Fluorescence detector for analysis of polynuclear arenes by gas chromatography

Abstract

A gas phase fluorescence detector has been developed for the analysis of mixtures of polynuclear arenes by gas chromatography. In general, gas phase measurements are more convenient to make and less susceptible to light scattering by the solvent than liquid phase measurements but fluorescence intensity is lower. Sensitivity might be enhanced through use of an ellipsoidal condensing mirror and removal of the carrier gas by a molecular separator before the sample enters the fluorometer cell. Measurement of fluorescence is more sensitive and specific than electron capture detection, and, in addition, permits the analysis of mixtures of compounds which cannot be separated on present chromatographic columns.MANY POLYNUCLEAR ARENES are present in the combustion products of fossil fuels, tobacco smoke, and smoked foods: some of these are known to be carcinogenic. Gas chromatography has great potential for analyzing complex mixtures of these compounds which has never been fully realized. This is in part due t o the fact that the electron capture detector (ECD), which has been used most frequently for the analysis of these compounds, is nonspecific and is not amenable t o temperature programming because of column bleed. Also, a number of refractive pairs of polynuclear arenes exist which cannot be resolved on any known column packing. By using a liquid phase fluorometer ( I ) or a gas phase fluorometer as chromatographic detectors, it is possible to overcome many of these difficulties. This paper describes the basic principles of operation of a gas phase fluorescence detector and its potential for the analysis of polynuclear arenes. EXPERIMENTALGas Chromatography. A Micro-Tek Model MT-160 gas chromatograph (Tracor, Inc., Austin, Texas), equipped with a 13.5 mC 03Ni electron capture detector was connected in series to a n Aminco-Bowman spectrophotofluorometer (American Instrument Company, Silver Spring, Md.) as shown in Figure 1. Polynuclear arenes were separated on the G L C column B a n d measured by the electron capture detector C. The column effluent then passed from the ECD through a heated transfer line into the microflow cell D where the compounds were measured by fluorometry. The signals from the ECD and the SPFD were recorded by the dual-pen recorder G.Glass columns (6-ft X l/a-in. i.d.) packed with 10% Dexsil 300 coated on 8OjlOO mesh Chromosorb W (Tek-Lab, Baton Rouge, La., Catalog No. 40009) were used for compound separation. Column temperatures were varied between 240 and 325 "C using the isothermal mode of operation. The injection port was maintained at 290 "C and the EC detector at 325 "C. The optimum carrier gas was N P at a flow rate of 90 ml!min. Electrometer sensitivity was in the range of 3.2 X 10-9 to 8.0 X 10-lo AFS.Spectrophotofluorometer. An Aminco-Bowman spectrophotofluorometer (SPF) equipped with a 150-watt, 7.5-A, 17-23 volt dc Hanovia 901C1 Xenon lamp, and IP21 photomultiplier tube was used. A 3-mm i.d. X 5 mm 0.d. X 20-(1) M. C. Bowman and M. Beroza, ANAL. CHEM., 40, 535 (1968). mm quartz flow-...

Instrumental effects on limits of detection in gas phase fluorescence detection of gas chromatographic effluents

“…It should be noted that the flow cell temperature in systems (iv) and (v) was lower than in systems (i), (ii), and (iii). However, while it has been shown that the sensitivity of gas phase fluorescence detection increases at lower temperatures (17). In our case, the temperature differential was not enough to make a substantial difference in the measured limits of detection.…”

“…Molecular fluorescence, as well as being a powerful analytical tool by itself, has become well-established as an ancillary technique to both liquid (1)(2)(3)(4)(5)(6)(7)(8)(9)(10) and thin layer (11)(12)(13)(14)(15) chromatography. There have also been several examples of molecular fluorescence being used to identify and quantify gas chromatographic eluents (16)(17)(18)(19)(20)(21).…”

Fluorometric analysis

“…Apparatus combining a gas chromatograph with a speetrofluorometer has been successfully applied (85, 138). A new scanner has been described for fluorometric quantitation of thin layer chromatograms (432).…”

“…Pulsed laser excitation was employed to study the fluorescence decay of pyrenebutyric acid attached to macromolecules (996). In the analysis of polynuclear arenes by gas chromatography, a fluorescence detector wras found useful (138). Studies have appeared on the luminescent spectra of the free radicals of methylnaphthalenes (576) and other arylmethyl radicals (514) produced by photolysis.…”

Fluorometric analysis

“…Even if the compounds in the effluent are not intrinsically fluorescent, it is still possible to use a fluorescence detector if (a) the compounds are oxidizable by Ce(IV) with the production of Ce(III) which is fluorescent (436,437), or (b) the compounds can be labeled with a fluorophore reagent such as 5-dimethylaminonaphthalene-l-sulfonyl (DAN-SYL) chloride (240). Similarly, in gas chromatography, fluorescent detectors for the effluent vapors provide higher sensitivity and specificity, as for polynuclear arenes, than other detectors (108,238,748). Refinements continue to be made in fluorometric quantitation of thin-layer chromatograms (TLC) (353); as an example, a tenfold greater sensitivity for the detection of pyrene was found on alumina TLC plates than on silica gel plates, which shows the importance of the adsorbent as well as of other experimental parameters (682).…”