t h e plate height as measured with p-toluidine using 38% cyclohexane in MeOH mobile phase, was ten times higher on the copper column than on the amine colume (Hvalue of 6.0 m m a n d 0.62 mm, respectively). T h e capacity ratios of p toluidine, of course, were not the same on the two columns. For the least basic isomers, t h e efficiencies were about the same on both columns. T h e interaction between the Cu(I1) ion and the most basic amines, is different, it seems, than the interaction with the rest of the amines. The broad peaks tend to indicate that the rate of Cu-basic amine complex formation and/or dissociation is slow. With the silica gel and t h e bonded amine columns, sharp and symmetrical peaks resulted from all solutes. I t is clear t h a t the bonded copper does provide a n active site which interacts with aromatic amines to yield separations. T h e selectivities are unlike those occurring on silica gel surfaces or in bonded amine columns. I t seems t h a t the basicity of the aromatic amine, although important, is not the sole factor which determines the retention on the bonded Cu(I1) column. Steric effects undoubtedly play an important role in the interaction with the copper. A similar conclusion was reached by Kunzru and Frei (18)in their studies on the Cd-impregnated silica gel. T h e present Cu(I1) column cannot be used with aqueous solvents for reasons outlined previously. A more stable Cu(I1) column can be achieved by using a ligand which will bind copper ions more strongly than the propylamine. Leyden and his co-workers (viz. 29) have described the extraction of Cu2+ from aqueous solution by bifunctional moieties, bonded t o silica gel. Initial studies in our laboratory show t h a t Cu2+ bonded to a bidentate molecule is much more stable in such systems. Subsequent publications will describe the preparation and properties of metal ions which are strongly bonded to t h e chromatographic support.
LITERATURE CITED (1) F. G. Helfferich. Nature(London), 189, 1001 (1961). (2) H.F. Walton, S e p . furif. Methods, 4, 189 (1975). (3) H. F. Walton, Ion-exchange and solvent extractions, a series of advances“, Vol. 4, J. A, Marinsky and Y. Marcus, Ed., 1973,p 121. (4) V. A. Davakov, S. V. Rogozhin, A. V. Semechkin, and T. P. Sachkova, J . Chromatogr., 82, 359 (1973). (5) V. A. Davankov, S.V. Rogozhin, A. V. Semechkin, and T. P. Sachkova, J . Chromatogr., 93, 363 (1974). (6) R. V. Snyder and R. J. Angelici, Mech. Methods Enzymol., 3, 468 (1957). (7)J. Seematter and G. Brushmiller, J. Chem. Soc., Chem. Commun., 1277 (1972). (8) A. V. Semechkin, S. V. Rogozhin, and V. A. Davankov. J . Chromfogr., 131, 65 (1977). (9) F. W. Wagner and S. L. Shepherd, Anal. Biochem., 41, 314 (1971). (10) J. Navratil, E. Murgia, and H. F. Walton, Anal. Chem., 47, 122 (1975). (11) K . Shimomura, J-J. Hsu. and H. F. Walton, Anal. Chem., 45, 501 (1973). (12) J. D. Navratil and H. F. Walton, Anal. Chem., 47, 2443 (1975). (13) M. Doury-Berthcd, C. Poitrenaud, and B. ‘rremillon. J . Chromatogr.. 131, 73 (1977). (14) 0.K. Guha and J. Janak, J . Chromato:gr., 68, 325 (1972). (15) R. R. Heath, J. H. Tumiinson, R. E. Doolittle, and A. T. Provaaux, J . Chromatogr. Sci., 13, 380 (1975). (16) R. Aigner, H. Spitzy, and R. W. Frei, A,qa/. Chem., 48, 2 (1976). . R. W. Frei. J . Cktromatwr. Sci.. 14. 381 11976). 117) R. Aioner. H. S D ~ Vand (l8i D. Kinzru and R.’W. Frei, J . Chbmatcigr. S c i , 12, 191 (1974) (19) K. Yasuda, J . Chromatogr., 60, 144 (1971). (20) K. Yasuda, J . Chromatogr., 72, 413 (1972). (21) E. L. Karger, Northeastern University, private communication, 1977. (22) J. S. Fritz and J. N. King. Anal. Chem.. 48, 570 (1976). (23) P. R. Young and H. M. McNair, Anal. Chem., 47, 756 (1975). (24) P. R. Young and H. M. McNair, J , Chromatogr., 119, 569 (1976). (25) K. K. Unger, N. Becker, and P. Roumeliotis. J . Chromatogr., 125, 115 11R76) _,. (26) L. R. Snyder and J. J. Kirkland, “Modern Liquid Chromatography”, Wilev-Interscience. New York. N.Y.. 1974. (27) R. Belcher and A. J.’ Nutten, “Laboratory Manual of Quantitative Inorganic Analysis“, Butterworth. London, 1955,Chap. 3, p 244. (28) L. R. Snyder, “Principles of Adsorption Chromatography”, Marcel Dekker, Inc., New York, N.Y.. 1968. (29) D. E. Leyden and G. H. Luttrell. Anal. Chem., 47, 1612 (1975). ~
RECEIVED for review May 23, 1977. .4ccepted ,July 19, 1977. We thank NIH for supporting the present work under grant GM-20846-02.
Determination of Tetraethyllead in Gasolines by High Performance Liquid Chromatography T. C. S. RUO, M. L. Selucky, and 0. P. Strausz” Hydrocarbon Research Center, University of Alberta, Edmonton, Alberta, Canada
A high-performance liquid chromatographic (HPLC) method for the determination of tetraethyllead (TEL) in gasollnes has been developed. The method is based on the separation of TEL from other UV absorbing material on silica gel and quantiiicetion of the UV detector response. TEL concentrations corresponding to as little as 0.03 pg Pb In the sample (corresponding to 0.01 g Pb/imp. gal) could be determined quantitatively. The response of other alkylleads (tetramethyllead (TML) and mixed alkylleads (TMLTTEL)) differs appreciably from that of TEL, precluding the use of this method for unknown samples. However, the analysis can be done In 5 min using commercially available equipment and can be used in all cases where the type of alkyllead present In the gasoline is known.
A number of methods has been suggested for t h e determination of tetraethyl- or total lead in gasolines. They
T6G 2G2
comprise wet processes (1, Z ) , polarography ( 3 ) , gas chromatography (4-6), x-ray spectrometry (7), and atomic absorption (8) or methods using an atomic absorption spectrometer as detector ( 4 , 5 , 8). Except for chromatographic methods, they have been introduced as ASTM standards. Wet methods are tedious and time consuming, since they require conversion of T E L t o P b salts which are either determined gravimetrically, titrimerically, or spectrophotometrically. Also, polarography requires the same sample pretreatment and can be classified 8 s a wet method. Gas chromatography using conventional detectors is complicated for aromatic base gasolines because of peak overlaps and special columns must be used for retarding the aromatic hydrocarbons (6). Atomic absorption requires sample stabilization (8). Thus, of all the conventional methods, only x-ray spectrometry does not require sample pretreatment. Combination of gas chromatographic separation with an atomic absorption detector has been demonstrated to give reasonable repeatability ( 4 ) . The method is limited, however, ANALYTICAL CHEMISTRY, VOL. 49, NO. 12, OCTOBER 1977
1761
a UV detector a t a fixed wavelength of 254 nm. It will be shown that HPLC can be used for the determination of TEL (and other alkylleads) in gasolines. T h e sample is injected onto the column without any pretreatment, the alkyllead is separated from other UV absorbing material (aromatics and olefins) and the UV response is quantified.
Table I. Repeatability of ASTM Methodsa Sam-
syiz,
g Pb/U.S. gal in sample Method 0.5 1 2 4 mL Gravimetry 0.02 0.10 0.11 0.14 SO Polarography 0.04 0.05 0.08 0.12 SO X-ray 0.03 -0.04 -0.05 0.06 1 0 Volumetry 0.06 0.06 0.07 0.08 50 " In g Pb/U.S. gal.
EXPERIMENTAL All HPLC analyses were done using a 60 cm X '/?-in. 0.d. p-Porasil column and n-heptane eluent. The instrument was Model 202 (Waters Associates) equipped with a UK-6 sample loop, Model 6000A solvent delivery system, UV and RI detectors (Waters Associates), model 17501A recorder (Hewlett-Packard) and model H P 338OA integrator. Sample injections were made with a 10-pL Pressure-Lok syringe (Precision Sampling). Other chromatographic conditions were: F = 1.5 mL/min, P = 1500 psi, recorder chart speed 0.5-in./min, integrator chart speed 1 cm/min. The UV detector was a fixed wavelength instrument (254 nm). Most measurements were done at detector attenuation X64 (chart width = 0.015 f.s.a.). A LC-55 UV detector (Perkin-Elmer) was also used for some measurements. Calibration. Aviation Mix Blue 21 (Ethyl Corporation) was used as such for the preparation of calibration solutions. This solution contains, by specifications, 61.4 f 0.25 w t % TEL and 35.67 wt R CH2Br2.Thus, 1.46 mL Mix contains 1.0 g Pb as TEL; 1.54 mL Mix contains 1 mL TEL; w t % Pb in TEL = 64.06. Tetramethyllead (TML) solutions were prepared using "TML Dilute" samples from DuPont and Ethyl Corporation. Mixed alkyllead solutions were made from MLA-500 (Ethyl Corporation) and Tetramix-50 (DuPont) samples. The calibration solutions are listed in Table 111. All other samples used are listed in Table IV and are solutions of a known amount of TEL in various refinery streams, i.e., reformate, light cracked naphtha (LCN) and refined oil (Turbo fuel A. Arctic diesel fuel P-60).
Table 11. Selected Results from a Corroborative Study Based on Canadian Standard" g Pbiimp. gal in sample
a
Repeatability Reproducibility In g Pbiimp. gal.
0.5 0.06 0.23
1
0.12 0.46
2 0.25 0.92
4 0.5 1.8
because of its incompatibility with electronic integration (the baseline noise is large) and insensitivity to other gasoline components; moreover, burning of the gasoline in the atomic absorption spectrophotometer (US)burner changes the flame properties, thus creating additional baseline noise. Frequent calibration is also necessary. Another liquid chromatographic method with AA detection (9) using a reversed phase technique (MeOH/H20),gave a noise level of 12.5% (100 X (N/S) for 0.39 pg TML) which again is incompatible with electronic integration. T h e determination of TEL in gasolines, as described in ASTM methods, is confined to the 0.2-5.0 g Pb/U.S. gal range in most cases, and the required sample size for most of them ranges between 5 and 50 mL. Repeatabilities of four of these methods, together with required sample sizes, are shown in Table I a t various concentration levels of P b in gasolines. Reproducibilities and repeatabilities are dependent on the Pb contents in the sample. For example, for a content of 1 g Pb/U.S. gal, the reproducibility can vary between 0.1 and 0.25 g Pb/U.S. gal. T h e results of a practical test between 7 laboratories, based on AA (as described by the Canadian standard method ( 1 9 ) ) yielded repeatability and reproducibility results summarized in Table 11. For P b levels exceeding the maximum allowable Pb concentration, the reproducibility exceeded 45% and the method is therefore meaningless. HPLC of gasolines on microparticulate silica has shown that TEL or other alkylleads appear together with the saturate peak and can be detected over the saturate background using Table 111. Composition of Calibration Solutions Sample No. Alkyllead 1 Aviation Mix (TEL) 2 3 4 4Db 11
RESULTS AND DISCUSSION In HPLC separation of gasolines on microparticulate silica, the peak corresponding to TEL or other alkylleads is completely separated from aromatic and olefinic hydrocarbon peaks and is eluted together with total saturated hydrocarbons as illustrated in a sample chromatogram in Figure 1. Since TEI, and other alkylleads absorb at 254 nm, whereas saturated hydrocarbons do not, the peak appearing in the UV trace in the saturate region corresponds t o the alkyllead. (The UV spectrum of TEL shows an absorption continuum beginning a t about 275 nm and extending towards shorter wavelengths (I 1-14)). Extensive studies of the chromatographic behavior of various refinery streams on silica have confirmed that, normally, no other UV absorbing compounds which might interfere with the absorption of TEL (or other alkylleads) are eluted in the same region of retention times. On the other hand, the separation achieved must be good enough to
g Pb/imp. g
0.01104 0.01605 0.02378 0.00548
0.00274 0.021s 12 0.0427 13 0.0642 14 DuPont Tetramix-50 0.0428 15 0.0644 16 Ethyl Corporation TML 0.0482 17 0.0658 18 Ethyl Corporation MLA-500 0.0215 19 0.0425 20 0.0642 a Total volume 1 0 mL for all samples (not corrected for temperature). alkylate ( 1 : l ) . 1762
Solvent Light alkylate
DuPont TML
ANALYTICAL CHEMISTRY, VOL. 49. NO. 12, OCTOBER 1977
n-Heptane n-Heptane n-Heptane n-Heptane Prepared
g (or mL)"
gal 1.974 2.870 4.253 0.980 0.490 1.101 1 0 mL 2.186 1 0 mL 3.287 1 0 mL 2.191 1 0 mL 3.296 1 0 mL 2.469 1 0 mL 3.371 1 0 mL 1.101 1 0 mL 2.176 1 0 mL 3.288 10 mL by diluting sample = 4 with light 6.82711 6.81786 6.82316 6.80254
.
.
L
1
1 I
I
I
Figure 2. Typical TEL determination using electronic integration and ESTD method of calibration
I
chromatograms of reguiar. premium, and unleaded gasolines S = saturates, MA = rnonoaromatics. D 4 = diarornatics. 0 = olefins Figure 1. HPLC
completely eliminate the possihle influence of some olefine which appear hetween the monoaromatic and saturate peaks iii the chromatogram if, e.g., heavy cracked naphtha (HCNI is used in the hlend. High column efficiencies r S 7OOQ for henzrne) and R good Feparation of olefins from saturates can he ohtained on microparticrilat,e silica. Figure 1 is a chromatogram of gasolines recorded hy both the RI and 13' detectors and demonstrates ihe feasibility of HPLC determination of TEL in gawlines. provided that the response is linear over t h e concentratinn range of interest and also that, the underlying saturate matrix (visible in the RI trace but not in the U l - trace) does not adversely influence response quan titation. Therefore. experiments were done t o verify the linearity of response over a TEL Concentration range of 0.2 -4 g Ph,/imp, gal, the repeatahility of determinations. and the possihle influence of the underlying saturate matrix. Other important quest,ions t o be resolved were day-to-day repeatahility of measurements (in other words, the validity of external calibration figures introduced in the integrator memory) and long term repeatability. Corroborative reproducibility studies cndd not be performed. Externa! standard calibration (ESTD) is the method of choice when an electronic integrator is being used for peak quantitation. Since any nonpolar compound, elutable under the conditions of elution with n-alkane from silica, will elute together with one or another peak in the chromatogram, internal standardizat,ion cannot be used. T h e same can be said about the calibration of peak height measurements. Figure 2 is a typical jntegratm print,nut for the standard solution used, Le., T E L in light cracked naphtha. T h e calibration curves were constructed as integrator counts vs. concentration (g Pb/imp. gal) or as peak heights in mm vs. concentration (g P b / i m p . gal) when a normal recorder was
-
G 0. _u
C
;'
..
2-
2b 1 T O
231
Figure 3. Calibration curves for TEL conceritration measurements from
integrator counts and peak heights used. In all of the experiments, the recorder and integrator were connected in parallel, so that both responses were obtained concirrrently. From the calibration curves. Figure 3, the unit count per wt of Pb as TEL lor unit peak height per w t of P h as TEL were calculated, together with dispersion of measurements. T h e calibration curves are linear over the range 0.5-2.4 g Pb/imp. gal, i.e., for 0.53-2.6 pg Pb in the sample (injection volume, 5 pL). At 3 g Pb/imp. gal, they hegin to deviate hy about 5% towards lower values but !inearit!: can be achieved using smaller injections (e.g., 3 pL). 1 Note however. that the above deviation represents only 0.15 g Phiimp. gal a t this concentration level.) If the calibration curves are used. the data are within 1% of the actual Pb contents. Table IV also shows a slight tendency towards higher results in the low concentration range (about 0.5 g Pb/imp. gal). In this region however, the determination was still very accurate a t the 0.49 g Pb/imp. gal (0.39 g Pb/Lr.S. gal) level. Thus the deviation of repeated measurements was 0.0044.006 in two different sets of results. At the full attenuation of the detector ix64)! the number of integrator counts was 4500, the peak ANALYTICAL CHEMISTRY, VOL. 49, NO. 12, OCTOBER 1977
1763
Table IV.
Selected Results of Measurements by ESTD' and Peak Height Methods. No. Difference, in rel. Measured concn, g Pbiimp. of Actual gal Difference, in g Pb/imp. %, from actual g meas- concn, Pbiimp. gal gal from actual value Sample ureg Pbl Integration NO.^ Solvent ments imp. gal (ESTD) hk ESTD hk ESTD h 1 Alkylate 5 1.974 1.998 (0.013)' 1.97 -0.024 0j 1.22 lb Alkylate 5 1.952 (0.008) 2.00 -0.002 +0.03 1.11 1.32 1 C Alkylate 5 1.993 (0.006) 2.09 +0.019 +0.12 0.95 5.88 2 Alkylate 5 2.870 2.812 (0,009) 2.87 -0.058 0 2.02 2b Alkylate 5 2.791 (0,012) 2.90 -0.079 +0.03 2.75 1.05 3 Alkylate 5 4.253 3.930 (0.009) 4.25 -0.32 0 7.53 0.988 (0.007) 0.99 +0.008 0 0.8 4 Alkylate 5 0.980 4Dd Alkylate 5 0.490 0.514 (0.006) 0.49 +0.024 0 4.6 4De Alkylate 5 0.504 (0.004) 0.53 rO.01 0.04 2.8 8.2 SIf Alkylate 4 3.858 3.870 (0.04) 3.79 +0.01 - 0.07 0.31 1.76 SIIf Unleaded 5 3.857 3.920 (0.02) 3.78 +0.06 - 0.07 1.63 2.0 gasoline 7 Reformate 4 2.028 2.072 (0.006) 2.03 +0.044 +0.002 2.12 0 8 Reformate 5 2.865 2.830 (0.01) 2.78 +0.03 - 0.08 1.22 2.8 9 Refined oil 5 1.924 2.250 C0.028) 1.89 -0.03 16.93 1.56 +0.33 10 Refined oil 5 2.860 3.030 (0.02) 2.70 -0.16 +0.17 5.96 5.6 11 LCN 5 1.958 1.956 (0.017) 1.91 -0.002 -0.05 0.12 2.45 12 LCN 5 2.885 2.793 (0.03) 2.94 -0.09 J. 0.06 3.17 1.91 a All data refer to sample size 5 p L unless specified otherwise. After two days. After one week. Prepared by diluting sample *4 with alkylate 1:l. e One day later. Sample size reduced t o 3 ML. g Numbers in brackets are standard deviations. Samples for which the value in this column is zero were used for the preparation of the calibration curve. h = peak height in mm. NOTE: The calibration factor for the ESTD method was determined by an independent analysis of sample +1 and used over a period of four weeks,
-
'
I
0 MLA-500jEthyl C o )
;5o
t
20,000
6 2
4
0
6
tR,min Y
Q
E
5,000
'00
TEL
b
i
i
JDA
I
I
I
I
2
4
6
a
t ,min R
Figure 4. Peak height and noise for (a) 0.49 fig Pb y g Pb as TEL in the sample
as TEL and (b) 0.03
height (recorder at 10 mV/% cm) was 16.2 mm and no noticeable noise was observed. T h e integrator recorder, set at approximately 2 mV/15 cm chart width gave a peak 44.5 mm high (Figure 4a) again, with no noticeable noise. Under these circumstances, the detector attenuation can be set a t least 4x lower. (Higher detector sensitivities produce noise a t such a level t h a t i t is integrated by t h e integrator.) 1764
ANALYTICAL CHEMISTRY, VOL.
05
10
15
20
25
30
3.5
g P b / i m p go1
MA
49, NO. 12, OCTOBER 1977
Figure 5. Calibration curves for TEL, TML, and TML/TEL (1:l) mix
Calculations based on the above results have shown t h a t a fourfold increase in sensitivity and twofold increase in sample size should allow the determination of 0.01 g Pb/imp. gal (0.03 gg P b in the sample). Under these conditions, the peak height should be about 10 mm. T h e corresponding solution was prepared by diluting sample =4 (see Table IV) and t h e chromatogram obtained is shown in Figure 4b. I t is evident t h a t the limit of detection is still lower for this sample. In fact, the ESTD method gave 0.01 5 g Pb/imp. gal (s = 0.001), showing t h a t even a t low concentrations of this order, t h e measurements are within one order of magnitude. Thus the method can also be used for the detection of trace amounts of T E L in gasolines. Using atomic absorption (9),t h e noise level was approximately 12% for a sample containing 0.39 kg Pb. Since in many cases the motor octane number is corrected by the addition of lead alkyls other than TEL, it was of interest to determine the response of t h e UV detector t o tetramethyllead (TML) and t o mixed alkylleads (1:1 TEL/
-
-,
I'
0:
1:
,MA
-.s
'
-
1
--
LJV
f
Flgure 6. Baseline disturbance due to saturate components in Turbofuel A. (a, Unleaded sample, (b) with TEL added. S = saturates, MA = monoaromatics, DA = diaromatics, TA = triaromatics
T M L ) . T h e calibration curves for these mixtures using the DuPont and Ethyl Corporation samples are shown in Figure 5. I t is seen that the response to TML at the wavelength used is about 13% of t h a t for T E L , while t h a t for t h e 1:l T M L / T E L sample is about 48% of that for TEL. Thus the method cannot be used for the determination of lead alkyl contents in cases where the type of lead alkyl present is not known. On t h e other hand, because of its simplicity and speed, it might be a method of choice for internal production checks a n d similar applications. Since the T E L peak appears in the chromatogram together with the peak of saturates, the influence of the saturate matrix on the UV detector response for T E L was also studied. For this purpose, alkylate, reformate, light cracked naptha (LCN), unleaded gasoline, a n d turbo fuel A were used as sample solvents. None of the usual blending components exerted any influence on the accuracy of the measurements. In contrast t o these results, injection of turbo fuel A produced a disturbance of the UV baseline which follows approximately the first derivative curve of the saturate peak, as shown in Figure 6. In this case, the integrator cannot be used since it will not integrate t h e negative portion of t h e disturbance which appears a t t h e foot of the ascending branch of t h e T E L peak, but will only integrate t h e positive part of t h e disturbance curve and give higher results. Repeated injections of turbo fuel A gave integrator counts simulating the presence of T E L a t a level of 0.28 g P b / i m p . gal with a deviation of 0.004. Sample =9, Table IV, containing 1.92 g P b / i m p . gal gave a value of 2.25 g Pb/imp. gal upon integration, giving a relative error of 17%. This adverse influence can be eliminated by determining t h e contribution of the disturbance t o t h e integration and correcting the results accordingly. In the above case, t h e corrected value was 1.97 g P b / i m p . gal and the relative error was 2.5%. LVhen peak heights are measured
in such cases, the problem does not arise since peak height measurements are done a t t h e zero value of t h e disturbance (compare t h e results in Table IV). When a single beam detector (Perkin-Elmer, model LC-55) was used, t h e disturbance (caused most probably by refractive index changes) nearly completely disappeared. Table IV also shows t h e results of measurements on t h e same sample made on subsequent days and after a week. The good agreement shows t h a t the time factor is not important. T h u s the standard deviation for t h e three consecutive measurements was 0.03 (at the 1.98 g Pb/imp. gal level) and t h a t for 5 measurements made on the same day was in t h e range 0.004-0.02 for most samples, depending mainly on the size of sample injected. I t tended towards the higher values if t h e P b concentration exceeded 3 g/gal. T h e most significant aspect of these determinations is t h e fact t h a t t h e analysis proper involves only one operation: injection of a 5-pL sample (or calibration standard) in t h e chromatograph. If proper precautions are taken (wiping of the external surface of the needle, complete elimination of air bubbles between the syringe plunger and the sample plug in the syringe), the injection can be made with a precision better than 1% (vol). Since t h e method consists of only one operation, it can also be expected that the reproducibility of the measurements in a corroborative study should be better than in most of the other methods described in ASTM standard methods. When using the E S T D method, t h e nonlinearity of the calibration curve for samples containing more than 2.5 g Pb/imp. gal can be easily circumvented by correspondingly adjusting the sample size. Normally, however, because of Canadian governmental regulations, the amount of P b should not exceed 3.5 g Pb/imp. gal of gasoline. The accuracy in this range is still excellent if the calibration curve is used, or if the sample size is reduced. Another alternative is to calibrate the measurement by injecting a standard T E L solution of similar concentration. T h e calibration fact,or for T E L remained unchanged over a period of 8 months. T h e analysis also gives first hand information about the sample as a whole and has the additional advantage t h a t a com.mercia1 liquid chromatograph can be used without any ad.aptations.
ACKNOWLEDGMENT Thanks are due to F. Seller of ESSO Refinery, Edmonton for kindly supplying samples of refinery streams and T E L mixes and E. M. Lown for helpful suggestions.
LITERATURE CITED (1) (2) (3) (4)
(5) (6)
(7) (8) (9) (10) (11) (12) (13) (14)
ASTM 0-2547-70, Vol. 17. ASTM D-526-70. Vol. 17. ASTM D-1269-61(68), Vol. 17. D. T. Coker, A n d Chem., 47, 386 (1975). Y. K . Chau. P. T. S. Wong, and H. Saitoh, J . Chromatogr. Sci., 14, 162 (1976). G. Castello. Chim. I n d . , 51, 700 (1969). ASTM D-2599-71, VOI. 17. ASTM D-3237-73, Vol. 17. C. Botre. F. Cacace, and R. Cozzani, Anal. Lett., 9 , 8 2 5 (1976). EPS 1-AP-73-3 (modified March 1975). W. H. Thompson, J . Chem. Soc., 790(1934). P. A . Leighton and R. A. Mortensen, J . Ani. Chem. Soc., 5 8 , 448 (1936). A. B. F. Duncan, J . Chem. Phys., 2 , 636 (1934). L. Riccoleoni, Garr. Chim. Ita/., 71, 6Cl6 (1941).
RECEIVED for review January 24, 1977.. Accepted July 5, 1977. This work was supported by the National Research Council of Canada.
ANALYTICAL CHEMISTRY, VOL. 49,
NO. l:!,
OCTOBER 1977
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