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
4
HzSOc
5
H2S04 H2
No. 1
+ HI +
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 a t room temperature and by the sensitivity of the detector system a t higher operating temperatures. Compounds with boiling points a t atmospheric pressure up to approximately 200’ C. have, in general, sufficient vapor pressure a t 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 Barras (1) reported developing 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.
From the flash chamber on, both reference and sample sides of the flow path are identical. The reference column and sample column are stainless steel tubing 1/4-in. 0.d. x 2 ft. in length and packed with 20 per cent by weight of SE-30 silicone gum on 60-80 mesh Chromosorb-P ( 2 ) . This packing was chosen because it is fairly nonselect ve and effects a separation essentially only by boiling point and also is stable over a wide temperature range. Only 2-ft. columns are used since good separation is not required or desirabl':. D u d parallel columns are used t o compensate for any bleeding effects. The cooling of th: columns is accomplished by having a third column, l/*-in. 0.d. copper tubing, mounted directly between and welded to the two gas chromatographic: columns. The cooling column is connected in series with a circulating refrigeration bath which continuously pumps coolant through the column (luring the cooling and stabilization period of the cycle. The cooling system is designed to maintain the column temperature to within 3 ~ 0 . 1F.~ The entire column assembly is enclosed by a heating jacket. The teniperature programming of the columns is accomplished by lirst draining the cooling column and then applying a fixed amount of heat to the heating jacket. This permits the column teniperature to rise through a linear programmed temperature curve. The columns are follon.ed by a heat exchanger. The purpose of the heat exchanger is to elevate the temperature of the effluent hydrocarbons to the necessary high constant temperature before entering the detector, thus increasing base line statility. The detector is a Gow-Mac Model 9220 high temperature thermal conductivity cell with a stainless steel block. The cell curr2nt is maintained purposely low since high sensitivity is not desirable. Also, this prolongs filament life. Flow control is achieved by using
I
EXCHANQER
I
I
I
MPLE
LUMN
OLING LUMN
FLASH CHAMBER SAMPLE
OUT
4 SAUPLE
Figure 1.
IN
Chromatograph assembly
Moore diaphragm-type flow controllers, Node1 63-BUL. The consumption of the helium carrier gas is quite low. The operating conditions of the gas chromatographic components are given in Table I for a light naphtha sample stream. The output signal from the detector is fed to a I-mv. Brown recorder which records the gas chromatographic curve. Mounted on the recorder is a Disc continuous ball and Disc integrator with a rotoswitch attachment. This furnishe? a pipping pen record of the integral on the chart and also a d.c. pulse output to an electromechanical Neuron readout counter. This counter not only counts the pulses but also provides for activation of a circuit when a pre5elected count has been reached. The full scale integrator capability is 600 counts per minute a t the pipping pen and 1500 counts per minute a t the rotoswitch. The coiintcr mechanism is so designed that any sequence of numbers up to 10,000 counts can provide a switching closure. The readout contacts are wired through a matrix board and stepping svitch in such a manner that the desired count numbers can be plugged into the matrix board to complete a switching closure to a printing counter (Raranoff). The printing counter is actually R time printer which is pulced on a time base of 300 counts per minute. It is commanded to print out time elapsed by closure pulses from the Xeuron counter and matrix system whenever the counter reaches preselected integral values. The printed time values form the basis for determining points on the distillation curve since retention time is a linear function of the sample boiling points on a linear programmed temperature gas chromatograph. A schematic diagram of the readout system appears in Figure 2. The repetitive on-stream operation of the analyzer is performed by a programmer or automatic timer. This is actually a standard process chromatograph control unit consisting of cams mounted on a shaft driven by a synchronous motor. Each cam actuates a microswitch which controls one or more functions of the instrument operation. A commercial version of this analyzer is being manufactured by the Mine Safety Appliances Co. Procedure. For initial operation of the analyzer, the sample lines are brought from the process unit and connected to the sampling valve of the analyzer. The usual precautions are taken to reduce the sample pressure and to install adequate filters in the lines. Once the analyzer has equilibrated t o the specified operating conditions, several runs are made to ensure satisfactory operation particularly of the sequence programmer, the sampling valve, and also the temperature programmer. If the analyzer is functioning properly, the gas chromatographic curves will repeat themselves exactly. The digital readout system i j then checked by observing the total integral
MECHANICAL
TC DETEcmR
YATRIX
BOARDS
FOR INTEGRAL
SELECTION
COINCIMNCE AND A D V A N E
CIRCUIT I
1
I
PRINT JSlGNAL
27 ISTILLAT1
Figure 2.
Readout system
count values. The attenuation range is adjusted so that all of the peaks are within the recorder range and so that the total integral count value is a workable one. That is, one which is of sufficient sensitivity and also readily divisible into various percentages. The total integral values must be reproducible to within 1.0% of the average total integral value. Based upon the average total integral value, the values which correspond to the desired yield points are plugged into the matrix board. Calibration of the analyzer is carried out first under simulated on-stream conditions with a static sample typical of the stream to be analyzed. A number of successive runs are made on the sample by both the analyzer and the ASTM-D86 procedure. A calibration curve is obtained by preparing a statistical plot of retention times printed out a t the selected yield points us. the corresponding .4STM-D86 temperatures. The curve obtained is essentially linear. From the curve a table of calibration values is readily prepared. This table permits simple conversion
Table 1. Operating Conditions for Light Naphtha Sample Stream 100" Sample valve
temperature Flash chamber temperature Column temperature Column
Heat exchanger temperature Cell temperature Cell current Cell Carrier gas Flow Total cycle time
c.
250" C.
15' t o 200" C. at 19'
C. per minute Dual, l / 4 " X 2', packed with 20% SE-30 on 60-80 mesh Chromosorb-P 250°
c.
250' C. 100 ma. Gow-Mac Model 9220
high temperature thermal conductivity cell Helium 60 ml. per minute 20 minutes
VOL. 36, NO. 6, MAY 1964
1009
SAMPLE-FULL RANGE G A Y Y i H E
0
D-86 DISTILLATION CURVE ILABORilTORll
OAS CHROMATOGRAPHIC DISTILLATIOH DATA GC END P O ( N T - 9 '
I /
0
l
-
-
O
~
O
U
) 5 O M O Y. RECOVERED
m
M
,
o
o
l
o
Figure 3. ASTM D-86 distillation curve
of printed out retention times to ASTM-D86 temperatures. The calibration curve is also checked on the on-stream sample in a similar manner. The gas chromatographic analyzer provides more precise boiling point distillation data than the ASTM procedure when retention times are plotted against true boiling point temperatures for calibration as is normally done (d).
Table II.
Repeatability Data
Total integral repeatability Number Average total Relative of runs integral counts std. dev. 1500
100
0.5
Yield point repeatability Std. dev. Yield point, yo for 100 rune, F. IBP 1.0 10
1.1 1.2 1.2 1.3 1.5 1.6
20
30 40 50 ..
GO 70 80
1.5 1.5 2.0 2.6
90 95
Table 111. Comparative Data-Chromatographic Analyzer vs. ASTM D-86 Laboratory Method Std. dev.5 in O F. of
Yield Point, yo TBP 10 20 30 40 50 GO
70
so 90 95
analyzer results us. D-86 results 3.1 4.7
3.7 3.5 3.5 3.9 3.8 3.6 3.6 3.7 4.0
These results were obtained over a three-month period. a
1010 *
ANALYTICAL CHEMISTRY
o
However, it was found that closer agreement with the ASTM-D86 results is obtained if the retention times are plotted against ASTM-D86 temperatures. I n Figure 3 is shown a comparison of a D86 distillation curve and a gas chromatographic distillation curve obtained using D86 temperatures for calibration. The initial boiling point and the end point obtained on the analyzer are inherently more reliable lhan those obtained by distillation because no significant loss or residue occurs with the gas chromatographic procedure. Therefore, to achieve better agreement, it is necessary t o determine these points somewhat arbitrarily by choosing integral count values IT hich correspond most closely with the ASTN-D86 initial boiling point and end point, respectively. RESULTS
Evaluation of the analyzer was obtained under both pilot plant and refinery conditions and also under simulated on-stream conditions. I n the evaluation it was necessary to establish the reliability of the analyzer as a process instrument. ,4s was mentioned previously, this involved the solving of several problems. Since the application of the digital readout system requires that the total integral value be constant, it had to be demonstrated that various components of the analyzer were capable of high repeatability. These components include the sampling valve, the automatic bridge balance mechanism, the integrator, and the switching counter. In Table I1 is shown the repeatability obtained for the total integral valua on 100 successive runs on an identical sample under simulated on-stream conditions. Since the programming sequence of the analyzer is based on time, it also had to be demonstrated that other components in the system did not introduce errors which would result in apparent changes in retention time of the sample. These components are the sequence controller, the flow controllers, the temperature programmer, and the cooling system. This ability to reproduce the retention times is also demonstrated in Table I1 where the repeatability for several yield points is shown for 100 successive runs on the same sample under simulated on-stream conditions. (Simulated on-stream conditions were chosen for this evaluation since it was necessary to maintain a constant sample composition.) The performance of the analyzer was evaluated over an extended period a t Gulf's Philadelphia Refinery on a prefractionator stream to a reforming unit. During this period, spot checks were made on the sample stream by means of the ,4STM-D86 distillation
Figure 4. curves
Typical chromatographic
procedure. Table I11 shows comparative results for the average analyzer values vs. the average ASTM-D86 distillation values. The analyzer values are based on approximately 2000 successive runs obtained over a three-month period. For evaluation at the refinery, the analyzer was installed in a trailer equipped as a mobile laboratory. This not only provided the required mobility and convenience, but also permitted evaluation of the analyzer without explosion proofing. Typical chromatographic curves obtained on the analyzer are shown in Figure 4. It should be noted that the kerosine curve was obtained using different operating conditions than those listed in Table I. DISCUSSION
The gas chromatographic distillation analyzer was found to be a very reliable process instrument. During one year of almost continuous operation only routine maintenance was required. In addition, once the analyzer was calibrated for a specific type of sample for a particular installation, no significant recalibration was required. Small changes in sample composition did not significantly affect the calibration. Although these changes caused variations in density and in response, it was found that concentration changes of as much as &loa/, of a single component varied the total integral count by less than &2%. This is a consequence primarily of the designed low sensitivity capabilities and also the good reproducibility of the apparatus. As a distillation analyzer it proved to be more applicable t o refinery control than the laboratory ASThI-D86 procedure. It also provided more precise data for both the light and heavy ends of a sample, Therefore, the important advantage of this analyzer lies in the fact that it can provide distillation data automatically on an on-stream basis with a minimumamount of maintenance. In addition, it provides full range distillation data, whereas all other commercially available process ana-
lyzers are capab!e of providing data for only one specific yield point. As such, the analyzeiu is very useful in refinery and pilot p l m t applications where distillation data are needed for control, It is especially suited for pilot plant research where only small amounts of sample are availabk. The analyzer is also well suited for gasoline blending operations. -4s a distillation analyzer the apparatus has sufficient flexibility to be applied t o various t,qpes of sample streams. Depending upon the nature of the sample, the operating conditions on the various instrumental components can be altered to obtain the desired type of distillation. fiamples through the kerosene and fuel oil range can thus be analyzed. Longer columns can be employed to obtain a more precise boiling point distillation when this may be required. Since the analyzer is a process programmed temperature gas chromatograph, it can also be used for the many applications where mch chromato-
graphic data are required. For example, it has been used for analysis of specific components and groups of components in wide boiling range sample streams such as the analysis of C6’s and lighter in gasoline. At Gulf’s Philadelphia Refinery the analyzer was modified to sample two streams. One stream was analyzed for full range distillation data and the other stream was analyzed for the concentration of benzene precursors. Thus, the apparatus can be used as a multipurpose process chromatograph. The readout system is also flexible. The data can be presented in the usual manner as a chromatogram with a pipping pen record of the integral along with the printed digitized record of the retention times a t selected yield points, If the chromatogram is not required, only the printed record need be obtained. This readout system can also be modified to present the data on punched tape thus fitting in quite well with a computer control system. ,Idditional work is being carried out to find other applications for this
analyzer and to improve its design. Particular attention is being given to extending its maximum workable temperature range. In addition, investigations are being carried out to modify the digital readout system to print out hST?vS-D86 temperatures directly instead of requiring the use of a calibration table. ACKNOWLEDGMENT
The authors express their appreciation to the many members of this company who worked on this project. In particular they wish to thank N. D. Coggeshall, D. H. Lichtenfels, F. H. Burow, A. B. Hartman, and L. H. Corn. LITERATURE CITED
(1) Barras, R. C., Boyle, J. F., 27th Midyear Meeting of API Division of Refining, May 16, 1062. (2) Eggertsen, F. T., Groennings, S., Holst, J. J., ANAL. CHELI. 32, 904,
(1960). RECEIVEDfor review July 18, 1963. Accepted February 3, 1964.
Detection a nd Spectro photo f I uorometric Characteriization and Estimation of Carbazoles and Polynuclear Carbazoles Separated by Thin-Laiyer Chromatography
FIuorescerit
DANIEL F. BENDER, EUGENE SAWICKI, and RONALD M. WILSON, Jr. Robert A. raft Sanitary Engineering Center, U. S. Department of Health, Education, and Welfare, Cincinnati 26, Ohio b A modification of the solvent medium used in a previous method for carbazole has resulted in considerable stabilization of the carbazole anion. It has improved the (earlier spectrophotometric, spectrophotofluorometric, and fluorescent spot test techniques for carbazoles containing acidic hydrogen on the nitrogen. The improved spectral methods have been applied to carbazoles of higher molecular weight, including polynuclear carbazoles. The fluorescent spot test has been applied to these carbazoles adsorbed on thin-layer chromatographic substrates. The absorption and fluorescent speclra in N,N-dimethylformamide and N,N-dimethylformamide-29% meithanolic tetraethylammonium hydroxide (5 to l), the fluorescent color changes, and the identification limits are reported for carbazoles and polyiiuclear carbazoles. A number of ,thin-layer chromatographic systems are described, whereby carbazoles can be sepa-
rated from other types of compounds and from one another. Commercially pure chrysene is separated readily by thin-layer chromatography into 5Hbenzo(b)carbazole and chrysene.
C
and polynuclear carbazoles, many of which are carcinogens (6, I T ) , have been found in various sources. Carbazole has been found in sources related to petroleum (6) and coal tar (9) and in the benzene-soluble particulates of air polluted by coal tar pitch fumes (11, 1 3 ) . Polynuclear carbazoles have been found in coal tar (9), cracked gas oils (I@, commercial chrysene obtained from coal tar (8, IO), aged rubber inhibited with N,N-diarylamines (16),and cigarette tar (19). Various reagents have been developed for the spot test detection and spectrophotometric determination of carbazole. The most sensitive spot test involves the fluorescent color of carbazole when exposed to a drop of aqueous alkali ARBAZOLE
(IS). When alkali is added to a solution containing carbazole, the fluorescent color is affected. This method has been used to characterize carbazole in air polluted by coal tar pitch fumes; however, the fluorescent spectrum fades rapidly (13). In the present work the alkaline fluorescent spot test and the fluorescence spectra have been considerably stabilized. The color change and identification limit of carbazole-type standards adsorbed on thin-layer chromatography substrates are described, The absorption and fluorescence spectra of carbazoles and polynuclear carbazoles in neutral and alkaline solvents are reported. A number of systems for the thin-layer chromatographic separation of carbazoles from other types of compounds and from one another are discussed, EXPERIMENTAL
Chemicals and Equipment. A’,fl.dimethylformamide, boiling point 14850’ C., was distilled over sodium biVOL. 36, NO. 6, MAY 1964
1011
