Lesliebrantley7098

Thiol compounds (R-SH) have many important biological functions and are principal controls of the speciation of several toxic metals in the environment. However, determining the concentration of thiols associated with environmental matrices is challenging due to the compounds' low abundance and interferences from non-thiol compounds for many available methods. Here a novel method has been developed and validated to quantify the total concentration of thiol functional groups in aqueous samples using derivatization with monobromo(trimethylammonio)bimane (qBBr) and quantification with tandem mass spectrometry. The thiol concentration was determined by titration of the sample with qBBr, which reacts selectively with thiols, and quantification of the residual qBBr. We systematically evaluated potential interferences from various organic compounds, inorganic ions (including sea water matrices), sulfide and mercury (Hg) species, and demonstrate that the method is highly sensitive, selective and robust. The limit of detection (LOD) for total thiols is in the nanomolar concentration range (~6 nM). The method performance was also demonstrated by determination of the total thiol concentration in different natural samples including boreal stream water (1.16 μM), wetland porewater (0.96 μM) and the Suwanee River natural organic matter (NOM) reference material SR101 N (7.9 μmol g-1). The developed method represents a combination of low LOD and high selectivity and robustness that is unsurpassed for total thiol concentration measurements.This work presents a new optical microfluidic paper biosensor for the detection of organophosphate pesticides and carbamate pesticides. The assay strip is composed of a paper support (1 × 17.6 mm) onto which acetylcholine esterase (AChE) and acetylcholine chloride (AChCl) are deposited, in such a way that there is a small hole between them that ensures that they only come into contact in the reaction zone when they are carried by a solution of the sample by lateral flow to the reaction zone containing bromocresol purple (BCP) as the pH indicator, immobilized by sol-gel. The sensor operates at room temperature and the rate of the inhibited reaction serves as an analytical signal, which is measured using a camera by quantifying the appropriate colour coordinate. Calibration curves were obtained for chlorpyrifos and carbaryl, with a useful concentration range from 0.24 to 20 μg L-1 for carbaryl and from 2.00 to 45 μg L-1 for chlorpyrifos. The detection limits were 0.24 and 2.00 μg L-1, respectively, and with reproducibility around 4.2-5.5%. The method was applied to the determination of pesticides in different water samples, with no sample preparation.A novel ultra high pressure liquid chromatography combined with high resolution mass spectrometry (UHPLC-HRMS) method was developed to study glutathionyl and cysteinyl polysulfides in wine. Different HPLC columns were investigated in order to optimise the chromatographic resolution of the polysulfide standard mixtures synthesised in-house. The optimisation of the chromatographic conditions when trying to separate glutathionylated and cysteinylated species containing from 3 to 5 sulfur atoms proved particularly challenging, with the cationic exchange column IonPac CS12A-MS resulting to be the best column for this task.The synergistic application of the newly developed methods together with the synthesised reference standard mixtures allowed the identification and the detection of 11 different glutathionyl and cysteinyl polysulfides. Moreover, analysing 15 young white wines was possible to confirm the presence of GSSSG in wine (GS = glutathione). More importantly, this study allowed for the first identification of several symmetric and asymmetric new polysulfides, namely GSSSSG, CSSSC (CS = cysteine), CSSSSC, CSSSG, and CSSSSG. These molecules have not previously been identified in wine, raising the question on their biogenesis and role on wine quality.An intrinsic Eu(III) luminescence phenomenon of Eu(III) complex was found under near-infrared light (NIRL) excitation of xenon lamp, and the maximum excitation wavelength is about twice the excitation wavelength of its Stokes fluorescence. The NIRL excitation fluorescence was mainly originated from second order diffracted light (SODL) excitation. The Eu(III) complex was consist of Eu(III), Gd(III), 2-trifluoroacetylacetone (TTA) and cetyltrimethylammonium bromide (CTAB). Curcumin (Cur) could notably quench the luminescence intensity of the Eu(III) complex. Based on this, a sensitive method for Cur detection was developed. Under optimum conditions, the decrease extent in the fluorescence intensity at 611 nm exhibited a good linear relationship with the Cur concentration in the range of 2.0 × 10-9 mol/L - 6.0 × 10-8 mol/L under 746 nm excitation, the limit of detection (LOD, S/N = 3) was 5.2 × 10-10 mol/L. While, the linear relationship and the LOD of Stokes fluorescence method (λex/λem = 360/611 nm) were found to be 1.0 × 10-8 mol/L - 6.0 × 10-8 mol/L and 2.6 × 10-9 mol/L, respectively. The former method is superior to the latter one in Cur detection. Both two methods were successfully applied to determine Cur in real samples. The luminescence mechanism of Eu(III) complex under the NIRL excitation and the quenching mechanism of Cur on the Eu(III) fluorescence was also investigated.A flow enzyme-linked immunosorbent assay (ELISA) method based on light absorption by enzymatically generated aniline oligomer in the presence of horseradish peroxidase (HRP), H2O2, and aniline is proposed. Aniline oligomer is rapidly formed through the polymerization reaction via the enzymatic reaction, and its fast reaction rate is beneficial for flow ELISA. An anti-3-phenoxybenzoic acid monoclonal antibody (mAb) was produced by mice, and was used for the flow competitive ELISA for the determination of 3-phenoxybenzoic acid (3PBA), which was performed on an acrylic plate having a Y-shaped channel. ABS resin beads (d = 1 mm) were filled in the channel to increase the surface area for the adsorption of the mAb. A clank-type detection chamber (optical length 1 cm) made of polydimethylsiloxane (PDMS) containing carbon black, which can significantly decrease light scattering, was fabricated with a 3D printer. The PDMS detection chamber was connected to the outlet of the acrylic flow chip with a tube. Tofacitinib inhibitor A blue LED was used as a light source for the flow ELISA.