The Loe detector has improved the gas chromatographic sensitivity fourfold over the sensitivity obtained with the standard F & M W1 detector even though it is used at lower filament current (90 ma.). With this detector we can conveniently determine the formic and acetic acid present in the smoke from 20 cigarettes. Peak heights us. concentrations of standard solutiolis of methyl formate and methyl acetate in methanol over a range of 0.1 to 2.0 pg. per microliter give a linear plot. It is necessary, however, to preload the column each day with the standard ester solution before making any measurements of peak height. The variation of the peak height of a single standard solution
I 1
I
40
I
eo
SOLVENT
‘y
1
120
160
RETENTIW TIME (SEC.1
Table II.
Comparison of Results
pg. in smoke/cigt. HCOOH CH3COOH Bradford et al. ( 1 ) All-bright cigarette All-burley cigarette Buyske el al. ( 2 ) All-bright cigarette All-burley cigarette By this procedure All-bright cigarette All-burley cigarette 5
4
2496”
252
2303”
424
1032
356
846
179
437
93
235
Total volatile acids as acetic acid.
Table 111.
1 2 3
410
Comparison of Resin Forms
pg in smoke/cigt. Eluted and of blended tobacco methylated on HCOOH CHaCOOH Rexyn 202 (OH-) 213 771 Resyn 202 (F-) 61 161 Effluent assed througt Rexyn 202 (OH-) 157 868 Total (2 plus 3) 218 1029
Table IV.
Cigt. brands A B
c
D E F G H I J K L M
382
Cigarette Smoke Delivery
pg./cigt. HCOOH CHaCOOH 61 50
161 137
48
~1-58 _ _
51 55 58 60 62 68 79 77 94 78
153 138 149 117 154 252 202 198 322 125
ANALYTICAL CHEMISTRY
Figure 1 . Gas chromatogram of methylated smoke components
Most authors extracted the acids with sodium hydroxide. Using Rexyn 202 (OH-) gave comparable results, while using it in the F- form gave lower values (Table 111). The,sum of the acids obtained by passing the F- form resin effluent.through the OH- form resin also gave comparable values; however, it appears that the extent of hydrolysis has changed. Table IV gives, results of some commercially available cigarettes analyzed by this procedure. The experiments that have been described show that this procedure quantitatively determines the amount of free formic and acetic acids in cigarette smoke and does not cause any hydrolysis of formic and acetic acid esters. This method should therefore be applicable to problems requiring the analysis of free formic and acetic acids in the presence of esters. ACKNOWLEDGMENT
- Smoke solution
--- Blank solution
from day to day and within a day is very small, if the column has been preloaded and if injections are made at regular intervals of about 20 minutes. The chromatogram of a typical smoke sample is shown in Figure 1. Hydrogen chloride and its reaction products with the resin appear first, followed by methyl formate at about 55 seconds and methyl acetate at about 78 seconds. The methanol solvent peak appears at about 140 seconds and is not completely eluted for 15 to 20 minutes. A small peak from the reagent blank solution which has the same retention time as the methyl formate peak must be subtracted from the sample peak height. Other peaks from the blank solution do not interfere. The peak height from the blank is higher if the resin is not washed with methanol immediately before elution with HClmethanol . Recovery studies were made by adding known quantities of aqueous solutions of formic and acetic acids to distilled water, to filter pads containing smoke particulate matter, and to the water traps before smoking. Recoveries of 95 to 105% of each acid were usually obtained, as shown in Table.1. The relative standard deviation of the method for an individual determination of the acids in cigarette smoke is &18% for formic acid and &14% for acetic acid at the 95y0 confidence level ( 2 ~ ) . This includes sample variation and smoking variation as well as analytical error. Buyske, Wilder, and Hobbs (2), and Bradford et nl (I), reported formic and acetic acid values for all-burley and all-bright tobacco cigarettes (Table 11).
The authors express their appreciation for the technical assistance given them by R. M. Ikeda. LiTERATURE CITED
( 1 ) Bradford. J. A , . Harlow. E. S.. Harlan, W. R., Hanmer, H.’ R., Ind: Eng. Chem. 29, 45-50 (1937). (2) Buyske, D. A., Wilder, P., Hobbs, M. -E., ANAL. CHEM. 29, 105-8 (1957). (3) Hornstein, T., Alford, J. A., Elliott, L. E., Crowe, P. F., Ibid., 32, 540-2 11960). (4) O’Keeffe, A. E., Lieser, R. C., Tobacco Sci. 11 73-6 (1958). ~
\ - - - - ,
( 5 ) Robb, E.
W., Westbrook, J. J., ANAL. CHEM.35, 1644-17 (1963). (6) Wartman, W. B., Cogbill, E. C., Harlow, E. S., Ibid., 31, 1705-19 (1959). RECEIVED for review November 12, 1964. Accepted December 22, 1964. Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Pittsburgh, Pa., 1965.
Correction Resorufin Butyrate and Indoxyl Acetate as Fluorogenic Substrates for Cholinesterase I n this article by George G. Guilbault and David N. Kramer [ANAL CHEM.37, 120 (1965)], the caption for Figure 1 on page 121 should read as follows: Figure 1. Excitation and emission curves for resorufin fluorescence A . Excitation curve: emission wavelength 580 mp B. Emission curve: excitation wavelength 540 mp
