ABSTRACT
Background Volatile organic compounds (VOCs) in exhaled breath are closely associated with respiratory diseases and are linked to various metabolic reactions in the human body. A quantitative analytical method can provide technical support for studying VOCs related to various diseases. Objective To establish a thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) method for the determination of 27 VOCs in exhaled breath. Methods VOCs in exhaled breath were collected using a Bio-VOC sampler and enriched with Tenax TA thermal desorption tubes before TD-GC-MS analysis. Standards were collected using thermal desorption tubes and optimized for thermal desorption conditions as well as chromatographic and mass spectrometric conditions: The separation of the 27 VOCs was achieved by an optimized temperature program, the improvement of sensitivity by optimizing quantitative ions, and the increase of VOCs desorption efficiency by optimizing thermal desorption time and temperature. Limit of detection, limit of quantification, accuracy, precision, and stability of the proposed method were investigated by spiking with a blank gas bag, and exhaled breath samples from 20 healthy individuals were collected for an application study of the proposed method. Results The thermal desorption temperature was 280 ℃, and desorption time was 6 min. A VF-624ms chromatographic column was selected for the separation of target substances. The initial temperature of heating program was 35 ℃, maintained for 1 min, and then increased to 100 ℃ at a heating rate of 3 ℃·min−1 for 1 min, followed by increasing to 210 ℃ at a heating rate of 28 ℃·min−1 for 5 min. A quantitative analysis was conducted with a single ion monitoring (SIM) mode. Under these conditions, the 27 VOCs showed good linear relationships in their respective concentration ranges and the correlation coefficients were higher than 0.9990. The limits of detection of the method were in the range of 0.01-0.13 nmol·mol−1, the limits of quantification were in the range of 0.02-0.44 nmol·mol−1, and the spiked recoveries were in the range of 80.1%-120.5%, with intra-batch and inter-batch precision ≤ 18.8% and 17.9% respectively. All substances can be stored at room temperature (23-28 °C) for 7 d and at 4 °C for 14 d. The proposed method was applied to exhaled breath samples from 20 subjects with detection rates≥ 80% (except for trans-2-pentene and decane) and a concentration range of 0.00-465.50 nmol·mol−1. Conclusion The established TD-GC-MS method for quantification of VOCs in exhaled breath is characterized by high sensitivity and good accuracy, and is suitable for quantitative determination of VOCs in exhaled breath, which can provide technical support for the study of exhaled breath VOCs.
ABSTRACT
ObjectiveTo establish a method for the determination of 8 volatile halogenated hydrocarbons in drinking water， including vinyl chloride， trichloroethylene， tetrachloroethylene， tetrachloromethane， chloroform， dichlorobromomethane， dichlorodibromomethane， and tribromomethane by headspace thermal desorption-gas mass spectrometry. MethodsThe water sample was kept in the headspace bottle at 60 ℃ for 40 min， and the volatile matter was transferred to the cold trap，subjected to thermal desorption， then analyzed by gas chromatography-mass spectrometry. ResultsThe linear ranges were 0.2‒20.0 μg·L-1 for vinyl chloride， 0.1‒20.0 μg·L-1 for chloroform， 0.02‒20.00 μg·L-1 for tetrachloromethane， 0.2‒20.0 μg·L-1 for trichloroethylene， 0.3‒20.0 μg·L-1 for dichlorobromomethane， 0.1‒20.0 μg·L-1 for tetrachloroethylene， 0.4‒20.0 μg·L-1 for dichlorodibromomethane， and 1.0‒20.0 μg·L-1 for tribromomethane. All the correlation coefficients were more than 0.997. The respective quantitative limits were 0.162， 0.073， 0.016， 0.184， 0.270， 0.071， 0.356 and 0.813 μg·L-1， and the respective recoveries were 98.0%‒101.0%， 102.0%‒110.0%， 99.2%‒101.0%， 95.5%‒96.2%， 96.0%‒102.0%， 100.0%‒102.0%， 99.0%‒105.0%， and 94.0%‒103.0%. ConclusionThe method is simple， sensitive， rapid， accurate and reliable， so it is applicable for the determination of 8 kinds of volatile halogenated hydrocarbons in drinking water.
ABSTRACT
Background Organic ultraviolet (UV) filters are widely used in personal care products. So far, relevant studies on organic UV filters in indoor dust have been reported. Objective This study aims to establish a thermal desorption combined with gas chromatography-mass spectrometry (TD-GCMS) method to identify organic UV filters in indoor air collected from different indoor environments, so as to reveal the pollution levels and characteristics of organic UV filters in indoor environment. Methods Based on the standard indoor air sampling protocol, a total of 60 samples were collected from eight different kinds of indoor environments (male and female dormitory rooms, offices, labs, barber shops, printing shops, hotels, and private cars) on and nearby Minhang Campus of Shanghai Jiao Tong University from August to November, 2020. The concentrations of six common organic UV filters, including homosalate (HMS), 2-ethylhexyl salicylate (EHS), 3-(4-methylbenzylidene)-camphor (4-MBC), isoamyl 4-methoxycinnamate (IMC), octocrylene (OC), and octyl 4-methoxycinnamate (EHMC), in the air of different indoor environments were detected by TD-GCMS. Furthermore, the correlations of individual organic UV filters in different indoor environments were analysed. Results Under optimized detection conditions, the correlation coefficients of the quantitative standard curves of selected six organic UV filters were all at or above 0.997. The relative standard deviations of 1 mg·L−3 samples ranged from 1.74% to 7.11%, and the recoveries ranged from 67.17% to 106.5%. The relative standard deviations of 10 mg·L−3 samples ranged from 3.59% to 8.76%, and the recoveries ranged from 78.80% to 126.60%. The detection rates of the other five organic UV filters except IMC were all at or more than 92% in eight different kinds of indoor air. The median concentration of total organic UV filters was 75.17 ng·m−3, and EHS presented the highest median concentration of 28.55 ng·m−3. Regarding different indoor environments, the highest concentration of total organic UV filters was found in the female dormitory samples, 154.98 ng·m−3. The respective pair-analysis among HMS, EHMC, OC, and EHS of all indoor air samples reached a significant level of correlation (r=0.40-0.61, P<0.01). Conclusion The TD-GCMS method is satisfactory for the determination of organic UV filters in indoor air. EHS, EHMC, HMS, OC, and 4-MBC are identified in selected eight indoor environments, and they may have similar sources of pollution.
ABSTRACT
A thermal desorption low temperature plasma (TD-LTP) ionization was developed for rapid and sensitive detection of pesticides by direct mass spectrometry.The thermal desorption sampler was added in fount of the plasma generator.The sample was desorbed in the thermal desorption sampler firstly,and then the gas molecules were transported to the plasma generator by the carrier gas to be ionized.The utilization of thermal desorption sampler helps to shift the interaction of the gas phase plasma with the sample form gas-solid or gas-liquid to gas-gas,which increases the sensitivity and stability especially for non-volatile sample (e.g.pesticides) greatly compared with the traditional LTP ionization source.Under the optimal parameters of the thermal desorption LTP ionization source,the characteristic ions of 12 kinds of pesticides were investigated.Then the thermal desorption LTP ionization source was connected with the commercial ACQUITY TQD mass spectrometer to evaluate the pesticide residue level in broomcorn.
ABSTRACT
A polyimide coated stir bar for sorptive extraction (SBSE) was prepared by immersion precipitation method, and evaluated by using 5 phenols and chlorinated phenols as model samples. The extraction efficiency of the prepared stir bar was the highest compared with commercial extraction phases of SBSE. Experimental parameters including stir speed, ionic strength, extraction temperature, extraction time, desorption temperature and time were optimized. Under the optimal conditions such as 100 mL of sample, 30 g of NaCl, extraction time of 30 min, stirring speed of 800 r/ min and at 25℃, the target compounds were recovered by thermal desorption at 300℃ for 4 min, more than two orders of magnitude of linearity was obtained (R≥0. 9995), LOQs (S/ N=10) were 0. 028-0. 123 μg/ L, and RSDs were in the range of 1. 6% -9. 7% . The polyimide SBSE coupled with gas chromatography-mass spectrometry was applied to the extraction/ enrichment and analysis of phenols in real samples, including tap water, sea water, and waste water. It was found that the polyimide SBSE showed high selectivity towards polar compounds and high thermostability up to 350℃.
ABSTRACT
Theδ13 C values of volatile organic compounds ( VOCs) in various emission sources and ambient air were analyzed by using thermal desorption coupled with gas chromatography and isotope ratio mass. The lowest sample concentration and peak shape quality needed for high precision and accurate analysis were investigated. Fuel evaporation ( gasoline and diesel) , vehicle exhaust, solvent evaporation, dining fumes and ambient air of different functional zones of Xiamen city were collected using Tenax TA tube, and the significant differences in δ13 C values of VOCs between these sources were observed. The δ13 C value of gasoline exhaust ( 97 # ) was heavier (-25 . 84‰) than that of dining fumes (-30 . 26‰) and theδ13 C values of fuel evaporation were heavier than that of vehicle exhaust after combustion. The average δ13 C value of atmospheric VOCs in Xiamen was at the level of -27 . 03‰ to -25 . 40‰, which was close to the δ13 C value of the evaporation and exhaust of gasoline and diesel, indicating that the VOCs in the atmosphere of Xiamen was highly influenced by transportation related sources.
ABSTRACT
A thermal desorption ( TD) device was developed and coupled to gas chromatography ( GC) or gas chromatography-mass spectrometry ( GC-MS ) for the qualitative and quantitative analysis of semi-volatile organic compounds on atmospheric particulate matters ( PM ) . The TD was operated by direct heating and placed on the GC injector, leading to high heating rate and easy transfer of analytes to GC without focusing of analytes by cold trap. For establishing the TD-GC method, the materials used for supporting PM samples, temperature and time of thermal desorption, and types of sample injection were investigated for detection of sixteen polycyclic aromatic hydrocarbons ( PAHs) and nine n-alkanes. The limits of detection of the proposed TD-GC method were in the range of 0. 014-0. 093 ng for PAHs, and 0. 016-0. 026 ng for n-alkanes, respectively, with the correlation coefficients of correlation above 0. 9975. The TD-GC method was applied to the determination of trace PAHs and n-alkanes on PM10 samples from three cities. The recoveries were in the range of 95%-135% ( PAHs) and 95%-115% ( n-alkanes) , respectively. Finally, the TD was coupled to GC-MS for comparison of the contents of PAHs and n-alkanes on PMx with different particulate size ( x=10 , 5, 2, 1, 0. 5, 0. 25, 0. 1).
ABSTRACT
The chemical components of mainstream smoke were trapped by the artifical salvia. A novel method) for the analysis of the trapped chemical components was established using stir bar sorptive extraction(SBSE)) followed by a thermal desorption-gas chromatography-mass spectrometry(TD-GC-MS). The major) factors including desorption temperature, desorption time, cryofocusing temperature, extraction time and the addition of sodium chloride were studied. Under the optimized conditions, the average relative standard deviation(RSD) of peak areas of 44 components which were identified from the artifical saliva for 6 determinations was less than 10%, which showed the good repeatability of this method. The experiment result indicated that the SBSE-TD-GC-MS technique provided a powerful tool for the analysis of smoke components of some cigarette) trapped and dissolved in the saliva.
ABSTRACT
A method was developed for the determination of 54 volatile hydrocarbons in workplace air by thermal desorption/gas chromatography-hydrogen flame ionization detector. The workplace air was adsorbed by Tenax-TA thermal desorption tubes, then desorbed by thermal desorption and detected by gas chromatography. The experimental results indicated that the coefficients efficiency of 1,1-dichloroethylene, dichloromethane, trans-1,2-dichloroethylene, cis-1,2-dichloroethylene, 2,2-dichloropropane, bromochloromethane, 1,1,1-trichloroethane, 1,2-dichloroethane, 1,1-dichloropropene were 0.9941-0.9986. The detection limits of bromochloromethane, dibromomethane, trichloromethane, bromodichloromethane, 2,2-dichloropropane, dibromochloromethane, bromoform were 5.4-10.3 ng, the minimum detectable concentration was 0.01-0.1 mg/m~3 (the air volume=0.5 L). The coefficients efficiency of other 38 volatile hydrocarbons was above 0.999, the minimum detectable concentration were 0.001-0.01 mg/m~3. The detection limits of alkenes were 0.4-2.7 ng, alkanes 1.4-3.7 ng, aromatic hydrocarbons 0.2-1.0 ng and naphthalene 2.2 ng. The desorption efficiencies of 54 volatile hydrocarbons were 92.1%-113.1% and the relative standard deviations(RSDs) were 0.6%-17.4%. Except for the RSD values of cis-1,2-dichloroethylene, 1,1-dichloroethane, 1,1,1-trichloroethane, 1,1-dichloroethylene, 2,2-dichloropropane, trichloromethane, trans-1,2-dichloroethylene, dichloromethane, bromochloromethane were 5.1%-17.4%, those of other volatile hydrocarbons were below 5%;The experimental results indicated that the breakthrough capacities of 9 volatile hydrocarbons were 400-4000 ng, those of the other volatile hydrocarbons were above 10 μg. Except for the loss rates of 2,2-dichloropropane, bromodichloromethane were 10%-15% in stable experiment, those of other volatile hydrocarbons in Tenax desorption tubes were below 5%, which indicated that 54 volatile hydrocarbons stored in Tenax tubes were stable. The method is a quick and accurate for the detection of volatile hydrocarbons in workplace air.