FEASIBILITY OF DIRECT SOLID SAMPLING FOR ARSENIC DETERMINATION IN SULFUR-CONTAINING ACTIVE PHARMACEUTICAL INGREDIENTS BY GF AAS

A method for As determination in sulfur-containing active pharmaceutical ingredients (SC-APIs) by direct solid sampling graphite furnace atomic absorption (DSS-GF AAS) was developed. The proposed method was successfully applied to three SC-APIs (hydrochlorothiazide, furosemide and sulfadiazine). Palladium was used as chemical modifier as well as hydrogen during the pyrolysis allowing the direct determination of As in the SC-APIs without interferences caused by gaseous sulfur species. Sample masses (hydrochlorothiazide) from 0.4 to 3 mg were used and calibration with aqueous standard solutions was feasible. The limit of quantification was 0.033 mg g-1 and the calibration ranged from 0.1 to 1.6 ng As. Recoveries for As solutions added directly to the solid samples were between 95 and 103%, showing a good accuracy. The method validation highlighted its robustness, since variation in pyrolysis and atomization temperatures, as well as in Pd and sample masses, did not change significantly the results. Additional experiments showed that this method can be applied to other SC-APIs (as e.g., furosemide and sulfadiazine). Arsenic concentration in hydrochlorothiazide samples ranged from 0.13 to 0.48 mg g-1, while in furosemide and sulfadiazine samples it was from 0.49 and 0.54 mg g-1, respectively. The use of DSS-GF AAS does not require previous sample digestion and As could be directly determined in the solid samples providing some advantages, as lower risks of contamination and analyte losses, good accuracy and limits of quantification.