A method of gas chromatography-mass spectrometry with acetonitrile extraction and solid phase extraction column purification was proposed for the determination of 6 phthalate ester compounds[PAEs, including dibutyl phthalate (DBP), benzyl butyl phthalate (BBP), di (2-ethyl) hexyl phthalate (DEHP), di-iso-nonyl phthalate (DINP), di-n-octyl phthalate (DNOP) and di-n-decyl phthalate (DIDP)] in 4 stationery supplies (plastic book covers, book membranes, pen holders, rulers) with complex matrix, and the pretreatment conditions of the method, including extractant (ethyl acetate, dichloromethane, mixed solution of n-hexane and dichloromethane at volume ratio of 1:1, n-hexane, acetone, tetrahydrofuran, toluene, acetonitrile), extraction temperature (0, 20, 30, 40℃), and extraction time (10, 20, 30, 40 min) were optimized. The sample was cut into small pieces with the size of 10 cm×10 cm. An aliquot (0.2 g) was taken and immersed into 5 mL of acetonitrile, and the mixture was shaken for 20 min, and extracted by ultrasound at 40℃ for 30 min. Then 1 mL of the extract was taken and passed through the solid phase extraction column (Si/PSA SPE glass column) activated beforehand. The above column was eluted by 10 mL of acetonitrile, and the eluate was collected, and blown to near dryness by nitrogen. The residue was dissolved by n-hexane, and made its volume up to 1 mL. The resulting solution was analyzed by gas chromatography-mass spectrometry, with external standard method for quantification. When purifying the extract of the other 7 solvents, 5 mL of n-hexane was used for rinsing, and 10 mL of mixed solution composed of n-hexane and ethyl acetate at volume ratio of 2:8. was used for elution. The other steps were the same as those of acetonitrile. The extraction effect of each solvent was evaluated using determined values of PAEs in actual samples and spiked recoveries. It was shown that acetonitrile had stronger adaptability to stationery supplies made of different materials. When ultrasonic extraction was made at 40℃ for 30 min, more PAEs were obtained, and their determined values and recoveries were higher (greater than 70.0%). Linear relationships between values of the mass concentration of the 7 PAEs and the peak area were kept in the ranges of 0.2-10.0 mg·L^-1 (DBP, BBP, DEHP and DNOP) and 2.0-100.0 mg·L^-1 (DINP and DIDP), with detection limits (3S/N) in the range of 0.003-0.05 mg·kg^-1. The spiked recoveries were found in the range of 74.1%-107%, with RSDs (n=6) of the determined values in the range of 1.2%-5.1%. The proposed method was used for the analysis of 12 actual samples, and DNOP, DINP and DIDP were not detected. The total detection amount of DBP, BBP and DEHP did not exceed the limit specified in GB 21027-2020.

Considering that the carrier gas of the commercially available hydride generation atomic fluorescence spectrometer was loaded into the inner tube of the quartz atomizer with a small flow (300-600 mL·min^-1 for the determination of lead and cadmium), resulting in smaller lead and cadmium fluorescence intensities, the flow paths of the carrier gas and auxiliary gas in the quartz atomizer of this instrument had been modified, and the inner tube injection had been changed to the outer tube injection. Meanwhile, the additives and carrier current had been optimized, and methodological validation had been conducted. After being treated with acid solution, the sample was analyzed using the modified hydride generation atomic fluorescence spectrometer. It was shown that compared to the inner tube injection, the outer tube injection could increase the carrier gas flow to 1 000-1 400 mL·min^-1, carrying more hydrogenated gas. The mixture of hydrogenated gas and hydrogen gas could come into contact with the heating furnace wire at the upper end of the quartz sleeve faster and beignited. The auxiliary gas (argon) input from the inner tube would moderately lift the hydrogen flame upwards, resulting in more stable and larger volume of the flame. Using potassium ferricyanide and cadmium sensitizer as additives, the fluorescence intensities of lead and cadmium could significantly be enhanced. Replacing traditional dilute acids with water as carrier current, RSDs (n=7) of fluorescence intensities of lead and cadmium in the reagent blank during alternating injection were less than 3.0%, suitable for small batch sample detection. Linear ranges of lead and cadmium standard curves were within 10.00 μg·L^-1 and 0.50 μg·L^-1, with detection limits (3s/k) of 3.5 μg·kg^-1 (lead in puffed food) and 0.74 μg·kg^-1 (cadmium in rice). The sensitivity (standard curve slope k) of lead, cadmium was 1.3-13 and 2.8-99 times those of similar methods reported in literatures, respectively. Test for recovery was made according to the standard addition method, giving recoveries in the range of 86.0%-118%, and RSDs (n=6) of the determined values were found in the range of 2.6%-5.8%.

Isoniazid (INH) drug tablets were ground, and the drug powder containing 2.00 mg of INH was taken. After adding 20 mL of water, the mixture was stirred for 2 min with glass rod. The obtained solution was diluted to 100.0 mL by water. An aliquot (5.00 mL) was taken, and centrifuged for 2 min, and 1.00 mL of the supernatant was taken, and diluted to 10.0 mL by water to prepare the INH sample solution. Then 1.00 mL of 0.20 mol·L^-1 acetic acid-sodium acetate buffer solution (pH 4.6), 1.50 mL of 0.50 g·L^-1 NaB(C₆H₅)₄ solution, and 2.00 mL of 1.00 g·L^-1 CuSO₄ solution were added and mixed, and 1.00 mL of INH sample solution was added. The mixture was diluted to 10.0 mL by water, shaken for 0.5 min, and settled to react for 10 min. INH reduced Cu(Ⅱ) to Cu(Ⅰ), and Cu(Ⅰ) reacted with B(C₆H₅)₄^- to form CuB(C₆H₅)₄ complex, which further aggregated to form associated particles, forming a solid-liquid interface with strong resonance light scattering signal. An appropriate amount of the above solution was taken and placed into a fluorescence spectrophotometer, and synchronously scan was made on excitation (λ_ex) and emission (λ_em) wavelengths in the range of 200-700 nm (λ_ex=λ_em), reading the signal intensity I_RSS of the resonance scattering peak at 397 nm. The reagent blank was analyzed simultaneously to obtain I⁰_RSS, with ΔI_RSS (ΔI_RSS=I_RSS-I⁰_RSS) for quantification. It was shown that 100 times starch, 120 times glucose, 150 times maltose, 200 times sucrose, 600 times NO₃^-, 800 times Cl^-, 1 000 times K⁺, and 800 times Zn²⁺ did not interfere with the determination of INH. Linear relationship between values of the mass concentration of INH and ΔI_RSS of the reaction system was kept in the range of 0.010-2.00 mg·L^-1, with detection limit (3s/k) of 0.004 mg·L^-1. The proposed method was used for the analysis of actual samples, and RSDs (n=5) of the INH determined values were found in the range of 1.8%-2.6%. The determined values were basically consistent with those obtained from the high performance liquid chromatography in the Pharmacopoeia of the People's Republic of China (2020 version). Test for recovery was conducted according to the standard addition method, giving recoveries in the range of 97.0%-99.0%.

Based on the information entropy theory, the recovery comprehensive score M of the 4 nitrofuran metabolites, including 5-morpholinomethyl-3-amino-2-oxazolidinone (AMOZ), 3-amino-2-oxazolidinone (AOZ), 1-aminohydantoin hydrochloride (AHD) and semicarbazide hydrochloride (SEM), was used as the evaluation index to optimize the derivatization conditions for the detection of nitrofuran metabolites residues in freshwater fish by single factor and response surface tests. The freshwater fish sample was hydrolyzed by hydrochloric acid solution, and internal standards solution was added. Then, 350 μL of 0.05 mol·L^-1 ortho nitrobenzaldehyde (derivatization reagent) solution with methanol as the medium was added, and derivatization reaction was made by oscillation at 46℃ under the light proof condition for 2.5 h. The acidity of the solution obtained was adjust to pH 7.4 ± 0.2, and extraction was made twice by ethyl acetate. The extract was collected, and blown to dryness by nitrogen. n-Hexane was added for impurity removal, and 50% (volume fraction) acetonitrile solution was added for redissolving the residue. After centrifugation, the lower phase was taken for filtration, and the filtrate was analyzed by ultra-high performance liquid chromatography-tandem mass spectrometry. In chromatographic analysis, Agilent Zorbax RRHD Eclipse Plus C₁₈ chromatographic column (100 mm×2.1 mm, 1.8 μm) was used for separation, and the mixed solution composed of 0.1% (volume fraction) formic acid solution and acetonitrile at volume ratio of 1:1 was used for isocratic elution. In mass spectrometry analysis, atmospheric pressure spray ion source was used for ionization, and multiple reaction monitoring (MRM) mode was used for detection. In quantitative analysis, matrix matching and internal standard methods were used to reduce matrix interference and improve the sensitivity of the method. It was shown that factors of derivatization reagent volume, derivatization temperature, and derivatization time, as well as the interaction factor of derivatization reagent volume and derivatization temperature, had a significant effect on the recovery comprehensive score M (P<0.01). Under the optimal derivatization conditions, the test value of the quadratic polynomial model (M_test=1.020 4) and the prediction value (M_prediction=0.999 2) were basically consistent. The linear ranges of the working curves for the 4 nitrofuran metabolites were found in the same range of 0.02-50.00 μg·L^-1, with detection limits (3S/N) in the range of 0.02-0.19 μg·kg^-1. Test for recovery was made according to the standard addition method, giving recoveries in the range of 85.1%-116%, and RSDs (n=5) of the determined values ranged from 0.64% to 9.8%. The proposed method was used for the analysis of 55 batches of actual samples, and the detection rates of AOZ, AMOZ, and SEM were 1.82%, 1.82%, and 3.64%, respectively. The highest detection amounts of AOZ and AMOZ were 0.24, 0.13 μg·kg^-1, and the detection amount of SEM was below the lower limit of determination.

A rapid and non-destructive method for the determination of total flavonoids in Pteridium aquilinum was proposed by near infrared spectroscopy combined with partial least square method. The 140 samples of Pteridium aquilinum were taken, and their near infrared spectra were collected in the waveband of 4 000-11 500 cm^-1 by Fourier transform near infrared spectrometer. The original spectra obtained were pretreated by the first-order derivative, and the model was established in the waveband of 6 100-7 500 cm^-1 and 5 400-6 000 cm^-1 with principal factor number of 10. It was shown that RMSEC of the quantitative analysis model established with calibration set was 0.078, and R² was 0.991 9. RMSEP of the quantitative analysis model established with varification set was 0.125, and R² was 0.984 1, indicating that the performance of the established model was superior. The completely external validation set samples were analyzed by the quantitative analysis model and UV-Vis spectrophotometry, giving predicted recoveries (percentage ratios of predicted values to determined values) closed to 100%, indicating that the established model had high prediction accuracy, and could be used for the rapid and accurate determination of total flavonoids in Pteridium aquilinum.

Considering the low recovery of nitenpyram using existing methods and lack of methods for simultaneously detecting neonicotinoid pesticides and their metabolites in soil, this study was conducted mentioned by the title. Soil samples were collected within 20 cm of the soil surface, dried by air, removed from impurities and sieved. An aliquot (5 g) was taken, and mixed with 3.0 mL of water. The mixture was shaken, settled for 10 min, and mixed with 10 mL of acetonitrile solution containing 1.0% (volume fraction) acetic acid. After shaking for 30 min, 5.0 g of anhydrous magnesium sulfate and 1.0 g of sodium chloride were added, and the mixture was shaken vigorously for 1 min, and centrifuged at 4℃ for 5 min. Then 0.15 g of anhydrous magnesium sulfate and 0.05 g of PSA were placed into a 5 mL-centrifuge tube with a stopper, and 2.0 mL of the above sample extract was added. The mixed solution was shaken for 1 min by vortex, and centrifuged at 4℃ for 3 min. An aliquot (0.5 mL) of the supernatant was taken, and mixed with 0.5 mL of water. After mixing well, the resulting solution was passed through a 0.2 μm filter membrane. The filtrate was collected and detected by the ultra-high performance liquid chromatograph-tandem mass spectrometer. Fourteen targets (including 10 neonicotinoid pesticides and 4 metabolites) were separated on the Waters ACQUITY UPLC HSS T3 chromatographic column by gradient elution with mixed solutions composed of methanol solution containing 5 mmol·L^-1 ammonium formate and 0.1% (volume fraction) formic acid solution containing 5 mmol·L^-1 ammonium formate at different volume ratios, ionized by the ESI⁺ mode, detected by the MRM mode, and quantified by matrix matching method. It was shown that linear relationships between values of the mass concentration and the corresponding peak area of 14 targets were kept in the ranges of 2.0-200.0 μg·L^-1 (clothianidin) and 0.5-200.0 μg·L^-1 (other 13 targets), with detection limits (3S/N) in the range of 0.36-2.49 μg·kg^-1. Test for recovery was made according to the standard addition method, giving recoveries in the range of 75.4%-112%, and RSDs (n=6) of the determined values were less than 9.0%. The proposed method was applied to the analysis of 16 orchard soil samples, and imidacloprid (13 samples), thiamethoxam (8 samples), and clothianidin (1 sample) were detected, with detection amounts of 0.007-0.31 mg·kg^-1, 0.005-0.28 mg·kg^-1 and 0.009 mg·kg^-1, respectively.

To reduce the loss caused by the pretreatment process in the determination of six 2-3 ring polycyclic aromatic hydrocarbons (naphthalene, acenaphthene, acenaphthene, fluorene, phenanthrene, and anthracene) and their substitute, decafluorobiphenyl, in soil sample by high performance liquid chromatography, the pretreatment conditions were optimized and effects of extraction, concentration, purification on the recovery of the 7 targets were explored. After automatically accelerating solvent extraction of the soil sample by the mixed solution consisting of acetone and n-hexane at volume ratio of 1:1, the extract was reduced to 5.0 mL under conditions of vacuum pressure of 0.06-0.07 MPa and temperature of 30℃, and further concentrated to about 1.0 mL under conditions of nitrogen pressure of 100 kPa and temperature of 30℃. If the sample needed to be purified, the above concentrated solution was directly passed through the activated Supelco magnesium silicate solid phase extraction column, and targets was eluted by the mixed solution composed of dichloromethane and n-hexane at volume ratio of 1:1. The targets in the eluent (concentration solution when purification was not requided) was displaced into acetonitrile, and the solution was diluted to 1.0 mL by acetonitrile. Targets in which were separated by SUPELCO LC-PAH chromatographic column, detected by a diode array detector and a fluorescence detector in series, and quantified by external standard method. It was shown that the segmented concentration method mentioned above could effectively reduce the loss of the targets. By analyzing the segmented simulated solutions in the pretreatment process, it was found that the extraction, purification, and nitrogen blowing concentration processes had a relatively small effect on the recovery of the 7 targets, while the vacuum concentration process had a significant effect. Linear relationships between values of the mass concentration and the peak area were kept in the ranges of 0.20-10.0 mg·L^-1 (decafluorobiphenyl) and 0.04-2.00 mg·L^-1 (the 6 targets), respectively. Detection limits (3.143s) were found in the range of 0.2-2.0 μg·kg^-1. The proposed method was used for analysis of the standard sample, and the determined values were within the uncertainty ranges of the identified values, with RSDs (n=5) of the determined values in the range of 1.4%-5.7%.

Ethyl acetate (20 mL) and 3.0 g of sodium chloride were added into 5 g of fruit puree of infant dietary supplement sample. The mixture was vortexed for 1 min, and centrifuged for 5 min. The extraction was repeated once with 20 mL of ethyl acetate. The two supernatants were combined and evaporated to near dryness under vacuum at 40℃. The residue was dissolved in 5 mL of methanol. The solution was passed through the activated C₁₈ solid phase extraction column, and the entire effluent was collected, and dried to near dryness by nitrogen at 40℃. Then 1 mL of heptane was added, and vortex process was made for 1 min to dissolve the residue. The solution obtained was filtered through a 0.22 μm organic phase filter membrane, and the filtrate was analyzed by UPC². Acquity Trefoil AMY1 column was used as the stationary phase. Mixed solutions composed of methanol solution containing 0.5% (φ) ammonia and supercritical carbon dioxide at different volume ratios were used as the mobile phase for gradient elution. (-)-Fenpropathrin and (+)-fenpropathrin were determined by external standard method at detection wavelength of 230 nm. It was shown that linear relationships between values of the mass concentration and peak area of the fenpropathrin enantiomers were kept in the range of 1.0-20.0 mg·L^-1, with lower limits of determination (10S/N) of 0.2 mg·kg^-1. The spiked recovery test was made at three concentration levels on the negative fruit puree samples, giving recoveries of the 2 targets in the range of 81.4%-106%, and RSDs (n=6) of the determined values in the range of of 4.1%-7.2%. The proposed method was used for the analysis of 20 fruit puree samples, and (-)-fenpropathrin (0.25 mg·kg^-1) and (+)-fenpropathrin (0.22 mg·kg^-1) were detected in one pear puree sample.

The study mentioned by the title was conducted for problems including long soaking extraction time and susceptibility of detection results to chromogenic time, chromogenic temperature, and soil acidity by silicon molybdenum spectrophotometry in standard methods of LY/T 1266-1999 or NY/T 1121.15-2006 to detect the available silicon in soil. The 5.00 g of sample and 50.00 mL of 0.025 mol·L^-1 citric acid solution were added into a plastic bottle. After capping the bottle and vortexing, the above mixture was extracted at 30℃ for 2.0 h under 300 W ultrasound power. The extract was filtered with qualitative filter paper, and the filtrate was introduced into the inductively coupled plasma atomic emission spectrometer. The available silicon in soil was determined at the conditions of radio frequency power of 1 150 W, atomizing gas flow of 0.55 L·min^-1, and analytical spectral line of 251.611 nm. As found by the results, linear relationship between values of the mass concentration and response intensity of silicon was kept within 100.0 mg·L^-1, and detection limit (3s) was 0.012 mg·kg^-1. The proposed method was used for the analysis of 19 soil reference materials with different acidity, giving determined values within the uncertainty ranges of the certified values, and RSDs (n=12) of the determined values less than 10%. There was no significant difference between the proposed method and silicon molybdenum spectrophotometry given by the above standard methods, indicating the proposed method was suitable for accurate and rapid determination of available silicon in large batches of soil with different acidity.

After the sample was dried, crushed, and sieved, an aliquot (3.0 g) was taken, and 5 mL of 1.0% (volume fraction) glacial acetic acid solution was added to completely immerse the sample by vortex. After soaking for 30 min, 15 mL of acetonitrile was added, and the mixture was shaken vigorously for 10 min. Then 4.0 g of anhydrous magnesium sulfate (AMS) and 1.0 g of sodium chloride were added, and the mixture was shaken vigorously to prevent salt agglomeration, shaken vigorously for another 10 min, and centrifuged for 10 min. All the supernatant was collected, and blown to near dryness by nitrogen at 40℃, and the residue was dissolved in 1 mL of 50% (volume fraction) acetonitrile solution. The obtained solution was introduced into the ultra-high performance liquid chromatograph-tandem mass spectrometer, and the targets were separated on the Waters AQUITY UPLC BEH Shield RP18 chromatographic column by gradient elution with mixed solutions composed of 0.05% (volume fraction, the same below) formic acid solution containing 5 mmol·L^-1 ammonium formate and acetonitrile solution containing 5 mmol·L^-1 ammonium formate and 0.05% formic acid at different volume ratios, and ionized by the ESI⁺ and ESI^- modes, detected by the sMRM mode, and quantified by matrix matching method. It was shown that linear relationships between values of the mass concentration and the corresponding peak area of 23 plant growth regulators were kept in definite ranges, with lower limits of determination (10S/N) in the range of 0.2-3.0 μg·kg^-1. Test for recovery was made according to the standard addition method, giving recoveries in the range of 75.2%-109%, and RSDs (n=5) of the determined values ranged from 1.8% to 13%. The proposed method was used for the analysis of 46 batches of Codonopsis Radix and 30 batches of Angelica sinensis samples. Among them, detection amounts of sodium 4-nitrophenol in 10.9% of Codonopsis Radix samples and 6.7% of Angelica sinensis samples exceeded the limit (100 μg·kg^-1) specified in GB 2763-2021.

Migration tests were conducted using water, 4% (volume fraction) acetic acid solution, isooctane, and ethanol solutions with volume fractions of 10%, 20%, 50%, and 95% as food simulants, in accordance with the provisions of GB 5009.156-2016 and GB 31604.1-2015. Direct injection analysis was made on the soaking solution of the 6 food simulants(except isooctane). The 10 mL of isooctane soaking solution was taken, and 10 mL of 40% (volume fraction) methanol solution was added. The mixed solution was shaken for 1 min, and settled for 30 min. The lower methanol solution was collected and passed through a 0.22 μm organic filter membrane. The filtrate was analyzed by the instrument. Chromatographic analysis was performed using ACQUITY UPLC BEH C₁₈ chromatographic column as the stationary phase, and 50% (volume fraction) methanol solution containing 0.1% (volume fraction) formic acid was used as the mobile phase for isocratic elution separation. The mass spectrometry analysis was carried out using the positive ion (ESI⁺) mode of the electric spray ion source and multiple reaction monitoring (MRM) mode. It was shown that linear relationships between values of the mass concentration of hindered amine light stabilizer UV4050 in different food simulants and the peak area were kept in the range of 5-200 μg·L^-1, with lower limits of determination (10S/N) in the range of 0.6-2.4 μg·L^-1. Test for recovery was conducted by the standard addition method, giving recoveries in the range of 88.1%-109%, and RSDs (n=6) of the determined values ranged from 0.90% to 8.9%. The proposed method was successfully used for the analysis of actual plastic food contact material samples.

After crushing and sieving the tea sample, an aliquot (2.50 g) was taken, and 2.0 mL of water was added for wetting. Then 20 mL of acetonitrile solution containing 1% (volume fraction) formic acid was added, and the mixture was vortexed for 3 min, and centrifuged at 4℃ for 10 min. An aliquot (1.0 mL) of the supernatant was taken and placed into a 2.0 mL-centrifuge tube containing the purifiers (250 mg of anhydrous magnesium sulfate and 150 mg of multiple walled carbon nanotubes). The mixture was vortexed for 3 min, and centrifuged at 4℃ for 10 min. The supernatant was collected, and passed through a 0.22 μm organic phase filter membrane. The initial filtrate was discarded, and the subsequent filtrate was analyzed by ultra-high performance liquid chromatography-tandem mass spectrometry. In chromatographic analysis, Agilent Poroshell 11 chromatographic column was used as the stationary phase, and mixed solutions composed of 0.1% (volume fraction) formic acid solution and acetonitrile at different volume ratios were used as the mobile phase for gradient elution separation. In mass spectrometry analysis, electrospray ion source positive ion (ESI⁺) mode was used for ionization, and multiple reaction monitoring (MRM) mode was used for detection. It was shown that linear relationships between values of the mass concentration of fumonisins B₁, B₂, and B₃ and the corresponding peak area were kept in the range of 0.5-100.0 μg·L^-1, with detection limits (3S/N) in the range of 0.15-1.00 μg·kg^-1. Test for recovery was made according to the standard addition method, giving recoveries in the range of 82.1%-108%, and RSDs (n=6) of the determined values ranged from 2.7% to 5.3%. The proposed method was used for the analysis of 50 batches of tea samples, and fumonisin B₁ was detected in a batch of black tea sample, with detection amount of 8.321 μg·kg^-1.

A method of high performance liquid chromatography-tandem mass spectrometry was proposed for the simultaneous determination of 5 persistent, bioaccumulative and toxic (PBT) substances in toys. The coatings, plastics, and textiles of toys were collected and treated in accordance with ISO 8124-3:2020, and an aliquot (1 g) was taken, and mixed with 10 mL of toluene. After sealing, ultrasonic extraction was performed at room temperature for 30 min. The supernatant was taken and passed through a 0.45 μm filter membrane, and the filtrate was analyzed by high performance liquid chromatograph-tandem mass spectrometer. In the chromatography analysis, Agilent Poroshell HPH-C₁₈ column was used as the stationary phase, and mixed solutions composed of methanol and 0.1% (volume fraction) acetic acid solution at different volume ratios were used as the mobile phase for gradient elution separation. In the mass spectrometry analysis, ESI⁺ and MRM modes were used for scanning, and external standard method was used for quantification. It was shown that linear relationships between values of the mass concentration of 5 PBT substances and the peak area were kept in the range of 0.005-0.2 mg·L^-1, with detection limits (3S/N) in the range of 0.010-0.078 mg·kg^-1. Test for recovery was made according to the standard addition method, giving recoveries in the range of 85.7%-105%, and RSDs (n=6) of the determined values were not greater than 7.0%.

The existing methods for the determination of trimethylamine in seawater had problems such as large sample amount, expensive instrument, or cumbersome operations, so the research mentioned by the title was conducted. An aliquot (10.00 mL) of seawater sample was taken and placed into a 20 mL-headspace bottle, 2.5 g of sodium chloride, 0.8 g of potassium sulfate, and 2.5 mL of 7.5 mol·L^-1 sodium hydroxide solution were added. The mixture was equilibrated at 85℃ for 40 min. The obtained gas was introduced into the gas chromatograph, and the separation was conducted by heating program on the CP-Volamine quartz capillary column, and trimethylamine was determined by the nitrogen phosphorus detector, with the matrix matching method for quantification. It was shown that linear relationship between values of the mass concentration of trimethylamine and the response signal was kept in the range of 5.0-100.0 μg·L^-1, with detection limit (3.143s) of 0.4 μg·L^-1.The proposed method was applied to the analysis of the spiked blank sample, RSDs (n=5) of the determined values was 2.1%, and recoveries ranged from 92.0% to 118%.

The 2 mL of water sample was taken, and 6 mg of trisodium citrate dihydrate, and 1 mL of 0.05 mol·L^-1 sodium tetraborate solution, and 2 mL of 1 g·L^-1 9-fluorene methyl chloroform (FMOC-Cl) solution were added sequentially. The mixed solution was reacted to derivatize targets at room temperature with ultrasonic power of 250 W for 10 min. Then 0.40 g of sodium chloride was added for salting out, and the mixture was vortexed for 2 min, and settled for 1 min. The lower water phase was collected, and passed through a 0.45 μm filter membrane, and the filtrate was analyzed by high performance liquid chromatography. PAH C₁₈ chromatographic column was used as the stationary phase, and the mixed solutions composed of acetonitrile and 0.2% (volume fraction) phosphoric acid solution at different volume ratios were used as the mobile phase for gradient elution separation, and fluorescence detector was used for detection. It was shown that linear relationships between values of the mass concentration of glufosinate, glyphosate, and aminomethylphosphonic acid and the peak area of their derivatization products were kept in the range of 0.400-50.0 μg·L^-1, with detection limits (3.143s) of 0.2, 0.1, 0.1 μg·L^-1, respectively. Test for recovery was made according to the standard addition method, giving recoveries in the range of 87.6%-100%, and RSDs (n=6) of the determined values ranged from 5.7% to 12%. The proposed method was used for the analysis of actual water samples, and the detection results were all negative.

The widespread presence of sulfur in metal ores will affect the smelting process and the evaluation of ore deposits. The analysis of the content and specie of sulfur can provide effective references for desulfurization and reduction of sulfur in metal ores, ore exploration and utilization of slag resources. The pretreatment methods (high temperature combustion, digestion, alkali melting, etc.) and detection methods (infrared absorption spectroscopy, elemental analysis, inductively coupled plasma atomic emission spectrometry, ion chromatography, etc.) for determination of sulfur in metal ore and slag were reviewed. The pretreatment methods and detection methods applicable to analysis of sulfur specie were summarized, and the development future of the above methods was prospected (44 ref. cited).

Common fluorescence visualization sensors (ratiometric, paper-based, and molecularly imprinted fluorescence sensors), fluorescence visualization sensing mechanisms (fluorescence resonance energy transfer, internal filtering effect, photoinduced electron transfer, aggregation-induced burst, aggregation-induced emission, intramolecular charge transfer, metal-ligand charge transfer, etc.) and their determination methods were introduced. The application of fluorescence visualization probes made by luminescent substances such as quantum dots (common quantum dots and biomass quantum dots), organic fluorescence material, and metal fluorescence nanoclusters in the food analysis was reviewed, and the development future was prospected (69 ref. cited).