Low-temperature fluorescence spectrometric determination of polycyclic aromatic hydrocarbons by matrix isolation

Abstract

The performance of quantitative low-temperature fluorometry by the technique of matrix Isolation Is reported. Matrix-isolated samples of polycyclic aromatic hydrocarbons (PAH) are prepared by mixing the PAH vapors effusing from a Knudsen cell with a large excess of nitrogen gas; the gaseous mixture Is then deposited onto an optical window at ~15 K. Detection limits for PAH in nitrogen matrices are on the order of 11 g. Quantitative working curves for PAH are linear over five decades or more in concentration. Linear working curves can readily be obtained for Individual PAH In mixtures of Isomeric compounds. The use of matrix-isolation fluorometry for identification and quantitation of PAH in complex samples derived from coal liquids Is demonstrated.

Laser-excited Shpol'skii spectroscopy for the selective excitation and determination of polynuclear aromatic hydrocarbons

“…In multiccmponent sanples, overlaps of absorption bands might necessitate use of another excitation wavelength for a particular conpound. Despite the numerous linear analytical curves that have been demonstrated, the potential analytical utility of the Shpol'skii effect for quantitation of trace levels of PAH connpounds have been questioned (71,74,96). These questioning assertions were based on classical Shpol'skii effect studies on the luminescence spectrum dependency on concentrations (49,57,60).…”

Fluorescence line narrowing spectrometry of polycyclic aromatic hydrocarbons in organic glasses

“…The same paper reports qualitative identification of three major constituents in a natural PAH fraction via this method (27). As would be expected, vide supra, improvements in selectivity are also gained by utilizing both temporal resolution (29) and selective excitation into the narrowed absorption bands (14,28). Another advantage is that once the sample is in the matrix, sensitivities of about one part in lo"'"' and a five order of magnitude linear working range can be achieved (28), cf., attribute ii.…”

“…As would be expected, vide supra, improvements in selectivity are also gained by utilizing both temporal resolution (29) and selective excitation into the narrowed absorption bands (14,28). Another advantage is that once the sample is in the matrix, sensitivities of about one part in lo"'"' and a five order of magnitude linear working range can be achieved (28), cf., attribute ii. Also, luminescence in the matrix is nondestructive with the accompanying advantages described in attribute v.…”

“…This and the still broad bands result in many interferences in any complex mixture (26 (27)(28)(29). In other types of matrices, these same vibronic transitions can be considerably sharper, vide infra (31).…”

“…Thus, the requirement listed as attribute i is not met. Quantitation schemes utilizing internal standards are necessary (28) to compensate for irreproducible deposition of sample components, cf., attribute iii.…”