Study On Electrochemical Detection Method Of Heavy Metal Lead And Cadmium In Food

Lead, cadmium is a heavy metal which does not need in the human body. The accumulation of lead, cadmium is not easy to eliminate in the environment. Lead and cadmium enter the body through the food chain step by step.The excess saving of lead and cadmium is harmful to the function of human body. The accumulation of lead, cadmium in the body will cause the decrease of immunity and the damage of digestive system reproductive system and nervous system.It also can causes some physiological and pathological diseases,such as osteoporosis. It can even lead to cancer. Therefore, the detection of lead, cadmium in food is very important and necessary. The traditional detection of lead, cadmium is atomic absorption spectrometry. Microwave digestion technology is a pre-processing technique of sample.Because the detection method is laborious and the instrument is large and expensive. It can be only used in laboratory. It cannot get the result immediately. So choose the wet digestion as a pre-processing technique of sample. Electrochemical detect the contents of lead and cadmium in food samples.Food sample preparation choose wet digestion, Sample pretreatment is as follows: Dry sample in the agate mortar grind into powder, Through a 40 mesh sieve, Stored in a plastic bottle, cold storage for used. Fresh sample chopped by stainless knife or into homogenate by homogenate machine,Stored in a plastic bottle, cold storage for used. The optimum digestion conditions are as follows: nitric acid- hydrogen peroxide digestion system, without pre- digestion after adding 10 m L nitric acid at 120~140 and adding 10 ℃~ 15 m L of hydrogen peroxide during the heating process. Catch the acid temperature at about 140℃, The final residual digestion solution volume is about 1m L after catching the acid temperature at about 140℃.Select the differential pulse stripping voltammetry to detect lead, cadmium content in food. The optimum experimental parameters are as follows: The sensitivity is 10μA, the filter parameter is 10 Hz, the initial potential is-1.0V, the termination of potential-0.3V, potential increment is 0.005 V, pulse amplitude is 0.06 V, pulse width of 20 ms, Pulse width is 140 ms, the sample width is 10 ms, static time is 10000 ms, accumulation potential is-1.4V, accumulation time is 90 s. Lead peak is around-0.55 V, Cadmium peak is around-0.75 V when using electrochemical to detect food samples. The experiment shows that it presents a good linearity when the content of lead is at 0~2×10﹣5mg/m L. The correlation coefficient is 0.99, the precision is 1.93%, The detection limit was 1.1223 g/L. The experiment shows that it presents a good linearity when the content of cadmium is at the 0~1.6×10﹣5mg/m L. The correlation coefficient is 0.99, the precision is 3.84%, The detection limit was 0.1517μg/L. When compared with the national standard method, the electrochemical process’ s error rate of lead content test is 2.23%~27.59%. The error rate of cadmium content test is 3.86%~18.38%. I have detected the lead, cadmium content of some food such as millet by random purchase. The recovery was in the range of 82%~115%, which shows that the electrochemical method can be used for detecting the content of heavy metals lead, cadmium in food.According to the optimal experimental conditions which were determined, the electrochemical detection of lead, cadmium can be used in 25 kinds of vegetables and fruit samples. Experimental results: the lead content of lily is excessive, the 25 kinds of vegetables and fruit samples’ over standard rate is 4%. The lead content of mushrooms, Lily and cauliflower cadmium content are excessive, the 25 kinds of vegetables and fruit samples’ over standard rate is 12%.