CA2237133A1 - Nitrogen dioxide passive sampling system - Google Patents
Nitrogen dioxide passive sampling system Download PDFInfo
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- CA2237133A1 CA2237133A1 CA002237133A CA2237133A CA2237133A1 CA 2237133 A1 CA2237133 A1 CA 2237133A1 CA 002237133 A CA002237133 A CA 002237133A CA 2237133 A CA2237133 A CA 2237133A CA 2237133 A1 CA2237133 A1 CA 2237133A1
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- silica gel
- sampler
- sampling media
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- 238000005070 sampling Methods 0.000 title claims abstract description 52
- MGWGWNFMUOTEHG-UHFFFAOYSA-N 4-(3,5-dimethylphenyl)-1,3-thiazol-2-amine Chemical compound CC1=CC(C)=CC(C=2N=C(N)SC=2)=C1 MGWGWNFMUOTEHG-UHFFFAOYSA-N 0.000 title claims description 14
- JCXJVPUVTGWSNB-UHFFFAOYSA-N nitrogen dioxide Inorganic materials O=[N]=O JCXJVPUVTGWSNB-UHFFFAOYSA-N 0.000 title claims description 14
- GSEJCLTVZPLZKY-UHFFFAOYSA-N Triethanolamine Chemical compound OCCN(CCO)CCO GSEJCLTVZPLZKY-UHFFFAOYSA-N 0.000 claims abstract description 33
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 24
- 239000000741 silica gel Substances 0.000 claims abstract description 18
- 229910002027 silica gel Inorganic materials 0.000 claims abstract description 18
- 238000009792 diffusion process Methods 0.000 claims description 21
- 230000004888 barrier function Effects 0.000 claims description 12
- 239000002808 molecular sieve Substances 0.000 claims description 7
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims description 7
- 239000004809 Teflon Substances 0.000 claims description 5
- 229920006362 Teflon® Polymers 0.000 claims description 5
- 239000011148 porous material Substances 0.000 claims description 5
- 238000000034 method Methods 0.000 description 20
- 239000003570 air Substances 0.000 description 9
- IOVCWXUNBOPUCH-UHFFFAOYSA-M Nitrite anion Chemical compound [O-]N=O IOVCWXUNBOPUCH-UHFFFAOYSA-M 0.000 description 7
- 239000011521 glass Substances 0.000 description 7
- 239000000243 solution Substances 0.000 description 7
- 239000011248 coating agent Substances 0.000 description 5
- 238000000576 coating method Methods 0.000 description 5
- 238000001035 drying Methods 0.000 description 5
- 239000000499 gel Substances 0.000 description 4
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 239000000809 air pollutant Substances 0.000 description 3
- 231100001243 air pollutant Toxicity 0.000 description 3
- 239000012491 analyte Substances 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
- 239000001913 cellulose Substances 0.000 description 3
- 229920002678 cellulose Polymers 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 238000012544 monitoring process Methods 0.000 description 3
- 239000004033 plastic Substances 0.000 description 3
- 239000000377 silicon dioxide Substances 0.000 description 3
- 239000012080 ambient air Substances 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 239000003365 glass fiber Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- MHUWZNTUIIFHAS-XPWSMXQVSA-N 9-octadecenoic acid 1-[(phosphonoxy)methyl]-1,2-ethanediyl ester Chemical compound CCCCCCCC\C=C\CCCCCCCC(=O)OCC(COP(O)(O)=O)OC(=O)CCCCCCC\C=C\CCCCCCCC MHUWZNTUIIFHAS-XPWSMXQVSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 241001432959 Chernes Species 0.000 description 1
- 238000003916 acid precipitation Methods 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000004927 clay Substances 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 238000005206 flow analysis Methods 0.000 description 1
- 238000004401 flow injection analysis Methods 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 238000004255 ion exchange chromatography Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- VGQXTTSVLMQFHM-UHFFFAOYSA-N peroxyacetyl nitrate Chemical compound CC(=O)OO[N+]([O-])=O VGQXTTSVLMQFHM-UHFFFAOYSA-N 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- IOVGROKTTNBUGK-SJCJKPOMSA-N ritodrine Chemical compound N([C@@H](C)[C@H](O)C=1C=CC(O)=CC=1)CCC1=CC=C(O)C=C1 IOVGROKTTNBUGK-SJCJKPOMSA-N 0.000 description 1
- 229940047047 sodium arsenate Drugs 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000002594 sorbent Substances 0.000 description 1
- 238000002798 spectrophotometry method Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/02—Devices for withdrawing samples
- G01N1/22—Devices for withdrawing samples in the gaseous state
- G01N1/2273—Atmospheric sampling
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
- G01N33/0036—General constructional details of gas analysers, e.g. portable test equipment concerning the detector specially adapted to detect a particular component
- G01N33/0037—NOx
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Engineering & Computer Science (AREA)
- Analytical Chemistry (AREA)
- Physics & Mathematics (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Food Science & Technology (AREA)
- Medicinal Chemistry (AREA)
- Combustion & Propulsion (AREA)
- Biomedical Technology (AREA)
- Molecular Biology (AREA)
- Sampling And Sample Adjustment (AREA)
Abstract
A novel passive NO2 sampling media is disclosed. The media comprises silica gel having high internal surface area combined with triethanolamine.
Description
' CA 02237133 1998-OS-07 NITROGEN DIOXIDE PASSIVE SAMPLING SYSTEM
TI~CHNICAL ;FIELD
'The invention relates to passive samplers and sampling media for nitrogen dioxide.
B,~CKGROUlfD OF THE INVENTION
Nitrogen dioxide (NOZ ) is a criteria air pollutant. It is required to be monitored by law in many countries because it is a major source of acid rain and is the only gaseous air pollutant which contributes to visibility reduction.
Many sampling methods for monitoring NOZ in the ambient air have been developed. These methods are generally categorized as either active methods or passive methods. Examples of active methods are described i n the following publications:
1. Federal Register, "Sodium Arsenate method for the determination of Nitrogen Dioxide in the Atmosphf;re", Vol. 42, p62971, 12/14/1977.
TI~CHNICAL ;FIELD
'The invention relates to passive samplers and sampling media for nitrogen dioxide.
B,~CKGROUlfD OF THE INVENTION
Nitrogen dioxide (NOZ ) is a criteria air pollutant. It is required to be monitored by law in many countries because it is a major source of acid rain and is the only gaseous air pollutant which contributes to visibility reduction.
Many sampling methods for monitoring NOZ in the ambient air have been developed. These methods are generally categorized as either active methods or passive methods. Examples of active methods are described i n the following publications:
1. Federal Register, "Sodium Arsenate method for the determination of Nitrogen Dioxide in the Atmosphf;re", Vol. 42, p62971, 12/14/1977.
2. Federal Register, "TGS-ANSA Method for the Determination of Nitrogen Dioxide in the Atmosphere", Vol. 42, p62971, 12/14/1977.
3 . Ellis, E.C.; Margeson, J. H. "Evaluation of TEA Procedure for Determination of Nitrogen Dioxide in Ambient Air", EP.A report NO. 650/4.74-031 July 1974.
4. Lipari, L. "New Solid - sorbent: Method for Ambient Nitrogen Dioxide monitoring", Anal. Chern. 1984, 56, 1920-1826.
5. Blacker J.H. "Triethanolalnine :for Collecting NOZ in the TLV Range", Am.
Ind.
Hyg. Assoc. J., 1973, 34, 390-396.
Active methods use devices to pump air through collection devices to collect the NOZ .
,A passive or diffusive sampler is a device which samples an atmospheric gas at a rate controlled by the physical process of diffusion through a static air layer or permeation through a membrane. Passive samplers rely upon a concentration gradient across a diffusion barrier to produce a mass transfer of gaseous molecules. The principle of operation is based on Fick's first law of diffusion:
41=-DA do dx (1) where J = diffusion transfer rate, D= diffusion coefficient A= effective cross-sectional area x= distance along the diffusion path c= analyte concentration at distance x The negative siign in equation 1 indicates that the concentration of the analyte decreases in the direction of diffusion.
:Equation 1 may be simplified as follows:
Q=R.,.Cat ~2) 'where Q= mass uptake RS = sampling rate Ce = concentration of the analyte t = sampling time From equation 2 it can be seen that the key parameter related to the correct measurement of NO Z in the atmosphere using a passive sampler is its sampling rate. Active samplers have a known sampling rate, which is the pump's flow rate. A passive sampler's sampling rate depends on many factors including NOZ concentration. ambient temperature, relative humidity, wiind direction, wind speed, the exposure and structure of the sampler and the collection media. Examples of passive sampling vmethods may be found in the following publications:
1. 1?almes, E.D.,; Gunnison.) A.F.; DiMatti:o, J.; Tomczyk, C. "Personal Sampler ~:or Nitrogen Dioxide", Am. Ind. Hyg. fl.ssoc. .1., 1976, 37, 570-577.
2. perm, M. "Further Development of a Diffusion Sampler for NOZ", IVL-T 86/180, Swedish Environmental Research Institute 1986.
3. Mulik, J.D.; Williams, D. "Passive Sampling Devices for NOZ", Proceedings of ~'he 1986 EPAlAPCA symposium of mecxsurement of Toxic Air Pollutants, l~aleigh, NC, April 1986, pp61-79.
4. hair, A.J.; Penkett, S.A.; Ovola, P. "Development of a Simple Passive 'technology for the Determination of N itrogen Dioxide in Remote Continental l:,ocations", Atmos. Environ., 1991, 25(9), 1927-1939.
5. Ogawa & Company US~~ Inc. "NO-NOz Simultaneous Sampling Protocol", June 1994.
Ind.
Hyg. Assoc. J., 1973, 34, 390-396.
Active methods use devices to pump air through collection devices to collect the NOZ .
,A passive or diffusive sampler is a device which samples an atmospheric gas at a rate controlled by the physical process of diffusion through a static air layer or permeation through a membrane. Passive samplers rely upon a concentration gradient across a diffusion barrier to produce a mass transfer of gaseous molecules. The principle of operation is based on Fick's first law of diffusion:
41=-DA do dx (1) where J = diffusion transfer rate, D= diffusion coefficient A= effective cross-sectional area x= distance along the diffusion path c= analyte concentration at distance x The negative siign in equation 1 indicates that the concentration of the analyte decreases in the direction of diffusion.
:Equation 1 may be simplified as follows:
Q=R.,.Cat ~2) 'where Q= mass uptake RS = sampling rate Ce = concentration of the analyte t = sampling time From equation 2 it can be seen that the key parameter related to the correct measurement of NO Z in the atmosphere using a passive sampler is its sampling rate. Active samplers have a known sampling rate, which is the pump's flow rate. A passive sampler's sampling rate depends on many factors including NOZ concentration. ambient temperature, relative humidity, wiind direction, wind speed, the exposure and structure of the sampler and the collection media. Examples of passive sampling vmethods may be found in the following publications:
1. 1?almes, E.D.,; Gunnison.) A.F.; DiMatti:o, J.; Tomczyk, C. "Personal Sampler ~:or Nitrogen Dioxide", Am. Ind. Hyg. fl.ssoc. .1., 1976, 37, 570-577.
2. perm, M. "Further Development of a Diffusion Sampler for NOZ", IVL-T 86/180, Swedish Environmental Research Institute 1986.
3. Mulik, J.D.; Williams, D. "Passive Sampling Devices for NOZ", Proceedings of ~'he 1986 EPAlAPCA symposium of mecxsurement of Toxic Air Pollutants, l~aleigh, NC, April 1986, pp61-79.
4. hair, A.J.; Penkett, S.A.; Ovola, P. "Development of a Simple Passive 'technology for the Determination of N itrogen Dioxide in Remote Continental l:,ocations", Atmos. Environ., 1991, 25(9), 1927-1939.
5. Ogawa & Company US~~ Inc. "NO-NOz Simultaneous Sampling Protocol", June 1994.
6. 1=IIOSH Method 6700, 1984.
7. perm, M.; Rodhe, H. "Measurement of Air Concentration of SOZ, NOZ and NH3 at Rural and Remote Sites in Asia", J. .Armos. Chem., 1997, 27, 17-29.
'rriethanolamine (TEA) is a commonly used agent in passive samplers because it captures NO-~ very efficiently and may be analyzed easily by ion chromatography to a very low detection limit. TEA is typically coated on cellulose or glass fibre filters or on metallic screens. However, numerous difficulties exist with the use of such TEA
sampling media. It ha.s been found that prior art TEA-coated cellulose or glass fibre filters or metallic screens demonstrated v~ridely varying sampling rates as ambient temperature is decreased from 27°C to 6°C. Similarly, a reduction in relative humidity from 79% to 10% is known to increase NOz sampling rates by about 50%. When I~-OZ concentration increases 10-fold from 20 parts per billion (ppb) to about 200 ppb, the NOz sampling rate has been known to increase about 2~~0%.
la is therefore desirable t,o have a passive sampling media for NOz which exhibits a more; stable sampling rate across a wide range of ambient temperature and other variables which affect prior art passive sampling media.
SiIMMARY OF THE INVENTION
l:n one aspect of the invention, the invention is a nitrogen dioxide sampling medium which has a sampling rate which is relatively insensitive to atmospheric fluctuations in temperature, relative humidity and other ambient conditions. In general terms, the sampling media comprises silica gel combined with triethanolamine (TEA) or molecular sieve combined with TEA.
l:n another aspect of the iinvention, the invention is an all-season sampler for collecting atmospheric nitrogen dioxide comprising:
(a) a sampler body having a downwardly opening cavity;
(b) sampling media disposed within the cavity comprising silica gel combined with ~:riethanolamine (TEA) o:r molecular sieve combined with TEA; and (c) means for retaining the sampling media within the cavity.
The sampler may further comprise an a.ir diffusion barrier and a support ring disposed between the retainer means and the diffusion barrier thereby creating an air gap between the diffusion barrio;r and the sampling media.
B1ZIEF DESCF;IPTION OF THE DF,A'WINGS
lEmbodiments of the invention will now be described with reference to the accompanying drawings in which:
1~ figure 1 is a cross-sectional depiction of the preferred embodiment of the sampler of the present invention.
Figure 2 is a cross-sectional depiction of the sampler mounted within a rain shelter.
DIETAILED DIESCRIPTION (BEST MODE) OF THE INVENTION
In one aspect of the invention, there is disclosed a passive NOZ sampler ( 10) as shown in Figure 1. In general terms, the preferred embodiment of the sampler ( 10) comprises a lbody ( 12), sampling media ( 14), a screen ( I 6), a support ring ( 18), a diffusion barrier (20) and a cover (2~?).
'Che body ( 12) defines a cavity (24) which is preferably cylindrical and closed at one end. TI ~e sampling media ( 14) i s retained within the cavity (24) by the screen ( 16). In the preferred embodiment, two polyester screens are used, having mesh sizes of 110 and 20 respectively.
_5_ 'the support ring ( 18) fits snugly in the cavity (24) and retains the screens ( 16) in place. The support ring ( 18) also creates an air gap between the sampling media ( 14) and the diffusion barrier (20). The diffusion barrier (20) is preferably a Teflon~
film which acts both as a gas diffusion controller and prevents contamination of the sampling media by air-borne particles. A ring-shaped cover (22) may be friction fit over the body ( 12) and the diffusion barrier (20) to hold the assembly of the sampler ( 10) together.
.As shown in Figure 2, tb~e samplers ( 1 CI) may be mounted in a rain shelter (26).
The shoulder (;? 8) built into the body ( 12) facilitates mounting of the samplers ( 10) so that the cavity (24) faces downward.
In another aspect of the invention, there is disclosed a new sampling media for NO 2 comprising a combination of silica. gel as a carrier and triethanolamine (TEA) as the NOZ
binding agent. Silica gel has a very hil;h internal surface area and apparently bonds well with TEA. The silica gel surface presents many acidic hydroxyl groups which, it is surmised, may be bonded to by TEA. Other materials which may be suitable for combining with TEA in accordance with this aspect of the invention include molecular sieve (silicaceous clay) which also has a very high internal surface area and a high affinity for TEA, similar to silica gel.
In the preferred embodiment, the silica gel used has a mesh size of about 60/100 and an average pore size of about 22A and has internal surface area of approximately 66.9 square meters per gram of gel. Silica gel with an average pore size of 60A and 150A
will also yield satisfactory results. In an alternative embodiment, molecular sieve 13X, with an internal surface area of approximately 600 square meters per gram and an average pore size of approximately 13A may be used.
(reparation of the sampling media is exemplified by the method described herein. This rr.~ethod or any other method producing t:he media is not intended to be limiting of the scope of the invention claimed herein.
Prepar;~tion of the Sampling Media a. preparation of TEA coating solution Ten grams of TEA (BDH, Toronto, Canada) and one gram of glycerol were dissolved in 100 ml of methanol and de-ionized {DI) water (Fisher Scientific, Nepean Canada) solution (50:50 volume). The coating solution was kept in a plastic bottle with a cap sealed with Teflon tape, and sto red at 4°C.
b. :silica gel cleaning Two hundred grams of silica ge:l (W.R. Grace & Co., Baltimore, Maryland, 22 A, 60/100 :mesh) was washed with DI water to remove fine particles. After washing, the silica gesl was transferred to several glass petri dishes and dried in a vacuum oven at 60°C and 15-mm Hg pressure for 3 hours. During drying, a small stream of room air purified by active carbon was directed at the gel in order to speed the drying process.
After drying, the silica gel was transferred to a glass column with frit at the column bottom. The column was installed in a gas chromatograph (GC) oven with 20 ml/min of helium as carrier gas. The silica gel was heated at 220°C for 24 hours, then cooled down to room temperature. The heat-treated silica gel was transferred in a glass bottle with a c:ap sealed with Teflon tape. The glass bottle was stored at 4°C.
c. Coating procedure 50 ml of each the heat-treated siilica gel and the TEA coating solution was added into a 20 crr~ (diameter) glass petri dish. After 5 minutes, the excess solution was decanted and the petri dish was placed into a vacuum oven and dried for 2 hours. The vacuum drying conditions were the same: as described above in section b. After drying, the coated silica gel was transferred to a glass bottle with a cap sealed with Teflon tape, Then, the glass bottle was put into a resealable plastic bag, sealed and kept at 4°C.
d. ~4nalytical procedure The spectrophotometric method, the flow injection analysis method and the continuous flow analysis method, are used for the nitrite analysis. These methods are well known in the art of nitrite analysis.
_g_ The novel sampling media of the present invention was tested in the laboratory in accordance with the analytical procedures referred to above.
1. Temperature study Cellulo:;e filters (Millipore, Bed:Ford, MA) coated with the same TEA coating solution and dried in th~~ vacuum oven under thc: same conditions for the sampling media prepared in accordance with Example 1 above (hereinafter referred to as "CHEMIXTM") were compared wiah CHEMIX'~M. Table 1 lists the comparison results. The comparison was conducted at -2 7 °C and 20°C., the relative humidity was about 4%, the cross diffusion barrier surface velocity was 0.5 cm/sec, and the NOZ concentrations were 30 ppb and 150 ppb.
Table 1. ;3ampling rate and temperature Nitrite Concentration (~,g/ml) at Different Temperatures Collection Media CHEMIXTM 0.97 1.10 TEA-cellulose filter 0.19 0.96 Table 1 clearly shows that the sampling; rate of CHEMIXTM changed only slightly when the temperature reduction from 20°C to -27°C, but the sampling rate for TEA coated filters decreased about 80%.
2. Sampling rate comparison 3 0 Table 1 also indicates that the C HEMIXTM has higher sampling rates than the TEA
coated filter. The CHEMIXTM collected about 5 times higher NOz than the TEA
coated filter at -27°C; the ratio was about 1.5 times at room temperature.
3. Relative humidity study Table 2 lists the sampling rate comparison of the CHEMIXTM and the TEA coated filter. The studies were conducted at 20°C, 150 ppb NOZ concentration, 0.5 cm/sec CDBS
velocity. The RHs ranged from 4% to 69%. It can be observed that the change of the relative humidity did not affect the CH:EMIXT'M sampling rate significantly, but did affect the TI~A coated filter's sampling rate.
Table 2. ;3ampling rate and relative humidity Collection Nitrite Media Concentration (~,g/ml j at Different Temperatures and Different Relative Humidities 4% 20% 40% 4% 50%
CHEMIXTM 0.95 0.96 0.99 1.08 1.12 TEA-filter 0.17 0.35 0.40 0.86 0.96 4. Stability study After e~;posing the NOZ passive sampler at 150 ppb NOZ concentration, half of the passive sampleo~s were taken out off the chamber and sealed in a resealable plastic bag which w<~s stored at -:?0°C. The rest of the passive samplers in the chamber were purged with zero air at room temperature for 5 days. The test results are shown in Table 3. The results show nc~ significant difference between the samplers in a cooler and in the chamber, which indicates th;~t the CHEMIXTM NOZ complex is stable.
Table 3. Comparison of samplers in cooler and in chamber Sampler Storing Condition Nitrite Concentration (~cg/ml) Cooler (-20C) 0.14 Chambf;r Purged with Air (20C'.) 0.14 5. Capacity study The N0, passive samplers were exposed at 16CI ppb NOz concentration, 3% RH and 20°C for one day, seven days and nine days separately. The results are shown in Table 5. It is concluded that the passive samplers c;an at least be used to monitoring 50 ppb NOZ
concentration in the atmosphere for one:-month exposure period.
Table 4. ~~apacity study Collection Nitrite Collected (~,g) at Different Exposure Time 25.5 hours 170.5 hours 203 hours Total 25.9 164.5 203.7 Per Hour 1.0 1.0 1.0 6. Practic,~l quantitative detection limit From field blank results, it is found that the pooled standard deviation was 0.1 ug of ni~.rite per blank. The practical quantitative detection limit, thus, can be taken as 1 ug per bl;~nk (10 times of the standard deviation). This is the equivalent to exposure of the passive sampler to 0.1 ppb for one month.
7. Analytical recovery study The standard nitrite solutions were spiked into the sampling media. After drying in the vacuum oven, the spiked media were extracted following the procedure described above.
The recovery vas found to be 100%.
'rriethanolamine (TEA) is a commonly used agent in passive samplers because it captures NO-~ very efficiently and may be analyzed easily by ion chromatography to a very low detection limit. TEA is typically coated on cellulose or glass fibre filters or on metallic screens. However, numerous difficulties exist with the use of such TEA
sampling media. It ha.s been found that prior art TEA-coated cellulose or glass fibre filters or metallic screens demonstrated v~ridely varying sampling rates as ambient temperature is decreased from 27°C to 6°C. Similarly, a reduction in relative humidity from 79% to 10% is known to increase NOz sampling rates by about 50%. When I~-OZ concentration increases 10-fold from 20 parts per billion (ppb) to about 200 ppb, the NOz sampling rate has been known to increase about 2~~0%.
la is therefore desirable t,o have a passive sampling media for NOz which exhibits a more; stable sampling rate across a wide range of ambient temperature and other variables which affect prior art passive sampling media.
SiIMMARY OF THE INVENTION
l:n one aspect of the invention, the invention is a nitrogen dioxide sampling medium which has a sampling rate which is relatively insensitive to atmospheric fluctuations in temperature, relative humidity and other ambient conditions. In general terms, the sampling media comprises silica gel combined with triethanolamine (TEA) or molecular sieve combined with TEA.
l:n another aspect of the iinvention, the invention is an all-season sampler for collecting atmospheric nitrogen dioxide comprising:
(a) a sampler body having a downwardly opening cavity;
(b) sampling media disposed within the cavity comprising silica gel combined with ~:riethanolamine (TEA) o:r molecular sieve combined with TEA; and (c) means for retaining the sampling media within the cavity.
The sampler may further comprise an a.ir diffusion barrier and a support ring disposed between the retainer means and the diffusion barrier thereby creating an air gap between the diffusion barrio;r and the sampling media.
B1ZIEF DESCF;IPTION OF THE DF,A'WINGS
lEmbodiments of the invention will now be described with reference to the accompanying drawings in which:
1~ figure 1 is a cross-sectional depiction of the preferred embodiment of the sampler of the present invention.
Figure 2 is a cross-sectional depiction of the sampler mounted within a rain shelter.
DIETAILED DIESCRIPTION (BEST MODE) OF THE INVENTION
In one aspect of the invention, there is disclosed a passive NOZ sampler ( 10) as shown in Figure 1. In general terms, the preferred embodiment of the sampler ( 10) comprises a lbody ( 12), sampling media ( 14), a screen ( I 6), a support ring ( 18), a diffusion barrier (20) and a cover (2~?).
'Che body ( 12) defines a cavity (24) which is preferably cylindrical and closed at one end. TI ~e sampling media ( 14) i s retained within the cavity (24) by the screen ( 16). In the preferred embodiment, two polyester screens are used, having mesh sizes of 110 and 20 respectively.
_5_ 'the support ring ( 18) fits snugly in the cavity (24) and retains the screens ( 16) in place. The support ring ( 18) also creates an air gap between the sampling media ( 14) and the diffusion barrier (20). The diffusion barrier (20) is preferably a Teflon~
film which acts both as a gas diffusion controller and prevents contamination of the sampling media by air-borne particles. A ring-shaped cover (22) may be friction fit over the body ( 12) and the diffusion barrier (20) to hold the assembly of the sampler ( 10) together.
.As shown in Figure 2, tb~e samplers ( 1 CI) may be mounted in a rain shelter (26).
The shoulder (;? 8) built into the body ( 12) facilitates mounting of the samplers ( 10) so that the cavity (24) faces downward.
In another aspect of the invention, there is disclosed a new sampling media for NO 2 comprising a combination of silica. gel as a carrier and triethanolamine (TEA) as the NOZ
binding agent. Silica gel has a very hil;h internal surface area and apparently bonds well with TEA. The silica gel surface presents many acidic hydroxyl groups which, it is surmised, may be bonded to by TEA. Other materials which may be suitable for combining with TEA in accordance with this aspect of the invention include molecular sieve (silicaceous clay) which also has a very high internal surface area and a high affinity for TEA, similar to silica gel.
In the preferred embodiment, the silica gel used has a mesh size of about 60/100 and an average pore size of about 22A and has internal surface area of approximately 66.9 square meters per gram of gel. Silica gel with an average pore size of 60A and 150A
will also yield satisfactory results. In an alternative embodiment, molecular sieve 13X, with an internal surface area of approximately 600 square meters per gram and an average pore size of approximately 13A may be used.
(reparation of the sampling media is exemplified by the method described herein. This rr.~ethod or any other method producing t:he media is not intended to be limiting of the scope of the invention claimed herein.
Prepar;~tion of the Sampling Media a. preparation of TEA coating solution Ten grams of TEA (BDH, Toronto, Canada) and one gram of glycerol were dissolved in 100 ml of methanol and de-ionized {DI) water (Fisher Scientific, Nepean Canada) solution (50:50 volume). The coating solution was kept in a plastic bottle with a cap sealed with Teflon tape, and sto red at 4°C.
b. :silica gel cleaning Two hundred grams of silica ge:l (W.R. Grace & Co., Baltimore, Maryland, 22 A, 60/100 :mesh) was washed with DI water to remove fine particles. After washing, the silica gesl was transferred to several glass petri dishes and dried in a vacuum oven at 60°C and 15-mm Hg pressure for 3 hours. During drying, a small stream of room air purified by active carbon was directed at the gel in order to speed the drying process.
After drying, the silica gel was transferred to a glass column with frit at the column bottom. The column was installed in a gas chromatograph (GC) oven with 20 ml/min of helium as carrier gas. The silica gel was heated at 220°C for 24 hours, then cooled down to room temperature. The heat-treated silica gel was transferred in a glass bottle with a c:ap sealed with Teflon tape. The glass bottle was stored at 4°C.
c. Coating procedure 50 ml of each the heat-treated siilica gel and the TEA coating solution was added into a 20 crr~ (diameter) glass petri dish. After 5 minutes, the excess solution was decanted and the petri dish was placed into a vacuum oven and dried for 2 hours. The vacuum drying conditions were the same: as described above in section b. After drying, the coated silica gel was transferred to a glass bottle with a cap sealed with Teflon tape, Then, the glass bottle was put into a resealable plastic bag, sealed and kept at 4°C.
d. ~4nalytical procedure The spectrophotometric method, the flow injection analysis method and the continuous flow analysis method, are used for the nitrite analysis. These methods are well known in the art of nitrite analysis.
_g_ The novel sampling media of the present invention was tested in the laboratory in accordance with the analytical procedures referred to above.
1. Temperature study Cellulo:;e filters (Millipore, Bed:Ford, MA) coated with the same TEA coating solution and dried in th~~ vacuum oven under thc: same conditions for the sampling media prepared in accordance with Example 1 above (hereinafter referred to as "CHEMIXTM") were compared wiah CHEMIX'~M. Table 1 lists the comparison results. The comparison was conducted at -2 7 °C and 20°C., the relative humidity was about 4%, the cross diffusion barrier surface velocity was 0.5 cm/sec, and the NOZ concentrations were 30 ppb and 150 ppb.
Table 1. ;3ampling rate and temperature Nitrite Concentration (~,g/ml) at Different Temperatures Collection Media CHEMIXTM 0.97 1.10 TEA-cellulose filter 0.19 0.96 Table 1 clearly shows that the sampling; rate of CHEMIXTM changed only slightly when the temperature reduction from 20°C to -27°C, but the sampling rate for TEA coated filters decreased about 80%.
2. Sampling rate comparison 3 0 Table 1 also indicates that the C HEMIXTM has higher sampling rates than the TEA
coated filter. The CHEMIXTM collected about 5 times higher NOz than the TEA
coated filter at -27°C; the ratio was about 1.5 times at room temperature.
3. Relative humidity study Table 2 lists the sampling rate comparison of the CHEMIXTM and the TEA coated filter. The studies were conducted at 20°C, 150 ppb NOZ concentration, 0.5 cm/sec CDBS
velocity. The RHs ranged from 4% to 69%. It can be observed that the change of the relative humidity did not affect the CH:EMIXT'M sampling rate significantly, but did affect the TI~A coated filter's sampling rate.
Table 2. ;3ampling rate and relative humidity Collection Nitrite Media Concentration (~,g/ml j at Different Temperatures and Different Relative Humidities 4% 20% 40% 4% 50%
CHEMIXTM 0.95 0.96 0.99 1.08 1.12 TEA-filter 0.17 0.35 0.40 0.86 0.96 4. Stability study After e~;posing the NOZ passive sampler at 150 ppb NOZ concentration, half of the passive sampleo~s were taken out off the chamber and sealed in a resealable plastic bag which w<~s stored at -:?0°C. The rest of the passive samplers in the chamber were purged with zero air at room temperature for 5 days. The test results are shown in Table 3. The results show nc~ significant difference between the samplers in a cooler and in the chamber, which indicates th;~t the CHEMIXTM NOZ complex is stable.
Table 3. Comparison of samplers in cooler and in chamber Sampler Storing Condition Nitrite Concentration (~cg/ml) Cooler (-20C) 0.14 Chambf;r Purged with Air (20C'.) 0.14 5. Capacity study The N0, passive samplers were exposed at 16CI ppb NOz concentration, 3% RH and 20°C for one day, seven days and nine days separately. The results are shown in Table 5. It is concluded that the passive samplers c;an at least be used to monitoring 50 ppb NOZ
concentration in the atmosphere for one:-month exposure period.
Table 4. ~~apacity study Collection Nitrite Collected (~,g) at Different Exposure Time 25.5 hours 170.5 hours 203 hours Total 25.9 164.5 203.7 Per Hour 1.0 1.0 1.0 6. Practic,~l quantitative detection limit From field blank results, it is found that the pooled standard deviation was 0.1 ug of ni~.rite per blank. The practical quantitative detection limit, thus, can be taken as 1 ug per bl;~nk (10 times of the standard deviation). This is the equivalent to exposure of the passive sampler to 0.1 ppb for one month.
7. Analytical recovery study The standard nitrite solutions were spiked into the sampling media. After drying in the vacuum oven, the spiked media were extracted following the procedure described above.
The recovery vas found to be 100%.
8. Precision study The precision study is based on triplicate NOz passive sampler exposure. The pooled standard deviation was calculated. It was found the pooled standard deviation is only about 5°.~°.
9. Interference Based on other studies, a possible interference for sampling NOZ in air by using CI~EMEXTM rr~ight be peroxyacetyl nitrate ("PAN"). Other investigators have designed an experimental regime to test the potential interference of PAN and concluded that there was no sil;nificant interference from PAN when using TEA as collection media.
Claims (8)
1. Nitrogen dioxide sampling media comprising silica gel combined with triethanolamine (TEA).
2. The sampling media of claim 1 wherein the silica gel has an average pore size of about 22 Angstroms to about 150 Angstroms.
3. The sampling media of claim 1 wherein the silica gel has surface area suitable for interacting with TEA of about 400 square meters to about 700 per gram of silica gel.
4. Nitrogen dioxide sampling media comprising molecular sieve combined with TEA.
5. The sampling media of claim 4 wherein the molecular sieve has an average pore size of about 13.ANG. and surface area of about 600 square meters per gram.
6. An all-season sampler for collecting atmospheric nitrogen dioxide comprising:
(a) a sampler body having a downwardly opening cavity;
(b) sampling media disposed within the cavity comprising silica gel combined with triethanolamine (TEA) or molecular sieve combined with TEA; and (c) means for retaining the sampling media within the cavity.
(a) a sampler body having a downwardly opening cavity;
(b) sampling media disposed within the cavity comprising silica gel combined with triethanolamine (TEA) or molecular sieve combined with TEA; and (c) means for retaining the sampling media within the cavity.
7. The sampler of claim 4 further comprising a diffusion barrier and a support ring disposed between the retainer means and the diffusion barrier thereby creating an air gap between the diffusion barrier and the sampling media.
8. The sampler of claim 5 wherein the diffusion barrier is a Teflon R film.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002237133A CA2237133A1 (en) | 1998-05-07 | 1998-05-07 | Nitrogen dioxide passive sampling system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002237133A CA2237133A1 (en) | 1998-05-07 | 1998-05-07 | Nitrogen dioxide passive sampling system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2237133A1 true CA2237133A1 (en) | 1999-11-07 |
Family
ID=29275687
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002237133A Abandoned CA2237133A1 (en) | 1998-05-07 | 1998-05-07 | Nitrogen dioxide passive sampling system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2237133A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2016008802A1 (en) | 2014-07-15 | 2016-01-21 | Institut National De Recherche Et De Sécurité Pour La Prévention Des Accidents Du Travail Et Des Maladies Professionnelles (Inrs) | Device for sampling and analysing chlorinated pollutants |
| CN105823652A (en) * | 2016-05-10 | 2016-08-03 | 华东师范大学 | Passive sampling device for monitoring water dissolved-state matter and using method thereof |
| CN108225852A (en) * | 2018-01-19 | 2018-06-29 | 中国科学院合肥物质科学研究院 | A kind of air peroxy radical sampling device and the measuring instrument with the device |
-
1998
- 1998-05-07 CA CA002237133A patent/CA2237133A1/en not_active Abandoned
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2016008802A1 (en) | 2014-07-15 | 2016-01-21 | Institut National De Recherche Et De Sécurité Pour La Prévention Des Accidents Du Travail Et Des Maladies Professionnelles (Inrs) | Device for sampling and analysing chlorinated pollutants |
| CN105823652A (en) * | 2016-05-10 | 2016-08-03 | 华东师范大学 | Passive sampling device for monitoring water dissolved-state matter and using method thereof |
| CN105823652B (en) * | 2016-05-10 | 2019-01-25 | 华东师范大学 | Passive sampling apparatus and its application method for water body solubilised state matter monitoring |
| CN108225852A (en) * | 2018-01-19 | 2018-06-29 | 中国科学院合肥物质科学研究院 | A kind of air peroxy radical sampling device and the measuring instrument with the device |
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