Successful matchmaking: The combination of a chiral nitrene precursor with a chiral rhodium(II) catalyst is the key factor that allows efficient intermolecular regioselective CH amination. ...Good‐to‐excellent yields and excellent diastereoselectivities can be obtained with a stoichiometric amount of the CH bond containing substrate. nttl=N‐1,8‐naphthoyl‐tert‐leucine.
Reaction between a sulfur(VI) compound and an iodine(III) oxidant in the presence of a catalytic quantity (≤3 mol %) of a rhodium(II) catalyst leads to the formation of a chiral metallanitrene of ...unprecedented reactivity. The latter allows intermolecular C−H amination to proceed in very high yields up to 92% and excellent diastereoselectivities up to 99% with C−H bond containing starting materials as the limiting component. The scope of this C−H functionalization includes benzylic and allylic substrates as well as alkanes. Secondary positions react preferentially, but insertion into activated primary C−H bonds or sterically accessible tertiary sites is also possible. Cooperative effects between the nitrene precursor and the chiral catalyst at the origin of these good results have also been applied to kinetic resolution of racemic sulfonimidamide. This methodology paves the way to the use of Csp3−H bonds as synthetic precursors for the introduction of a nitrogen functionality into selected positions.
The development of 3D printing in recent years opens up a vast array of possibilities in the field of flow analysis. In the present study, a new 3D-printed flow system has been developed for the ...selective spectrophotometric determination of lead in natural waters. This system was composed of three 3D-printed units (sample treatment, mixing coil and detection) that might have been assembled without any tubing to form a complete flow system. Lead was determined in a two-step procedure. A preconcentration of lead was first carried out on TrisKem Pb Resin located in a 3D-printed column reservoir closed by a tapped screw. This resin showed a high extraction selectivity for lead over many tested potential interfering metals. In a second step, lead was eluted by ammonium oxalate in presence of 4-(2-pyridylazo)-resorcinol (PAR), and spectrophotometrically detected at 520nm. The optimized flow system has exhibited a linear response from 3 to 120µgL−1. Detection limit, coefficient of variation and sampling rate were evaluated at 2.7µgL−1, 5.4% (n=6) and 4 sampleh−1, respectively. This flow system stands out by its fully 3D design, portability and simplicity for low cost analysis of lead in natural waters.
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•A 3D-printed Multi Pumping Flow System is presented.•Selective extraction of lead using Triskem Pb resin enables elimination of interferences.•Pb2+ can be quantified between 3 and 120µgL−1 with a LOD of 2.7µgL−1.•This flow system is a low cost and portable system allowing in-situ measurement.
This paper presents the development and the application of a multisyringe flow injection analysis system for the fluorimetric determination of the major heat-stable known allergen in shrimp, rPen a 1 ...(tropomyosin). This muscle protein, made up of 284 amino acids, is the main allergen in crustaceans and can be hydrolyzed by microwave in hydrochloric acid medium to produce glutamic acid, the major amino acid in the protein. Glutamic acid can then be quantified specifically by thermal conversion into pyroglutamic acid followed by chemical derivatization of the pyroglutamic acid formed by an analytical protocol based on an OPA-NAC reagent. Pyroglutamic acid can thus be quantified between 1 and 100 µM in less than 15 min with a detection limit of 1.3 µM. The method has been validated by measurements on real samples demonstrating that the response increases with the increase in the tropomyosin content or with the increase in the mass of the shrimp sample.
The present paper reports the development and the application of a microplate assay for the fast and individual determination of thiols and sulfides. The method is based on the reaction of ethyl ...propiolate with thiols and sulfides, yielding thioacrylates absorbing in the UV range. Thioacrylate generated by derivation of sulfide with EP presents a bathochromic shift of maximal absorbance wavelength of 16nm compared to thioacrylates formed with thiols. EP concentration, reaction time and derivatization pH were carefully optimized in order to separately quantify thiols and sulfides using a spectral deconvolution procedure in 15min. The detection limits were 0.6 and 2.8μM (63.7 and 92.4μg·L−1) for mercaptopropionic acid (used as reference thiol compound for calibration) and dissolved hydrogen sulfide respectively. Non-thiol sulfur compounds (methionine, sulfates and sulfites) or other nucleophile compound did not display any interference in the determination of MPA or sulfides. Interference from metals was suppressed with application of a reduction step with TCEP and DTPA. Finally, the method has been successfully applied to the analysis of raw and treated wastewater.
•A simple microplate assay based on EP derivatization procedure was developed for the simultaneous determination of thiols and sulfides in wastewater.•The thioacrylate formed with HS− presents a bathochromic shift of 16nm compared to thioacrylate formed with MPA.•Under optimized derivatization conditions, the method has a low LOD with a 2min reaction time.•The method was successfully applied to real wastewater samples.
In this paper, a new spectrofluorimetric method is proposed for the fast, simple, and accurate determination of trace resorcinol in the microplate format (high-throughput screening). The analytical ...method is based on the formation of a coumarin derivative with methyl acetoacetate via a Pechmann condensation reaction. Experimental conditions have been optimized, and excellent analytical performances have been achieved with a limit of detection of 0.46μgL−1, a wide linear range between 1.5 and 1000μgL−1 and a relative standard deviation of 2.01% (n=10).
This method is remarkably specific for resorcinol compared to other phenols and hydroxyphenols and suffers from low interferences from other potential matrix components. The proposed protocol was finally applied and validated on real samples such as wastewater or pharmaceutical/cosmetic samples.
•A new spectrofluorimetric method for the determination of resorcinol is presented.•The method uses coumarin formation with methylacetoacetate.•It is highly selective and specific for resorcinol.•The method was validated on real samples (wastewater, cosmetics)
The detection of explosives is of paramount importance in the areas of internal security and military activities. Tracking down clandestine laboratories manufacturing homemade explosives, and in ...particular those made from organic peroxides (triacetone triperoxide TATP, methyl ethyl ketone peroxide MEKP, hexamethylene triperoxide diamine HMTD), is a major issue in the fight against terrorism worldwide. During the synthesis of these peroxide-based explosives, significant quantities of precursors or residues of explosives may be discharged into wastewater and then in environmental waters. Some of these precursors (e.g. acetone or hydrogen peroxide) are used for other applications (e.g. solvents, bleaching agents, medical and industrial products) and are therefore not specific of the manufacture of explosives. However, they can provide a first indication of the location of the production site through on-line monitoring of wastewater. Many analytical techniques exist for the trace analysis of explosives on post blast surfaces or for the quantification of traces of hydrogen peroxide in biological systems (topics already reviewed elsewhere). However, the application of these techniques to water and wastewater monitoring remains challenging. In this review, water sample preparation and instrumental methods applied (or at least adaptable) to water analysis for the quantification of peroxide-based explosives (PBEs) and of their major precursors are reviewed and discussed. Sample preparation by solid-phase extraction (SPE) is thoroughly investigated for organic peroxides and some precursors. Analytical methods such as electrochemistry, spectroscopy, chromatography coupled to mass spectrometry or flow injection techniques are presented for their application to PBEs. The advantages and disadvantages of the different analytical techniques show that some of these techniques could be combined to develop low-cost, easily transportable, and miniaturized methods for automated in-situ analyses of explosives and their major precursors.
•Homemade explosives present key challenges for in-situ detection in wastewaters.•SPE combined with LC-MS/MS most suitable for sensitive and specific analysis of PBEs.•Flow-based methods seem to be appropriate for continuous monitoring of PBEs in wastewater and need to be further developed.•Most of homemade explosives analytical methods are based on the detection of H2O2.
Inorganic chloramines are disinfection by-products resulting from the unwanted reaction between chlorine used as disinfectant in swimming pools and nitrogenous compounds brought by bathers. This ...parameter (total chloramines or combined chlorine) is currently measured on site by a colorimetric method that does not allow to measure only inorganic chloramines. In this paper, a multi-syringe chromatography system combined with a post column derivatization is applied for the first time for the specific detection of the three individual inorganic chloramines (monochloramine, dichloramine and trichloramine). These latter ones are separated using a low-pressure monolithic C18 column, and separately detected after a post-column reaction with the chromogenic reagent ABTS (2,2′-azino-bis-(3-ethyl-benzothiazoline)-6-sulfonic acid-diammonium salt). Development of two ABTS reagents provides discrimination of chlorine and monochloramine that are not separated on the column. Optimization of the experimental conditions enables determination of inorganic chloramines with very good detection limits (around 10 μg eq.Cl2 L−1) without interferences from other chlorinated compounds such as organic chloramines or free available chlorine. The validation of the whole procedure has been successfully applied to real swimming pools samples.
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•New automated system for the analysis of inorganic chloramines in swimming pools.•Post-column reaction with ABTS provides detection limits around 10 μg eq.Cl2.L−1.•No interferences from organic chloramines or other disinfection by-products.•DPD reference methods overestimates dichloramine in real swimming pool samples.
A new procedure is described for the determination of Hg2+ ions in water samples. A Rhodamine based fluorescent sensor was synthesized and the experimental conditions were specifically optimized for ...application to environmental samples, which requires low detection limits and high selectivity in competitive experiments with realistic concentrations of other metal ions. Incorporation of a Rhodamine-6G fluorophore to a previously described sensor and optimization of the buffer system (detection with acetic acid at pH 5.25) enabled significant enhancement of the sensitivity (detection limit = 0.27 μg L−1) and selectivity. The optimized procedure using high-throughput microplates has been applied to tap and river waters with good results.
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•Optimized rhodamine sensor and experimental conditions for Hg2+ detection.•Acetic acid buffer enables detection limit at nM level.•Selectivity over other metal ions has been proven with environmental concentrations.•Procedure applied and validated on real water samples (tap water and river samples).
This work presents a multisyringe flow injection analysis (MSFIA) system for the automatic extraction and determination of tetracyclines in wastewater samples. The sample was adjusted with Na
EDTA ...buffer before solid-phase extraction with an Oasis HLB column used for the analyte preconcentration. The europium (Eu
)-based and citrate-mediated method (using Tris-HCl buffer) was selected for the fluorimetric analysis (λ
= 400/612 nm). For fluorescence detection, a low-cost system consisting of an USB 2000 CCD detector and a 3D-printed support that holds a LED light source was used. Under optimized conditions, the proposed method provided low limits of detection (9.4 μg L
) and quantification (31 μg L
), and good values for intra-day (<4 %) and inter-day precisions (<6 %). Recoveries of spiked TCs in wastewater samples ranged from 87 to 106 %. The results of this work were in good agreement with the measurements obtained by liquid chromatography coupled to a fluorescence detector.
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