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Determination of ammonia in tobacco and tobacco smoke with an ammonia electrode
&alyfica Cllinuka Actu. 69 ( 1974) 243-247 0 Elsevicr Scientific Publishing Company.
SHORT
- Printed in The Netherlands
of ammonia in tobacco and tobacco smoke with an aminonia electrode
H. SLOAN
and GERALD
P. MORIE
Research Ltrhortrrurks. T~~~ncs.s~~c~ Eosrmtr~ Con~pm_v (Division Terrnesstw 37662 (U.S.A.) (Reccivcd
243
COMMUNICATION
Determination CEPHAS
Amstcrdnm
17th September
oj’ Etr.s!r~~rrtr Kocld
Co~nprory). K ingsport.
1973)
Many classical analytical methods have been described for the determination of ammonia in various matrices l - 4 , but few of these are suitable for the determination of ammonia in tobacco or tobacco smoke. Such determinations usually involve distillation of the ammonia and subsequent titrimetric or calorimetric measurementsS-8. The distillation and titration methods are generally tedious, timeconsuming, and non-specific. A gas-chromatographic method9 overcomes some of the problems, but still requires a lengthy separation step to isolate the ammonia from the bulk of the sample. In view of the complex compositions of both tobacco and smoke, the need for a simple technique for determining ammonia in these materials was indicated. This paper describes a method in which an ammonia electrode is used for determining ammonia in tobacco and tobacco smoke. Experimental Apparatus. An Orion Model 95-10 ammonia electrode was used in conjunction with the Orion model 407 specific-ion meter. The cigarettes were smoked by a one-port syringe-type smoking machine which was made in these laboratories. The machine was adjusted to operate at standard conditions (one 35-ml, 2-s puff per min). An all-glass steam distillation unit of 125-ml capacity was used. Reagents. Ammonia calibration standard solutions of 0.1 p.p.m. ammonia, 1.0 p.p.m. ammonia, and 10 p.p.m. ammonia were prepared from reagent-grade ammonium chloride. Buffer solution was prepared by dissolving 10.2 g of dipotassium hydrogenphosphate and 4.8 g of borax in 1 1 of ammonia-free water. The alkaline solution used in conjunction with the buffer solution was prepared by dissolving 5 g of borax in 100 ml of 0.5 M sodium hydroxide. Cigarettes mtiji’lters. The cigarettes used were two domestic brands (tobacco blends), one European brand (dark tobacco), and two non-commercial types (burley tobacco and flue-cured tobacco). One of the domestic brands was an 85-mm filter cigarette and the other an 85-mm non-filter cigarette. All cigarettes were conditioned at 60% relative humidity at 75°F for 48 h before use. Filters examined for their capacity to remove ammonia from cigarette smoke were:
SHORT COMMUNICATION
244
1. Cellulose acetate: 1.6 den. per II.. 48.000 total den. tow; length 20 mm; 2.7 in. pressure drop. 2. Paper: length 20 mm with 2.5.in. pressure drop. 3. Cellulose-acetate-activated carbon ( 100 mg)--length 20 mm. 3.0 in. pressure drop. (Carbon was held in place with two 7.5 mm. 3.3 den. per fil.. 44.000 total den. cellulose acetate rods.) 4. Cellulose acetate: 3.3 den. per lil.. 44,000 total den. tow: treated with an acidic additive. 20 mm length. 3.0 in. pressure drop. 5. Cellulose acetate: high efliciency. 1.6-den. per fil. tow. 25 mm length, 2.4 in. pressure drop. Detrrwirltrtim oJ’ ctmmmia irl tobacco. Place a weighed sample of tobacco ( 100-200 mg) in a steam-distillation flask. To the flask add 20 ml of buffer solution and 5 ml of alkaline solution, steam-distil. collecting the distillate (80 ml) in 10 ml of 0.1 M hydrochloric acid and then dilute to 100 ml with distilled water. Transfer the solution to a 250-ml beaker, and stir at the rate established during calibration of the instrument with the known samples. Dip the ammonia electrode in the solution. and add 2 ml of aqueous 10 M sodium hydroxide. Read the previously calibrated meter directly in p.p.m. ammonia. Calculate the percentage of ammonia in the tobacco from the concentration in solution, volume of solution, and weight of the tcbacco sample. Deterrnirltrtiotl qf’unmot1i~~ irl cigcmt te SItlOliL’.Two cigarettes were smoked to 27-mm butt lengths under standard conditions, the smoke then being passed through a scrubber flask containing 50 ml of 0.1 M hydrochloric acid to collect the ammonia. Transfer the coptents of the flask to a steam-distillation unit and add 2 ml of aqueous 10 M sodium hydroxide. Steam-distil until about 80 ml of distillate has collected in a lOO-ml volumetric flask containing 10 ml of 0.1 M hydrochloric acid. Fill the flask to the mark with distilled water, and transfer the solution to a 250-ml beaker. Stir at the predetermined rate, add 2 ml of 10 M sodium hydroxide. and read the amount of ammonia in p.p.m. directly from the previously calibrated meter. Calculate the amount of ammonia per cigarette from the ml of distillate. p.p.m. of ammonia, and number of cigarettes smoked. The precision was determined from 7 repeat analyses. The percentage of ammonia removed from the tobacco smoke by various filters was based on the amount of ammonia delivered by a control cigarette equipped with a length of tobacco column equal to that of the test filter. Compwiso~~ of’ the electrotle r7wtlwtl with CI ~trs-chr.onlatog~~tpl~i~ method. To evaluate the accuracy of the electrode method, the ammonia in the tobacco and tobacco smoke from a non-filter cigarette was determined by a gas-chromatographic method similar to that described by Ayers’. An 8-ft x& in stainless-steel column packed with Chromosorb 103 was used; the column temperature was controlled at loo”, and a thermal conductivity detector was used. The method for collection of the ammonia was identical to that described above. but it was necessary to concentrate the acidic steam-distillate until the ammonia concentration was about 20 p.p.m. Results
mci tliscussio~~ Anwoniu corltent
oj’ cwrimrs
cigarette
tohawos.
The ammonia
contents
of
SHORT
245
COMMUNICATION
several tobaccos used in cigarettes are shown in Fig. 1. The cigarettes made from dark tobacco contained 0.48’;/, ammonia which was the highest of the commercial cigarettes tested. Cigarettes made from burley tobacco contained 0.31”/, and those prepared from flue-cured tobacco contained 0.11(x, ammonia. The blended tobacco of the non-filter domestic cigarette contained 0.14”/;: ammonia, and the blended tobacco of the filtered domestic brand contained 0.11% ammonia.
Fig. 1. Ammonia
content
of various
Fig. 2. Ammonia
content
of smoke
cigarcttc from
tobaccos.
various
cigarcttcs.
Amnonict in the w~olze of ocwious cigarettes. The smoke from the dark tobacco cigarettes contained 153 /cg of ammonia per cigarette (Fig. 2). Smoke from the burley and the flue-cured tobacco cigarettes contained 102 jig and 51 pg of ammonia per cigarette, respectively. Smoke from the non-filter, blended-tobacco cigarettes contained 67 /rg of ammonia per cigarette while smoke from the filter in blended-tobacco cigarettes contained 36 ,ug of ammonia per cigarette. The lower amount of ammonia in the smoke of the filter cigarettes was primarily due to ammonia removal by the filter. Removtrl qJ‘ummorrin ji*ont cigarette smoke by ji’lters. The amounts of ammonia removed from cigarette smoke by certain filters are shown in Table I. The most efficient filter for removing ammonia from smoke was the high-efficiency cellulose acetate lilter. l.The ammonia in cigarette smoke is present as the ammonium ion. This is indicated” b y the pH of cigarette smoke, which ranges from 5.4-6.4. In Fig. 3 FRACTION OF EACH SPECIES
PI I OF SOLUTION
Fig. 3. Frxtion
or NH,+ and NH3 LS. pH;(A)
NH;;
(0)
NI-I,.
246 TABLE
SHORT
COMMUNICATION
I
EFFIClEl\fCY (The tobacco
FILTERS
FOR
used contained
OF
0.147;
REMOVING
AMMONIA
FROM
CIGARETTE
SMOKE
ammonia)
-. Filter
Tobacco Cellulose xet;1te” Cellulose acctutcL Paper Acctatecarbon’ Acctateadditive”
Pressctrc drop (in )
A t,rtuoriitr ck4irer.v (j(g)
0.6 2.4
67 47
3.1
27
2.5 3.0
39 38
3.0
36
u Regular acetate filter: acct;1tc plugs: ’ xctatc
* high-cflkicncy liltcr containing
acetate filter: C 100 mg uctivatcd ;I polyol and an acidic additive.
-.
carbon
between
two 7.5-mm
The ammonia in cigarette smoke is present as the ammonium ion. This is indicated” by the pH of cigarette smoke, which ranges from 5.4-6.4. In Fig. 3 the fraction of ammonium and ammonia are plotted us. pH. In the pH range of cigarette smoke, the amount of unprotonated ammonia is negligible. Therefore, ammonia in cigarette smoke is primarily ammonium ion entrained in the particulate phase, and the amount of ammonia removed by a filter roughly parallels the amount of total particulate matter removed by a filter. This observation is further supported by the fact that the filter containing activated carbon did not selectively remove the ammonia from cigarette smoke. Accrtracy md precision. The precision of the method was determined from the repeated analyses of the smoke from the domestic brand 85-mm non-lilter cigarette. The mean delivery of ammonia was 67 pg with a standard deviation of 2.2 and a coefficient variation of 3.3(x. An attempt was made to compare the results with those obtained by the classical Nessler method4. However, several compounds in tobacco smoke interfered with the Nessler method, even after steam distillation of the sample. A gaschromatographic method. similar to that of Ayers”. was used to obtain a measure of the accuracy of the method. This method was less sensitive than the electrode method, and it was necessary to concentrate the acidified steam-distillate about 20-fold; the average amount of ammonia found in the smoke of the non-filter cigarette was 67 pg which is identical to the 67 ,ug obtained with the electrode method. The gas-chromatographic method was also used to determine the ammonia content of tobacco; the amount found was 0.13?/,, which agreed very closely with the O.140/0 obtained by the electrode method. Ejjtct oJ’ cmines OII electrode response. Amines were the compounds which were most likely to interfere with the electrode response during the ammonia determinations. No interference was observed when methylamine was added in
SHORT
COMMUNICATION
247
amounts equal to the ammonia concentration. It was therefore concluded that the relatively low amounts of amines in cigarette smoke (lo-15 ,ug of methylamine)” would not significantly affect the ammonia determination. REFERENCES 1 2 3 4 5 6 7 8 9
10 I1
J. W. Howell and D. F. Boltz. Aflu/. C/I~I,I., 36 (1964) 1799. D. Midgley and K. Torrance. Anc~Iysf (Lodo~r). 97 ( 1972) 626. 633. J. M. Brcnner and D. R. Kenncy. Ar~ul. Chinr. Acre. 32 (1965) 485. M. Hahn, Ge.str!?d/,. I/r{/.. 3 I (1910) 693. G. W. Pucker, H. G. Vichery and C. Lcavcnworth, I&. Eng. Chent.. Anul. Ed.. 7 (1935) 152. Chemists’ Rcscarch Confcrcncc J. F. Williams and G. F. Hunt. presented at the 21st Tobacco Durham. Enplnnd. 1967. J. R. Newsomc and C. H. Kicth. Tobacco Sci.. 9 (1965) 65. P. F. Collins. W. W. Lawrence and J. F. Williams, Beifr. Tcrhcr/iJiwsch.,6 (1972) 167. C. W. Ayers, Tuiutrm, 16 (1969) 1085. A. J. Sensabaugh and R. H. Cundiff, Tobacco Sci.. 1 I (1967) 25. H. Elmenhorst and Ch. Shultz Beifr. Tnha,kforsc/r.. 4 (1968) 90.
at
SHORT
- Printed in The Netherlands
of ammonia in tobacco and tobacco smoke with an aminonia electrode
H. SLOAN
and GERALD
P. MORIE
Research Ltrhortrrurks. T~~~ncs.s~~c~ Eosrmtr~ Con~pm_v (Division Terrnesstw 37662 (U.S.A.) (Reccivcd
243
COMMUNICATION
Determination CEPHAS
Amstcrdnm
17th September
oj’ Etr.s!r~~rrtr Kocld
Co~nprory). K ingsport.
1973)
Many classical analytical methods have been described for the determination of ammonia in various matrices l - 4 , but few of these are suitable for the determination of ammonia in tobacco or tobacco smoke. Such determinations usually involve distillation of the ammonia and subsequent titrimetric or calorimetric measurementsS-8. The distillation and titration methods are generally tedious, timeconsuming, and non-specific. A gas-chromatographic method9 overcomes some of the problems, but still requires a lengthy separation step to isolate the ammonia from the bulk of the sample. In view of the complex compositions of both tobacco and smoke, the need for a simple technique for determining ammonia in these materials was indicated. This paper describes a method in which an ammonia electrode is used for determining ammonia in tobacco and tobacco smoke. Experimental Apparatus. An Orion Model 95-10 ammonia electrode was used in conjunction with the Orion model 407 specific-ion meter. The cigarettes were smoked by a one-port syringe-type smoking machine which was made in these laboratories. The machine was adjusted to operate at standard conditions (one 35-ml, 2-s puff per min). An all-glass steam distillation unit of 125-ml capacity was used. Reagents. Ammonia calibration standard solutions of 0.1 p.p.m. ammonia, 1.0 p.p.m. ammonia, and 10 p.p.m. ammonia were prepared from reagent-grade ammonium chloride. Buffer solution was prepared by dissolving 10.2 g of dipotassium hydrogenphosphate and 4.8 g of borax in 1 1 of ammonia-free water. The alkaline solution used in conjunction with the buffer solution was prepared by dissolving 5 g of borax in 100 ml of 0.5 M sodium hydroxide. Cigarettes mtiji’lters. The cigarettes used were two domestic brands (tobacco blends), one European brand (dark tobacco), and two non-commercial types (burley tobacco and flue-cured tobacco). One of the domestic brands was an 85-mm filter cigarette and the other an 85-mm non-filter cigarette. All cigarettes were conditioned at 60% relative humidity at 75°F for 48 h before use. Filters examined for their capacity to remove ammonia from cigarette smoke were:
SHORT COMMUNICATION
244
1. Cellulose acetate: 1.6 den. per II.. 48.000 total den. tow; length 20 mm; 2.7 in. pressure drop. 2. Paper: length 20 mm with 2.5.in. pressure drop. 3. Cellulose-acetate-activated carbon ( 100 mg)--length 20 mm. 3.0 in. pressure drop. (Carbon was held in place with two 7.5 mm. 3.3 den. per fil.. 44.000 total den. cellulose acetate rods.) 4. Cellulose acetate: 3.3 den. per lil.. 44,000 total den. tow: treated with an acidic additive. 20 mm length. 3.0 in. pressure drop. 5. Cellulose acetate: high efliciency. 1.6-den. per fil. tow. 25 mm length, 2.4 in. pressure drop. Detrrwirltrtim oJ’ ctmmmia irl tobacco. Place a weighed sample of tobacco ( 100-200 mg) in a steam-distillation flask. To the flask add 20 ml of buffer solution and 5 ml of alkaline solution, steam-distil. collecting the distillate (80 ml) in 10 ml of 0.1 M hydrochloric acid and then dilute to 100 ml with distilled water. Transfer the solution to a 250-ml beaker, and stir at the rate established during calibration of the instrument with the known samples. Dip the ammonia electrode in the solution. and add 2 ml of aqueous 10 M sodium hydroxide. Read the previously calibrated meter directly in p.p.m. ammonia. Calculate the percentage of ammonia in the tobacco from the concentration in solution, volume of solution, and weight of the tcbacco sample. Deterrnirltrtiotl qf’unmot1i~~ irl cigcmt te SItlOliL’.Two cigarettes were smoked to 27-mm butt lengths under standard conditions, the smoke then being passed through a scrubber flask containing 50 ml of 0.1 M hydrochloric acid to collect the ammonia. Transfer the coptents of the flask to a steam-distillation unit and add 2 ml of aqueous 10 M sodium hydroxide. Steam-distil until about 80 ml of distillate has collected in a lOO-ml volumetric flask containing 10 ml of 0.1 M hydrochloric acid. Fill the flask to the mark with distilled water, and transfer the solution to a 250-ml beaker. Stir at the predetermined rate, add 2 ml of 10 M sodium hydroxide. and read the amount of ammonia in p.p.m. directly from the previously calibrated meter. Calculate the amount of ammonia per cigarette from the ml of distillate. p.p.m. of ammonia, and number of cigarettes smoked. The precision was determined from 7 repeat analyses. The percentage of ammonia removed from the tobacco smoke by various filters was based on the amount of ammonia delivered by a control cigarette equipped with a length of tobacco column equal to that of the test filter. Compwiso~~ of’ the electrotle r7wtlwtl with CI ~trs-chr.onlatog~~tpl~i~ method. To evaluate the accuracy of the electrode method, the ammonia in the tobacco and tobacco smoke from a non-filter cigarette was determined by a gas-chromatographic method similar to that described by Ayers’. An 8-ft x& in stainless-steel column packed with Chromosorb 103 was used; the column temperature was controlled at loo”, and a thermal conductivity detector was used. The method for collection of the ammonia was identical to that described above. but it was necessary to concentrate the acidic steam-distillate until the ammonia concentration was about 20 p.p.m. Results
mci tliscussio~~ Anwoniu corltent
oj’ cwrimrs
cigarette
tohawos.
The ammonia
contents
of
SHORT
245
COMMUNICATION
several tobaccos used in cigarettes are shown in Fig. 1. The cigarettes made from dark tobacco contained 0.48’;/, ammonia which was the highest of the commercial cigarettes tested. Cigarettes made from burley tobacco contained 0.31”/, and those prepared from flue-cured tobacco contained 0.11(x, ammonia. The blended tobacco of the non-filter domestic cigarette contained 0.14”/;: ammonia, and the blended tobacco of the filtered domestic brand contained 0.11% ammonia.
Fig. 1. Ammonia
content
of various
Fig. 2. Ammonia
content
of smoke
cigarcttc from
tobaccos.
various
cigarcttcs.
Amnonict in the w~olze of ocwious cigarettes. The smoke from the dark tobacco cigarettes contained 153 /cg of ammonia per cigarette (Fig. 2). Smoke from the burley and the flue-cured tobacco cigarettes contained 102 jig and 51 pg of ammonia per cigarette, respectively. Smoke from the non-filter, blended-tobacco cigarettes contained 67 /rg of ammonia per cigarette while smoke from the filter in blended-tobacco cigarettes contained 36 ,ug of ammonia per cigarette. The lower amount of ammonia in the smoke of the filter cigarettes was primarily due to ammonia removal by the filter. Removtrl qJ‘ummorrin ji*ont cigarette smoke by ji’lters. The amounts of ammonia removed from cigarette smoke by certain filters are shown in Table I. The most efficient filter for removing ammonia from smoke was the high-efficiency cellulose acetate lilter. l.The ammonia in cigarette smoke is present as the ammonium ion. This is indicated” b y the pH of cigarette smoke, which ranges from 5.4-6.4. In Fig. 3 FRACTION OF EACH SPECIES
PI I OF SOLUTION
Fig. 3. Frxtion
or NH,+ and NH3 LS. pH;(A)
NH;;
(0)
NI-I,.
246 TABLE
SHORT
COMMUNICATION
I
EFFIClEl\fCY (The tobacco
FILTERS
FOR
used contained
OF
0.147;
REMOVING
AMMONIA
FROM
CIGARETTE
SMOKE
ammonia)
-. Filter
Tobacco Cellulose xet;1te” Cellulose acctutcL Paper Acctatecarbon’ Acctateadditive”
Pressctrc drop (in )
A t,rtuoriitr ck4irer.v (j(g)
0.6 2.4
67 47
3.1
27
2.5 3.0
39 38
3.0
36
u Regular acetate filter: acct;1tc plugs: ’ xctatc
* high-cflkicncy liltcr containing
acetate filter: C 100 mg uctivatcd ;I polyol and an acidic additive.
-.
carbon
between
two 7.5-mm
The ammonia in cigarette smoke is present as the ammonium ion. This is indicated” by the pH of cigarette smoke, which ranges from 5.4-6.4. In Fig. 3 the fraction of ammonium and ammonia are plotted us. pH. In the pH range of cigarette smoke, the amount of unprotonated ammonia is negligible. Therefore, ammonia in cigarette smoke is primarily ammonium ion entrained in the particulate phase, and the amount of ammonia removed by a filter roughly parallels the amount of total particulate matter removed by a filter. This observation is further supported by the fact that the filter containing activated carbon did not selectively remove the ammonia from cigarette smoke. Accrtracy md precision. The precision of the method was determined from the repeated analyses of the smoke from the domestic brand 85-mm non-lilter cigarette. The mean delivery of ammonia was 67 pg with a standard deviation of 2.2 and a coefficient variation of 3.3(x. An attempt was made to compare the results with those obtained by the classical Nessler method4. However, several compounds in tobacco smoke interfered with the Nessler method, even after steam distillation of the sample. A gaschromatographic method. similar to that of Ayers”. was used to obtain a measure of the accuracy of the method. This method was less sensitive than the electrode method, and it was necessary to concentrate the acidified steam-distillate about 20-fold; the average amount of ammonia found in the smoke of the non-filter cigarette was 67 pg which is identical to the 67 ,ug obtained with the electrode method. The gas-chromatographic method was also used to determine the ammonia content of tobacco; the amount found was 0.13?/,, which agreed very closely with the O.140/0 obtained by the electrode method. Ejjtct oJ’ cmines OII electrode response. Amines were the compounds which were most likely to interfere with the electrode response during the ammonia determinations. No interference was observed when methylamine was added in
SHORT
COMMUNICATION
247
amounts equal to the ammonia concentration. It was therefore concluded that the relatively low amounts of amines in cigarette smoke (lo-15 ,ug of methylamine)” would not significantly affect the ammonia determination. REFERENCES 1 2 3 4 5 6 7 8 9
10 I1
J. W. Howell and D. F. Boltz. Aflu/. C/I~I,I., 36 (1964) 1799. D. Midgley and K. Torrance. Anc~Iysf (Lodo~r). 97 ( 1972) 626. 633. J. M. Brcnner and D. R. Kenncy. Ar~ul. Chinr. Acre. 32 (1965) 485. M. Hahn, Ge.str!?d/,. I/r{/.. 3 I (1910) 693. G. W. Pucker, H. G. Vichery and C. Lcavcnworth, I&. Eng. Chent.. Anul. Ed.. 7 (1935) 152. Chemists’ Rcscarch Confcrcncc J. F. Williams and G. F. Hunt. presented at the 21st Tobacco Durham. Enplnnd. 1967. J. R. Newsomc and C. H. Kicth. Tobacco Sci.. 9 (1965) 65. P. F. Collins. W. W. Lawrence and J. F. Williams, Beifr. Tcrhcr/iJiwsch.,6 (1972) 167. C. W. Ayers, Tuiutrm, 16 (1969) 1085. A. J. Sensabaugh and R. H. Cundiff, Tobacco Sci.. 1 I (1967) 25. H. Elmenhorst and Ch. Shultz Beifr. Tnha,kforsc/r.. 4 (1968) 90.
at