Sensitive fluorescence detection based on dimeric G-quadruplex combined with enzyme-assisted solid-phase microextraction of streptomycin in honey.

Streptomycin (STR), an aminoglycoside antibiotic with the potential to persist in honey and other food products, may induce allergy, toxicity and antibiotic resistance in humans. In this study, we developed a solid-phase microextraction (SPME) biosensor based on a quartz rod that was modified with double-stranded DNA structures consisting of partially complementary G-rich base DNA strand and STR aptamer. The STR isolated by SPME initially bound to the aptamer. Then the remaining double-stranded DNA structures were cleaved by the Nt.BstNBI enzyme, resulting in release of G-quadruplex dimers. The latter formed a complex with thioflain T fluorescent dye, resulting in an amplified fluorescence response. The method exhibited high sensitivity (a limit of detection of 10.84 pM), wide linear range (0.05 nM âˆ¼ 500 nM (with determination coefficient > 0.99)), and simple operation, making it suitable and convenient for STR detection. Successful STR determination in genuine honey samples was demonstrated.

[Determination of C1-C6 organic acids in the products from syngas to olefins by ion chromatography].

A method for the determination of C1-C6 organic acids in the products from syngas to olefins (SGTO) was developed by ion chromatography, which included the optimized separation conditions, the linear ranges and the working curves determined by using standard samples, the precision and accuracy of the method and the alkaline-washing conditions of the pretreatment for the oil phase samples. The SGTO water phase and oil phase samples were analyzed according to the method. The linearity test showed that the correlation coefficients (R2) for all of the C1-C6 organic acids in the specific concentration ranges were above 0.99, which means that all the components had good linear correlations. The recoveries of standard solutions were from 95.6% to 104.3%, and the RSDs (n = 5) were from 0.4% to 3.6%. The spiked recoveries in SGTO oil phase samples were from 91.1% to 96.8%, and the RSDs (n = 5) were from 0.7% to 2.3%. The accuracy of the method can satisfy the requirement for the analysis of SGTO samples. The results showed that there were more C2-C4 organic acids in the water phase samples, while there were more C4-C6 organic acids in the oil phase samples. This research has great significance for the study of SGTO reaction, the improvements of catalysts and operation conditions, and is helpful for choosing the materials of the equipment.