FLOW-INJECTION DILUTION SYSTEM FOR THE ANALYSIS OF HIGHLY CONCENTRATED SAMPLES USING FLAME ATOMIC-ABSORPTION SPECTROMETRY

A versatile computer-controlled flow injection manifold which extends the determination range of flame atomic absorption spectrometry is discussed. The system uses a peristaltic pump equipped with a small bore pump tube. While the pump is working at a low rate, a small volume of sample is metered into the system. Next, the pump rate is increased linearly with time. The inclusion of a T-piece before the nebulizer permits this device to be fed at a constant flow rate and an efficient dilution of the sample plug. Dilution of about 2000-fold can be obtained. Sampling frequencies are in the 40-120 samples h-1 range. By choosing appropriate pump rates and injection times, the problems posed by the pulsations due to the rollers of the peristaltic pump are overcome. Calibration can be performed by using peak height or integrated absorbance. Repeatability of the integrated absorbance measurements is in the 0.6-2.3% range.