Analysis of flavor formation during the production of Jinhua dry-cured ham using headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS).

This study aimed to clarify the formation process of flavor compounds and identify the volatile substances present during a continuous period of Jinhua dry-cured ham (JDH) making. Via headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS), a total of 53 volatile organic compounds (VOCs), including 20 aldehydes, 16 alcohols, 11 ketones, 5 esters and 1 furan, were identified in JDH from seven sampling stages. The results showed that butanal, 3-methylbutanal, 2-methylbutanal, 2-hexanone, 2-pentanone and 2-butanone could be flavor markers in the evolution of aroma characteristics of JDH. Aldehydes (2-methylbutanal and 3-methylbutanal), alcohols (2-methylpropanol, 2-methylbutanol, 3-methylbutanol and 1-penten-3-ol), ketones (2-pentanone, 2-propanone, 2-butanone and 2-hexanone) and esters (ethyl acetate and ethyl 3-methylbutyrate) were considered the main VOCs in the mature JDH. Free fatty acid (FFA) analysis displayed the changes in intramuscular fat (IMF) of JDH. Additionally, principal component analysis (PCA) showed that drying-ripening was a critical stage in the flavor formation of JDH.

Anodic Polymerization of Phenylphenols in Methyl Isobutyl Ketone and Mesityl Oxide: Incorporation of a Cavitand into the Layers Formed for Sensing Phenols in Organic Media.

The electropolymerization of three phenylphenol isomers was studied in methyl isobutyl ketone and mesityl oxide, and the remarkable differences highlighted the importance of the carbon-carbon double bond in mesityl oxide. In the case of each substrate, a brownish deposit formed during the electrooxidation. The obvious difference between the polymers formed from the two solvents was recognized via voltammetric signal enhancement of 4-methoxyphenol and 4-chlorophenol, and it was only observed in the case of mesityl oxide. The experiments highlighted that incorporation of a cavitand with biphenyl groups on the upper rim of the polymers of phenylphenols improved the results to a small extent. The cavitand was, itself, electroactive without any fouling effect. As 2-phenylphenol is by far the cheapest of the three isomers, a cavitand was incorporated into its polymer, which was exploited to solve analytical problems while mesityl oxide was used as solvent. Useful quantifications were achieved in organic solvents; however, it failed under aqueous conditions due to the high hydrophobicity of the deposit. Application of differential pulse voltammetry for 4-methoxyphenol and 4-chlorophenol gave detection limits of 9.28 and 50.8 µM in acetonitrile, respectively. This procedure resulted in the immobilization of cavitand derivatives onto the electrode's surface, and the layer formed offered selective sensing of phenols by electrochemical methods.

[Determination of methyl isobutyl ketone in urine by headspace coupled with gas chromatography-mass spectrometry].

Objective: To establish a method for the determination of methyl isobutyl ketone (MIBK) in urine samples by headspace-gas chromatography-mass spectrometry. Methods: Automatic headspace sampling technique was adopted to optimize the headspace conditions (headspace bottle heating temperature and equilibration time) and gas chromatographic conditions. A total of 5 ml samples were taken and added with 3.0 g ammonium sulfate into a 20 ml headspace bottle. After heated at 60 ℃ for 30 mins, gas from the upper part of headspace bottle was injected into gas chromatography with an injection volume of 100 µl. The target was separated by HP-5MS UI (30 m×0.25 mm×0.25 µm) capillary column and then detected by mass spectrometry detector. The retention time and external standard method were used for qualitative and quantitative analysis of MIBK in samples, respectively. Results: The standard curve of MIBK showed significant linearity between 20.0-1 000.0 µg/L. The standard curve was y=62.9x-652.5, and the correlation coefficient r=0.9998. The detection limit of MIBK was 5.0 µg/L and the quantification limit of MIBK was 16.0 µg/L. The average recovery rate was 95.3%~100.2% at three spiked concentrations of low (50.0 µg/L) , medium (200.0 µg/L) and high (500.0 µg/L) . The intra-day and inter-day precisions were 1.7%~3.8% (n=6) and 1.2%~4.0% (n=6) respectively. This method was stable for the determination of MIBK, and the urine could be kept 14 d at -20 ℃ without significantly loss. Conclusion: This method is proved to be simple, practical and highly sensitive. It can satisfy the request for the determination of urine samples of workers exposed to MIBK.

Response of earthworm coelomocytes and catalase to pentanone and hexanone: a revelation of the toxicity of conventional solvents at the cellular and molecular level.

Organic solvents like 2-pentanone and 2-hexanone which are widely used in industrial production make up a large proportion of the source of chemical pollution. What is worrisome is that the cellular and molecular toxicity of 2-pentanone and 2-hexanone has not been reported yet. Based on this, earthworms and catalase (CAT) were chosen as target receptors for the toxicity studies. The cytotoxicity of 2-pentanone and 2-hexanone was revealed by measuring the multiple intracellular indicators of oxidative stress. At the molecular level, changes in the structure and function of CAT were characterized in vitro by the spectroscopy and molecular docking. The results show that 2-pentanone and 2-hexanone that induced the accumulation of reactive oxygen species can eventually reduce coelomocytes viability, accompanying by the regular changes of antioxidant activity and lipid peroxidation level. In addition, the exposure of 2-pentanone and 2-hexanone can shrink the backbone structure of CAT, quench the fluorescence, and misfold the secondary structure. The decrease in enzyme activity should be attributed to the structural changes induced by surface binding. This study discussed the toxicological effects and mechanisms of conventional solvents at the cellular and molecular level, which creatively proposed a joint research method.

Copper Supported on Ceria Mesocellular Foam Silica as an Effective Catalyst for Reductive Condensation of Acetone to Methyl Isobutyl Ketone.

Copper-containing materials based on Ce- and Ca-Nb-mesocellular foam (MCF) silica supports are prepared, characterized and applied as catalysts for gas-phase reductive condensation of acetone to produce methyl isobutyl ketone (MIBK). The properties of the materials, the interaction of metal species, and their role in the catalytic process are examined by nitrogen physisorption, XRD, XPS, CO2 -TPD, H2 -TPR, and chemisorption of NO and pyridine combined with FTIR spectroscopy. A synergistic interaction of Cu2+ , Cu0 , and CeO2 species incorporated in the MCF support enable the Cu/Ce-MCF catalyst to yield 34 % of acetone conversion with over 90 % MIBK selectivity at 250 °C. Moreover, this high catalyst selectivity is maintained during operation for 24 h despite a decline in catalyst activity. The catalytic performance is superior to that of hydroxyapatite-supported Cu and similar previously reported Pd-containing catalysts.

Valorization of Biomass to Furfural by Chestnut Shell-based Solid Acid in Methyl Isobutyl Ketone-Water-Sodium Chloride System.

Recently, highly efficient production of furfural from available, abundant, inexpensive, and renewable lignocellulosic biomass has gained much attention by using biomass-based heterogeneous catalyst in an effective biphasic system. Using microwave-treated chestnut shell (MC-CNS) as biobased support, biomass-based catalyst (MC-Sn-CNS) was firstly synthesized for catalyzing biomass into furfural. The structure parameters of MC-Sn-CNS were measured by BET, SEM, XRD, and FT-IR. After systematical optimization, furfural yield reached 64.4% from corncob by MC-Sn-CNS (3.6 wt%) at 180 °C for 15 min in methyl isobutyl ketone (MIBK)-water (2:1, v:v) containing 200 mM NaCl. MC-Sn-CNS had high stability, which could be recycled for 7 batches. The yield of furfural from fresh corncob was 44.5-64.4%. The possible catalytic mechanism for synergistic catalysis of biomass to furfural by MC-Sn-CNS was expounded in MIBK-water-NaCl system. The results showed that green solvent (MIBK) and NaCl promoted the production of furfural from CC catalyzed by solid acid (MC-Sn-CNS). This study demonstrated an environmentally friendly strategy for efficiently utilizing corncob into furfural by CNS-based heterogeneous chemocatalyst in a green reaction media. Clearly, this newly synthesized biomass-based MC-Sn-CNS catalyst had potential application in the future.

Determination of methyl isobutyl ketone in urine by headspace coupled with gas chromatography-mass spectrometry / 中华劳动卫生职业病杂志

Objective: To establish a method for the determination of methyl isobutyl ketone (MIBK) in urine samples by headspace-gas chromatography-mass spectrometry. Methods: Automatic headspace sampling technique was adopted to optimize the headspace conditions (headspace bottle heating temperature and equilibration time) and gas chromatographic conditions. A total of 5 ml samples were taken and added with 3.0 g ammonium sulfate into a 20 ml headspace bottle. After heated at 60 ℃ for 30 mins, gas from the upper part of headspace bottle was injected into gas chromatography with an injection volume of 100 μl. The target was separated by HP-5MS UI (30 m×0.25 mm×0.25 μm) capillary column and then detected by mass spectrometry detector. The retention time and external standard method were used for qualitative and quantitative analysis of MIBK in samples, respectively. Results: The standard curve of MIBK showed significant linearity between 20.0-1 000.0 μg/L. The standard curve was y=62.9x-652.5, and the correlation coefficient r=0.9998. The detection limit of MIBK was 5.0 μg/L and the quantification limit of MIBK was 16.0 μg/L. The average recovery rate was 95.3%~100.2% at three spiked concentrations of low (50.0 μg/L) , medium (200.0 μg/L) and high (500.0 μg/L) . The intra-day and inter-day precisions were 1.7%~3.8% (n=6) and 1.2%~4.0% (n=6) respectively. This method was stable for the determination of MIBK, and the urine could be kept 14 d at -20 ℃ without significantly loss. Conclusion: This method is proved to be simple, practical and highly sensitive. It can satisfy the request for the determination of urine samples of workers exposed to MIBK.

Toxic effects of acetone, 2-pentanone, and 2-hexanone on physiological indices of wheat (Triticum aestivum L.) germination and seedlings.

Petroleum hydrocarbons are important characteristic pollutants in the process of oil exploitation in the Yellow River Delta (China), and they cause a potential hazard to the surrounding ecological environment. The research on eco-toxicological effects of petroleum-derived products still needs to be studied in depth. This paper describes the physiological indices of wheat (Triticum aestivum L.) seeds and seedlings under independent stresses of acetone, 2-pentanone, and 2-hexanone to determine the toxicological effects of ketones derived from petroleum products on typical crops. The experimental results indicated that ketones with concentrations lower than 0.4 mg·cm-2 and 800 mg·kg-1 the germination of wheat seeds and the growth of seedlings were promoted to 113.32-127.27% and 105.41-126.39%, respectively, thus exhibiting low-dose excitatory effects. However, when the concentration was higher than 0.4 mg·cm-2 and 800 mg·kg-1, germination and seedlings' growth were significantly reduced to 7.14-2.12% and 35.09-13.33%, respectively. At the same time, acetone had a greater impact on the growth of wheat seed roots, the malondialdehyde (MDA), and chlorophyll contents in leaf tissues. The low concentration of acetone had a significant promoting effect on the activity of α-amylase in wheat seeds. 2-Pentanone reduced the electrical conductivity of wheat seed extract, and it significantly promoted the catalase (CAT) activity at low concentrations. 2-Hexanone had a strong inhibitory effect on wheat germination and growth. This study provided new research results to determine the toxic effects of petroleum-derived products and provided a basis for the environmental management of such substances.

Identification of a non-host semiochemical from miniature pinscher, Canis lupus familiaris, that repels Rhipicephalus sanguineus sensu lato (Acari: Ixodidae).

It is already known that the beagle breed of domestic dogs produces semiochemicals capable of repelling the brown dog tick, Rhipicephalus sanguineus sensu lato (s.l.). With a view to discovering new non-host semiochemicals as tick repellents, we compared the semiochemicals produced by a putative tick-resistant breed of dog, miniature pinscher, with known tick-resistant (beagle) and tick-susceptible (English cocker spaniel) breeds. Two non-host compounds produced by beagles, i.e. 2-hexanone and benzaldehyde, were shown to be present in samples collected from all three breeds. Furthermore, two compounds, 6-methyl-5-hepten-2-one and 1,2,4-trimethylbenzene, were found in higher amounts in samples collected from miniature pinscher dogs. The mean amounts of benzaldehyde, 2-hexanone and 1,2,4-trimethylbenzene were similar for beagles and miniature pinschers (P > 0.05) and higher than the means observed for cocker spaniels (P < 0.05), whereas the mean amount of 6-methyl-5-hepten-2-one produced by miniature pinschers was significantly higher (P < 0.05) than for the other breeds of dogs. In Petri-dish assays with adult R. sanguineus s.l., 6-methyl-5-hepten-2-one was repellent for all observation periods evaluated for the two highest concentrations (0.100 and 0.200 mg.cm-2, P < 0.01). The obtained results support our hypothesis that miniature pinschers are a tick-resistant dog breed and agree with previous observations of miniature pinschers being the breed least parasitized by ticks. Furthermore, the non-host semiochemical 6-methyl-5-hepten-2-one has potential to be developed for use as a repellent for the protection of susceptible dogs from R. sanguineus s.l. ticks.

Comparative study of degradation of toluene and methyl isobutyl ketone (MIBK) in aqueous solution by pulsed corona discharge plasma.

Effectiveness of pulsed power plasma for the degradation of two toxic volatile organic compounds (VOCs), toluene and methyl isobutyl ketone (MIBK), in aqueous solution was evaluated. The plasma degradation of MIBK has been studied for the first time. The influence of initial concentration of target compound, solution pH and scavengers on percentage degradation was evaluated. 100% removal of 200 mg/L of toluene and MIBK was achieved both in liquid and gaseous phases after 12 and 16 min of plasma treatment, respectively. The first order rate constant of toluene and MIBK degradation (for 200 mg/L each) was 0.421 and 0.319 min-1 respectively when they were treated individually, and these values decreased slightly during degradation of their mixture. MIBK degradation was slower than toluene and it might be due to semi volatile and hydrophilic nature of MIBK. The effect of initial concentration of toluene and MIBK showed different degradation patterns. Highest degradation of both the compounds was obtained in neutral pH and in absence of scavengers. •OH radical was the major reactive species involved in their degradation. Their degradation in real environmental matrices showed that removal reduced significantly in secondary effluent due to scavenging of reactive species by various ions and organic matter. The total number of degradation intermediates identified in case of toluene and MIBK was 11 and 14 respectively and formate was the one recalcitrant byproduct generated. The degradation pathway of toluene and MIBK involving reactions of reactive oxygen and nitrogen species and reductive species is proposed.

Determination of amphenicol antibiotics and their glucuronide metabolites in urine samples using liquid chromatography with quadrupole time-of-flight mass spectrometry.

A rapid procedure for the determination of amphenicol antibiotics in human urine by liquid chromatography with quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) is proposed. The presence of thiamphenicol (TAP), florfenicol (FF) and chloramphenicol (CAP) in the human body can be attributed to their administration to treat certain diseases or by eating food of animal origin. The TAP, FF and CAP excreted in urine is mainly in the form of glucuronide conjugates, although their free forms may also be excreted to a lesser extent. In the procedure described, the enzymatic hydrolysis of amphenicol glucuronide forms in urine was carried out using ß-glucuronidase and sulfatase at pH 5 (37 °C, overnight) in order to discriminate the free and conjugated forms. Then, amphenicol antibiotics were submitted to dispersive liquid-liquid microextraction (DLLME) for preconcentration. All the parameters affecting DLLME efficiency were optimized, and the following conditions were selected: 0.9 g NaCl in 10 mL of urine, to which 1.2 mL methanol (as dispersant solvent) and 1 mL of 4-methyl-2-pentanone (as extractant solvent) were added. The absence of a matrix effect allowed quantification of the samples against aqueous standards. Detection limits were 29, 6 and 3 pg mL-1 for TAP, FF and CAP, respectively. Relative standard deviations were calculated to evaluate the intra- and inter-day precision and values lower than 10% were obtained in all cases. The trueness of the method was tested through recovery studies, obtaining satisfactory values (83-104%). Ten urine samples obtained from volunteers were analysed and all of them were free of the studied antibiotics.

Effect of presence of hydrophilic volatile organic compounds on removal of hydrophobic n-hexane in biotrickling filters.

Hydrophilic VOCs (volatile organic compounds) were applied to explore their positive influence on the elimination of the single hydrophobic VOC in biotrickling filters (BTFs). Comparison experiments were carried to evaluate the effect of 4-methyl-2-pentanone and toluene on the performance of BTFs for n-hexane removal. The results showed that the existence of 4-methyl-2-pentanone improved the removal performance of BTFs at short gas empty bed contact time (EBRT) of 15 s and low temperature of 10 °C. The degradation of n-hexane in the presence of 4-methyl-2-pentanone was slightly enhanced with a loading ratio of 6:1. When the mixing ratio was greater than 4, toluene significantly promoted the biodegradation of n-hexane with toluene loading rate less than 10 g m-3 h-1. Additionally, The promotion effect was not only reflected in the contents of proteins and polysaccharides, but also in the growth rates of microorganisms in biofilms. This work discussed the detailed effect between n-hexane and hydrophilic VOCs in BTFs, which would contribute to develop a more economical method to improve the removal performance of hydrophobic VOCs in BTFs.

Machine Vision Methods, Natural Language Processing, and Machine Learning Algorithms for Automated Dispersion Plot Analysis and Chemical Identification from Complex Mixtures.

Gas-phase trace chemical detection techniques such as ion mobility spectrometry (IMS) and differential mobility spectrometry (DMS) can be used in many settings, such as evaluating the health condition of patients or detecting explosives at airports. These devices separate chemical compounds in a mixture and provide information to identify specific chemical species of interest. Further, these types of devices operate well in both controlled lab environments and in-field applications. Frequently, the commercial versions of these devices are highly tailored for niche applications (e.g., explosives detection) because of the difficulty involved in reconfiguring instrumentation hardware and data analysis software algorithms. In order for researchers to quickly adapt these tools for new purposes and broader panels of chemical targets, it is critical to develop new algorithms and methods for generating libraries of these sensor responses. Microelectromechanical system (MEMS) technology has been used to fabricate DMS devices that miniaturize the platforms for easier deployment; however, concurrent advances in advanced data analytics are lagging. DMS generates complex three-dimensional dispersion plots for both positive and negative ions in a mixture. Although simple spectra of single chemicals are straightforward to interpret (both visually and via algorithms), it is exceedingly challenging to interpret dispersion plots from complex mixtures with many chemical constituents. This study uses image processing and computer vision steps to automatically identify features from DMS dispersion plots. We used the bag-of-words approach adapted from natural language processing and information retrieval to cluster and organize these features. Finally, a support vector machine (SVM) learning algorithm was trained using these features in order to detect and classify specific compounds in these represented conceptualized data outputs. Using this approach, we successfully maintain a high level of correct chemical identification, even when a gas mixture increases in complexity with interfering chemicals present.

One-pot selective conversion of lignocellulosic biomass into furfural and co-products using aqueous choline chloride/methyl isobutyl ketone biphasic solvent system.

This study investigated simultaneous lignocellulose fractionation and conversion in a one-pot reaction using an aqueous choline chloride/methyl isobutyl ketone (ChCl/MIBK) biphasic solvent system. Under the optimized condition (170 °C, 60 min, 0.6 wt% H2SO4, 10.7 wt% solid loading), the biphasic solvent solubilized 96% xylan in raw switchgrass, which was simultaneously converted to furfural with a yield of 84.04%. The biphasic solvent was also able to selectively extract lignin, which had a high purity (93.1%), and uncondensed moieties (i.e., Hibbert's ketone), as well as decreased molecular weight and polydispersity index. The resultant pulp was enriched with cellulose (73.3%), which can be completely hydrolyzed into glucose within 48 h via enzymatic hydrolysis. Aqueous ChCl was successfully recycled and reused for atleast three cycles with similar performance in switchgrass fractionation. This study demonstrated that aqueous ChCl/MIBK biphasic system was an effective solvent system for co-production of furfural, high quality technical lignin and digestible cellulose for further upgrading.

Efficient Synthesis of Methyl 3-Acetoxypropionate by a Newly Identified Baeyer-Villiger Monooxygenase.

Baeyer-Villiger monooxygenases (BVMOs) are an emerging class of promising biocatalysts for the oxidation of ketones to prepare corresponding esters or lactones. Although many BVMOs have been reported, the development of highly efficient enzymes for use in industrial applications is desirable. In this work, we identified a BVMO from Rhodococcus pyridinivorans (BVMORp) with a high affinity toward aliphatic methyl ketones (Km < 3.0 µM). The enzyme was highly soluble and relatively stable, with a half-life of 23 h at 30°C and pH 7.5. The most effective substrate discovered so far is 2-hexanone (kcat = 2.1 s-1; Km = 1.5 µM). Furthermore, BVMORp exhibited excellent regioselectivity toward most aliphatic ketones, preferentially forming typical (i.e., normal) products. Using the newly identified BVMORp as the catalyst, a high concentration (26.0 g/liter; 200 mM) of methyl levulinate was completely converted to methyl 3-acetoxypropionate after 4 h, with a space-time yield of 5.4 g liter-1 h-1 Thus, BVMORp is a promising biocatalyst for the synthesis of 3-hydroxypropionate from readily available biobased levulinate to replace the conventional fermentation.IMPORTANCE BVMOs are emerging as a green alternative to traditional oxidants in the BV oxidation of ketones. Although many BVMOs are discovered and used in organic synthesis, few are really applied in industry, especially in the case of aliphatic ketones. Herein, a highly soluble and relatively stable monooxygenase from Rhodococcus pyridinivorans (BVMORp) was identified with high activity and excellent regioselectivity toward most aliphatic ketones. BVMORp possesses unusually high substrate loading during the catalysis of the oxidation of biobased methyl levulinate to 3-hydroxypropionic acid derivatives. This study indicates that the synthesis of 3-hydroxypropionate from readily available biobased levulinate by BVMORp-catalyzed oxidation holds great promise to replace traditional fermentation.