THE CETAC ADX-500 AUTODILUTER SYSTEM - A STUDY OF DILUTION PERFORMANCE WITH THE ELAN-6000 ICP-MS AND ELAN SOFTWARE

The CETAC ADX-500 autodiluter system was tested with ELAN(R) v 2.1 sof tware and the ELAN 6000 ICP-MS instrument to determine on-line automat ed dilution performance during analysis of standard solutions containi ng nine analytes representative of the mass spectral range (mass 9 to mass 238). Two or more dilution schemes were tested for each of 5 test tube designs. Dilution performance was determined by comparison of an alyte concentration means of diluted and non-diluted standards. Accura te dilutions resulted with one syringe pump addition of diluent in sma ll diameter round-bottomed (13 mm OD) or conical-tipped (18 mm OD) tub es and one or more syringe pump additions in large diameter (28 mm OD) conical-tipped tubes. Inadequate dilution mixing which produced high analyte concentration means was observed for all dilutions conducted i n flat-bottomed tubes, and for dilutions requiring multiple syringe ad ditions of diluent in smalt diameter round-bottomed and conical tipped tubes. Effective mixing of diluted solutions was found to depend larg ely upon tube diameter and liquid depth: smaller tube diameters and gr eater Liquid depth resulted in ineffective mixing, whereas greater tub e diameter and shallower liquid depth facilitated effective mixing. Tw o design changes for the autodiluter were suggested that would allow e ffective mixing to occur using any dilution scheme and tube design.