The Sample Pretreatment Method For Detecting Heavy Metal Of Carbohydrate Agriculturl Produces By ELISA

With frequent food safety problem in recent years, the traditional testing technologies of food safety become more tedious, more time-consuming and more difficult to do detection in field. Enzyme-Linked Immunosorbent Assay (ELISA) kit as a rapid, reliable detection method has been applied to solve some disadvantages of the traditional testing technology. But ELISA kit can only detect the liquid free iron of heavy metals, in view of this situation, it would be of realistic and far-reaching significance to develop an efficient, fast, easy sample pretreatment method based on ELISA .The optimum pretreatment conditions for Cu, Pb and Cd in vegetables such as Chinese cabbage (Brassica campestris L. sub. Chinensis var. utilis Tsen et Lee), carrot(Daucus carota var. L. sativa Hoffm.) and pumpkin(Cucurbita moschata (Duch. ex Lam.) Duch. ex Poir.) were studied with the extracting agent of three dilute acid (HCl, HNO3 and H2SO4). The results showed that the optimum pretreatment conditions were performed as follow: 40℃for 20min with 2.0M HCl, and the extraction rate was 64~98% as compared with the National standard method of microwave digestion; 40℃for 10min with 2.0M HNO3, and the extraction rate was 61~100% as compared with the National standard method; 25℃for 20min with 2.0M H2SO4, and the extraction rate was 57~100% as compared with the National standard method. And for Cu and Cd in Chinese cabbage and Cu in pumpkin, HCl has better extraction rate, the extraction rate was 87~98%; for Cu, Pb and Cd in Chinese cabbage and Cu and Cd in pumpkin, HNO3 has the best extraction rate, the extraction rate was 90~100%; for Cu in Chinese cabbage, carrot and pumpkin and Cd in Chinese cabbage and carrot, H2SO4 has better extraction rate, the extraction rate was 81~100%, all of them could substitute for the traditional pretreatment methods.The optimum pretreatment conditions of Cu, Pb and Cd extraction for fruit such as apple(Malus pumila Mill.), grape(Vitis vinifera L.) and banana(Musa paradisiacal L.) were investigated with the extracting agent of three dilute acid (HCl, HNO3 and H2SO4) ,too. The results showed that the optimum pretreatment conditions were performed as follow: 25℃for 15min with 2.0-4.0M HCl, and the extraction rate was 57~96% as compared with the National standard method; 70℃for 20min with 4.0M HNO3, and the extraction rate was 55~99% as compared with the National standard method; 4℃for 20min with 4.0M H2SO4, and the extraction rate was 54~96% as compared with the National standard method. And for Cu and Cd in apple and Cu in grape and banana, HNO3 has better extraction rate as well as HCl and H2SO4, the extraction rate were 84~100%, 83~96%,81~96%,respectively; for Cd in grape and Pb in apple, H2SO4 has better extraction rate, the extraction rate were 83%, 85%, respectively, all of them could substitute for the traditional pretreatment methods.The optimum pretreatment conditions of Cu, Pb and Cd extraction for grain such as rice(Oryza sativa L.), wheat(Triticum aestivum L.) and brown rice(Oryza sativa L.) were also investigated with the extracting agent of three dilute acid (HCl, HNO3 and H2SO4) . The results showed that the optimum pretreatment conditions were performed as follow: 25℃for 20min with 2.0M HCl, and the extraction rate compared by the National standard method was 37~57%; 4℃for 20min with 2.0M HNO3, and the extraction rate compared by the National standard method was 30~72%; 25℃for 20min with 4.0M H2SO4, and the extraction rate compared by the National standard method was 17~66%. And for Cu, Pb and Cd in rice and brown rice and Cu and Pb in wheat, HCl was of more than 50% extraction rate; for Cu and Cd of rice, wheat and brown rice and Pb in brown rice, HNO3 was of more than 50% extraction rate; for Cu in rice, wheat and brown rice and Pb in rice, H2SO4 was of more than 50% extraction rate. The standard recovery test shows that, the recovery rates of Cu, Pb and Cd in vegetables, fruits and grains extracted by dilute HCl were 69~104%, 76~105%, 78~100%, which is slightly lower than the National standard method; the recovery rates of Cu, Pb and Cd in vegetables, fruits and grains extracted by dilute HNO3 were 87~109%, 87~111%, 82~113%, which is close to the National standard method; the recovery rates of Cu, Pb and Cd in vegetables, fruits and grains extracted by dilute H2SO4 were 69~104%, 76~105%, 78~100%, which was also close to the National standard method, the above results verify the reliability of acid extraction.Finally, The both group data of Cu concentrations of carbohydrate produces, extracted with dilute acid pretreatment method, and determined by graphite furnace atomic absorption spectrometry(GF-AAS) method and ELISA assay respectively, were significantly correlated(R2=0.9515), this showed that dilute acid pretreatment method could meet the requirements of detecting heavy metals(Cu, Pb and Cd) of carbohydrate produces with ELISA kit.