Achieve Streamlined VOC Analysis in Ambient Air

Application Note Semiconductor and Environmental Authors Youjuan Zhang and Yu-tian Xu Agilent Technologies (Shanghai) Co. Ltd. Jun Lu Markes International Shanghai, China Abstract This application note introduces the use of a canister for gas sampling. Samples were introduced into an Agilent 8890 gas chromatograph (GC) with an Agilent 5977 single quadrupole mass selective detector (MSD) and the Markes Multi-Gas thermal desorption (TD), to analyze volatile organic compounds (VOCs) in the atmosphere or in semiconductor cleanrooms. The results of linearity, reproducibility, and detection limit fully met the requirements of the China method HJ759-2023. This method is widely used as a reference both in environmental laboratories and semiconductor cleanrooms. The linear correlation coefficient for all 65 compounds was greater than 0.991, with 86% of compounds having a value greater than 0.999. The results of reproducibility in scan mode varied between 0.3 to 6.8%, while results in SIM mode varied between 1.1 to 6.7%. The sampling volume was 300 mL, which resulted in detection limits of 0.013 to 0.113 nmol/mol for scan mode and 0.002 to 0.013 nmol/mol for SIM mode. Analysis of 65 Volatile Organic Compounds in Ambient Air by Canister Sampling Using an Agilent 8890/5977 GC/MSD A method using both scan and SIM mode that fully meets the requirements in the HJ 759-2023 standard 2 Introduction VOCs are a common type of organic pollutant that are highly irritating and harmful, with a significant impact on the environment. The composition of VOCs in the atmospheric environment is complex and they are crucial contributors to the formation of photochemical smog in the air. The study of VOCs has become a focus both domestically and internationally, with many countries issuing a series of regulations for the monitoring of air quality. In China, Europe, America, and other places, the detection of VOCs in the environment is not only a key project for city, regional, or national environmental monitoring stations, but also for certain manufacturing enterprises. These manufacturers, such as wafer factories, require strict control of VOCs in cleanrooms. Currently, with the rapid development of semiconductor technology and chip production entering the nanometer scale, the corresponding requirements for the production environment are becoming successively greater. The control of molecular-level air pollutants in cleanroom environments is becoming increasingly urgent, and VOCs are one of the molecular-level air pollutants that need to be strictly controlled. The main sources of VOCs in cleanrooms include interior decoration materials, equipment materials, cleaning agents, outdoor air, etc.1 VOC pollutants in the ambient air can cause contamination on the surface of semiconductor wafers, corrosion of connecting wires, and other problems that endanger product quality. Therefore, VOC pollutants have become a major factor affecting industrial development of wafers and their yield rate. In the analysis of VOCs in ambient air, thermal desorption gas chromatography/mass spectrometry (TD-GC/MSD) is mostly used for detection both in environmental monitoring labs and semiconductor industry cleanrooms. There are two common ways to collect samples. One type of sampling involves the use of an adsorption tube for sample collection and preconcentration, followed by analysis through a TD-GC/MSD system. The HJ 734-20142 method specifies the use of adsorption tubes and TD-GC/MSD to detect 24 VOCs. Markes International has published an application note based on the HJ734 method, which shows excellent performance results using adsorption tube sampling method.3 An alternative method employs a pre-evacuated canister for sample collection, with low-temperature condensation used for preconcentration. The HJ759-20234 standard provides a detailed description of a method using a canister for sampling and determining 65 VOCs in ambient air. This study adopts the HJ759-2023 method as a reference, using canister sampling for the qualitative and quantitative analysis of 65 VOCs. Excellent linearity, high precision, and excellent reproducibility results were demonstrated, which shows the inertness of the full flow path, high sensitivity, and durability of the whole TD-GC/MSD system. Experimental This study was performed on an 8890 GC coupled to a 5977 single quadrupole GC/MSD with an electron ionization (EI) source. A Markes Multi-Gas thermal desorption sample introduction and preconcentration system was used and included three modules: – CIA Advantage-xr (CIA): canister autosampler – Kori-xr: water removal module – Unity-xr: thermal desorption instrument First, three internal standards (ISTDs) were introduced into the Unity trap by CIA. Then, the sample was passed through a heated transfer line through the CIA Advantage into the Kori for water removal. Finally, the sample flowed into the focusing cold trap of the Unity for preconcentration. Eventually, the Unity trap was desorbed at high temperature, and the 65 VOCs and three ISTDs all entered the GC/MSD for analysis. Figure 1 shows the flow path of the combined system. Tables 1 and 2 illustrate the instrument conditions and consumables used in the system. Figure 1. Schematic illustration of the flow path of a Markes TD and an Agilent 8890/5977 GC/MSD system. TD system GC system Split tube Agilent 8890 GC Agilent DB-624UI, 60 m × 0.25 mm, 1.4 μm Standard ISTD gas Kori trap Unity trap Agilent 5977 MSD Stream selection 3 In this study, gas standards were purchased from Zhongce Standards Technology Co., Ltd. (Chengdu, China). One cylinder contained a mixed standard of 65 VOCs, each with a concentration approximating 1 µmol/mol. The other cylinder contained four compounds, three of which were ISTDs (bromochloromethane: ISTD 1; 1,4-difluorobenzene: ISTD 2; and chlorobenzene-d5 : ISTD 3); the fourth compound was 4-bromofluorobenzene (BFB). All had concentrations of approximately 1 µmol/mol. BFB was required for injection during the tuning evaluation to learn if the entire system, particularly the mass spectrometer, was operating at optimal conditions. These two standard gas cylinders both used nitrogen as the balance gas. Preparation of 65 VOCs standard gas Before establishing the calibration curve, the 1 µmol/mol standard gas had to be diluted to 0.5, 5, and 20 nmol/mol, respectively, and stored in canisters. According to the requirements of the HJ 759 method, to simulate real samples as much as possible, the standard gas also needed to be humidified. The relative humidity of the standard gas in canisters after final dilution was 50%. Therefore, after cleaning canisters, a certain amount of deionized water was added to the canisters according to the humidification method in Appendix B of HJ 759. Then, through a static dilution system using high-purity nitrogen (99.999% purity) as the dilution gas, the 1 µmol/mol standard gas was diluted to the target concentration levels. As shown in Tables 3 and 4, in scan mode, the target concentrations were 5 and 20 nmol/mol, respectively. In SIM mode, the target concentrations were 0.5 and 5 nmol/mol, respectively. Then different volumes were pumped in by the CIA to obtain calibration levels with different concentrations. Scan 5 nmol/mol 20 nmol/mol Sample Volume (mL) 30 60 150 60 150 300 Calibration Levels (nmol/mol) 0.5 1 2.5 4 10 20 Table 3. Preparation of calibration mixture of 65 VOCs for scan mode. SIM 0.5 nmol/mol 5 nmol/mol Sample Volume (mL) 60 150 300 60 150 300 Calibration Levels (nmol/mol) 0.1 0.25 0.5 1 2.5 5 Table 4. Preparation of calibration mixture of 65 VOCs for SIM mode. Table 1. TD parameters. Parameter Value Instrument Multi-Gas UNITY-xr, Multi-Gas CIA Advantage xr, Kori-xr Cold Trap Markes HJ 759 (p/n U-HJ759-KXR) General Flow Path Temperature 120 °C Sampling Line Temperature 120 °C Presampling Sample Purge Time 0.1 min Sample Purge Flow 50 mL/min Internal Standard Volume 30 mL Sampling Sample Volume 30 to 300 mL Sampling Flow 20, 50 mL/min Post Sampling Purge Post Sampling Purge Time 4 min Post Sampling Purge Flow 50 mL/min CIA Post Sampling Purge Flow 50 mL/min Kori Settings Kori Trap Low –30 °C Kori Trap High 300 °C Trap Settings Trap Purge Time 1 min Elevated Trap Purge Temperature 10 °C Trap Purge Flow 50 mL/min Trap Low Temperature –25 °C Trap High Temperature 250 °C Trap Desorption Time 3 min Desorb Split Flow 2 mL/min Table 2. GC conditions. Parameter Value Agilent 8890 GC Column Agilent DB-624 UI, 60 m × 0.25 mm, 1.4 μm (p/n 122-1364 UI) Carrier Gas Helium, constant flow, 1 mL/min Oven Program 35 °C (5 min), 5 °C/min to 150 °C (7 min), 10 °C/min to 200 °C (4 min) Agilent 5977 MSD Ion Source Temperature 230 °C Quad Temperature 150 °C Tune File Atune.u Acquisition Type Scan/SIM, m/z scan range 35 to 500 Gain Factor 1 Drawout Plate 6 mm 4 Preparation of ISTD gas The 1 µmol/mol ISTD was directly diluted to 50 nmol/mol with high purity nitrogen. The sample volume pumped into the system was 300 mL, as detailed in the HJ 759 method. By pumping 30 mL into the system through the CIA, the corresponding concentration of the internal standards distributed in a 300 mL sample was 5 nmol/mol. The HJ 759 method requires the use of canisters for sample collection. Some of the 65 VOCs have high polarity and were easily adsorbed; it was therefore necessary to use passivated canisters. Moreover, the canisters had to rigorously be cleaned before use to reduce their own adsorption of polar or high-boiling point compounds. It is suggested to prepare a canister filled with high purity nitrogen. Before each batch of samples is run, a blank check of the canister and the system should be carried out. Results and discussion TD parameter optimization To simulate the humidity of real samples, the standard gas was also subjected to 50% humidification treatment during preparation. The UNITY-CIA Advantage-xr Kori-xr instrument employs Dry Focus3 for effective management of humidity from gas phase samples, ensuring robust results, extending the life of the GC column and prolonging source cleaning of the MSD. Dry Focus3 is a fully automated three-stage process for drying, focusing, and injecting humid samples. Figure 2 shows the three-stage process. Step 2 takes advantage of a temperature-programmed purge of the cold trap to eliminate residual water retained by the strong sorbents required for HJ 759. Even small amounts of residual water can affect the Figure 2. The schematic shows the whole process of Dry Focus3. Step 1 – Sampling The sample passes through a drying trap to selectively remove water before concentration of the analytes on the focusing trap. Step 2 – Trap purge A temperature-programmed purge of the focusing trap allows elimination of residual water while retaining all trapped analytes. Step 3 – Desorption The focusing trap heats rapidly in a reversed flow of carrier gas to inject analytes into the GC column. At the same time, the drying trap is regenerated for the next sample. Kori-xr trap Focusing trap Carrier gas To vent To GC Sample 5 ionization efficiency of the mass spectrometer, impacting target compounds that coelute with water to the greatest degree. In this study, analyte trapping at –25 °C ensured sensitive detection of target compounds while an elevated temperature purge was optimized to eliminate residual water. The higher the purge temperature and the longer the time, the sooner the more volatile targets will begin to breakthrough to be lost from the Unity trap. If the purge temperature is too low or the time is too short, effective water removal is not achieved. Optimized elevated temperature purge conditions of 10 °C and 50 mL/min purge flow for 1 minute are shown in Figures 3 and 4; this balances retention of the most volatile target analytes with efficient water removal. Figure 3. Comparison of chromatograms in scan mode (scan from m/z 35) with and without "enable elevated trap purge temperature" function. For the water check, scan from m/z 12. 1,3-Butadiene Chloroethene Without elevated trap purge temperature Elevated trap purge temperature at 10 °C for 1 minute Acquisition time (min) 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 Significant reduction in water reaching the mass spectrometer with optimized Dry Focus3 conditions. m/z 18 5.2 5.4 5.6 5.8 6.0 6.2 6.4 Figure 4. Enable the "elevated trap purge temperature" function in TD software. 6 Scan mode results Scan mode is used for combined qualitative analysis of unknown compounds along with targeted quantitative analysis. With the library search function, the mass spectrum of the unknown peak can be compared with the standard mass spectrum in the library, providing preliminary qualitative results. Figure 5 is the total ion chromatogram (TIC) of 2.5 nmol/mol standard gas obtained under the full scan mode for 65 VOCs. All compound peaks are sharp and symmetrical. For some polar compounds, such as 1,4-dioxane and isopropanol, the peak shape remains outstanding even when the relative humidity of the sample is 50%. Most compounds have achieved baseline separation, while a small number of the compounds are coeluted. Because different quantitative ions can be selected during quantification, it does not affect accurate qualitative and quantitative analysis. In Figure 5, in addition to the 65 VOCs and three ISTDs, there is also a BFB peak. This is because BFB was prepared with three internal standard substances in a standard gas cylinder, so the peak of BFB can be seen in scan mode. In contrast, in SIM mode, only the ions of the target substance and the ISTD substance were collected, so the BFB peak could not be found in the TIC in SIM mode (Figure 7). The calibration curves were developed based on the ISTD method for six concentration levels from 0.5 to 20 nmol/mol. The 6 mm drawout plate was used for the best linearity for all compounds. For each component at every level of calibration, an average relative response factor (RRF) was determined with the ISTD method. The RRF for the percent relative standard deviation (%RSD) was less than 28% for all substances analyzed. In relation to linear curve fitting, the correlation coefficient (R2 ) was found to be at least 0.994 for each component, as shown in Table 5. Repeatability was assessed by calculating the relative standard deviation (RSD) of the area from eight replicate runs at 0.5 nmol/mol (low), 2.5 nmol/mol (middle), and 10 nmol/mol (high) concentration levels (Figure 6). Table 5 shows the overall area %RSD was 0.3 to 6.8 %. For middle and high concentration levels, the area %RSD of most compounds was less than 3%. For low concentration, due to the smaller peak area, the RSD would be slightly larger, with the %RSD of most compounds ranging between 3 to 4%. In this study, the method detection limit (MDL) was established by conducting eight replicated tests using a 0.5 nmol/mol standard gas. The concentration of each compound was calculated using a linear equation, followed by the calculation of the standard deviation and multiplication by 3 to determine the MDL. The study showed that the calculated detection limits for 65 VOCs ranged from 0.013 to 0.113 nmol/mol, as shown in Table 5. Figure 5. Total ion chromatogram of 65 VOCs at the concentration of 2.5 nmol/mol in scan mode ×105 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 1 2 3 4 5 6 7 8 9 10 11,12 13 14,15 16 17,18 19 20 21 22,23 24 25,26 27 28 29 30,31 32 33 34 35 37 36 38 39 40 41 42 43 44 45 46 47 48 49 50,51 52,53 54 55 56 57 58 59 60 61 62 63 64 65 BFB ISTD3 ISTD2 ISTD1 7 Table 5. Linearity, repeatability, and MDL results for 65 VOCs in scan mode (continued on the next page). No. Name RT m/z RRF %RSD CF R2 Area %RSD MDL Low Mid High (nmol/mol) ISTD 1 Propene 4.813 41 5.7 0.9984 1.9 1.5 1 0.039 1 2 Dichlorodifluoromethane 4.929 85 3.1 0.9996 2.9 0.9 1 0.032 1 3 1,1,2,2-Tetrafluoro-1,2-dichloroethane 5.36 134.9 3.3 0.9993 2.7 1.2 1 0.041 1 4 Chloromethane 5.515 50 8.1 0.9956 6.3 2.5 1 0.113 1 5 Chloroethene 5.921 62 3.4 0.9996 2.7 0.8 1 0.040 1 6 1,3-Butadiene 6.045 54 4.3 0.9997 5.1 1.9 1 0.072 1 7 Bromomethane 7.00 94 7.2 0.9941 5.1 0.8 1 0.069 1 8 Chloroethane 7.331 64 3.6 0.9997 4.4 1.7 1 0.056 1 9 Trichlorofluoromethane 8.134 101 3.6 0.9995 2.3 0.3 1 0.039 1 10 Acrolein 9.325 56.1 8.6 0.9997 6.6 2 1 0.067 1 11 1,1-Dichloroethylene 9.63 96 5.0 0.9997 3.6 1.4 1 0.050 1 12 1,2,2-Trifluoro-1,1,2-trichloroethane 9.671 150.9 2.8 0.9995 2.9 1.3 1 0.047 1 13 Acetone 9.762 58 2.2 0.9999 4.1 1.5 1 0.064 1 14 Isopropyl alcohol 10.187 45 7.5 0.9988 4.6 1.3 1 0.056 1 15 Carbon disulfide 10.236 76 3.1 0.9997 2 0.8 1 0.023 1 16 Dichloromethane 10.937 84 3.8 0.9996 3.4 1.6 1 0.041 1 17 trans-1,2-Dichloroethylene 11.693 96 4.3 0.9996 5.1 1.6 1 0.072 1 18 Methyl tert-butyl ether 11.73 73 9.0 0.9997 3.1 1.6 1 0.033 1 19 n-Hexane 12.435 57 6.1 0.9997 2.8 1.4 1 0.033 1 20 1,1-Dichloroethane 12.766 63 3.9 0.9995 2 1.4 1 0.039 1 21 Vinyl acetate 12.9 43 13.2 0.9996 4.3 1.3 1 0.044 1 22 cis-1,2-Dichloroethylene 14.246 96 4.1 0.9997 2 1.3 1 0.027 1 23 2-Butanone 14.272 72 8.6 0.9997 6.8 1.3 1 0.068 1 24 Ethyl Acetate 14.433 43 10.1 0.9998 5.3 2 1 0.059 1 25 Trichloromethane 15.02 83 4.5 0.9998 1.7 0.7 2 0.041 2 26 Tetrahydrofuran 15.038 72 12.3 0.9997 5.8 1.3 1 0.058 1 27 1,1,1-Trichloroethane 15.548 97 3.1 0.9998 3.3 0.7 2 0.048 2 28 Cyclohexane 15.721 84 5.9 0.9997 2.8 1.9 2 0.027 2 29 Carbon Tetrachloride 15.983 116.9 3.3 0.9997 3 1.1 2 0.031 2 30 1,2-Dichloroethane 16.471 62 4.4 0.9999 3.1 1.2 2 0.048 2 31 Benzene 16.471 78 5.3 0.9998 1.2 0.5 2 0.031 2 32 Heptane 17.117 43 6.8 0.9998 4.1 1.4 2 0.046 2 33 Trichloroethylene 18.081 130 5.9 0.9999 2.9 1.1 2 0.042 2 34 1,2-Dichloropropane 18.627 63 2.7 0.9999 3.3 1.7 2 0.039 2 35 Methyl methacrylate 18.888 100.1 17.4 0.9991 4.8 1.7 2 0.058 2 36 1,4-Dioxane 18.995 88 11.3 0.9951 3.5 2.3 2 0.058 2 37 Bromodichloromethane 19.296 83 4.0 0.9999 3.1 1.1 2 0.041 2 38 cis-1,3-Dichloropropene 20.459 75 6.7 0.9996 3 0.7 2 0.045 2 39 Dimethyl disulfide 20.709 94 17.2 0.9978 3.8 2.1 2 0.027 2 40 Methyl isobutyl ketone 20.839 43 8.6 0.9991 3.2 1.7 2 0.040 2 41 Toluene 21.376 91 4.4 0.9999 1.4 1.1 2 0.027 2 42 trans-1,3-Dichloropropene 21.882 75 8.5 0.9997 2.9 1.2 2 0.036 2 43 1,1,2-Trichloroethane 22.38 96.9 3.2 0.9997 1.7 1.1 2 0.032 2 44 Tetrachloroethylene 22.863 165.8 5.6 0.9997 1.6 0.8 2 0.046 2 45 2-Hexanone 23.042 43 12.4 0.9989 3.7 1.2 2 0.047 2 8 No. Name RT m/z RRF %RSD CF R2 Area %RSD MDL Low Mid High (nmol/mol) ISTD 46 Dibromochloromethane 23.467 128.8 4.5 0.9998 1.7 1 2 0.029 2 47 1,2-Dibromoethane 23.815 106.9 3.9 0.9999 2.6 1.8 2 0.041 2 48 Chlorobenzene 25.169 112 3.2 0.9999 1.4 1.2 3 0.019 3 49 Ethylbenzene 25.455 91 6.9 0.9998 2.5 0.8 3 0.020 3 50,51 m,p-Xylene 25.778 91 8.9 0.9998 2.4 0.8 3 0.013 3 52 o-Xylene 26.898 91.1 9.3 0.9998 3.1 0.8 3 0.027 3 53 Styrene 26.924 104 15.3 0.9997 3.4 0.4 3 0.027 3 54 Bromoform 27.449 173 6.2 0.9997 3.2 1.3 3 0.036 3 55 1,1,2,2-Tetrachloroethane 28.735 83 6.4 0.9997 3.3 1.1 3 0.034 3 56 p-Ethyltoluene 29.528 105.1 17.6 0.9996 1.8 1.7 3 0.016 3 57 1,3,5-Trimethylbenzene 29.729 105.1 19.6 0.9997 3.1 1.7 3 0.024 3 58 1,2,4-Trimethylbenzene 31.029 105 22.3 0.9996 4.7 1.3 3 0.029 3 59 1,3-Dichlorobenzene 32.115 146 8.4 0.9998 3.4 1 3 0.032 3 60 1,4-Dichlorobenzene 32.46 146 9.3 0.9998 3.8 0.9 3 0.032 3 61 Benzyl chloride 32.984 91 27.8 0.9988 3.2 1.4 3 0.024 3 62 1,2-Dichlorobenzene 34.065 145.9 10.3 0.9997 3.6 0.6 3 0.036 3 63 1,2,4-Trichlorobenzene 40.312 179.9 11.4 0.9992 4.7 2.6 3 0.054 3 64 Hexachlorobutadiene 40.908 224.8 11.3 0.9996 4.6 1.4 3 0.046 3 65 Naphthalene 41.101 128 22.4 0.9986 4.9 2.4 3 0.042 3 Area %RSD 0 2 4 6 8 10 12 14 Propene Dichlorodifluoromethane 1,1,2,2-Tetrafluoro-1,2-dichloroethane Chloromethane Chloroethene 1,3-Butadiene Bromomethane Chloroethane Trichlorofluoromethane Acrolein 1,1-Dichloroethylene 1,2,2-Trifluoro-1,1,2-trichloroethane Acetone Isopropyl alcohol Carbon disulfide Dichloromethane trans-1,2-Dichloroethylene Methyl tert-butyl ether n-Hexane 1,1-Dichloroethane Vinyl acetate cis-1,2-Dichloroethylene 2-Butanone Ethyl Acetate Trichloromethane Tetrahydrofuran 1,1,1-Trichloroethane Cyclohexane Carbon Tetrachloride 1,2-Dichloroethane Benzene Heptane Trichloroethylene 1,2-Dichloropropane Methyl methacrylate 1,4-Dioxane Bromodichloromethane cis-1,3-Dichloropropene Dimethyl disulfide Methyl isobutyl ketone Toluene trans-1,3-Dichloropropene 1,1,2-Trichloroethane Tetrachloroethylene 2-Hexanone Dibromochloromethane 1,2-Dibromoethane Chlorobenzene Ethylbenzene m,p-Xylene o-Xylene Styrene Bromofor m 1,1,2,2-Tetrachloroethane p-Ethyltoluene 1,3,5-Trimethylbenzene 1,2,4-Trimethylbenzene 1,3-Dichlorobenzene 1,4-Dichlorobenzene Benzyl chloride 1,2-Dichlorobenzene 1,2,4-Trichlorobenzene Hexachlorobutadiene Naphthalene 0.5 nmol/mol 2.5 nmol/mol 10 nmol/mol Figure 6. Repeatability results for 65 VOCs at low, middle, and high calibration levels in scan mode. 9 SIM mode results SIM mode uses a defined compound list to perform sensitive, targeted analysis. In SIM mode, it is necessary to group the target substances in advance and input the characteristic ions of each target substance to establish an acquisition method. Figure 7 is the TIC of the 1 nmol/mol standard gas collected under SIM mode. Because only the ions of interest are collected, only the chromatographic peaks of the target substances appear on the chromatogram. Therefore, compared to scan mode, the data collected in SIM mode have fewer interference peaks, and the BFB peak cannot be seen. Similar to scan mode data, under SIM mode, all compound peaks are also sharp and symmetrical, demonstrating the excellent inertness of the entire TD/GC/MSD system and fast injection from TD to GC. In SIM mode, a comprehensive method evaluation was also performed. The linear range of SIM mode is from 0.1 to 5 nmol/mol, which is approximately 5x lower than the concentrations in scan mode. Within this linear range, the RRF %RSD was less than 22% for all substances analyzed. The correlation coefficient values of 84% of the compounds were greater than 0.999, while the remaining 16% of the compounds were all greater than 0.99, which fully meets the requirements detailed in method HJ759-2023. To verify the precision of the method and the stability of the instrument, the concentrations of 0.1 nmol/mol (low), 0.5 nmol/mol (middle), and 2.5 nmol/mol (high) standard gases were measured eight times. The peak area %RSD of all compounds was less than 7%, and the average %RSD value was 2.3%, as shown in Figure 8. The MDL was determined through eight replicate runs of a 0.1 nmol/mol standard gas. Under SIM mode, the MDL values of all compounds ranged from 0.002 to 0.013 nmol/mol, showing the ultrahigh sensitivity of this system. All the performance results are shown in Table 6. Figure 7. Total ion chromatogram of 65 VOCs at the concentration of 1 nmol/mol in SIM mode. ×104 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 1 2 3 4 5 6 7 8 9 10 11,12 13 14,15 16 17,18 19 20 21 22,23 24 25,26 27 28 29 30,31 32 33 34 35 37 36 38 39 40 41 4243 44 45 4647 48 49 50,51 52,53 54 55 56 57 58 59 60 61 62 63 64 65 ISTD3 ISTD2 ISTD1 0 1 2 3 4 5 6 7 8 9 10 Figure 8. Repeatability results for 65 VOCs at low, middle, and high calibration levels in SIM mode. Area %RSD 0 2 4 6 8 10 12 14 Propene Dichlorodifluoromethane 1,1,2,2-Tetrafluoro-1,2-dichloroethane Chloromethane Chloroethene 1,3-Butadiene Bromomethane Chloroethane Trichlorofluoromethane Acrolein 1,1-Dichloroethylene 1,2,2-Trifluoro-1,1,2-trichloroethane Acetone Isopropyl alcohol Carbon disulfide Dichloromethane trans-1,2-Dichloroethylene Methyl tert-butyl ether n-Hexane 1,1-Dichloroethane Vinyl acetate cis-1,2-Dichloroethylene 2-Butanone Ethyl Acetate Trichloromethane Tetrahydrofuran 1,1,1-Trichloroethane Cyclohexane Carbon Tetrachloride 1,2-Dichloroethane Benzene Heptane Trichloroethylene 1,2-Dichloropropane Methyl methacrylate 1,4-Dioxane Bromodichloromethane cis-1,3-Dichloropropene Dimethyl disulfide Methyl isobutyl ketone Toluene trans-1,3-Dichloropropene 1,1,2-Trichloroethane Tetrachloroethylene 2-Hexanone Dibromochloromethane 1,2-Dibromoethane Chlorobenzene Ethylbenzene m,p-Xylene o-Xylene Styrene Bromofor m 1,1,2,2-Tetrachloroethane p-Ethyltoluene 1,3,5-Trimethylbenzene 1,2,4-Trimethylbenzene 1,3-Dichlorobenzene 1,4-Dichlorobenzene Benzyl chloride 1,2-Dichlorobenzene 1,2,4-Trichlorobenzene Hexachlorobutadiene Naphthalene 0.1 nmol/mol 0.5 nmol/mol 2.5 nmol/mol Table 6. Linearity, repeatability, and MDL results for 65 VOCs in SIM mode (continued on the next page). No. Name RT RRF %RSD CF2 Area %RSD MDL Low Mid High (nmol/mol) ISTD 1 Propene 4.618 5.0 0.9999 1.9 2.4 2.4 0.004 1 2 Dichlorodifluoromethane 4.729 3.1 0.9999 1.6 1.8 1.9 0.002 1 3 1,1,2,2-Tetrafluoro-1,2-dichloroethane 5.171 2.5 0.9999 1.7 1.9 2.2 0.002 1 4 Chloromethane 5.46 16.0 0.9989 4.1 4.5 3.2 0.013 1 5 Chloroethene 5.725 2.8 0.9999 1.1 2.1 1.9 0.003 1 6 1,3-Butadiene 5.865 2.9 0.9998 2.1 2.1 2.6 0.004 1 7 Bromomethane 6.824 7.0 0.9998 1.9 6.7 1.6 0.004 1 8 Chloroethane 7.149 3.0 0.9998 3.4 2 2.3 0.007 1 9 Trichlorofluoromethane 7.947 3.0 0.9998 1.8 1.9 1.9 0.003 1 10 Acrolein 9.202 10.1 0.9998 3.1 1.7 3.1 0.012 1 11 1,1-Dichloroethylene 9.5 3.4 0.9999 2 2.2 2.7 0.003 1 12 1,2,2-Trifluoro-1,1,2-trichloroethane 9.532 2.9 0.9997 1.7 1.8 1.8 0.004 1 13 Acetone 9.654 21.6 0.9999 2.6 2.9 2.5 0.009 1 14 Isopropyl alcohol 10.081 9.3 0.9981 1.9 2.6 2.4 0.006 1 15 Carbon disulfide 10.105 5.8 0.9999 2 1.6 1.9 0.006 1 16 Dichloromethane 10.824 7.6 0.9998 1.1 1.5 1.9 0.004 1 17 trans-1,2-Dichloroethylene 11.597 3.5 0.9999 1.6 2 2.3 0.003 1 18 Methyl tert-butyl ether 11.648 5.5 0.9996 1.4 2 3.2 0.003 1 19 n-Hexane 12.35 18.5 0.9999 1.7 2.5 3.3 0.007 1 20 1,1-Dichloroethane 12.689 4.0 0.9996 1.5 1.9 2.1 0.002 1 21 Vinyl acetate 12.827 7.9 0.9996 3.4 2.5 3.6 0.008 1 22 cis-1,2-Dichloroethylene 14.177 4.0 0.9998 1.2 2.1 2.4 0.003 1 23 2-Butanone 14.221 5.1 0.9996 3.5 2.1 2.7 0.011 1 24 Ethyl Acetate 14.384 5.7 0.9997 1.6 1.9 2.5 0.005 1 25 Trichloromethane 14.966 3.4 0.9997 1.3 1.9 1.9 0.003 2 11 No. Name RT RRF %RSD CF2 Area %RSD MDL Low Mid High (nmol/mol) ISTD 26 Tetrahydrofuran 15.005 5.7 0.9996 2.2 2.7 2.7 0.007 1 27 1,1,1-Trichloroethane 15.495 2.5 0.9999 1.8 2.2 1.9 0.005 2 28 Cyclohexane 15.665 3.5 0.9999 2.1 2.6 3.1 0.004 2 29 Carbon Tetrachloride 15.932 2.7 0.9998 2 2.5 1.6 0.005 2 30 1,2-Dichloroethane 16.428 8.1 0.9998 2.5 1.9 2 0.007 2 31 Benzene 16.428 6.0 0.9996 2.2 2.4 2.2 0.005 2 32 Heptane 17.079 3.0 0.9997 2.1 2.6 3.3 0.003 2 33 Trichloroethylene 18.041 3.4 0.9998 1.4 2.2 2 0.003 2 34 1,2-Dichloropropane 18.594 3.9 0.9998 1.7 2.2 2.1 0.004 2 35 Methyl methacrylate 18.867 6.7 0.9986 2 2.5 2.9 0.003 2 36 1,4-Dioxane 18.981 15.3 0.9913 2.7 2.4 1.7 0.008 2 37 Bromodichloromethane 19.265 3.4 0.9999 1.7 2.2 1.6 0.004 2 38 cis-1,3-Dichloropropene 20.437 4.8 0.9998 1.9 2.4 2.6 0.002 2 39 Dimethyl disulfide 20.684 10.0 0.9980 2.3 2.7 2.9 0.003 2 40 Methyl isobutyl ketone 20.83 9.1 0.9992 2.4 3.1 2.1 0.004 2 41 Toluene 21.36 5.5 0.9999 2 2.2 2.5 0.004 2 42 trans-1,3-Dichloropropene 21.87 6.2 0.9998 2.3 2.5 2.5 0.005 2 43 1,1,2-Trichloroethane 22.362 4.5 0.9997 1.8 2.2 1.7 0.005 2 44 Tetrachloroethylene 22.851 4.6 0.9997 1.3 2 1.7 0.003 2 45 2-Hexanone 23.04 9.7 0.9993 3.1 3.1 2.1 0.007 2 46 Dibromochloromethane 23.45 4.1 0.9999 1.3 2 1.5 0.003 2 47 1,2-Dibromoethane 23.801 4.1 0.9999 1.4 2.3 1.8 0.003 2 48 Chlorobenzene 25.161 4.4 0.9998 1.2 2.5 2.1 0.003 3 49 Ethylbenzene 25.447 5.4 0.9998 2.5 2.7 2.6 0.005 3 50,51 m,p-Xylene 25.767 9.2 0.9997 2.8 2.7 2.3 0.004 3 52 o-Xylene 26.897 8.9 0.9996 2.8 2.8 2.6 0.005 3 53 Styrene 26.921 13.1 0.9992 2.9 2.7 2.3 0.004 3 54 Bromoform 27.445 5.2 0.9999 2 2.2 1.6 0.004 3 55 1,1,2,2-Tetrachloroethane 28.731 3.3 0.9999 1.6 2.2 1.7 0.003 3 56 p-Ethyltoluene 29.528 11.7 0.9987 2.9 2.5 2.7 0.004 3 57 1,3,5-Trimethylbenzene 29.73 14.4 0.9988 3 2.5 2.5 0.005 3 58 1,2,4-Trimethylbenzene 31.03 13.4 0.9978 2.5 2.6 2.8 0.004 3 59 1,3-Dichlorobenzene 32.113 6.6 0.9999 2.3 2.2 2.2 0.003 3 60 1,4-Dichlorobenzene 32.459 7.6 0.9999 3 2.1 2.4 0.005 3 61 Benzyl chloride 32.993 13.4 0.9978 2.7 2.8 2.6 0.004 3 62 1,2-Dichlorobenzene 34.07 5.9 0.9999 3.1 2.7 2.5 0.006 3 63 1,2,4-Trichlorobenzene 40.318 12.0 0.9992 5.1 3 3.1 0.013 3 64 Hexachlorobutadiene 40.912 7.4 0.9997 2.5 2.8 2.3 0.006 3 65 Naphthalene 41.107 16.5 0.9978 5.8 2.6 4 0.012 3 12 Figure 9. MDL results for 65 VOCs both in scan and SIM mode. 0 0.02 0.04 0.06 0.08 0.10 0.12 Propene Dichlorodifluoromethane 1,1,2,2-Tetrafluoro-1,2-dichloroethane Chloromethane Chloroethene 1,3-Butadiene Bromomethane Chloroethane Trichlorofluoromethane Acrolein 1,1-Dichloroethylene 1,2,2-Trifluoro-1,1,2-trichloroethane Acetone Isopropyl alcohol Carbon disulfide Dichloromethane trans-1,2-Dichloroethylene Methyl tert-butyl ether n-Hexane 1,1-Dichloroethane Vinyl acetate cis-1,2-Dichloroethylene 2-Butanone Ethyl Acetate Trichloromethane Tetrahydrofuran 1,1,1-Trichloroethane Cyclohexane Carbon Tetrachloride 1,2-Dichloroethane Benzene Heptane Trichloroethylene 1,2-Dichloropropane Methyl methacrylate 1,4-Dioxane Bromodichloromethane cis-1,3-Dichloropropene Dimethyl disulfide Methyl isobutyl ketone Toluene trans-1,3-Dichloropropene 1,1,2-Trichloroethane Tetrachloroethylene 2-Hexanone Dibromochloromethane 1,2-Dibromoethane Chlorobenzene Ethylbenzene m,p-Xylene o-Xylene Styrene Bromofor m 1,1,2,2-Tetrachloroethane p-Ethyltoluene 1,3,5-Trimethylbenzene 1,2,4-Trimethylbenzene 1,3-Dichlorobenzene 1,4-Dichlorobenzene Benzyl chloride 1,2-Dichlorobenzene 1,2,4-Trichlorobenzene Hexachlorobutadiene Naphthalene Scan SIM Figure 9 shows the MDL results calculated under both scan and SIM modes. Compared to scan mode, the sensitivity results of SIM mode have improved by approximately 10x, which is consistent with the expectation. Therefore, if an analysis involves quantifying known trace components, SIM is a good choice to enhance sensitivity. www.agilent.com DE-000635 This information is subject to change without notice. © Agilent Technologies, Inc. 2024 Printed in the USA, November 25, 2024 5994-7723EN Conclusion An Agilent 8890/5977 GC/MSD system, equipped with a Multi-Gas CIA Advantage-xr TD provides a robust analytical procedure for the analysis of 65 VOCs in ambient air. This system offers a highly efficient and highly sensitive solution for the simultaneous analysis of multiple VOCs in both atmospheric quality monitoring laboratories and semiconductor cleanrooms. Based on different application requirements, users can choose to collect data in scan or SIM mode, demonstrating the flexibility of Agilent instruments. Excellent analytical performance has been achieved based on this system both in scan and SIM mode, which fully meets the requirements detailed in method HJ 759-2023. References 1. GB/T25915.8-2021 Cleanrooms and Associated Controlled Environments Part 8: Classification of Air Cleanliness by Chemical Concentration (ACC). 2. HJ 734-2014 Stationary Source Emission – Determination of Volatile Organic Compounds–Sorbent Adsorption and Thermal Desorption Gas Chromatography Mass Spectrometry Method. 3. The Monitoring of Organic Waste Gas VOCs Emitted by Fixed Pollution Sources is Sampled With Adsorption Tubes and Analyzed by Thermal Desorption/Gas Chromatography-Mass Spectrometry Method, Which Complies with the Chinese Environmental Protection Standard HJ 734-2014. Agilent Technologies application note, publication number, 2021. 4. HJ 759-2023 Determination of 65 Volatile Organic Compounds–Collected in Canisters and Analyzed By Gas Chromatography/Mass Spectrometry.