Search

[EN] A comprehensive study on the chiral separation of bupivacaine, mepivacaine, prilocaine and propanocaine with eight commercial polysaccharide-based chiral stationary phases (CSPs) in reversed phase conditions compatible with MS detection is performed. Methanol and acetonitrile are used as organic modifiers. Retention and resolution values obtained for each compound in the different CSPs and mobile phases are compared. The polysaccharide-based CSPs tested present different enantioselectivity towards the analytes. From the results, the experimental conditions for determining the enantiomers of bupivacaine, mepivacaine, prilocaine and propanocaine in saline aqueous samples using MS detection are used, for the first time, to perform an enantioselective biodegradability study. (C) 2020 Elsevier B.V. All rights reserved.

[EN] Polysaccharide-based chiral stationary phases (CSPs) are the most used chiral selectors in HPLC. These CSPs can be used in normal, polar organic and aqueous-organic mobile phases. However, normal and polar organic mobile phases are not adequate for chiral separation of polar compounds, for the analysis of aqueous samples and for MS detection. In these situations, reversed phase conditions, without the usual non-volatile additives incompatible with MS detection, are preferable. Moreover, in most of the reported chiral chromatographic methods, retention is too large for routine work. In this paper, the chiral separation of 53 structurally unrelated compounds is studied using three commercial amylose-based CSPs -coated amylose tris(3,5-dimethylphenylcarbamate) (Am1), coated amylose tris(5-chloro-2-methylphenylcarbamate) (Am2), and immobilised amylose tris(3-chloro-5-methylphenylcarbamate) (Am3)-. Chiral separations are carried out using acetonitrile/ammonium bicarbonate (pH = 8.0) mixtures, reversed mobile phases compatible with MS detection. To provide realistic conditions for routine analysis, maximum retention factors are set to 15. Retention and enantioresolution behaviour of compounds in those CSPs are compared. On the other hand, to compare and describe the resolution ability of these CSPs, 58 structural variables of the compounds are tested to model for the first time a categorical enantioresolution (CRs) for Am1 and Am3 CSPs. Discriminant partial least squares, for one response categorical variable (DPLS1) is used for feature selection, modelling. The final DPLS1 models showed good descriptive ability.

[EN] Accurate and reliable estimation of kinetic parameters of pollutant biodegradation processes is essential for environmental and health risk assessment. Common biodegradation models proposed in the literature, such as the nonlinear Monod equation and its simplified versions (e.g. Michaelis-Menten-like and first-order equations), are problematic in terms of accuracy of kinetic parameters due to the parameter correlation. However, a comparison between these models in terms of accuracy and reliability, related to data imprecision, has not been performed in the literature. This task is necessary, mainly because the model selection cannot be straightforward, as shown in this work. To facilitate the comparison, novel statistics summarising the accuracy and reliability of estimations are introduced. The main objective is to establish relationships between these statistics (trough new diagnostic indicators) to limit the probability of pitfalls or to avoid the negative impact of an improper model selection. Such anticipation is an imperative need in the biodegradation modelling framework and, to the best of our knowledge, it has never been performed. In order to account for accuracy, simulated data in realistic conditions are used to highlight the magnitude of pitfalls related to the model selection for estimation of the main kinetic parameters (K-s, mu(m) and/or V-m). Four scenarios related to model selection are compared for the first time and, diagnostic indicators able to anticipate relevant aspects related to accuracy and reliability are introduced. Moreover, first evidences of the impact of measurement errors in other intrinsic Monod parameters (the initial biomass concentration and the microbial yield coefficient, Y), as well as the impact of the simultaneous mu(m), K-s and Y estimation, on the accuracy and reliability of the estimations are reported. Despite the pitfalls shown, specific applicability of even unreliable models is highlighted, and suggestions for e

[EN] A great number of available pharmaceuticals are chiral compounds. Although they are usually manufactured as racemic mixtures, they can be enantioselectively biodegraded as a result of microbial processes. In this paper, a biodegradability assay in similar conditions to those recommended in OECD tests of enantiomers of trimeprazine (a phenothiazine employed as a racemate) is carried out. Experiments were performed in batch mode using a minimal salts medium inoculated with an activated sludge (collected from a Valencian Waste Water Treatment Plant, WWTP) and supplemented with the racemate. The concentration of the enantiomers of trimeprazine were monitored by means of a chiral HPLC method using a cellulose-based chiral stationary phase and 0.5 M NaClO4/acetonitrile (60:40, v/v) mobile phases. Experiments were performed at three concentration levels of the racemate. In parallel, the optical density at 600 nm (OD600) was measured to control the biomass growth and to connect it with enantioselectivity. The calculated enantiomeric fractions (EF) offer the first evidence of enantioselective biodegradation of trimeprazine. A simplified Monod equation was used as a curve fitting approach for concentration (S), biodegradation (BD), and for the first time, EF experimental data in order to expand the usefulness of the results. Precision studies on S (repeatability conditions) and, for the first time, EF (intermediate precision conditions) were also performed.

[EN] The quantification of the enantiomeric fraction (EF) during the biodegradation process is essential for environmental risk assessment. In this paper the enantioselective biodegradation of ibuprofen, IBU, and ketoprofen, KET, two of the drugs most consumed, was evaluated. Biodegradation experiments were performed in batch mode using a minimal salts medium inoculated with an activated sludge (collected from a Valencian Waste Water Treatment Plant) and supplemented with the racemate of each compound. The inoculum activity was verified using fluoxetine as reference compound. The experimental conditions used (analyte concentration and volume of inoculum) were chosen according to OECD guidelines. In parallel, the optical density at 600 nm was measured to control the biomass growth and to connect it with enantioselectivity. Two RPLC methods for chiral separations of IBU and KET using polysaccharides-based stationary phases were developed. Novel calculations and adapted models, using directly the chromatographic peak areas as dependent variable, were proposed to estimate significant parameters related to the biodegradation process: biodegradation (BD) and EF values at given time, half-life times of (R)- and (S)-enantiomers, number of days to reach a complete BD and the minimum EF expected. The modelled BD and EF curves fitted adequately the data (R-2 > 0.94). The use of these new equations provided similar results to those obtained using concentration data. However, the use of chromatographic peak areas data, eliminates the uncertainty associated to the use of the calibration curves. The results obtained in this paper indicate that an enantiorecognition towards 1BU enantiomers by the microorganisms present in the activated sludge used in this study occurred, being the biodegradation of (R)-IBU higher than that of (S)-IBU. For KET, non-enantioselective biodegradation was observed.

[EN] To the best of our knowledge, the prediction of the enantioresolution ability of polysaccharides-based stationary phases in liquid chromatography for structurally unrelated compounds has not been previously reported. In this study, structural information of neutral and basic compounds is used to model their enantioresolution levels obtained from an immobilised cellulose tris(3,5-dichlorophenylcarbamate) stationary phase in reversed phase conditions. Thirty-four structurally unrelated chiral drugs and pesticides, from seven families, are studied. Categorical enantioresolution levels (RsC, 0 = no baseline enantioresolution and 1 = baseline enantioresolution) are established from the experimental enantioresolution values obtained at a fixed experimental conditions. From 58 initial structural variables, three topological parameters (two of them connected to the chiral carbon), and six molecular descriptors (one of them also related with the chiral carbon), are selected after a discriminant partial least squares refinement process. The molar total charge of the molecule at the working pH is the most important variable. The relationships between RsC and the most important structural variables and the drug/pesticide family are evaluated. An explicit model is proposed to anticipate the RsC levels, which provides 100% of correct anticipations. A criterion is introduced to alert about the compounds that should not be anticipated.

[EN] Background: There is a growing concern for the problem of food authenticity assessment (and hence the detection of food adulteration), since it cheats the consumer and can pose serious risk to health in some instances. Unfortunately, food safety/integrity incidents occur with worrying regularity, and therefore there is clearly a need for the development of new analytical techniques. Scope and approach: In this review, after briefly commenting the principles behind the design of electronic noses and electronic tongues, the most relevant contributions of these sensor systems in food adulteration control and authenticity assessment over the past ten years are discussed. It is also remarked that future developments in the utilization of advanced sensors arrays will lead to superior electronic senses with more capabilities, thus making the authenticity and falsification assessment of food products a faster and more reliable process. Key findings and conclusions: The use of both types of e-devices in this field has been steadily increasing along the present century, mainly due to the fact that their efficiency has been significantly improved as important developments are taking place in the area of data handling and multivariate data analysis methods. (C) 2016 Elsevier Ltd. All rights reserved.

Fermentation processes are often sensitive to even slight changes of conditions that may result in unacceptable end-product quality. Thus, close follow-up of this type of processes is critical for detecting unfavorable deviations as early as possible in order to save downtime, materials and resources. Nevertheless the use of traditional analytical techniques is often hindered by the need for expensive instrumentation and experienced operators and complex sample preparation. In this sense, one of the most promising ways of developing rapid and relatively inexpensive methods for quality control in fermentation processes is the use of chemical multisensor systems. In this work we present an overview of the most important contributions dealing with the monitoring of fermentation processes using electronic noses and electronic tongues. After a brief description of the fundamentals of both types of devices, the different approaches are critically commented, their strengths and weaknesses being highlighted. Finally, future trends in this field are also mentioned in the last section of the article. (C) 2013 Elsevier B.V. All rights reserved.