In-sample stability and postsampling analysis of 21 illicit drugs, their metabolites and cotinine in wastewater.

A thorough understanding of the degradation of chemical biomarkers in wastewater after the sampling is critical in the surveillance of illicit drug use based on the back-calculation technique. Herein, three temperatures, eight groups of matrices, and acidification were applied to simulate the preservation condition of 21 illicit drugs, their metabolites, and cotinine for a 240-day stability study. It was proved that the temperature, matrices, and acidification play vital roles in their stability in wastewater. Most of them demonstrated high stability (transformation rates < 20%) during room temperature for 45 days, and the transformation rates decreased while the storage temperature reduced. The stability of the target compounds such as cocaine (COC), 6-monoacetylmorphine (6-MAM), and amphetamine (AM) is influenced by matrices. Acidification prevented the majority of analytes from transforming, making it a feasible solution for preservation after sampling. A model that combined the effects of temperature and matrix was developed to back-calculate the concentration of target compounds during the postsampling process. The feasibility of this model was validated by correcting the loss of COC and 6-MAM from 24.2% and 16.2% to 2.98% and 2.77%. This study simulated a typical large-scale sampling and storage scenario. The effect of the temperature, pH, and matrix on in-sample stability and the postsampling analysis of selected target compounds was investigated for the first time in this study.

Development of a one-pot and sequence-specific LAMP assay based on the self-quenching probe integrated by the complementary oligonucleotide for an enhanced fluorescence quenching.

Single-modified fluorogenic primer (Sfp) enables accurate identification of LAMP amplicons without being affected by non-specific products. However, the fluorescence self-quenching by nucleobases for Sfp is generally of low efficiency, and the high background signal makes it a great challenge to achieve visual inspection with naked eyes. In the present study, the oligonucleotide (Ao) complementary to Sfp was designed, which would hybridize to Sfp and dramatically heighten the quenching effect, leading to a low background signal in negative reaction. Instead, for positive reaction, Sfp is incorporated into the double-stranded amplicons, resulting in dequenching and consequently, enhanced fluorescence. The detection scheme can be further improved by a dual-color fluorescence strategy, allowing visual detection of 1 pg rainbow trout DNA in a closed-tube format within 30 min. Therefore, our LAMP-Ao-Sfp assay represents a useful tool for rapid and sensitive detection, and can serve as a reliable method for on-site detection in low-resource settings.