Laser-excited fluorescence spectrometry of phosphorus monoxide and phosphorus in an electrothermal atomizer: determination of phosphorus in plant and biological reference materials and in nickel alloys
Laser-excited molecular fluorescence spectrometry with electrothermal vaporization of phosphorus monoxide (PO ETV-LEMOFS) and laser-excited atomic fluorescence spectrometry of phosphorus in an electrothermal atomizer (P ETA-LEAFS) were studied. Phosphorus monoxide and phosphorus were excited at 246.291 and 213.618 nm, and their fluorescence was detected at 324.5 and 253.5 nm, respectively. Excitation spectra of phosphorus monoxide both in an air–acetylene flame and a graphite furnace were obtained. Detection limits of phosphorus by PO ETV-LEMOFS and P ETA-LEAFS were found to be 80 and 8 pg, respectively. The linear dynamic range of the calibration graph for phosphorus by PO ETV-LEMOFS and P ETA-LEAFS extended over three orders of magnitude, from 80 pg to 0.2 µg, and four orders of magnitude, from 8 pg to 0.1 µg, respectively. For phosphorus monoxide, significant interferences were observed from cations, such as nickel and calcium. Phosphorus was determined in National Institute of Standards and Technology plant and biological Standard Reference Materials by PO ETV-LEMOFS and P ETA-LEAFS. Good agreement with certified values was obtained, with an analytical precision of between 5 and 18%. Phosphorus ETA-LEAFS was applied successfully to the determination of phosphorus in high temperature nickel alloys, in which the concentrations of phosphorus were below the detection capabilities of electrothermal atomic absorption spectrometry. For P ETA-LEAFS a background signal from nitrogen monoxide, caused by the presence of nitric acid during dissolution, could be eliminated by a char step at temperatures above 600 °C.