Reconsideration of the Criteria to Determine Practical Fluctuational Concentration Limits in Atomic-Absorption Flame Photometry

Abstract

A study is presented on the influence of the instrumental time constant value in the determination of fluctuational sensitivity in atomic-absorption flame photometry. Fluctuational concentration limit (detection limit) has been defined as a function of the noise level of the blank reading (blank adjusted at the 0% absorption level), while the signal noise is a direct function of the time constant of the readout system employed. Employing a Beckman 979 atomic-absorption system and recorder, a scale expander unit was modified to provide a time constant control. The behavior of several elements is presented as an example of the dependence of the fluctuational concentration limit on the system time constant. These results, clearly indicating a basic relationship, lead to the establishment and presentation of a new criterion in an attempt to define and to compare concentration limits of a fluctuational nature.