Hyphenation Of Sequential Injection With Spectrometry For The Determination Of Trace Level Of Heavy Metals

Copper and manganese are indispensable micro-nutrients to human health at very low concentration levels, when exceeding a certain concentration threshold, they both become toxic to human health. Therefore, it is very important to develop quantitative protocols for the determination of trace copper and manganese in environmental and biological samples.In the first section of the paper, a comprehensive review about the analytical methods exploited in the quantitative assay of copper, manganese and the research techniques envolved in the separation/preconcentration of copper was introduced.In the second section, the selective retention of Cu2+ with silk fibroin at pH 6.0 was investigated and a novel on-line procedure for separation/preconcentration of Cu2+ from complex sample matrices was thus developed by using a sequential injection system with an electrothermal atomic absorption spectrometry. A novel concept of enrichment index(EI), i.e., defined as enrichment factor(EF) obtained by consuming unity of sample volume(mL), was proposed for evaluating the enrichment efficiency of a flow-based preconcentration procedure. With a sampling volume of 900μL, an El of 30.3(EF=27.3) was achieved, which was much improved as compared to that of reported procedures. A detection limit of 8.0 ng L-1 was achieved within a linear range of 0.025-1.5μg L-1 along with a precision of 2.2% RSD at 0.5μg L-1. The practical applicability of this procedure was validated by analyzing a certified reference material of riverine water(GBW08608) and a certified reference material of seawater(NASS-5) achieving satisfactory agreements between the certified and the obtained values. A spiking recovery was also performed by using a cave water sample.Based on National Standard Method of GB 11906-89, a simple, accurate spectrophotometric procedure for the determination of filtered manganese and total manganese was developed by exploiting sequential injection technique in the third section of this work. A thorough scrutiny has been made to investigate the effect of digestion conditions. Under the selected conditions, the filtered manganese could be quantified in the range of 0.02-3.0 mgL-1 along with a detection limit of 0.007 mg L-1 and a precision of 2.4% RSD at 1.0 mg L-1. For the total manganese, a calibration curve was obtained in the range of 0.1-30.0 mg L-1 with a detection limit of 0.03 mg L-1 and a precision of 1.2% RSD at 10.0 mg L-1. The present procedure was validated by spiking recoveries of manganese in river water, lake water, tap water and homemade water samples, and satisfactory results were obtained.The conclusions about the developed protocols were given in the last section.