~~
Table I. Standard Analyses of Vinyl Chloride Sample
Flou rate
45-ppm standard
50 ml/min
Table 11. Precision of Vinyl Chloride Measurement
T i m e , Vinyl chloride min detccted, ul
1 2 2 3
2.168 4.506 4.508 6.866
Tenax ( 1 1 ) ,porous polymers (12), and graphitized carbon black (13) as adsorbents for solvents and hydrocarbons followed by thermal desorption has been shown to be a useful technique. However, analytical procedures based on the thermal desorption of activated charcoal directly onto a chromatographic column have not been extensively reported in the literature, although a most recent commercially available unit does utilize this process (Bendix Process Instruments Div., Ronceverte, WV). A simple test was devised to evaluate the performance of the adsorbent. A collection tube was attached directly to the 45-ppm VC1 standard lecture bottle and the gas flow was adjusted to 50 ml/min. Samples were collected for 2minute periods and then chromatographed. The efficiency of the adsorption-desorption process was evaluated by comparing the results obtained from the tubes with those of pure vinyl chloride injected with a gas syringe. The values were in good agreement. Data for duplicate analyses of vinyl chloride collected for 2 minutes as well as single values for 1-minute and 3-minute sample times are shown in Table I. The precision of the thermal-desorption method is shown in Table I1 for four standard runs a t the 1-ppm level. A relative standard deviation of 1.2% was calculated for the four runs. Standard samples of vinyl chloride collected on the charcoal adsorbent were also allowed to stand for several weeks before analysis with no apparent loss of monomer. For the analysis, an external standard technique was used. Peak areas were directly related to microliters of sample injected. Thus, the concentration of any given sample was calculated in parts per million by volume from the known volume of air sampled. A test of the overall efficiency of the method was devised using the 518-liter NBS smoke chamber. T o the sealed chamber was added 4500 111 of pure vinyl chloride. Air samples were then withdrawn from the chamber through one of the sampling lines a t the rate of 300 ml/min. The concentration of vinyl chloride in the chamber was calcuiated to
Run N o .
Retention time, min
VCI, ppm
1 2 3 4
6.51 6.51 6.47 6.50
1.248 1.217 1.225 1.218
be 8.7 ppm. Analysis of the three samples taken gave values of 8.8, 8.2, and 8.2 ppm resulting in an overall analytical efficiency of 96% for vinyl chloride. CONCLUSIONS The use of activated charcoal as an adsorbent for vinyl chloride followed by thermal desorption of the monomer directly onto a chromatographic analytical column has been shown to be an accurate, reliable method. The technique can be used for either personnel or environmental monitoring. Samples can he taken a t any location, and easily transferred to the analytical laboratory for subsequent analysis. In separate work, we have also shown that, with a minimum of expense and effort, the entire sampling and analysis process can be automated. The details of such an automated system have been reported a t the 1st National FACSS meeting (14). LITERATURE C I T E D (1) 8. G. Liptak, lnstrum. Technol., 2 1 ( l ) , 43 (1974). (2) 0 . S. Lavery and P. A. Wilks. Jr., Amer. Lab., 6 ( l o ) , 53 (1974). (3) Analytical Instrument Development, Inc., Avondale, PA, Appl. Rep., GCAN-127. (4) C. A. Burgett, Hewlett-Packard Co., Avondale, PA, Appl. Note, ANGC8-74. (5) Carle Instruments, Inc., Fullerton, CA, Bull., 9500-P. (6) Baseline Industries, Inc., Lyons, CO, Bull., FMIOOOB. (7) NIOSH Manual of Analytical Methods, HEWPubl. No. (NIOSH) 75-121. (8) L. D. White, D. G. Taylor, P. A. Mauer, and R. E. Kupel, Amer. lnd. Hyg. Assoc. J., 31, 225 (1970). (9) F. X. Mueller and J. A Miller, Arner. Lab., 6(5), 49 (1974). (10) S. A. Liebman, D. H. Ahlstrom, C. I. Sanders, E. J. Quinn. and C. D. Nauman, J. Fire Flammability, Combust. Toxicol. Suppl., 1, 78 (1974). (11) W. Bertsch, R. C. Chang, and A. Zlatkis, J. Chromatogr. Sci., 12, 175 (1974). (12) J. P. Mieure and M. W. Dietrich, J. Chromatogr. Sci., 11, 559 (1973). (13) A. Raymond and G. Guiochon, Environ. Sci. Technol., 8, 143 (1974). (14) S. A. Liebman. D. H. Ahlstrom, and C. I, Sanders, Abstracts 1st Annual Meeting, Federation of Analytical Chemistry and Spectroscopy Societies, Atlantic City, NJ, Nov. 1974, No. 160.
RECEIVEDfor review January 20,1975. Accepted February 27, 1975.
Determination of Water and Ethylene Glycol in Used Crankcase Oils by Gas Chromatography R. A. Putinier, T. A. Norris, and F. P. Moore Texaco Inc., P. 0. Box 509, Beacon, NY 12508
An important phase of the testing of used crankcase oils from gasoline and diesel engines is the detection and determination of water and ethylene glycol. These substances are common contaminants in used crankcase oils and a knowledge of their concentration can yield important clues 1412
ANALYTICAL CHEMISTRY, VOL. 47, NO. 8, JULY 1975
concerning engine performance and, in preventative maintenance programs, give early warning of impending engine trouble. A gas chromatographic method has been developed for the determination of water and ethylene glycol in used
0
~
N I
Table I. Retention Times and Response Factors Component
Retention time, sec
Water Acetone (standard) Ethylene Glycol
47
Volume response factor
17
0.61 1.oo 0.80
171
~
Table 11. Comparative Results of Water and Ethylene Glycol Determinations c---RRETENTION
TIME-
Percent by volume found
0
Figure 1. Chromatogram of water, acetone, and ethylene glycol Sample No.
Blended
Watera
Gas
lation by distil(ASTM
chromatography
D 95-70)
1
5 % WATER XI6
5 % ACETONE X 2
S%ETHILENE GLYCOL X2 5% FRESH GASOLINE X 2 5 % WEATHERED GASOLINE X I 5%DIESEL FUEL X I MOTOROIL X I
~
/ L -
Water Ethylene glycol
1.5 0.5
1.3 0.6
2 .o
Water Ethylene glycol
2 .o 1.o
1.9 0.9
3 .O
Water Ethylene glycol
None None
1.3 2.3
3.4
2
a
-2
3
---ud~
___
z
-~
4
~ - _ _ _
--
RETENTION T I M E
"Includes ethylene glycol if present. Samples No. 1 and No. 2 were prepared from the same used engine oil. Sample No. 3 is an actual field sample.
r
0
Figure 2. Chromatograms of various diluents and contaminants found in used crankcase oils DIUSacetone and motor oil
crankcase oils from gasoline and diesel engines. The analysis takes approximately 5 minutes and is being used routinely in our laboratory in place of the conventional distillation method for determining water in used crankcase oils. I t also replaces the various qualitative methods available for the detection of ethylene glycol. The quantitative determination of water in used engine oils is most often performed by ASTM Method D 95-70 ( I ). Average analysis time is forty-five minutes per sample. T h e trapped water must be examined for water soluble, volatile compounds such as ethylene glycol and alcohols, or t h e water content may be erroneously high. Qualitative tests are available for detecting ethylene glycol in used crankcase oils (2, 3 ) . A gas chromatographic method has been proposed by Greenleaf and Mikkelsen for the quantitative determination of water and ethylene glycol in used engine oils ( 4 ) .In this method, different column packings are used for the determination of each of the two contaminants. The analyses are performed isothermally but a t different temperatures. Each analysis takes about 10 minutes to complete. Esposito and Jamison (5) determined ethylene glycol in used engine oils by making the trimethylsilyl derivative and analyzing for it on a non-polar column using a temperature programmed instrument. Total analysis time was approximately 1 hour and water content was not determined.
EXPERIMENTAL An isothermal, gas chromatograph with thermal conductivity detector is used for the analysis. The column is a %foot by %-inch 0.d. copper tube packed with 80 to 100 mesh Chromosorb 102. The column is preconditioned a t 150 OC for approximately 15 hours with a slight helium flow. The column oven and detector block are maintained a t 150 O C . The injection port temperature is 280 O C .
Helium is used as the carrier gas and the flow rate is 100 ml per minute. The detector current is maintained a t 125 mA. Procedure. Fifty *,Iof acetone, the internal standard, is added to one ml of the sample in a one-dram glass vial. The vial is then capped and shaken vigorously. This yields a blend containing 4.8 volume percent acetone. Five ~1of this mixture is injected immediately into the gas chromatograph. The components elute in the order shown in Figure 1. The volume percent of the water and of the ethylene glycol are calculated using a simple ratio of peak areas and applying the suitable detector response factor relative to the internal standard. Typical detector response factors are 0.6 and 0.8 for water and ethylene glycol, respectively.
RESULTS AND DISCUSSION Common contaminants found in used crankcase oils are water, ethylene glycol, gasoline, and diesel fuel. Figure 2 shows chromatograms of an uncontaminated motor oil and equal amounts of each of the contaminants plus acetone blended in a motor oil. The chromatogram of ethylene glycol shows a peak due t o water. The water originates from the commercial ethylene glycol used to make the blend. Two chromatograms are given for gasoline, one is of a fresh gasoline and the other is of a weathered gasoline. The weathered gasoline would be typical of that found in used motor oils. The diesel fuel and motor oil show little or no interference with the water, acetone, or ethylene glycol peaks. Acetone was used as the internal standard because it disperses well in the oil and yields a peak on the chromatogram between the water and ethylene glycol peaks. Figure 1 is a chromatogram of a sample containing equal volumes of water, acetone, and ethylene glycol in a motor oil. Table I lists the retention times and volume response factors for these three components. If gasoline dilution is present a t greater than 596, it produces a few diffuse peaks which interfere slightly with the determination of ethylene glycol. For example, 1.0% water and 1.0% ethylene glycol were added to a field sample containing 6% gasoline dilution. T h e results obtained using this method were 1.0%water and 1.3%ethylene glycol, indiANALYTICALCHEMISTRY, VOL. 47, NO. 8, JULY 1975
1413
Table 111. Analyses of Water and Ethylene Glycol Blends Blend KO. 1
Run No.
1 2 3 4 5
Average Standard deviation
91 H20 O 4
2
Eth. qly. % H 2 0
0.8 0.9 0.9 0.8 0.8 0.8
0.3 0.3 0.3 0.3 0.3 0.3
0.07
,. .
%
3
Eth. gly. % H 2 0 ?4 Eth. gly.
0.5 0.5 0.5 0.5
0.9 0.7 0.7 0.7 0.7 0.7
0.05
0.1
0.6
0.5
1.0
0.8 0.8 0.8 0.8 0.8 0.8
. ..
...
1.0 1.0 1.0 1.0 1.0
cating a contribution to the ethylene glycol peak. Although the increase is sizeable on a relative basis, when regarded in absolute terms, in this type of application, it does not represent a meaningful increase. The combination of high concentrations of all three contaminants, water, ethylene glycol, and gasoline is extremely rare and would be readily apparent from the chromatogram of the used oil. Table I1 shows some comparative results obtained using this method and ASTM D 95-70. Samples 1 and 2 were prepared by adding the indicated amounts of water, and ethylene glycol to a used engine oil containing no detectable fuel, water, and ethylene glycol. Sample 3 is an actual field sample. Good agreement was obtained between the percent water by distillation, which also includes the ethylene glycol, and the combined results by gas chromatography. Total analysis time using the gas chromatographic method was about 5 minutes per sample. T o determine the repeatability of the method, three blends were made in a used crankcase oil. Five analyses of
each blend were made over a period of three days. Table I11 lists the results of the analyses and the standard deviation for each blend. As can be seen, the repeatability is good. An important consideration which must be mentioned is the actual sampling procedure. The original sample container as well as the 1-dram vial must be vigorously shaken t o achieve as homogeneous a sample as is practically possible. Another important point is, after thoroughly shaking and sampling the vial, injection into the chromatograph should be made immediately. The oil from each sample injection is retained by the column under the conditions of analysis and eventually the column becomes saturated. This can be detected as an upward drifting base line. The retention times and relative response factors should be checked about once a week or more often depending on the useage to determine if any changes in conditions are occurring. A typical column becomes saturated with oil after about 1000 analyses. When bleeding becomes a problem, the column is discarded and replaced with a new one. I t is good chromatographic procedure to change the septa and clean the injection ports on a daily basis. In this procedure, it becomes particularly important since the used crankcase oil causes accumulation of carbonaceous matter in the injection port. This carbonaceous matter could absorb ethylene glycol and cause interference with the analysis. LITERATURE CITED ASTM Standards, Part 17, American Society for Testing and Materials, 1916 Race St., Philadelphia, PA 19103. H. Levin. K. Uhrig, and E. Stehr, lnd. Eng. Chern., 11, 134 (1939). , D 2982-71T, ASTM Standards, Part 17, American Society for Testing and Materials, 1916 Race St.. Philadelphia, PA 19103. (4) C. Greenleaf and L. Mikkelsen. Facts and Methods (Hewlett-Packard), 8 , 4 (August-September 1967). ( 5 ) G. G. Esposito and R. G. Jamison, J. Mater., 5 (4), 779-85 (1970). ~
RECEIVEDfor review January 20, 1975. Accepted March 28, 1975.
Influence of Added Electrolyte to the Stationary Phase on Retention and Selectivity in Gas-Liquid Chromatography Jerry W. King Department of Chemistry, Virginia Commonwealth University, Richmond, VA 23284
Recently, we have determined adsorption and partition coefficients for 26 nonelectrolytes measured by gas chromatography on aqueous NaCl columns containing electrolyte a t concentrations up to 5.3 molal (1). While the primary purpose of this research was to study the effect of the addition of electrolyte on the gas-liquid interfacial adsorption of sparingly soluble nonelectrolytes on electrolyte solutions by gas-liquid chromatography (GLC), the results also are of interest in analytical chromatographic separations. We should like to report here a portion of this research which has important consequences in several areas of chromatographic research. Namely, these are: 1) The effect of electrolyte addition to the stationary phase in gas chromatography on the net retention volume of various solutes. 2) The change in the relative retention for various solute pairs which are retained on the column by singular and dual retention mechanisms upon addition of electrolyte to the stationary phase. 3) With respect t o (1)and ( 2 ) ,to note the effect of the solute interfacial adsorption a t the gas-liq1414
ANALYTICAL CHEMISTRY, VOL. 47, NO. 8, JULY 1975
uid interface on the determination of bulk solution retention constants and complexation constants. I t is well established that retention of solutes in gas-liquid chromatography columns may be represented by a summation of discrete retention volumes for the various retention modes operative in the column. For a binary solute retention mechanism consisting of adsorption a t the gasliquid interface and partition into the bulk stationary phase, the net retention volume per gram of packing, VN', is given as where K A = adsorption coefficient of the solute a t the gasliquid interface. ALO = surface area of the gas-liquid interface per gram of packing. K L = partition coefficient of the solute in the bulk stationary phase. VLO = volume of the stationary phase per gram of packing. The presence of a dual retention mechanism described in Equation 1 can readily be shown by noting the change in
