An improved sampling approach in multi-pumping flow systems applied to the spectrophotometric determination of glucose and fructose in syrups Original Research Article

A novel sampling approach in flow analysis exploiting the multi-pumping concept is proposed and applied to the spectrophotometric determination of glucose and fructose in invert sugar syrups. The samples are collected in gelatin capsules and brought to the laboratory. The capsules are placed directly into the dissolution chamber of a flow-batch system, therefore, the manual sample dissolution step is not required. All the involved analytical steps, including the capsule dissolution under acidic conditions, are efficiently controlled by using discretely actuated solenoid micro-pumps. Glucose and fructose determinations involve sugar oxidation by periodate and evaluation of the remaining periodate by monitoring the tri-iodide complex formed after addition of potassium iodide. The proposed system is very stable, handles about 50 samples per hour and requires 28.8 μg NaIO4 and 2.5 mg KI per determination. Precise results (R.S.D. < 2%) in agreement with HPLC are obtained.