Optimization of instrument conditions for the analysis for mercury, arsenic, antimony and selenium by atomic absorption spectroscopy

The chemical vapor generation atomic absorption spectrometry technique is extremely popular for trace analysis specifically hydride generation continuous flow systems for arsenic, antimony, selenium and cold vapor for mercury. Optimizing the instrument parameters as well as the hydride generating reactions will improve the sensitivity and reliability of the results obtained. The advantage of optimizing these conditions increases the production of hydrides or vapor species formed thereby improving recoveries. In addition this helps to reduce chemical interferences from other species that may compete with the analyte of interest for hydride formation. Parameters optimized include: • Reagent flow rate; • Sample flow rate; • Argon flow rate; • Acetylene/Air ratio; • Concentration of reagents; • Read delay time. For the analytical procedure the flow rate of the reagents and sample was affected by the tension on the peristaltic pump and the size of the tubing. The optimized flow rate for all reagents was between 0.9–1.0 mL/min and between 6–7 mL/min for the sample when both conditions were applied. The optimized type and concentrations of the reducing agent for Arsenic, Antimony and Selenium were NaBH4 (0.6% w/v), NaBH4 (0.7% w/v) and NaBH4 (0.1% w/v) in NaOH (0.5% w/v) respectively and SnCl2 (25% w/v) in HCl (20% v/v) for Mercury. The concentration and type of acid that produced the optimum signals for Arsenic, Antimony and Selenium were 5, 10 and 10 mol/dm-3 respectively. The flow rates for the carrier gas (Argon) for Arsenic, Antimony, Selenium and Mercury were optimized at 0.2, 0.2, 2.0 and 2.0 mL/min respectively. The optimized flow rate for fuel gas (Acetylene) for all the metals except Mercury was 2.5 mL/min. The optimized Instrument Read Delay Time for Mercury was 70 s and 20 s for Arsenic, Antimony and Selenium.