Development and application of a sensitive liquid chromatography-tandem mass spectrometry method for the quantitative analysis of 11 free fatty acids in human serum using a derivatisation strategy.

A stable isotope dilution-liquid chromatography-tandem mass spectrometry method based on a derivatisation strategy involving an N,N'-carbonylimidazole solution (CDI) with 4-(dimethylamino)-benzenemethanamine was developed for the determination of 11 free fatty acids (FFAs) in human blood samples. Serum samples were subjected to liquid‒liquid extraction and centrifuged, and the supernatant was collected for a two-step derivatisation reaction with a CDI and 4-(dimethylamino)-aniline acetonitrile solution. The derivatised solution was separated on a ACQUITY UPLC HSS T3 column (2.1 × 50 mm, 1.8 µm) column with a mobile phase consisting of water-acetonitrile in gradient elution and then detected by tandem mass spectrometry using electrospray ionisation (ESI) and multiple reaction monitoring (MRM) in positive ion mode and quantified using the isotope internal standard method. The effects of the derivatisation reaction time, temperature and concentration of derivatisation reagents on the response values of the analytes were investigated. The optimal conditions were as follows: 1.0 mg mL-1 CDI acetonitrile solution at 25 °C for 25 min, followed by a reaction with a 1.0 mg mL-1 4-(dimethylamino)-benzenemethanamine acetonitrile solution at 70 °C for 30 min. Under the optimal conditions, the limits of detection (LODs) of the 11 FFAs were in the range of 3.0-14.0 ng mL-1; the limits of quantification (LOQs) were in the range of 8.0-45.0 ng mL-1; and the mean recoveries ranged from 83.4 to 112.8%, with intraday and interday precisions ranging from 0.7 to 9.1% and 3.7-9.5%, respectively. The experimental method is simple in terms of the pretreatment operation, accurate and reliable, and can be applied to the sensitive determination of FFAs in human blood samples.

Determination of six volatile fatty acids in human serum, urine and faeces by low temperature derivatisation combined with HPLC-MS/MS.

A stable isotope dilution-liquid chromatography tandem mass spectrometry method based on a low-temperature derivatization strategy with 3-nitrophenylhydrazine (3-NPH) was developed for the determination of six volatile fatty acids (VFAs) in serum, urine, and feces. Ice acetonitrile was used to precipitate proteins and extract the target analytes. The extract was derivatized with 3-NPH methanol solution at 4 °C. BEH C8 (1.7 µm, 2.1 × 100 mm) column was used for chromatographic separation, and acetonitrile-water (both containing 0.01 % formic acid) were used as the mobile phase with a gradient elution of 10 min. Electrospray ionization source (ESI) in negative ion multiple reaction monitoring (MRM) mode were used for analyte detection. The regression coefficients R2 of the calibration curves for the six VFAs were in the range of 0.9963-0.9994, and the LOQs were in the range of 0.02-0.5 µg mL-1, with the recoveries in the range of 85.3-104.3 %, and the intra- and inter-day precision in the range of 1.8-9.1 %. The method is simple, accurate and reliable, and has been applied in the sensitive determination of VFAs in complex biological samples.

Boosting Catalytic Purification of Soot Particles over Double Perovskite-Type La2-xKxNiCoO6 Catalysts with an Ordered Macroporous Structure.

The catalytic performances for soot purification over the perovskite-type ABO3 oxides, as one of the most potential non-noble metal catalysts, are closely correlated with the substitution of A-site and B-site ions. Herein, three-dimensional ordered macroporous (3DOM) structural catalysts of double perovskite-type La2-xKxNiCoO6 were prepared by a method of colloidal crystal template. The contact efficiency between the catalyst and soot particles is significantly promoted by the 3DOM structure, and the partial substitution of A-site (La) with low-valence potassium (K) ions in La2-xKxNiCoO6 catalysts boosts the increasing surface density of coordinatively unsaturated active B-sites (Co and Ni) and active oxygen. 3DOM La2-xKxNiCoO6 catalysts exhibited superior performance during the purification of soot particles, and the 3DOM La1.80K0.20NiCoO6 catalyst exhibited the highest activity, that is, the values of T50, SCO2, and turnover frequency are 346 °C, 99.3%, and 0.204 h-1 (at 300 °C), respectively. According to the results of multiple experimental characterizations and density functional theory calculations, the mechanism of the samples during soot removal is proposed: the increase in surface oxygen density induced by the doping of K ions significantly promotes the critical step of the oxidation from NO to NO2 in catalyzing soot purification. It is one new strategy to develop the high-efficient non-noble metal catalysts for soot purification in practical application.

Efficient elimination of sulfadiazine in an anaerobic denitrifying circumstance: Biodegradation characteristics, biotoxicity removal and microbial community analysis.

Sulfadiazine (SDZ) is widely used in clinical treatment, livestock husbandry and aquaculture as an antibacterial agent, resulting in environmental risks. In this work, batch experiments were conducted to investigate the characteristics of SDZ biodegradation and reaction mechanisms in a nitrate anaerobic denitrifying system for the first time. The results showed that 98.52% of the SDZ, which had an initial concentration of 50 mg L-1, was degraded after 70 h, indicating that the removal efficiency of SDZ in anaerobic denitrifying system was 55.27% higher than that in anaerobic system. Furthermore, LC-MS-MS analysis confirmed that SDZ could be degraded into 16 byproducts via 3 main degradation pathways that contained 6 different reactions. After analyzing the microbial communities of the reactor, the denitrifying bacteria and desulfurizing bacteria Desulforhabdus, Ignavibacterium, SBR1031_norank, Nocardioides, etc. were highly associated with the removal of SDZ in the system. The biological toxicity test of the effluent indicated that the remaining organic matter and inorganic matter of the effluent could provide nutrients for E. coli and promote its growth. In other words, anaerobic denitrifying systems are highly efficient, simple and environmentally friendly, and have an impressive prospect in the biodegradation of sulfonamide antibiotics.

Enhanced quinoline removal by zero-valent iron-coupled novel anaerobic processes: performance and underlying function analysis.

Quinoline is toxic and difficult to degrade biologically; thus, it is a serious threat to the safety of ecosystems. To promote quinoline reduction, zero-valent iron (ZVI) was introduced into an anaerobic digestion (AD) system through batch experiments. The performance of three different types of ZVI (i.e., iron powder, iron scrap and rusty iron scrap) on quinoline degradation, methane production, formation of volatile fatty acids (VFAs) and chemical oxygen demand (COD) removal were investigated systematically. Compared to the AD system alone, quinoline and COD removal as well as the production of methane and acetic acid were effectively enhanced by ZVI, especially rusty iron scrap. The removal efficiencies of quinoline and COD were increased by 28.6% and 19.9%, respectively. The enhanced effects were attributed to the high accumulation of ferrous ions and high pH self-buffering capability, which were established by ZVI addition. Furthermore, high-throughput sequencing analysis indicated that the functional microorganisms in the ZVI-AD system were higher than in the AD system, and the added types of ZVI played important roles in structuring the innate microbial community in waste activated sludge (WAS). Especially, high enrichment of microorganisms capable of degrading quinoline, such as Pseudomonas and Bacillus, in the coupled system was detected.