Evaluation of Radiello diffusive sampler indicated for thermal desorption for measuring VOCs in ambient air.

1 Evaluation of Radiello diffusive sampler indicated for thermal desorption for measuring VOCs in ambient air E. Gallego1, F.J. Roca1, F.J. Perales1, X. Guardino2 1Laboratori del Centre de Medi Ambient. Universitat Politècnica de Catalunya (LCMA-UPC). Avda. Diagonal, 647. E 08028 Barcelona. Phone: 34934016683, Fax: 34934017150, e-mail: Lcma.[email protected] 2Centro Nacional de Condiciones de Trabajo. INSHT. C/Dulcet, 2-10. E 08034 Barcelona. Phone: 34932800102, Fax: 34932803642, e-mail: cnct[email protected] Odour episodes and environmental air quality are topics of worldwide concern. VOCs are responsible for odorous annoyance of varying degrees of nuisance and represent a threat to human health (irritation of mucous membranes, psychological stress and long-term toxic reactions) and comfort. Sensitive, selective, fast and reliable methodologies are needed to sample and analyse pollutants in ambient air. BACKGROUND Laboratori del Centre de Medi AmbientUPC 18% 12% 12% 4% 1% 4% 2% 2% 1% 8% 36% Paintings and adhesives utilisation Chemical treatment and degreasing Exploitation, treatment and crude oil refinement Fuel distribution Industrial organic chemistry Incineration and combustion processes Food-processing Industrial production and metal processing Waste Industrial products Transport Source: Slovak Environmental Agency Most important VOC sources Laboratori del Centre de Medi AmbientUPC Active sampling has been a traditional sampling technique used to determine pollutants in air; however, passive sampling is being an increasingly used technique for ambient air measurements, specially in urban environments. Active sampling Passive sampling Laboratori del Centre de Medi AmbientUPC Standard Solution Injection Septum Needle Carrier Gas Sample Aerosol Injection Port Liner Sorbent Tube Swagelock Adapter Standard Solution Injection Septum Needle Carrier Gas Sample Aerosol Injection Port Liner Sorbent Tube Swagelock Adapter MATERIALS AND METHODS Active sampling •Carbotrap (24/40 mesh, 70mg) –Weak sorption strength, hydrophobic •Carbopack X (40/60 mesh, 100 mg) –Medium sorption strength •Carboxen 569 (20/45 mesh, 90 mg) –High sorption strength Adsorption direction Desorption direction Weak Medium Strong Silanized glass wool Ribes et al., 2007, J. Chr.A., 1140 (44-55) Laboratori del Centre de Medi AmbientUPC Passive sampling - Adsorbent cartridges filled with 350 mg Carbograph 4 (40/60 mesh) (Code 145) - Yellow Radiello diffusive bodies (code 120-2) Radiello cartridge Microporous diffusion membrane Radial diffusion path Radial diffusion path Radiello cartridge Microporous diffusion membrane Radial diffusion path Radial diffusion path Laboratori del Centre de Medi AmbientUPC Evaluation of Radello Diffuive Sampler Indicated for Thermal Desorption VOCs in Ambient Air Eva Gallego - LCMA-UPC, Spain 2 Thermal desorption TD Desorption temp.: 300 ºC Desorption time: 10 min Transfer line: 200 ºC Cold trap sorbent Tenax TA + Carbotrap Cold trap low: -30 ºC Cold trap high: 300 ºC Desorption flow rate: He (50 ml/min) Inlet split: 4 ml/min Outlet split: 7 ml/min Split ratio: 12 % GC Capillary column: DB-624 (60 m x 0.25 mm x 1.4 µm) Temperature program: 40 ºC (1 min), 6 ºC/min until 230 ºC (5min) Carrier gas: He (19.1 psi) MS Interface: 250 ºC Ionization source: 200 ºC Ionization mode: Electron impact Electron energy: 70 eV Mass range 20 - 300 amu Instrumental settings and operating conditions. TD Desorption temp.: 300 ºC Desorption time: 10 min Transfer line: 200 ºC Cold trap sorbent Tenax TA + Carbotrap Cold trap low: -30 ºC Cold trap high: 300 ºC Desorption flow rate: He (50 ml/min) Inlet split: 4 ml/min Outlet split: 7 ml/min Split ratio: 12 % GC Capillary column: DB-624 (60 m x 0.25 mm x 1.4 µm) Temperature program: 40 ºC (1 min), 6 ºC/min until 230 ºC (5min) Carrier gas: He (19.1 psi) MS Interface: 250 ºC Ionization source: 200 ºC Ionization mode: Electron impact Electron energy: 70 eV Mass range 20 - 300 amu Instrumental settings and operating conditions. Cold trap He Inlet split Adsorbent tube Heating Detector GC column Adsorbent tube Cooling Hot trap He Detector GC column Outlet split He Primary desorption Secondary desorption Cold trap He Inlet split Adsorbent tube Heating Detector GC column Adsorbent tube Cooling Hot trap He Detector GC column Outlet split He Primary desorption Secondary desorption RT: 810 12 14 16 18 20 22 24 26 28 30 32 34 3 6 Time (min) 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 42 RT: 810 12 14 16 18 20 22 24 26 28 30 32 34 3 6 Time (min) 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 1 2+3,4 5+6 78 9,10 11,12+13 14 15 16 171819 20 21+22+23 24 25 26 27 28+29 30 31 32 33 34+35 36+37 38 39+40 41 43 44 45 46 47 48+49 50 51+52 53 54 55 56 RT: 810 12 14 16 18 20 22 24 26 28 30 32 34 3 6 Time (min) 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 RT: 810 12 14 16 18 20 22 24 26 28 30 32 34 3 6 Time (min) 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 RT: 810 12 14 16 18 20 22 24 26 28 30 32 34 3 6 Time (min) 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 42 RT: 810 12 14 16 18 20 22 24 26 28 30 32 34 3 6 Time (min) 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 RT: 810 12 14 16 18 20 22 24 26 28 30 32 34 3 6 Time (min) 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 RT: 810 12 14 16 18 20 22 24 26 28 30 32 34 3 6 Time (min) 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 1 2+3,4 5+6 78 9,10 11,12+13 14 15 16 171819 20 21+22+23 24 25 26 27 28+29 30 31 32 33 34+35 36+37 38 39+40 41 43 44 45 46 47 48+49 50 51+52 53 54 55 56 Ethanol Propanal Acetone Carbon disulfide Methyl acetate Isopropanol Tert-butylmethylether n-Hexane Butanal Ethyl acetate Chloroform Methylethylketone Tetrahydrofuran 1,1,1-Trichloroethane Cyclohexane Carbon tetrachloride Isobutanol Benzene 1-Butanol Trichloroethylene Methylcyclohexane Pentanal Methyl methacrylate Methylisobutylketone Toluene 1,1,2-Trichloroethane Tetrachloroethylene Butyl acetate Hexanal N,N-Dimethylformamide N-Methylformamida Ethylbenzene n-Nonane m-Xylene p-Xylene o-Xylene Styrene Heptanal 2-Butoxyethanol α-Pinene Cyclohexanone Propylbenzene n-Decane 1,3,5-Trimethylbenzene β-Pinene 1,2,4-Trimethylbenzene Benzaldehyde Isocyanatocyclohexane Limonene p-Dichlorobenzene n-Undecane Phenol 1-Octanol Naphthalene Isothiocyanatocyclohexane 2-Methylnaphthalene 1-Methylnaphthalene 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 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 MS analysis Laboratori del Centre de Medi AmbientUPC Two main aspects of passive sampling strategy using Radiello passive samplers are discussed: - a comparative between two types of sampling strategies, active and passive - an evaluation of the effect of passive sampling exposition time Sampling was done in three locations of Catalonia (Spain 2008): La Canonja, Constantí and Sant Adrià del Besós. Active-Passive comparative (12 different places): - active 24-hour samples (sampling flows between 80-120 ml min-1). - passive sampling with sampling periods ranging between 3 and 17 days Sampling exposure time (only in La Canonja and Constantí): - at each sampling location two Radiello samplers were exposed during 1 week (7 days). At the same time, one sampler was exposed during 4 days, replaced at the end of the 4th day for a new sampler that was exposed 3 days, leading to a total of 7 days of exposure. Sampling strategy Laboratori del Centre de Medi AmbientUPC Comparison of adsorbents used -Only compounds with uptake rate values available (www.sigma-aldrich.com/ radiello) were quantified in the passive Radiello samplers, even though much more compounds could be identified qualitatively. -The comparison between active and passive samplings could only be referred to these compounds (Table 1). -There were no significant differences in concentrations obtained between the two kinds of adsorbent tubes for: -trichloroethylene (ttest, p ≤0.05) -toluene (ttest, p ≤0.05) -1,2,4-trimethylbenzene (ttest, p ≤0.05) -p-dichlorobenzene (ttest, p ≤0.05) -m+p-xylene (ttest, p ≤0.01) -BTEX (ttest, p ≤0.05) -Hexane, tetrachloroethylene, butyl acetate, 1-metoxy-2-propanol, 2-ethylhexanol, benzene, ethylbenzene and o-xylene presented significant differences between the two adsorbents. Laboratori del Centre de Medi AmbientUPC RESULTS Table 1. Minimum and maximum, average concentrations (µg m-3) and standard deviation values obtained for the studied compounds for both multi-sorbent tubes and Radiello tubes. *Not statistical differences between the average values from multi-sorbent and radiello tubes were found, t-test, p ≤0.05. ** Not statistical differences between the average values from multi-sorbent and radiello tubes were found, t-test, p ≤0.01. aBTEX = benzene + toluene + ethylbenzene + sum of xylenes 1.0 50.71 ±60.1748.26 ±50.54 186.12 157.61 6.30 8.58 BTEX*, a 0.6 12.30 ±17.137.10 ±11.50 49.87 34.49 1.65 0.65 Ethylbenzene 0.6 4.20 ±2.091.01 ±0.73 8.63 2.68 1.27 0.47 o-xylene 0.7 32.33±40.5321.14 ±29.94 125.36 92.86 2.47 2.63 m+p-xylene** 0.41.46 ±1.060.58 ±0.563.941.930.420.11Benzene 0.8 32.59 ±22.0326.60 ±22.58 72.40 71.52 7.54 4.72 Toluene* 0.9 0.68 ±0.990.60 ±0.76 2.54 1.94 0.06 0.08 1,2,4-trimethylbenzene* 0.9 0.09 ±0.060.08 ±0.06 0.21 0.21 0.01 0.02 p-dichlorobenzene* 0.65.65 ±4.943.53 ±5.92 13.94 26.24 1.28 0.27 2-ethylhexanol 0.111.10 ±4.720.84 ±1.06 19.13 5.01 4.14 0.11 1-metoxi-2-propanol 0.52.00 ±1.380.94 ±1.145.155.280.330.16Butyl acetate 0.33.64 ±6.351.09 ±1.5522.085.690.510.13Tetrachloroethylene 0.8 0.41 ±0.540.31 ±0.44 1.84 1.56 0.02 0.04 Trichloroethylene* 1.71.56 ±1.022.63 ±2.744.3811.250.490.39n-hexane Multisorbent/Radiello RadielloMulti-sorbentRadiello Multisorbent Radiello Multisorbent Compound RatioAverage ± SDMax. ValueMin. Value Comparison of sampling strategy (passive and active) - Good agreement is observed between active and passive samplings for different types of compounds (Figure 1): being all studied correlations significant (Pearson correlation, p ≤0.01). - The correlation coefficients range from 0.70 to 0.99. - Obtained passive concentrations are generally higher than active concentrations. - Some compounds, such as benzene and o-xylene express relevant differences between active and passive sampling strategies. - Passive samples represent the average of 3 to 17 days’ VOCs concentrations, although active samples represent the average of 24-hour’s VOCs concentrations during a particular day. - In other studies, differences between concentrations in simultaneous active and passive strategies have also been found for benzene, toluene and xylenes, mainly due to atmospheric chemical reactions (Pilidis et al. 2005, Sunesson 2007). Laboratori del Centre de Medi AmbientUPC Evaluation of Radello Diffuive Sampler Indicated for Thermal Desorption VOCs in Ambient Air Eva Gallego - LCMA-UPC, Spain 3 Eth ylbenze ne R 2 = 0,9 7 0 10 20 30 40 0 102030405060 Passive (µg m-3) Active (µg m-3) p-dichlorobe nzene R 2 = 0,92 0,00 0,05 0,10 0,15 0,20 0,25 0,00 0,05 0,10 0,15 0,20 0,25 Passive (µg m-3) Active (µg m-3) Trichloroethylene R 2 = 0,94 0,0 0,5 1,0 1,5 2,0 0,0 0,5 1,0 1,5 2,0 Passive (µg m-3) Active (µg m-3) 1,2,4-Trimethylbenzene R 2 = 0,9 9 0,0 0,5 1,0 1,5 2,0 2,5 0,0 0,5 1,0 1,5 2,0 2,5 3,0 Passi ve (µg m -3) Acti ve (µg m-3 ) Benzene R 2 = 0,93 0,0 0,5 1,0 1,5 2,0 2,5 0,0 1,0 2,0 3,0 4,0 5,0 Passive (µg m-3) Active (µg m-3) m+p-xylene R 2 = 0,99 0 20 40 60 80 100 0 20 40 60 80 100 120 140 Passive (µg m-3) Active (µg m-3) o-xylene R 2 = 0,82 0 1 2 3 4 5 6 024681012 Passive (µg m-3) Active (µg m-3) Tolue n e R 2 = 0,70 0 20 40 60 80 0 20406080 Passive (µg m-3) Acti v e ( µg m-3) Figure 1. Comparison of different compounds concentrations (µg m-3) between active sampling on a multisorbent tube (Carbotrap, Carbopack X and Carboxen 569) and passive sampling on a Radiello cartridge (Carbograph 4) from Sant Adrià, Constantí and La Canonja (Spain). BTEX R 2 = 0,94 0 25 50 75 100 125 150 175 200 0 25 50 75 100 125 150 175 200 Passive (µg m-3) Active (µg m-3) Trichloroethylene p-dichlorobenzene 1,2,4-trimethylbenzene toluene benzene m+p xylene o-xylene ethylbenzene Passive μg m-3 Active μg m-3 R2=0,94 R2=0,92 R2=0,99 R2=0,70 R2=0,93 R2=0,99 R2=0,82 R2=0,97 R2=0,94 Influence of exposure/sampling time and air concentration levels in Radiello passive samplers -In several studies it has been observed that in early stages of sampling, uptake rates are higher and, above a certain threshold limit, they decrease to a constant level. - Uptake rate is regulated by the concentration gradient established between the surface of the adsorbent and the entrance of the diffusion zone of the sampling device. - Air pollutant concentrations have also been found to be an important factor in uptake rates decrease, usually depending on the heaviness and volatility of the compound. - In the present study, for tetrachloroethylene and toluene, the mass of compound summed from the samples of 4 and 3 days of exposure is higher than the mass of compound obtained by the samplers that stayed 7 consecutive days exposed (Table 2, Figure 3). Laboratori del Centre de Medi AmbientUPC 0.9 235.7 ±29.8 206.00.6 1750.9 ±430.6 1011.8 n-hexane 1.0 358.9 ±69.0 335.60.6 1654.7 ±529.6 901.0 Benzene 0.9 4660.0 ±611.4 3947.30.7 3978.1 ±1409.8 2544.4 1-metoxi-2-propanol 1.1 14.7 ±1.2 15.40.9 7.4 ±3.0 6.0 Trichloroethylene 1.4 10186.2 ±637.1 13989.91.4 14505.7 ±889.1 20413.0 Toluene 1.6 128.5 ±15.9 199.31.9 70.4 ±7.7 129.6 Tetrachloroethylene 0.7 1147.1 ±162.3 829.71.1 109.5 ±37.9 109.1 butyl acetate 1.1 8280.5 ±23.2 9451.90.7 3628.3 ±491.3 2484.9 Ethylbenzene 1.4 18051.9 ±60.1 25609.60.9 10113.4 ±759.9 9005.9 m+p-xylene 0.8 2126.4 ±9.2 1760.70.6 2329.4 ±351.6 1274.4 o-xylene 1.1 290.1 ±107.3 309.60.6 903.7 ±184.4 554.9 1,2,4 trimethylbenzene 2.2 2.6 ±0.7 5.51.2 41.7 ±9.6 48.0 p-dichlorobenzene 2.3 324.4 ±56.7 719.21.0 2105.7 ±458.5 2004.6 2-etilhexanol 4+3 days/7 days ratio 7 days (ng sample) 4 + 3 days (ng sample) 4+3 days/7 days ratio 7 days (ng sample) 4 + 3 days (ng sample) Compounds ConstantíLa Canonja Table 2. Amount of sampled compound (ng in sample) coming from the samplings of 4+3 days and 7 consecutive days, and ratio between the two amounts. Laboratori del Centre de Medi AmbientUPC 4 days + 3 days La Canonja 0 5000 10000 15000 20000 25000 n-hexane benzene 1-metoxi-2-propanol trichloroethylene toluene tetrachloroethylene butyl a ceta te ethylbenzene m+p-xylene o-xylene 1,2,4-trimethylbenzene p-dichlorobenzene 2-etilhexanol Compounds ng sample 7 days La Canonja 0 5000 10000 15000 20000 25000 n-hexane benzene 1-metoxi-2-propa nol trichloroethylene toluene tetrachloroethylene butyl acetate ethylbenzene m+p-xylene o-xylene 1,2,4-trimethylbenzene p-dichlorobenzene 2-etilhexanol Compounds ng sample 4 days+ 3 days Constantí 0 5000 10000 15000 20000 25000 30000 n-hexane benzene 1-metoxi-2-pro panol trichloroethylene toluene tetrachloroethylene butyl a cetate ethylbenzene m+p-xyle ne o -xyl en e 1,2,4-trimethylbenzene p-dichlorobenzene 2-etilhexanol Compounds ng sample 7 daysConstantí 0 5000 10000 15000 20000 25000 30000 n-hexane benzene 1-metoxi-2-pro pa nol trichloroethylene toluene tetrachloroethylene butyl acetate ethylbenzene m+p-xylene o-xylene 1,2,4-trimethylbenzene p-dichlorobenzene 2-etilhexanol Compounds ng sample Figure 2. Total amount of different compounds (ng sample) adsorbed on Radiello cartridges exposed for a different number of days in La Canonja and Constantí (Spain) between 27-09-2008 and 4-10-2008. Laboratori del Centre de Medi AmbientUPC ng sample ng sample ng sample ng sample 0.92 ±0.120.760.846.76 ±1.663.244.38n-hexane 1.29 ±0.250.981.375.86 ±1.882.133.94Benzene 17.50 ±2.3010.6417.9014.73 ±5.227.7710.581-metoxi-2-propanol 0.05 ±0.0040.040.070.03 ±0.0010.020.02Trichloroethylene 33.92 ±2.1238.8152.2747.61 ±2.9272.4063.19Toluene 0.51 ±0.060.980.640.27 ±0.030.560.46Tetrachloroethylene 4.68 ±0.661.354.880.44 ±0.150.420.45butyl acetate 32.19 ±0.0949.8726.9413.90 ±1.8811.188.35ethylbenzene 67.80 ±0.23125.3674.3837.44 ±2.8140.1028.56m+p-xylene 8.63 ±0.049.845.149.32 ±1.415.394.90o-xylene 1.32 ±0.490.222.294.06 ±0.832.792.291,2,4-trimethylbenzene 0.01 ±0.0030.010.030.19 ±0.040.240.19p-dichlorobenzene 2.27 ±0.404.325.5414.50 ±3.1613.6213.932-etilhexanol 7 d3 d4 d7 d3 d4 dCompounds Constantí (µg m-3)La Canonja (µg m-3) Table 4. Ambient air concentrations (µg m-3) in La Canonja and Constantí (Spain) for 4 days, 3 days and 7 days, between 27-09-2008 and 4-10-2008. Laboratori del Centre de Medi AmbientUPC 0.80.90.50.7n-hexane 0.81.10.40.7benzene 0.61.00.50.71-metoxi-2-propanol 0.81.40.70.7trichloroethylene 1.21.51.51.3toluene 1.91.32.11.7tetrachloroethylene 0.31.01.01.0butyl acetate 1.60.80.80.6ethylbenzene 1.91.11.10.8m+p-xylene 1.10.60.60.5o-xylene 0.21.70.70.61,2,4-trimethylbenzene 1.03.01.31.0p-dichlorobenzene 1.92.40.91.02-etilhexanol 3 d/7 d ratio4 d/7 d ratio3 d/7 d ratio4 d/7 d ratioCompounds Constantí (µg m-3)La Canonja (µg m-3) Table 5. Ratios between 4 and 7 days and between 3 and 7 days concentrations in La Canonja and Constantí (Spain), between 27-09-2008 and 4-10-2008. Laboratori del Centre de Medi AmbientUPC Evaluation of Radello Diffuive Sampler Indicated for Thermal Desorption VOCs in Ambient Air Eva Gallego - LCMA-UPC, Spain 4 REMARKS - One of the key aspects regarding air monitoring is to determine the suitability of the methodology chosen. -The comparison between validated active air multi-sorbent tubes and Radiello diffusive samplers show no significant differences between the two methodologies for several compounds studied. -For the Radiello passive sampler, relevant differences have not been observed between the sum of two shorter sampling periods (4 days + 3 days) and a longer sampling period (7 days). -The Radiello diffusive sampler provides satisfactory quantitative measurements and is suitable for the determination of several VOCs in ambient air. -Radiello passive sampler coupled with ATD-GC/MS is a simple to use, sensible and cheap method to assess ambient air concentrations of VOCs. -More research has to be done to enhance the results obtained in this study. Laboratori del Centre de Medi AmbientUPC Evaluation of Radello Diffuive Sampler Indicated for Thermal Desorption VOCs in Ambient Air Eva Gallego - LCMA-UPC, Spain