Revealing the Kinetic Advantage of a Competitive Small-Molecule Immunoassay by Direct Detection
ANALYTICAL CHEMISTRY
Authors: Tran, Renee J.; Sly, Krystal L.; Conboy, John C.
Abstract
Small-molecule detection in an immunoassay format generally employs competition or labeling. A novel direct-detection label-free primary immunoassay utilizing second harmonic generation (SHG) has been developed and the utility of the method has been demonstrated for several small-molecule narcotics. Specifically, the binding of morphine, methadone, and cocaine to antimorphine, antimethadone, and anticocaine antibodies was measured by SHG, allowing binding affinities and rates of dissociation to be obtained. The SHG primary immunoassay has provided the first kinetic measurements of small-molecule hapten interactions with a receptor antibody. The kinetics reveal for the first time that competitive immunoassays achieve their selectivity by taking advantage of the kinetics of association and dissociation of the labeled and unlabeled target and nontarget small-molecule to the capture antibody. In particular, the induced fit of the target small-molecule to their antibody pairs prolongs their residence time, while the nontarget small-molecule dissociate rapidly in comparison.
Simultaneous ozonation of 90 organic micropollutants including illicit drugs and their metabolites in different water matrices
ENVIRONMENTAL SCIENCE-WATER RESEARCH & TECHNOLOGY
Authors: Zoumpouli, Garyfalia A.; Souza, Fernanda Siqueira; Petrie, Bruce; Feris, Liliana Amaral; Kasprzyk-Hordern, Barbara; Wenk, Jannis
Abstract
The ozonation of 90 chemically diverse organic micropollutants (OMPs) including four classes of illicit drugs and their metabolites was studied in pure buffered water, tap water and wastewater effluent at three specific ozone doses and three pH levels. The second order rate constants for the reaction of 40 OMPs with ozone were known and span across 8 orders of magnitude, from below 1 M(-1)s(-1)to above 10(7)M(-1)s(-1). 47 of the tested OMPs were removed to at least 90% at the highest specific ozone dose of 0.3 mM O(3)per mM C at pH 7. However, most illicit drugs, including cocainics, amphetamines and ecstasy-group compounds, were ozone-resistant due to their lack of ozone-reactive functional groups. Exceptions included some opioids and the cocaine biomarker anhydroecgonine methylester which contain olefinic bonds and/or activated benzene rings. Different removal trends at different pH for OMPs were due to the combined effect of target compound speciation and ozone stability, leading to elimination of less than 70% for all OMPs at pH 11. In both tap water and wastewater effluent scavenging by matrix components led to lower ozone exposure compared to pure buffered water and consequently lower removal of OMPs. This multi-compound ozonation study utilised liquid chromatography-mass spectrometry to provide a large dataset on the removal of environmentally relevant OMPs, including those of interest for drinking water regulations. Besides including pharmaceutically active compounds that have not been studied with ozone before (e.g.gliclazide, anhydroecgonine methylester, quetiapine, 6-monoacetylmorphine), this study simultaneously shows ozonation data for a wide range of illicit drugs.