Length-controlled hydrophobic CF3-COF as a highly efficient absorbent coating for dual-mode solid-phase microextraction of sixteen polycyclic aromatic hydrocarbons in water samples.

Polycyclic aromatic hydrocarbons (PAHs), a group of seriously hazardous environmental contaminants, have attracted extensive attention due to their carcinogenicity, genotoxicity, mutagenicity, and ubiquity. In this work, the excellent hydrophobic trifluoromethyl-enriched covalent organic framework (CF3-COF) was designed and synthesized as coating of solid-phase microextraction (SPME). The CF3-COF offered a high adsorption selectivity for PAHs, which could be attributed to the multiple interactions between the CF3-COF and PAHs, including hydrophobicity interaction, π-π and H bond interactions. Furthermore, headspace (HS) and direct immersion (DI) dual-mode solid-phase microextraction (HS/DI-SPME) were innovatively integrated as a dual-mode extraction by varying the length of SPME coating on stainless-steel, which could simultaneously and efficiently extract 16 PAHs with different volatile. Amazingly, the proposed strategy achieved fast adsorption for PAHs and shortened the adsorption equilibrium time to 15 min. By further integrating with gas chromatography tandem mass spectrometry (GC-MS/MS), PAHs could be detected in the range of 0.008-0.16 ng mL-1 with a quantitative limit of 0.029-0.47 ng mL-1, respectively. The recoveries of PAHs in water samples ranged from 80.84 to 117.67 %. This work indicates that the dual-mode CF3-COF-SPME is a promising candidate for the enrichment of multiple hazardous substances in complicated samples.

[Determination of fluorescent whitening agents in plastic food contact materials by high performance liquid chromatography with fluorescence detector].

A method for the determination of fluorescent whitening agents in plastic food contact materials by high performance liquid chromatography (HPLC) with fluorescence detector was developed. The samples were extracted with trichloromethane by sonication for 30 min at 40 degrees C. The HPLC method was performed on a column of Eclipse XDB-C18 (250 mm x 4.6 mm, 5 microm) by gradient elution using 5 mmol/L ammonium acetate and acetonitrile as the mobile phases, and detected by the fluorescence detector at an excitation wavelength of 350 nm and an emission wavelength of 430 nm. The experimental results indicated that the four fluorescent whitening agents were separated well. The limits of detection (LOD) (S/N = 3) were 0.3, 0.1, 0.05, 0.14 mg/L, and the limits of quantification (LOQ) (S/N = 10) were 1.0, 0.4, 0.2, 0.5 mg/L for 1,4-bis (4-cyanostyryl) benzene (C. I. 199), 1,4-bis (2-benzoxazolyl) naphthalene (C. I. 367), 4,4'-bis(2-methoxystyryl) biphenyl (C. I. 378) and 2,5-thiophenediylbis (5-tert-butyl-1,3-benzoxazole) (C. I. 184), respectively. Good linearities with correlation coefficients (r2) not less than 0.991 were obtained. The proposed method is simple, accurate, sensitive and can meet the requirements of the routine determination of fluorescent whitening agents in entry-exit products.

Simultaneous determination of multiresidual phenyl acetanilide pesticides in different food commodities by solid-phase cleanup and gas chromatography-mass spectrometry.

An efficient and sensitive multiresidue method has been developed for quantification and confirmation of 25 phenyl acetanilide pesticides in a wide variety of food commodities including maize, spinach, mushroom, apple, soybean, chestnut, tea, beef, cattle liver, chicken, fish, and milk. Analytes were extracted with acetone-n-hexane (1:2, v/v) followed by cleanup using SPE. Several types of adsorbents were evaluated. Neutral aluminum and graphitized carbon black cartridge showed good cleanup efficiency. The extract was determined by GC-MS in the selected ion monitoring mode using one target and two qualitative ions for each analyte. The limits of detection were 0.01 mg/kg for all analytes. The average recoveries ranged from 66.9 to 110.6% (mean 88.8%) and RSDs were in the range 2.0-19% (mean 10.5%) across three fortification levels. The proposed method was successfully applied to real samples in routine analysis and a satisfactory result was obtained.

[Rapid screening and confirmation of hormones in health foods by high performance liquid chromatography-ion trap-time of flight tandem mass spectrometry].

A method was developed for the screening, confirmation and quantification of 21 hormones including progesterones, etrogens, glucocorticoids and resorcylic acid lactones in health foods by high performance liquid chromatography-ion trap-time of flight tandem mass spectrometry (HPLC-IT-TOF-MS). The analytes in the sample were extracted with acetonitrile containing 1.0% (v/v) acetic acid and the extract was purified with the mixed QuEChERS sorbents. In the chromatographic analysis, the 21 target compounds were separated on a C18 column with the gradient elution using the mobile phases of acetonitrile and water containing 0.1% acetic acid. The mass analyzer was performed in positive and negative full scan modes in one injection at the same time. The results showed that the linear ranges of the 21 hormones were 5.0-250 microg/L with the correlation coefficients above 0.993 and the limits of quantification (LOQ, S/N > or = 10) were 2.0-5.0 microg/kg and 1.0-2.5 microg/L for capsule and oral solution, respectively. The method validation was carried out at three spiked levels, and the recoveries were 60.2%-116.0% with the relative standard deviations (RSDs) of 7.0%-18.3%. The screening of analytes was performed by precision mass matching and library searching. The secondary fragment ion spectra were employed to the confirmation. This method is simple, fast, reliable, and can be applied to the simultaneous screening and determination of hormones in health foods.

[Determination of ten aminoglycoside residues in milk and dairy products using high performance liquid chromatography-tandem mass spectrometry].

A high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/ MS) analytical method was developed for the simultaneous determination of ten aminoglycoside residues (streptomycin, dihydrostrepmycin, neomycin, kanamycin, tobramycin, gentamycin, apramycin, hygromycin B, paromomycin, and amkacin) in milk and dairy products. The sample was extracted with 5% trichloroacetic acid aqueous solution, then the extract was purified by a hydrophilic-lipophilic balance (HLB) cartridge. The ten aminoglycoside residues were separated by ion-pair reversed phase high performance liquid chromatography. Heptafluorobutyric acid was used as ion pair agent due to its volatility. Then the analytes were detected by electrospray ionization tandem mass spectrometry. The pretreatment condition of the sample, the HPLC condition and the MS operation parameters were optimized. The results showed that the linearities of the ten aminoglycoside residues in 20-1000 microg/L had the correlation coefficient between 0.9946-0.9997. The recoveries ranged from 71.2% and 101.7% with the relative standard deviations of 3.4%-13.8%. The proposed method was successfully applied to the determination of the mass concentrations of the analytes in related samples, which provides a simple, and convenient method for the quality control of milk and dairy products. Furthermore, this method is effective for the safety monitoring of aminoglycoside residues in milk and dairy products.

[Magnetic multi-walled carbon nanotubes as a solid phase extraction adsorbent for the determination of 13 phthalate acid esters in water samples by gas chromatography-mass spectrometry].

A method based on solid phase extraction (SPE) with magnetic multi-walled carbon nanotubes (MWCNTs) as adsorbent was developed for the determination of 13 phthalate acid esters (PAEs) in water samples by gas chromatography-mass spectrometry (GC-MS). The factors affecting the extraction efficiency, such as extraction time, pH of water sample, desorption solvent, and desorption time, were carefully investigated. The optimized conditions were as follows: extraction time, 10 min; pH of water samples, 5 - 7; desorption solvent, 2 mL acetone; desorption time, 5 min. The extraction efficiencies were 89.7% - 100.5% under the optimized conditions. The method was sensitive with the detection limits (S/N = 3) between 0.08 -0.47 microg/L for the 13 PAEs. The developed method was successfully applied for the analysis of tap water, bottle drinking water and lake water, and none of the 13 PAEs was detected. The recoveries ranged from 84.5% to 107.5% for the 3 real spiked samples, and the relative standard deviations were between 1.9% and 12.8%. The developed method has proved convenient, time-saving, accurate, sensitive, and environmental-friendly, and can be used for the determination of PAEs in water samples.