Bromine and iodine determination in active pharmaceutical ingredients by ICP-MS†
A method based on microwave-induced combustion (MIC) was applied for digestion of active pharmaceutical ingredients (APIs) and subsequent determination of bromine and iodine by inductively coupled plasma mass spectrometry (ICP-MS). Ten APIs including amoxicillin, atenolol, clavulanic acid, clonazepan, diltiazem, haloperidol, imipramine, nimesulide, propranolol and sodium diclofenac were decomposed by MIC. Combustion of 500 mg of each API was possible in less than 30 s using 20 bars of oxygen as initial pressure. A single and diluted solution (50 mmol L−1 (NH4)2CO3) was used for the absorption of both analytes and a reflux step of 5 min was applied to improve analyte recoveries. Final digests were suitable to Br and I determination by ICP-MS. Accuracy was evaluated using certified reference materials and agreement better than 95 and 97% for Br and I was obtained, respectively. Results were also compared with those obtained by ion chromatography (IC). The carbon content in digests obtained after decomposition was lower than 500 mg L−1 avoiding interferences in the determination step for both techniques. With the use of MIC, up to eight samples could be processed simultaneously and only diluted solutions are required, minimizing reagent consumption and waste generation. The limits of detection for Br and I by ICP-MS were 0.02 and 0.001 μg g−1, respectively, that were considered suitable for the determination of these elements in the investigated active pharmaceutical ingredients.