Tesfaldet Zeriet O, van Staden Jacobus F, Stefan Raluca I
Department of Chemistry, University of Pretoria, Pretoria 0002, South Africa.
Talanta. 2004 Nov 15;64(4):981-8. doi: 10.1016/j.talanta.2004.04.026.
A simple and rapid, inexpensive spectrophotometric method was proposed for magnesium assay in pharmaceutical preparations by sequential injection analysis (SIA). The method is based on the reaction between o-cresolphthalein complexone (CPC) and Mg(II) in alkaline media, yielding a pink colored complex with absorption maximum at 570nm. Since the formation constant between Ca-CPC and Mg-CPC is similar, initially a sample/standard solution was aspirated into the holding coil followed by a mixture of masking-buffer solutions. This was done because masking of calcium should be accomplished before Mg-CPC complexation. Then the reagent was introduced into the reaction coil to produce a colored complex, which is measured spectrophotometrically at 570nm. In this way the interference of calcium was reduced. Furthermore, all the parameters that affect the reaction were evaluated. The calibration curve is linear over a range of 0-20mgl(-1) of Mg(II) with a detection limit of 0.24mgl(-1). A sample throughput of 80 samples per hour and relative standard deviation <2.0% were achieved. The proposed method was successfully applied for the assay of magnesium in three different compositions of pharmaceutical preparations (tablets). The results were found to be in good agreement with the manual flame atomic absorption spectrophotometry (FAAS) and UV-Vis spectrophotometry methods and with the claimed values by the manufactures. The t-test shows no significant difference at 95% confidence level.
提出了一种简单快速、成本低廉的分光光度法，用于通过顺序注射分析（SIA）测定药物制剂中的镁。该方法基于邻甲酚酞络合剂（CPC）与碱性介质中的Mg（II）之间的反应，生成一种在570nm处有最大吸收的粉红色络合物。由于Ca-CPC和Mg-CPC之间的形成常数相似，最初将样品/标准溶液吸入保持线圈，随后吸入掩蔽缓冲溶液的混合物。这样做是因为钙的掩蔽应在Mg-CPC络合之前完成。然后将试剂引入反应线圈以产生有色络合物，在570nm处进行分光光度测定。通过这种方式减少了钙的干扰。此外，对所有影响反应的参数进行了评估。校准曲线在0-20mg/L的Mg（II）范围内呈线性，检测限为0.24mg/L。实现了每小时80个样品的进样量，相对标准偏差<2.0%。所提出的方法成功应用于三种不同成分药物制剂（片剂）中镁的测定。结果发现与手动火焰原子吸收分光光度法（FAAS）和紫外可见分光光度法以及制造商声称的值非常一致。t检验表明在95%置信水平下无显著差异。
