Implementation of an automatic standard addition method in a flow-batch system: application to copper determination in an alcoholic beverage by atomic absorption spectrometry

A novel strategy for implementing the automatic standard addition method (SAM) is described. By using a flow-batch system that presents the intrinsic favourable characteristics of the flow and batch techniques, the proposed strategy performs fast standard additions with sufficient flexibility and versatility and employs only one standard solution per analyte. To calculate the analyte concentration, a mathematical model based on a classical SAM and flow variables of the system was developed. The proposed flow-batch SAM was applied to copper determination by flame atomic absorption spectrometry (AAS) in sugar cane-made alcoholic beverages, known as "Cachaca", available in Brazil. A SAM has been recommended for these analyses because "Cachacas" presents a significantly different composition causing matrix effects and copper determination by calibration using matrix-matching standards can yield inaccurate results. The results show good agreement between the obtained values with the proposed flow-batch SAM and a manual SAM. The mean relative errors and overall standard deviations were always < 1.0% (n = 6) and 0.2 mg l(-1), respectively, for 1.0-7.0 mg l(-1) Cu. By using five standard addition levels, the sample throughput was 70 h(-1) and the consumption of sample and standard solution were 1.5 and 0.5 ml per analysis, respectively. (C) 2003 Elsevier Science B.V. All rights reserved.