of species measured should be stated. For example, the
7. Identification of the ordinate scale in specific terms where possible. In general, increasing concentration of evolved gas should be plotted upwards. For gas density detectors, increasing gas density should also be plotted upwards. Deviations from these practices should be clearly marked. 8. A statement of the methods used to identify intermediate or final products. 9. Faithful reproduction of all original records. 10. Identification of the sample atmosphere by pressure, composition and purity; whether the atmosphere is selfgenerated, or dynamic through or over the sample. ?he flow rate, total volume, construction, and temperature of the system between the sample and detector should be given, together with an estimate of the time delay within this system. 11. Identification of the apparatus used by type and/or commercial name, together with details of the location of the temperature-measuring thermocouple and the interface between the systems for sample heating and detecting or measuring evolved gases. 12. In the case of EGA, when exact units are not used, the relationship between signal magnitude and concentration
dependence of the flame ionization signal on number of carbon atoms and their bonding, as well as on concentration, should be given. Members of the ICTA Committee on Standardization are: Prof. C. Mazieres (France), Dr. K. Heide (German Democratic Republic), Dr. F. Paulik (Hungary), Prof. H. Kambe (Japan), Dr. R. S. Forsyth (Sweden), Dr. H. G. Wiedemann (Switzerland), Dr. I. S. Rassonskaya (USSR), Prof. D. A. Smith (United Kingdom), Mr. R. W. Pfeil (USA). Other delegates to the Committee include Prof. L. G. Berg (USSR), Mr. C. J. Keattch (United Kingdom), Dr. R. C. Mackenzie (United Kingdom), Dr. J. P. Redfern (United Kingdom), Dr. 0. Menis (USA), and Dr. C. B. Murphy (USA). The Vicechairman is Dr. P. D. Garn (USA) and the Chairman is Dr. H. G. McAdie (Canada).
H. G . MCADIE
Ontario Research Foundation Sheridan Park Ontario, Canada
RECEIVED for review November 18, 1971. Accepted November 30,1971.
Gas-Chromatographic Separation of Hydrogen Sulfide, Air, and Water SIR: The resolution of small amounts of HzS from large quantities of air and water is of particular importance to industries with wet waste-gas streams containing sulfur gases (1,2). For example, in the pulp and paper industry the main stack gases from chemical recovery plants vary in temperature from 65 to 370 “C with a moisture content of about 27% by volume (3). Withdrawal of gas samples via a sampling line to a gas chromatograph for continuous analysis leads to gross condensation in the sampling line, and partial dissolution of the sulfur gases being estimated. A column is therefore required which will separate HzS from water-saturated air and water samples containing dissolved HzS. This allows the HzS content to be determined in the vapor phase and in the condensate, thus enabling the total concentration of HzSto be calculated. Previously, Jones (4) has reported the separation of Hz, Oz, NP,CO, Con, HzS, NH3, HzO, and C1 through C4 saturated hydrocarbons in oil-refinery gases, using two Porapak Q columns at different temperatures. However, only samples which are in the vapor phase under atmospheric conditions may be analyzed. The method is not applicable to two-phase samples and only “small” amounts of water may be tolerated. Obermiller and Charlier ( 5 ) have separated HPS, HCI, and HzO using a 5 Carbowax 20M on a Fluoropak 80 column, with air present as an impurity. The air peak was only partially resolved from the H&i peak. These workers (6) have also separated air, COz, HzS, HzO, COS and SOz using (1) C. Oloman, F. E. Murray, and J. B. Risk, Pulp Pup. Mug. Can., 70 (12), T499 (1969). (2) A. C. Harkness. F. E. Murray. and L. Girard. Atmos. Emiron.. 2, 303 (1968). (3) J. G. Sanderson and A. J. Roy, Pulp Pap. Mug. Can., 70 (ll),
T404 (1969). (4) C. N. Jones, ANAL.CHEM.,39, 1858, (1967). (5) E. Obermiller and G. Charlier, ibid., p 396. (6) E. Obermiller and G. Charlier, J . Clirornatogr. Sci., 7, 580 (1969).
0
1
2
3
Retention Time (mid;
Figure 1. Separation of air, COz, HzS, and H 2 0 in ‘wet’ air sample. Hot wire detector. Attenuation X20. ANALYTICAL CHEMISTRY, VOL. 44, NO. 3, MARCH 1972
641
Peak Helghl ( C N X 2.5
Figure 4. Peak-height calibration curve for H,S in aqueous solutions Carbowax 1500 on Teflon 6. The 0.d. of the stainless-steel columns was 1/8-in,,the mesh size for Porapak Q was 80/100 and for Teflon 40/60. The carrier gas was helium at 60 ml/min. The column has been used in a Beckman GC-M gas chromatograph to analyze gas samples which were either synthetic or extracted directly from the main stack in a Kraft pulp mill chemical recovery plant. RESULTS AND DISCUSSION
3
0 1 2 Retention Time (min.)
Figure 2. Separation of air, H2S,and H 2 0 in water sample. Hot wire detector
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20
Area(8q cm)
30
40
Figure 3. Sample loop calibration showing least-detectable amount of‘ H a in helium carrier gas Porapak Q columns in the presence of “trace” amounts of water.
Figure 1 shows the separation of air, C02, H2S, and HzO from a vapor phase sample. The trace was given by a 1-ml sample injection and the retention time of the H2S peak was about 30 sec from the air peak. Figure 2 shows the separation of H2Sfrom an aqueous sample obtained by bubbling H2S through a water-filled Dreschel bottle. The sample size was 7.5 pl. For both separations the injection inlet temperature WdS 120 “C, column compartment 125 “C, and detector compartment 175 “C. The “hot wire” current was kept at 150 mA with a recorder span of 1 mV for both samples. The minimum quantity of H2S which gave a recorder response was determined as 0.77 pg using an experimental dilution technique (7). Using a 10-ml sample loop, this corresponded to a minimum detectable concentration of about 50 ppm vjv. The calibration is shown in Figure 3. The gas chromatograph was calibrated for aqueous samples by 50 p1 injections of prepared solutions of H2S in distilled water and immediate estimation of the H2S content by iodine-thiosulfate titrations (8), Figure 4. This procedure offers a rapid analysis time and definite separation of the components without using either temperature programming or cold traps. It has been proved equally suitable for laboratory estimations and for continuous in-line analyses on the plant. Department of Chemistry Lakehead University Thunder Bay Ontario, Canada
EXPERIMENTAL
A Porapak Q column was used to separate air from H2S and H 2 0 ,and this was linked to a Carbowax column to increase the resolution. The total column length was 12 feet, 6 feet of Triton 305 joined to 6 feet of 5 Porapak Q treated with 642
ANALYTICAL CHEMISTRY, VOL. 44, NO. 3, MARCH 1972
W. G. COOK R. A. Ross
RECEIVED for review August 6,1971. Accepted November 30, 1971. (7) J. E. Lovelock, ANAL.CHEM., 33, 162 (1961). (8) A. I. Vogel, “A Text Book of Quantitative Inorganic Analysis,” Longmans Ltd., London, 1962, p 370.
