CALIBRATION IN FLAME ATOMIC-ABSORPTION SPECTROMETRY USING A SINGLE STANDARD AND A GRADIENT TECHNIQUE

To obtain calibration graphs, a standard solution of the analyte was p umped using an increasing flow rate while pure water was aspirated, fo r compensation, through a T-piece. In this way an on-line concentratio n gradient was obtained and a constant flow was supplied to the nebuli zer. The absorbance was monitored via a computer which facilitated dat a 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 b y means of the separate measurement of several standard solutions. A c alibration graph could be obtained in only 50 s with errors of less th an +/-3%. The mode of operation also permits the on-line dilution of m oderately concentrated solutions, which cannot be measured by direct a spiration and simplifies the standard additions method.