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Lorillard

A New Method for the Determination of Nitric Oxide in Smoke

Date: 28 Oct 1968 (est.)
Length: 11 pages
81410734-81410744
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Fields

Author
Creamer, R.M.
Area
WU/LAB 8 SMOKE CHEMISTRY
Type
SCRT, SCIENTIFIC REPORT
BIBL, BIBLIOGRAPHY
CHAR, CHART/GRAPH/MAPS
DRAW, DRAWING
FOOT, FOOTNOTE
Alias
81410734/81410744
Site
G73
Named Person
Aunis
Griess
Hackney
Ilosvay
Lang
Norman
Raschig
Saltzman
Thomas
Vinson
Weidlich
Williams
Date Loaded
12 Feb 1999
Document File
81410558 /81410789 /Missing
81410559 /81410788 /Nox in Tobacco Smoke
Master ID
81410733/0744

Related Documents:
Author (Organization)
PM, Philip Morris
Litigation
Stmn/Produced
Characteristic
DRFT, DRAFT
UCSF Legacy ID
qrj40e00

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Page 1: qrj40e00
DRAfi A New Method for the Determination of Nitric Oxide in Smoke R. M. Creamer - Philip Morris Incorporated A number of methods have been suggested for the determi- nation of the small amounts of nitric oxide in smoke. In all of these methods, the nitric oxide - which is the predominant form of the nitrogen oxides in smoke - is oxidized to nitrogen dioxide before analysis. The nitrogen dioxide is then measured spectrophotometrically or colorimetrically by the Griess-Ilosvay- Saltzman, or other methods from the nitrite ion formed on trapping of the nitrogen dioxide. Both methods, however, can yield low results due to the interference of other gas phase smoke compounds. It has been found that the determination of nitrite ion iodo- metrically by the Raschig method is open to fewer interferences from other smoke chemicals. This approach has been developed into a micro method for the determination of nitric oxide in gas phase smoke. The apparatus developed for the determination of nitric oxide in smoke is shown on Slide 1. The desired number of cigarettes - usually five - are smoked on a 30 port rotary smoking machine similar to that described by Hackney, Weidlich, and Williams (1). Unlit
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DRAFT 2 cigarettes are used to block the unused ports, thus, giving a continuous flow of gas into the collection system. Cambridge filters are used to separate the particulate fraction from the smoke aerosol, and the gas phase portion is then passed on to a manifold. Here 60 ml per minute of dry air containing the desired amount of ozone is mixed with the gas phase smoke. A dilute mixture of nitric oxide in helium may also be added when it is required for calibration or spiking purposes. All gases pass into the manifold through calibrated flowmeters. The gas mixture now passes into a 400 ml glass cylinder that delays the gas for about 20 seconds. This delay permits more complete oxidation of the nitric oxide by the dilute ozoney and also helps even out the composition of the intermittent flow of gas phase smoke. The nitrogen dioxide is then washed from the gas stream in tan- dem traps that each contain 20 ml of 2 1/2% sodium carbonate solution, and the waste gas is exhausted by a vacuum pump. To minimize contamination of the laboratory air, the whole apparatus is housed in a hood. A number of the liquid and solid oxidants that have been suggested for the conversion of nitric oxide to nitrogen dioxide were tested, with poor, and varying, nitrogen dioxide recoveries. It was found, however, that the ozone suggested for this purpose by Thomas, et al (2), is the preferred oxidant. 1
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3 Aging of smoke in the presence of oxygen for this conver- sion was not investigated, as publications of other researchers have suggested that this reaction may be slow, and incomplete. Norman and Vinson (3) reported last year, however, that this oxi- dation may be complete in the case of smoke. The ozone generator used has not been descrived in the lit- erature before and, therefore, is described here in detail. The generator is shown on Slide 2. An A. Co high voltage discharge between the coaxial electrodes is used to generate the ozone. The rate of ozone formation is readily controlled by varying the cell voltage with a variable transformer. The stainless steel outer electrode appears to be permanent. The 28 gauge chrome-nickel center electrode slowly oxidizes in use and is replaced when the rate of ozone production shows a significant drop.. At rates of ozone formation of 10 microequivalents per minute or less, the ozone output is directly proportional to the cell current and none of the nitrogen in the air feed is converted to nitric oxides. The air used by the ozone generator is dried to give higher ozone yields. The substitution of oxygen for air only increased the ozone output by 60%. Air was used in all experi- ments since it provided adequate ozone. Approximately 15 microliters of 1-octanol are used as an antifoam agent. The actual volume used is adjusted to that giving the maximum permissable amount of bubble formation in order to help gas absorption.
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DRAFT 4 The solutions in the traps are analyzed for their nitrite content by the iodometric method of Raschig. Nitrite oxidizes iodide to iodine in acidic solution. This oxidation is complex and, below 25 micromoles of nitrite ion, produces about 1 microeq. of iodine per micromole of nitrite. The iodine produced is titrated with 0.005 normal thiosulfate solution. In this con- centration range the method is reproducible, linear, and is insensitive to the presence of many other smoke compounds. As has been suggested by Lang and Aunis (2), the titration must be conducted in a completely oxygen free atmosphere, since the nitric oxide formed during the titration must not be reoxidized. There is an optimum anount of ozone for any given amount of nitric oxi.de. This shown on Slide 3. It will be seen that the maximum amount of N02 is recovered when just enough oxidant has . been added to convert the NO to NO2 Dilute mixtures of nitric oxide in air were used to calibrate the efficiency off recovery of the process. Known amounts of nitric oxide that were added to gas phase cigarette smoke were quantita- tively identified. Slide 4 shows the interdependence of N02 recovery from smoke and the amount of 03 added. Gas phase smoke contains materials that compete with the NO for the ozone and in consequence a larger amount of 03 must be used than t`hat required to oxidize the NO. Gas phase m N .L~ . ~ O .~ `
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DRRTI 5 smoke, however, buffers the effects of an excess of ozone on the NO and makes the concentration of ozone in gas phase smoke less critical. than that observed with synthetic test mixtures. Some compounds that interfere with the determination of the nitric oxide in smoke were reported last fall by Norman and Vinson. However, iff the nitrite is determined iodometrically with 03 as an oxidant, the addition of 1,000 micrograms of either acetaldehyde or isoprene or 100 micrograms of hydrogen sulfide per cigarette to gas phase smoke has little effect on the nitric oxide recovered. With the apparatus that has been described, and at the reactant concentrations used, negligible amounts of organic oxidants were formed from the cigarette gas phase. The amount of ozone is, of course, adjusted to its optimum concentration. With this method of analysis for nitric oxide, data that are consistent are obtained. Some comparative data obtained with the same cigar.ett;e rod but different filters is shown on Slide 5, The carbon filter does lower the nitric oxide in the filtered smoke, but the acetate filter does not. The infrared analyses are based on the adsorption spectra of gas phase smoke at 1600 cm-1 wave number. The relative standard deviation for a number of analyses on the same cigarette was .3.5%. The method described here thus gives rapid, consistent and reproducible analyses and has fewer problems with interferences than do other methods described for the analysis of nitric oxide in smoke.
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DR~.~ ~ 6 REFERENCES 1. Hackney, E. J., Weidlich, W. R., Williams, J. B., Tobacco Science IX, 112 (1965). 2. Lang, F. M., Aunis, G., Chim. Anal. 32, 139 (1950). 3. Norman, U., Vinson, R. R.: 21st Tobacco Chemists' Research Conference, Durham, North Carolina, October, 1967. 4. Thomas, M. D., et al., Anal. Chem. 28, 1810 (1956). ~.+ 4 .6 a ~.+ ~ ~ CD
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ROTARY SMOKING MACHINE r rY-,~- b`l I~l I~J~ m CAM RIDGE U U ~ U FILTERS CARBONATE TRAPS OZONEGENERATOR He-NO ~ MIXTURE HIGH VOLTAGE ' COS04 DRYING TUBE VACUUM PUMP APPARATUS FOR NITRIC OXIDE ANALYSIS
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28 GAUGE CHROMEL A WIRE ~ S S TUBI NG R a 30~ ~- J 1.9 cm OD, 1.65 cm I D POLI SHED BORE 2.8cvn 12.7 cm ® VAR IABLE TRANSFORMER ~u AMP AC PHTHALATE RESI N S EALS v ._ ;: ~ I MEGOHM 20 WATT S Y 12 KV NEON SIGN TRANSFORMER OZONE GENERATOR ~vz,OTt~iB GLASS SHELL
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NITRIC OXIDE RECOVERI ES AT VARYING OZONE INPUTS- SYNTHETIC MIXTURES .~L 11 .0 .0 . -3,
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300 Ng NITRIC OX IDE 200 PER CIGARETTE 100 - M L I I f 10 20 30 40 Aj EQUIVALENTS OZONE/CIGARETTE NITRIC OXIDE RECOVERIES FROM SMOKE AT VARYING OZONE INPUTS ,~ a ~ . ~ Zb w

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