200
centrations, the linear region of the graph was extended down to M. Although a generalization cannot be made on the basis of results with one batch of salts, it may be noted that Mesmer ( 6 )in a similar experiment found less F in 1M KC1 than in 1 M NaCl. It follows from this comparison that in order to avoid possible complications from ion-pairing and to be consistent with the use of KF as primary standard ( 2 ) that TISB or other high-ionic strength solutions be prepared from K salts rather than Na salts. As a possible additional benefit from this change, K salts may introduce lower F impurity than Na salts resulting in an extended linear calibration and reduction in the minimum detectable concentration. LITERATURE CITED 10"
166 NaF
105 concentration m o l e w l i t r e
Flgure 1. Emf vs. log(NaF concentratlon mol/l.) for N a and K buffers All polnts from the K buffer have been dlsplaced 00 mV downward for greater M NaF for whlch clarlty. (0)Experlmental polnts; (0)points in the reglon the nomlnal concentratlons have been corrected for the presence of F lmpurlty In the buffer
intentionally-added F. By extrapolation of the linear portion of the graphs values of 4 X 10-6 and 1X 10-6 M were derived as the contributions from impurities in the Na and K buffers, respectively. When correction was made to the nominal con-
(1) J. E. Harwood, Water Res., 3,273 (1969). (2) R. A. Roblnson, W. C. Duer, and R. G. Bates, Anal. Chem., 43, 1802 (197 1)(3) W. C. Duer, R. C. Roblnson,and R. G. Bates, J. Chem. SOC.,Faraday Trans.. 7, 68, 710 (1972). (4) J. N. Butler and R. Huston, Anal. Chem., 42, 1300 (1970). (6) M. S. Frant and J. W. Ross, Anal. Chem., 40, 1189 (1988). (0) R. E. Mesmer, Anal. Chem., 40, 443 (1908).
J. Bagg Department of Industrial Science University of Melbourne Parkville, Victoria 3062 Australia
RECEIVEDfor review May 3,1976. Accepted June 30,1976.
Chromatographic Analysis of Gaseous Products from Pyrolysis of Organic Wastes with a Single Column Sir: The operation and optimization of a pilot plant at which organic wastes, such as wood shavings, solid municipal waste, or rice hulls are pyrolyzed requires a method of analysis of the gaseous products, The gases detected were Hz, Nz, CO, COz, HzO,CH4, CzH4, CzH6, C6H6, and C7Hs. Our objective was to obtain a method of determination for these gases as simply and rapidly as possible. A search of the literature failed to show a simple separation of this particular combination of gases. Hollis and Hayes (1) showed that Hz, Nz,Oz, Ar, and CO could be separated at -78 "C on a Porapak Q column. In the same paper, they indicated that the column could also separate Hz,air, CO, CH4, COz, CzH4, CzHa, and HzO in that order at room temperature. This separation was made by Cross ( 2 ) .Papic (3) later separated C1 through C4 hydrocarbons, also on a column of Porapak Q. Many people have combined columns to achieve better separations (4-7). Stufkens and Bogaard (8)made a separation of Nz, 02,COz, CzHe and heavier hydrocarbons, including and C7H8 using a Porapak R column operated between -10 "C and 230 "C. This correspondence describes a method whereby the above mentioned gases may be separated for determination employing a single column. EXPERIMENTAL Apparatus. A Hewlett-Packard 5750 gas chromatograph equipped with temperature programming and a 0.5-ml gas sampling valve was used. The dual stainless steel columns (10ft X %in. id.) were packed with 50-80 mesh Porapak QS and modified with 2% terephthalic 1812
ANALYTICAL CHEMISTRY, VOL. 48,
NO. 12,
acid. Method. The separation was carried out as follows: prior to sample injection, the oven was cooled to room temperature (-26 "C).This was best achieved by opening the oven door and leaving it open
Table I. Analytical Conditions Sample Size : Column Length: Diameter: Material : Packing : Packing size: Packing modifier: Carrier gas: Temperatures Column: Primary isothermal period: Programming rate : Final isothermal rate: Injection p o r t : Detector: Sample loop: Recorder Chart speed : Detector Type : Bridge current:
OCTOBER 1976
0.5 m l
10 f t l/o-in. i.d. Stainless steel Porapak QS 50-80 mesh 2% Terephthalic acid Helium R o o m temperature (- 26 "C) t o 200 "C 2 min 60 "C/min Balance of analysis 230 "C 260 "C R o o m temperature ( - 26 "C)
2.00 in./min for 4 m i n 0.25 in./min for balance Thermal conductivity 160 m A
Table 11. Individual Analyses (mol %) Sample
H,
N2
co
1202'75 R1 120275 R 2 1202'75 R3 1203'75 R1 1203'75 R 2 1203'75 R3
17.7 19.8 11.5 18.0 19.0 19.5
1.3 0.5 0.8 0.7 0.6 0.7
37.6 39.6 41.8 30.1 34.4 33.8
CH, 17.9 19.4 18.8 18.6 17.9 19.1
CO,
25.0 22.4 20.9 19.4 19.7 21.6
C 2% 3.8 3.7 3.6 3.5 3.6 3.5
CZH, 0.9 0.9
CJ-4 1.2 1.3 1.0 1.2 1.4 1.3
0.8 0.8 0.9 0.9
C,H, 0.3 0.3 0.2 0.2 0.3 0.3
e 3
t
NEGATIVE I+ P E A K HEIGHT (INCHES) 4
x 64
X I
II
3t
5
I
k
0
2
3
4
6
s
I 10
IS
MINUTES
Flgure 2. Typlcal chromatogram of pyrolysls gas IO
MOLE
20
- a%
30
Peak Identlflcation: (1) hydrogen, (2) nltrogen (Includes oxygen), (3)carbon monoxide, (4)methane, (5) carbon dloxlde, (6)ethylene, (7) ethane, (8)water, (9) benzene, (10) toluene
40
HYDROGEN
Figure 1. Typical negative peak height curve
throughout the initial isothermal period. The gas sample, collected a t the pilot plant in a 40-ml Whitey stainless steel gas sampling bulb, was allowed to purge through the 0.5-ml gas sampling valve until the system came to atmospheric pressure. The sample was then quickly injected. The oven was held a t room temperature with the oven door open for 2 min. Temperature was then raised a t 60 OC/min to a maximum of 200 O C . In order to save paper, the chart speed which had been run at 2 in./min was reduced to 0.25 in./min 4 min into the analysis. Complete analytical conditions may be found in Table I. Calibration. The system was calibrated by analyzing a purchased (Union Carbide Corporation, Linde Division Primary Standard) calibration mixture. The relationship between peak area and mole percentage !was found using the cut and weight method (9).Because of the nonlinearity of the hydrogen response (IO), a calibration curve was made for thiA gas employing separate standards (Alltech Associates Calibration Gas). The relationship between the negative peak height (IO) and the mol % was plotted, as shown in Figure 1, and compared to samples. Finally, aromatics were calibrated using a 3-bl injection of a solution of benzene (50ml/l.) and toluene (10 ml/l.) in chloroform. A relationship between liquid volume and mol % was developed employing the ideal gas law. Water was neither calibrated nor calculated for.
ACKNOWLEDGMENT The authors express their deep gratitude to W. Martin Fassell, Donald W. Bridges, and Richard C. Dietz for their assistance and encouragement in preparing this work.
RESULTS A typical chromatogram is shown in Figure 2. Resolution between peak 2 (nitrogen) and peak 3 (carbon monoxide) is increased tis the room temperature is lowered. Results of the analysis of some samples collected from the pyrolysis of rice hulls are shown in Table 11.
Resource Recovery Systems Division Barber-Colman Company Irvine, Calif. 92714
LITERATURE CITED (1) 0. L. Hollis and W. V. Hayes, "Gas Chromatography 1966", A. B. Littlewood,
Ed., lnstltute of Petroleum, London, 1967, pp 57-70. (2) R. A. Cross, Nature (London), 211, 409 (1966).
(3) M. Papic, J. Gas Chromatogr.,6, 493 (1988). (4) R. R. Forsey, J. Gas Chromatogr., 6, 5 5 5 (1988). (5) R. I Jerman and L. R. Carpenter, J. Gas Chromatogr., 6, 298 (1968). (6) H. W. J. Sears, AMDEL Bull., 6, 47 (1966);as clted In Anal. Abstr., 18, Abstr. 1033 (1970). (7) J. S. Archer, J. Inst. Fuel, 43, 56 (1970). (8) J. S. Stufkens and H J. Bogaard, Anal. Chsm., 47, 383 (1975). (9) H. M. McNalr and E. J. Bonelll, "Baslc Gas Chromatography", 5th ed., Varlen Aerograph, Walnut Creek, Calif., 1969, p 154. (10) J. E. Purcell and L. S. Ettre, J. Gas Chromatogr., 3 , 69 (1965).
Peter T. Brodowski Norma B. Wilson William J. Scott* 1
RECEIVEDfor review May 10, 1976. Accepted June 24, 1976. Present address, 515 Palmetto, Pasadena, Calif. 91105.
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