Indoor air pollutants

Transcription

1 Passive sampling in indoor air quality Monika PARTYKA, Bożena ZABIEGAŁA, Jacek NAMIEŚNIK Department of Analytical Chemistry, Chemical Faculty, Gdansk University of Technology, Poland

2 Indoor air pollutants outdoor sources infiltration of atmospheric air pollutants (especially harmful in vicinity of emission sources) indoor sources endogenous user s dependent and non-dependent - gas stoves; - furnishing elements; - consumer products; - lacquer and paints; - wooden-based materials; - environmental tobacco smoke.

3 Methods used to determine VOC concentrations in indoor air ACTIVE require active devices need for power supply noisy and irritating PASSIVE no active devices (pumps, flow meters, etc.) no need for power supply less intrusive, hence more acceptable no need qualified engineering supervision

4 Main types of passive samplers DIFFUSION SAMPLERS PERMEATION SAMPLERS - sampling rate can be estimated based on the chemical properties of the analyte (diffusivity) and sampler geometry - sensitive to moisture, air currents, temperature variations - need calibration for each analyte - effective moisture elimination, much less sensitive to air currents and temperature changes

5 Theory of passive sampling Mass (M) of a gaseous component transported across a membrane by diffusion over a specific period of time (t): A P U t = M = p 0 L M t U - diffusional mass-transfer rate M - amount of a compound trapped on the sorbent bed A - cross-section of the diffusion path L M membrane thickness P permeability coefficient of the sampled component p o partial pressure of the analyte near the outer membrane surface t time After transformation: C 0 = k M t

6 Permeability P = D e K L M D e - effective diffusion coefficient of the analyte in the membrane material K - partition coefficient of the analyte between the membrane material and ambient air Thus far, calibration constants had to be determined experimentally for each individual analyte

7 Permeation process Sorption of the analyte on the surface of the membrane. Dissolution in the membrane material and diffusion of the dissolved analyte through the membrane. Dissolution is governed by the solubility of the analyte in the membrane material. Desorption of the analyte on the opposite side of the membrane.

8 Design of the passive sampler

9 Proposed approach Estimation of the calibration constants of the analytes from their physicochemical properties: - number of carbon atoms in a member of a homologous series of compounds - boiling point - molecular weight - GC retention index

10 Analytes n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane benzene, toluene, ethylbenzene, butylbenzene methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl butyrate, ethyl butyrate, methyl heptanoate 1-butanol, 1-pentanol, 1-heptanol, 1-heptanol, 1-octanol, 2-methyl-1-propanol, 2-pentanol, 2,3-dimethyl-2-butanol, 3-hexanol, 2-hexanol, 2,4-dimethyl-3-pentanol, 1-hexanol, 6-methyl-2-heptanol, 2-ethyl-1-hexanol

11 Analytical conditions environmental chamber parameters temperature: 23 C±0.1 C, relative humidity: 43 % ±2 %, air exchange rate: 0.7 h -1, chamber volume: 0.1 m 3, 30 min desorption (after transferring the active carbon to a glass vial) loading rate: m 2 /m 3 1 ml of CS 2 for aliphatic and aromatic hydrocarbons or 1 ml of mixture of CS % isopropanol for esters and alcohols gas chromatograph Hewlett Packard, GC System 5890 detector FID, 280 C carrier gas helium, at 2.2 ml/min temperature program 40 C, 7 C/min to 220 C data acquisition and processing ChemStation software capillary column DB-1, 32 m x 0.32 mm, 5.0 µm film thickness 007-1, Quadrex, 30 m x 0.32 mm x 0.25-µm film thickness calibration method external standard (ESTD) multipoint calibration curve

12 Calibration constant vs. the number of carbon atoms Calibration constant k [min ml -1 ] aliphatic hydrocarbons 0,25 aromatic hydrocarbons alcohols 0,2 esters 0,15 0,1 0, Number of carbon atoms Calibration constant k [min ml-1] vs. boiling point y = x R 2 = Calibration constant k [min ml -1 ] vs. molecular weight y = x R 2 = Molecular weight of the analyte

13 What to do when the identity of a compound is unknown? Calibration constant vs. physico-chemical properties of the analytes (number of carbon atoms in homologous series, the boiling point or molecular weight of compound) Calculate calibration constant on the basic of finding equation

14 What to do when the identity of a compound is unknown? Permeability through the membrane is determined primarily by the solubility of the analyte in the membrane material The membrane is made of the same material as the stationary phase in the GC column used (PDMS) Retention time is determined by the partition coefficient of the analyte between the carrier gas and the stationary phase, which also depends on the solubility of the analyte in PDMS There should be a relationship between the retention parameters and the calibration constants of the analytes!

15 Linear Temperature Programmed Retention Index (LTPRI) LTPRI=100x(t(A)-t(n)/t(n+1) -t(n)) + 100n t(a) retention time of the analyte t(n) retention time of the n-alkane eluting directly before the analyte t(n+1) retention time of the n-alkane eluting directly after the analyte n number of carbon atoms for the n-alkane eluting directly before the analyte. LTPRI were determined using: - capillary columns from different manufacturers (Agilent, J&W, Quadrex, Restek) and of different thickness of stationary phase (5 µm, 1µm, 0.25 µm); - different chromatographic conditions (flow rate of carrier gas, temperature rate, initial oven temperature); - chromatographs from different manufacturers (Hewlett Packard, Carlo Erba).

16 Calibration constant vs. LTPRI -1 k [min ml ] k [min m ] n-alkanes aromatic hydrocarbons alcohols esters LTPRI 1200 R 2 EQUATION n-alcanes y = x aromatic hydrocarbons y = x alcohols y = x esters y = x y = x k [min ml -1] R 2 =

17 Indoor air analysis with the permeation passive sampler LTPRI Analyte 645 n-butanol 658 benzene 751 n-pentanol 757 toluene 821 2,4-dimethyl-3-pentano 844 ethylbenzene 859 n-hexanol methyl-2-heptanol 950 n-heptanol 964 unknown 1030 unknown HP 6890, capillary column: 007-1, Quadrex, 30 m x 0.32 mm x 1.0-µm, oven temperature 50 C, 7 C/min to 180 C, carrier gas: He 1.5 ml/min

18 Indoor air analysis with the permeation passive sampler Concentration [µg/m ] benzene toluene butyl acetate ethylbenzene m-xylene styrene exposition II (March, 2001) exposition I (March, 2000) m-dichlorobenzene

19 Conclusions The approach proposed eliminates the biggest obstacle in a wider acceptance of permeation passive samplers, the need to calibrate each sampler for each individual analyte All the advantages of passive sampling are maintained Permeation passive samplers can be deployed in the same way as active sampling, i.e. without the need to calibrate them before measurements

20 List of Publications Kot A., Zabiegała B., Namieśnik J., Passive sampling for long-term monitoring of organic pollutants in water. Trends in Anal. Chem., 19, (2000). Namieśnik J., Górecki T., Passive sampling in environmental analysis. LC-GC Europe, 13, (2000). Zabiegała B., Zygmunt B., Przyk E., Namieśnik J., Applicability of silicone membrane passive samplers for monitoring of indoor air quality. Anal. Lett., 33, (2000). Zabiegała B., Przyk E., Przyjazny A., Namieśnik J., Evaluation of indoor air quality on the basis of measurements of VOC concentrations. Chem. Anal., 45, (2000). Przyk E., Zabiegała B., Górecki T., Namieśnik J., Methods for the control of indoor air quality. Chem. Anal., 45, (2000). Zabiegała B., Kot A., Namieśnik J., Long-term monitoring of organic pollutants in water application of passive dosimetry. Chem. Anal., 45, (2000). Górecki T., Namieśnik J., Passive sampling, TrAC., 21, (2002). Zabiegała B., Górecki T., Przyk E., Namieśnik J., Permeation passive sampling as a tool for the evaluation of indoor air quality. Atmos. Environ., 36, (2002). Zabiegała B., Górecki T., Namieśnik J., Calibration of permeation passive samplers with silicone membranes based on physicochemical properties of the analytes. Anal. Chem., 75, (2003).

21

22 Acknowledgements The Department of Analytical Chemistry constitutes Centre of Excellence in Environmental Analysis and Monitoring which is a research project supported by the European Commission under the Fifth Framework Programme and contributing to the implementation of the Key Action Sustainable Management and Quality of Water within the Energy, Environment and Sustainable Development (Contract No.: EVK1-CT ). The authors acknowledge this generous support.