pressure distillation somewhat similar to ASTAI D 1160 ( 2 ) . Two base oils and two types of diluent uere used. One diluent was a nhole gasoline, the other a 207, bottoms fraction from the distillation of gasoline. These samples nere run in quadruplicate by the gas chromatographic method. API gravities reported for the diluent were used to convert the gas chromatographic results to volume-in-volume concentrations to permit direct comparisons. Table I1 lists sample composition and results and > h o w that gas chromatographic values are generally higher than distillation results. Distillation procedures in no case give significantly higher diluent concentrations than chromatography. Results on sample Q-1-S seem abnormally high, and perhaps the sample tcstcd in this work has become contaminated.
It is difficult to remove all diluent by distillation. Sample (2-1-R was heated to 300” F. for 4 hours and all vapors were remox cd which came off TT ith the pressure reduced to 1 mm. of mercury.
After this treatment, about 1% of diluent still was present in the oil. Regular Dilution Samples. Eight randomly selected samples of used lubricating oil, submitted for dilution analysis by ASTM distillation D 32255T ( I ) , were determined by the gas chromatographic method. Using an assumed density for diluent of 0.82, gas chromatographic results were converted to volume-in-volume units. Results for these samples are tabulated in Table 111. The chromatographic charts obtained were similar to those for the synthetic and ASTII samples. ilgain the chromatographic results were consistently higher than those obtained by steam distillation.
run by weighing in the internal stand ard. Therefore, oil dilution samples may be periodically extracted during a continuous engine test without appreciably altering engine conditions. If desired, resolution of the diluent can be increased by use of longer columns and Ion er temperatures than used in this work. This makes it possible to ftudy individual fuel components that appear as diluent. The chromatographic chart also provides a permanent record of the nature and amounts of diluent. This general technique has proved to be very useful for a variety of analytical problems. LITERATURE CITED
CONCLUSIONS
Results indicate that the chrcmatographic technique has improved the sensitivity, precision, and accuracy of fuel dilution analyses. Moreover, there are several additional advantages of this method over distillation procedures. Samples as small as 0.25 ml. may be
(1) Am. Soc. Testing RIaterials, Philadelphia, Pa., “ASTlI Standards,” p. 169, Method D 322-55T, 1958. ( 2 ) Ibid., Appendix I, p. 1076. (3) ASTM Bull., to be published. RECEIVEDfor review July 25, 1958. Accepted October 17, 1958. Division of Petroleum Chemistry, 134th Meeting, ACS, Chicago, Ill., September 1958.
Gas Chroma tog ra phic Dete rmination of DissoIved Oxygen in Lubricating Oil PAUL G. ELSEY Research lobcrafories, Ethyl Corp., Detroit, Mich.
b A rapid quantitative method for the determination of oxygen in lubricating oil, utilizing gas chromatographic techniques, was developed in connection with a program relating engine wear to the amount of oxygen present in lubricating oil.
I
the recently developed chromatographic method for oxygen determination in lubricating oil, a special column effects a preliminary separation of the dissolved gases from the oil. Then the mixture of gases is passed through a llolecular Sieve analyzing column, which separates the individual components so that oxygen can be determined. The total analysis time is approximately 10 minutes. The lower limit of detection of oxygen is 0.01 volume 70. The standard deviation of a single determination is 2.2% of the mean. The method can be extended to include the determination of other dissolved gases, such as nitrogen. The only knon n interference is argon, which has the same retention time as oxygen. N
EXPERIMENTAL
T h e apparatus consists of a commercial gas chromatographic instrument modified with a bypass arrangement. The preliminary column, a glass U-tube, is attached t o t h e bypass arrangement as shown in Figure 1. One leg of the glass U-tube is fitted with t1T-o coarseporosity fritted disks 5 inches apart. d sampling port for injection of the oil sample is located midway betn-een the disks. The diameter of the sample chamber is 0.5 inch. The analyzer column, a section of copper tubing 20 feet long and 0.25 inch in outside diameter, is packed with Linde 14 X 30 mesh Type 5,4 Molecular Sieve. The recorder is a 0 to 5 mv. strip chart rvhich is operated a t 60 inches per hour. Procedure. The instrument is thermostatted t o 75’ C. and is operi t e d with a helium carrier gas f l o ~ rate of 50 ml. per minute. The glass TT-tube is wrapped with heating tape and also maintained a t 75’ C. I t is attached t o the bypass assembly, and the entire assembly is purged with helium. Then t h e stopcocks of the assembly are adjusted so t h a t t h e glass V-tube is in the carrier gas stream of Apparatus.
the instrument. K h e n the instrument has reached equilibrium, as evidenced by a stable base line on the recorder, the oil sample is injected into the YDLECYLA.(I 5 L Y E I*A.L”lE* COLUUli
Til
rrro
0,s-
PORT
61UPLlNO
CONThIW 110 I I L CONE. PLUG
I
1 C(IE6YI
-lr 0“ T
Figure 1 . Preliminary column for separating dissolved oxygen from oil VOL. 31, NO. 5, MAY 1959
869
Table 1.
Determination of Oxygen in Typical Lubricating Oil Sample Temp. of Volume %
Size, M1.
U-?be, C.
1.o
25
Oxygen Found 1.57
1.71 1 . 73a
1.70* 1.73 1.74
Sample added t o 1 ml. of oxygen-free oil in U-tube. b Sample added t o 2 ml. of oxygen-free oil in U-tube.
sampling port of the glass U-tube. The retention times of oxygen and nitrogen are approximately 6 and 9 minutes, respectively. Upon completion of the analysis, the glass U-tube is removed from the bypass arrangement and rinsed with hexanes to remove the oil sample. Calibration data are obtained by using pure oxygen as a standard. The sensitivity of the instrument is such that a peak area of about 16 square inches is obtained for 0.1 ml. of oxygen a t standard temperature and pressure. The sensitivity is checked daily to minimize errors caused by any instrumental variations. Peak areas are measured with a planimeter. RESULTS
showed that oxygen was not quantitatively removed from the oil when the glass U-tube was operated a t room temperature and that the peaks on the chromatogram tended to tail slightly. With large oil samples, the tailing was more pronounced and the results were low. When the glass U-tube was heated to 75' C., no tailing was observed, and results were consistent over the range of sample sizes tested. Preliminary columns of this type serve two purposes: The analysis can be performed without contaminating the analyzer column with high-boiling components, and speed of analysis is increased as only specific compounds reach the analyzer column.
Table I shows the values of oxygen obtained from an oil sample that was saturated with air. Preliminary studies
RECEIVED for review November 10, 1958. Accepted January 8, 1959.
Paper Chromatography of 2,B-Dinitrophenylhydrazones Resolution of 2-Alkanone, n-Alkanal, AIk-2-ena1, and AI k-2,4-d iena I Derivatives A. M. GADDIS and REX ELLIS Dairy and Meat laboratory, Eastern Utilization Research and Development Division, Agricultural Research Service, U. S. Department o f Agriculture, Beltsville, Md.
A rapid paper chromatographic procedure for separating mixtures of 2,4-dinitrophenylhydrazones, 2-alkanones, n-alkanals, alk-2-enalsI and alk2,4-dienals of chain lengths up to 1 2 to 14 carbon atoms is described. Any member of the four homologous series studied, with the exception of acetone, ethanal, propanal, butanal, and propenal, can b e identified. The procedure consisted of resolving into classes by ascending development with petroleum ether on untreated filter paper, Acetone separated with the n-alkanal class and methanal and ethanal with the alk-2-enal class. Earlier paper chromatography systems for the separation of n-alkanals were used to separate class groups into individual compounds. The inseparable mixtures were acetonepropanal, acetone-butanal, and ethanal-propenal.
A
of paper chromatographic systems are capable of separating a limited number of members of a homologous series of 2,4-dinitrophenylhydrazones. Ellis, Gaddis, and Currie
870
NUMBER
,ANALYTICAL CHEMISTRY
(3) described a rapid ascending paper chromatographic procedure for separation of the C1to Cl4 n-aliphatic saturated aldehyde series, which was believed applicable to other homologous series of aliphatic monocarbonyls. However, it is extremely difficult to separate mixtures composed of different homologous series. Forss, Dunstone, and Stark (6) reported comparative R, values of the four homologous series on the paper chromatographic system of Huelin (9) and Meigh (16); with the exception of acetone, values were similar for 2-alkanone C,, alkanal C,+,, alk-2enal C n f 2 , and alk-2,4-dienal Cn+4. Nonaka, Pippen, and Bailey (17) found a different R j value alignment with the paper chromatographic system of Lynn, Steele, and Staple (13). Bassette, Day, and Keeney ( 1 ) separated homologous series easily on partition columns of nitromethane-hexane-Celite. However, mixtures of homologous series of 2-alkanones (except acetone). alkanals, and alk-2-enals were resolved into characteristic groups of C,, Cn+l, and Cn+p, respectively. Monty (16) has reported a differential spectrophotometric determination of saturated aldehydes and
ketones separated on a modified Kramer and van Duin (18) partition column. Pippen and coworkers (18, 19) separated some of these inseparable groups with silicic acid-Celite adsorption columns, and by repeated chromatography of fractions isolated a number of aliphatic monocarbonyl derivatives from chicken tissue. Forss and Dunstone (4) have shown that adsorption columns are relatively destructive and may cause rearrangements. This paper describes the extension of the paper chromatographic method of Ellis, Gaddis, and Currie (3) to other homologous series. A rapid new paper chromatographic method for the separation of mixtures of the four homologous series into classes is reported. The separation was referred to briefly by Gaddis and Ellis (7) and Ellis et al. (3) and this work was necessary to determine its effectiveness. The method ( 8 ) has since been used in a preliminary study of changes in the proportions of volatile monocarbonyl classes obtained from oxidizing fat. SOLVENTS A N D REAGENTS
ACS grades of carbon tetrachloride,
