Iodometric determination of milligram and microgram amounts of levocetirizine in pharmaceuticals

Four simple, selective and sensitive methods are described for the determination of levocetirizine dihydrochloride (LCT) in bulk drug and in tablets. The methods exploit the well-known analytical reaction between iodide and iodate in the presence of acid solution. Iodide present is oxidized by iodate in an amount equivalent to the HCl present in LCT to iodine and the liberated iodine is determined by four different procedures which inturn quantify LCT at varying detection range and sensitiveness. Two direct titrimetric procedures involve titration of iodine by thiosulphate either towards starch end point (method A) or potentiometrically (method B). Both the methods have a reaction stiochiometry of 1: 1 (LCT: liberated iodine) and have quantification ranges of 2–20 mg LCT for method A and method B. The liberated iodine is also measured spectrophotometrically at 350 nm (method C) or the iodine-starch complex measured at 570 nm (method D). In both the methods, the absorbance is found to be linearly dependent on the concentration of iodine which in turn is related to LCT concentration. The calibration curves are linear over 5–40 and 1.25–12.5 mg mL^?1 LCT for method C and method D, respectively. The calculated molar absorptivity and Sandel sensitivity values are 1.0 × 10⁴ L mol^?1 cm^?1 and 0.0435 mg cm^?2, respectively for method C, and their respective values for method D are 2.9 × 10⁴ L mol^?1 cm^?1 and 0.0156 mg cm^?2. The intra-day and inter-day accuracy and precision studies were carried according to the ICH guidelines. The method was successfully applied to the analysis of two brands of tablets LCT. The accuracy was also checked by placebo blank and synthetic mixture analyses besides recovery study via standard addition procedure.     

气相色谱法测定婴幼儿配方谷粉中的碘

建立婴幼儿配方谷粉中碘的气相色谱定量分析方法。样品经α-淀粉酶水解,利用乙酸锌和亚铁氰化钾作为沉淀剂将样品中的蛋白质除去,在硫酸环境中把碘离子氧化成碘,碘与丁酮反应生成3-碘代-2-丁酮,用正己烷萃取,气相色谱法定量检测。碘的含量在0.04~0.48μg/m L范围内与色谱峰面积呈现良好的线性关系,线性相关系数r=0.998 2,方法的检出限为90μg/kg。测定结果的相对标准偏差为3.49%(n=6),样品加标回收率为86.2%~95.6%。该方法具有较高灵敏度和准确度,适用于婴幼儿配方谷粉中碘含量的检测。     

Determination of total iodine in foods and dietary supplements using inductively coupled plasma-mass spectrometry

A method was developed and validated for the determination of total iodine in a wide variety of food products and dietary supplements. The method involves a unique sample digestion with a KOH solution in an oven or by using an open-vessel microwave system. After digestion, a stabilizer is added and the solution is taken to volume, then filtered and analyzed either directly or after dilution. The amount of iodine is determined with inductively coupled plasma-mass spectrometry (ICP-MS). The method was validated by experiments to determine its precision, accuracy, linearity, specificity, ruggedness, and robustness. The LOQ of this method is 25-50 microg/kg. The method demonstrated an average RSD of 2.27% during analysis of milk powder and 4.30% during analysis of a dietary supplement tablet reference material. The accuracy of the method as determined with these same reference materials was 100 and 94.2%, respectively. The method has been used successfully on commodity foods, processed foods, dairy products, pet food, infant formula, animal feed, mineral premixes, and a variety of dietary supplements.     

硫化物标定方法的改进

对HJ/T 200-2005中硫化物标定方法进行了改进。改进后的方法通过限制碘溶液加入后的硫酸加入速度,成功地控制了碘与硫化物的歧化副反应的进度,找到了影响硫化物标定方法准确度和精密度的因素。在乙酸锌的加入量为10 mL,碘溶液加入后的静置时间为0 s,硫酸的加入量为8 mL,反应时间为5 min的实验条件下,测定结果的相对标准偏差为0.45%~1.33%(n=6),样品的加标回收率为97.1%~99.6%。对改进后的方法进行t检验,没有显著的系统误差,该方法具有良好的准确度和精密度。     

灰化法-气相色谱法测定45种食品中的碘含量

以日常食品为研究对象,建立了气相色谱测定不同食品中碘含量的检测方法。样品经碳酸钾-硫酸锌灰化处理后,采用酸水溶解,以丁酮衍生后进行气相色谱分析。经DB-1701色谱柱(30 m×0.32 mm×0.25μm)分离,电子捕获检测器(ECD)测定,以保留时间定性,峰面积外标法进行定量。考察了不同灰化条件对结果的影响,并对方法的灵敏度、准确度和精密度进行验证。碘的检出限为1.0 ng·g-1,平均加标回收率为99.5%,相对标准偏差(RSD)为3.6%。该方法灵敏、准确、可靠,且分析时间短、抗干扰性好,可用于日常食品中碘安全的监测。     

A rapid spectrophotometric method for iodimetric α-amylase assay

A kinetic, two-point method for the assay of α-arnylase in serum, involving spectrohotometric measurement of a starch-iodine complex, is described. This approach avoids interferences by serum proteins and other substances that react with iodine. The method requires less than 4 min per assay, only 10 μl of sample is used, and precision and accuracy are comparable to those of established procedures.     

Determination of thiourea and its organic derivatives with iodine trichloride

Thiourea and its organic derivatives and thiosemicarbazide are determined in water, methanol or glacial acetic acid medium by reaction with an excess of iodine trichloride in the presence of mercuric chloride. The reaction is complete in 15 min. The excess of iodine trichloride is evaluated by adding potassium iodide and titrating the liberated iodine with thiosulphate. A variety of organic thioureas can be determined with an average accuracy and precision of 0.2%.     

Concentration of iodine traces in solution by filtering through activated carbon

The retention of iodine traces (ppb) was investigated in small activated carbon filters (50 mg) from solution at a yielding rate exclusively determined by pH. Retention is approximately 100% at pH values of 4–6, while no retention of iodine traces occurs after filtering them through an activated carbon filter from very acidic and basic solutions (pH values of 1 and 11, respectively) with 0% yielding rate. Since activated carbon is a very pure material, this procedure may be an alternative method of the activation analysis of iodine traces in foodstuffs, because the half-life of ¹²⁸I, formed by (n,g) reaction, is only 25 minutes. It does not allow either the sample to be placed readily in solution or the radioisotope to be separated after irradiation with the purpose of attaining maximal accuracy and sensitivity in this type of analysis.     

液相色谱法和淀粉-碘化镉法检测聚合物含量的对比

考察了液相色谱法检测聚合物含量以及聚合物分子量对测试准确性的影响,并对比了液相色谱法和经典的淀粉-碘化镉法检测结果的差异.利用液相色谱法可对干扰多、偏差大的油井产出液中聚合物含量进行准确测定.对于其它不同介质中聚合物含量的检测有一定的应用价值.     

Determination of iodine in biological materials and in some standard reference materials by X-ray fluorescence spectrometry

Summary A new method for the determination of iodine in biological samples is described. If series of samples of uniform matrix are to be analyzed no mineralization is required: water soluble iodide coprecipitated on a carrier and tissue-bound iodine are both collected on a filter and simultaneously determined by X-ray fluorescence thin layer technique. In the particular case of the determination of iodine in rat thyroids this procedure allows a satisfactory screening of drugs influencing the iodine balance. In the general case of trace iodine determination in quite different matrices the organic material is ashed prior to the precipitation and measuring step. The trace iodine content of several reference materials from NBS, BCR and IAEA obtained by this method is given.

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Iodbestimmung in biologischen Proben und einigen Standardreferenzmaterialien mit Hilfe der Röntgenfluoreszenzspektrometrie