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.

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.

Cross-interaction of volatiles in fast co-pyrolysis of waste tyre and corn stover via TG-FTIR and rapid infrared heating techniques.

Using fast infrared heating technology to minimize the pyrolysis temperature differential and optimizing secondary reactions is advantageous for studying co-pyrolysis behaviors. In this study, the co-pyrolysis behaviors of waste tyres (WT) and corn stover (CS), including product distribution, pyrolysis kinetics, and thermodynamics, were studied using TGA-FTIR analysis and fast infrared heating reactor. The DTG curves for the co-pyrolysis of WT and CS significantly differed from the calculated values, implying that the pyrolysis intermediates produced by CS during the pyrolysis process may have synergetic effects with the pyrolysis of WT. The apparent activation energies using the Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods were similar, 244.88 kJ/mol and 245.93 kJ/mol, respectively. The experiment results suggest that the bio-oil yield increased first and then decreased with a further temperature increase. The yield of bio-oil gradually increased from 35.36% to 46.06% as temperature rose from 500 °C to 700 °C; but the further increasing to 800 °C decreased the bio-oil yield to 40.72%. The aromatic compounds in tar gradually increased with increasing the temperature, while the aliphatic compounds increased initially and then reduced. Meanwhile, the oxygenated compounds first decreased and then increased with increasing the pyrolysis temperature. The yield of light oil components (C＜10) increased from 5.11% at 400 °C to 7.71% at 700 °C. A further increase in the pyrolysis temperature to 800 °C reduced the light oil content to 4.93%.

Fast co-pyrolysis behaviors and synergistic effects of corn stover and polyethylene via rapid infrared heating.

Rapid infrared heating with fast heating rates and the capacity to load materials on the gram scale help investigate the co-pyrolysis behaviors, minimizing the gap of materials' pyrolysis temperature and volatile release during the co-pyrolysis. This work explored the effects of temperature and heating rate on the co-pyrolysis product s behaviors and synergistic interactions of corn stove and polyethylene. Initial increases in oil yield were followed by decreases when the heating rate rose, and when the temperature increased from 500 °C to 600 °C, the oil yield rose from 17.91 wt% to 20.58 wt% before falling to 14.75 wt% at 800 °C. High heating rate promoted the oil generation, and the maximum oil yield was at 25 °C/s with varying heating rates from 15 °C/s to 35 °C/s. The pyrolysis gas produced at 25 °C/s exhibited the highest LHV (Low heating value) and lowest CO2 yield, which were 17.23 MJ/nm3 and 39.29 vol%, respectively. The suitability of heating rate and temperature may improve the interaction between H-radicals of PE and oxygenated groups of CS to generate stable macromolecular compound and enhance oil production. GC-MS studies of the oil products demonstrated that oxygenated compounds such as furans, phenols and acids from lignocellulosic depolymerization had been converted to high molecular weight long chain alcohols (mostly C26, C20 and C14 alcohols) via stronger interactions during fast infrared-heated co-pyrolysis. The alcohols increased from 32.29 % to 65.06 % as temperatures rose from 500 °C to 800 °C. Few furan heterocycles, acids and phenols were detected, suggesting that the oil presented higher quality and stronger synergistic effects. Rapid infrared heating accelerated the synergistic effects between volatile-volatile interactions during co-pyrolysis of corn stover and polyethylene, and the increases in temperature and heating rates further enhanced the release of many volatile substances and the formation of fine pores. Raman results showed char of 600 °C deposited more pure aromatic structures, the influence of temperature on aromatization was stronger than that of heating rate.

[Development of a multi-residue detection method for 27 typical pharmaceuticals and personal-care products in plants and analysis of their migration patterns in sprouts].

An analytical method based on ultra-performance liquid chromatography-tandem mass spectrometry was developed for the simultaneous determination of 27 pharmaceutical and personal-care product (PPCP) residues in plants. The enrichment and cleanup of PPCPs in plants were achieved using an HLB extraction column, and the separation was performed on a BEH C18 column (100 mm×2.1 mm, 1.7 µm) with 0.1% formic acid water-acetonitrile as the mobile phase via gradient elution. PPCPs were detected with electrospray ionization mass spectrometry in positive-ion multiple-reaction monitoring (MRM) mode. The limits of detection and quantification of the 27 PPCPs in plants were 0.01-0.30 µg/kg and 0.03-0.98 µg/kg, respectively. Good linearities were observed with coefficients of determination (r2) >0.99. The spiked recoveries were between 80.8% and 122.3% with relative standard deviations (RSDs) between 1.0% and 9.9%. The method was subsequently used to study sprouts grown in different concentrations of PPCPs. A total of 10 PPCPs were detected in sprouts grown in medium with a low concentration PPCPs, 13 PPCPs were detected in sprouts grown in medium with a moderate concentration of PPCPs, and 19 PPCPs were detected in sprouts grown in medium with a high concentration of PPCPs. These results showed that plants grown in water bodies contaminated with PPCPs or irrigated with water contaminated with PPCPs absorbed and accumulated these substances and that the amount and type of PPCPs absorbed by plants were closely related to the levels of PPCPs in the external environment. Analysis of the contents of PPCPs in different plant tissues revealed a general distribution of root>stem>leaf. Haemosibutramine showed a tissue distribution of leaf>stem>root, while glibenclamide showed a distribution of root>leaf>stem; these results revealed differences in the distribution of PPCPs in plants. Calculation of the transfer factor (TF) of the PPCPs in plants demonstrated significant differences in the transferability of different PPCPs, with TF=2.34 for haemosibutramine and TF=1.25 for chlorosibutramine. The results showed that among the drugs that migrated in plants, haemonosibutramine and chlorosibutramine had the strongest migration ability in sprouts, followed by nicardipine and chlorpheniramine maleate, and amantadine, N-monodesmethyl sibutramine, carbamazepine and flumequine had the weakest migration ability. Once absorbed, these compounds were transferred to the stems and/or leaves, where they accumulate and cause potential harm by contaminating other plant organs. Therefore, PPCPs such as homosibutramine and chlorosibutramine, which easily migrate in plants, should be given extra attention in future studies. The method is simple in pre-treatment, sensitive and accurate, and can be widely applied to the detection of PPCP residues in plant samples.

Uptake and Transport of Different Concentrations of PPCPs by Vegetables.

In many parts of the world, water resources are scarce or even extremely scarce, and the reuse of water resources has become mainstream in today's world. Many regions use treated wastewater for agricultural irrigation, aquaculture, and other activities. However, in recent years, wastewater has been found to contain large amounts of pharmaceuticals and personal care products (PPCPs). Therefore, there is a potential risk of PPCPs being transported in the environment and affecting human health. In this study, we compared the uptake, transport, and accumulation of 27 PPCPs in three types of sprouts (radish, buckwheat, and okra).The bioaccumulation of amantadine, diphenhydramine, chlorpheniramine maleate, sibutramine, hemosibutramine, chlorosibutramine, N-monomethyl sibutramine, N, N-desmethyl sibutramine, and carbamazepine was found to be significantly higher in plants grown for 12 days in media containing 0.5, 5.0, and 50.0 ng/mL PPCPs. With increasing concentration of PPCPs in the culture solution, the amount of PPCPs absorbed by plants and the degree of accumulation also showed an increasing trend. At the same time, it was demonstrated that there was an obvious uptake transfer phenomenon of PPCPs by plants, and the trend of uptake transfer became more and more obvious as the concentration of external environmental pollutants increased. In addition, amantadine, chlorpheniramine maleate, carbamazepine, N, N-desmethyl sibutramine, hemosibutramine, and chlorosibutramine showed more active translocation in some plants (TF > 1.0).