Optical enhancements and applications of rapid atomic emission spectrometry acousto-optic deflector background correction

A glass acousto-optic deflector (AOD) is mounted in a 0.5 m spectrometer fo r atomic emission background correction. The system allows sequential and r apid observation of adjacent wavelengths for "on" and ''of" atomic line bac kground correction. Particular attention is directed to optical masking and data acquisition. While AOD components slightly degrade spectroscopic reso lution, proper optical masking minimizes this problem and enhances AOD diff raction efficiency. Conversely, reduction of light throughput by masking fo rces a compromise in minimal useful aperture diameters. Representative atom ic spectra with a neon hollow cathode lamp are presented. Utilizing appropr iate AOD masking arrangements produced an increase in observed neon line wi dths to 0.14 nm from the 0.09 nm widths observed in the absence of the AOD. While the acousto-optic has the capability to alternate observed wavelengt hs in the 100 kHz range, the 3000 Hz upper frequency limit is a function of the current computer manipulation software. The best signal-to-noise ratio s were obtained at higher sampling rates. Background correction was perform ed with a microwave-induced plasma atomic emission source. Spectral charact erizations were obtained with the 425 nm scandium emission line, the sodium doublet near 589 nm and the chromium triplet in the 427 nm region. Calibra tion plots were obtained with solution nebulization and electrothermal vapo rization. Time-detector response profiles are illustrated for electrotherma lly vaporized analytes.