A flow injection on-line displacement/sorption preconcentration and separation technique coupled with flame atomic absorption spectrometry for the determination of trace copper in complicated matrices

A novel flow injection (FI) on-line displacement/sorption preconcentration and separation technique coupled with FAAS was developed for the determination of trace copper in complicated matrices. The methodology involved on-line formation of lead diethyldithiocarbamate (Pb-DDTC), pre-sorption of the resultant Pb-DDTC onto the inner walls of the knotted reactor (KR), retention of the analyte Cu-II on the inner walls of the KR through a displacement reaction between Cu-II and the sorbed Pb-DDTC and elution of the retained analyte with ethanol for FAAS detection. Interference from co-existing ions with lower stability DDTC complexes relative to Pb-DDTC were eliminated without need for any masking reagents in the proposed on-line displacement/sorption preconcentration system. The developed method was shown to tolerate up to greater than or equal to 250 mg l(-1) Fe-III, 40 mg l(-1) Cd-II, greater than or equal to 30000 mg l(-1) Zn-II, greater than or equal to 25000 mg l(-1) Mn-II and 10000 mg l(-1) Co-II in the sample digest. With 70 s of displacement/sorption at a flow rate of 6.0 ml min(-1), an enhancement factor of 155 and a detection limit (3s) of 0.38 mug l(-1) were obtained. The precision (RSD, n = 11) was 0.65% at the 50 mug l(-1) level and 3.3% at the 5 mug l(-1) level. The developed system was successfully applied to interference-free determination of trace copper in a variety of environmental and biological materials with high contents of co-existing heavy metals.