Anal. Chern. 1982, 5 4 , 1221-1224
a t mole fractions of phosphate C0.02.
LITERATURE CITED Jean, M. Chlm. Anal. 1955, 3 7 , 125-133. Strickland, J. D. H. J . Am. Chem. SOC. 1952, 7 4 , 862-867. Strlckland. H. ,I Am. . Chem. Soc. 1952. 74. 888-871. - - - - J. - -0’. Strickland, J. 0.H. Am. Chem. SOC. 1952, 7 4 , 872-878. Keggin, J. F. F’roc. R. SOC. London, Ser. A 1934, 744A, 75-100. (8) . . Matsumota. K. Y.: Kobavashi. A.: Sasaki, Y. Bull. Chem. Sac. Jpn. 1975, 4 8 , 3146. (7) KasDrzak, M. 8.; Leroi, G. E.; Crouch, S. R. Appl. Spectrosc., in press. (8) Launay, J. P.; Massart, R.; Souchay, P. “Chemistry and Uses of Molybdenum”; IMltchell. P. C. H., Ed.; Climax Molybdenum Co.: 1979; pp 71-70. (9) Kasprzak, M. I;.; Crouch, S. R.: Leroi, G. E. Appl. Spectrosc. 1978, 3 2 , 537-540. (10) Hargis, L. G. A,nal. Chem. 1970, 4 2 , 1494-1497. (1) (2) (31 -, (4) (5) I
.
3.
1221
(11) . . Truesdale, V. W.: Smith, P. J.; Smith, C. J. Analyst (London) 1979, 104, 897-918. (12) Halasz, A.; Pungor, E.; Polyak, K. Talanta 1971, 78, 577-588. (13) Truesdale. V. W.; Smith, C. J. Ana/yst (London) 1976, 707, 19-31. (14) Klrcher, C. C.; Crouch, S. R. Anal. Chem. 1962, 5 4 , 879. (15) Ingri, N.; Kakolowlsz, W.; Sillen, L. G.; Warnqulst, B. Talanta 1967, 74. 1261-1286. (16) Aveston, J.;Anacker, E. W.; Johnson, J. S. Inorg. Chem. 1964, 3 , 735-746. (17) Ingle, J. D., Jr. Thesls, Michigan State University, East Lansing, MI, 1971.
RECEIVED for review December 14,1981. Accepted February 22, 1982. The authors gratefully acknowledge the National Science Foundation through a graduate fellowship (C.C.K.) and Grant No. CHE 79-26490.
Collection Efficiencies of Cartridges and Microimpingers for Sampling of Aldehydes in Air as 2,4-Dinltrophenylhydrazones Danlel Grosjean‘ and Koch1 Fung Environmental Research & Technology, Inc., 2625 Townsgate Road, Westlake Village, California 9 136 1
The determination of low levels (typically parts per billion) of formaldehyde and other aldehydes and ketones in air is of importance in a number of areas of pollution control including indoor pollution, industrial hygiene, characterization of industrial effluents, modeling of ozone and other photochemical oxidants, and research in atmospheric photochemistry. However, due to a large extent to the limitations inherent to the analytical methods employed to date, there is a paucity of data Concerning levels of carbonyls in the air environment (1).
Recently, several investigators have applied high-performance liquid chromatography (HPLC) to the determination of formaldehyde (2-9) and of other carbonyls (3, 4 , 7-9) in polluted atmospheres. This method entails the selective reaction of airborne carbonyls with the reagent 2,l-dinitrophenylhydrazine (DNPH)
(NO2)ZCGH3NHFJH, + RCHO HzO + (NOz)zCeH3NHN=CHR -+
and the subsequent separation and quantitation of the corresponding 2,4-diinitrophenylhydrazonesby HPLC. Several sampling devices have been employed, including microimpingers containing DNPH solutions (3,4, 7-9), cartridges with DNPH coated on a solid support (6, IO),cryogenic concentration ( I I ) , and DNPH solutions in rotating flasks (5). In spite of the critical importance of establishing the collection efficiency (ICE) of these DNPH-sampling devices, there is virtually no information concerning CE studies in the range! of concentrations and conditions directly relevant to atmospheric sampling. In this study, we have investigated the collection efficiencies of several cartridges and microimpingers for three representative carbonyls, formaldehyde, acetaldehyde, and benzaldehyde. Parameters studied included aldehyde concentration, sampling volume, time and flow rate, matrix air humidity, and addition of organic solvents to the aqueous DNPH reagent.
EXPERIMENTAL SECTION Cartridges consist of 100 mm long X 6 mm i.d. glass tubes packed with 20 mesh, HF-etched glass beads impregnated with DNPH reagent. The DNPH reagent consists of aqueous, acidic (HsPO,) saturated solutions of DNPH to which small amounts of poly(ethy1ene glycol) are added. The glass beads are immersed in the DNPH reagent, and the water is slowly evaporated. The 0003-2700/82/0354-122 1$01.25/0
purpose of adding poly(ethy1ene glycol) is to promote the formation of a viscous film on the bead surface. Once packed with glass beads and plugged with glass wool, the cartridges are sealed with plastic caps and stored in the dark at refrigerator temperature prior to sampling and prior to extraction and HPLC analysis. Microimpingers (e.g., Kontes No. K737550 midget impingers) contain 10 mL of‘ aqueous, acidic (2 N HC1) DNPH reagent to which 10 mL of an HPLC-grade organic solvent can be added. Organic solvents employed to date include n-hexane and a 9:l by volume mixture of cyclohexane and isooctane. Storage prior to and after sampling is in the dark at refrigerator temperature. Blanks are included in each batch of cartridges and impingers prepared and are subjected to the same handling and analytical protocol employed for the actual samples. Collection efficiency studies are carried out by using a dynamic dilution system. Mixtures of 1ton of the carbonyl to be studied (as measured by a 0-20 torr Wallace and Tiernan absolute pressure Nz, or purified air, are prepared in a gauge) in -780 torr of 02, 22-L Pyrex bulb. After allowing 1-3 h to ensure complete mixing, these mixtures are diluted in a flow system using calibrated rotameters and capillary flow meters. Carbonyl concentrations of 100-300 ppb in the diluent gas are typically employed. After -1 h of flowing this mixture at a flow rate of -5 L/min, sampling is initiated. Samples are typically collected at a sampling flow rate of 1.0 f 0.2 L/min, and the volume sampled is monitored by a wet test gas meter connected to the exit of a Metal Bellows sampling pump. The diluent gas stream can be humidified to -4040% relative humidity by passing this diluent gas stream through a bubbler containing distilled water. Formaldehyde B i prepared by heating paraformaldehyde (>95% purity) at 373 K under vacuum and passing the effluent gases through a methanol/liquid-nitrogen slush tap (179 K) to remove Hz0 and possible disproportionation products, and formaldehyde is collected in a trap at 77 K. Acetaldehyde is degassed under vacuum and distilled into an ethanol/liquid nitrogen slush trap (156 K) and thence to a liquid nitrogen trap (77 K) under vacuum. Benzaldehyde is degassed under vacuum. Cartridge and impinger samples were analyzed by HPLC as described by Fung and Grosjean (2). Reference 2 could be consulted for a more detailed description of the analytical method and of its quantitative aspects including reproducibility, calibration, and nanogram detection limits.
-
RESULTS AND DISCUSSION Our studies included five collection devices (two cartridges and three impingers), three diluent gases (02, Nz, and air), 0 1982 American Chemical Society
1222
ANALYTICAL CHEMISTRY, VOL. 54, NO. 7, JUNE 1982
Table I. Summary of Aldehyde Collection Efficiency Studies cartridgesa
c,
C humid
impingers
dryd
11
humid
dry
humid
12
dry
humid
Formaldehyde 0 9 2 + 12
99+13
80
dry
humid
dry
89
111 + 1 8
101 i 27
86+ 3
31+ 9
90 + 0.5
5f 3-1 2
5f 3-1 2
2
2
8 6-7.7
1
6
5 6-6.7
1
6
6
6
5 6-7.7
3 6-1 0.6
270-300
255-333
333
222
164-339
126-321
250
333
169-333
117-320
1.1-4.4
1.2-4.9
2.4
1.6
1.4-2.5
1.0-2.6
1.8
2.4
1.4-2.4
1.5-2.3
15-60
16-66
32
22
19-34
13-35
24
32
19-32
20-31
collection efficiency, % no. of samples volume sampled, L nominal concn, ppb nominal loading, p g equiv ambient concn, ppb
38i.4
38+2
8
6
4' 6-6.4
140-193
collection efficiency, % no. of samdes volume sampled, L flow rate, L/min nominal concn, ppb nominal loading, p g equiv ambient concn, ppb
collection efficiency, %e no. of samples volume sampled, Lg nominal concn, ppb nominal loading, pg equiv ambient concn, ppb
Benzaldehyde 29 + 0.5
28 + 0.5
94 + 2
2 6
2 6
2 6J
182-243
100-105
94
81-97
3.7-5.1
4.8-6.4
2.6-2.7
2.5
2.1-2.5
14-20
18-25
10-11
10
8-1 0
1-24'
12-89'
Acetaldehyde 91 + 18l 5 6 + 33
5 0 + 28
115
82t 7
63t 5
12m 0.5-12
24 0.05-198
8 12-49
5 6-6.7
9 6-1 2
1 6
2 5-6.5
2 6.1
1.0
0.05-1.9 67-956
1.0 190
1.0 158-400
0.7-1.4 149-330
1.4 300
1.0
188-320
203-400
1.0 156-300
0.17-4.1
0.08-31.4
3.7-19.2
1.7-4.8
1.6-4.1
3.2
1.8-4.7
1.7-3.3
1.5-37
0.7-290
34-176
16-44
14-37
29
16-43
15-30
a C = cartridge as described in text. C, = cartridge with smaller size glass beads (60 mesh) and more DNPH reagent and poly(ethy1ene glycol) than cartridge C. b I, = 10 mL of 2 N HCl aqueous DNPH. I2 = I, t 10 mL of n-hexane. I, = I, + Relative humidity
