Ultrasonic-assisted Enzymatic Digestion For Heavy Metal In Biologic Samples And The Study Of Detecting By Atomic Fluorescence Spectrometry

In this paper, the main method of sample pretreatment was illustrated in detail. The ultrasonic-assisted enzymatic digestion approach was highlighted. Then the principle,application and development trend of electrochemical vapor generation technique had been summarized. The research work consisted of ultrasonic-assisted enzymatic digestion for heavy metal in biologic samples and detection approach by atomic fluorescence spectrometry. The main contents of this paper were as follows: First, the study and application of ultrasonic-assisted enzymatic digestion. Second, various experimental parameters on the detection of As?III??Se?IV??I-Hg and Me-Hg were optimized. Some biologic samples were also analyzed. The details are listed as follow:Firstly, ultrasonic bath assisted enzymatic digestion As?III? and Cd in glutinous flours samples was studied. The influence of amounts of enzyme and extracting agent,ultrasound conditions were also investigated. The extraction efficiency was only 55%compared with microwave extraction. Then dual-frequency ultrasonic system was established by combination of an ultrasonic bath and an ultrasonic probe device,which can improve extraction efficiency greatly. Under the optimized conditions, the detection limit?3?? of As?III? and Cd were 0.0096 ?g L-1 and 0.0063 ?g L-1,respectively. RSD?n=11? was 2.2% and 3.8%, respectively. To improve enzymatic digestion efficiency, the dual-frequency ultrasonic-assisted approach was employed to study As?III? and Cd in flour samples.Secondly, the electrochemical vapor generation behavior of As?III??As?V??Se?IV?and Se?VI? were studied by using L-Cys-modified carbon paste electrode?L-Cys/CPE?as working electrode. The results indicated that the atomic spectral signal of As?III?and Se?IV? at L-Cys/CPE electrode significantly enhanced 3 time of that at graphite electrode. At the same time, L-Cys/CPE electrode has long service life of more than100 h. Under optimum condition, the detection limit?3?? of As?III? and Se?IV? could reach 1.26 ?g L-1 and 3.35 ?g L-1, respectively. RSD?n=11? were 3.4% and 4.2%,respectively. And the recovery rate was 96.8 %¹02.8 % and 92.3%¹04%,respectively. Therefore, the new method for detecting As?III? and Se?IV? based on EVG-AFS of L-Cys/CPE electrode has been established. This novel method has the advantage of high sensitivity, accuracy and precision. Moreover, it has overcome theproblem that lifetime of previous modified electrode was too short. We also successfully determinated As?III? and Se?IV? in traditional Chinese medicine samples by this method.Finally, HAuCl₄-modified electrode?Au-GE? was used as working electrode to explore the electrochemical vapor generation behavior of I-Hg and Me-Hg. The research shows that I-Hg can convert to vapor Hg0 individually in 1.6 mol L-1HCOOH, while both I-Hg and Me-Hg can convert to vapor Hg0 directly in 1.2 mol L-1HCl. As a result, we has established a high efficiency method for mercury speciation analysis on Au-GE modified electrode. This system has been applied satisfactorily for the determination of trace Hg species in human hair samples.