Improved data-processing method for atomic absorption spectroscopy with electrothermal atomization.

A new approach is described for processing transient data from electrothermal atomizers used in atomic absorption spectroscopy. The transient responses are first integrated and then a pseudo-first-order model is fit to the time-dependent integrals in order to predict the response that would be measured if the atomization process were monitored to completion. The principal advantage expected and observed for the new approach is its ability to reduce effects of variables such as atomization temperature. For all elements studied (Cr, Mn, K, Yb, Fe), the new predictive approach is shown to be virtually independent of temperature in the range from 2200 to 2600 degrees C. The predictive approach exhibited lower temperature coefficients than either the peak-height or peak-area options for all elements examined. For the more volatile elements (Mn, K, Yb, Fe), the improvement ratio at 2400 degrees C of the predictive approach relative to the others ranged from 1.4 to 8.2. For chromium at 2400 degrees C, the temperature coefficient of the predictive method was approximately 10- and 30-fold lower than those for the peak-area and peak-height options, respectively.

Continuum-source atomic absorption spectroscopy with an echelle spectrometer adapted to a charge injection device.

An instrumental system for continuum-source atomic absorption spectroscopy has been developed for simultaneous multielement determinations. The system consists of an electrothermal atomizer and a charge injection device adapted to an echelle spectrometer to achieve multiplex detection. A continuous 40-nm spectral range in the two-dimensional echelle spectrum was acquired simultaneously through the capability of the charge injection device to integrate signals in its MOS capacitors. Novel methods were developed to compute absorbances by "scanning" through all orders in the entire echelle spectrum or selecting absorption lines randomly. In the range 300-430 nm, characteristic concentrations (1% absorption) were 1.6, 2.6, 2.9, and 3.8 ng mL-1 respectively for Cu, Mn, and two Cr lines; these values are similar to those (1.3, 2.2, 1.2, and 3.6 ng mL-1) obtained for single-element detection with an image-dissector system.

Multielement continuum-source atomic-absorption spectrometry with an echelle-spectrometer/image-dissector system.

The continued development of the echelle-spectrometer/image-dissector system for multielement determination by continuum-source atomic-absorption spectrometry is presented. Modifications of the instruments include the use of a 20-groove/mm echelle grating blazed at 76 degrees , and the removal of the magnetic shield from the image dissector. The spectral range is from 300 to 430 nm and the observed resolution is better than 0.005 nm at 400 nm. Calibration curves are linear up to an absorbance of 0.2, and absorption sensitivities are up to 4-fold better than with the previous design. Fundamental characteristics of the detector limit the application of the instrument to sequential single-element quantifications with the electrothermal atomizer, and to sequential multielement quantification with the flame atomizer. The further development of the instrument for simultaneous multielement qualification is discussed.

Advantages of an off-Littrow mounting of an echelle grating.

A phenomenon is described in which the size of the exit-slit image of the entrance slit is influenced by the angle at which an echelle grating is used. The phenomenon becomes significant only for large deviations from Littrow conditions. A mathematical treatment and experimental results are presented to show that proper exploitation of the effect results in simultaneous improvements in bandpass, range, and intensity for an echelle spectrometer.