[Discussion on the application status and method improvement of gas chromatography in occupational health inspection standards in China].

As a rapid, accurate and efficient analytical technique, gas chromatography is widely used in the detection of volatile organic compounds and inorganic small molecule toxins, and it is the main analytical method in the national testing standards for occupational health. The existing effective national standards of gas chromatography for the detection of some substances have low column efficiency, high toxicity of reagents, poor correlation of the standard curve and low desorption efficiency and other problems, some of which can be solved through method improvement. At the same time, with the use of new materials and new processes, new types of toxic substances are emerging, and there are still many occupational disease hazards of limited value without supporting detection methods, gas chromatography can be applied to the detection of some toxic substances to better complement the vacancy of China's occupational health detection methods. This paper analyzes the current situation of the application of gas chromatography in occupational health testing standards, discusses the improvement of some of these methods, and helps to promote the application and development of gas chromatography in occupational health testing.

[Determination of 4-methyl-2-pentanol in workplace air by solvent desorption-gas chromatography].

Objective: To establish a method for the determination of 4-methyl-2-pentanol in the air of workplace by gas chromatography. Methods: In January 2022, 4-methyl-2-pentanol in the air of workplace was collected by activated carbontube, eluted with dichloromethane-methanol (95∶5, V/V), separated by capillary column and determined by gas chromatogram. Results: The limit of detection for 4-methyl-2-pentanol was 0.04 µg/ml. The linear range of 4-methyl-2-pentanol was 0.16-1616.60 µg/ml, with the regression equation of y=1.94x-5.48, and the coefficient correlation was 0.99958, and the minimum detection concentration was 0.03 mg/m(3) (collected sample volume was 1.50 L). The within-run precisions were 1.08%-1.75% and the between-run precisions were 1.41%-2.52%. The desorption rates were 95.15%-99.91%. The samples could be stored at least 3 days at room temperature and 7 days at 4 ℃ without significant loss. Conclusion: The method has the advantages of good precision, high sensitivity and simple operation. It is suitable for the determination of 4-methyl-2-pentanol in the air of workplace.

[Determination of acetylacetone in workplace air by solvent desorption-gas chromatography].

Objective: To establish a method for the determination of acetylacetone in the air of workplace by gas chromatography. Methods: In August 2020, acetylacetone in the air of workplace was collected by silica gel tube, eluted with methanol, separated and detected by gas chromatography with flame ionization detector. The detection limit and precision of the method were also analyzed. Results: The linear range of acetylacetone was 1.95-1950.60 µg/ml with the regression equation of y=0.815x-3.667, and the correlation coefficient was 0.99993. The limit of detection of the method was 0.18 µg/ml and the minimum detection concentration was 0.12 mg/m(3) (collected sample volume was 1.50 L). The within-run precisions were 1.08%-4.11% and the between-run precisions were 1.98%-2.80%. The desorption rates were 99.68%-100.45%. The sealed samples could be kept at least 15 days at room temperature without significant loss. Conclusion: The solvent desorption-gas chromatography method for the determination of acetylacetone has good precision, high sensitivity and simple operation, and is suitable for the determination of acetylacetone in the air of the workplace.

[Determination of chlorobenzene metabolite-p-chlorophenol in urine by solid phase extraction-gas chromatography].

Objective: A method to determine chlorobenzene metabolite-p-chlorophenol in urine by solid phase extraction-gas chromatography was established. Methods: In May 2021, the urine sample was hydrolyzed at 100 ℃ for 1.5 h with 2 ml concentrated hydrochloric acid. After cooling and filtering, the sample was enriched and purified by Oasis(®)MAX 6cc SPE column. Drip washing with 0.01 mol/L hydrochloric acid solution and elution with acetonitrile, the eluent was volumized to 5 ml with acetonitrile and determined by gas chromatography, and quantify by standard curve method. Results: Calibration curve of the method was linear within the range of 1.61-80.30 µg/ml and showed good linearity with r=0.9997, the regression equation was y=1.51602x-0.10234. The determination limit was 0.17 µg/ml, and the limit of quantitation was 0.55 µg/ml. Recovery rates were between 89.3%-104.4%, the relative standard deviation (RSD) of intra-day measurements ranged from 4.3% to 6.7%, and the RSD of inter-day measurements ranged from 4.5% to 6.7%. Conclusion: This method could optimize sample pretreatment, and eliminate the interference of impurities, which is sensitive, efficient and accurate for the determination of chlorobenzene metabolite-p-chlorophenol in urine.

[The method of determination for butyronitrile and isobutyronitrile in the air of workplace by dissolved desorption-gas chromatography].

Objective: To establish a method for the determination of butyronitrile and isobutyronitrile in the air of workplace by gas chromatography. Methods: In March 2020, butyronitrile and isobutyronitrile in the air of workplace was collected by silica gel, eluted with methanol, separated and determined by gas chromatogram with flame ionization detector, the characteristics of determination of nitrile and isobutyronitrile by gas chromatography were analyzed. Results: The limit of detection for butyronitrile and isobutyronitrile was 0.33 µg/ml. The linear range of butyronitrile determined by this method was 1.60-1600.00 µg/ml, y=2.295x-3.480, and the coefficient correlation was 0.99998, and the minimum detection concentration was 0.22 mg/m(3) (collected sample volume was 1.50 L) . The within-run precisions were 2.43%-4.12%, the between-run precisions were 1.72%-3.70%, and the desorption rates were 93.26%-98.41%. The linear range of isobutyronitrile determined by this method was 1.52-1520.00 µg/ml, y=2.208x-0.102, and the coefficient correlation was 0.99998, and the minimum detection concentration was 0.22 mg/m(3) (collected sample volume was 1.50 L) . The within-run precisions were 2.52%-3.22%, the between-run precisions were 1.20%-3.82%, and the desorption rates were 96.85%-102.50%. The sealed samples could be stored at least 10 days at room temperature without significant loss. Conclusion: The method has the advantages of good precision, high sensitivity and simple operation. It is suitable for the simultaneous determination of butyronitrile and isobutyronitrile in the air of workplace.

[Rapid determination of 30 volatile organic compounds in workplace air by gas chromatography].

Objective: To establish a method for rapid detection of DB-WAX capillary column and determination of the workplace air in 30 kinds of volatile organic pollutants. Methods: In August 2020, N-pentane, n-hexane, methylcyclohexane, octane, Acetone, ethyl acetate, butanone, benzene, 3-pentanone, trichloroethylene, tetrachloroethylene, toluene, butyl acetate, 2-hexanone, Isoamyl acetate, ethylbenzene, p-xylene, m-xylene, amyl acetate, o-xylene, chlorobenzene, styrene, cyclohexanone, P-chlorotoluene, bromobenzene, M-dichlorobenzene, p-dichlorobenzene, O-dichlorobenzene, o-Chlorotoluene, 1, 2 , 4-trichlorobenzene of 30 kinds of substances in air were collected by activated carbon tube. After analysis by carbon disulfide, the analytical solution was analyzed by DB-WAX column and determined by FID detector. Results: The above 30 kinds of volatile organic pollutants had good separation effect, the correlation coefficient of the standard curve was above 0.999, the relative standard deviation was 0.1%-3.2%, the desorption efficiency was 77.0%-117.1% , the lower limit of quantitation was 0.33-5.33 µg/ml, and the lowest quantitation concentration was 0.22-3.55 mg/m(3), the recoveries ranged was 95.4%-104.9%. Conclusion: The method can effectively separate and accurately determine 30 volatile organic compounds in these workplaces, and the method is simple and quick.

The method of determination for butyronitrile and isobutyronitrile in the air of workplace by dissolved desorption-gas chromatography / 中华劳动卫生职业病杂志

Objective: To establish a method for the determination of butyronitrile and isobutyronitrile in the air of workplace by gas chromatography. Methods: In March 2020, butyronitrile and isobutyronitrile in the air of workplace was collected by silica gel, eluted with methanol, separated and determined by gas chromatogram with flame ionization detector, the characteristics of determination of nitrile and isobutyronitrile by gas chromatography were analyzed. Results: The limit of detection for butyronitrile and isobutyronitrile was 0.33 μg/ml. The linear range of butyronitrile determined by this method was 1.60-1600.00 μg/ml, y=2.295x-3.480, and the coefficient correlation was 0.99998, and the minimum detection concentration was 0.22 mg/m(3) (collected sample volume was 1.50 L) . The within-run precisions were 2.43%-4.12%, the between-run precisions were 1.72%-3.70%, and the desorption rates were 93.26%-98.41%. The linear range of isobutyronitrile determined by this method was 1.52-1520.00 μg/ml, y=2.208x-0.102, and the coefficient correlation was 0.99998, and the minimum detection concentration was 0.22 mg/m(3) (collected sample volume was 1.50 L) . The within-run precisions were 2.52%-3.22%, the between-run precisions were 1.20%-3.82%, and the desorption rates were 96.85%-102.50%. The sealed samples could be stored at least 10 days at room temperature without significant loss. Conclusion: The method has the advantages of good precision, high sensitivity and simple operation. It is suitable for the simultaneous determination of butyronitrile and isobutyronitrile in the air of workplace.

Rapid determination of 30 volatile organic compounds in workplace air by gas chromatography / 中华劳动卫生职业病杂志

Objective: To establish a method for rapid detection of DB-WAX capillary column and determination of the workplace air in 30 kinds of volatile organic pollutants. Methods: In August 2020, N-pentane, n-hexane, methylcyclohexane, octane, Acetone, ethyl acetate, butanone, benzene, 3-pentanone, trichloroethylene, tetrachloroethylene, toluene, butyl acetate, 2-hexanone, Isoamyl acetate, ethylbenzene, p-xylene, m-xylene, amyl acetate, o-xylene, chlorobenzene, styrene, cyclohexanone, P-chlorotoluene, bromobenzene, M-dichlorobenzene, p-dichlorobenzene, O-dichlorobenzene, o-Chlorotoluene, 1, 2 , 4-trichlorobenzene of 30 kinds of substances in air were collected by activated carbon tube. After analysis by carbon disulfide, the analytical solution was analyzed by DB-WAX column and determined by FID detector. Results: The above 30 kinds of volatile organic pollutants had good separation effect, the correlation coefficient of the standard curve was above 0.999, the relative standard deviation was 0.1%-3.2%, the desorption efficiency was 77.0%-117.1% , the lower limit of quantitation was 0.33-5.33 μg/ml, and the lowest quantitation concentration was 0.22-3.55 mg/m(3), the recoveries ranged was 95.4%-104.9%. Conclusion: The method can effectively separate and accurately determine 30 volatile organic compounds in these workplaces, and the method is simple and quick.

[Simultaneous determination of saturated and aromatic hydrocarbons in soil by on-line high performance liquid chromatography-gas chromatography].

To strengthen regulation for mitigating the risk posed by petroleum contaminants in soil, the Ministry of Ecology and Environment of the People's Republic of China has classified petroleum hydrocarbons as a key monitoring item for regulatory contamination monitoring. Petroleum is principally derived from petroleum and synthetic fuels, which contain an extremely high content of hydrocarbon compounds that have varied boiling points. These compounds are chemically classified primarily as saturated and aromatic. Aromatic hydrocarbons are typically highly alkylated monocyclic, bicyclic, and polycyclic, which are more toxic to human and animal life than saturated hydrocarbons. Because of the significant toxicological differences among the various hydrocarbons, it is difficult to accurately assess their environmental toxicity by only determining the total content of petroleum in soil. However, there are no analytical methods for the simultaneous determination of saturated hydrocarbons and aromatic hydrocarbons in soil according to Chinese standards. In this study, extraction and purification procedures were completely optimized depending on the matrix of the soil samples. The advanced analytical technique of on-line high performance liquid chromatography-gas chromatography (HPLC-GC) was performed after sample preparation for the simultaneous determination of saturated hydrocarbons and aromatic hydrocarbons in soil. For the extraction, n-hexane/ethanol (1∶1, v/v) was chosen as the extraction solvent. The ratio of solid sample (soil) to the solvent was chosen as 1∶4, and extraction was performed once at room temperature, for 1 h. Water was then added and mixed to remove ethanol from the extracts, and the upper n-hexane layer was separated; thus, the petroleum hydrocarbons in the samples were completely extracted. However, the oils and fats in the matrix of the soil sample were also simultaneously extracted. Because of the limited retention capacity of the HPLC column, the presence of oils, fats, and other interferents would affect the subsequent determination of saturated hydrocarbons and aromatic hydrocarbons. Therefore, an additional purification step is required before sample injection into the HPLC-GC equipment. In this study, purification was performed using a lab-made silica gel column, which is commonly used for the determination of saturated hydrocarbons and aromatic hydrocarbons in food. The purification column was conditioned and eluted with an 8∶2 ratio (v/v) of n-hexane to dichloromethane after sample loading. Subsequently, the eluent was concentrated and injected into the HPLC-GC equipment for analysis. The flame ionization detector (FID) is ideal for petroleum hydrocarbons quantification because of its nearly identical responses to all hydrocarbons; hence, with the FID, reference standards are not required for quantification, and internal standards are typically used for quantifying the total hydrocarbon content. In this study, cyclohexylcyclohexane (Cycy) and 2-methylnaphthalene (2-MN) were used as internal standards for determining the saturated and aromatic hydrocarbons, respectively. The limit of quantification (LOQ) of this proposed method was 0.4 mg/kg. Moreover, the suitability of the method was verified by comparing the obtained content against the soil petroleum hydrocarbon standard (SQC-116); the measured value was found to be within the credible interval provided by the standard. The relative error (RE) was 10.6% with a relative standard deviation (RSD) of 1.4%, which indicates that the proposed method is accurate and reliable, and the precision meets analytical requirements. Finally, the method was applied to the determination of hydrocarbons in five soil samples from the Beijing area. Saturated hydrocarbons (C10-C40) were detected in all five samples, with contents ranging from 3.3 to 32.1 mg/kg, while aromatic hydrocarbons (C10-C40) were detected in four samples, with contents ranging from 0.8 to 4.3 mg/kg. HPLC-GC combines the high selectivity of HPLC with the high separation efficiency of GC, and as demonstrated in this study, can be used for the simultaneous determination of saturated and aromatic hydrocarbons in soil. The source of hydrocarbon contamination can also be preliminarily identified by chromatographic analysis.

[Determination of hydrazine in workplace air by gas chromatography with large bore capillary column].

Objective: To determine hydrazine quantitatively in workplace air by gas chromatography with large bore capillary column. Methods: In October 2019, hydrazine in the air was adsorbed by acid silica gel tube sampling and desorped using sulfuric acid solution. After derivatization with furfural and extraction, the content of hydrazine was determined by DM-FFAP capillary column gas chromatography with flame ionization detector. Results: The linear regression equation was y=353.8x+21.2 (r=0.9998) between 0.1-2.0 µg/ml of target concentration. The detection limit was 0.030 µg/ml. The lower limit of quantification was 0.100 µg/ml. If 15 L air sample was collected, the minimum detection concentration was 0.004 mg/m(3) and the minimum quantitative concentration was 0.013 mg/m(3) respectively. The average desorption efficiency was 86.5%-89.4%. The recovery was 94.4%-97.1%. The relative standard deviation was 1.6%-4.9%. Hydrazine and furfural derivative was 2-furaldehyde hydrazine. Conclusion: The method has symmetrical peak shape of hydrazine derivatives chromatographic peaks, short analysis time, easy operation, and is suitable for the determination of the concentration of hydrazine in the air in the workplace.

[Determination of chloroacetic acid in workplace air by silanization-gas chromatography].

Objective: A method to determine acrylic acid in workplace air was developed by silanization-gas chromatography. Methods: In March 2020, chloroacetic acid in air were absorbed by silica gel tube, the samples were dried, then were desorbed and silanized by acetonitrile: N, O-bis (trimethylsilane) trifluoroacetamide (2∶1, V/V) at room temperature, allowed quantitative analysis of chloroacetic acid as its silanization product by gas chromatography. Results: Calibration curve of the method was linear within the range 0-162.8 µg/ml and showed good linearity with linear equation: y=0.011 8x, r=0.999 7. The determination limit of the method was 0.8 µg/ml, and the minimum detection concentration was 0.05 mg/m(3) (collect 15 L air) . The relative standard deviation (RSD) was 0.5%-1.3% (n=5) . Recoveries were between 98.6%-101.2%. Conclusion: The results prove silanization-gas chromatography is an accurate, simple and high sensitive method for determining chloroacetic acid in workplace air.

Thermal Stability and Monomer Elution of Bulk Fill Composite Resins Cured from Different Irradiation Distances.

Objectives : This study aimed to evaluate the thermal stability and monomer elution of bulk fill composite resins cured at different irradiation distances. Materials and Methods: Forty cylindrical-shaped (3×4mm) specimens were fabricated from two composite resins (X-tra fil, X-tra base) and cured from 0 and 7mm distances. In 9 specimens, the degree of conversion was determined by the release of monomers. For this purpose, after curing of composites, they were immersed in 5 mL of 99.9% methanol and stored at 37°C for 24h. The eluted monomer was then analyzed by gas chromatography (GC). Also, thermal stability of one sample from each group was assessed by thermogravimetric analysis (TGA) at a rate of 10°C/min. Data were analyzed using two-way ANOVA and Tukey's post-hoc test (P<0.05). Results: X-tra fil had significantly higher degree of conversion than X-tra base (P=0.001). Specimens cured at 7mm distance had significantly lower degree of conversion compared with those cured at 0 mm distance (P=0.001). The interaction effect of composite type and distance of light curing unit from the surface of samples was statistically significant (P=0.001). Regarding the TGA results, the lowest and the highest percentages of weight loss were detected in X-tra fil cured at 0 mm distance and X-tra base cured at 7mm distance, respectively. Conclusion: X-tra fil composite cured at 0mm distance had the highest degree of conversion and thermal stability, and X-tra base composite cured at 7mm distance had the lowest values.

[Application of a new solid adsorbent tube for the determination of three kinds of epoxy eompounds in air].

Objective: To develop a new solid sorbent tube for simultaneously capturing ethylene oxide (EO) , propylene oxide (PO) and epichlorohydrin (ECH) in air, and establish a complete set of method. Methods: In June 2018, EO, PO and ECH in air were captured by the new solid sorbent tube filled with carbon aerogel adsorbent, desorbed with solution of 5% (V/V) methanol-methylene chloride, separated through capillary chromatographic column, and then analyzed by gas chromatography-flame ionization detector. Results: The linear ranges of EO, PO and ECH were 0.24-960.00, 0.60-2384.00 and 0.12-472.40 mg/L respectively, and the related coefficients were between 0.99995-0.99997. The relative standard deviations (RSD) within the group were 1.66%-4.09%, 1.36%-4.43%, and 1.99%-5.65%, respectively, and the RSD between the group were 2.69%-4.95%, 2.77%-5.30%, and 3.27%-6.67%, respectively. The average desorption efficiencies were 88.25%-94.50%, 98.17%-98.60%, and 97.79%-101.04%, respectively. The samples could be stored at 4 ℃ refrigerator for at least 27 days. Conclusion: The newly developed solid sorbent tube filled with carbon aerogel adsorbent and its complete set of gas chromatography method could be used for sampling and quantitative detection of EO, PO and ECH in workplace air.

Evaluación de las características fisicoquímicas y de la actividad antimicrobiana del aceite del árbol de té contra Cutibacterium acnes (Propionibacterium acnes) ATCC 6919 / Evaluation of tea tree oil physicochemical features and its antimicrobial activity against Cutibacterium acnes (Propionibacterium acnes) ATCC 6919

Resumen: Introducción. El aceite del árbol de té es un aceite esencial reconocido por sus propiedades antimicrobianas. Objetivos. Evaluar la composición, características y efecto antimicrobiano del aceite al 2 % del árbol de té y su concentración inhibitoria mínima (CIM) contra Cutibacterium acnes (Propionibacterium acnes). Materiales y métodos. Se evaluó el quimiotipo en tres lotes diferentes de este aceite mediante cromatografía de gases, así como su actividad antimicrobiana en concentración al 2 % v/v y la CIM contra C. acnes mediante ensayo de difusión en agar (guía M11-A8 CLSI). Resultados. Los lotes evaluados presentaron los quimiotipos ajustados a la norma ISO 4730, lo que indicó la alta calidad del producto. Los lotes contenían de 30 a 40 % de terpinen-4-ol, compuesto que favorece la actividad antimicrobiana, la cual presentó en todos los lotes un efecto dependiente de la concentración contra C. acnes, con una inhibición del crecimiento microbiano en concentración al 2 % v/v en todas las pruebas. La concentración inhibitoria mínima fue de 0,25 % v/v. La actividad antimicrobiana del aceite del árbol de té contra este microorganismo ya ha sido reportada con una concentración inhibitoria mínima entre 0,05 y 1,25 % v/v, rango que cobija la obtenida en este estudio. Conclusiones. Los resultados evidenciaron la gran calidad de este producto y su capacidad como agente antibacteriano contra C. acnes. Se deben hacer estudios con otros aislamientos del microorganismo provenientes de pacientes con acné vulgar para confirmar su actividad general y la de cada uno de sus componentes.

Abstract: Introduction: Tea tree oil is an essential oil recognized for its antimicrobial properties. Objective: To evaluate the composition, features, and antimicrobial effect at 2% v/v, and its minimal inhibitory concentration (MIC) against Cutibacterium acnes (Propionibacterium acnes). Materials and methods: Three different batches of tea tree oil were evaluated. We characterized its chemotype by gas chromatography and its 2% v/v antimicrobial activity against C. acnes by agar diffusion assay (guide M11-A8 CLSI). Results: The three batches of oil had the chemotypes required by the ISO 4730 standard, which indicates that it is a high-quality product. Additionally, they had 30% to 40% of terpinen-4-ol, a compound that favors its antimicrobial activity. Antimicrobial activity against C. acnes for all batches had a concentration-dependent effect with microbial growth inhibitory activity in all assays at 2% v/v. The MIC obtained against C. acnes for all batches was 0.25% v/v. The antimicrobial activity of tea tree oil against this microorganism has been previously reported with a MIC between 0.05% and 1.25% v/v, a range that covers the one obtained in this study. Conclusion: These results show the high quality of the oil and its capacity as an antibacterial agent against C. acnes. New studies should be conducted to confirm its activity and that of its components in isolates of the microorganism from patients with acne vulgaris.

[Determination of isobutyl methacrylate in workplace air by gas chromatography].

Objective: To establish a gas chromatography method for detecting isobutyl methacrylate in workplace air. Methods: From July to October 2019, isobutyl methacrylate in workplace air was collected by activated charcoal tube, absorbed using carbon disulfide and analyzed by gas chromatography (FID) with FFAP capillary column. Results: The linear range of isobutyl methacrylate in the method was 0-800 µg/ml, the correlation coefficient was 0.99993. The detection limit was 0.35 µg/ml. The lowest detected concentration was 0.12 mg/m(3). The within-run precision was 2.06%-2.72%, the between-run precision was 3.03%-3.83%. The rates of desorption was 96.7%. The breakthrough volume was 14.46 mg. The average sampling efficience was 100%. The samples could be stored at room temperature for 7 days. Conclusion: The method is simple, highly sensitive and precise. Isobutyl methacrylate in workplace air could be determined accurately.

[Determination of trichlorobenzene in workplace air by solvent desorption gas chromatography].

Objective: To develop a solvent desorption-gas chromatography method for determination of trichlorobenzene in workplace air. Methods: Trichlorobenzene in workplace air were captured by Sampling tube consisting of glass fiber filter and solvent desorption activated carbon and desorbed with carbon disulfide, separated through capillary chromatographic column, and then analyzed by gas chromatography-electron capture detector. Results: The linear ranges of 1, 2, 3-trichlorobenzene, 1, 2, 4-trichlorobenzene and 1, 3, 5-trichlorobenzene were 12.20-1220.00, 16.60-1660.00 and 14.80-1480.00 µg/L, respectively, and the related coefficients were between 0.99946 to 0.99948. The relative standard deviations (RSD) within the groups of 1, 2, 3-trichlorobenzene, 1, 2, 4-trichlorobenzene and 1, 3, 5-trichlorobenzene were 1.96%-2.68%, 1.73%-2.82% and 1.81%-2.56%, respectively, and the RSD between the groups were 3.27%-4.25%, 2.85%-4.83% and 3.46%-4.43%, respectively. The average recovery efficiencies were 92.4%, 92.0% and 93.6%, respectively. The minimum quantification concentrations were 0.81, 1.53 and 1.18 µg/m(3), respectively (3 ml desorption solution, 15.00 L sample) . The samples could be stored at room temperature for at least 5 days. Conclusion: This method could be used for monitoring of 1, 2, 3-trichlorobenzene, 1, 2, 4-trichlorobenzene and 1, 3, 5-trichlorobenzene in workplace air.

[Determination of Cyclohexene in workplace air by Solvent desorption gas chromatography].

Objective: To establish a solvent desorption gas chromatography method for determination of cyclohexene in workplace air. Methods: Cyclohexene in the air of workplace was collected with carbon tube and desorbed by carbon disulfide. The target toxicant was separated with the GC column and analyzed with FID detector, identified by retention time, and quantified by peak area. Results: The linear range of cyclohexene in the air of workplace was 0.77~4 050.00 µg/ml, with a correlation coefficient of 0.9999. The limit of detection was 0.23 µg/ml. The lower limit of quantification was 0.77 µg/ml. The minimum detectable concentration was 0.15 mg/m(3) under1.5 L sampling volume and 1.0 ml extraction solution volume. The within-run precision of different cyclohexene concentrations was 0.62%~1.9% and the between-run precisions was 1.5%~3.5%; The average extraction efficiency was 96.4%; Penetration capacity (100 mg of carbon tube) was 29.4 mg; The average collection efficiency was 100%; The samples could be stored for 7 days at room temperature. When placed in 4 ℃ refrigerator, the samples could be stored for 14 days. The potential coexistence of cyclohexane, hexane, benzene, toluene and ethylbenzene with cyclohexene in the air did not interfere with the results of determination. Conclusion: This method has high sensitivity, precision, accuracy and lower limit of detection and it is applicable for determination of cyclohexene in workplace air.

[Determination of 1-methoxy-2-propanol in urine by headspace solid-phase microextraction coupled with gas chromatography].

Objective: To establish a method for the determination of 1-methoxy-2-propanol in urine using headspace solid phase micro-extraction coupled with gas chromatography. Methods: The 1-methoxy-2-propanol was enriched by headspace solid phase micro-extraction fiber coated with carbene/polydimethylsiloxane (CAR/PDMS) . Single factor rotation method was used to optimize the conditions of extraction temperature, salt amount, and extraction time. The separation was performed on DB-5 (30 m×0.32 mm×0.25 µm) capillary column and detected with flame ionization detector. The quantification was based on the standard curve. Results: The concentration of 1-methoxy-2-propanol in urine was linear in the range of 0.50-10.0 mg/L, and the linear correlation coefficient was 0.9993. The detection limit of the method was 0.14 mg/L, and the limit of quantification was 0.45 mg/L. The recovery was 85.8% to 104.7%, and the RSD of intra- and inter-batch precision were 3.25%-6.65% and 0.81%-3.96%, respectively. Conclusion: The method is high sensitivity and simple operation, and is suitable for the determination of 1-methoxy-2-propanol in urine of occupational exposure population.

[Determination of n-butyl alcohol in urine by headspace solid-phase microextraction coupled with gas chromatography].

Objective: To establish a headspace solid phase microextraction-gas chromatography method for determination of n-Butyl alcohol in urine. Methods: In October 2019, the n-butyl alcohol in urine was extracted with a polydimethylsiloxane/divinylbenzene (PDMS/DVB) solid-phase microextraction head. The conditions of salt amount, extraction temperature, extraction time and desorption time were optimized. The separation was performed on HP-5 (30 m×0.32 mm×0.25 µm) capillary column and detected with flame ionization detector. The quantification was based on the external standard curve. Results: The linear relationship of n-butyl alcohol in urine was good in the range of 0.04-3.00 mg/L, the correlation coefficient was 0.999, the detection limit of the method was 0.04 mg/L, the recovery was 77.4%-102.8%, the intra-run precision was 3.67%-8.11%, and the inter-assay precision was 4.94%-6.90%. Conclusion: The method has simple operation, high concentration efficiency and high sensitivity, and it is suitable for the determination of n-butyl alcohol in urine of occupational exposure to n-butyl alcohol.

[Determination of acrylic acid in workplaceair by on-line methylationgas chromatography].

A method to determine acrylic acid in workplace air was developed by on-line methylation gas chromatography. Methods: the samples were absorbed by solvent desorption silica gel tube and desorbed by methanol. Desorption fluid in the injector at 350 ℃ in the presence of an organic alkali tetramethylamine hydroxide (TMAH, 25% methanol) , allowed quantitative analysis of acrylic acid as its corresponding methyl derivative by gas chromatography. Results: calibration curve of the method was linear within the range 0-258.4 mg/L and showed good linearity with r=0.999 4. The determination limit of the method was 0.9 mg/L, and the minimum detection concentration was 0.06 mg/m(3) (collect 15 L air) . The relative standard deviation (RSD) was 2.2%-2.7% (n=5) . Recoveries were between 96.9-101.6%. Conclusion: the results prove on-line methylation gas chromatography is an accurate, simple and high sensitive method for determining acrylic acid in workplace air.