Detection Of Cartap Residues In Vegetables By Water-soluble CdTe QDs Capped With Thioglycolic Acid

Cartap is a highly efficient insecticide widely used in modern agricultural production,and the overuse of cartap has also caused the problem of residue in fruits and vegetables.Most of the existing methods of detection of cartap require complex pre-treatment processes,expensive equipment,professional technicians,cumbersome operating procedures,time-consuming,and not suitable for on-site rapid detection.In this paper,the water-soluble Cd Te quantum dots capped with thioglycolic acid(TGA)and gold nanoparticles were proposed to detect cartap in vegetables based on inner filter effect(IFE).This study included the following two aspects:(1)The water-soluble Cd Te quantum dots capped with thioglycolic acid were prepared by aqueous phase synthesis method and used as a fluorescent probe to detect the residues of cartap.The maximum fluorescence emission wavelength of the purified Cd Te quantum dots was at 540 nm,and the fluorescence quantum yield was high and the optical properties were stable.The positively charged cartap and the negatively charged quantum dots are adsorbed by electrostatic attraction,which can cause significant quenching of the quantum dots fluorescence,whereby qualitative and quantitative detection of the cartap could be carried out.The method is very simple,and the selectivity is good and the sensitivity is high.Under the optimum conditions,the linear range was 1~10 ?g/m L,and the detection limit was 0.167 ?g/m L.The method was applied to the detection of the cartap in the real sample Chinese cabbage,and the recovery rate was high.Other substances in Chinese cabbage did not interfere with the detection of the cartap.(2)The water-soluble Cd Te quantum dots capped with thioglycolic acid were prepared by aqueous phase synthesis method.The cartap residues were determined by the combination of Cd Te quantum dots and gold nanoparticles based on inner filter effect(IFE).Gold nanoparticles have a strong fluorescence inhalation effect on Cd Te quantum dots.When there is no cartap in the detection system,the fluorescence emission of Cd Te quantum dots is weak and even quenched.When the cartap is present,it is combined with the gold nanoparticles by electrostatic adsorption,which makes the gold nanoparticles aggregate.At this time,the inner filter effect is obviously weakened or even disappeared,which makes the fluorescence emission of Cd Te quantum dots recover.Accordingly,qualitative and quantitative analysis of the cartap can be carried out.The method has the advantages of high stability,good selectivity and high sensitivity.Under the most conditions,the linear range of this method is 0.01~0.50 mg/kg and the detection limit is 8.24 ?g/kg.The method was applied to the detection of the cartap in the real sample Chinese cabbage,and the results were compared with GC-MS.The results were found to be accurate,the recovery rate was high,and the other substances in Chinese cabbage did not interfere with the detection of the cartap.In this paper,the water-soluble Cd Te quantum dots capped with thioglycolic acid as the fluorescent probe were used to detect the residues of the cartap in vegetables.At the same time,a new type of method was carried out in the detection of cartap by combination the gold nanoparticles and the Cd Te quantum dots based on the inner filter effect.The two methods established in this paper are simple,time-saving and labor-saving,good selectivity and high sensitivity.It is suitable for rapid detection in the field.It has great potential in the detection of the cartap residue in real samples such as fruits and vegetables.