The most encountered situations in reversed-phase liquid chromatography for temperature dependence of retention are those obeying the linear equation known as the van't Hoff plot. When studying compounds that are involved in structural modifications, it is likely that the temperature dependences of their retention factors do not follow this rule. It is the aim of this paper to report some particular cases when compounds involved in tautomeric interconversion have a different retention behavior with temperature: a deviation from the linearity of ln k on 1/T, or, in certain temperature ranges, temperature increase leading to a retention increase. Examples of compounds exhibiting deviation from the van't Hoff temperature dependence are piroxicam, drotaverine, vincamine, and epivincamine. A simple thermodynamic model relying on tautomeric equilibria in mobile phase is proposed for these compounds, which gives a polynomial dependence between ln k and 1/T.

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The present study investigated the distribution and environmental fate of Bisphenol A (BPA), the 4‐hydroxyacetophenone (4‐HAP) metabolite, and 5 other bisphenol congeners in 2 municipal wastewater treatment plants (WWTPs) and their receiving rivers in Romania. Accordingly, a new, highly sensitive and accurate solid‐phase extraction–liquid chromatography–electrospray ionization–tandem mass spectrometry method was developed and validated. This technique generated low limit of quantitation values: below 2.3 ng/L for surface water and less than 2.4 and 2.7 ng/L for WWTP effluent and influent water. The sum of detected analytes in wastewater was between 1337 and 16 118 ng/L for influent samples and between 15 and 96 ng/L for effluent samples. In surface water, the total of all compounds was somewhere between 34 and 240 ng/L. The highest concentration observed was for BPA in all 3 types of analyzed water (up to 9140 ng/L for influent, as high as 75 ng/L for effluent, and a maximum of 135 ng/L in surface waters). All analyzed samples were free of bisphenols B, C, and F. For all analytes detected in surface water, the concentration values were higher than those determined in the effluent samples, which may be caused by intrinsic contamination of the 2 rivers (Danube and Jiu Rivers). Values of environmental risk coefficients, calculated for both effluents and surface waters, indicated a low ecological risk or no ecological risk for 3 types of organisms (algae, daphnia, and fish). Human risk assessment calculation suggests no risk to human health as a result of the presence of BPA in either of the 2 rivers. Environ Toxicol Chem 2021;40:435–446. © 2020 SETAC

The presence of pharmaceuticals in the aquatic ecosystem has received great attention from the scientific community in the last decades, due to their potential impact on living organisms. This paper presents a short review of the results of investigations performed by INCD-ECOIND concerning the occurrence of 32 pharmaceutical compounds belonging to important therapeutic classes and 2 disinfectants along the Danube River and its tributaries. Grab water samples were collected from multiple points along the River (10 sites) and from 2 locations for each of the tributaries Jiu, Olt and Argeș, upstream and downstream of large cities. All samples were quantified via solid phase extraction, followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Results of these studies show that various pharmaceutical compounds are present in the dissolved water phase of the Danube River and its tributaries in low to moderate amounts with variation due to season and location.

Occurrence and fate of 6 neonicotinoid insecticides belonging to different chemical classes were investigated in the aqueous phase of surface water at 16 sampling locations along the Romanian side of the Danube River and its three main tributaries (Jiu, Olt, Arges). This is the first report on the neonicotinoid occurrence in the Danube River and three tributaries. It was observed a contamination of Danube River and its tributaries, higher in planting period than pre-or post- planting period, with the next compounds (detection frequency and the concentration range): thiamethoxam (68.7%, 0.9-3.8ng/L), clothianidin (64.6%, 0.84-9.6ng/L), nitenpyram (52.08%, 0.39-11.1ng/L), imidacloprid (31.2%, 0.5-8.2ng/L), acetamiprid (16.6%, 0.84-12.7ng/L). The four main neonicotinoids (clothianidin, thiamethoxam, imidacloprid, nitenpyram) follow the classic pattern in which concentrations and frequency increase during the planting period and that is correlated with seed crop treatment. Total neonicotinoid levels present in investigated Rivers, reaching up to 31.6 ng/L, may affect aquatic invertebrates that are most susceptible to these insecticides. For clothianidin and nitenpyram were obtained positive correlations between the percentage of the area planted with cereals and concentrations of this compound (r= 0.574, r =0.665) which indicate their use in agricultural area. For imidacloprid were obtained positive correlations between percent of permanent cultivated crop in urban land and concentrations of this compound (r =0.264, r =0.877).