Zuguang Li

A novel method of ultrasound-assisted dispersive liquid-liquid microextraction coupled to liquid chromatography-mass spectrometry for the determination of trace organoarsenic compounds in edible oil.

A novel approach, ultrasound-assisted dispersive liquid-liquid microextraction combined with liquid chromatography-mass spectrometry (UA-DLLME with LC-MS) is demonstrated to be quite useful for the determination of trace amounts of organoarsenic compounds in edible oil. The organoarsenic compounds studied include dimethylarsinic acid (DMA), monomethylarsonic acid (MMA) and 3-nitro-4-hydroxyphenyl arsenic acid (Roxarsone). Orthogonal array experimental design (OAD) was utilized to investigate the parameter space of conditions for UA-DLLME. The optimum conditions were found to be 4 min of ultrasonic extraction using 1.25 mL of mixed solvent with 50 μL of buffer solution. Under these optimal conditions, the linear range was from 10 ng g(-1) to 500 ng g(-1) for DMA and Roxarsone, from 25 ng g(-1) to 500 ng g(-1) for MMA. Limits of detection of DMA, MMA and Roxarsone were 1.0 ng g(-1), 3.0 ng g(-1) and 5.8 ng g(-1), respectively. The precisions and recoveries also were investigated by spiking 3-level concentrations in edible oil. The recoveries obtained were over 89.9% with relative standard deviation (RSD) of 9.6%. The new approach was utilized to successfully detect trace amounts of organoarsenic compounds in various edible oil samples.

Determination of chlorophenols in landfill leachate using headspace sampling with ionic liquid-coated solid-phase microextraction fibers combined with gas chromatography–mass spectrometry

A new microextraction technique based on ionic liquid solid-phase microextraction (IL-SPME) was developed for determination of trace chlorophenols (CPs) in landfill leachate. The synthesized ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([C(4)MIM][PF(6)]), was coated onto the spent fiber of SPME for extraction of trace CPs. After extraction, the absorbed analytes were desorbed and quantified using gas chromatography-mass spectrometry (GC/MS). The term of the proposed method is as ionic liquid-coated of solid-phase microextraction combined with gas chromatography-mass spectrometry (IL-SPME-GC/MS). No carryover effect was found, and every laboratory-made ionic liquids-coated-fiber could be used for extraction at least eighty times without degradation of efficiency. The chlorophenols studied were 2,4-dichlorophenol (2,4-DP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP), and pentachlorophenol (PCP). The best results of chlorophenols analysis were obtained with landfill leachate at pH 2, headspace extraction for 4 min, and thermal desorption with the gas chromatograph injector at 240°C for 4 min. Linearity was observed from 0.1 to 1000 μg L(-1) with relative standard deviations (RSD) less than 7% and recoveries were over 87%. The limit of detection (LOD) for pentachlorophenol was 0.008 μg L(-1). The proposed method was tested by analyzing landfill leachate from a sewage farm. The concentrations of chlorophenols were detected to range from 1.1 to 1.4 μg L(-1). The results demonstrate that the IL-SPME-GC/MS method is highly effective in analyzing trace chlorophenols in landfill leachate.

Determination of perfluorocarboxylic acids in water by ion-pair dispersive liquid–liquid microextraction and gas chromatography–tandem mass spectrometry with injection port derivatization

A novel technique for derivatization in a gas chromatograph injection port after a one-step extraction of trace perfluorocarboxylic acids (PFCAs) in water with ion pair formation during dispersive liquid-liquid microextraction (DLLME) was investigated. Tetrabutylammonium hydrogen sulfate (TBAHS) was used as the ion pair reagent. PFCA butyl ester derivatives were formed in the GC injection port and then analyzed using gas chromatography coupled to tandem mass spectrometry with negative chemical ionization. According to our analysis, the operative linear range for PFCA detection from 250 pg mL(-1) to 2 μg mL(-1) with a relative standard derivation (RSD) below 13%. Detection limits were achieved at the level of 37-51 pg mL(-1). This method was successfully applied for the analyzing of PFCAs in river water samples from urban and industrial areas without tedious pretreatment. The concentration range over which PFCAs were detected is from 0.6 ng mL(-1) to 604.9 ng mL(-1).

Ultrasound/microwave-assisted solid–liquid–solid dispersive extraction with high-performance liquid chromatography coupled to tandem mass spectrometry for the determination of neonicotinoid insecticides in Dendrobium officinale

A one-step ultrasound/microwave-assisted solid-liquid-solid dispersive extraction procedure was used for the simultaneous determination of eight neonicotinoids (dinotefuran, nitenpyram, thiamethoxam, clothianidin, imidacloprid, acetamiprid, thiacloprid, imidaclothiz) in dried Dendrobium officinale by liquid chromatography combined with electrospray ionization triple quadrupole tandem mass spectrometry in multiple reaction monitoring mode. The samples were quickly extracted by acetonitrile and cleaned up by the mixed dispersing sorbents including primary secondary amine, C18 , and carbon-GCB. Parameters that could influence the ultrasound/microwave-assisted extraction efficiency such as microwave irradiation power, ultrasound irradiation power, temperature, and solvent were investigated. Recovery studies were performing well (70.4-113.7%) at three examined spiking levels (10, 50, and 100 μg/kg). Meanwhile, the limits of quantification for the neonicotinoids ranged from 0.87 to 1.92 μg/kg. The method showed good linearity in the concentration range of 1-100 μg/L with correlation coefficients >0.99. This quick and useful analytical method could provide a basis for monitoring neonicotinoid insecticide residues in herbs.

Identification of new minor metabolites of penicillin G in human serum by multiple-stage tandem mass spectrometry.

Liquid chromatography/mass spectrometry (LC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) were applied to characterize drug metabolites. Although these two methods have overcome the identification and structural characterization of metabolites analysis, they remain time-consuming processes. In this study, a novel multiple-stage tandem mass spectrometric method (MS(n) ) was evaluated for identification and characterization of new minor metabolism profiling of penicillin G, one of the β-lactam antibiotics, in human serum. Seven minor metabolites including five phase I metabolites and two phase II metabolites of penicillin G were identified by using data-dependent LC/MS(n) screening in one chromatographic run. The accuracy masses of seven identified metabolites of penicillin G were also confirmed by mass spectral calibration software (MassWorks™). The proposed data-dependent LC/MS(n) method is a powerful tool to provide large amounts of the necessary structural information to characterize minor metabolite in metabolism profiling.

Microwave-assisted deep eutectic solvent extraction coupled with headspace solid-phase microextraction followed by GC-MS for the analysis of volatile compounds from tobacco

A novel method of microwave-assisted deep eutectic solvent extraction coupled with solid-phase microextraction was developed to determine the volatile compounds in tobacco by gas chromatography-mass spectrometry. During the process, the deep eutectic solvent played the roles of absorbing medium for microwave radiation, destroyer of cell walls, and solvent for dissolving the compounds released from the cells. Combined with solid-phase microextraction, the volatile components were extracted and concentrated in one step. In this method, several experimental parameters, such as fibre type, deep eutectic solvent type, microwave power, set-up temperature and irradiation time were studied. Compared with microwave-assisted water extraction coupled with solid-phase microextraction, and conventional solid-phase microextraction, more volatile components were obtained with higher responses. It was demonstrated that this method has improved extraction efficiency. Moreover, the proposed method has been applied to analyzing tobacco volatiles from different regions and nine different types of components have been detected. The results indicate that microwave-assisted deep eutectic solvent extraction coupled with solid-phase microextraction is an efficient, environmentally-friendly and fast miniaturization pretreatment technology for the extraction of volatiles from tobacco samples. This is a potentially promising technique for other complex and valuable matrices with low volatile content.

A new liquid–liquid microextraction method by ultrasound assisted salting-out for determination of triazole pesticides in water samples coupled by gas chromatography-mass spectrometry

A simple, fast and environmentally friendly method termed “ultrasound assisted salting-out homogeneous liquid–liquid microextraction (UASO-HLLME)” has been developed and validated for the quantitative determination of triazole pesticides in water samples coupled with gas chromatography-mass spectrometry (GC-MS). In this work, the water-miscible solvent, acetonitrile was used as an extractant instead of a highly toxic extractant used in traditional dispersive liquid–liquid microextraction (DLLME) to form a homogeneous water solution, followed by salting-out a small amount of acetonitrile for the purpose of extraction and enrichment. Various parameters affecting the extraction process, including the kind and volume of extractant, ultrasound assisted promoting solvent collection and solvent blending, were optimized. Under optimum conditions matrix matched calibration curves were established using a standard solution spiked water sample. Good linear relationships as well as low limits of detection, LODs (0.4–14.4 μg L−1) and quantification, LOQs (1.3–48.1 μg L−1), were obtained. The relative standard deviation percentages (RSD%) of the spiked water sample and real environmental water sample were 4.5–8.1% and 0.4–8.1%, respectively, with an enrichment factor (EF) of 120–185. Recoveries obtained from spiked environmental water samples at three concentration levels ranged from 89.6 to 119%. The results of the analysis revealed that this method is simple, fast and environmentally friendly, being successfully applicable for the determination of triazole pesticides in water samples.

Ionic liquid-based carbon nanotube coated magnetic nanoparticles as adsorbent for the magnetic solid phase extraction of triazole fungicides from environmental water

Ionic liquid-based magnetic carbon nanotubes (IL-Fe3O4@MWCNTs) were synthesized as a novel adsorbent for magnetic solid-phase extraction (MSPE) for the determination of six triazole fungicides, i.e. penconazole (Pen), tebuconazole (TEB), epoxiconazole (Epo), bitertanol (Bit), fenbuconazole (Fen) and difenoconazole (Dif), from aqueous solution by gas chromatography coupled to mass spectrometry. Scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD) and Energy Dispersive X-ray (EDX) spectrometry were used to characterize the adsorbent. Some important factors governing the extraction efficiency such as adsorbent type, dilution conditions, adsorbent amount, extraction time, desorption time and ionic strength were investigated and optimized. Under the optimal conditions, the enrichment factors of the method for the analytes were in the range of 125 to 1242. A good linearity was observed in the range of 0.5–50 ng mL−1 for Epo, Bit, Fen, and Dif, 1–50 ng mL−1 for Teb and 2–50 ng mL−1 for Pen, respectively, with the correlation coefficients ranging from 0.9968 to 0.9999. The limits of detection (LODs) and the limits of quantification (LOQs) of the method were within the range 0.05–0.22 ng mL−1 and 0.23–0.75 ng mL−1, respectively. The southern end of the Beijing-Hangzhou Grand Canal water (Hangzhou, China) was used to verify the applicability of the developed method for the determination of the targets.

Tablet-effervescence-assisted dissolved carbon flotation for the extraction of four triazole fungicides in water by gas chromatography with mass spectrometry

A pretreatment method named tablet-effervescence-assisted dissolved carbon flotation was introduced for the determination of four triazole fungicides in environmental water. In this method, the use of effervescent tablet composed of nontoxic sodium carbonate and sodium dihydrogen phosphate could generate CO2 in situ to assist the dispersion of extraction solvent and to accelerate mass transfer of target analytes. In addition, the simple phase separation simply based on the rising of low-density organic solvent from the aqueous phase was applied rather than the application of apparatus, which demonstrated the potential for on-site extraction in the field. The experimental variables, including the composition of effervescent tablets, amount of effervescent tablets, types and volume of extraction solvent, were investigated. Under the optimized conditions, the method showed good linearity for myclobutanil, tebuconazole, epoxiconazole, and difenoconazole in the range of 1-100 μg/L. The limits of detection and the limits of quantification were within the range of 0.15-0.26 and 0.49-0.86 μg/L, respectively. The obtained correlation coefficients varied from 0.997 to 0.999, and suitable enrichment factors were 422-589. The recoveries were 82.5-112.9% with relative standard deviations of 4.7-13.5%.

The development of ultrasound-assisted extraction/dispersive liquid–liquid microextraction coupled with DSI-GC-IT/MS for analysis of essential oil from fresh flowers of Edgeworthia chrysantha Lindl.

In this study, a simple and novel method was successfully developed for extraction and preconcentration of essential oil from fresh flowers of Edgeworthia chrysantha Lindl. by using ultrasound-assisted extraction/dispersive liquid–liquid microextraction (UAE-DLLME) coupled with gas chromatography-ion trap/mass spectrometry (GC-IT/MS) using a direct sample introduction (DSI) device. The optimum parameters of UAE-DLLME were investigated. The optimum conditions of an extraction solvent of toluene, a dispersive solvent of acetone, and an ultrasound time of 10 min were obtained and applied to the extraction of essential oil compounds from fresh flowers of Edgeworthia chrysantha Lindl. The main volatile and semi-volatile compounds from Edgeworthia chrysantha Lindl. at different florescences ((A) flower buds; (B) the initial flowering stage; (C) the full flowering stage; (D) the final flowering stage) were studied. The results showed that 36 substances were identified, including alkanes, alkenes, aromatic hydrocarbons, alcohols, aldehydes, ketones, acids, lipids, and compounds containing nitrogen (N), all of which contributing a lot to the fragrance of Edgeworthia chrysantha Lindl. In this study, a simple, rapid, and environmentally friendly approach was developed for analysis of essential oil compounds from fresh flowers of Edgeworthia chrysantha Lindl. at different florescences.