Multivariate optimization of a digestion procedure for bismuth determination in urine using continuous flow hydride generation and atomic fluorescence spectrometry

A sensitive method has been developed for the determination of bismuth in urine using continuous flow hydride generation and atomic fluorescence spectrometry (HG AFS). The conditions for bismuth hydride generation as well as some instrumental parameters were optimized using univariate methodology. Experimental conditions for sample digestion using nitric acid, hydrogen peroxide and a reflux system by “cold finger” were optimized employing a two-level full factorial design and a Box-Behnken design. Nitric acid used during sample preparation showed a negative effect on Bi determination by HG AFS, and a drying step was required after digestion. The established conditions for sample digestion allowed a low residual carbon content. Thus, the proposed method, using 5mL urine, allowed bismuth determination with limits of detection and quantification of 0.02 and 0.08μgL−1, respectively. Accuracy was assessed by the spike/recovery test using urine samples and the recoveries obtained varied from 91and 97%. Precision expressed as relative standard deviation (RSD) was lower than 10%. This method was satisfactorily applied for the determination of bismuth in five urine samples. The bismuth contents found ranged from 0.30 to 0.66μgL−1.