single band with a maximum at 545 nm is observed with no evidence for a 645 nm peak. There is, in addition, an illdefined shoulder in the 385 to 430 nm region. As sodium 1,2-naphthoquinone-4-sulfonate in 14 M H&304in the absence of titanium shows a peak at 390, this shoulder could possibly indicate that the complexation reaction is not quite complete under these conditions. This complex is violet-blue in color. In contrast to the previous two compounds, the peak maximum at 545 nm does not change drastically at high acid strengths (13 to 15 M). Decomposition sets in above 15 M H2S04. As the effect of Ti(1V) and Ti(II1) concentrations was the same as that found for the previous two compounds, except that the absorbance was measured at 545 nm, the experimental conditions for the analysis of sodium 1,2-naphthoquinone4-sulfonate were identical as described above. A calibration curve for this compound from 7.7 X to 4.6 X was linear with a correlation coefficient of 0.999987 ( E = 4~4350) and, for the range 1.9 X to 2.3 X M, the correlation coefficient was 0.99994 (e = *4350). 2-Methyl-3-phytyl-1,4-naphthoquinone (Vitamin Kl). This molecule is different from the others because of the long side chain in the 3-position which perturbs complex formation. The spectrum (Figure 1,curve D) shows a single absorbance band with a rounded maximum between 640 and 655 mn. The two peaks at 510 and 390 nm have disappeared and the color of the complex is different. It is blue and corresponds to a single type of complex. The time needed to form the complex, 45 min, is longer, presumably because of steric hindrance. A calibration curve for this compound from 8.9 X lo4 to 8.9 X M was linear with a correlation coefficient of 0.99999 (e = *5730). Nature of the Complexes Formed. The structural nature of the complexes formed between titanium(1V) and these naphthoquinones is unknown although there is some indirect evidence that the less sterically hindered species, i.e., 1,4naphthoquinone, forms dimeric while the more sterically hindered 2-methyl-3-phytyl- 1,4-naphthoquinone forms monomeric complexes. Menadione forms a complex which appears to be in equilibrium with its dimeric form. Evidence for these speculations is as follows: (i) All complexes were found to have 1:l stoichiometry (determined by Job curves).
(ii) The absorption spectrum of the menadione complex as a function of acidity indicates the presence of two species in equilibrium (monomer/dimer) as is evidenced by the isosbestic point at 530 nm. Further, lower HzS04 concentrations favor the species absorbing at 510 nm (dimer). (iii) The menadione complex shows a shift in the absorption spectrum as a function of time; the 510 peak increases (dimer) while the 645 nm peak decreases (monomer). (iv) The complex formed with the sterically hindered 2-methyl-3-phytyl-l,4-naphthoquinone exhibits a single peak a t 645 nm (monomer favored) while (v) the complex formed with 1,4-naphthoquinone exhibits one peak at 510 nm (dimer favored). It has been assumed that the presence of an aliphatic side chain (i.e., methyl, phytyl) alters the absorption spectra of these complexes through steric effects exclusively. Presumably all of these complexes are bound through Ti-042 bonds which are well documented. The concentration of H#04 determines the form of the Ti(1V) species which in turn affects the absorption spectrum of the complex (cf. Figure 3). If the concentration of HzS04 is too low, Ti(1V) hydrolyzes and complex formation with most naphthoquinones does not occur. The spectrum of the complex formed with sodium 1,2naphthoquinone-4-sulfonate is difficult to explain on the basis of these arguments because this ligand is quite different from the others studied.
LITERATURE CITED (1) E. E. Van Koetsveld, Red. Trav. Chim Pays-Bas, 69, 1217 (1950). (2) H. Wachsrnuth and R. Denissen, J. Pharm. Belg., 42, 173 (1960). (3) S. S. M. Hassan, M. M. Abd Ei Fatteh, and M. T. M. Zakl, Fresenius’ 2. Anal Chem., 275, 115 (1975). (4) I. M. Kolthoff and P. J. Eiving, “Treatise on Analytical Chemistry”, Part 11, Vol. 5, Interscience, New York, N.Y., 1961 p 1. (5) T. C . J. Ovenston, C. A. Parker, and C. G. Hatchard, Anal. Chim. Acta, 6, 7 (1952). (6) J. H. Yoe and A. R. Arrnstrong, Anal. Chem., 19, 100 (1947). (7) J. V. Griel and R. J. Robinson, Anal. Chem., 23, 1871 (1951). (8) P. Arthur and J. F. Donahue, Anal. Chem., 24, 1612 (1952).
RECEIVED for review March 10,1977. Accepted May 12,1977. Thanks are expressed to the Fonds National de la Recherche Scientifique (F.N.R.S. Belgium) and the National Science Foundation (Grant No. CHE76-04321) for support of this research.
Fourier Transform Infrared Spectrometric Determination of Gaseous Performic Acid P. D. Maker, Hiromi Nlki,” C. M. Savage, and L. P. Breitenbach Research Staff, Ford Motor Company, Dearborn, Michigan 48 12 1
Gaseous performic acid in the concentration range 0.01 to 1.0 Torr was analyzed using a Fourler infrared spectrometer system. Sample stabillty problems were overcome by the fast data acquisltion speed and high sensitlvity of the system. Sample purity problems were circumvented by taking full advantage of the system’s hlgh resolution and spectral subtraction Capabilities.
Definitive identification of performic acid (HC(=O)OOH) as a reaction product in the photo-oxidation of hydrocarbons 1346
ANALYTICAL CHEMISTRY, VOL. 49, NO. 9, AUGUST 1977
is crucial for the understanding of atmospheric chemistry ( I ) . However, because of gas handling problems, no reliable analytical technique has been available. According to Giguere and Almos (Z),gaseous performic acid decomposes spontaneously to formic acid even at 0 “C and is highly explosive in concentrated form. Nevertheless, they succeeded in recording its IR spectrum but with unknown sample pressure. Unfortunately, its major absorption bands are not readily distinguishable under low resolution from those of formic acid. The work reported here demonstrates that the IR Fourier spectroscopic method can overcome these difficulties. By combining the following essential capabilities, it becomes a
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spectra of formic acid monomer (0.2 Torr) and dimer (0.05 Torr) and performic acid (0.6 Torr) in the frequency region of 600 to 3600 cm- . Absorption path length, 1 m. Av = ' / l e cm-'. Samples were pressurized with 700 Torr air Figure 1. IR
uniquely suited analytical tool. Fast data acquisition speed minimizes sample degradation. High detection sensitivity enables trace analysis of hazardous samples and ensures gas handling safety. High spectral resolution and frequency calibration facilitate compound identification. Computeraided spectral analysis used to remove spectra of known compounds from a composite spectrum enables the use of samples containing known impurities. The technique has been applied successfully to the determination of unstable compounds of atmospheric importance, such as pernitric acid and organic ozonides (3, 4).
EXPERIMENTAL The Fourier-transform IR facility consisted of a rapid scan, high resolution EOCOM Model 7001 interferometer,a PDP 11/40 on-line computer and in-house software ( 5 ) . The interferometer was equipped with a liquid Nzcooled HgCdTl detector and was capable of monitoring IR signals in the 600-4000 cm-' range with Au i '/32 cm-' and scanning speed
