Calibration in flame atomic absorption spectrometry using a single standard and a gradient technique

Abstract

To obtain calibration graphs, a standard solution of the analyte was pumped using an increasing flow rate while pure water was aspirated, for compensation, through a T-piece. In this way an on-line concentration gradient was obtained and a constant flow was supplied to the nebulizer. The absorbance was monitored via a computer which facilitated data acquisition and handling. In spite of the problems posed at low flow rates by the pulsations caused by the rollers of the peristaltic pump, this calibration strategy gave graphs comparable to those obtained by means of the separate measurement of several standard solutions. A calibration graph could be obtained in only 50 s with errors of less than ±3%. The mode of operation also permits the on-line dilution of moderately concentrated solutions, which cannot be measured by direct aspiration, and simplifies the standard additions method.