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

Rodrigo C Bolzan,Julio Cezar P De Mattos,Valderi L Dressler,Érico M De Moraes Flores,Diogo P De Moraes

doi:10.1590/s0103-50532010000400015

Abstract

A method for arsenic determination in pharmaceutical grade BaSO4 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 μg 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 BaSO4 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.

Highlights

Barium sulfate is a raw material widely used in pharmaceutical industry for production of suspensions for radiographic templates
According to pharmacopoeical recommendations the limit test for heavy metals should be performed by extraction in open vessels with diluted acid solution before the reaction with sulfide.[1,2]
This procedure is prone to several drawbacks as (i) risks of contamination and analyte losses; (ii) limit test is not specific for As, but gives only general information based on color appearance for a group of elements; (iii) lack of accuracy and sensitivity; (iv) time consuming, and (v) use of unstable reagents

Summary

Introduction

Barium sulfate is a raw material widely used in pharmaceutical industry for production of suspensions for radiographic templates. In the literature only one study was found related to As determination in a similar matrix used in the present work.[26] Authors demonstrated the feasibility of D2-SoS-ET AAS for trace element analysis in barytes (a mineral basically constituted by BaSO4) They found that concentrated nitric acid could be used as chemical modifier for As determination. Calibration was performed using solid reference materials having different matrix composition (soil or sediments) Based on these considerations, in this work a comparison of the performance for two instruments equipped with deuterium or Zeeman-effect BG correction systems was performed in order to develop a method for As determination in pharmaceutical grade BaSO by SoS-ET.

Procedures

Results and Discussion

Conclusions