Flame photometric detection of some transition metals. I. Calibrations and spectra

Abstract

129 (1992). After gas-chromatographic separation as volatile organometallics, some transition elements were found to respond with analytically relevant sensitivities in the flame photometric detector. Their minimum detectable amounts, in mole of metal per second at an S/N,.,., ratio of 2, were 1 x lo-'' for nickel and 6 x 10-l3 for rhenium, as well as a less sensitive 2 x lo-'' for molybdenum and 3 x lo-'' for cobalt. (When divided by 3.7, these values yield the S / u = 3 limit of detection as recommended by IUPAC.) Calibration curves were established for these elements in comparison with transition metals already known to respond in the flame photometric detector. Their chemiluminescent spectra, together with that of chromium, were measured in the detector at analytically (as opposed to spectroscopically) optimized conditions. Atomic lines, molecular bands, and continua were all present. Also, the spectra produced by several types of carbon compounds were recorded for a definition of potential spectral interferences from hydrocarbonaceous sample matrices. The atomic lines and the massive continua displayed by certain metals are discussed in some detail. Atomic lines appear up to a limiting energy level of 3.6 eV above ground state. It is suggested that continua could arise from small, perhaps catalytically active particles. Also discussed, in accordance with a reviewer's request, are the analytical performance of the FPD compared to ICP and MIP sources, and the definition and influence of noise on measured performance criteria.XUN-YUN S U N , BRIAN MILLIER et WALTER A. AUE. Can. J. Chem. 70, 1129 (1992) On a trouvC que certains dements de transition, sCpar6s par chromatographie gazeuse sous le forme d'organomCtalliques volatils, peuvent repondre avec des sensibilites analytiquement acceptables dans un dttecteur photometrique a flamme. Les quantitks minimales detectables, en mole de metal par seconde, a un rapport de S/N,.,., de 2, sont de 1 X 10-l4 pour le nickel et de 6 X lo-'' pour le rhenium alors que des sensibilites plus faibles de 2 X lo-" et 3 x lo-'' ont Ct C dCterminCes respectivement pour le molybdkne et le cobalt. (Lorsqu'on divise ces valeurs par 7 , on obtient la limite de detection S / u = 3 recommandee par I'UICPA.) On a Ctabli des courbes de calibration de ces elements et on les a compare avec celles de metaux de transitions d6ja connus pour donner une reponse dans le detecteur photometrique flamme. Optrant dans des conditions analytiquement (par opposition 2 spec~roscopiquement) optimisees, on a mesure leur spectre de chimiluminescence ainsi que celui du chrome dans le dktecteur. Des raies atomiques, des bandes molCculaires et des continua sont presents dans tous les cas. De plus, dans le but de dCfinir les interfkrences spectrales potentielles dues a des matrices d'Cchantillons contenant des hydrocarbures, on a aussi enregistre les spectres de plusieurs types de composCs carbones On discute en detail des raies atomiques et des continua importants observes avec certains mCtaux. Les raies ato...

Flame photometric detection of some transition metals. II. Enhancement of selectivity

“…In particular, the spectra of aromatics are more intense than those of aliphatics in the 480-660 nm region (2). This is chromatographically illustrated in Fig.…”

“…But it is also the one mode where selectivities are, in general, at their lowest. While transition metals are most often determined by those methodologies that employ high-energy, high-resolution atomic spectrometry, several elements have shown analytically useful responses in the low-energy, low-resolution FPD (2). And although the vast majority of the industrially, environmentally, and biochemically important transition metal compounds are not volatile enough to make it through a gas chromatograph, they can be processed by capillary liquid chromatography and (or) supercritical fluid chromatography, two techniques that make increasing use of typical GC detectors (including the FPD).…”

“…For some FPD-active transition elements, as well as for different types of carbon compounds, such spectra have recently been determined (2).…”

“…Second, it is well known that the FPD signal for carbon compounds depends to some degree on their structure: f o~ instance, aliphatics respond more weakly than aromatics. The spectral profiles, while similar in one wavelength region, differ strongly in another (2). Consequently, the choice of a carbon standard with which to match the two channels can be crucial.…”

“…J. Chem. 70, 1143(1992.On a utilisC un dCtecteur photometrique & flamme opCrant dans un mode a canal unique ou dans un mode diffkrentiel a double canal pour caractkriser et pour contrder sa sClectivitC vis-8-vis de divers ClCments de transition comportant un fond hydrocarbonC. Les expCriences comportaient des composCs du Cr, du Mn, du Fe, du Co, du Ni, du Ru, du Re et du 0 s pouvant &tre chromatographies en phase gazeuse.…”