苏玛罐采样-气相色谱-质谱法测定环境空气中99种挥发性有机物

崔连喜，关玉春，王艳丽

(天津市生态环境监测中心，天津 300191)

挥发性有机物(Volatile Organic Compounds，VOCs)是指沸点在50～260 ℃之间，室温下饱和蒸汽压超过133.32 kPa，在常温下以蒸汽形式存在于空气中的一类有机物[1]。VOCs广泛存在于环境空气中对人体健康与环境均会造成很大影响，美国国家环保局(EPA)已将超过50种VOCs列入有毒大气污染物名单。经研究发现，VOCs是臭氧与二次有机气溶胶形成的重要前体物[2-3]，因此，对环境空气中VOCs的监测尤为重要。

根据国内外相关文献，比较常用的测定挥发性有机物的方法有活性炭吸附/气相色谱法[4-6]、吸附管采样-热脱附/气相色谱-质谱法[7-9]和罐采样/气相色谱-质谱法[10]。目前国内出台了罐采样-气相色谱-质谱法测定环境空气中挥发性有机物的标准方法(HJ759-2015)，但是测定物质相对较少，不能满足当前研究需求。本文结合监测工作的实际情况，优化了该方法，并实际应用于某处环境空气中挥发性有机物的10天连续测定，对研究挥发性有机物与臭氧的关系具有重要意义。

1 实 验

1.1 仪器与试剂

Agilent 7890B/5977B型气相色谱-质谱联用仪；Entech 7200型苏玛罐预浓缩仪；Entech 3100A型清罐仪；Entech 7016D型自动进样仪；Entech 4700型动态气体稀释仪；3.2 L苏玛罐；150 L液氮瓶。

混合标准气体：PAMS标准气体(57种)；EPA TO-14、-15标准气体(65种)；内标气(4种)；浓度均为1.00 mg/kg。

高纯氦气(纯度大于99.999%)；高纯氮气(纯度大于99.999%)；液氮(纯度大于99.99%)。

1.2 仪器工作条件

1.2.1 预浓缩条件

(1)一级冷阱：捕集温度：-40 ℃；捕集流速：100 mL·min-1；解析温度：10 ℃；阀温：100 ℃；烘烤温度：150 ℃；

(2)二级冷阱：捕集温度：-40 ℃；捕集流速：10 mL·min-1；捕集时间：5 min；解析温度：30 ℃；解析时间：3 min；烘烤温度：230 ℃；

(3)三级聚焦：聚焦温度：-150 ℃；解析时间：3 min；烘烤温度：150 ℃；

(4)传输线温度：120 ℃；

(5)进样体积：400 mL。

色谱条件：HP-1毛细管色谱柱(60 m×0.32 mm，1.0 μm)。色谱柱升温程序：初始温度35 ℃，保持5 min；以5 min-1速率升温至150 ℃，保持7 min；以10 ℃·min-1速率升温至200 ℃，保持4 min。气化室温度250 ℃；载气流量1 mL·min-1；分流比20:1。

质谱条件：电子轰击离子源(EI)，离子源温度230 ℃；溶剂延迟时间3 min；数据采集时间3～44 min；全扫描模式，扫描范围m/z 33～350。

1.3 实验方法

1.3.1 采样前准备

用Entech 3100A清罐仪对3.2 L苏玛罐进行抽真空，并用氮气对苏玛罐进行三个循环的清洗，最后抽真空至5 Pa。

1.3.2 样品采集与保存

样品采集可采用瞬时采样和恒定流量采样两种方式。

瞬时采样：将清洗后并抽成真空的苏玛罐带至采样点，安装过滤器后，打开采样罐阀门，开始采样(采样时间为10～20 s)。待罐内压力与采样点大气压力一致后，关闭阀门，用密封帽密封。

恒定流量采样：将清洗后并抽成真空的采样罐，带至采样点，安装流量控制器和过滤器后，打开采样罐阀门，开始恒流采样，在设定的恒定流量所对应的采样时间达到后，关闭阀门，用密封帽密封。

样品在常温下保存，采样后尽快分析，20天内分析完毕。

1.4 定性与定量方法

以保留时间定性，内标法定量。

2 结果与讨论

2.1 色谱行为

99种混合标准气体的总离子流色谱图见图1。

图1 混合标准气体的总离子流色谱图Fig.1 TIC chromatogram of mixed standard gases

2.2 标准曲线与方法检出限

用动态稀释仪，将1.00 μmol·mol-1的57种PAMS标准气体和65种TO-14、TO-15标准气体用高纯氮气稀释混合至10.0 nmol·mol-1的标准使用气，另外，将1.00 μmol·mol-1的4种内标混合气用高纯氮气稀释至50.0 nmol·mol-1的内标使用气，然后向预浓缩仪中分别引入20.0、50.0、100、150、200 mL标准气体及每次20 mL的内标气体。将400mL进样体积作为基准的进样体积，根据5次引入的标准气体浓度推算出校准曲线各点的浓度分别为0.50、1.25、2.50、3.75、6.25 nmol·mol-1，4种内标物的浓度均为2.50 nmol·mol-1。在标准系列浓度范围内99种挥发性有机物的相关系数为0.9952～0.9996。具体参数见表1。

连续测定7个接近于方法检出限(MDL)的实验室空白加标样品，计算标准偏差s。按照HJ 168-2010附录A.1方法检出限规定的计算公式：MDL=st(n-1,0.99)(式中t值取3.143)计算该方法测定醛酮类化合物的检出限，结果见表1。

表1 标准曲线与方法检出限

续表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甲基环戊烷10.6810.50～6.25y=1.568x-0.1270.99900.8苯11.6880.50～6.25y=5.179x-0.2690.99890.3环己烷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甲基环己烷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间、对-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邻二甲苯∗21.5331.00～12.5y=1.019x+0.0280.99850.6异丙苯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对乙基甲苯∗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对二乙苯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异丙醇6.4070.50～6.25y=0.241x-0.0020.99930.6顺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

续表1

三氯甲烷9.6450.50～6.25y=0.465x+0.0020.99850.5四氢呋喃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-0.0130.99790.51,4-二氧六环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顺式-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对二氯苯25.8570.50～6.25y=1.316x+0.0180.99860.7邻二氯苯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：*号物质为标准气体重叠物质。

2.3 方法的精密度

对高、低2种不同浓度水平的VOCs混合气体，分别进行6次测定，计算相对标准偏差(RSD)，结果见表2。

表2 精密度实验结果

续表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顺-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环戊烷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甲基环戊烷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环己烷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甲基环己烷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间、对-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

续表2

邻二甲苯2.501.701.691.721.741.611.551.674.47.506.556.255.995.525.955.866.025.8异丙苯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对乙基甲苯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对二乙苯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异丙醇1.250.901.001.030.990.920.880.956.53.753.473.383.222.903.052.863.158.0顺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

续表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氢呋喃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环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顺式-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

续表2

对二氯苯1.250.890.840.860.860.801.000.877.53.753.193.092.992.752.932.832.975.5邻二氯苯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，低浓度等级下，RSD范围为1.6%～12.9%；高浓度等级下，RSD范围为3.1%～11.5%；其中多数组分的RSD小于10%。结果表明：方法的精密度良好。

2.4 样品分析

在某监测点位按照样品采集方法采集2018年9月4日-9月13日期间的样品，数据以D1～10表示。采样时段为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。采集后的样品根据以上的分析条件及标准曲线，进行定性定量分析。经汇总，10天 VOCs的测定结果如图2所示。

图2 测定结果汇总图Fig.1 The results of summary

由10天样品数据结果及汇总图表明：① 在此处环境空气中，常见挥发性有机物为正丁烷、异戊烷、甲苯、对间二甲苯、二氟二氯甲烷、一氯甲烷、二氯甲烷等，比重占40%以上；② 在常见的几种挥发性有机物中，甲苯、对间二甲苯、二氟二氯甲烷、一氯甲烷和二氯甲烷检出率在95%以上；③ 浓度较高点出现在早高峰和晚高峰时段，可能与机动车排放有关，造成该结果的原因尚待进一步探索。

本工作采用苏玛罐采样-气相色谱-质谱法测定环境空气中99种挥发性有机物，方法精密度高，检出限低，检测物质种类多，操作简单。因此，本方法适用于环境空气中挥发性有机物质的测定和臭氧前体物的研究。