1894
Anal. Chem. 1085, 57, 1894-1902
linear range and basicity equilibria must be reduced. Photoionization (PI) sources in gas chromatographic detectors have linear ranges of over lo6 and a PI source may result in greater linear ranges in IMS sensing for N2H,and MMH. Use of PI sources while selective in choice of energy may also be useful in removing equilibrium selectivity in creation of product ions. Registry NO.MMH, 60-34-4;NzHd, 302-01-2;“8,7664-41-7; MeOH, 67-56-1. LITERATURE CITED (1) Schmidt, E. W. ”Hydrazine and Its Derlvathres”; Wlley-Intersclence: New York, 1984. (2) Sutton, W. L.; Patty, F. A. “Industrlal Hygiene and Toxlcobgy”; Irish, D. O., Fassett, D. W., Eds.; Wlley: New York, 1966; Vol. 2. (3) Voltrauer, H. N. Report; Aerochem-TP-394 SAM-TR-80-13 1980. (4) Suggs, H. J.; Luskus, L. J.; Klllan, H. J. Am. Ind. Hyg. Assoc. J . 1980, 4 1 , 879. (5) Stetter, J. R.; Tellefsen, K. A,; Saunders. R. A.; Decorpo, J. J. Talanta 1979. 26. 799. (6) Holtzclaw; J. R.: Rose, S. L.; Wyatt, J., Sr.; Rounbehler, D. P.; Flne, D. H. Anal. Chem. 1984, 56, 2952.
(7) Anderson, K.; Hallgren, C.; Levln, J.; Nlllson, C. Anal. Chem. 1984, 56, 1730. (8) Menyuk, N.; Klllinger, D. K.; OeFeo, W. E. Appl. Opt. 1982, 21, 2275. (9) Luskus, L. J.; Klllan, H. J. Report; SAM-TR-76-21; AD-A027824 N7716469; 1978. ( I O ) Karasek. F. W. Int. J . Envlron. Anal. Chem. 1972, 2 , 157. (11) Dam, R. J. In “Plasma Chromatography”; T. W., Ed.; Plenum Press: New York, 1984; pp 177-213. (12) Elceman, Q. A.; Leesure C. S.; Vandlver, V. J.; Rlco, G. R. Anal. Chlm. Acta, In press. (13) Rlco, G.; Elceman, Q. A.; Leasure, C. S.; Vandiver, V. J. Anal. Instrum. 1985, 13, 289. (14) Marsh, W. R.; Knox, 6. P. “USAF Propellant Handbooks, Hydrazine Fuels (U)”;AFRPL-TR-69-149; AD-507864; 1970; Vol. 1. (15) Hunt, D. F.; McEwen, C. N.; Upham, R. A. Tetrahedron Lett. 1971, 47, 4539. (16) Heller, S. R.; Mllne, Q. W. A. “EPAINIH Mass spectral Data Base”; U.S.Government Prlntlng Offbe:Washhgton, DC, 1978; p 2. (17) Vandiver, V. J.; Leesure, C. S.; Elceman, Q. A. Int. J . Mess Specfrom. Ion Rocesses , In press. (18) Mollna, L. T.; Qrant, W. B. Appl. Opt. 1984, 23, 3893.
RECEIVED for review February 4, 1985.
Accepted April 29,
1985.
Mass Spectral Characterization of Petroleum Dyes, Tracers, and Additives T. L. Youngless,* J. T. Swansiger, D. A. Danner, and Mariano Greco
Gulf Research and Development Company, P.O. Drawer 2038, Pittsburgh, Pennsylvania 15230
Petroleum dyes, additlves, and tracers are Important for IdentHying gacroiines in spill and contamlnation problems. Hlgh-resolution mass spectrometry (HRMS) was used for the characterizatlon of 21 commercial petroleum dyes. Many contained common chromophores, typically azo or anthraquinone groups, and often dmered only in their degree of alkyl substitutlon. Few dyes were pure and typically contained several chromogens with homologous series of substltuents. A separation method was developed to concentrate the polar fractions containing the additives. Subsequent characterlzatlon of the polar fractlon by GC/MS showed distlnct differences between dMerent gasolines. Various colortesl, tracers were evaluated In terms of detectablilty, soil adsorptlon, and cost. Many tracers exhlwted sdl adsorption and Interferences whlch limited thelr detectabllity. Alcohols in the C8-C10 range were found to be the most sunable tracers with GC/MS detectlon ilmlts of 1 ppm.
In the past, several methods have been developed for environmental monitoring with respect to the detection and effects of petroleum spills. Several components in petroleum have been designated as “passive tags”; these compounds include c20-C40 acyclic isoprenoids, C27+ steranes, and triterpanes (1).These compounds are typically detected by using GC/MS with specific ion plots. Other methods for monitoring the effects and the source of petroleum in the environment include field ionization and field desorption mass spectral fingerprinting (2),identification of thiophenic sulfur compounds by GC/MS (3),GC/MS detection of mono-, di-, and trimethylnaphthalenes, (4)and lead isotope distributions (5). Most of these techniques were developed to determine the source of marine spills, the extent of the spill, and the 0003-2700/85/0357-1894$01.50/0
resulting effects on the environment. Therefore, in the above studies, the techniques were developed with emphasis on the identification of petroleum crude stocks and in most cases have not been applied to identification of gasolines. Techniques for the identification of the source of gasolines are important for several reasons, including spills, excess lead violations, boot-legged fuels, and contamination problems. A variety of methods have been employed for the identification of various gasoline samples and they have met with varying degrees of success. Probably the most common technique is GC fingerprinting. It provides a powerful and simple solution to many problems (6, 7). Chemical ionization mass spectrometry was used as a fingerprinting technique for gasolines with cyclohexane as the reagent gas and it was shown to produce molecular ions for the aromatics and olefins with essentially no saturate components ionized thus producing a fingerprint of the gasoline (8). Leaded fuels can also be identified on the basis of their alkyl lead compound distribution (9). Problems occur with the above identification techniques in several circumstances. GC and GC/MS are sometimes unable to distinguish between different gasolines produced from similar crude slates. Lee et al. found several different gasolines (regular and premium) to contain essentially the same hydrocarbons with differences only in their relative concentrations (10).The CI mass spectra of these gasolines would also be similar. Problems may arise with identification of the fuel based on the alkyl lead distribution because different manufacturers may use the same lead package. Gasoline dyes are often useful for fuel identification. Leaded fuels are required by federal law to be distinctively colored to indicate the presence of alkyl lead compounds. The color is not specified; however, minimal dye concentrations to meet Surgeon General requirements are specified (11). Typical concentrations for a dry dye range from 0.7 to 1.3 0 1985 American Chemical Soclety
ANALYTICAL CHEMISTRY, VOL. 57, NO. 9, AUGUST 1985
g/100 gal. Although gasoline dyes have been in use for more than 50 years, the literature contains relatively few references to them. Most of the recent literature concerning petroleum dyes is contained in patent disclosures. These describe novel diazo dyes which tend to resist removal from soil or water contact but are still amenable to TLC separation from the fuel (12-14). In some cases, thin-layer chromatography of the gasoline dyes and comparision of their Rf values are sufficient to identify a fuel (15). Comparison of the TLC Rf values of the dyes is complicated when different gasolines contain similar dye packages and is impossible if identical dye packages are used. Identification is further complicated by mixing different fuels and contact with the soil. Analysis of the dyes can be difficult when the fuel has percolated through the soil and become contaminated by other polar components which obscure the dye bands. These same compounds may cause a shift of the dye Rf values. In addition, while TLC is adequate for separating different dye colors, the technique sometimes lacks the resolution to separate structurally similar dyes varying only in alkyl substitution. The typical petroleum dyes are nonionic and can be readily vaporized into the electron impact ion source without apparent thermal degradation making their analysis by mass spectrometry a viable technique. Unleaded fuels can present other problems in identification since they do not contain a lead package and are not required to contain dyes. The addition of a unique chemical compound to the fuel which will act as a tracer can be used to unambiguously identify the fuel. Several tracers are available commercially; however, many are prohibitively expensive for routine addition to the fuel and suffer severe adsorption problems when in contact with soils. Thiophane has been proposed as a tracer to detect leakage from gasoline storage tanks (16);however, the suggested concentrations of 0.1-1 % make it too expensive for routine fuel addition. Further, the “substantially similar” definition in the Clean Air Act has been modified by an interpretive ruling with respect to unleaded gasolines to allow manufacturers to determine whether additives are subject to restrictions of the Act (17). If an additive contains only C, H, N, 0, and S, such that the total additive content (other than hydrocarbons, alcohols, and ethers) is less than 2500 ppm of the fuel and the sulfur additive contributes no more than 15 ppm sulfur to the fuel, then the additive is defined as substantially similar. Tracers containing heteroatoms such as chlorine have been suggested (18);however, the use of heteroatomic containing species which do not fit the “substantially similar” definition of the Clean Air Act may require petition for approval by the EPA. From the above discussion it can be seen that additional information is required to identify certain gasolines. This work concerns the identification and fingerprinting of the polar components of leaded and unleaded gasolines as an aid in the identification of unknown gasolines and demonstrates the feasibility of a tracer for routine addition by the manufacturer. High-resolution mass spectrometry (HRMS) is applied to the characterization and identification of petroleum dyes used in leaded fuels and a procedure is developed using low-resolution GC/MS for distinguishing unleaded fuels on the basis of their polar compound distributions. The use and GC/MS detection of a tracer which is unique to the fuel, economically feasible, and resistant to soil adsorption are also shown. EXPERIMENTAL SECTION Reagents. The acetone, toluene, and hexane were ACS certified reagent grade. The methanol and methylene chloride were both HPLC grade. Apparatus. Dry packed silica gel columns were used for the liquid chromatography (Sep-PAK Waters Associates, Milford, MA) and precoated 250-pm silica coated plates were used for the thin-layer chromatography.
1895
HRMS. The HRMS spectra were obtained with a Kratos MS50 spectrometer and a Data General Nova 4X data system using Kratos DS-55 software (rev 6.71). All samples were run at 70-eV ionizing voltage, 300-pA trap current, 8-kV accelerating voltage, and a source temperature of 250-300 O C . Direct probe samples were runwith a scan rate of 10 s/decade over a mass range of m/z 32 to 755 and a 10 000-Hz band width at a resolution of 20 000 using a programmable temperature ramp from 50 to 350 “C at 30 OC/min. LRMS. The GC/LRMS spectra were obtained on a Finnigan 4510 quadrupole mass spect\rometer using the Incos data system (software rev. 4.07.82). An ionizing voltage of 70 eV, an emission current of 430 pA, and a source temperature of 150 O C were maintained for data acquisition. The spectrometer was scanned from m/z 50 to 650 at the rate of 0.3 s/decade. Sample sizes of 0.1 FL were injected with 1x)split on a 0.33 mm i.d. X 30 m (0.25 pm film thickness) DX4 fused silica capillary column (J & W ScientificInc., Rancho Cordova, CA) using helium as the carrier gas, A column head pressure of 12 psi was used to maintain a flow of about 1.5 mL/mh. The column temperature was programmed at the rate of 6 OC/min from an initial temperature of 50 OC with a 2-min hold to a final temperature of 230 OC with an 18-min hold. Procedure-Dyes and Polars. The polar fractions of the gasoline samples were obtained by passing 100 mL of gasoline through a silica gel column followed by three 2-mL volumes of a hexane wash and subsequent vacuum removal of the solvent to near dryness. The polars were eluted with three 2-mL volumes of methanol. The three eluates were then combined and evaporated to a volume of 2 mL. A procedure was developed for the separation of dye fractions from gasoline. This consisted of passing 10 mL of the gasoline through 8 silica gel column followed by elution with acetone. Only the colored dye containing bands were collected and the acetone was evaloprated with a nitrogen gas stream. The fraction could be further separated using 250-pm silica gel TLC plates with toluene as the mobile phase. The reference dyes were analyzed as received or after TLC separation as described above. Procedure-Tracers. Color IA (DuPont). A 1WmL aliquot of a sample of gasoline containing 3 ppm of color IA was extracted with 10 mL of a 75% ethylene glyco1/25% water mix. The pH was adjusted to 4.5 with 0.1 N HCl to give a light blue color. Color IAR (Du Pont). The same procedure as for color IA was followed and upon acidification a light red color developed. Calcofluor White R WP (American Cyanamid). A 3 ppm solution of the tracer in gasoline was detected by dropping 2-3 mL onto filter paper and flashing off the volatiles. A fluorescent spot was observed under UV light. Calco Rhodamine B Base (American Cyanamid). A 3 ppm solution gave a light pink color under visible light and fluoresced under UV light. Marker EB (Morton). A 3 ppm blend of the tracer in gasoline was extracted with 5 % NaOH using a 201 fuel to extract ratio to give a strong purple-blue color.
RESULTS AND DISCUSSION Leaded Fuels-Dye Analysis. High-resolution mass spectral fingerprints were obtained for 21 commercial dyes. The dyes were found to range in molecular weight from 200 amu to 700 m u . Table I shows a summary of the results for the 21 dyes analyzed. The information was tabulated from the average spectrum for each dye using information from specific ion plots when necessary as described below. These average direct probe microdistillation data were produced by averaging the individual spectra obtained as the sample distilled off the probe. For each of the 21 dyes, the table shows the empirical formulas determined for the major dye componenta and some characteristicfragment ions along with their relative intensities. Additional components varying in the number of alkyl carbons are also listed along with their relative intensities. All components listed for a given dye including alkyl-substituted species have relative intensities listed with respect to the base peak in the averaged spectrum. The table also indicates structures for the various dye components as
1898 c ANALYTICAL CHEMISTRY, VOL. 57, NO. 9, AUGUST 1985
Table I. Petroleum Dye Components ions mass
intensity
374.1743 254.0929 121.0891 478.2732
40 28 100 2
I
C4 (40)
I1
c13 (2)
378,2732
60
I1
C6 (231, C11 (40), C12 (60), C13 (23)
421.2028 261.1028 674.4559 589.3542
65 100 12 24
V
c19 (12)
M+
346.2045
31
I11
fragments
317.1654 303.1497 289.1341 171.0558 115.0548
16 53 100 13 16
374.1743 254.0929 121.0891 254.0929 121.0653 416.2828 289.1341
42 29 100 8 16 5 15
248.0949 171.0558 115.0548
85 27 72
I11
CO (85)
416.2828
29
I11
C11 (12), C12 (29), C13 (14), C14 (6), C15 (5)
289.1341
100
248.0949 171.0558 115.0548
90 22 68
I11
CO (go), phenyl (11)
262.1106 171.0558 115.0548
100 45 93
I11
CO (63), C1 (100)
478.2732
70
I1
C10 (13),C11 (45), C12 (70), C13 (25), C14 (10)
fragments 10. red B a. M+
421.2028
15
394.1793
100
fragments
275.1184 261.1028
45 25
380.1637 261.1028 322.1681 307.1446
100 83 30 50
I1
c 5 (100)
VI
C6 (30)
380.1637 261.1028
100 84
I1
c 5 (100)
478.2732
80
I1
C11 (45), C12 (801, Ci3 (35), C14 (lo), C15 (7), C16 (lo), C17 (8), C18 (6), c19 (lo), c20 (101, c21 (2)
421.2028
100
dye
1. orange A a. M+ fragments b. M+ 2. orange B a. M+ fragments
b. M+ fragments 3. orange C a.
4. orange D a. M+ fragments b. M+ fragments
c. M+ fragments 5. orange E a. M+ fragments 6. orange F a. M+ fragments 7. orange G a. M+ fragments
8. orange H a. M+ fragments 9. red A a.
M+
11. red C a. M+ fragments b. M+ fragments 12. red D a. M+ fragments 13. red E a. M+
fragments 14. bronze A
structure
I
alkyl substitution carbons (intensity)
C4 (42)
IV I11
I1
ANALYTICAL CHEMISTRY, VOL. 57, NO. 9, AUGUST 1985
1807
-
Table I (Continued) dye a. Mt
ions mass
intensity
478.2732
100
structure I1
alkyl substitution carbons (intensity) C5 (la), C7 (48), c10 (221, c11 (55), C12 (loo), C13 (32), C14 (B), C15 (91, C16 (7), C17 (4), C18 (lB), C19 (ll), c20 (71, c21 (4)
fragments b.
Mt fragments
c. Mt
fragments 15. bronze B a. Mt
421.2028 374.1743 254.0929 121.0891 416.2828 289.1341 478.2732
87 48 58
100 18
I
C4 (48)
I11
C12 (29)
11
C5 OB), C1Z (loo),
55 100
C13 (36), C14 (51, C15 (7), C16 (61, C17 (41, C18 (101, c i 9 (la) 421.2028
90
276.1262 247.0871 171.0558 115.0548 380.1637 261.1028 115.0548
100 35 15 60
I11
c2 (100)
12
I1
c 5 (12)
a. Mt fragments 18. blue B a. Mt
322.1681 307.1446
60 100
VI
C6 (60)
462.3246
55
VI
C13 (6),C16 (55), C20 (20), C22 (15), C23 (9), C24 (7)
fragments
363.2072 265.0977
100 60
462.3246
53
363.2072 265.0977
100 82
Mt
674.4559
83
fragments
589.3542 443.2936 252.1262
100 10 25
253.1579 238.1344 148.1126
100 66 100
fragments 16. bronze C
a. Mt fragments b. Mt
fragments
9 6
17. blue A
19. blue C
a. Mt
fragments 20. yellow A a.
21. yellow B a. Mt
fragments
shown in Figure 1. These structures show only the parent structure with minimal alkyl subetitution. The number of alkyl carbons reported in the table is the number of additional carbons with respect to these structures. Thus,in many cases the major component is an alkyl-substituted derivative of the parent structure and will also be listed with the other alkyl-substituted components. The empirical formulas for the dyes suggested azo, diazo, and anthraquinone type structures. The azo and diazo dyes exhibited cleavage at the azo group with fragments resulting from cleavage at both ends of the azo linkages. Fragments were also present which could be formed as the result of cleavage between the two azo nitrogens and then recombination with two hydrogens to form the amine. These results agree with the e x p W fragmentations for am and diazo dyes (19). The anthraquinone dyes exhibited strong molecular ions and fragmentation of substituents consistent with anthra-
VI
V
C19 (B), C20 (83), C21 (15)
VI1
c 4 (100)
quinones with alkylamino groups (19). Examination of the individual spectra as a function of the probe temperature yields information on the individual dye componentrs. This is often necessary to distinguish between dyes of the same color and to identify dyes in a complex mixture such as gasoline. Detailed analysis of the probe microdistillation data shows that several of the dyes consisted of more than one component. Figure 2 shows a comparison of the specific ion plots for the molecular ion(s) of a yellow dye cantaining a single component vs. a multicomponent bronze dye. The higher molecular weight bronze dye at m l z 478 distilled off a t the highest probe temperature. The components at mla 416 qnd 374 are adequately resolved to show they are not fragment ions from the 478 ion. Fragment ions are easily distinguished from molecular ions by this method since fragment ions such as mlz 421 would follow the same distillation curve as the 478 molecular ion. This demonstrates
1898
ANALYTICAL CHEMISTRY, VOL. 57,
NO. 9, AUGUST 1985
OH
.nu
I
,
,
,
,
,
,
I
.
.
,
HO. 8
R
-
90
oy\
-
IS, 70
Figure 1. Petroleum dye structures.
the general application of the specific ion plots and the probe microdistillation technique for determining the number of compounds in a dye and the fragment ions that belong to a particular molecular ion. Difficulties are encountered when the molecular ions are not resolved from one another. Dyes of different colors and molecular weights could be resolved off the probe with little difficulty; however, several of the dyes were found to be structurally identical except for varying alkyl substitution. Figure 3A shows the specific ion plot for the prominent ions of a complex blue dye. Although the plot demonstrates some resolution, the interpretation becomes much easier if the dye is first separated by TLC and then the individual components analyzed by HRMS. TLC of this dye produced six distinct bands, and subsequent HRMS analysis of the bands showed them to consist of an anthraquinone type structure as shown in Figure 3A with alkyl substitution varying between 2 and 16 carbon atoms. The molecular ions of the six species present in the dye occurred at m / z values of 462,420,378,364,322, and 266. The spectrum of the unseparated dye showed ions for all of the components present but at 20 000 resolution it was impossible to determine if a given ion was a fragment ion, a carbon-13 containing ion from an intense cleavage fragmentation, or the molecular ion of a lower molecular weight component in the dye mixture. A resolution of 60000 is required to resolve even the simplest case at m/z 266. Figure 3, parts B-D, shows the specific ion plots for the three TLC bands containing the 462,364, and 266 molecular ions. Figure 3B shows the 462 molecular weight component. The ion at m / z 364 shows an intensity consistent with the calculated
I
s
IO
IS
20
25
30
35
40
45
Scan Number
Flgure 2. Specific ion plot for single component yellow dye (A) and multicomponent bronze dye (e).
intensity for the 13Cion from the 363 fragment ion. Likewise, the 266 ion in Figure 3C is the I3C fragment ion from the 364 molecular ion. Figure 3D shows the plot for the 266 molecular weight component. Unleaded Fuels-Polar Analysis. Figure 4 shows the reconstructed ion chromatograms for the analysis of the polar components of three unleaded fuels consisting of fuels A, B, and C. Each of the gasolines shows distinctly different reconstructed ion current ( R E ) traces, thus providing unique information sufficient to distinguish between the gasolines. Fuel C (Figure 4C)intensities were scaled up by a factor of 3 relative to fuels A and B due to the high concentration of a single component. The quantitation of the various components is achieved by assuming unit sensitivity for each compound and calculating the percent of the area of each peak relative to the sum of areas of the peaks. The peaks were identified by using the 32 767 compound NBS mass spectral library. Tentative identifications were assigned based on the results of the library search in conjunction with relative retention times determined for phenolic and nitrogen compounds on polar columns (20, 21). Table I1 lists the com-
ANALYTICAL CHEMISTRY, VOL. 57, NO. 9, AUGUST 1985
I
S
I
II
15
21
"
,
1809
'
25
Scan Number 111
98
81
71
-2 *
68
51
w
:a
-*
$
38
21
I1
1
I
a
II
I5
28
2s
Ssrn WumboP
Figure 3. Specific ion plot for complex blue dye (A), TLC separated 402 molecular weight component (B), 304 molecular weight component (C), and 200 molecular weight component (D).
pounds identified for the peaks in Figure 4 along with the quantitation results. The polar compounds identified in the fuel are both naturally occurring polar compounds and fuel additives. Fuel additives include antiknocks, antioxidants,metal deactivators, corrosion inhibitors, and antiicers. Antioxidants such as p-phenylenediamine and highly hindered phenols are used to prevent gum formation by quenching the free radicals produced by olefin breakdown which promote the oxidation initiated by trace quantities of hydroperoxides (22). Metal deactivators include such compounds as disalicylpropanediamine which chelate with metals like copper to prevent fuel oxidation by metallic catalysts. Corrosion inhibitors are usually long chain molecules which contain a strong polar group. They function with the polar group oriented toward the metal surfaces and the hydrophobic portion oriented toward the fuel. Typical corrosion inhibitors include carboxylic acids and diimides. Antiicers consist of both freeze point depressants and surface active ingredients. Examples of freeze point depressants are short chain n-alcohols. Examples of surface active antiicers are amines and ethoxylated alcohols
with long hydrocarbon chains. Some of these additive types were identified in the three gasolines. All of the fuels contained a series of alkyl-substituted phenols which may be part of an antioxidation fuel additive package. Fuels A and B contained identical phenolic compounds, and significant differences in concentrations were noted for only a few compounds. Fuel C was found to contain different phenolic compounds in the higher molecular weight regions and a strikingly different quantitative distribution of the lower molecular weight phenols with 3-methylphenol accounting for over 50% of the total ion current. Fuel C contained a series of ethoxylated alcohols quite distinct from fuels A and B. Fuels A and B contained significant quantities of amines. Fuel A contained more pyridines in the lower molecular weight region than fuel B. Fuel B contained more anilines than fuel A, while fuel C contained only small quantities of amines. Metal deactivators such as disalicylpropanediamine were not detected. This compound would probably not elute from the column under the GC conditions used for this work. Carboxylic acids used as corrosion inhibitors would probably not be detected unless the polar
1000
ANALYTICAL CHEMISTRY, VOL. 57, NO. 9, AUGUST 1985
Table 11. Polar Components in Gasoline6 by GC/MS peak no. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
T1 24 25 26 27 28 T2 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58
59 60 61 62
% TIC
compound name 2-methylpyridine 3-pentanol ethylmethylbenzene 2-ethoxyethanol 2,6-dimethylpyridine 1-pentanol 2-ethylpyridine 1,3,54rimethylbenzene 2-propoxyethanol 2-ethyl-6-methylpyridine ethanol 2-ethoxyacetate NJV-dimethylformamide 2,5-dimethylpyridine 3,Ci-dimethylpyridine 2,3-dimethylpyridine
fuel A
fuel B
1.11
0.35
0.16
0.44
0.04 4.10 0.24 0.94 1.16
0.26 0.17 0.21 0.26 0.17
0.03 1.83
2,4,64rimethylpyridine 2,3,6-trimethylpyridine 2-butoxyethanol
0.21 0.07
2-ethyl-4,6-dimethylpyridine
0.30 0.06
5.82 0.09
3-ethyl-2,6-dimethylpyridine tetrahydro-1-oxide thiophene
0.51 0.57 0.40 1.00 0.14 4.15 0.49
fraction was derivatized to form the corresponding methyl esters. Tracers are useful for both leaded and unleaded fuels, particularly for unleaded fuels because of the difficulties associated with their identification. Five commercially available tracers were evaluated, and the results are shown in Table 111. All of the tracers gave positive results from the laboratory spiking experiments; however, they all suffered
0.62 5.04 9.46 3.84 2.80
0.94 0.02 0.83 0.77 0.15 0.15
5-ethyl-2-methylpyridine methylisoquinoline 2-methylpropanoic acid 2,2-oxybis(ethanol) phenol 2-methylphenol N-ethyl-2-methylaniline 2-ethylphenol 3-methylphenol 2,5-dimethylphenol 3,5-dimethylphenol 3-ethylphenol tetrahydro-1,l-dioxide thiophene 3,4-dimethylphenol 2,3,5-trimethylphenol 2 4 l,l-dimethylethyl)-6-methylphenol 2-ethyl-5-methylphenol 4-propylphenol 4-(l,l-dimethylethyl)-2-methylphenol 3-(l,l-dimethylethyl)phenol 3-ethyl-5-methylphenol 44 1-methylpropy1)phenol 4-(l,l-dimethylethyl)phenol
0.12 0.07
3.63
2-(2-ethoxyethyl)ethanol naphthalene aniline 1-decanol tracer 4-methylaniline l-(2-butoxyethoxy)ethanol N-methylaniline 3-ethyl-4-methylpyridine 2-methylaniline 2,3,54rimethylpyridine 3-ethyl-5-methylpyridine 2,6-dimethylphenol isoquinoline
0.11 0.06 0.05 0.07
0.20
4-hydroxy-2-methyl-2-pentanol
acetic acid 1-(2-methoxy-1-methy1ethoxy)propanol 2-ethyl-1-hexanol I-octanol tracer 2-(2-methoxyethoxy)ethanol 1,2-propanediol
fuel C
0.41
11.4 5.65 5.14 0.29 0.29 1.20
0.04 0.12
2.65 0.46
12.50 12.30 0.10 14.50 20.80 2.81 8.25 4.10 0.99 2.96 0.76
3.37 7.92 0.84 8.46 10.60 1.51 5.31 2.75
1.37 0.62
0.92 0.44
1.83 0.44
0.04 0.41 6.24 3.13 11.10 51.40 0.03 0.21 0.10 0.03 1.88 6.38 0.04
0.46 0.07
0.31 0.05 0.21
adsorption effects when 100 mL of the 3 ppm tracer containing fuels were slowly percolated through a column containing 10 g of soil. The adsorption problems together with the economic considerations suggest that these tracers are better suited for use in solving specific problems such as leak testing of storage tanks,etc. The choice among the above noted tracers depends on the specific problem and fuel involved. Figure 4A shows the GC/MS detection of an economical
ANALYTICAL CHEMISTRY, VOL. 57, NO. 9, AUGUST 1985
RIC
1
441145
1001
A
471148
B
I
53
I
C
4
30
i
26
Flgure 4. Total Ion chromatograms of the polar fraction of fuel A with 10 ppm tracer of 1-octanol (Tl) and l-decanol (T2) (A), fuel B (B), and fuel C (C).
Table 111. Colorless Tracers
tracer color IA color IAR calcofluor white RWB Calco rhodamine B base marker EB
detection limit, PPm
means of detection
cost, $/lb
3 3 3
blue color red color UV fluor
24.50 24.95 20.25
