Arsenic determination in pharmaceutical grade barium sulfate using direct solid sampling electrothermal atomic absorption spectrometry

Abstract

Um método para determinação de arsênio em BaSO 4 por espectrometria de absorção atômica com aquecimento eletrotérmico e introdução de amostras sólidas (SoS-ET AAS) é descrito. Foram avaliados dois sistemas de correção de fundo (BG), deutério e efeito Zeeman (Z). Com o uso combinado de hidrogênio e Pd o BG foi diminuído. Resultados exatos e precisos foram obtidos usando Z-SoS-ET AAS. O desvio padrão relativo usando Z-SoS-ET AAS foi menor que 9,5%. O limite de detecção foi 0,005 mg g -1 e a massa característica foi 25,4 pg. Os resultados foram comparados com os obtidos usando o método de preparo de amostras sugerido pela Farmacopeia Europeia, com determinação usando espectrometria de emissão ótica e espectrometria de massas, ambos com plasma indutivamente acoplado, porém os resultados foram cerca de 20% menores. Vantagens como simplicidade, elevada frequência de determinações e boa exatidão foram obtidos em comparação com o método descrito na farmacopeia.A method for arsenic determination in pharmaceutical grade BaSO 4 by solid sampling electrothermal atomic absorption spectrometry (SoS-ET AAS) is described. Two background (BG) correction systems, deuterium and Zeeman-effect (Z), were evaluated. Background was decreased by using hydrogen combined with Pd. Accurate and precise results were obtained using Z-SoS-ET AAS. Relative standard deviation using Z-SoS-ET AAS was lower than 9.5%. Limit of detection was 0.005 mg g -1 and characteristic mass was 25.4 pg. Results were also compared with those obtained using the preparation method suggested by European Pharmacopoeia for BaSO 4 followed by determination using inductively coupled plasma optical emission spectrometry and inductively coupled plasma mass spectrometry. Results were around 20% lower than results obtained using the proposed method. Some advantages as simplicity, higher sample throughput were found when compared with the official method currently described in pharmacopoeia.

Feasibility of Direct Solid Sampling for Arsenic Determination in Sulfur-Containing Active Pharmaceutical Ingredients by Gf Aas

“…Thus, 1300 and 2400 °C were selected as pyrolysis and atomization temperatures, respectively, for As determination in hydrochlorothiazide by DSS-GF AAS. These temperature parameters were partially in agreement with those reported in previous works suggesting 1300 and 2200 o C for pyrolysis and atomization temperatures, respectively, for As determination using Pd as chemical modifier [20,[34][35][36].…”

“…The effectiveness of hydrogen as chemical modifier (0.5 L min -1 added as additional gas) was evaluated by adding during the pyrolysis step combined with the use of 6 μg Pd. The amount of chemical modifier was based on the conditions described in the literature [20]. Additionally, the suitable sample mass range (from 0.1 to 3 mg) that can be used for As determination was also investigated [30].…”

“…In all experiments the use of Pd (6 μg) as chemical modifier was performed taking into account its effectiveness in the As determination in a wide variety of samples [20,33]. Preliminary studies showed the need of a cool down step (100 °C, 15 s) before atomization to impair further interference caused by matrix vapors formed during the pyrolysis.…”

“…Using DSS-GF AAS, problems related to unsuitable LODs or difficulties on sample digestion can be solved [12]. This technique has been applied for trace elements determination at low levels in a wide range of samples [17][18][19][20][21][22][23][24][25] taking into account the following features as i) it practically avoids sample pretreatment step, ii) low contamination risk, iii) low risk of analyte loss, and iv) the use of corrosive and hazardous chemicals is avoided. Thus, the use of DSS-GF AAS for As determination at low levels in pharmaceuticals could present advantages over the techniques based on wet digestion for further As determination.…”

“…However, the application of chemical modifiers, careful adjustment of heating program and the use of an efficient BG correction system (e.g., Zeeman effect), generally are able to provide suitable GF AAS measurements [18,27]. Hydrogen has also been proved to be effective to reduce the BG [20,23,28] and/or to improve the effectiveness of Pd as chemical modifier [29], making feasible the analysis by DSS-GF AAS. However, this approach was still not applied to the determination of As in organic SC-APIs.…”