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51.
Summary Capillary electrophoresis (CE) has proved to be a fast and convenient method for the determination of the dissociation constants
of non-UV absorbing solutes in the acidic pK
A range (2.0–2.5).
The electroosmotic flow was reversed by washing the capillary with 0.2% polybren aqueous solution. A series of background
electrolytes was prepared with phenylphosphonic acid (pK
A=1.29) and β-alanine (pK
A=3.55) with the same ionic strength and a high buffer capacity in order to improve the repeatability (0.1–0.2 %) of the electrophoretic
mobility and to determine the values of pK
A accurately.
This procedure was applied to the determination of the dissociation constants of several alkyl-alkylphosphonic acids whose
pK
A values have not yet been published in the literature. In this work, their dissociation constants have been found to vary
between 1.91 and 2.34 for alkyl-methylphosphonic acids and between 2.10 and 2.38 for alkyl-ethylphosphonic acids. 相似文献
52.
Thermal lens detection with a 325.0 nm He-Cd excitation laser is used for thermooptical indirect detection in combination with the capillary electrophoretic separation of organic anions. The optimization of indirect thermooptical detection is discussed. With Mordant Yellow 7 (an azo dye) chosen as a probe ion limits of detection for 1-heptane-, 1-pentane-, 1-butane-, 1-propanesulfonic, and acetic acid at a level of n × 10−7 M were achieved with a separation electrolyte containing 50 μM of the probe ion and 5 mM Tris pH 9.90. A further increase in the detection sensitivity (twofold decrease in the limit of detection ) was obtained with a separation electrolyte containing a volume fraction of 20% acetonitrile. 相似文献
53.
Summary A pure silica gel (Pia Seed 5S-60-SIL), synthesized by the hydrolysis of pure tetraethoxysilane [Si(OCH2CH3)4], was applied as a cation-exchange stationary phase in ion chromatography with indirect photometric detection for common
mono-and divalent cations (Li+, Na+, NH4
+, K+, Mg2+, and Ca2+) using various protonated aromatic monoamines (tyramine [4-(2-aminethyl) phenol], benzylamine, phenylethylamine, 2-methylpyridine
and 2,6-dimethylpyridine) as eluet ions. When using 0.75 mM tyramine-0.25 mM oxalic acid-1.5 mM 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane)
at pH 5.0 as the eluent, excellent simultaneous separation and highly sensitive detection at 275 nm for these mono-and divalent
cations were achieved on the Pia Seed 5S-60-SIL column (150×4.6 mm I.D.) in 20 min. 相似文献
54.
Hong Zheng Wei Yu Hon-bin Zhang Chi-xing Zhou 《高分子科学》2006,(1):1-11
Finite element method is used to simulate the high-speed melt spinning process,based on the equation system proposed by Doufas et al.Calculation predicts a neck-like deformation,as well as the related profiles of velocity,diameter, temperature,chain orientation,and crystallinity in the fiber spinning process.Considering combined effects on the process such as flow-induced crystallization,viscoelasticity,filament cooling,air drag,inertia,surface tension and gravity,the simulated material flow behaviors are consistent with those observed for semi-crystalline polymers under various spinning conditions.The structure change of polymer coils in the necking region described by the evolution of conformation tensor is also investigated.Based on the relaxation mechanism of macromolecules in flow field different types of morphology change of polymer chains before and in the neck are proposed,giving a complete prospect of structure evolution and crystallization of semi-crystalline polymer in the high speed fiber spinning process. 相似文献
55.
Simultaneous determination of the fat-soluble vitamins A and E and the water-soluble vitamins B1, B2 and B6 has been carried using a screening method from fluorescence contour graphs. These graphs show different colour zones in relation to the fluorescence intensity measured for the pair of excitation/emission wavelengths. The identification of the corresponding excitation/emission wavelength zones allows the detection of different vitamins in an aqueous medium regardless of the fat or water solubility of each vitamin, owing to the presence of a surfactant which forms micelles in water at the used concentration (over the critical micelle concentration). The micelles dissolve very water insoluble compounds, such as fat-soluble vitamins, inside the aggregates. This approach avoids the use of organic solvents in determining these vitamins and offers the possibility of analysing fat- and water-soluble vitamins simultaneously. The method has been validated in terms of detection limit, cut-off limit, sensitivity, number of false positives, number of false negatives and uncertainty range. The detection limit is about g L–1. The screening method was applied to different samples such as pharmaceuticals, juices and isotonic drinks. 相似文献
56.
微波-气相-热压法分解高纯铂的研究 总被引:1,自引:0,他引:1
本文研究了微波气相热压法新技术分解高纯铂在密闭的聚四氟乙烯高压罐中,以微波瞬间加热混合酸产生的高压、纯净蒸气分解金属铂,此法避免了酸中杂质的沾污以制备供高纯铂分析的试液,提高了痕量杂质分析的准确度和降低检测限 相似文献
57.
无机阴离子的毛细管电泳分析 总被引:9,自引:2,他引:9
本文研究了常见无机阴离子的毛细管电泳规律,考察了分离电压、电解质熔液组成、浓度、pH值等对分离的影响,建立了高效、快速的无机阴离子毛细管电泳分析方法。在选定的实验条件下,各种常见无机阴离子在5min内达到完全分离,对Br^-和Cl^-的分离柱效每米可达76万理论板数。迁移时间的相对标准偏差小于1%,峰面积的相对标准偏差小于5%,各离子的最低检测浓度为0.05 ̄0.5μg/ml。 相似文献
58.
Determination of rimantadine in pharmaceutical preparations by capillary zone electrophoresis with indirect detection or after derivatization 总被引:2,自引:0,他引:2
Summary Rimantadine is synthetic analog of amantadine; both are antiviral agents used for prophylaxis and treatment of influenza A.
A capillary zone electrophoretic (CZE) procedure for the determination of rimantadine has been developed. As the direct determination
of rimantadine is poorly sensitive because the compound is almost transparent in the UV/Vis range, several indirect methods
were studied. Two were found to be the particularly useful: (a) indirect detection using 5 mM 4-methylbenzylamine in 1:4 methanol-water
as absorbing background electrolyte, with detection at 210 nm, and (b) derivatization of rimantadine with 1,2-naphthoquinone-4-sulfonic
acid in alkaline medium and subsequent determination of the derivative by CZE (40 mM tetraborate, pH 9.2, detection at 280
nm). Uncoated capillary tubing, 44 cm length ×75 μM i.d., was used for both determinations. The detection limits were 0.1
and 2 ppm for methods a and b, respectively. The methods were used to determine rimantadine in pharmaceutical products and
for dissolution testing of Flumadin? tablets. 相似文献
59.
Summary Recently much attention has been directed to the validation of analytical methods. The level of validation will depend on the method application. If a method is developed for general use, for instance by different analysts, instruments or laboratories, then the effect of these changes need evaluation. This is normally referred to as ruggedness testing, where the limitations of the method to changes in the specified conditions are examined.This paper examines the use of Plackett-Burman fractional factorial experiment designs for ruggedness testing in high performance liquid chromatography (HPLC). The ability of these designs to identify confounding effects is applied to the stability indicating analysis of Salbutamol and its major degradation product, AH4045. The results show that confounding effects, proving extremely pertinent to HPLC, can be identified.The assay proved rugged to most tested changes although not to the use of column packing material from different manufacturers. 相似文献
60.
Summary Retention models for ionic compounds in reversed-phase ion-pair chromatographic systems have been developed on the basis of
the capacity ratios of solutes and ionic mobile phase components using indirect detection. The binding to the adsorbent, μBondapak
Phenyl, has been expressed by ion-pair distribution constants and tested in the retention models by non-linear regression.
All the ionic compounds followed adsorption models of the Langmuir type comprising two kinds of binding sites with widely
different adsorption capacities and binding constants. The results indicate certain differences between the two sites regarding
the binding of cationic and anionic components, respectively. 相似文献