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(2) J. C. Arcos and M. F. Argus, “Chemical Induction of Cancer", Vol. II A, Academic Press, New York, NY, 1974, p 386. (3) "The Health Consequences of Smoking", January 1973, DHEW Publication No. (HSM) 73-8704. (4) P. S. Larson and H. Silvette, "Tobacco—Experimental and Clinical Studies", Supplement II, The Williams and Wilkins Co., Baltimore, MD, 1972. (5) “The Health Consequences of Smoking, A Report to the Surgeon General: 1971", DHEW Publication No. (HSM) 71-7513. (6) R. L. Stedman, Chem. Rev., 68, 153 (1968). (7) A. P. Swain, J. E. Cooper, R. L. Stedman, and F. G. Bock, Beitr. Tabakforsch., 5, 97 (1969). (8) F. G. Bock. A. P. Swain, and R. L. Stedman, J. Nat. Cancer Inst., 44, 1305 (1970). (9) D. Hoffman and E. L. Wynder, Cancer, 27, 848 (1971). R. L. Miller, W. J. Chamberlain, and R. L. Stedman, Tob. Sci., 13, 21 (10)

(12) R. L. Stedman, R. L. Miller, L. Lakritz, and W. J. Chamberlain, Chem. Ind. (London), 394 (1968). (13) B. L. Van Duuren, J. Nat. Cancer Inst., 21, 1 (1958). (14) D. Hoffmann and E. L. Wynder, Cancer, 27, 848 (1971). (15) H. J. Kllmlsch and L. Stadler, J. Chromatogr., 67, 175 (1972). (16) H. J. Kllmlsch, Fresenlus Z. Anal. Chem., 264, 275 (1973). (17) W. O. Atkinson, "Production of Sample Cigarettes for Tobacco and Health Research", Unlv. of Kentucky Tobacco and Health Conference— 1970, Lexington, KY. (18) K. Rothwell, Ed., "Standard Methods for the Analysis of Tobacco Smoke", Research Paper II, Tobacco Research Council, Lodon, 1972. (19) H. C. Plllsbury, C. C. Bright, K. J. O'Connor, and F. W. Irish, J. Assoc. Off. Agrie. Chem., 52, 458 (1969). (20) A. P. Swain, J. E. Cooper, and R. L. Stedman, Cancer Res., 29, 579 (1969).

(1969). (11) E. L. Wynder and D. Hoffmann, "Tobacco and Tobacco Smoke: Studies in Experimental Carcinogenesis", Academic Press, New York and London, 1967, p 730.

Received for review December 20, 1974. Accepted February 7, 1975. Reference to a company or product name does not imply approval or recommendation by the USDA.

Quantitative Gas Chromatographic Determination of Ethanolamines as Trimethylsilyl Derivatives Ryszard Piekos, Krzysztof Kobylczyk, and Janusz Grzybowski Institute of Chemistry and Analytics, Faculty of Pharmacy, Medical Academy, 80-416 Gdansk, Poland

Individual components of ethanolamine mixtures, comprising mono-, di-, and triethanolamine are usually determined by chemical methods. The methods are said to be nonspecific and mostly inaccurate. Their brief characterization is to be found in the work of Brydia and Persinger

U).

Direct gas chromatographic determination of ethanolam-

ines is complicated by their low volatility owing to the strong hydrogen bonding character which causes tailing chroma(1). The best separation was achieved by vacuum tography with a copper tube, 0.5 m by 0.3 cm, packed with diatomaceous earth, grain size 0.25-0.5 mm, impregnated with 25% polyethylene glycol 6000, and operated at 195 °C with helium carrier gas flow rate of 18 ml/min (2). A more convenient procedure has been developed by Brydia and Persinger (1), who converted ethanolamines to their trifluoroacetyl derivatives and determined them by gas chromatography. This method turned out to be simple and rapid, and provided impurity information which was unobtainable from the chemical method. However, when an ethanolamine mixture contained water, trifluoroacetic acid was liberated which tailed badly. A slight tailing of the derivative peak was also observed with new columns, which disappeared after several analyses. These shortcomings have now been eliminated by con-

version of ethanolamine mixtures to their trimethylsilyl (TMS) derivatives prior to separation. The trimethylsilylation method has been used widely for the separation and gas chromatographic determination of compounds carrying -OH, -NH, -NH2, -COOH, and -SH groups (3-5). More recent works on related analyses are: that of Champion and Jones (6), concerning determination of other alkanolamines by gas chromatography of acetyl derivatives and that of Cancalon and Klingman (7) on the determination of ethanolamine and other hydroxy amines as trifluoroacetyl and trifluoroacetyl/trimethylsilyl derivatives.

EXPERIMENTAL Apparatus. A Pye 104 gas chromatograph equipped with a flame ionization detector was used. The chromatograms were recorded on a Philips PM 8010 chart recorder. Chromatographic Columns. Glass columns were used (152.4 cm = 5 feet long X 0.4-cm i.d.) packed with 3% OV-1 coated on 100/120 mesh Diatomite CQ. The columns were preheated overnight at 240 °C with a carrier gas flow rate of 60 ml/min. Operating Parameters. The detector temperature was 210 °C, and the injection port was maintained at 190 °C. Argon and nitrogen were used as carrier gases at a flow rate of 19 ml/min. The chart speed was 1 cm/min. Injections were made with a 1 µ syringe, and injected volumes varied between 0.4 and 0.7 µ . The volumes were dependent on the magnitude of correction factors of the TMS derivatives considered. When the triethanolamine content of a mixture exceeded 90%, 0.7 µ was injected, since the TMS derivative of the amine has the greatest correction factor. In case of a high (>90%) monoethanolamine content, a 0.4-µ1 injection was satisfactory. For the remaining cases, intermediate volumes were employed. The column temperature was isothermal at 130 °C for 2 min and 15 sec, then programmed to 180 °C at 49°/min, and held at 180 °C until the analysis has been completed. An attenuation of the order of 5 X 104 resulted in a stable base line even with a fast rate of temperature increase employed. Peak area was calculated by multiplying the width of a peak at half-height by peak height at maximum. Chemicals. The trimethylsilylation agent, A,0-bis(trimethylsilyl)acetamide (BSA), was prepared according to the method of Klebe et al. (S), and had bp 71-73 “C/35 mm Hg. Monoethanolamine (>99%) was the product of Carlo Erba, Milan, Italy, and diand triethanolamine were pure commercial products manufactured by POCh, Gliwice, Poland. Procedure. About 0.02 ml of an ethanolamine mixture was added to a 2-ml stoppered test tube, followed by 1 ml of BSA. An exothermic reaction ensued. The content was then shaken for 1 min to obtain a homogeneous solution, and maintained in a water bath at 60 °C for 20-30 min, or for 2 hr at room temperature. The time was reduced by half with binary mixtures containing monoand triethanolamine, since each of them could be derivatized quantitatively much more readily than diethanolamine. Under the conditions indicated, complete trimethylsilylation of ethanolamANALYTICAL CHEMISTRY, VOL. 47, NO. 7, JUNE 1975

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Table I. Response Factors and Derivative Data for Components of Ethanolamine Mixtures Tris-TMS derivative

AbbreviaComponent

tion

Monoethanolamine Diethanolamine Triethanolamine

MEA DEA TEA

Bp/mm Hg Mol

20

*20 j 4

D

Relative

Approx.

response

retention

(7)

(7)

(7)

factor

time, min

80°/4 74°/2 119V2

1.4345 1.4290 1.4310

0.8551 0.8692 0.8945

0.22 0.63 1.00

1.95 5.42 8.20

Wt

277.64 321.69 365.74

n

Table II. Weight Per Cent Analyses of Trimethylsilyl Derivatives of Ethanolamines by Gas Chromatography Determined0

Added MEA

DEA

TEA

MEA

DEA

TEA

32.0 17.1

33.2 24.7 65.8 94.2

34.8 58.2 16.7 2.9 98.1 2.0 5.0 98.0 65.6 2.5

32.0 17.1 17.4 2.8

33.8 24.4 65.9 94.2

1.1

1.1

34.2 58.5 16.6 3.0 97.8

17.5 2.9 0.8

1.1

96.0 2.0 95.7 2.0 4.1 90.9 4.2 90.6 0 2.0 2.1 0 34.4 0 34.3 0 0 97.5 97.1 0 All results are averages of two determinations.

Figure 1. Chromatogram of trimethylsilyl derivatives of ethanolamines

ines occurred. One-half microliter samples were usually introduced into the gas chromatograph by means of a l-µ syringe.

RESULTS AND DISCUSSION Under the conditions employed, BSA reacts with the hydroxyl and the amino groups of the ethanolamines as shown in the following general equation: OSi(CH3)3 H2 N (C H2 C H2 OH )3_ „ +

3CH3C(:0)NHSi(CH3)3

3CH3C^ XNSi(CH3)3 +

—>-

[(CH3)3Si]X(CH2CH2OSi(CH3)3]3.„ (1)

where

=

0, 1, 2.

The products of these reactions were verified by preparation of the derivatives and comparison of their physicochemical characteristics with those reported in the literature (9). The side product of silylation, N-trimethylsilylacetamide (MSA), had retention time of ca. 1.5 min and eluted along with the excess of BSA. Reactions of the ethanolamines with BSA are quantitative under the conditions of the method. Derivative prepa1158

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ANALYTICAL CHEMISTRY, VOL. 47, NO. 7, JUNE 1975

2.3 5.2 97.9 65.7 2.9

ration is simple and rapid. Complete elution of all volatile derivatives requires less than ten minutes, and overall analysis time including calculations takes about one hr. In case of binary mixtures comprising mono- and triethanolamine, the time is reduced by half. Peak X in the chromatogram (see Figure 1) is due to incompletely silylated di- and/or triethanolamine in which only two hydroxyls have been silylated. Thus, it may be useful for monitoring the completeness of trimethylsilylation of the two amines. Figure 1 shows a chromatogram of an almost completely trimethylsilylated mixture which contained 4.2% of monoethanolamine (MEA), 90.6% of diethanolamine (DEA), and 5.2% of triethanolamine (TEA). For quantitative trimethylsilylation, a slight extension of the silylation time is required. Commercial ethanolamines contain low concentrations (<0.1%) of water which will react with BSA to form trimethylsilanol and MSA. Separate experiments showed that water up to a concentration as high as 5% did not interfere in determinations owing to a large excess of BSA employed. Table I lists the retention times and response factors for the individual ethanolamines, as well as physical constants of their trimethylsilylated derivatives. Table II shows the applicability of the procedure as a quantitative method for determining the individual components of the ethanolamine mixtures over the whole concentration range studied. The precision of the method was determined using a mixture comprising 5.2% MEA, 86.15% DEA, and 8.65% TEA of the highest purity available. These data were obtained from ten runs of three separate derivative preparations of the sample. The results showed an absolute standard deviation of 0.08, 0.12, and 0.11% for MEA, DEA, and TEA, respectively. The relative standard deviation was 1.6, 0.14, and 1.3%, respectively. LITERATURE

CITED

(1) L. E. Brydia and . E. Persinger, Anal. Chem., 39, 1318 (1967).

(2) P. F. Komissarov, L. V. Kondakova, and D. A. Vyakhirev, Gazov. Khromatogr., No. 4, 84 (1966). (3) A. E. Pierce, "Sllylatlon of Organic Compounds", Pierce Chemical Co.,

Rockford, IL, 1968. (4) Ch. A. Roth, Ind. Eng. Chem., Product Res. Develop., 11, 134 (1972). (5) V. Miller and V. Pacáková, Chem. Usty, 67, 1121 (1973). (6) . H. Champion and J.H. Jones, J. Assoc. Oft. Anal. Chem., 54, 1175 (1971).

(7) P. Cancalon and J. D. Kllngman, J. Chromatogr. Sci., 10, 253 (1972). (8) J. F. Klebe, H. Flnkbelner, and D. M. White, J. Am. Chem. Soc., 88, 3390

(1966). (9) E. Ya. Lukevlts, L.

I.

Libert, and M. G. Voronkov, Zh. Obshch. Khim., 38,

1838(1968).

Received for review October 10,1974. Accepted February 3,1975.

Analysis of Petroleum for Trace Metals: Loss of Mercury from Polyethylene Sample Vials in Neutron Activation Analysis J. O. Larson and E. V. Tandeskl Chevron Research Company, Richmond, CA 94802

'

A study of the stability of organomercury and arsenic compounds in petroleum stocks stored in a variety of containers was recently completed. The investigation was undertaken to find the best container for use in shipping samples around the country for the purpose of cross-checking analytical methods. Reactor neutron activation analysis was selected to monitor any metal losses because of the ease with which mercury and arsenic can be determined by this method. The experiments involved periodic removal of samples from the containers and transferring them to polyethylene containers for irradiation and subsequent counting. During this study, postirradiation losses of mercury, but not arsenic, from the irradiated polyethylene sample containers were observed. Other investigators have reported similar losses of mercury. Bate (1) found that polystyrene containers irradiated for prolonged periods (12-65 hours) at a neutron flux of 12 n cm-2 sec-1 showed a loss of mercury activity. He concluded that an unknown time dependent or time-temperature dependent transport mechanism was responsible. He also concluded that a group of samples and standards irradiated in individual plastic containers could become cross-contaminated and, therefore, recommended the use of quartz vials. Greenwood and Clarkson (2) observed losses of 203Hg stored at room temperature from 3-51 days in a variety of glass and plastic tubes. They suggested that mercury is lost by diffusion through the container walls or by volatilization to the upper part of the container, which effectively removes it from the gammaray detector surface. Kosta and Byrne (3), on the other hand, showed that, in sealed polystyrene containers, biological samples can be quantitatively assayed for mercury by irradiation. Weiss and Chew (4) recently reported observing substantial losses of induced activity from unacidified aqueous mercury solutions irradiated for 60 minutes in a TRIGA reactor. They proposed that the mercury is reduced to the metal and is lost through volatilization. In this note, we will show that postirradiation losses of mercury by diffusion may take place from heat-sealed polyethylene vials irradiated for only one hour at 3 X 1012 n cm-2 sec-1; that increasing neutron flux increases the postirradiation losses of mercury; that the solvent has an effect on the rate of loss; and that mercury diffuses through the container walls.

EXPERIMENTAL Diphenylmercury (Alpha Inorganics)

was

dissolved in

a

350-680

°F (40% aromatics) hydrotreated light cycle oil at a concentration of 100 ng/g. Containers made from five different materials were filled with this stock solution and sampled periodically. Approximately 1 ml was transferred to a %-dram tared conventional polyethylene vial (Olympic Plastics, Los Angeles, CA) and weighed. The vials were heat-sealed and reweighed. Aqueous inorganic mercury radiation standards containing 100 ng/g were prepared fresh prior to each irradiation from stock solutions of Harleco 1000 ¿ig/g mercury (as HgCh). The standard vials were prepared in the same as the sample vials. The final aqueous solution was apmanner proximately IN in nitric acid. Five samples (sometimes in duplicate) and two standards were irradiated for one hour at a flux of 3 X 1012 n cm-2 sec-1 at the Aerotest Operations’ AGNIR facilities (San Ramon, CA). Following the irradiations, the test sets were brought back to our laboratories for further processing. Blank vials were also irradiated in the same reactor position to determine if the irradiation facility was mercury contaminated, in which case the mercury may be sorbed on the surface of the vials and released later simulating postirradiation losses. No mercury was detected on the blank vials. After each irradiation, samples and standards were reweighed to determine if any evaporation loss had occurred in the reactor, which operates at a temperature of about 60 °C. No losses greater than 1 mg were ever observed. In most cases, a 30-minute gammaray spectrum was obtained using an ORTEC lithium-drifted germanium detector coupled to a Nuclear Data Model 2200, 1024 Channel Analyzer. An X-Y recording of the spectrum from 0-0.8 MeV was obtained as well as a digital printout of the analyzer contents in the region of interest. The isotope measured was 197Hg (half-life = 65 hours, peak energies = 0.078 MeV gamma and 0.069 MeV unresolved X-rays). Calculations were made by conventional peak integration and background subtraction. Corrections for decay and flux differences between samples and standards were made whenever necessary.

RESULTS AND DISCUSSION Because of the convenient half-life of 197Hg, no special attempts were made during the initial stages of this study to count the samples immediately upon arrival from the reactor facilities. They were stored at room temperature and processed whenever time and sample scheduling permitted. The first set of data obtained five days after irradiation in-

dicated that the mercury-hydrocarbon solutions irradiated and counted in the same vials had lost 50-60% of their 197Hg activity when compared to the aqueous mercury standards. The latter showed only the calculated decrease in activity due to decay. A second set of the same samples was irradiated and counted the same day; in this case, the mercury recovery was about 90%. Repeated experiments showed that if the samples were irradiated and counted within 4-8 hours, excellent recoveries of mercury were ob-

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