Standard dilution analysis using an automatic sampler and a peristaltic pump stopping step for ICP-OES determinations

Abstract

This work applies a semiautomated version of the standard dilution analysis calibration method (SDA) for the determination of Ba, Be, Cd, Co, Cr, Cu, Mn, Ni, V and Zn in several matrices (0.5 % m/v Ca, 0.6 % m/v Na, Vitamin Water, apple juice, red wine, and rum) by inductively coupled plasma optical emission spectrometry (ICP-OES). SDA utilizes only two calibration solutions: S1 is a mixture of 50% v/v sample and 50% v/v of a standard solution containing the analytes and an internal standard (IS1); S2 has a 1:1 mixture of sample and a blank solution containing a second internal standard (IS2). In the present study, S1 and S2 are mixed in the ICP-OES’s sample introduction tubing to create several calibration points on the fly. The SDA calibration process is semiautomated simply by creating an analysis sequence within the instrument’s software to move the automatic sampler from S1 to S2, while including a peristaltic pump stopping step between the two calibration tubes to prevent the formation of an air bubble. The semiautomated SDA method, which includes manual peristaltic pump stopping, provides precision corresponding to < 0.8% RSD, and LOD < 20 μg L-1 for all analytes, which is lower than values calculated for the traditional standard additions method (SA). Accuracy was evaluated by analyzing a reference material (EPA Water Pollution Standard 1) and by addition and recovery experiments (percent recoveries in the 96.3–109% range for all analytes evaluated). The SDA strategy provided comparable, and mostly superior accuracy when compared with the external standard (EC), internal standard (IS) and SA calibration methods applied to ICP-OES.