Each of the first four samples was analyzed twenty times using the flame ionization detector, with a 0.05-ml. vapor sample. Each of the last four samples was analyzed twenty times using the thermal conductivity detector with a 2.5-pl. liquid sample. The thermal conductivity was not used for the first sample because the l-butene3-yne peak was too small for accurate measurement, while the last sample was omitted from the flame ionization detector program because it was felt that this was outside the range where the extra sensitivity is of any advantage. The results from the flame ionization detectorare shown inTable I11 and those from the thermal conductivity detector in Table IV. The reproducibility of results from the flame ionization detector
appears slightly better than that from the thermal conductivity detector. It is believed that a small sample size was a significant factor, since preliminary investigation using the flame ionization detector with the 2.5-pl. liquid sample had given indications of much poorer reproducibility. -4s pointed out in the procedure, if optimum accuracy is required, particularly for concentrations of 300 p.p.m. and higher, calibration factors should be obtained for a given detector. As can be seen in Figure 1, the resolution of 1-butyne and 2-butyne is excellent. While no studies were made of quantitative reproducibility for these components, there is no reason to believe that they should not be of the same order as those for 1-butene-3-yne.
LITERATURE CITED
(1) Dal Nogare, Ste hen, Juvet, R. S., Jr., “Gas-Liquid CPhromatography,” p. 110, Interscience, New York, 1962. (2) Grenesch, H., Stadtmiiller, R., Rev. Chim. (Bucharest) 9 , 35, (1958). (3) Kaufman, H. R., Zlatkis, A,, Chem. Ind. (London)1958, 1001. (4) Knight, H. S., ANAL. CHEM.30, 9
(1958). (5) Sands, J. D., Fullarton, Hugh, “A Combined Chemical-Mass Spectrometer Method of Analysis for Individual Alpha Acetylenes in CCHydrocarbons,” Polymer Corp., Sarnia, unpublished data (1949). (6) Taylor, G. W., Fass, T., C h a . Can., 7, No. 5, 46 (1955). ( 7 ) Tenney, H. M., ANAL. CHEM.30, 2 (1958). (8) Wittig, G., Wittenberg, D., Ann. 606, 1 (1957). C.A. 5 2 , 1971g (1958). RECEIVED for review September 19, 1963. Accepted January 27, 1964.
New Technique for Functional Group Analysis in Gas Chromatography Syringe Reactions JOHAN E. HOW and EUGENE D. FEIT2 American Meat Institute Foundation, The University of Chicago, Chicago 37, 111.
b A technique for the gas chromatographic analysis of functional groups of compounds in vapor mixThe vapor is tures is described. brought into contact with classification reagents in the syringe used to inject the sample into the gas chromatograph. Procedures are given for the detection of carbonyl compounds, differentiation between aldehydes and ketones, conversion of alcohols to acetates or nitrites, detection of unsaturation, hydrogenation of unsaturated compounds, and differentiation of ethers, olefins, aromatic hydrocarbons, and paraffins. The technique may b e applied to vapors a t concentrations from l o + to gram per ml. of vapor diluent and to compounds with boiling points up to at least 200’ C. a t normal pressure. The technique was tested with 35 compounds representing various functional group classes. The results are summarized in a classification chart which is suggested as an aid in identification work by this method.
T
development of ionization detectors for gas chromatographs has emphasized the need for more sensitive methods for functional group determinations, since the amount of material HE
1002
ANALYTICAL CHEMISTRY
which can be sensed by these detectors is several orders of magnitude smaller than that required even by microprocedures for functional group analysis. There is also a need for simpler means of obtaining information of compounds separated by gas chromatography than those used today. Trapping and further characterization by physical and chemical methods are time-consuming and require expensive equipment. Many attempts have been made to solve these problems. Dorsey, Hunt, and O’Neal (4) connected the output from capillary columns to a rapidscanning mass spectrometer and obtained mass spectra of the separated compounds. The sensitivity of this technique can be extended to obtain useful spectra of compounds present in microgram amounts, but this still falls short of the sensitivity of the ionization detectors. illteration of the chemical compounds by a reaction chamber in front of the column was studied by Beroza ( d ) , Drawert (6), and Rowan (8). The reaction products contributed to the characterization of the compounds that were originally in the mixture. Walsh and Merritt (9) obtained functional group information by bubbling the effluent gases through specific qualitative reagent solutions,
and Casu and Cavalotti (3) allowed the effluents to come in contact with filter strips wetted with such solutions. Bassette and Whitnah (1) removed certain classes of compounds selectively from the original mixture and caused a corresponding disappearance of peaks from the chromatograms. A similar prechromatographic treatment was used by Nelson et al. (7) in detecting olefins in a mixture with paraffins by hydrogenation of the original sample. In a previous communication (6) we presented a development of this approach in which the prechromatographic reactions between vapor mixtures and selective reagents took place in a. hypodermic syringe. The present report gives a more complete account of this technique and results of its application to compounds of various functional group classes. EXPERIMENTAL
Principle. Dilute vapors of organic compounds in air or inert gases are brought into contact with chemical reagents in a hypodermic syringe. The reagents may be gases, solids, or aqueous solutions. 1 Present address, Department of Horticulture, Purdue University, Lafayette, Ind.
2 Present address, Department of Chemistry,University of Chicago, Chicago37, Ill.
GENERATION OF ~ z 6 N E . A quantity of ozone sufficient for the treatment of a few milliliters of dilute vapors was generated by high voltage discharge between two electrodes in an atmosphere of oxygen (Figure 2). The electrode system consisted of an inverted hypodermic n e e d l e i e . , the needle part had Figure 1. Transfer of vapor from one been separated from the hub and insyringe to another serted through the rear side of the h u b and the barrel of the syringe wbich was grounded by means of a wrapping of Gas Chromatograph. A flame ionaluminum foil. The high voltage source ization detector, which is insensitive Figure 3. O-ring seal and needle was a Tesla coil type leak detector to water vapor, was used in this study. stopcock for treatments at elevated which was brought into contact with Column. The volume of the vapor temperatures the needle. sample (2 to 5 ml.) makes packed O-RINGSEAL. Occa8ionally, it may columns best suited for this technique. be necessary to operate at temperature A column of relatively wide diameter the formation of nit1'ogen oxides whic h above ambient to achieve reaction. is able to buffer the shock of injection evidently interfered with the sut1The plunger end of the syringe was of vapor samples of this magnitude sequent ozonization. If alcohols were rendered leak-tizht to the increased with less tendency for blowout of the treated with ozone contaminated with pressure by means of the arrangement flame and with better resolution. nitrogen oxides, the corresponding ni-. shown in Figure 3. A silicon rubber Packing materials are, as usual, detrites were produced. Nitrogen conO-ring was brought in contact with the termined by the nature of the sample tamination was avoided by a procedure sides of the plunger and the flange of and of the operating conditions. The similar to that described for hydrogen, the barrel by means of pressure exerted column specifications and operating conThe electrodeneedle (Figure 2) waE by a male and a female brass ring. ditions used in this study were: 6-foot brought in through the wall of the Tygon The pressure can easily be adjusted to X %-inch 0.d. stainless steel packed tubing while the oxygen was bubbling sml the plunger in a rigid position or to with 15% Ucon Non-Polar, LB 1715 at a brisk rate through a 20-em. water allow leak-free movement of the plunger. (a polyaikylene ether) on Chromosorb column. With oxygen flowing through The needle end of the plunger was W, (regular) mesh 60 to 70, a t 50' C., the needle, the barrel of the syringe sealed with a two-way stopcock (Becton, with a nitrogen carrier gas flow rate was slowly brought into position with Dickinson and Co.) of auuroximatelv 60 ml. uer minute. the hub of the needle, taking care that Reagents. The composition of the Seingrs. 'i%e Iiypode'rri.ic syringra all air was swept out of the barrel. reagents, their preparation, and the should ti. rquiplml u i i h eroun I-glass The plunger was next inserted against recommended levels of application barrels IO t!n?ure r v r n dixribution the pressure of the oxygen, and the are given in Table I. of liquid wigcnts and rrdnrz leakige, assembled syringe removed for genersc SODIUM METAL. A slice of metallic and with a needle lock to prevent tion of ozone. sodium, about 1 mm. thick, with two loss of the needle when in use. Spreading Technique for Liquid freshly cut surfaces was prepared. The B-D (Becton, Diekinson and Co.) Reagents. The liquid reagent was end of a 10-ml. Cornwd syringe plunger Yale Lner-Lok hypodermic syringes audied to the inner wall of the svringe pressed hard against the slice usually and B-D Cornwall Luer-Lok syringes caused the slice to adhere to the end were used. Needles, 25-gauge, permit of the plunger. The metal extending rapid discharge from the syringe beyond the diameter of the plunger was without excessively disrupting the of the pipet. A quantity 01 cut off with a knife (Figure 4). A septum of the injection port. pl. (Table I) was applied when using Accessory Equipment. TRANSFER. slightly &mished surface gave better a 2-ml. syringe, 25 p l . if i t was desired results than a freshly cut one. TarnishSamples were transferred from one to treat a larger volume of vapors in a ing was accomplished by exposure inside syringe to another by means of a 5ml. syringe. The plunger was inthe syringe for 3 minutes to 10 ml. of connector made bv solderine the hub serted following the application of the humid laboratory air. The syringe part of two hypidermic needles toreagent and was brought all the way containing the metallic sodium was gether end-to-end (Figure 1). A conin with a rotary motion. When the stored in a desiccator containine Drierite nector can also easily be made from plunger was pulled out (Figure 6 ) , an uud wuld be re-used wrrml tiniw. two 30-gauge 1-inch needles by pulling wetting of the wall had resulted. I I v m r o ~ n ~ G ~ nlsl .i r catalysr (PtOJ even the needle from the.hub and inserting No difficulties were experienced with was plirtd UI the hotrum id the syringe the tip of the other needle in its place this procedure as long as the syringe barrel by means of a microspatula to in the hub. Such a connector is leakwalls were clean. of the syringe avoid contamination tight. Transfer was necessary when Preparation of Vapor Samples. wall with resulting impediment of the an excess of a volatile reagent would Vapors were produced by injecting plunger movement. The syringe was interfere with the chromatogram or small quantities of liquid samples then partially filled with hydrogen when it was desired to treat a sample into closed glass containeri. Reagent A slow stream of gas as follows: with a series of reagents. bottles of 500-ml. capacity were used was bvdronen from a lecture hntt,le ~~~~~. brongst through a Tygon tubing into a beaker Wed with water. The bubbles provided a means for convenient gauging of the flow rate. The syringe was then partially filled with the gas by piercing the Tygon tubing with the needle. HYDROGEN IODIDE.This nowerfd L
~
Figure 2. of azone
Arrangement far generation
~~
~~~~~~~
~~~
with the plunger. One drop was, t h e r e fore, spread over the end surface of the plunger of a 10-ml. Cornwall syringe. OZONE. To achieve complete reaction with olefins, i t was necessary to generate ozone in a pure oxygen a& mosphere. Presence of nitrogen caused
Figure 4. Arrangement far treatment with metallic sodium VOL. 36, NO. 6. MAY 1964
1003
container (Figure 7). The capillary tubing prevented loss of vapors by providing a very narrow diffusion path to the serum cap. Recovery Study. Ten microliters of mixtures of equal volumes of liquid compounds belonging to the same functional class were injected into a 500-ml. bottle containing dry air and a piece of aluminum foil to aid the distribution of vapor by shaking the bottle. A portion of the vapor (2 ml.) was transferred by means of a syringe to another similar bottle to produce a level of concentration snitable for use with the syringe reaction techniaue (anuroximatelv 6 X gram der d.j: The comnounds (Table 11) were all of the highest purity commercially available and were used without further purification.
pplication of reagent s o b 3.
cnrougn most of this study. These were closed with a cork equipped with a 4-cm., 10-mm.4.d. glass tubing containing a serum cap. I n an effort to reduce absorption of vapors by cork or rubber, we later developed the container illustrated in Figure 7. A piece of 10-mm.-i.d. glass tubing was fused onto a narrow-necked 500-ml. Erlenmeyer flask and cut approximately 15 mm. beyond the neck. Another piece of glass tubing, 9-mm. o.d., was fused to a piece of capillary tubing and the wide end was formed into a flange, 1 mm. wide. The piece was cut to 4 em. total length and placed in the neck of the modified Erlenmeyer flask. A serum bottle cap was inserted in the S-mm.-o.d. tubing and wrapped over the 10-mm.-i.d. tubing to close the
Table
Figure 6. Spreading of reagent solution on syringe wall.
Concentrated Has01 I _ _ _ _ _ _ I
7. Vapor flask
Recoveries were determined by measurement of the peak height of the treated sample and of the untreated sample, and were expressed as the peak height ratios in per cent of the treated us. the untreated sample. The oxygen present in the air gave an appreciable peak at the sensitivity setting used in this study, and was used as an internal standard in correcting the volumes of the injected samples. It was not POSsihle to make this correction when the oxygen content was affected by the chemical reaction in the syringe b y drogenation, ozonization) or when other gases with the same retention
I. Reagents and Conditions for Syringe Reactions
Preparation of rsagents Slice on tip of plunger
. .-
Figure
7 ml. HBO, (concd.) and 3 ml. -ater, cooled to mom temp. tnd a few ma. PtOp
J. 9045% HaPo, warmed id stirred with a few g. XI irated solution of 1 ater, freshly prepare1 ",OH, HC1 in 50 I water Sodium borohydride 1 g. NaBH, in 2 ml. watm
ExSyringe posure Additional Size, +e, treatment Amount of Reagent, d. Type ml. mm. necessary Purpose of reagent 3 None Clean-up, leaving ethers and Thin slice Cornwall 10 hydrocarbons 2 3 None Clean-up, leaving paraffins and Yale 5 aromatic hydrocarbons 2 3 None Leaves olefins paraffins, and Yale 5 aromatic hydrocar@ns Yale 5 3 None Sat,urates uusaturazea oomFiounds 10 3 NaHCOa Cle;ayes ethers Wetting of Cornw$l plunger tip
2
5
None
2
3
None
2
3
None
Brommazes (removes) un8amrated con ounds RentIves cm%onyl compounds Removes carbonyl compounds, producing the corresponding alcohols Removes (oxidizes.) aldehydes, leaving ketones, produces ketones from secondary alcohols Produces nitrites from alcohols
5
Yale
2
3
None
rresnty preparea' 00id mixture of equal amountsI of 2.5 g. NaNOz in 50 ml. water and
5
Yale
2
3
None
5
Yale
2
3
NaHCOs Produces esters from alcohols
Sodium hydroxide
5 ml. acetic anhydiride and 2 drops HzSOl (con(:d.) 2.5 g. NaOH in 50 nd. w
Yale
2
5
Ozone
Ozone in oxygen
Hydrogen ohloride
2.5 ml. HCI (coned.) i n water
Potassium permanganate
"eoaium . . niwice ....
Acetic anhydride
Water Sodium arsenite
Saturated solution in water
,.
~
~~
I N HzSOd
Yale 5U ml.
5 g. NaAsOe in 53 ITd. water
water Sodium bicarbonate 2.5 g. NsHCOs in 5(1 d.
1004
ANALYTICAL CHEMISTRY
5
Yale
2
3
None
5
Yale
2
3
None
5
Yale
2
3
None
5
Yale
2
3
None
pounds, producing carbony compounds Removes amines Decreases water soluble com pounds Elifninates excess ozone, re auces ozoniaes Eliminates acidic compounds
(om*
Wmt-
Q,MW
t. w P.i
000
1 m 3 3 P - 3
o w 0
0
Qj
a
w w L3
000
000
000
000
000
000
OCCO
04
030
c000c
c30
0
VOL. 36, NO. 6, MAY 1964
1005
time were present (hydrogen evolution from sodium borohydride). Working Range. The working range of the technique was determined from a series of acetone vapor samples of different concentration levels in 2-ml. syringes. The samples were treated with 5 pl. of the hydroxylamine reagent and with the same amount of the sodium borohydride reagent. The signal was attenuated to give peaks within the range of the recorder at each level of concentration. RESULTS
The recoveries realized by the various chemical treatments of 35 compounds are shown in Table 11. The reproducibility of the recoveries was estimated by repetition of selected runs and was best in the extreme cases, where either no reaction occurred or the reaction went to completion. The reproducibility mas poorer when the recovery of volatile compounds was primarily affected by solubility in a liquid reagent or a side reaction occurred. Thus, treatments with recoveries in the range from 90 to 100% could be reproduced within =t5% and those in the range from 0 to 10% within &3%. When the recoveries were in the intermediate range, 10 to 90%, the reproducibility was appreciably poorer and was estimated as =t10%. Effects of Individual Reagents. Exposure to metallic sodium elim-
5
0
10
I5
MINUTES
Figure 8. Hydrogenation of olefins 1. 2.
3. 4. 5. 6.
7. 8. A. 8.
1006
0
1-Hexene 2-Hexene 1-Heptene 3-Heptene Benzene Hexane Cyclohexane Heptane Before treatment After treatment
ANALYTICAL CHEMISTRY
MI Y UTES
Figure 9 . Reduction of ketones with sodium borohydride 1. 2. 3. 4. 5.
Acetone 2-Butanone 2,3-Butanedione Isopropyl alcohol Isobutyl alcohol
A. Before treatment 8. After treatment
inated all the compounds except ethers and hydrocarbons. Hydrocarbons, in general, suffered little loss by the treatment. Heptane among the paraffins and allyl ethyl ether among the ethers were, however, decreased to a significantly greater extent than the others. Concentrated sulfuric acid eliminated all the compounds except paraffins and benzene, while the 7 to 3 diluted sulfuric acid in addition to these also left the olefins untouched. Appreciable amounts of other compounds did, however, survive the treatment with the latter reagent. Hydrogen gas and Adam's catalyst did not affect saturated hydrocarbons, but completely eliminated the unsaturated hydrocarbons which reappeared as the corresponding saturated species. It was not possible to hydrogenate benzene a t room temperature when the vapor diluent was an inert gas (argon). I n this case, heating in a closed syringe a t 100' C. for 5 minutes was required. When the vapor was present in air, however, the reaction occurred at room temperature (Figure 8). The reaction between hgrdrogen and oxygen may have caused the formation of a hot catalyst surface which facilitated the hydrogenation of benzene. Impurities in the hydrogen or the catalyst caused small peaks t o appear on the reagent blank chromatogram. The nature of these compounds and their elimination were not investigated. The hydrogenation procedure eliminated alcohols and aldehydes, which possibly became adsorbed on the catalyst surface. Ketones survived to a considerable degree, but 2,3-butane-
dione reacted. Among the esters, the formates were severely affected, while the acetates survived well. Saturated ethers were not affected, while the unsaturated ethers were converted to their saturated counterparts. Hydrogen iodide reagent was able to cleave all the ethers tested (except furan) but did not affect the hydrocarbons. All other cqmpounds were eliminated. All unsaturated compounds were removed by bromine water. In addition to bromination, this reagent also to some degree affected oxidizable compounds such aq alcohols and aldehydes by either oxidation or substitution, forming new volatile products. The nature of these was not investigated. Hydroxylamine hydrochloride reagent very efficiently removed aldehydes and ketones, while other groups were not appreciably affected. Alcohols were decreased because of their increased solubility in acidic solutions (see HC1, Table 11). Under the conditions used, sodium borohydride reduced carbonyl groups but tiid iiot affect eqter groups or double bonds. Formates were probably affected by the hydrolytic action of the alkaline reagent. Alcohols formed by the reduction of the carbonyl compounds were recovered in good yield
A
0
5
10
IS
20
MINUTES
Figure 10. Conversion of alcohols to nitrites 1. 2.
3. 4. 5. 6. 7. 8.
Methanol Ethanol Isopropyl alcohol Propyl alcohol Methyl nitrite Ethyl nitrite Isopropyl nitrite Propyl nitrite
A.
Before treatment
8. After treatment
(Figure 9). The lower primary alcohols, however, appeared in poor yield, probably because of high solubility in the reagent. Potassium permanganate effectively removed aldehydes, while little effect was experienced by ketones (monofunctional). Vnsaturated ethers were completely destroyelj, while olefins survived to some degree. The reaction betmeen alcohols and nitrous acid was used by Drawert ( 5 ) in his reaction chromatographic procedure to detect alcohols in wines and fermentation brews. The outstanding property of this reagent was the formation of nitrites from alcohols (Figure lo), while other funciional groups were largely unaffected. One exception was the acid -sensitive E thy1 vinyl ether which decomposed under the acidic conditions of the reagent. The nitrites were easily reconvert1:d to the alcohols by the action of hydroxylamine hydrochloride. Acetic anhydride, catalyzed by sulfuric acid, removed ,he alcohols, converting them to t ?e corresponding acetate esters, which appeared as new peaks (Figure 11). A( id-sensitive ethers and unsaturated aldehydes were also affected by this reagent, while saturated aldehydes, ketones, and esters were decreased, probably bwause of solubility in the acetic anhydride. Sodium hydroxide effectively hydrolyzed the esters and produced peaks of the corresponding alcohols. The yield of these produr-ts was, however, rather poor. Better yields were obtained with a stronger solution (30%),
I-
I
0
5
5
10
15
20
MINUTES
Figure 11. Esterification of alcohols with acetic anhydride 1.
8.
Methanol Ethanol Isopropyl alcohol Propyl alcohol Methyl acetate Ethyl acetate Isopropyl acetate Propyl acetate
A. 6.
Before treatment After treatment
2. 3.
4. 5.
6. 7.
but this resulted in less complete hydrolysis of the acetate esters. The alcohols and unsaturated aldehydes were severely decreased. 2,3-Butanedione was eliminated, as expected. Ozone eliminated all the unsaturated compounds tested except benzene. The decomposition products of the appropriate volatility were found as new peaks on the chromatogram (Figure 12). Alcohols suffered some oxidation and formed the corresponding aldehydes and ketones.
If excess ozone was not subsequently eliminated with sodium arsenite, artefact peaks from breakdown of the column material resulted. The sodium arsenite also reduced the ozonides to carbonyl compounds. Working Range. The efficiency of acetone vapor trapping by the hydroxylamine reagent failed a t congram centrations of approximately per ml. The upper limit is determined by the ratio of exposed reagent to amount of reactant and, therefore] varies with the amount of reagent and the type of syringe used. Thus, it was possible to extend the limit further (to approximately gram per ml.) by appropriately changing these parameters (exposed surface area, amount and concentration of reagent, time of reaction). With sodium borohydride the trapping efficiency started to fail a t 2 x 10-6 gram per ml., but was still 70% complete at 10-5 gram per ml. At very low levels of concentration (below 10-8 gram per ml.) the trapping efficiency again became poor. DISCUSSION
The purpose of developing the present technique was to obtain structural information from gas chromatograms of complex mixtures of volatile compounds in naturally occurring materials. The sensitivity of the syringe reaction technique should make it possible to work directly with dilute aqueous solutions, thus avoiding time-consuming concentration steps that may alter the composition of the sample both quantitatively and qualitatively. If it is desired to investigate an aqueous solution containing small quantities of unknown volatile compounds-a steam distillate of some foodstuff, for instance-the functional groups of compounds present at levels above O . O l ~ ocan be determined by this technique from 10 111. of sample. If quantitative or semiquantitative information is not required, it is possible to eAtend this lower limit. In this case, complete vaporization (see Experimental) is unnecessary and the sample may be obtained in the head space over an aqueous solution. For quantitative studies, proper attention should be given t o the effect
.. 5
0
10
IS
20
25
38
MINUTES
Figure 12. 1. 2. 3.
4. 5. 6.
7. 8.
1-Hexene 2-Hexene 1-Heptene 3-Heptene Benzene Acetaldehyde Propionaldehyde Unknown
Ozonolysis of olefins 9.
10. 11. 12. 13.
A. 6.
Butyroldehyde Unknown Benzene Valeraldehyde Hexanal Before treatment After treatment
Figure 13.
Classification chart VOL. 36,
NO. 6, MAY
1964
1007
Table ments for a fins,
111
Suggested Order of Treatand Sequences of Treatments Mixture Containing Ethers, OleAromatic Hydrocarbons, and Paraffins
Chromatogram 2
Treatment None Na
3
Na
No. 1
+ HI
4
HzSOc
5
H2S04 H2
+
Surviving peak8 All Ethers, olefins, aromatic HC. oaraffins O&fins,aromatic HC, paraffins Aromatic HC, paraffins ’ Paraffins, cyclic saturated HC
of sorption of constituents in the vapor phase to the glass walls of the vapor flasks and the syringes. The effect of sorption has not been investigated in this study, and the concentration levels stated throughout this report are based on the assumption that sorption did not materially affect the theoretical levels. The effects of the various treatments on the 35 compounds may conveniently be grouped into four classes: “NO Effect,” 100 to 90% recovery; “Slight Decrease,” 90 to 60% recovery; “Severe Decrease,” 60 to 10% recovery; and, “Elimination,” 10 to 0% recovery.
Disregarding bifunctional compounds, such as unsaturated aldehydes, unsaturated ethers, and 2,3-butanedione, the data in Table I1 may be presented as shown in Figure 13. This chart may find use as an aid in determining functional groups and in planning treatments and sequences of treatments for unknown mixtures of monofunctional compounds. When a compound has two functional groups, the effect is often additive, and the nature of such compounds may then also be deduced from the chart. The aldehyde group of acrolein, for instance, is revealed by treatment with hydroxylamine or sodium borohydride, while its double bond becomes apparent after ozonolysis or treatment with bromine water. The behavior of a compound cannot be predicted from the chart alone when strong interaction between two functional groups creates nonadditive effects and endows the compound with properties not expected from any of the two functional groups. The recommended order of treatments to be used on an unknown mixture is that used on the chart, working from left to right, but this will, of course, depend on the composition of a mixture. Special sequences of treatments involving several transfers will often be advantageous. A suggested scheme for the partial analysis of a mixture containing ethers, olefins, aromatic
hydrocarbons, and paraffins, besides other class compounds, is shown in Table 111. The application of the technique to compounds of higher molecular weight than those investigated here is limited only by the volatility of such compounds at room temperature and by the sensitivity of the detector system at higher operating temperatures. Compounds with boiling points at atmospheric pressure up to approximately 200’ C. have, in general, sufficient vapor pressure at room temperature to allow 10-4 to lo-’ gram of the vapor to enter the syringe. LITERATURE CITED
(1) Bassette, R., Whitnah, C. H., ANAL. CIIEY.32, 1098 (1960). (2) Beroza, M., Zbid., 34, 1801 (1962). (3) Casu, B., Cavalotti, L., Zbid., 34, 1514 (1962).
(4) Dorsey, J. A., Hunt, R. H., O’Neal, ?rl. J., Zbid., 35, 511 (1963). (5) Drawert, F., Vitis 2, 172 (1960); C A 54, 17788b (1960). (6) Hoff, J. E., Feit, E. D., ANAL.CHEW 35, 1298 (1963). ( 7 ) Kelson, K. H., Hines, W.J., Grimes, M. D., Smith, D. E., Zbid., 32, 1110 (1960). (8) Rowan, R., Jr., Zbid., 33, 658 (1961). (9) Walsh, J. T., Rlerritt, C., Jr., Ibid., 32, 1378 (1960). RECEIVED for review November 27, 1963. Accepted January 31, 1964. Third Meeting, Chicago Gas Chromatography Discussion Group, Oct. 3, 1963. Journal Paper Xo. 265, American Meat Institute Foundation.
Process Gas Chromatographic Distillation Analyzer J. A. PETROCELLI, T. J. PUZNIAK, and R. 0.CLARK Gulf Research and Development Co., Pittsburgh, Pa.
b A gas chromatographic analyzer has been designed to present Englertype distillation data. The analyzer is essentially a process programmed temperature dual column gas chromatograph equipped with a digital readout system. The details of this design are described. The analyzer was extensively evaluated under onstream conditions on both pilot plant and refinery units. The results obtained demonstrate that this apparatus is a reliable process distillation analyzer.
S
THE INTRODUCTION of programmed temperature gas chroniatography, considerable effort has been carried out to utilize this technique for distillation applications. Several gas chromatographic laboratory procedures were developed for analytical distillation for which many applications were found.
INCE
1008
0
ANALYTICAL CHEMISTRY
Recently, both Eggertsen (2) and (1) reported developing Barras laboratory procedures for analytical distillation by gas chromatography. Although these procedures have many advantages compared to standard distillation methods, it was concluded that greater advantages could be obtained from a process gas chromatographic distillation analyzer. Consequently, our efforts led to the design of such an apparatus particularly for the analysis of samples which are normally analyzed by the .4STM-D86 Engler procedure. Since it was necessary to use programmed temperature gas chromatography for this application, several problems had to be solved to achieve a reliable process instrument. These included reproducing exactly and repeatedly for each cycle the programmed temperature curve, the starting column temperature, the sample volume, and also the total integrator response.
Another important problem was the presentation of the data. The more precise gas chromatographic distillation data had to be converted to the less precise ASTM-D86 Engler-type data. Also, the final data had to be presented in digital form. EXPERIMENTAL
Apparatus. The apparatus is essentially a process programmed temperature dual column gas chromatograph equipped with a special digital readout system. A schematic diagram of the apparatus is given in Figure 1. The saniple is injected into the carrier gas stream by means of a pneumatically actuated hIicro-Tek 10-pl. sampling valve. Based upon extensive evaluation, this valve was found to be capable of introducing a constant volume of sample repeatedly. After injection, the sample is completely vaporized in the flash chamber.
