| Heavy metals contamination was an important part of food safety issue. The important part of monitoring, supervision, prevention and quality control for security was good detection techniques and methods.Some limited indicators of heavy metals in different categories of food such as lead, cadmium and copper must be detected. New technique of on-site rapid detection, more economical and convenient, could not only achieve a high percentage of sample screening and truly reflect the contamination of heavy metals in food, but also benefit the monitoring of food quality control. Therefore, it was the research focus of concern.The electrochemical detection methods of lead, cadmium and copper in food were economical and simple relatively so that they were becoming hot spots of attention and research. Differential potentiometric stripping analysis (DPSA) was a kind of high-resolution electrochemical analysis of simplicity and high sensitivity for synchronous rapid detection multielement in comparing with other electrochemical analysis methods. Mini DPSA-1 was a instrument of single function and miniaturization volume, based on the many advantages of electrochemical method. Its biggest advantage was that the instrument itself and the cost of routine maintenance had been greatly reduced, while it would be helpful for enterprises and multi-level departments; In addition, combining with screen-printed carbon electrodes (SPCE), it could greatly reduce cost of sample testing, which was to be able to promote the use of electroanalytical chemistry trends. Therefore, the aim of this study was to develop a better kind of synchronization rapid detection technique for multielement in food, which maintained the original advantages of electrochemical methods and overcome its critical shortages. In this novel technique, Mini DPSA-1 instrument with SPCE was used for synchronization rapid detection of lead, cadmium and copper in food (tea, vegetable, seafood) by DPSA, while optimized microwave digestion method was used for samples pretreatment.This thesis mainly contains the aspects as follows:The first part summarized the status and hazards of heavy metals contamination in food, made an overview of conventional detection methods of heavy metals. Also, electrochemical analysis detection methods and their studys were introduced.The second part of the study developed a new technique using Mini DPSA-1 instrument, coupled to SPCE, and detected trace lead in tea by DPSA. Test conditions and instrument parameters were optimized. The interference of other elements for lead detection, the recovery and actual samples detection were tested, also. The experimental conditions were optimized as follows, supporting electrolyte was 0.08 mol/L pH 4.0 NH4Cl, Hg2+ concentration was 3×10-4 mol/L, deposition potential was -1.0 V, final potential was -0.2 V, deposition time was 180 s. The potentiometric stripping response for lead in digested tea samples following 3 min deposition was linear over the concentration range examined (10μg/L～380μg/L, r=0.9968) with detection limit of 1.38μg/L (S/N=3), while the equation was Y (s/V)= 3.4648X (μg/L)+ 39.911. No significant interference of various ions existed in the determination of lead (140μg/L). No significant difference existed after the rapid detection results were compared with those detected by GB method using t test. The recovery of different types of tea samples was reached 88.3% to 97.7%. So, rapid detection technique developed for trace lead in tea, using Mini DPSA-1 instrument, coupled to SPCE by DPSA, was cheaper and more convenient in comparing with conventional detection technique. It could achieve a high percentage of sample screening and truly reflect the content of lead in tea.The third part established rapid technique using Mini DPSA-1 instrument with SPCE for synchronization determination of lead, cadmium and copper in tea by DPSA. The optimized experimental parameters were as follows, supporting electrolyte was 1.5 mol/L pH 4.0 NH4Cl, Hg2+ concentration was 3×10-4 mol/L, deposition potential was -1.1 V, final potential was -0.2 V, deposition time was 200 s. The potentiometric stripping responses for lead, cadmium and copper following 200 s deposition were linear over the concentration range examined (20μg/L～840μg/L) with regression coefficient of 0.99749,0.99740 and 0.99612 and detection limit of 1.12μg/L,1.09μg/L and 1.23μg/L (S/N=3), respectively. The equations of lead, cadmium and copper were Y (s/V)= 3.57189X (μg/L)+101.01566, Y (s/V)= 1.97376X (μg/L)-4.43362, Y (s/V)= 5.71248X (μg/L)-202.0041, respectively. No significant interference of various ions existed in the determination of lead, cadmium and copper (140μg/L). In addition, microwave digestion was used for sample pretreatment and the digestion parameters were also optimized. The recoveries of lead, cadmium and copper by testing different types of tea samples were 89.6%～97.7%,86.7%～100.7%,89.6%～98.9%, respectively. No significant difference existed after the rapid detection results were compared with those detected by industrial standard method using t test. Therefore, in comparing with conventional detection technique, this detection method for lead, cadmium and copper in tea, using Mini DPSA-1 instrument, coupled to SPCE by DPSA, was a cheaper rapid detection technique. It could achieve a high percentage of sample screening and truly reflect the contents of lead, cadmium and copper in tea.The forth part was to optimize digestion parameters of sample pretreatment. The experiment optimized digestion parameters of vegetable, then, twenty six kinds of different vegetables were detected by the synchronization detection technique established in part three. The optimized digestion parameters were as follows,0.3 MPa,2 min; 0.6 MPa,1 min; 1.0 MPa,1 min; 1.5 MPa,4 min. Under optimized condition, the linearity was from 1μg/L to 840μg/L (equivalent to contents of lead, cadmium and copper in vegetable from 0.0125 mg/kg to 10.5 mg/kg). The detection limits of lead, cadmium and copper in vegetable were 0.42μg/L,0.34μg/L,0.76μg/L, respectively. The recoveries of lead, cadmium and copper were 93.33%～99.20%,92.67%～96.33% and 95.91%～99.48%, respectively. No significant difference existed after the rapid detection results were compared with those detected by GB method using t test. Therefore, this detection method for lead, cadmium and copper in vegetable, using Mini DPSA-1 instrument, coupled to SPCE by DPSA, was a cheaper rapid synchronization detection technique. It could achieve a high percentage of sample screening and truly reflect the contents of lead, cadmium and copper in vegetable.The fifth part was to optimize digestion parameters of seafood sample pretreatment. Then, fifteen kinds of different seafood were detected by the synchronization detection technique established in part three. The optimized digestion parameters were as follows,0.3 MPa,2 min; 0.6 MPa,1 min; 1.0 MPa,1 min; 1.5 MPa,1 min,2.0 MPa,3 min. Under optimized condition, the linearity was from 1μg/L to 840μg/L (equivalent to contents of lead, cadmium and copper in seafood from 0.05 mg/kg to 42 mg/kg). The detection limits of lead, cadmium and copper in seafood were 0.47μg/L,0.32μg/L and 0.89μg/L, respectively. The recoveries of lead, cadmium and copper were 90.61% 102.96%,84.36%～104.33% and 85.41%～105.02%, respectively. No significant difference existed after the rapid detection results were compared with those detected by GB method using t test. Therefore, this synchronization detection method for lead, cadmium and copper in seafood, using Mini DPSA-1-SPCE by DPSA, was a cheaper rapid detection technique. It could achieve a high percentage of sample screening and truly reflect the contents of lead, cadmium and copper in seafood.The sixth part was summary and prospects of the thesis.
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