(5) 0.E. Newfield, Med. J. Aust., 1, 257 (1967). (6) A. Ito and K. Ueno, Bunseki Kagaku, 19, 393 (1970). (7) “Analysis of Calcium in Water”, Hach Chemical Company, Ames, Iowa. (8) “Stability Constants”, The Chemical Society, London, 197 1 and 1964. (9) “Standard Methods for the Examination of Water and Wastewaster”, American Public Health Association, New York, N.Y., 14th ed, 1975. (IO) S. B. Sawin, Talanfa,8,673 (1961); H . Onishi and C. V. Banks, Tabnta, 10, 399 (1963).
(11) J. C. Van Loon, J. H. Galbraith, and H. M. Aarden, Analyst (London),96, 47 (1971). (12) R. Belcher, K. P. Ranjitkar, and A. Townsend, Analyst(London), 101, 666 (1976).
for review January 18,
Accepted March
97
1977.
Determination of Vanadium in Athabasca Bitumen and Other Heavy Hydrocarbons by Visible Spectrometry Edward W. Funk” and Ernest0 Gomez Corporate Research Laboratories, Exxon Research and Engineering Company, Linden, New Jersey 07036
A slmple and rapid method has been developed to estimate the vanadium concentration in heavy hydrocarbons. It is based on an empirical correlation obtained by use of a spectrophotometer operating in the visible reglon. A separate correlatlon must be developed for each hydrocarbon. The utlllty of this new technique Is for experimental work requiring a rapld estlmde of vanadlum for a large number of similar samples.
separated from the deasphalted bitumen by centrifuging the mixture for 15 min at 2000 rpm. Use of higher pentane/bitumen ratios had very little effect on the vanadium concentration of the deasphalted bitumen. Use of n-heptane at the same conditions just described for n-pentane deasphalting gave a deasphalted bitumen containing 150 ppm of vanadium. High vanadium concentrations were obtained by mixing npentane asphaltenes (V = 605 ppm) with toluene-extracted bitumen and also by using samples of the n-pentane and n-heptane asphaltenes.
Pate1 ( I ) recently published a new spectrophotometric method for the determination of the bitumen content of Athabasca tar sands. The method is particularly useful for small samples where weighing the toluene-extracted bitumen is difficult. Its disadvantage is that a separate correlation is required for tar sands with even slightly different processing histories. The purpose of this work was to explore the extension of the spectrophotometric method to tar sand bitumen that has been deasphalted under different conditions. For such similar samples, it is expected that correlations will exist between various properties of the deasphalted bitumens. Finally, it is hoped that what is learned using deasphalted bitumens can also be applied to other heavy hydrocarbons.
RESULTS
EXPERIMENTAL The experiments were made using a Beckman DB-G spectrophotometer operating at a wavelength of 530 nm. The optical cell was of silica, acta grade, and the cross-section was 10 mm. For all experiments, reagent-grade toluene (Matheson,Coleman and Bell) was used as the standard solution. Reagent grade toluene was also used to dilute the bitumen samples. This was done by first preparing a solution of 0.08% (w/v) of oil in toluene and then, as desired, diluting further 50-mL samples of the solution. The sample of Athabasca tar sands was obtained from Great Canadian Oil Sands, Alberta, Canada. The bitumen was extracted from the tar sands using a Soxhlet extractor with reagent-grade toluene. The extracted bitumen had a vanadium concentration of 205 ppm as determined using emission spectroscopy and atomic absorption. Samples of the other heavy hydrocarbons were obtained from Exxon Research and Development Laboratories, Baton Rouge, La. Deasphalting of the heavy hydrocarbons (e.g., Athabasca bitumen) was accomplished using paraffinic solvents. N-Pentane at a solvent/bitumen weight ratio of 10 gave a deasphalted bitumen containing 60 ppm of vanadium; the asphaltenes were 972
ANALYTICAL CHEMISTRY, VOL. 49, NO. 7, JUNE 1977
Tables I to I11 summarize the experimental results. The vanadium and nickel concentrations were determined using emission spectroscopy and atomic absorption.
DISCUSSION Figure 1 presents the weight concentration of tar sand bitumen dissolved in toluene as a function of absorbance a t 530 nm. It is interesting that the lines in Figure 1 show a definite trend with respect to vanadium concentration. This suggested cross-plotting the data shown in Figure 1 for a constant bitumen percentage, chosen to be 0.04%. Figure 2 gives the resulting correlation between vanadium concentration and absorbance for the range of 65 to 400 ppm vanadium. This correlation is useful for the rapid determination of the vanadium concentration of a deasphalted tar sand bitumen. The use of Figures 1 and 2 requires several precautions. First, the correlation is likely to change with the source of the Athabasca tar sands and also possibly the depth within a given deposit. Also, should a sample be uncharacteristically high in metals (for example, Fe) the correlation could give incorrect results; i t must be remembered that it is essentially an empirical correlation. Therefore, Figures 1 and 2 are useful for rapid evaluations of results but subsequent check of samples by traditional analytical methods is also necessary. The results of Table I1 show there is a good correlation between nickel and vanadium concentrations of the tar sand bitumen samples. These data could be plotted and the resulting correlation used in conjunction with Figure 2 to estimate nickel concentration. The above correlation procedure can be applied to other heavy hydrocarbons. Figure 3 shows hydrocarbon weight percentages in toluene as a function of absorbance for tar sand
Table I. Spectroscopic Data (Absorbance at 530 nm)
v, Hydrocarbon
PPm
Athabasca bitumen
60 103 150 205 350 639 58 485 280
Arabian crude Job0 crude Tiajuana resid
Weight %, w/v
Ni, PPm 27 44 60 75
... *.. ... ...
278
0.02
0.03
0.04
0.05
0.06
0.040 0.075 0.115 0.145 0.275 0.5 60 0.095 0.185 0.195
0.056 0.110 0.152 0.212 0.405 0.870 0.140
0.067 0.138 0.202 0.288 0.535 1.090 0.185 0.346 0.365
... ... ... ...
0.098 0.210 0.298 0.418 0.790 1.420 0.278 0.525 0.540
...
0.280
0.660
...
0.236 0.430 0.455
Table 11. Absorbance Data at 530 nm for Athabasca Bitumen at 0.04%in Toluene
v,
PPm 60 75 80 95 103 108 113 118 125 135 150 165 193 195 200 205 235 263 350 639
Ni, PPm
Absorbance
27 33 34
0.067 0.090 0.095 0.120 0.138 0.145 0.158 0.155 0.145 0.208 0.202 0.222 0.282 0.282 0.283 0.288 0.365 0.460 0.520 1.090
...
44 46 42 46 49 60 60 68 75 75
... 75 98 .,.
138 278
ob
0'1
0'3
3l2
014
D15
0Ib
0 ' 7+E
AaSORBANCE
Figure 2. Vanadium concentrationof tar sand bitumens as a function of absorbance 0 10
I EXPERlLlENTAL A T 530 nm
0.08 ~
I ,
Table 111. Absorbance Data at 530 nm for Tiajuana Resid at 0.04%in Toluene
c
PPm
v,
Ni, PPm
Absorbance
83 95 155 203 220 280 398
12 15 21 28 29 37 60
0.120 0.145 0.208 0.282 0.295 0.360 0.540
lol
I
0
E X P E R I I A E N T A L A T 530
I I
0.2
0.4
0.6
08
1.0
I 1.2
1.4
ABSORBANCE
Figure 3. Weight concentration of heavy hydrocarbons as a function of absorbance
81#1,7
ABSORBANCE
Figure 1. Weight concentration of tar sand bitumen as a function of
7
absorbance ABSORBANCE
bitumen, Arabian crude, Job0 crude, and Tiajuana resid (see Table I).
Figure 4. Vanadium concentration of Tiajuana resid as a function of absorbance
ANALYTICAL CHEMISTRY, VOL. 49, NO. 7, JUNE 1977
973
The vanadium concentration can be correlated by preparing a plot similar to Figure 2. For example, Figure 4 shows the vanadium concentration of a function of absorbance for samples of Tiajuana resid which have been deasphalted under different conditions.
LITERATURE CITED (1) M. S. Patel, Anal. Chem., 46, 794 (1974).
RECEIVED for review December 27,1976. Accepted March 4, 1977.
Analytical Studies and Applications of Ferroin Type Chromogens Immobilized by Adsorption on a Styrene-Divinylbenzene Copolymer Joel L. Lundgren and Alfred A. Schllt * Department of Chemistry, Northern Illinois University, DeKalb, Illinois 60 1 15
Of four different representative types of ferroin chromogens tested, 3-( 2-pyridyi)-5,6-diphenyi-l,2,4-triazine (PDT) proved to be the most effectively adsorbed on Amberlite XAD-2. Isotherms for the adsorption of PDT and its iron(I1) chelate on the copolymer were measured and interpreted. Distribution coefficients and retention capacities of PDT coated XAD-2 for various transition metal ions were determined. Effects of pH, different anions, and flow rates on column operation were evaluated. Applications of PDT coated columns include purification of reagents, concentration of trace metal ions from dilute solutions, and group separation of metal ions prior to analysis. The analysis of seawater and of various reagent grade chemicals for trace quantities of iron, cobalt, nickel, copper, and zinc ions is described.
The remarkable ability of Amberlite XAD-2, and other similar high surface area styrene-divinylbenzene copolymers, to adsorb or bind various water-soluble organic substances was first recognized and investigated by Gustafson and coworkers (1).Their investigations convincingly demonstrated the promising utility of XAD-2 as a macroreticular adsorbent for separation and purification of water-soluble organic species. Further studies of significance and practical application were quick to follow. In 1969, based upon his studies of its uptake of nonpolar solvents, Pietrzyk recommended XAD-2 for use as an inert support for reversed-phase chromatography (2). In subsequent papers, Pietrzyk and co-workers reported measurement of the heats of immersion and swelling of XAD-2 (3) and application of XAD-2 to separation of nitro- and chlorophenols ( 4 ) and of organic bases (5) by liquid chromatography. Another early proponent for the use of XAD-2 in analysis, Fritz and co-workers applied it to the analysis of water for various trace organic contaminants (6-8) and also for the liquid-liquid chromatographic separation of gallium, indium, and thallium (9). Ionic resins of the polystyrene type, closely related to XAD-2, also exhibit pronounced binding properties toward uncharged organic compounds. Various studies, particularly those by Walton and co-workers (10-1.2), have revealed that adsorption by polystyrene resins primarily involves the “solvent” action of the polymer matrix for the organic solutes. Ionic groups on the polymer matrix are of secondary importance; their major influence is to promote solvation and 974
ANALYTICAL CHEMISTRY, VOL. 49, NO. 7. JUNE 1977
swelling of the resin. Walton has also emphasized that adsorption is especially pronounced in the case of aromatic hydrocarbons, which he suggests is almost certainly a consequence of a-electron overlap between styrene moieties and adsorbate molecules (13). Consideration of the foregoing led us to believe that XAD-2 should exert appreciable adsorptive affinities toward such highly aromatic compounds as 1,lO-phenanthroline and related chelation reagents and possibly also for their metal ion chelates as well. If true, the analytical possibilities are obvious. Most appealing among these are the following: (1)immobilization of chelation reagents on a solid matrix without recourse to chemical bonding which ordinarily restricts geometries of chelation, preventing formation of fully coordinated species and discouraging strong retention of metal ions, (2) removal of trace quantities of certain transition metal ions from concentrated solutions of electrolytes, possibly without serious adverse competition from other cations, and (3) preconcentration of metal ions from very dilute solutions to enhance the sensitivity of their determination. To explore the many possibilities, four different representative ferroin-type compounds were selected for study: 1,lO-phenanthroline, 2,2’-bipyridine, 2,4,6-tripyridyl-1,3,5-triazine (TPTZ), and 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine (PDT). We present here our findings in these matters together with a number of promising applications that were developed and proved practical in our investigations.
EXPERIMENTAL Materials. The nonionic, macroporous, styrenedivinylbenzene copolymer Amberlite XAD-2 (Rohm and Haas Co., Philadelphia, Pa.) (20-50 mesh) was extracted with methanol for 12 h in a Soxhlet extractor, vacuum dried, and stored in a desiccator. Since the dry copolymer is not readily wetted by water, weighed quantities of the dry adsorbent taken for experimentation were first stirred with methanol for 10 min and then filtered by suction to remove non-imbibed methanol. Treated in this fashion, the samples of copolymer typically retained approximately 0.8 g of methanol per g of dry resin and were readily wetted by water. The 1,lO-phenanthroline, 2,2’-bipyridine, 2,4,6-tripyridyl-striazine (TPTZ), and 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine (PDT) were obtained from the G. Frederick Smith Chemical Co., Columbus, Ohio. Impregnation or coating of the XAD-2 with PDT was accomplished by introducing a methanol slurry of a known weight of dry copolymer into a glass tubular column equipped with a stopcock to control solution flow rate and a plug of glass wool at the top. For each gram of adsorbent, 10 mL of a 0.024 M
