Organic acids in a selective Dialysate of air particulate matter*

VOL. 2 (1959)

JOURNALOF

ORGANIC DIALYSATE ETHEL Public

CHROMATOGRAPHY

ACIDS

OF AIR

IN

615

A SELECTED

PARTICULATE

D. BARBER, l?RANCIS AND LAWRENCE

MATTER*

T. FOX, JAMES M. MARSHALL

P. LODGE

Health Sevvice, U. S. Department of Health, and Welfave, Cincinnali, Ohio (U.S.A.)

During chromatographic studies of the air particulate matter from urban air, it became increasingly apparent that the variations in composition of the organic acid fraction, as well as the complexity of the air sample, made the interpretation of chromatograms unduly involved. While the method of CORCORAN~ had more than adequate. detailed

resolving knowledge

of the sample

power

for

of the nature

for chromatography

aliphatic

acids

from

of the carboxylic a trial

and

error

C,

acids

to

CL02, the

in the air made

process.

absence

of

any

the preparation

To overcome

this difficulty

selective dialysis2 was used so that a given air sample, after dialysis, could be chromatographed in stages. Since the more rapidly dialysing solutes have the lower molecular weights, each stage of the chromatographic sample increases progressively with respect to the molecular weight of its organic acid components. The present report is concerned with the application of such selective dialysis to five air particulate samples from the National Air Sampling Network of the Community Air Pollution Program, This study was confined to one sample of each of five selected cities, and to the twohour dialysate of the sodium hydroxide extract of the organic acids of these samples,

PROCEDURE

An amount of the glass filter containing approximately ISO mg of air particulate matter was cut into rectangles having an area of approximately one-sixteenth square inch. The sample was placed in roo-xgo ml of 0.05 N sodium hydroside solution, and the mixture was shaken mechanically. In order to determine the time recluired for maximal recovery of the acids from the particulate, quantities of HWOOH of known specific activity as the sodium salt were added to particulate matter, and the amount of naturally occurring acid extracted was deduced by the isotope dilution principle. Since 5.5 hours was found to be sufficient time for such extraction, the extract was decanted through a filter of glass wool after this interval of time. IO ml of the filtrate were placed in a cellophane dialyzing bag having a diameter, when round, of Ig mm, CRAIG’S

procedure

of selective

dialysis

was

followed,

and

the

alkaline

* Paper presented at the Symposium on Air Pollution at the 134th National American Chemical Society, September 7.-12, 1958, Chicago, 111. Refevemes

p. 6rg.

extract Meeting

of the of the

E. D. BARBER et al.

616

VOL. 2

(1959)

particulate, reduced by evaporation to a volume of IO ml, was dialyzed against IOO ml of water. The dialysate collected after 2 hours was used. for these studies with the exception that the material used in the isotope studies with aniline-ldC described ‘*% below employed a 2+hour dialysate. Dialysates in all cases were taken to dryness “” under moving warm air. The dried residue (sodium salts of the organic acids) was dissolved in from 0.3 to 0.8 ml water, acidified to approximately pH 2 (or lower) with glycine buffer and/or I-I HCl.The acidified solution, having a volume between 0.5 and I,O ml was mixed with o.G to 1.2 g of silicic acid and stirred. This mixture was suspended in chloroform and placed on the top of a silica gel column of such mass that the combined weight of the silica mixed with the sample and used for the column was 3.0 g. Silica gel chromatography followed the procedure of CORCORAN~ except that gradient elution4 was employed and the aqueous phase was glycine buffer pH 2 exclusively. The first effluent chromatographic zone, a possible mixture of aliphatic acids having more than 3 carbons, was examined qualitatively by reacting these carboxylic acids with aniline -1% . When the reaction mixture was chromatographed mobility of according to DE JONGE~, ra.dioautographs charted the chromatographic the resulting anilides. Two samples of soot from burning propane and toluene, kindly furnished by Professor B. D. TEBBENS, University of California, were extracted, dialyzed and chromatographed according to the procedure described above for the air particulate matter. RESULTS

The data of Table isolated H14COOH

AND DISCUSSION

I indicate that the specific activity of the chromatographically does not decrease after 5.5 hours. Obviously, therefore, the conTABLE

SPECIFIC

ACTIVITY OF

OF AIR

INTRODUCED

PARTICULATE

l-114COOH* MATTER

WITH

Time (It)

2

l

*

5.P

24

*t*

I AFTER 0.05

SEVERAL, N

SODIUM

PERIODS

OF

EXTRACTION

HYDROXIDE

Specific aclivily

1910

1903 1880 1553 1618

1565 1560 1750

.

+ Specific activity, 12,940cts/mmole. y’ With mechanical shaking. * * * 6 h shaking, 12 h standing and 6 h shaking.

,centration of inert, naturally occurring formic acid in the extract does not increase, and ,thereby dilute the introduced radioactive organic acid after 5.5 hours. This Refevemes

p, 6rg.

VOL.

2

(1959)

ORGANIC

ACIDS

IN AIR

P:~RTICULATE

MATTER

617

relatively simple extraction procedure for these acids argues against the use of more drastic methods involving heat for such estraction purposes. Chromatograms from the z-hour dialysates from the selected air samples appear in Fig. I. It is clear that all the samples are different with respect to the concentration of organic acids in the s-hour dialysate. The two that are most nearly alike are the Cincinnati and the Racine samples and even these differ with respect to two factors. The first of these factors is that the acidity of the first 44 ml of the effluent of the Racine sample indicates the presence of acid solutes while the corresponding portion I

I

I

Ii

II

I

I

CORPUS

CHRIST1

I

-

g2 -

_

I 40

I 60

I 60 EFFLUENT,

I 100 ML

CINCINNATI

--..

ri

... __.-

I-

-__

i------T--

I

E

FT. WAYNE

w2

I,_1

20

1

I

I

I I20

1,:

20

20

40

I.

40

60

60

60 EFFLUENT,

100

I 120

ML,

EFFLENT,

100

120

ML

Fig. I. Chromatographic representation of the acids emerging from silica gel columns from 2-h clialysates of 5 samples of air particulate matter. 3-g silica gel columns were employed with an aqueous phase of glycine buffer ~13: 2. The mobile phase consisted of butnnol admixing with chloroform in a 3oo-ml mixing vessel. Plots express the data on the basis of 200 mg of air particulate matter. Samples are identified by the National Air Sampling Network as: Cincinnati, bvayne, 12660; Pasadena, 15832; Racine, 12484. 12106; Corpus Christi, 12153, 12173, 12172; FOd References

p.

Grg.

E.

618

D.

BARBER

et

al.

VOL.

2

(1959)

of the effluent from the Cincinnati air is apparently free of such solutes. The second ,,i, factor is that, while the acidity between the 76th and 96th effluent ml is approximately 1.5 times that. between fractions 44 and 62 for the Cincinnati particulate, the car- ,,,’ responding zones are nearly equal for the dialysate from Racine. The acidity residing within the 76th and 98th ml has been shown 2 to be that of formic acid by microdiffusion studies, while that of the zone between fractions 45 and 68 is acetic acid with a carboxylic acid contaminant. On a weight basis, the formic acid concentration as determined by this method is 1.52 pg/rns for Cincinnati and 0.52 &x-n3 for Racine. The impure acetic acid fraction, calculated as acetic acid, corresponds to I.19 /&g/m3for Cincinnati, and 0.58 pg/m3 for Racine. Acetate and formate are lcnown at7 to occur in air, and their presence in air would be expected as combustion products. BUSKYE, WILDER AND HOBBS showeds that these two acids accounted for over 65% of the titratable acidity of the effluent from burning tobacco. On the other hand, the burning of simple fuels such as propane or

20

I

I

I

I

30

40

60

60

I 70 EFFLUENT,

ml

I

I

EO

SO

100

110

I20

PROPANE

20'

I

I

30

40

1

I

JO

60

I EFFLU7iNT,

I

I

I

I

60

90

100

110

120

ml

Fig. 2. Chromatographic representation of the z-h dialysate from the particulate matter from burning toluene and propane. Chromatographic details are the same as those for Fig. I except that the data are expressed on the basis of 500 mg of particulate matter.

toluene was evaluated through selective dialysis. Fig. 2 shows that the greater part of the titratable acidity of the selected dialysate does not reside in acetic and formic acids. There is the possibility that these acids are liberated in appreciable quantities, on the combustion of these fuels, but they are not adsorbed or otherwise bound by References

p. 6x9.

,++

VOL.

2

(1959)

ORGANlC

ACIDS

IN

AIR

PARTICULATE

MATTER

6x9

the particulate constituting the soot. The basic difference between the simpler acid patterns (Cincinnati and Racine) as contrasted with the more complex (Corpus Christi, Fort Worth and Pasadena) could also reflect chemical interaction of the components of air as well as their source. Therefore it seemed worthwhile to critically evaluate the particulate collections from Racine and Cincinnati in order to decide the validity of the similarity suggested by the above data. When pooled samples representing the acidity of the first 35 ml of the Racine and Pasadena samples were reacted with aniline -l*C, the radioautographs showed no distinct spots at the known RF values for the anilides of aliphatic acids having from 3 to IO carbons atoms. A single spot near the front appeared on the radioautograph from the described chromatographic zone of the Pasadena sample and the chemical nature of this anilide is being investigated. SUiMNlARY

of acids from air Because of the difficulty of interpreting partition chromatograms particulate samples, selective dialysis through cellophane was investigated as a means of simplifying the elution patterns. Five samples of particulate matter collected on glass fiber filters, and two samples of soot from the combustion of simple fuels were analyzed. The procedure consisted of extraction, dialysis, and column chromatography, followed by paper chromatography of radioactive anilides of unresolved portions of eluate. The results are presented, together with evaluation of the technique, and recommendations for further study. REFERENCES

1 G. B. CORCORAN, Anal. Chem., 28 (1936) 168. 2 I?. T, Fox AND L.M. MARSHALL, Intern.J.Air Pollution, I (1959) 163. 8 L. C. CRAIG AND T. P. KING, J. Am. Chem. SOL, 77 (1955) 6620 ; L. C. CRAIG, T, P. KING AND A. STRACHER, J. Am. Chew Sot., 79 (1957) 3729. 4 I<, 0. DONALDSON,V. J, TULANE AND L. M.MARsHALL.Aw~Z.C/J~~., 24 (1952) 6 A. I?. DE JONGE. Rec. Irav.~lti~?z., 74 (1955) 760. 0 B. D. TEBBIZNS AND J.D.Ton~~~,Science, 120 (1954) 662. 7 P. P. MADER, G. CANN AXD L. PALMER, Plant Physic%, 30 (1955) 318. * D. A. BUSICYE, P. WILDER AND M. E. HoBBs,A~~Z. C/tern., zg,(Ig57)105.

Received

773.’

February

23rd, Igsg