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A new GC-MS method was developed for the analysis of ascaulitoxin, its aglycone , and 4-amino- D -proline , which are phytotoxins with potential herbicidal activity produced by Ascochyta caulina . The method involved directly treating the lyophilized culture filtrate with a derivatizing reagent, converting the mixture of toxins in the filtrate to their corresponding trimethylsilyl derivatives, and consequent analysis by EI-MS . The method is rapid, sensitive and highly specific for the identification and analysis of the toxins in a complex sample matrix. Analysis of culture filtrates using this method suggested that phytotoxicity correlates with the level of ascaulitoxin in the culture filtrate. A new method for the purification of 2,4,7-triamino-5-hydroxyoctandioic acid , the aglycone of ascaulitoxin, is also described.

Pyruvate dehydrogenase complex (PDHc) plays a key role in pyruvate decarboxylation, the transformation of pyruvate to acetyl-CoA. In this study, a new assay for measuring PDHc activity has been developed. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) is adopted as the electron acceptor in this method, and the change in absorbance caused by the reduction of MTT by hydroxyethyl-TPP, which is the catalyzed product of pyruvate dehydrogenase (PDH, E1), within a certain period of time is measured to reflect PDHc activity. For further impartial evaluation of the characteristics of this newly developed assay, a series of comparative studies were also conducted with several commonly used assays of PDHc activity, including the conventional spectrophotometric assay of NADH accumulation, the p -iodonitrotetrazolium violet (INT)-coupled assay, the 2,6-dichlorophenolindophenol (2,6-DCPIP) assay, and the potassium ferricyanide assay. Results have proved that the spectrophotometric assay using MTT is highly sensitive and inexpensive with little interference from the sulfhydryl compound. In conclusion, the newly established assay is applicable for activity measurement not only in purified PDH and PDH in purified PDHc, but also in crude PDH solution prepared under certain conditions; hence, the assay can indirectly reflect the activity of PDHc activity.

The presence and fate of antifungal agents in the environment have hardly been investigated. This is despite the increased usage of antifungal agents and higher prevalence of antifungal resistance. Stereochemistry of antifungal agents has been largely overlooked due to lack of analytical methods enabling studies at the enantiomeric level. This paper introduces a new analytical method for combined separation of achiral and chiral antifungal agents and their metabolites with the utilization of chiral chromatography coupled with triple quadrupole tandem mass spectrometry to enable comprehensive profiling of wide-ranging antifungal agents and their metabolites in environmental matrices. The method showed very good linearity and range ( r 2 0.997), method accuracy (61–143%) and precision (3–31%) as well as low (ng L ?1 ) MQLs for most analytes. The method was applied in selected environmental samples. The following analytes were quantified: fluconazole, terbinafine, N -desmethyl-carboxyterbinafine, tebuconazole, epoxiconazole, propiconazole and N -deacetyl ketoconazole. They were predominantly present in the aqueous environment (as opposed to wastewater) with sources linked with animal and plant protection rather than usage in humans. Interestingly, chiral fungicides quantified in river water were enriched with one enantiomer. This might have consequences in terms of their ecological effects which warrants further study.

A novel chemiluminescence (CL) method to determine putrescine was proposed based on the enhanced effect of putrescine on CL emission of the [Ag(HIO 6 ) 2 ] 5? –luminol system. The enhanced degree of CL emission was proportional to the putrescine concentration. Under optimal conditions, there was a linear relationship between the increase in CL intensity and the putrescine concentration over a range of 4.0 × 10 ?8 to 4 × 10 ?6 g mL with a detection limit (3 σ ) of 1.76 × 10 ?8 g mL ?1 . The relative standard deviation (RSD) was 3.2% for 11 replicate determinations of 1.0 × 10 ?6 g mL ?1 putrescine. The proposed CL reaction systems had potential capability for residue analysis of studied analytes in food samples. A possible mechanism of CL emission and enhanced effect was also suggested.

Trace explosives detection, a crucial component of many security screening environments, commonly employs wipe-sampling. Since collection of an explosive residue is necessary for detection, it is important to have a thorough understanding of the parameters that affect the efficiency of collection. Current wipe-sampling evaluation techniques for explosive particles have their limits: manual sampling (with fingers or a wand) is limited in its ability to isolate a single parameter and the TL-slip/peel tester is limited to a linear sample path. A new wipe-sampling instrument, utilizing a commercial off-the-shelf (COTS) 3D printer repurposed for its XYZ stage, was developed to address these limitations. This system allowed, for the first time, automated two-dimensional wipe-sampling patterns to be studied while keeping the force and speed of collection constant for the length of the sampling path. This new instrument is not only capable of investigating the same parameters as current technology (wipe materials, test surfaces, forces of collection, and linear sample patterns), it has added capabilities to investigate additional parameters such as directional wipe patterns ( i.e. “L” and “U” shapes, square, and serpentine) and allowing for multiple lines to be sampled during a single collection without the need for adjustments by the user. In this work, parametric studies were completed using 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) and the COTS 3D printer for wipe-sampling to establish collection efficiencies for numerous scenarios. Trace explosives detection in field screening environments could be greatly improved with the ability to comprehensively investigate how a wide range of parameters individually affect collection by wipe-sampling. A screener who knows how to properly interrogate any given surface will be much more efficient at detecting trace explosives.

A coumarin-based “Turn-on” fluorescence chemosensor 1 containing L -histidine for Al 3+ was readily synthesized and investigated, which showed high selectivity and remarkable sensitivity to aluminium( III ) ions based on a photo-induced electron-transfer (PET) mechanism in aqueous solution (Tris–HCl, 0.1 mM, pH 7.2). The sensor responded rapidly to Al 3+ in aqueous solutions with a 1?:?1 stoichiometry. Meanwhile, it showed excellent adaptability and also responsiveness.

A n L -lysine-based urea containing low-molecular-weight organogelator was synthesized and grafted onto silica particles, so that the functional groups were expected to be oriented through H-bonding. The gelator-grafted particles were applied for the separation of bioactive and shape-constrained isomers for the first time and they showed very high molecular shape-selectivity.

The spectrophotometer is the most used analysis equipment in traditional colorimetric methods. However, the operation of using a spectrophotometer is time-consuming and labor-intensive, which presents practical difficulties in rapid detection. To this end, we present a digital color analysis method, using the typical 3,5-dinitrosalicylic acid (DNS) method for glucose detection as an example. The primary colors from 3 color spaces (Red-Green-Blue, Hue-Saturation-Value, Hue-Saturation-Intensity) were studied as quantitative analytical parameters for the glucose concentration and the red color (from the Red-Green-Blue colorspace) of the assay image provides superior prediction precision ( 99.8%). Combined with the color analysis, two calculation algorithms, nonlinear regression and artificial neural networks, were compared for the detection of a high concentration of glucose. Then a microtiter plate (48-well plate) platform, based on the color analysis, was set up. Compared to existing methods using a spectrophotometer, the digital color analysis method has a large detection range (0–10 g L ?1 ), high accuracy (0.07 g L ?1 ) and fast detection rate (150 samples detected within about 15 min). It also shows great promise for use in a variety of reducing sugar measurements such as xylose, fructose and maltose. These aforementioned features render this newly developed method highly suitable for quick detection applications.

In the present study, the construction of a nanomachined flow channel sensor based on a nanoporous alumina membrane (NAM) together with information on its kinetic biosensing for real-time electrochemical detection of glucose are described. Firstly, the enzyme glucose oxidase was covalently immobilized on nanochannels of NAM as active biosensing elements, and a thin film of Pt was sputtered at the end of the nanochannels as an electrochemical detector. When the glucose solutions flowed through the nanochannels at a certain flux, the hydrogen peroxide (H 2 O 2 ) produced as a result of enzymatic conversion was detected by an amperometric method at the end face of the Pt film sputtered membrane. The results showed that the H 2 O 2 produced in the nanochannels was completely collected at the Pt film electrode due to the unique nanoscale channels. Thus, the detection sensitivity of glucose was significantly improved to as high as 86.62 μA mM ?1 cm ?2 at a flow rate of 20 μL min ?1 . It was also found that the amperometric signal of glucose was directly related to the imposed flow rate. The increased sensitivity of the sensor at a faster flow rate was at the cost of a reduction of the dynamic range of glucose. The present nanochannel sensor exhibited excellent stability and reproducibility even with a usage time of ten days. The proposed sensor was used to detect glucose in wine samples, and the results obtained were in good agreement with the values obtained by a spectrophotometric enzyme method.

Phthalates are a group of compounds widely used in consumer products and they are ubiquitous in the environment due to their widespread commercial use. In this study, a new non-targeted screening method has been developed to identify phthalate metabolites in human urine samples as exposure markers of phthalates using mass spectrometry. The method firstly scanned precursor ions that contained the deprotonated benzoate ion, [C 6 H 5 COO] ? , at m / z 121 using liquid chromatography-tandem mass spectrometry (LC-MS/MS), which is specifically a common fragmentation ion of all phthalate metabolites. The daughter ions of the precursor ions were subsequently scanned using high-resolution mass spectrometry (HRMS) to elucidate their potential structures using accurate mass and fragmentation patterns. Agilent MassHunter software was used to calculate the potential formulas based on the accurate masses of unknown metabolites, and SciFinder was used to narrow down the targets. The fragmentation patterns of phthalate monoesters in mass spectrometry have been investigated for application in the identification of new metabolites in this study. The method has been validated with commercially available standards of phthalate metabolites and applied to identify phthalate metabolites in human urine samples. Nine known phthalate metabolites and an unknown phthalate metabolite have been identified in urine samples. The structure of the new metabolite was proposed as 1,2-benzenedicarboxylic acid, mono(9-cyclopropylnonyl) ester. This study has demonstrated that the non-targeted method developed could be a useful tool in exposure biomarker discovery.