) and between 10 and 100 μg L?1 for a deposition time of 60 s (r=0.999). For the determination of As(III) in dialysis concentrate samples, the linear range was between 5 and 25 μg L?1 for a deposition time of 180 s (r=0.992) and between 10 and 100 μg L?1 for a deposition time of 60 s (r=0.996). Detection limits of 0.3 and 2.2 μg L?1 in water and dialysis concentrate samples were calculated for the method using a deposition time of 300 and 180 s, respectively. Recovery values between 93.0 and 110.0% for As(III) added to deionized, mineral, seawater (synthetic and real) and dialysis concentrate samples prove the satisfactory accuracy and applicability of the procedure. 相似文献