Desenvolvimento de método para determinação de Cl- e SO42- em medicamentos contendo carbonato de cálcio

Abstract

In this work, a new method for determination of Cl- and SO42- in calcium carbonate active pharmaceutical ingredient (API) and medicine by ion chromatography (IC) is proposed. In the limit tests recommended by Brazilian Pharmacopoeia (BP), the API is dissolved in acid medium and the determination is performed by visual comparison between the opalescence of the sample and a standard solution after the addition of precipitating reagents standard solution. Despite its relative simplicity, the tests are monoelementar, semi-quantitative and some factors such as the visual acuity analyst and the brightness of the workplace can influence the final result. For the proposed method, the microwave-induced combustion (MIC) was evaluated for the volatilization of the analytes from the matrix through the energy provided by volatilization aid. For optimization, several parameters such as sample mass, volatilization aids, absorption solution and reflux step were evaluated. Additionally, the CaCO3 API and medicine were prepared by microwave assisted extraction using H2O as extracting solution and the analytes determination were performed by IC. Moreover, the ion-selective electrode potentiometry and ultraviolet/visible spectroscopy were evaluated to determination of Cl- and SO42-, respectively. Thus, after selected the best conditions of the proposed method by MIC (100 mg of API mixed with 300 mg of starch as volatilization aids, using HNO3 100 mmol l-1 as the absorbing solution, and 5 min reflux) the analytes were determined by IC. The accuracy of the results was evaluated by recoveries tests using a standard solution. Moreover, the API and a certificate reference material (CRM) NIST 1515 (Apple Leaves), were mixed as a recovery test. The recoveries obtained in both cases were adequate and ranged from 95 to 104% for Cl- and ranged from 83 to 90% for SO42-. The results showed good precision (RSD ≤ 9%) and LODs for Cl- and SO42- from 45 and 142 mg kg-1, respectively. After the optimizations, five API from different manufacturers were analyzed using the proposed method. Furthermore, the method was also applied to three medicines (different brand and batches) recommended for the treatment of gastric hyperacidity and calcium supplementation on body. The accuracy for medicines was evaluated by recoveries tests. The medicine and a CRM NIST 1547 (Peach Leaves) and a NIST 8433 (Corn Bran) were mixed for evaluated the accuracy for Cl- e SO42- concentrations, respectively. Suitable recoveries was obtained in both cases (103 and 91% for Cl- and SO42-, respectively). In respect to the results, the concentration of Cl- and SO42- are in agreement with maximum limits recommended by BP.