GRAND-MP - Microwave plasma-atomic emission spectrometer

Abstract

Methods of atomic absorption analysis with electrothermal and (or) flame atomizers and inductively coupled argon plasma are widely used for elemental analysis of solutions. Despite the wide popularity of these analysis methods, in analytical laboratories there is a demand for spectrometers with new excitation sources as an addition or replacement to the existing set of instruments that could provide improved analytical performance, reliability, ease of operation on new equipment, and a reduction of analysis cost. The Agilent company made an attempt to develop such an instrument by launching the first production model of a microwave plasma spectrometer. However, a number of design features did not allow the use of the spectrometer to solve many analytical problems. We have summarized the principles of developing atmospheric pressure microwave nitrogen plasma of “optimal” shape for efficient heating, evaporation, atomization, and ionization of liquid samples and have developed a high-order-mode microwave cavity based on a commercial 2.45 GHz magnetron. A Grand-2 spectrometer with two hybrid assemblies of BLPP-2000 photodetector arrays is used to obtain and record spectra. The spectrometer allows simultaneous recording of spectra in the range 190-780 nm with an integration time of 2 ms. The analytical characteristics of a Grand-MP spectrometer are as follows: the linearity range of the calibration curve is 5 orders, with possible expansion to 7 orders of magnitude when using a lower intensity line, which is similar to the range of inductively coupled plasma spectrometers and far exceeds the ranges of flame atomic absorption spectrometry with 2-3 orders and Agilent MP 4210 with 4 orders; the long-term stability of the analytical signal measured for 6 hours without using the internal standard is no more than 2% relative standard deviation; The obtained detection limits are not inferior to those for Agilent MP-AES 4100, 4200, and 4210 microwave plasma spectrometers and modern flame atomic absorption spectrometers and are very close to those for radial view inductively coupled plasma spectrometers.