Yiqun Wan

Simultaneous determination of organophosphorus, organochlorine, pyrethriod and carbamate pesticides in Radix astragali by microwave-assisted extraction/dispersive-solid phase extraction coupled with GC–MS

A simple, rapid and reliable method was proposed for the simultaneous determination of 27 pesticides (organophosphorus, organochlorine, pyrethroid and carbamate pesticides) in Radix astragali. The pesticides were extracted by acetonitrile and the experimental variables, such as temperature, extraction time and volume of acetonitrile, were optimized through orthogonal array experimental design. Cleanup of extracts was performed with dispersive-solid phase extraction using primary secondary amine (PSA) as the sorbent. The determination of pesticides in the final extracts was carried out by gas chromatography-mass spectrometry in selected ion monitoring mode (GC-MS, SIM). The linearity of the calibration curves is good in matrix-matched standard, and yields the coefficients of determination (R(2))≥0.99 for approximately 96% of the target analytes. Under optimized conditions, the average recoveries (six replicates) for most pesticides (spiked at 0.02, 0.1 and 0.2 mg kg(-1)) range from 70% to 120%, and RSDs are less than 17.2%.

Utilization of deep eutectic solvents as novel mobile phase additives for improving the separation of bioactive quaternary alkaloids

Deep eutectic solvents (DESs) were used as novel mobile phase additives to improve chromatographic separation of four quaternary alkaloids including coptisine chloride, sanguinarine, berberine chloride and chelerythrine on a C18 column. DESs as a new class of ionic liquids are renewably sourced, environmentally benign, low cost and easy to prepare. Seven DESs were obtained by mixing different hydrogen acceptors and hydrogen-bond donors. The effects of organic solvents, the concentration of DESs, the types of DESs and the pH values of the buffer solution on the separation of the analytes were investigated. The composition of acetonitrile and 1.0% deep eutectic solvents aqueous solution (pH 3.3, adjusted with hydrochloric acid) in a 32:68 (v/v) ratio was used as optimized mobile phase, with which four quaternary alkaloids were well separated. When a small amount of DESs was added in the mobile phase for the separation of alkaloids on the C18 column, noticeable improvements were distinctly observed such as decreasing peak tailing and improving resolution. The separation mechanism mediated by DESs as mobile phase additives can be attributed to combined effect of both hydrogen acceptors and hydrogen-bond donors. For example, choline chloride can effectively cover the residual silanols on silica surface and ethylene glycol can reduce the retention time of analytes. The proposed method has been applied to determine BerbC in Lanqin Chinese herbal oral solution and BerbC tablet. Utilization of DESs in mobile phase can efficiently improve separation and selectivity of analytes from complex samples.

Sulfonated polystyrene magnetic nanobeads coupled with immunochromatographic strip for clenbuterol determination in pork muscle.

A magnetic solid-phase extraction method (MSPE) was developed to pre-concentrate and cleanup clenbuterol (CLE) from pork muscle. Novel sulfonated polystyrene magnetic nanobeads (spMNBs) were synthesized via a one-pot emulsion copolymerization method by using divinylbenzene, styrene, and sodium styrene sulfonate in the presence of oleic acid-modified and 10-undecylenic acid-modified magnetic ferrofluid. The resulting spMNBs exhibited high adsorption efficiency for CLE and for 10 other common beta-adrenergic agonists, namely, brombuterol, ractopamine, tulobuterol, bambuterol, cimbuterol, mabuterol, clorprenaline, penbutolol, salbutamol, and cimaterol. The adsorption behavior of the spMNBs for CLE was described by the Langmuir equation with a maximum adsorption capacity of 0.41 mg/g. Under the optimized parameters, the extraction of CLE from 0.5 g of pork muscle required 25mg of the spMNBs at a shortened adsorption time (0.5 min). The proposed MSPE was coupled with colloidal gold nanoparticle-based immunochromatographic assay (MSPE-AuNPIA) for the quantitative detection of CLE residue in pork muscle. The limit of detection and limit of quantification for the pork muscle were 0.10 and 0.24 ng/g, respectively. The intra-day and inter-day assay recoveries at three CLE spiked concentrations ranged from 92.5% to 98.1%, with relative standard deviations ranging from 3.2% to 13.0%. The results of MSPE-AuNPIA were confirmed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The CLE values obtained with MSPE-AuNPIA agreed with those obtained with LC-MS/MS.

Ultrasensitive turn-on fluorescent detection of trace thiocyanate based on fluorescence resonance energy transfer.

Thiocyanate (SCN(-)) is a small anion byproduct of cyanide metabolism. Several methods have been reported to measure SCN(-) above the micromolar level. However, SCN(-) is derived from many sources such as cigarettes, waste water, food and even car exhaust and its effect is cumulative, which makes it necessary to develop methods for the detection of trace SCN(-). In this paper, a simple and ultrasensitive turn-on fluorescence assay of trace SCN(-) is established based on the fluorescence resonance energy transfer (FRET) between gold nanoparticles (AuNPs) and fluorescein. The detection limit is 0.09 nM, to the best of our knowledge, which has been the lowest detection LOD ever without the aid of costly instrumentation. The fluorescence of fluorescein is significantly quenched when it is attached to the surface of AuNPs. Upon the addition of SCN(-), the fluorescence is turned on due to the competition action between SCN(-) and fluorescein towards the surface of AuNPs. Under an optimum pH, AuNPs size and concentration, incubation time, the fluorescence enhancement efficiency [(IF-I0)/I0] displays a linear relationship with the concentration of SCN(-) in the range of 1.0 nM to 40.0 nM. The fluorescein-AuNP sensor shows absolutely high selectivity toward SCN(-) than other 16 anions. The common metal ions, amino acids and sugars have no obvious interference effects. The accuracy and precision were evaluated based on the recovery experiments. The cost effective sensing system is successfully applied for the determination of SCN(-) in milk products and saliva samples.

Deep eutectic solvent-based liquid-phase microextraction for detection of plant growth regulators in edible vegetable oils

In this study, a series of tunable DESs were prepared and used for the liquid-phase microextraction of plant growth regulators, including indole-3-acetic acid, indole-3-butyric acid and 4-iodophenoxyacetic acid, from a multi-component edible vegetable oil matrix. Of the several types of DESs composed of different hydrogen acceptors and hydrogen bond donors, the DESs formed by tetramethylammonium chloride–ethylene glycol (in a 1 : 3 molar ratio) showed the best extraction efficiency, and 30 μL of the DESs yielded the highest efficiency of all volumes tested in the range of 10–50 μL. Extraction equilibrium was reached in only 7 min of ultrasonication under 50 °C. Under the optimum conditions, a good linearity was obtained for 3.0–50 μg mL−1 of indole-3-acetic acid, 1.2–58 μg mL−1 of indole-3-butyric acid and 7.5–75 μg mL−1 of 4-iodophenoxyacetic acid, with the correlation coefficients no less than 0.9980. Both the limits of detection (LODs) and limits of quantification (LOQs) were satisfied and could meet the requirements of the applications in oil samples. The study demonstrated that DESs could be used as efficient liquid-phase microextraction media for analysis of plant growth regulators in edible vegetable oil samples.

Determination of plant growth regulators in pears by microwave‐assisted extraction and liquid chromatography with electrospray ionization mass spectrometry

A new method for the determination of six plant growth regulators, 3-indolylacetic acid, 3-indolepropionic acid, 2-naphthoxyacetic acid, 2,4-dicholrophenoxyacetic acid, 1-naphthlcetic acid, and methyl naphthalene-1-acetate, in pears was established by liquid chromatography with electrospray ionization mass spectrometry. In this study, a microwave-assisted extraction technique was first applied for the determination of plant growth regulators in fruit and three cleanup techniques were, respectively, investigated for the purification of pear samples. The chromatographic separation was performed on a Diamonsil C18 column by using 0.01 mol/L formic acid/ammonium formate buffer solution (pH 3.5)/methanol (35:65, v/v) as the mobile phase with a flow rate of 0.7 mL/min in 1:1 split mode. The LODs ranged from 0.3 to 1.9 μg/kg. Under optimized conditions, the average recoveries (five replicates) for six plant growth regulators (spiked at 0.01, 0.05, and 0.5 mg/kg) ranged from 78.9 to 118.0%, and the RSDs were 1.4-10.3%.

Determination of Organotins in Seafood by Novel Extraction Procedures and High Performance Liquid Chromatography–Inductively Coupled Plasma-Mass Spectrometry

Triorganotins in seafood are a risks to human health, but due to their low concentrations, their determination is challenging. In this study, a simple and rapid method was developed to isolate triorganotins from seafood by microwave-assisted extraction coupled with magnetic nanoparticle-based purification. The magnetic nanoparticles were coated with octanoic acid. Triethyltin chloride, tributyltin chloride, triphenyltin chloride, and azocyclotin were determined by high performance liquid chromatography– inductively coupled plasma mass spectrometry (HPLC–ICP-MS). Various parameters including the temperature, time, and volume of solvent were optimized to improve the extraction efficiency. Under the optimized conditions, the average recoveries (n = 6) of the triorganotins (fortified at 0.01, 0.02, and 0.05 µg g−1) were between 73.8% and 105.4% and the relative standard deviations were less than 10.4%. The procedure was successfully applied to seafood, and the analytes were measured at concentration levels between 2.93 and 11.26 ng g−1.

A simple one-step extraction method for the determination of organophosphorus pesticides in shuanghuanglian and antivirus oral liquids by gas chromatography-tandem mass spectrometry

A new multi-residue method was proposed for the determination of 11 organophosphorus pesticides (OPPs) in Traditional Chinese medicinal preparation oral liquids. The method was based on a simple one-step extraction procedure without further clean-up step. The analytes were extracted by a solvent mixture of acetone and n-hexane, and the experimental parameters such as the ratio of acetone : n-hexane (v/v), the volume of extraction solvent and the extraction time were optimized via orthogonal array experimental design (OAD). All of the pesticides were successfully identified and quantified by gas chromatography-tandem mass spectrometry (GC-MS/MS). The linearity of calibration curves is excellent for matrix-matched standards and yields the coefficients of determination (R2) > 0.9997 for the target analytes. Low limits of quantification (10 μg L−1) were achieved. Under optimized conditions, the average recoveries for most pesticides (spiked at 10, 20, and 50 μg L−1) range from 70% to 120%, and RSDs are less than 13.3%. This satisfactory method has been established for the first time for the determination of OPPs in Traditional Chinese medicinal preparation oral liquids.

Fast and effective low‐temperature freezing extraction technique to determine organotin compounds in edible vegetable oil

Most organotin compounds that have been widely used in food packaging materials and production process show serious toxicity effects to human health. In this study, a simple and low-cost method based on high-performance liquid chromatography with inductively coupled plasma mass spectrometry for the simultaneous determination of four organotins in edible vegetable oil samples was developed. Four organotins including dibutyltin dichloride, tributyltin chloride, diphenyltin dichloride, and triphenyltin chloride were simultaneously extracted with methanol using the low-temperature precipitation process. After being concentrated, the extracts were purified by matrix solid-phase dispersion using graphitized carbon black. The experimental parameters such as extraction solvent and clean-up material were optimized. To evaluate the accuracy of the new method, the recoveries were investigated. In addition, a liquid chromatography with tandem mass spectrometry method was also proposed for comparison. The procedures of extracting and purifying samples for the analysis were simple and easy to perform batch operations, also showed good efficiency with lower relative standard deviation. The limits of detection of the four organotins were 0.28-0.59 μg/L, and the limits of quantification of the four organotins were 0.93-1.8 μg/L, respectively. The proposed method was successfully applied to the simultaneous analysis of the four organotins in edible vegetable oil. Some analytes were detected at the level of 2.5-28.8 μg/kg.

Low-temperature precipitation for the determination of residual organotin compounds in plant oil using dispersive-solid phase extraction and gas chromatography-mass spectrometry

Considerable numbers of organotin compounds, which are widely used in people’s lives, have serious toxic effects to human health. In this paper, a simple, low-cost method for the simultaneous determination of four organotins in plant oil samples by gas chromatography-mass spectrometry (GC-MS) has been established for the first time. The method uses dispersive-solid phase extraction (d-SPE) clean-up after a low-temperature precipitation procedure, in situ derivatization with NaBEt4 and liquid–liquid extraction (LLE). The relevant experimental variables influencing the whole results were optimized; a good accuracy and precision were attained under the optimal conditions. The average recoveries obtained for analytes were in the range of 75.6–114.9% with a relative standard deviation (RSD) of 3.9–12.6%, and the limits of detection for each organotin ranged between 0.19 and 0.33 μg kg−1. Finally, these four organotins in different oil samples were detected using this method, which demonstrated the feasibility of our developed method in this study.