Development of an enzyme-linked immunosorbent assay specific to Sudan red I.

To obtain antibodies to develop an enzyme-linked immunosorbent assay (ELISA) for the analysis of Sudan red I, haptens were designed and synthesized via four different strategies: (i) attachment of a spacer at the para position of the benzene ring, (ii) attachment of a spacer at the naphthol part, (iii) attachment of a spacer at the hydroxyl group of the Sudan red I molecule, and (iv) use of a fragment of the target molecule. A total of 10 haptens were used to generate immunogens, coating antigens, and polyclonal antibodies. One of the heterologous ELISAs developed exhibited an IC(50) of 1.6 ng/ml, a limit of detection (LOD) of 0.03 ng/ml, and a dynamic range between 0.1 and 14 ng/ml. The assay had 13% cross-reactivity with Para red and negligible cross-reactivity with other structure-related compounds. This ELISA was much more specific than those published previously. This assay was used to determine Sudan red I residues in tomato sauce and chili powder samples after simple pretreatment. The results were validated by comparison with high-performance liquid chromatography (HPLC). The average recoveries of Sudan red I by ELISA and HPLC were in ranges of 70-97% and 82-114%, respectively, indicating suitability of the developed ELISA for screening of Sudan red I in foods.

Quantitative analysis of the neonicotinoid insecticides imidacloprid and thiamethoxam in fruit juices by enzyme-linked immunosorbent assays.

Rapid and sensitive ELISAs have been applied to analyze imidacloprid and thiamethoxam residues in apple, grape, orange, and peach juices after simple dilution of the samples without any extraction and cleanup. The matrix interference of the fruit juices was eliminated after 100-fold dilution, and the ELISAs gave method LODs of imidacloprid and thiamethoxam in fruit juices down to 20 and 5 ng/g, respectively. Average recoveries of imidacloprid and thiamethoxam from the spiked fruit juices were in the range of 92-115% and 87-118%, respectively. The CVs of the recoveries ranged from 3 to 19% and from 6 to 19% for imidacloprid and thiamethoxam, respectively. The ELISA results were comparable to those obtained by a reference HPLC/MS method using pesticide-spiked samples, with reasonable correlation coefficients between 0.89 and 0.93 and regression coefficients (slopes) between 0.75 and 0.94.

Alternative chiral thiols for preparation of chiral CdS quantum dots covered immediately by achiral thiols.

Developing of alternative chiral thiol stabilizers from the assembly of achiral thiol (e.g. thioglycolic acid) and chiral ligand (e.g. arginine) via both hydrogen bonding and electrostatic interactions was proposed and successfully applied to an efficient preparation of chiral CdS quantum dots (QDs). Chiral CdS QDs capped mainly with achiral thioglycolic acid were also obtained that may allow the chiral QDs to be modified for extended applications.