Peristaltic pumps and Fourier transforms in flame atomic absorption spectrometry: use of standard additions method and on-line dilution procedures

The use of periodically pulsed peristaltic pumps to introduce samples in flame atomic absorption spectrometry allows the signal obtained during the sampling time to be treated with Fourier transform. In this work two applications of this methodology are presented: the standard additions method and the on-line dilution of the sample. In both cases two peristaltic pumps are used. For the standard additions method, the process is carried out in two experiments using three standards. The developed procedure has been applied to copper, calcium and chromium determination in the presence of several interferents. The RSD and accuracy were lower than +/- 2% and 5%, respectively. The second application permits high on-line dilutions of sample. In this case, two periodically pulsed peristaltic pumps rotate in opposite ways. This method and the use of 0.5 mm id tubes and a sampling time of 13 s, permits copper concentrations as high as 2000 mug ml(-1) to be determined.