An easy method for the preparation of 4-acylisoxazoles from C(α),O-dianions of oximes

Several C(α),O-dilithiooximes of aromatic ketones were condensed with aroyl chlorides. The presumed diacyl intermediates were not isolated, and the reaction mixtures containing them were acid-cyclized to give 4-acylisoxazoles in 22–62% yield.     

Metal 3D‐printed catalytic jet and flame ionization detection for in situ trace carbon oxides analysis by gas chromatography

A gas chromatographic approach for the determination and quantification of trace levels of carbon oxides in gas phase matrices for in situ or near‐line/at‐line analysis has been successfully developed. Catalytic conversion of the target compounds to methane via the methanation process was conducted inside a metal 3D‐printed jet that also acted as a hydrogen burner for the flame ionization detector. Modifications made to a field transportable gas chromatograph enabled the leveraging of advantaged microfluidic‐enhanced chromatography capability for improved chromatographic performance and serviceability. The compatibility with adsorption chromatography technology was demonstrated with in‐house constructed columns. Sustained reliable conversion efficiencies of greater than 99% with respectable peak symmetries were attained at 400°C. Quantification of carbon monoxide and carbon dioxide at a parts‐per‐million level over a range from 0.2 ppm to 5% v/v for both compounds with a respectable precision of less than 3% relative standard deviation for peak area (n = 10) and a detection limit of 0.1 ppm v/v was achieved. Linearity with correlation coefficients of R² greater than 0.9995 and measured recoveries of >99% for spike tests were achieved. The 3D‐printed steel jet was found to be reliable and resilient against potential contamination from the matrices owing to the in situ backflushing capability.     

Multidimensional gas chromatography with capillary flow technology and LTM-GC

2-D GC is a logical and cost effective extension to 1-D GC for improving the separation resolution, selectivity, and peak capacity of an analytical system. The advent of electronic pressure control systems that are accurate to the third decimal place, combined with recently innovated chromatographic devices such as capillary flow technology, has eliminated many deficiencies encountered in current conventional 2-D GC by making the technique reliable and simple to implement in both production and research analytical facilities. Low thermal mass GC (LTM-GC) was successfully integrated with capillary flow technology to further enhance overall 2-D GC chromatographic system performance by providing not only faster throughput via rapid heating and cooling, but independent temperature control for each dimension to maximize separation power. As an example, despite the enhanced peak capacity obtained from conventional 2-D GC, alkyl naphthalene isomers such as 2,3-dimethyl and 1,4-dimethyl naphthalene coeluted. These two critical compounds were well resolved (R = 5.2) using 2-D GC with LTM-GC with a similar analytical time. This paper demonstrates the benefits of combining capillary flow technology with LTM-GC to provide major enhancements to conventional 2-D GC. The synergy of these techniques is highlighted with practical industrial applications.     

Amine oxidase amperometric biosensor coupled to liquid chromatography for biogenic amines determination

A selective and sensitive method is presented for biogenic amines (BA) determination. The novelty consists in coupling a highly selective electrochemical biosensor to a weak acid cation-exchange column for online detection of amines. A bienzyme design, based on a recently isolated amine oxidase from grass pea and commercial horseradish peroxidase, was used for the biosensor construction. The enzymes were co-immobilized on the surface of a graphite electrode together with the electrochemical mediator (Os-redox polymer). The electrochemical detection was performed at a low applied potential (?50 mV vs. Ag/AgCl, KCl_0.1 M), where biases from interferences are minimal. The separation and determination of six BA, with relevance in food analysis (tyramine, putrescine, cadaverine, histamine, agmatine and spermidine), were investigated. Irrespective of the BA nature, the amine oxidase-based biosensor showed a linear response up to 5 mM, and its sensitivity decreases in the following order: cadaverine, putrescine, spermidine, agmatine, histamine and tyramine. The approach was used to estimate the BA content in fish samples, after their extraction with methanesulfonic acid.     

Determination of ultra trace levels of 1,2-dichloroethane in air by sample enrichment micromachined gas chromatography-differential mobility detection

A novel analytical procedure has been developed for the analysis of ultra trace levels of 1,2-dichloroethane (EDC) in air using sample enrichment in combination with micromachined gas chromatography (GC) and differential mobility detection (DMD). When compared to other contemporary GC techniques, such as GC-flame ionization detection, GC-electron capture detection, or GC-electrolytic conductivity detection, the employment of a DMD in combination with a preconcentrator provided better sensitivity and markedly improved selectivity. The increase in sensitivity reduces false-negative results, while the improvement in selectivity decreases the potential for false-positive results. Using the technique described, a complete analysis can be conducted in less than 10 min, with a detection limit of 0.7 ppb (v/v) of EDC and a short term precision of less than 6%. A correlation coefficient of 0.9988 was obtained over an EDC concentration range from 0.7 ppb to 36.4 ppb (v/v). The analytical system also has an on-board microTCD in series with the DMD, allowing both detector outputs to be monitored simultaneously. With the pre-concentration technique, the microTCD can detect EDC as low as 15 ppb (v/v) with a substantially enhanced linear dynamic range in addition to providing a confirmation means for the presence of EDC at the level cited.     

A unified approach for the measurement of individual or total volatile organic sulfur compounds in hydrocarbon matrices by dual-plasma chemiluminescence detector and low thermal mass gas chromatography

A novel gas chromatographic technique has been developed, offering dual-analytical capability of either speciation or rapid measurement of total volatile sulfur compounds in hydrocarbon matrices using the same hardware. The technique employs a pressurized liquid injection system for the delivery of volatile liquid hydrocarbons, low thermal mass gas chromatography, and a dual-plasma sulfur chemiluminescence detector to enable this dual capability with a high degree of sensitivity and selectivity towards sulfur-containing compounds. Using the technique described, a detection limit in the range of 20 ppb sulfur and less than 30 s analysis is attained. Response is linear over five orders of magnitude, with a high degree of repeatability.     

New Developments in the Field of Luminescent Materials for Lighting and Displays

Owing to their use in fluorescent lamps and many display applications, luminescent materials affect our daily life. Improvement of already very mature as well as development of new materials demanded by a variety of new applications are the focus of research today. The latest advances in the field of electroluminescence enable new displays and light generation concepts that challenge the classical areas of application of luminescent materials.     

Stacked injection with low thermal mass gas chromatography for PPB level detection of oxygenated compounds in hydrocarbons

The presence of oxygenated compounds in light hydrocarbons can have a negative impact in manufacturing processes and on the quality of products produced. The development of an analytical technique termed "stacked injection" has been reported earlier. With this technique, sensitivity in the parts-per-billion (ppb) range for oxygenated compounds can be achieved, even with a flame ionization detector; however, there are drawbacks for this approach that limit its overall effectiveness. A new, improved analytical technique has been developed that not only addresses the shortcomings encountered, but offers markedly higher analytical performance. The new concept employs multidimensional gas chromatography (GC) with low thermal mass GC. With this new approach, throughput improvements of up to 5 times, range extension of solutes amenable for this analysis of up to nC16 alcohol, and ppb levels of detection for oxygenated compounds are achieved. Apart from alcohols, this technique is successfully employed for the ppb level analysis of other classes of oxygenated compounds, such as ethers, aldehydes, and aromatics.