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The development of a portable device created by 3D printing for colorimetric and fluorometric measurements is an efficient tool for analytical applications in situ or in the laboratory presenting a wide field of applications in the environmental and food field. This device uses a light-emitting diode (LED) as radiation source and a webcam as a detector. Digital images obtained by the interaction between the radiation source and the sample were analyzed using a programming language developed in Matlab (Mathworks Inc., Natick, MA, USA), which builds the calibration curves in real-time using the RGB colour model. In addition, the entire system is connected to a notebook which serves as an LED and detector power supply without the need for any additional power source. The proposed device was used for the determination in situ of norfloxacin, allura red, and quinine in water and beverages samples, respectively. For the validation of the developed system, the results obtained were compared with a conventional spectrophotometer and spectrofluorometer respectively with a t-test at a 95% confidence level, which provides satisfactory precision and accuracy values.

In general, it is accepted that water stagnation and lack or poor maintenance in buildings are risk factors for Legionella growth. Then, in theory, the prolonged hotel closures due to the COVID-19 pandemic may have increased the risk of Legionella infections. However, there are very few field studies comparing the level of Legionella colonization in buildings before the pandemic and the new situation created after the lockdown. The objective of this study was to analyze these differences in a group of hotels that experienced prolonged closures in 2020 due to the COVID-19 pandemic. We have studied the Legionella spp. results, analyzed by standard culture, from the domestic water distribution systems of 73 hotels that experienced closures (from 1 to >4 months) during 2020, immediately after the reopening. The results were compared with those obtained in similar samplings of 2019. For the comparative analysis, we divided the hotels in two groups: Group A that have suffered closures for ≤3 months and Group B that remained closed for more than 3 months, both in relation to the opening period of 2019. In the Group B (36 sites), the frequency of positive samples in the hot water system increased from 6.7% in 2019 to 14.0% in 2020 (p Legionella spp. concentrations and prevalence of Legionella pneumophila sg1 between the samplings of the two periods studied. The results suggest that hotels that suffered the longest prolonged closures (> 3 months) could have carried a higher risk of exposure to Legionella in the domestic hot water system. These findings highlight the importance of adequate preopening cleaning and disinfection procedures for hotel water systems, and the convenience of considering the most effective disinfection methods especially for hot water systems and after prolonged closure periods.

Long-chain fatty acids (LCFA) are commonly found in lipid-rich wastewaters and are a key factor to monitor the anaerobic digesters. A new simple, fast, precise, and suitable method for routine analysis of LCFA is proposed. The system involves in-syringe-magnetic stirring-assisted dispersive liquid-liquid microextraction (DLLME) prior to gas chromatography-mass spectrometry (GC-MS) without a derivatization process. Calibration curves were prepared in an ethanol solution (R2 ≥ 0.996), which was also useful as disperser solvent. Hexane was chosen as the extraction solvent. Several parameters (pH, ionic strength, extraction solvent volume, stirring time) were optimized in multivariate and univariate studies. Limits of detection (LODs) were found in the range 0.01–0.05 mg L−1 and good precision inter-day (RSDs≤7.9%) and intra-day (RSDs≤4.4%) were obtained. The method was applied to quantify LCFA in supernatants of anaerobic digesters and olive mill wastewaters (OMW). Palmitic, stearic, and oleic acids were the most abundant fatty acid in the analyzed samples and the relative recoveries for all of them were between 81 and 113%.

This work proposes an automated strategy for the inorganic selenium speciation in infusion tea samples, employing an MSFIA-CVG-AFS system and sodium tetrahydroborate for chemical vapor generation. The selenium total is determined after an online prereduction step of selenium (VI) to selenium (IV) in alkaline media, using a UV reactor with a 15 W Hg lamp. Selenium (IV) is quantified directly on the sample, and selenium (VI) is determined by the difference between the total selenium and selenium (IV) concentrations. The optimization of the chemical parameters: hydrochloric acid - hydrobromide acid solution concentration, potassium iodide concentration, sodium hydroxide concentration, and sodium tetrahydroborate concentration was performed using a (2

Soil properties' conservative behaviour is essential in sediment tracing research. To compare suspended sediment and soil samples, it is necessary that soil properties remain stable or vary in a predictable way during its transfer from sources to deposition areas. Conservative behaviour of soil properties has been largely focused on the differences in particle size and organic matter. However, in-channel biochemical alterations are also known to occur, but further research is needed considering the wide variety of fluvial regimes. Here is presented an experiment to investigate variations of in-channel soil properties' by using the most common soil properties used as tracers in sediment fingerprinting studies; i.e., colour, fallout radionuclides and geochemical elements. Twenty-eight soil samples collected from different land uses were introduced in an intermittent stream channel of a small Mediterranean catchment. Samples were extracted at different time intervals (i.e. 7, 30, 60, 90, 150, 210, 270 and 365 days) during one year. Results showed that changes on soil properties -average coefficient of variation 8.1 ± 8.8%- were generally lower than its spatial variability within the catchment (average coefficient of variation 16.3 ± 18.5%); being the colour properties the most stable tracers with an average coefficient of variation 2.6 ± 2.2%. The general low variability observed in the investigated soil properties and its strong correlations with specific surface area and carbon content seems to emphasize the role of particle size and organic matter in the conservative behaviour of soil properties. The exploration of in-channel soil properties variability can improve the selection of tracers in future suspended sediment fingerprinting studies in Mediterranean catchments.

In this work, a flow-based spectrofluorimetric method for iodine determination was developed. The system consisted of a miniaturized chip-based flow manifold for solutions handling and with integrated spectrofluorimetric detection. A multi-syringe module was used as a liquid driver. Iodide was quantified from its catalytic effect on the redox reaction between Ce(IV) and As(III), based on the Sandell–Kolthoff reaction. The method was applied for the determination of iodine in salt, pharmaceuticals, supplement pills, and seaweed samples without off-line pre-treatment. An in-line oxidation process, aided by UV radiation, was implemented to analyse some samples (supplement pills and seaweed samples) to eliminate interferences and release iodine from organo-iodine compounds. This feature, combined with the fluorometric reaction, makes this method simpler, faster, and more sensitive than the classic approach of the Sandell–Kolthoff reaction. The method allowed iodine to be determined within a range of 0.20–4.0 µmol L−1, with or without the in-line UV digestion, with a limit of detection of 0.028 µmol L−1 and 0.025 µmol L−1, respectively.

Different guidelines and regulations for the prevention of legionellosis in public facilities include the recommendation of a periodical thermal shock in the hot water system. The purpose of this study was to assess the efficacy of periodical thermal shocks along a 1-year period on the presence of

This work review shows a description of non-chromatographic and chromatographic procedures proposed for speciation analysis of antimony employing hydride generation (HG) coupled to atomic fluorescence spectrometry (AFS) in environmental matrices, including details of HG-AFS as the detection technique. Non-chromatographic procedures have been developed based on the determination of total antimony after a pre-reduction step. The main reductant agents used are discussed. Antimony(III) has been quantified in the presence of a masking agent. The most used are citrate and 8-hydroquinoline. Chromatographic procedures have been established utilizing High-Performance Liquid Chromatography (HPLC). Advantages and drawbacks of the main extracting agents and mobile phases employed in these procedures have been discussed. Also, alternatives to improve the method sensitivity during the determination of antimony(V) and its organic compounds by HPLC-HG-AFS are presented. Speciation procedures involving preconcentration steps have allowed methods with high sensitivity. Tables evidencing applications of non-chromatographic and chromatographic procedures in speciation studies of environmental samples are also shown. Advantages of automated and flow systems for antimony speciation studies are also highlighted.

A Multi-Syringe Flow Injection Analysis (MSFIA) fluorometric system based on a 3D printing device hosting a CCD detector has been designed for the determination of quinine in soft drinks. A LED controlled by an electronic circuit was used as a radiation source. The entire system is connected to two USB outputs of a computer. The AutoAnalysis program has been used for data acquisition and treatment. The results are more accurate and precise than those obtained with a manual method using a conventional spectrofluorometer. This developed system is a viable alternative to reduce the consumption of reagents, the impact on the environment and reduce measurement costs.

A very simple, fast and non-chromatographic methodology for inorganic antimony speciation based on Multisyringe Flow Injection Analysis (MSFIA) employing online hydride generation (HG) ICP-MS was developed. The fully automated analysis is performed in two steps: firstly, Sb(III) is quantified by ICP-MS after chemical vapor generation; then, total antimony is determined in the presence of potassium iodide as a pre-reducer of Sb(V) to Sb(III). The Sb(V) concentration is quantified by the difference between the total antimony and Sb(III) concentrations, reaching an analysis frequency of 30 h−1. The optimization was performed using a Box Behnken design. The MSFIA-HG-ICP-MS system allows the antimony speciation analysis with a detection limit of 0.016 µg L−1 for Sb(III), working in a linear range of 0.053 to 5.0 µg L−1. This method was applied for the determination of Sb(III) and Sb(V) in water samples from Maiorca Island, Spain, and the concentrations found varied from 0.10 to 0.14 µg L−1 for Sb(III) and from 0.12 to 0.28 µg L−1 for Sb(V). The results were validated by addition/recovery tests, obtaining recoveries between 90 and 111% in both cases. Furthermore, a good precision was achieved, 1.4% RSD, and sample and reagent consumption were reduced to a few mL, with the consequent decrease in waste generation. Thus, the proposed method is a good tool for the speciation of inorganic antimony at ultra-trace levels in waters, allowing its risk assessment.

A simple potentiometric chip-based multipumping flow system (MPFS) has been developed for the simultaneous determination of fluoride, chloride, pH, and redox potential in water samples. The proposed system was developed by using a poly(methyl methacrylate) chip microfluidic-conductor using the advantages of flow techniques with potentiometric detection. For this purpose, an automatic system has been designed and built by optimizing the variables involved in the process, such as: pH, ionic strength, stirring and sample volume. This system was applied successfully to water samples getting a versatile system with an analysis frequency of 12 samples per hour. Good correlation between chloride and fluoride concentration measured with ISE and ionic chromatography technique suggests satisfactory reliability of the system.

Different guidelines and regulations for the prevention of legionellosis in public facilities include the recommendation of a periodical thermal shock in the hot water system. The purpose of this study was to assess the efficacy of periodical thermal shocks along a 1-year period on the presence of Legionella spp. in the domestic hot water system of hotels. The Legionella testing results from the period January–December 2019 coming from a group of 77 hotel facilities in the Balearic Islands (Spain) conducting periodical thermal shocks were analyzed. A second group of 44 hotels operating without periodical thermal shocks was used for a comparative analysis. In the facilities where the periodical thermal shock was performed, 16.0% of the results (429 hot water samples collected) were positive for Legionella spp., compared to 21.1% (298 samples), where periodical thermal shock was not performed. Overall, in the thermal shock group, 32.5% of the sites presented at least 1 positive sample along the period of study versus 45.5% in the control group. None of these differences was statistically significant (p-value > 0.05). These findings suggest that the efficacy of regular thermal shock for long-term control of Legionella spp. in domestic hot water systems of hotels is low.

In this paper, a field-deployable method for the spectrophotometric determination of iron after a simple preconcentration procedure in column is proposed. A 3D-printed portable system, housing a small spectrophotometer with a CCD detector and a LED as homemade light source is used for spectrophotometric detection. The entire system is powered through two USB outputs of a notebook. The Fe (III) preconcentration is based on a solid phase extraction with a column packed of Chelex-100 chelating resin. The Fe (III) eluted in the cuvette was reduced to Fe (II) and the iron concentration was determined using the o-phenanthroline method. Preconcentration factors between 9.7 and 98 were obtained. Under optimized conditions, linear calibration curves without and with preconcentration were constructed (R2 > 0.9992). Low LD (5 µg L−1) and LQ (10 µg L−1) were achieved, and good values for intra-day and inter-day precision were obtained (RSD ≤ 2.9% and RSD ≤ 9.6%, respectively). Recoveries of spiked iron in local tap water, sea water, well water, leachate and supernatant of anaerobic digester were ranged from 93 to 106%. The validation of method was also carried out by successfully analyzing a river water reference material SLRS-4.

International audience; 15 The present paper reports the development and the application of a microplate assay for the fast 16 and individual determination of thiols and sulfides. The method is based on the reaction of ethyl 17 propiolate with thiols and sulfides, yielding thioacrylates absorbing in the UV range. 18 Thioacrylate generated by derivation of sulfide with EP presents a bathochromic shift of 19 maximal absorbance wavelength of 16 nm compared to thioacrylates formed with thiols. EP 20 concentration, reaction time and derivatization pH were carefully optimized in order to 21 separately quantify thiols and sulfides using a spectral deconvolution procedure in 15 minutes. 22 The detection limits were 0.6 and 2.8 µM (63.7 and 92.4 µg.L-1) for mercaptopropionic acid 23 (used as reference thiol compound for calibration) and dissolved hydrogen sulfide respectively. 24 Non-thiol sulfur compounds (methionine, sulfates and sulfites) or other nucleophile compound 25 did not display any interference in the determination of MPA or sulfides. Interference from 26 metals was suppressed with application of a reduction step with TCEP and DTPA. Finally, the 27 method has been successfully applied to the analysis of raw and treated wastewater. 28 29

Dietary supplements may contain heavy metals with the property of bioaccumulation in humans. The aim of this research was to validate and apply two analytical methods to determine Pb, As, Cr, and Hg in dietary supplements by Total Reflection X-ray Fluorescence Spectroscopy (TXRF). Methods validation was conducted through a multivariate analysis using a central composite design (CCD) and a desirability function. Critical values for each study variable were established. The TXRF_DS_1 method was proposed for Pb, As, and Cr determinations, while the TXRF_DS_2 was established for Hg analysis. The digestion method with an acid mixture (HNO3 + HCl + H2O2) was used to break down the organic material of dietary supplements. A solution of 10 μg L−1 Ga was used as an internal standard. Excellent analytical performance was obtained as LODs of 0.59, 0.41, 0.57, and 0.75 μg L−1 and LOQs of 1.95, 1.35, 1.90, and 2.50 μgL −1 for Pb, As, Cr, and Hg, respectively. Calibration curves showed a good linearity for all elements (R2>0.999). Excellent accuracy and precision in measurements (% RSD) was achieved. The real and spiked samples analysis demonstrated the applicability of the TXRF technique (percentage recovery 91–108%). Besides, two samples were analyzed in a comparison study between the TXRF_DS_1 method and the ICP-OES method. The results obtained showed good agreement between both techniques. The TXRF technique allows the analysis of toxic heavy metals in dietary supplements, which are marketed in a wide variety of presentations.

Volatile fatty acids (VFAs) are key parameters to monitor anaerobic digestion processes. Thus, a fast, simple and precise determination of these analytes is necessary for a timely characterization of the biological processes present in municipal solid waste and wastewater treatment plants. In this work, an automated method for the extraction and preconcentration of VFAs, based on dispersive liquid-liquid microextraction with magnetic stirring in syringe, and gas chromatography with flame ionization detector for the separation and detection, is described. The effect of parameters such as the type and volume of extraction solvent, pH, salting out effect and stirring time, was studied using a multivariate and univariate experimental design. Extraction and preconcentration were performed simultaneously using tert-butyl methyl ether (TBME) as the extraction solvent, after stirring 100 s at a constant rate. The detection limits were in the range of 0.1 - 1.3 mg L-1 and a good linearity was observed up to 1000 mg L-1 of the studied VFAs, with a range of R2 between 0.9997 and 0.9999. The intra and interday precision expressed as relative standard deviation (n= 5) varied between 0.7 and 2.4% and between 1.7 and 7.0%, respectively. Subsequently, the developed method was successfully applied to evaluate the presence of VFAs in wastewater samples from anaerobic treatments and an average relative recovery of 102% was obtained.

Corn is one of the most consumed cereals in world and the second most cultivated in Brazil. Cereal flour has a flavor well accepted by the Brazilian population. This work describes the preparation and characterization of a new corn flour reference material which can be used as a quality assurance tool to demonstrate the reliability of the analytical results obtained from inorganic analysis of cereals and their derivatives. The studied elements were Ca, K, Mg, P, Cu, Fe, Mn and Zn. Homogeneity and stability tests, material characterization and attribution of uncertainty value were performed in this work by following recommendations of ISO Guides 30–35. The material was shown to be homogeneous and stable for 15 months at temperatures of −10 °C, +25 °C and +45 °C, with small uncertainty. Alternatively, the data were analyzed by hierarchical clustering technique and the stability was confirmed. The confidence ellipse technique enabled a simple and fast evaluation of data supplied by collaborating laboratories allowing the exclusion of outlying values and indicating possible causes of the deviations.

The spectrophotometric determination of uranium (VI) has been developed using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP). This reaction has been adapted to apply a multisyringe flow injection analysis (MSFIA) system with spectrophotometric detection. The ternary complex of uranium (VI)-(Br-PADAP)-F has been measured at 578 nm. The procedure was optimized using univariate method and two-level full factorial. Four variables (concentrations of Br-PADAP, CyDTA, NaF and sample volume) were regarded as factors in the extraction optimization. Results of the two-level full factorial design, showed that only two factors (concentration of Br-PADAP and CyDTA) are statistically significant. The calibration curve is linear over the range 0.3–5 mg L−1 uranium (VI) with a relative standard deviation of 4.0% (1 mg L−1 uranium (VI), n = 10). The recoveries of uranium in water samples were between 80 and 102%.

In this work, the automation of a catalytic spectrophotometric method for the determination of molybdenum is presented. For this purpose, a multisyringe flow injection system was coupled to an integrated microconduit that we have called “chip”. Reagents and sample were simultaneously dispensed to the chip where complete mixing, heating, and measurement were carried out. The spectrophotometric method is based on the oxidation of 4-amino-3-hydroxy-naphthalenesulphonic acid (AHNA) by hydrogen peroxide catalyzed by Mo (VI). Absorbance of the reaction product was measured at 465 nm. Two optical fibers were used to conduct the light, one from the source to the chip, and the other from the output of the cell to the spectrophotometer. The detection cell was incorporated in the thermostated zone of the chip. The initial rate method, at controlled temperature, was employed to determine the Mo (VI) concentration. The estimated precision was 3.7%, with the working range of 4.0–40 µg L−1 of Mo (VI), and the limit of detection of 1.2 µg L−1 of Mo (VI). The system was successfully applied to water samples and pharmaceutical products with a sampling throughput of 20 injections h−1.

In this work, we present an automated catalytic spectrophotometric method for determination of Mn(II) by using a multisyringe burette coupled to a chip microfluidic-conductor (Chip-MSFIA). The reaction is based on the catalytic effect of Mn(II) on the auto-oxidation reaction of succinimidedioxime (SIDO). Reagents and the sample were simultaneously dispensed to the chip for their complete mixing, heating, and measurement. The absorbance of the reaction product was measured at 700 nm. The product concentration could be determined by the fixed-time and the initial rate method under optimum conditions (temperature 35 °C, 4.70 mmol L−1 SIDO, and 0.60 mol L−1 NaOH). Both fixed-time and initial rate methods have been developed, with the fixed-time method giving higher reproducibility and a wider working range. Therefore it was selected for Mn(II) samples in the working range of 1–20 μg L−1 of Mn(II). The estimated precision was 0.67% (5 μg L−1, n = 15) and the limit of detection of Mn(II) was 0.33 μg L−1. The proposed method is highly sensitive, selective, and simple for trace Mn(II) determination without extraction and separation steps. The system was successfully applied to water samples with an injection throughput of 22 injections h−1.

The present paper proposes the use of a multi-syringe flow injection analysis (MSFIA) system for the determination of Cd in natural water by cold vapour atomic absorption spectrometry (CV-AAS). The chemical and physical conditions for vapour generation were investigated and optimized using multivariate optimization methodology. Some complexing reagents were tested as additives to increase the analytical signal. Thiourea showed a positive effect, whereas L-cysteine reduced the signal of Cd. The method allows the direct determination of Cd, i.e. without sample pre-concentration, with limits of detection and quantification of 5.8 and 19.3 ng L−1, respectively, and employing external calibration technique. The precision expressed as a relative standard deviation varied between 1.4% and 2.9% for two levels of cadmium (0.25 and 2.5 μg L−1). Using 2 mL of sample volume, an injection throughput of 87 h−1 was achieved. The accuracy was confirmed by the analysis of a certified reference sample of seawater (CASS-4) furnished by National Research Council of Canada and addition/recovery tests, obtaining recoveries between 94% and 101%. The method was satisfactorily applied for the determination of Cd in seawater and ground water samples from Mallorca, Spain.

An automatic integrated system implementing a catalytic spectrophotometric method for vanadium determination is presented. Thus, a multisyringe flow injection system (MSFIA) was coupled to a monolithic flow microconduit, called chip (CHIP-MSFIA). All reagents and samples were simultaneously propelled into the chip to achieve complete mixing, heating, and measurement inside it. This catalytic spectrophotometric method is based on the oxidation of gallic acid with bromate catalyzed by V(V). The reaction was followed by measuring the absorbance change at 384 nm. The incorporation of the detection cell inside the thermostatic zone of the chip allows two kinetic–catalytic determination methods: initial rate and fixed time methods. A critical comparison between these two methods at a controlled temperature is presented. Under optimized conditions, the determination of V(V) was performed in the range 0.24–75 μg L−1 achieving limits of detection of 0.33 and 0.24 μg L−1 for fixed-time and initial rate methods, respectively. Relative standard deviations were between 1% and 4%. Finally, the initial rate method was successfully applied to determine the V(V) concentration in natural and waste water samples. Good recoveries were obtained varying from 94% to 102%. Results were compared with those obtained by the reference method (ICP-AES), in order to confirm the accuracy of the CHIP-MSFIA method. Additionally, a certified reference material was satisfactorily analyzed.

In this work a fully automated catalytic–spectrophotometric method for determination of copper at trace levels using a multisyringe flow injection system (MSFIA) and a multipumping flow system (MPFS) coupled to a micro-chip (Chip–MSFIA–MPFS) is presented. The reaction is based on the catalytic effect of Cu(II) on the oxidation of the in situ reduced form of 2,6-dichlorophenolindophenol (DCPI)r, by hydrogen peroxide. Due to the importance of the mixing order of the reagents, a new design of the chip is proposed. DCPI, ascorbic acid and buffer are first propelled to mix in the front section of the chip using MPFS. Then this reagent mixture, together with hydrogen peroxide and the sample, is simultaneously dispensed to the rear section of the chip by using a multisyringe for mixing, heating and absorbance measurement of the product at 600 nm. The optimum conditions are 0.9 mmol L−1 DCPI, 3.6 mmol L−1 ascorbic acid, 0.8 mol L−1 ammonium chloride buffer, pH 10.5, and 0.3 mol L−1 H2O2. The proposed system is simple, rapid, selective and sensitive. We can determine trace levels of Cu(II) at room temperature (25 °C). The main analytical characteristics of the proposed method are a detection limit of 0.12 μg L−1 of Cu(II), a working range of 0.4–35.0 μg L−1 of Cu(II), and a relative standard deviation of 0.79% (10 μg L−1 Cu(II), n = 15). The system was successfully applied to water samples, certified reference materials (CRMs) of river and waste water, acid digested multivitamins and animal tissues with a sample throughput of 31 injections h−1.

In this paper, an on-line spectrofluorimetric system is proposed for a simple, rapid and accurate measurement of volatile fatty acids (VFA) in anaerobic treatment processes. The determination method is based on the derivatization of VFA with N-(1-naphthyl)ethylenediamine (EDAN) followed by a spectrofluorimetric detection of the corresponding amide. The analytical procedure is automated with a flow analysis technique, coupling multisyringe (MSFIA) and multi-pumping (MPFS) methods. Operative conditions have been investigated with a special attention paid to the activation and amidation steps and to the liquid-liquid extraction of the derivatized final product. Fluorescence intensities (lambda(em)=335 nm, lambda(ex)=395 nm) were found to be proportional to the concentration of VFA, expressed as acetic equivalent, in the range 19-1000 mg L(-1), with a detection limit (3sigma) of 5.1 mg L(-1). Our results showed a good selectivity for VFA as compared to other organic and inorganic compounds usually found in sewage sludges. Validation of the on-line system developed has been assessed by application of the procedure to aqueous samples originating from sewage sludge treatment plants. The results were in good agreement with ion chromatography measurements.

International audience; This paper presents a simple, accurate and multi-sample method for the determination of volatile fatty acids (VFAs) thanks to a 96-well microplate technique. A procedure using an activating reagent of the carboxylic function (water-soluble carbodiimide EDC) and a fluorescent amino labeling reagent (N-(1-naphthyl)ethylenediamine, EDAN) allows the formation of an isoindole derivative that needs to be separated from initial fluorescent amine for efficient VFAs determination. Isolation of these fluorescent VFA-derivatives was carried out by use of the fluorescent quenching of EDAN with o-phthaldialdehyde (OPA). Quenching was most efficient at pH around 7 and by heating at 40 degrees C within the microplate reader. This optimized procedure has been applied to various carboxylic acids and other organic compounds, demonstrating that VFA exhibit the highest fluorescence responses with homogeneous results for the main ones (acetic, propionic and butyric acid, all mass concentration expressed as acetic acid equivalents). This protocol was calibrated against acetic acid and determination of VFA was thus possible in the range 3.9-2000 mg L-1 (acetic acid equivalents). Subsequent application to real samples (sewage sludges or anaerobically digested samples) and comparison to gas chromatography analyses gave accurate results, proving the great potential of our high-throughput microplate-based technique for the analysis of VFA. (C) 2011 Elsevier B.V. All rights reserved.

Correspondance auteur: Boudenne J.L. E-mail: jean-luc.boudenne@univ-provence.fr; International audience; This paper presents a simple, rapid, and accurate method suitable for on-site measurement of short-chain volatile fatty acids (SCFA) in various environmental samples. This fluorimetric method involves a derivatization step of SCFA with N-(1-naphthyl)ethylenediamine (EDAN) and allows determination of acetic, butyric, propionic, valeric, lactic, succinic, and p-hydroxybenzoic acids in approximatively 10 min. To evaluate specificity and accuracy of the method, both laboratory-made waters and real samples ranging from wastewater plant and river to soils and composts have been tested. Good accuracy and correlation (r(2) = 0.9887) with HPIC determination have been obtained. The potential interference effect has been taken into account with compounds like humic substances, alcohols, amines, aldehydes, and metallic ions. Ibis method seems thus well designed for the determination of total SCFA in waters, in the range 0.84-500 mg/L. Because this method seems well suited for following of anaerobic treatment, it has been calibrated versus acetic acid-equivalent