AUTOMATIC IMPLEMENTATION OF THE METHOD OF STANDARD ADDITIONS IN UNSEGMENTED FLOW SYSTEMS

An open/closed flow system allowing variable volumes of both sample an d standard calibration solution to be introduced was employed to perfo rm automatic calibration in unsegmented flow systems by using the meth od of standard additions. The dilution loop thus established was used to homogenize the sample and standard mixture in a constant final volu me that was subsequently introduced into the main flow system. The pro cedure allows direct analysis of liquid samples with no pretreatment a nd avoids matrix effects. Glucose and fructose were enzymatically dete rmined over the ranges of 0.01-0.1 g l(-1) and 0.02-0.1 g l(-1) with r elative standard deviation of +/-0.8% and +/-1.0% for the determinatio n of 0.05 g l(-1) (glucose) and 0.07 g l(-1) (fructose), respectively. Both analytes were determined in various types of drinks with average errors of 3.8% (glucose) and 4.6% (fructose).