蘇瑪罐采樣-氣相色譜-質譜法測定環境空氣中99種揮發性有機物

崔連喜，關玉春，王艷麗

(天津市生態環境監測中心，天津 300191)

揮發性有機物(Volatile Organic Compounds，VOCs)是指沸點在50～260 ℃之間，室溫下飽和蒸汽壓超過133.32 kPa，在常溫下以蒸汽形式存在于空氣中的一類有機物[1]。VOCs廣泛存在于環境空氣中對人體健康與環境均會造成很大影響，美國國家環保局(EPA)已將超過50種VOCs列入有毒大氣污染物名單。經研究發現，VOCs是臭氧與二次有機氣溶膠形成的重要前體物[2-3]，因此，對環境空氣中VOCs的監測尤為重要。

根據國內外相關文獻，比較常用的測定揮發性有機物的方法有活性炭吸附/氣相色譜法[4-6]、吸附管采樣-熱脫附/氣相色譜-質譜法[7-9]和罐采樣/氣相色譜-質譜法[10]。目前國內出臺了罐采樣-氣相色譜-質譜法測定環境空氣中揮發性有機物的標準方法(HJ759-2015)，但是測定物質相對較少，不能滿足當前研究需求。本文結合監測工作的實際情況，優化了該方法，并實際應用于某處環境空氣中揮發性有機物的10天連續測定，對研究揮發性有機物與臭氧的關系具有重要意義。

1 實 驗

1.1 儀器與試劑

Agilent 7890B/5977B型氣相色譜-質譜聯用儀；Entech 7200型蘇瑪罐預濃縮儀；Entech 3100A型清罐儀；Entech 7016D型自動進樣儀；Entech 4700型動態氣體稀釋儀；3.2 L蘇瑪罐；150 L液氮瓶。

混合標準氣體：PAMS標準氣體(57種)；EPA TO-14、-15標準氣體(65種)；內標氣(4種)；濃度均為1.00 mg/kg。

高純氦氣(純度大于99.999%)；高純氮氣(純度大于99.999%)；液氮(純度大于99.99%)。

1.2 儀器工作條件

1.2.1 預濃縮條件

(1)一級冷阱：捕集溫度：-40 ℃；捕集流速：100 mL·min-1；解析溫度：10 ℃；閥溫：100 ℃；烘烤溫度：150 ℃；

(2)二級冷阱：捕集溫度：-40 ℃；捕集流速：10 mL·min-1；捕集時間：5 min；解析溫度：30 ℃；解析時間：3 min；烘烤溫度：230 ℃；

(3)三級聚焦：聚焦溫度：-150 ℃；解析時間：3 min；烘烤溫度：150 ℃；

(4)傳輸線溫度：120 ℃；

(5)進樣體積：400 mL。

色譜條件：HP-1毛細管色譜柱(60 m×0.32 mm，1.0 μm)。色譜柱升溫程序：初始溫度35 ℃，保持5 min；以5 min-1速率升溫至150 ℃，保持7 min；以10 ℃·min-1速率升溫至200 ℃，保持4 min。氣化室溫度250 ℃；載氣流量1 mL·min-1；分流比20:1。

質譜條件：電子轟擊離子源(EI)，離子源溫度230 ℃；溶劑延遲時間3 min；數據采集時間3～44 min；全掃描模式，掃描范圍m/z 33～350。

1.3 實驗方法

1.3.1 采樣前準備

用Entech 3100A清罐儀對3.2 L蘇瑪罐進行抽真空，并用氮氣對蘇瑪罐進行三個循環的清洗，最后抽真空至5 Pa。

1.3.2 樣品采集與保存

樣品采集可采用瞬時采樣和恒定流量采樣兩種方式。

瞬時采樣：將清洗后并抽成真空的蘇瑪罐帶至采樣點，安裝過濾器后，打開采樣罐閥門，開始采樣(采樣時間為10～20 s)。待罐內壓力與采樣點大氣壓力一致后，關閉閥門，用密封帽密封。

恒定流量采樣：將清洗后并抽成真空的采樣罐，帶至采樣點，安裝流量控制器和過濾器后，打開采樣罐閥門，開始恒流采樣，在設定的恒定流量所對應的采樣時間達到后，關閉閥門，用密封帽密封。

樣品在常溫下保存，采樣后盡快分析，20天內分析完畢。

1.4 定性與定量方法

以保留時間定性，內標法定量。

2 結果與討論

2.1 色譜行為

99種混合標準氣體的總離子流色譜圖見圖1。

圖1 混合標準氣體的總離子流色譜圖Fig.1 TIC chromatogram of mixed standard gases

2.2 標準曲線與方法檢出限

用動態稀釋儀，將1.00 μmol·mol-1的57種PAMS標準氣體和65種TO-14、TO-15標準氣體用高純氮氣稀釋混合至10.0 nmol·mol-1的標準使用氣，另外，將1.00 μmol·mol-1的4種內標混合氣用高純氮氣稀釋至50.0 nmol·mol-1的內標使用氣，然后向預濃縮儀中分別引入20.0、50.0、100、150、200 mL標準氣體及每次20 mL的內標氣體。將400mL進樣體積作為基準的進樣體積，根據5次引入的標準氣體濃度推算出校準曲線各點的濃度分別為0.50、1.25、2.50、3.75、6.25 nmol·mol-1，4種內標物的濃度均為2.50 nmol·mol-1。在標準系列濃度范圍內99種揮發性有機物的相關系數為0.9952～0.9996。具體參數見表1。

連續測定7個接近于方法檢出限(MDL)的實驗室空白加標樣品，計算標準偏差s。按照HJ 168-2010附錄A.1方法檢出限規定的計算公式：MDL=st(n-1,0.99)(式中t值取3.143)計算該方法測定醛酮類化合物的檢出限，結果見表1。

表1 標準曲線與方法檢出限

續表1

2,3-二甲基丁烷8.2930.50～6.25y=1.556x-0.0790.99910.82-甲基戊烷8.4280.50～6.25y=1.834x-0.2640.99780.83-甲基戊烷8.9420.50～6.25y=1.529x-0.1270.99960.81-己烯9.1510.50～6.25y=0.804x-0.0650.99920.8正己烷?9.5751.00～12.5y=1.118x-0.1220.99900.32,4-二甲基戊烷10.8020.50～6.25y=1.444x-0.1060.99890.9甲基環戊烷10.6810.50～6.25y=1.568x-0.1270.99900.8苯11.6880.50～6.25y=5.179x-0.2690.99890.3環己烷12.0980.50～6.25y=2.363x-0.1650.99900.62-甲基己烷12.3880.50～6.25y=1.588x-0.0540.99910.92,3-二甲基戊烷12.4900.50～6.25y=1.419x-0.0580.99890.93-甲基己烷12.7720.50～6.25y=1.268x-0.0650.99900.92,2,4-三甲基戊烷13.3860.50～6.25y=3.918x-0.2280.99781正庚烷?13.8071.00～12.5y=1.239x+0.0050.99910.4甲基環己烷14.8070.50～6.25y=1.680x-0.0960.99810.92,3,4-三甲基戊烷16.0680.50～6.25y=2.007x-0.1810.997912-甲基庚烷16.6950.50～6.25y=1.835x-0.1390.99831甲苯?16.2731.00～12.5y=3.408x-0.3580.99890.53-甲基庚烷17.0240.50～6.25y=1.367x-0.0680.99861正辛烷18.1200.50～6.25y=1.819x-0.1350.99881乙苯?20.2631.00～12.5y=1.257x-0.0170.99870.6間、對-二甲苯?20.6042.00～25.0y=1.003x+0.2140.99940.6正壬烷22.1390.50～6.25y=0.521x-0.0150.99921苯乙烯?21.3161.00～12.5y=0.735x-0.0390.99840.6鄰二甲苯?21.5331.00～12.5y=1.019x+0.0280.99850.6異丙苯22.7900.50～6.25y=1.532x-0.0450.99901正丙苯23.9100.50～6.25y=1.705x-0.1240.999411-乙基-2-甲基苯24.1700.50～6.25y=1.500x-0.0350.999311-乙基-3-甲基苯24.2580.50～6.25y=2.853x+0.1500.998811,3,5-三甲苯?24.4511.00～12.5y=1.229x+0.1110.99891對乙基甲苯?24.8591.00～12.5y=0.732x-0.0350.99920.9癸烷25.8360.50～6.25y=0.683x+0.0240.998811,2,4-三甲苯?25.4011.00～12.5y=1.267x+0.0250.99910.71,2,3-三甲苯26.4290.50～6.25y=1.290x-0.0540.999211,3-二乙基苯27.3150.50～6.25y=0.942x-0.0620.99921對二乙苯27.5510.50～6.25y=0.995x-0.1590.99901十一烷29.3090.50～6.25y=0.809x-0.0470.99971十二烷33.5240.50～6.25y=0.836x-0.0460.99881二氟二氯甲烷4.0730.50～6.25y=0.572x+0.0010.99900.5一氯甲烷4.2550.50～6.25y=0.139x-0.0030.99740.31,1,2,2-四氟-1,2-二氯乙烷4.3700.50～6.25y=0.418x-0.0120.99880.6氯乙烯4.4860.50～6.25y=0.153x-0.0090.99940.3丁二烯4.6340.50～6.25y=0.097x-0.0010.99780.3一溴甲烷4.9260.50～6.25y=0.168x-0.0020.99780.5氯乙烷5.1240.50～6.25y=0.074x-0.0010.99830.9一氟三氯甲烷5.9450.50～6.25y=0.598x+0.0040.99860.71,1-二氯乙烯6.6660.50～6.25y=0.183x-0.0110.99770.51,2,2-三氟-1,1,2-三氯乙烷7.1350.50～6.25y=0.384x-0.0030.99870.7二硫化碳7.1400.50～6.25y=0.375x-0.0240.99790.4二氯甲烷6.8090.50～6.25y=0.165x-0.0030.99820.5異丙醇6.4070.50～6.25y=0.241x-0.0020.99930.6順1,2-二氯乙烯7.9360.50～6.25y=0.169x-0.0180.99690.5甲基叔丁基醚8.5530.50～6.25y=0.554x-0.0660.99800.51,1-二氯乙烷8.1910.50～6.25y=0.341x-0.0120.99860.7乙酸乙烯酯8.6460.50～6.25y=0.045x+0.0030.99880.5反1,2-二氯乙烯9.2630.50～6.25y=0.212x-0.0130.99840.8乙酸乙酯9.8360.50～6.25y=0.301x-0.0250.99670.6

續表1

三氯甲烷9.6450.50～6.25y=0.465x+0.0020.99850.5四氫呋喃10.4840.50～6.25y=0.152x-0.0120.99890.71,1,1-三氯乙烷11.0230.50～6.25y=0.521x-0.0020.99840.51,2-二氯乙烷10.6810.50～6.25y=0.291x+0.0040.99870.7四氯化碳11.8930.50～6.25y=0.568x-0.0070.99830.6三氯乙烯13.2750.50～6.25y=0.329x-0.0290.99760.61,2-二氯丙烷12.9170.50～6.25y=0.215x-0.0110.99850.6甲基丙烯酸甲酯13.7520.50～6.25y=0.315x-0.0130.99790.51,4-二氧六環13.5030.50～6.25y=0.166x+0.0040.99650.5一溴二氯甲烷13.1900.50～6.25y=0.780x-0.0230.99830.6順式-1,3-二氯-1-丙烯14.6530.50～6.25y=0.610x-0.0790.99520.64-甲基-2-戊酮14.9000.50～6.25y=0.634x-0.0500.99860.6反式-1,3-二氯-1-丙烯15.5280.50～6.25y=0.574x-0.0840.99710.51,1,2-三氯乙烷15.7930.50～6.25y=0.441x-0.0170.99830.52-己酮16.9300.50～6.25y=0.480x-0.0670.99690.9二溴一氯甲烷16.9490.50～6.25y=0.940x-0.0410.99810.7四氯乙烯18.2540.50～6.25y=0.777x-0.0430.998111,2-二溴乙烷17.3940.50～6.25y=0.703x-0.0400.99782氯苯19.5020.50～6.25y=1.129x-0.0530.99810.7三溴甲烷20.6500.50～6.25y=0.990x-0.0480.99780.9四氯乙烷21.5000.50～6.25y=0.960x+0.0230.998611,3-二氯苯25.6760.50～6.25y=1.303x+0.0080.99780.5氯代甲苯25.6690.50～6.25y=1.331x-0.1110.99830.7對二氯苯25.8570.50～6.25y=1.316x+0.0180.99860.7鄰二氯苯26.6970.50～6.25y=1.223x-0.0300.998721,2,4-三氯苯32.1830.50～6.25y=1.020x-0.1850.99651萘32.5800.50～6.25y=1.862x-0.3200.99630.71,1,2,3,4,4-六氯-1,3-丁二烯34.5620.50～6.25y=1.111x-0.0120.99772

注：*號物質為標準氣體重疊物質。

2.3 方法的精密度

對高、低2種不同濃度水平的VOCs混合氣體，分別進行6次測定，計算相對標準偏差(RSD)，結果見表2。

表2 精密度實驗結果

續表2

2-甲基1,3-丁二烯1.250.901.040.920.960.911.100.978.33.753.623.393.102.882.872.913.1310.0順-2-戊烯1.250.910.990.981.010.981.151.007.83.753.553.363.212.962.992.923.168.02,2-二甲基丁烷1.250.890.970.950.980.930.870.934.83.753.573.363.202.963.012.853.168.6環戊烷1.251.131.020.961.161.140.941.069.43.752.522.812.553.042.872.982.807.72,3-二甲基丁烷1.250.890.871.010.801.000.930.928.93.753.533.293.142.892.982.893.128.22-甲基戊烷1.250.850.980.961.000.940.880.936.23.753.483.333.172.902.973.013.147.23-甲基戊烷1.250.830.930.900.920.931.100.949.63.753.683.483.293.053.132.973.278.41-己烯1.250.880.970.960.980.931.140.988.83.753.603.333.192.932.972.903.158.7正己烷2.501.822.112.052.112.042.162.055.87.507.126.736.355.926.065.876.347.82,4-二甲基戊烷1.250.891.020.991.040.990.920.986.23.753.603.383.222.973.052.933.198.1甲基環戊烷1.250.890.990.971.010.940.890.955.13.753.563.333.162.943.002.893.158.3苯1.250.931.051.030.821.020.960.978.73.753.613.383.233.013.052.973.217.8環己烷1.250.941.010.981.011.110.920.996.93.753.583.353.172.963.042.953.187.82-甲基己烷1.250.851.010.991.020.970.930.966.43.753.363.133.042.792.902.803.007.32,3-二甲基戊烷1.250.901.071.060.931.040.991.007.23.753.483.273.122.912.992.943.127.13-甲基己烷1.250.830.961.180.980.941.131.0012.93.753.423.213.072.822.922.803.048.02,2,4-三甲基戊烷1.251.050.950.940.960.931.130.997.93.753.313.122.962.762.842.752.967.5正庚烷2.501.812.192.162.242.142.042.107.47.506.786.416.125.715.875.856.126.6甲基環己烷1.251.051.191.161.191.161.111.144.83.753.413.203.082.882.932.873.067.02,3,4-三甲基戊烷1.251.041.171.150.941.141.081.088.03.753.453.263.122.872.942.883.097.52-甲基庚烷1.251.021.171.151.181.161.101.135.33.753.413.193.082.862.942.893.066.9甲苯2.501.811.661.621.691.612.011.738.87.507.206.756.506.056.226.186.486.73-甲基庚烷1.250.831.011.001.000.980.930.967.33.753.313.153.012.842.922.893.025.9正辛烷1.251.011.151.121.151.131.071.114.93.753.413.223.092.882.972.913.086.6乙苯2.501.581.941.961.971.871.781.857.97.506.356.055.765.295.695.515.786.6間、對-二甲苯5.003.973.893.913.963.803.903.911.615.013.212.913.212.712.612.112.83.1正壬烷1.250.990.940.960.960.910.880.944.23.753.233.112.942.722.932.852.966.2苯乙烯2.501.911.992.012.031.911.831.953.87.506.336.025.735.285.675.435.746.7

續表2

鄰二甲苯2.501.701.691.721.741.611.551.674.47.506.556.255.995.525.955.866.025.8異丙苯1.251.051.231.241.000.951.151.1011.13.753.263.122.982.752.962.872.996.0正丙苯1.251.010.920.920.940.880.850.925.73.753.463.313.182.933.153.063.185.81-乙基-2-甲基苯1.251.030.960.980.991.190.891.019.83.753.293.152.962.773.012.923.026.01-乙基-3-甲基苯1.251.061.071.081.091.041.001.053.13.753.122.972.862.642.882.822.885.51,3,5-三甲苯2.501.581.611.631.652.031.971.7511.67.506.235.955.695.285.755.615.755.6對乙基甲苯2.501.521.941.951.981.882.041.899.97.506.526.255.965.535.975.816.015.7癸烷1.250.760.780.780.800.990.960.8512.13.753.042.912.792.592.832.772.825.31,2,4-三甲苯2.501.571.561.591.601.501.441.543.97.506.486.185.885.505.985.845.985.51,2,3-三甲苯1.251.000.950.960.970.930.890.954.03.753.383.253.102.873.133.043.135.61,3-二乙基苯1.250.720.930.930.950.890.860.889.53.753.423.283.142.903.153.093.165.6對二乙苯1.250.990.981.001.010.950.930.983.23.753.273.122.962.743.002.943.006.0十一烷1.250.830.960.760.780.970.930.8710.83.753.333.283.182.963.223.133.184.2十二烷1.250.900.860.870.881.091.050.9410.83.753.273.153.022.803.062.983.055.2二氟二氯甲烷1.250.980.981.011.010.930.880.975.23.753.483.323.222.963.193.123.215.4一氯甲烷1.251.130.920.931.130.871.051.0111.33.753.483.323.222.933.083.653.287.91,1,2,2-四氟-1,2-二氯乙烷1.251.000.981.001.010.940.880.975.13.753.613.453.343.043.273.183.326.0氯乙烯1.251.010.920.920.930.870.790.918.23.753.593.273.192.913.113.123.207.0丁二烯1.250.950.960.970.960.940.810.936.43.753.473.443.242.943.223.043.226.6一溴甲烷1.250.990.981.040.960.950.880.975.53.753.513.333.262.973.173.163.235.7氯乙烷1.250.921.021.001.000.940.870.965.93.753.503.343.312.993.263.173.265.3一氟三氯甲烷1.250.960.981.011.000.950.900.974.13.753.513.333.212.933.183.133.226.01,1-二氯乙烯1.250.940.810.810.831.000.950.899.53.753.593.383.202.963.052.933.198.21,2,2-三氟-1,1,2-三氯乙烷1.250.950.950.960.960.910.840.935.03.753.483.323.182.933.103.073.186.1二硫化碳1.250.950.870.890.860.840.750.867.73.753.503.403.232.923.153.023.206.9二氯甲烷1.250.970.960.980.990.920.880.954.33.553.333.202.933.153.013.197.0異丙醇1.250.901.001.030.990.920.880.956.53.753.473.383.222.903.052.863.158.0順1,2-二氯乙烯1.250.980.800.780.750.940.900.8610.83.753.753.543.392.983.162.973.309.6

續表2

甲基叔丁基醚1.250.930.750.781.030.970.910.8912.23.753.953.753.603.263.443.313.557.51,1-二氯乙烷1.250.970.900.920.930.880.810.906.13.753.623.453.312.993.203.113.287.0乙酸乙烯酯1.251.251.201.181.381.071.201.218.33.753.633.553.453.482.823.163.359.1反1,2-二氯乙烯1.250.940.810.840.830.780.980.869.03.753.633.413.272.973.113.033.237.8乙酸乙酯1.250.901.000.901.030.920.880.946.43.753.723.553.923.133.242.953.4210.8三氯甲烷1.250.950.960.980.990.940.870.954.43.753.463.313.212.963.163.093.205.4四氫呋喃1.250.920.900.920.911.111.050.979.33.754.183.993.773.303.493.343.689.81,1,1-三氯乙烷1.250.940.950.970.970.910.860.934.73.753.513.323.242.973.183.143.235.61,2-二氯乙烷1.250.900.930.940.930.860.830.904.73.753.333.193.122.843.053.073.105.3四氯化碳1.250.940.940.980.960.920.880.943.73.753.513.333.252.993.193.193.245.3三氯乙烯1.250.940.820.830.821.010.970.909.53.753.743.553.423.093.263.173.377.31,2-二氯丙烷1.250.980.890.900.900.851.040.937.43.753.673.473.323.043.203.113.307.2甲基丙烯酸甲酯1.250.941.010.770.780.940.910.8911.03.753.633.433.293.252.862.643.1811.51,4-二氧六環1.251.031.001.091.010.970.931.005.42.932.782.713.122.872.832.875.0一溴二氯甲烷1.250.950.860.870.860.821.010.897.83.753.403.293.142.833.032.853.097.4順式-1,3-二氯-1-丙烯1.250.821.081.081.091.010.971.0110.23.753.453.383.202.862.973.003.147.74-甲基-2-戊酮1.250.901.021.001.010.940.910.965.63.753.393.503.192.893.052.803.148.9反式-1,3-二氯-1-丙烯1.250.840.880.870.881.051.010.929.63.753.633.543.323.003.142.883.259.21,1,2-三氯乙烷1.250.960.840.840.831.040.990.9210.13.753.413.293.142.812.962.823.078.12-己酮1.251.040.920.910.940.850.820.918.33.753.823.693.493.133.273.093.418.8二溴一氯甲烷1.250.890.830.840.841.040.990.909.73.753.343.243.092.812.992.853.056.9四氯乙烯1.250.950.830.850.850.800.980.888.33.753.443.323.202.893.032.903.137.31,2-二溴乙烷1.250.911.021.031.031.230.911.0211.43.753.403.293.122.822.972.823.077.9氯苯1.250.930.820.830.830.780.970.868.53.753.363.253.132.823.012.823.077.4三溴甲烷1.250.831.021.041.040.990.950.988.23.753.243.153.012.762.932.822.986.3四氯乙烷1.250.860.810.830.831.030.980.8910.03.753.123.022.892.662.822.682.866.41,3-二氯苯1.250.860.830.840.830.790.990.868.03.753.233.163.042.772.962.863.005.8氯代甲苯1.250.820.991.001.010.940.890.947.93.753.533.443.313.023.223.083.276.1

續表2

對二氯苯1.250.890.840.860.860.801.000.877.53.753.193.092.992.752.932.832.975.5鄰二氯苯1.250.861.040.811.051.010.950.9510.83.753.323.253.112.873.042.923.095.81,2,4-三氯苯1.250.931.021.011.030.960.880.976.23.754.024.043.883.523.763.583.805.8萘1.250.941.081.081.091.040.951.036.63.753.663.603.433.143.303.133.386.71,1,2,3,4,4-六氯-1,3-丁二烯1.250.831.031.040.791.000.950.9411.43.753.143.052.952.692.872.782.915.8

由表2可知，低濃度等級下，RSD范圍為1.6%～12.9%；高濃度等級下，RSD范圍為3.1%～11.5%；其中多數組分的RSD小于10%。結果表明：方法的精密度良好。

2.4 樣品分析

在某監測點位按照樣品采集方法采集2018年9月4日-9月13日期間的樣品，數據以D1～10表示。采樣時段為0:00～3:00、3:00～6:00、6:00～9:00、9:00～12:00、12:00～15:00、15:00～18:00、18:00～21:00、21:00～24:00。采集后的樣品根據以上的分析條件及標準曲線，進行定性定量分析。經匯總，10天 VOCs的測定結果如圖2所示。

圖2 測定結果匯總圖Fig.1 The results of summary

由10天樣品數據結果及匯總圖表明：① 在此處環境空氣中，常見揮發性有機物為正丁烷、異戊烷、甲苯、對間二甲苯、二氟二氯甲烷、一氯甲烷、二氯甲烷等，比重占40%以上；② 在常見的幾種揮發性有機物中，甲苯、對間二甲苯、二氟二氯甲烷、一氯甲烷和二氯甲烷檢出率在95%以上；③ 濃度較高點出現在早高峰和晚高峰時段，可能與機動車排放有關，造成該結果的原因尚待進一步探索。

本工作采用蘇瑪罐采樣-氣相色譜-質譜法測定環境空氣中99種揮發性有機物，方法精密度高，檢出限低，檢測物質種類多，操作簡單。因此，本方法適用于環境空氣中揮發性有機物質的測定和臭氧前體物的研究。