Anal. Chem. 1986, 58,2434-2438
2434
Fast-Atom Bombardment and Chemical Ionization/Fast-Atom Bombardment Mass Spectrometry of Lubricants Royal B. Freas and Joseph E. Campana*'
Naval Research Laboratory, Chemistry Division, Washington, D.C. 20375-5000
Fast-atom bombardment mass spectrometry (FABMS) Is used for the dlrect, rapid, and semlquantltatlve characterlratlon of neat Synthetic base dls and thelr addltlves. Both posttlve and negatlve Ion spectra are lnvestlgated, and whlle the negatlve Ion spectra give less structural lnformatlon, they are more useful for proflllng complex mixtures because of thelr slmpliclty. Lubrlcant addltlves, present at the low percent to parts-per-thousand levels, can be ldentlfled by thelr molecular ions using FABMS on the neat lubricant. The related technique, chemlcal lonlzatlon/fast-atom bombardment mass spectrometry, Is shown to enhance slgnlficantly the abundances of homologous tetraester molecular ions In a Synthetic base oil. This resulting molecular ion enhancement permlts tandem mass spectrometric methods to be used to determine the Isomer composltlon of each homologue. Several appllcatlons of FABMS on Iubrlcants are discussed includlng the use of computer reference FABMS spectra for mixture analysis and the potentlal use of FABMS In trlbochemlstry.
Technological advances during the last decade in mechanics, propulsion, and materials have spawned the requirement and development of high-performance, high-temperature, oxidatively stable synthetic lubricants ( I ) . Additives can improve oxidation resistance, inhibit corrosion and rust, improve wear properties, etc., and they can act synergistically with one another to improve performance, including the enhancement of oxidation resistance through the alkali metal effect (2). Because of the nature of the synthetic base oils, the number of additives, and also the in situ formation of new chemical compounds by base oilladditive and additiveladditive chemical reactions, these lubricants can be very complex chemical mixtures although less complex than petroleumbased lubricants. It is well-established that lubricant performance is related to the formulation, and the chemistry of a lubricant is one of the least-understood phenomena in tribochemistry. Therefore, chemical characterization of lubricants for quality assurance and quality control, trend analysis, and fundamental chemical studies is an important aspect to the science of tribology. Fast-atom bombardment mass spectrometry (FABMS) will be shown to be a direct and simple method to characterize synthetic lubricants. This method has been used to characterize a tremendous variety of complex and intractable biological molecules since its inception (3). Molecular products from matrix interactions with the solute and solute/solute interactions have been reported in FABMS ( 4 ) ,and dissociation constants of weak acids in solutions have been determined by FABMS ( 5 ) . Furthermore, it is generally known that organic salts, acids, and bases dissolved in the matrix result in high abundances of the gas-phase analogues of the Current address: Environmental Research Center, University of
Nevada, Las Vegas, NV 89154.
solution-phase ions (6). These observations suggest that solution chemistry may be studied by using FABMS. There is a unique compatibility of FABMS to the analysis of lubricants. A lubricant base oil is analogous to the viscous liquid matrix used in FABMS. The lubricant additives and the reaction and degradation products of a lubricant are analogous to the sample species in a liquid matrix. Here we report the use of FABMS on neat lubricants as a fast, simple, direct, and semiquantitative method for the characterization of synthetic lubricants and as a method to probe the solution chemistry of the lubricant.
EXPERIMENTAL SECTION The fast-atom bombardment (FAB) mass spectra were obtained with a reverse-geometry, double-focusing mass spectrometer (7) fitted with a saddle-field fast-atom gun (8). Xenon was used as the fast-atom beam, and a resolving power of greater than 1000 was used in all studies. The lubricant samples were applied as liquid (-1 wL) to the FAB direct insertion probe tip, and the unheated probe tip was bombarded by the xenon fast-atom beam (8 keV; 10 wA/cm2). The chemical ionization/fast-atom bombardment technique and experimental method have been described elsewhere (9, IO). During the first several minutes of FAB analysis the relative ion abundances were quite stable and reproducible so they were useful analytically. However, after several minutes of primary particle bombardment, the relative abundances of homologous ion fragments changed such that the ion abundances of the higher homologues increased with respect to the lower homologues. This variation likely is due to bombardment-induced damage and the increased volatility of the lower molecular weight homologues. RESULTS AND DISCUSSION Base Oils. The neopentyl poly01 esters constitute an important class of synthetic base oils. They are used as oils for jet turbines and high-temperature gas turbines, hydraulic fluids, rolling-oil additives, heat-exchange fluids, and hightemperature lubricating greases (Ii). Those oils, based on the pentaerythritol tetraesters, are of interest because of their high-temperature properties and their use in jet turbines. The general structure of the pentaerythritol tetraesters is C(CH,OCOR,)* where each alkyl group, R, or CnHln+l( n = 4, 5 , 6,7, 8, or 9), on the four carboxylic acid moieties, R,COO, of the molecule may be a different alkyl homologue. The chemical composition of the homologous mixture determines many of the base oil properties such as viscosity and flash and pour points. A FAB mass spectrum of the model compound, pentaerythritol tetrapentanoate (PETP) [R, = C4H9],is shown in Figure la. A number of structurally informative ions are observed: the protonated molecule at mass-to-charge ratio ( m / z )473; the abundant loss of a single carboxylic acid moiety from the protonated species ([MH - RCOOH]+ equivalent to [M - RCOO]+) at m / z 371; the acylium ion, [RCO]+ a t mlz 85; and the butyl cation, R+ = [C4H9]+a t mlz 57. The ion peak observed at m / z 287 is a fragment ion (analogous to that at m/z 371) resulting from the loss of a carboxylic acid moiety from the protonated pentaerythritol tripentanoate (triester) impurity. This impurity is present due to incomplete ester-
This article not subject to US. Copyright. Published 1986 by the American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 58, NO. 12, OCTOBER 1986 37,
1 [M-RCOO]'
Table I. Acyl Component Profiles (Relative Amounts) in a Commercial Pentaerythritol Tetraester Base Oil Determined by (A) Positive and (B) Negative Ion Fast-Atom Bombardment (FAB) Mass Spectrometry and Compared to (C and D ) Chemical/Chromatographic Methods"
X I 0 0
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FAB mass spectrometryb [CnH,n+,CnHzn+lNRL-S-300 CO]+ COO]I,
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1
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5 4
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1
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19
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Correlation Coefficients between Data Sets A and B = 0.98 A and C = 0.98 B and C = 1.00
287
455
141
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100
4
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gas chromatography present ref 15' workd
473 .I
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300
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Flgure 1. (a) A fast-atom bombardment mass spectrum of neat pentaerythritol tetrapentanoate (PETP). The protonated molecule [M i-HI+ Is about 5 % of the base peak in the spectrum. A few fragment
ions that are indicative of the structure of the molecule are observed. (Spectra are multiplied by factors shown for direct comparison of absolute abundances.) (b) A fastatom bombardment mass spectrum of neat NRL-S-300, a commercial base oil. Five diagnostic regions in the mass spectrum are observed. They are (a) the protonated molecular region m l z 460-600, (b) loss of an acid moiety from the protonated tetraester, which also includes a contribution from the protonated triester impurity, m l z 360-500, (c) loss of an acid moiety from the triester impurity, m lz 280-360, (d) the acylium ion region m / z 60-240, and (e) the alkyl ion region, m l z 50-200. ification in the chemical production process. The spectrum, shown in Figure la, indicates about 15% triester impurity. The presence of the triester in this compound was confirmed by thermospray liquid chromatography/mass spectrometry; therefore, we confirmed that the origin of the mlz 287 species was from a triester impurity and not from successive loss of carboxylic acid moieties from the protonated tetraester. Figure l b is a FAB mass spectrum of NRL-S-300, a commercial base oil, where a mixture of C5-Cl0 carboxylic acids are substituted randomly about the pentaerythritol nucleus. Again, five diagnostic regions are observed similar to those discussed in the previous example. These ion regions correspond to (a) protonated molecules ( m / z 460-600), (b) loss of an acid moiety from the protonated molecule, [MH RCOOH]+ or [M - RCOO]+ ( m / z360-500), (c) loss of an acid moiety from the triester impurity ( m / z 280-360), (d) the acylium fragment ion [RCO]' region ( m / z 60-240), and (e) the alkyl fragment ion region, R+ ( m / z 50-200). The ion abundances in the protonated molecular region are too weak to be quantitatively useful. The observation of abundant acylium fragment ions, RC=O+, in the FAB mass spectra of these compounds allows acyl component profiling when a variety of homologues are present. Although there may be some interference from the alkyl fragments, R+ or [CnHPn+J+, in the acylium ion region at low resolving power (verified by exact mass measurements), the alkyl ion interferences were found to contribute less than 2% of the acylium ion abundances. Alternatively, the abundant and highly stable carboxylate negative ions, [RCOOI-, that are observed in the negative ion
Similar analytical results were obtained on two other commercial base stocks. bThe values given are the average of the first three spectra obtained on the sample. These data were obtained by the two-step procedure of hydrolyzing the ester linkages and then analyzing the resultant free acids in the mixture by conventional gas chromatography. dThese data were obtained by the two-step procedure of the transesterification of the tetraesters followed by the capillary gas chromatographic analysis of the resultant methyl esters in the mixture.
FAB mass spectrum could be used to profile the acyl components of the base oil. Negative ion mass spectra also have the advantage of exhibiting less fragmentation than the corresponding positive ion mass spectra. The negative ion FAB mass spectrum of the model compound, PETP, contains only two major ions, the [M - HI- parent ion and the carboxylate negative ion, [RCOOI-. A carboxylate negative ion distribution from the NRL-S-300 can be obtained, which is similar to the NRL-S-300 acylium ion distribution. The carboxylate negative ion distribution has the advantage of being relatively free from interferences unlike the acylium ion distribution discussed above. Table I gives the acyl component profile of NRL-S-300 determined by four (A-D) methods. The acylium ion (positive ion) abundances (A) and the carboxylate ion (negative ion) abundances (B) from the FAB mass spectra are given. These results are compared to the profiles determined by a conventional two-step method (C) (12), published previously, which consisted of chemical hydrolysis of the ester linkage to give the free carboxylic acids followed by the quantitative determination of the acid distribution by conventional gas chromatography. Another two-step method (D) involving the transesterification of the tetraesters and the capillary gas chromatographic analysis of the resulting mixture of methyl esters was used also to confirm the analyses. The table shows good agreement between the methods. Two other commercial base stocks were studied also, and the analytical results were of similar quality. The correlation coefficients between the FAB data and conventional method (C) were all 0.97 or better for the three commercial base stocks, although negative ion data were superior to the positive ion data. Thus conventional FABMS provides a simple, direct, rapid, and semiquantitative method to determine acyl component acid profiles of the pentaerythritol tetraester base fluids. The FAB mass spectrometric method can be performed in a few minutes and the results give structural and molecular weight information. The two-step gas chromatographic methods require about an hour, and internal standards are needed because the analysis is based on retention times of peaks rather
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ANALYTICAL CHEMISTRY, VOL. 58, NO. 12, OCTOBER 1986
a .
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200
300
400
500
600
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Figure 2. (a)An isobutane chemical ionizatin/fast-atom bombardment (CI/FAB) mass spectrum of pentaerythritol tetrapentanoate. An en-
hancement of 1000-fold in the molecular ion (compared to the conventional FAB spectrum, Figure la) is observed due to the postionization of the abundant sputtered neutrals. (b) An isobutane CI/FAB mass spectrum of NRL-S-300 commercial base oil. A 500-fold enhancement of the protonated molecules is observed relative to the conventional FAB mass spectrum of NRL-S-300 (Figure lb). than molecular information (unless gas chromatography/mass spectrometry is used). A new desorption ionization method, called chemical ionization/fast-atom bombardment mass spectrometry (CI/ FABMS) (9, IO), also has been investigated in these studies on lubricant characterization. In the sputtering or desorption process of inorganic systems there are about 1000-fold more neutral species desorbed than ions desorbed (IO). This high neutral-to-ion yield apparently applies to organic species (IO). The CI/FABMS method postionizes the desorbed neutral species by gas-phase ion/molecule reactions such as proton and hydride transfer, charge-exchange, adduct ion formation, and collisional relaxation processes. Figure 2a is an isobutane chemical ionization/fast-atom bombardment (CI/FAB) mass spectrum of the model compound, PETP. This CI/FAB spectrum can be compared directly to the conventional FAB mass spectrum of PETP (shown in Figure la). The differences are dramatic (remembering that the conventional FAB spectrum, Figure l a , has been multiplied by 100). The protonated molecule [M H]+ is enhanced in abundance by almost 3 orders of magnitude. Also, the fragment ion abundances have decreased such that their relative abundances are less than that of the protonated molecule. Similar enhancements in ion abundances also have been observed with negative ions (IO). Figure 2b shows the CI/FAB mass spectrum of NRL-S-300 that can be compared directly with the conventional FAB mass spectrum (Figure l b ) of the base oil. An almost 500-fold enhancement of the ion abundances in the protonated molecular region is observed. This enhancement allows these protonated molecules to be used to determine quantitatively the isomeric composition of the sequence of homologues that make up the base stock. To perform this analysis, mass spectrometry/mass spectrometry (or tandem mass spectrom-
+
70
Figure 3. The mass-analyzed ion kinetic energy spectra (MIKES)of the unimolecular dissociation of protonated molecular ions (homologues: m l z 487, m l z 501, and m / z 515) produced by isobutane CI/FAB on NRL-S-300 base oil. The isomeric composition of each homologue can be determined from the ion abundances of the fragment ions, which represent the loss of one of the alkyl groups of the four esters moieties about the pentaerythritol nucleus. (The peak heights in these stick spectra are proportional to the area of the corresponding MIKES peaks.)
Table 11. Isomer Composition of the Tetraester Homologues in NRL-S-300 homologue
isomer(s)"
% measured compositionb
% predicted composition'
100 100
100 100
84
84
16 53
16 55
34
38 7
13
48 16 29
I 1
53 9 31 6 1
"Each of the four numbers in the series specifies the number of carbon atoms in the four acyl components, (CnH2n+10),about the pentaerythritol nucleus. The measured isomer compositions were calculated by an algebraic analysis of the measured acid abundances in the CI/FAB tandem mass spectrometry spectrum obtained from each protonated parent molecule. The predicted isomer values were calculated from the values of the acyl abundances (method C) given in Table I.
etry) (13)methods were used. Each of the various protonated molecules of the homologous series was mass selected in turn with the first sector of the mass spectrometer; then, the mass-selected ions unimolecularly fragmented between the two analyzers, and finally the fragments were energy analyzed with the second sector of the mass spectrometer. This technique is referred to as mass-analyzed ion kinetic energy spectrometry (MIKES) (14). The distribution of the [MH - RCOOH]+ fragment ions (Figure 3) was related to the isomeric composition of the mass-selected protonated molecule (assuming equivalent rates of unimolecular dissociation).
ANALYTICAL CHEMISTRY, VOL. 58, NO. 12, OCTOBER 1986
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73
O
rn/z
Flgure 4. A FAB mass spectrum of NRL-LQ, miniature bearing oil. Ions corresponding to the three components of the lubricant, (a) the base oil ( E T P ) , (b) antioxidant (octyCPANA), and (c) metal passivator (benzotriazole), are observed.
Table I1 gives the results of the isomeric analysis, and it should be referred to in the following discussion. The numbers given for the isomer compositions in Table I1 represent acyl component carbon chain length of each of the four acid moieties about the pentaerythritol nucleus. The protonated molecules observed at m / z 473 and mlz 487 can only result from one possible isomer. In the case of the protonated molecule at m / t 501, there are two different isomers as given in the table that can yield the 501 molecular weight, for the species at mlz 515 three isomers are possible, and for the mlz 529 species there are five possible isomers. In this example, these isomeric compositions also could have been calculated based on the acyl component analysis given in Table I, unless the base oil was a blend of two or more base oils. The good agreement shown in Table I1 between the measured and predicted compositions illustrates the potential of the method for determining the isomeric compositions not only of a homologous base-oil mixture but also in blends of base oils where acyl component profiles cannot be used to calculate the isomer compositions. Computer reference FABMS spectra can be used to determine the base-oil composition of lubricants. A FAB spectrum of NRL MB-SOB instrument ball-bearing lubricant (15) compared very well to a computer-generated composite FAB mass spectrum synthesized from two different base-oil reference spectra. The composite was composed of the NRL-S-300 spectrum attenuated 33% and the FAB spectrum of dioctyl azelate attenuated 66%. The actual composition was 34.5% NRL-S-300 and 63.3% dioctyl azelate. Additives. Another consideration in lubricant analysis is the determination of low levels of additives and/or their fate (e.g., degradation or reaction products) in the lubricant. Some additives are carcinogenic and highly toxic while others may have deleterious effects in certain applications; therefore, it is useful and it may be required for occupational safety to have fast, simple, semiquantitative methods to screen directly for additives. Figure 4 shows the FAB mass spectrum of another miniature bearing oil, NRL-LQ. This synthetic lubricant is composed of 98.8% base oil, pentaerythritol tetrahexanoate (PETH), 1.0% antioxidant, N-(1,1,3,3-tetramethylbutyl)phenyl-1-aminonaphthalene (octyl-PANA),and 0.2% metal passivator, benzotriazole. Ions that are characteristic of the lubricant composition are observed in the spectrum. In addition to those ions indicative of the base oil PETP, ions representative of the additives were observed. The M+ ( m / z 331) and [M + H]+ species for the octyl-PANA are observed including a characteristic fragment a t m / z 260 [M - CH&(CH,),]+. The protonated molecule of benzotriazole ( m / z 120) is also observed. Silicone compounds are used as high-temperature lubricants and in low levels as antifoam additives. In certain applications
200
100
300
400
500
m/z
Figure 5. A FAB mass spectrum of a commercial silicone based lubricant, which consists of linear and cyclic poly(dimethylsi1oxanes). Ion peaks indicative of the various series are observed. The trimethylsilyl ion (m/ z 73),characteristic of linear polysiloxanes, is the most abundant ion in the mass spectrum. (D is -(CH,),SiO-, the repeating dimethylsiloxane polymeric unit, and M is -(CH,),SiO-, the trimethylsiloxane terminating unit, where one of the two M-terminating groups will not have an oxygen.)
[MtNa]'
w 0 z]
5[
595
9 I I
0
100
58 1
200
300
400
500
600
m/z
Figure 6. A FAB mass spectrum of the experimental base oil, pentaerythritol perdeuteriotetrahexanoate, havin a 2000 ppm concentration of sodium. An adduct ion [M f Na] resulting from the at-
9
tachment of the sodium ion to the base oil molecule is observed at m l z 595.
airborne silicones can have deleterious effects on electromechanical machinery. We have determined the presence of low levels ( - 5 parts per thousand) of poly(methylphenylsi1oxane) in NRL-S-300 base fluid using FABMS by monitoring the abundant methylsilyl ion ( m / z 73), which is characteristic of linear polysiloxanes. Also, FABMS can be used to characterize the composition of silicone fluids similar to that demonstrated for the pentaerythritol tetraesters. Figure 5 shows a FAB mass spectrum of a commercial silicone oil lubricant, which is composed of a series of linear and cyclic polydimethylsiloxanes. This spectrum is similar to E1 mass spectra of silicones. These examples show the potential of the technique for the direct and rapid screening of additives in lubricants. To use this FABMS technique for quantitative analysis of additives, the addition of known quantities of isotopically labeled additives as internal standards would be the preferred method. Figure 6 shows a FAB mass spectrum of a deuterated base stock, pentaerythritol perdeuteriotetrahexanoate (PEdTH), which is inder investigation in our laboratory as an oxidatively stable base oil ( I ) . This particular base stock was found to have a high concentration (2000 ppm) of sodium (determined by flame emission spectroscopy) resulting from its chemical synthesis. The FAB mass spectrum shows a large peak at m / t 23 due to the ubiquitous sodium ion, but more important an adduct ion corresponding to the attachment of sodium to the PEdTH molecule is observed a t m / z 595, [M+ Na]+. This species is not observed in low-sodium content PEdTH base oils. This result may indicate a base stock/alkali metal interaction. The FAB method may offer considerable potential for the study of additive/base stock and additiveladditive
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ANALYTICAL CHEMISTRY, VOL. 58, NO. 12, OCTOBER 1986
interactions, for example, the alkali metal effect (1,2).
CONCLUSIONS The fast-atom bombardment technique has been shown to be a rapid, direct, and semiquantitative method for determining the composition of base oils and lubricants and for the direct screening of additives. The technique of chemical ionization/fast-atom bombardment mass spectrometry, which enhances dramatically molecular ion abundances, allows the isomeric compositions of base oils (and blends) to be determined readily in conjunction with tandem mass spectrometry techniques. While this study focused on synthetic lubricants, the method should be applicable to more complex systems. This FAB mass spectrometry method also is being used in our laboratory for the direct analysis of degradation products in lubricants. The use of computer-based reference spectra from this method was discussed, and such as computer-based system could be automated and extend the application of the method. It could be an especially powerful technique for lubricant characterization if combined with a complementary technique and corresponding reference data base such as Fourier transform infrared spectroscopy. The FAB technique has immediate application to lubrication science and technology in the areas of fundamental lubrication chemistry, quality control, trend analysis, and failure analysis. For example, study of gas-phase ion/molecule reactions using the CI/FAB method is a simple experimental method to investigate oxidative degradation mechanisms, and such studies may have relevance to lubricant solution chemistry. Also, the characterization of polar degradation products from an oxidized lubricant sample is readily amenable to FAB analysis because of the increased sensitivity of the method to charged or polar species (16). We have also used FABMS in a study related to a biosynthetic approach to deuterated lubricants (17). In that study, we found that algae (deuterated and undeuterated) could be bombarded directly to obtain semiquantitative data on the distribution of fatty acids in the complex lipids of the algae (18).
ACKNOWLEDGMENT The authors thank Mark M. Ross (NRL) and James A. Yergey (NIH) for performing the liquid chromatography/mass spectrometry analysis, Mark Ross for performing the gas chromatographic analysis, John W. Mintmire (NRL) for his computer computations of isomer compositions, and Robert
N. Bolster (NRL) for helpful discussions on lubricants. Mgistry No. PETP, 15834-04-5; PETH, 7445-47-8; octylPANA, 103693-92-1;benzotriazole, 95-14-7; pnetaerythritol tripentanoate, 70146-32-6.
LITERATURE CITED Campana, J. E. High-Temperature Deuterated Lubricants: Additives, Mechanisms and Methods ; US. Naval Research Laboratory: Washington, DC 1983; NRL Report 8779. Chao, T. S.; Kjonaas, M. Proceedings of the Symposium on Synthetic and Petroleum-Based Lubricants, Division of Petroleum Chemistry of the American Chemical Society, Las Vegas, NV, March 1982; pp 362-379. Barber, M.; Bordoli, R. S.; Elliott, G. J.; Sedgwick, R . D.; Tyler, A. N. Anal. Chem. 1982, 5 4 , 645A-657A. Kuriansik, L.; Williams, T. J.; Campana, J. E.; Green, B. N.; Anderson, L. W.; Strong, J. M. Biochem. Biophys. Res. Commun. 1983, 478-483. Caprioii, R. M. AnaiChem. 1983, 5 5 , 2387-2391. Busch, K. L.; Cooks, R. G. Science 1982, 2 1 8 , 247-254. Morgan, R. P.; Beynon, J. H.; Bateman, R. H.; Green, B. N. Int. J . Mess Spectrom. Ion Phys. 1979* 28, 171-191. Franks, J. Int. J . Mass Spectrom. Ion Phys. 1983, 4 6 , 343-346. Campana, J. E.; Freas, R. B. J . Chem. SOC.,Chem. Commun. 1984, 1414- 14 15. Freas, R. B.; Ross, M. M.; Campana, J. E. J . Am. Chem. SOC. 1985. 107, 6195-6201. Klamann, D. Lubricants and Related Products; Verlag Chemie: Weinheim, FRG, 1984; p 132. O'Rear, J. G.; Sniegoski, P. Analysis for Acyl Components of Neopentyi Polyol Ester Lubricants ; U.S. Naval Research Laboratory: Washington, DC, 1966; NRL Report 6338. Tandem Mass Spectrometry; McLafferty, F. W., Ed.; Wiiey-lnterscience: New York, 1983. Beynon, J. H.; Cooks, R. G.; Amy, J. W.; Baitinger, W. E.; Ridley, T. W. Anal. Chem. 1973, 4 5 , 1023A-1031A. Blachiy, C. H.; FitzSimmons, V. G.; Ravner, H. NRL-MB-208, An I m proved Instrument Ball Bearing Lubricant; US. Naval Research Laboratory: Washington, DC, 1970; NRL Report 7087. Williams, D. H.; Bradley, C.; Bojesen, G.; Santikorn, S.; Taylor, L. C. E. J . Am. Chem. SOC. 1981, 103, 5704-5706. Ross, M. M.; Neihof, R. A.; Campana, J. E. Biodeuterated Materials: Hlgh Temperature Lubricants from Aigae ; US. Naval Research Laboratory: Washington, DC, 1986; NRL Report 8952. Ross, M. M.; Neihof, R. A.; Campana, J. E. Anal. Chim. Acta 1988, 181, 149-157.
RECEIVED for review September 26, 1985. Resubmitted May 27, 1986. Accepted May 27, 1986. The National Research Council is acknowledged for its support of R. B. Freas as a National Research Council Research Associate. A portion of this work was presented at the 40th Annual Meeting of the American Society of Lubrication Engineers, Las Vegas, NV, May 1985. This work was supported financially through the Office of Naval Research, the Naval Sea Systems Command, and the Naval Air Systems command.
