Automated Water Analysis of Foodstuffs.

Water determination methods should not only be very accurate but also fast, say Metrohm. There are several methods for determining water in foods with Karl Fischer (KF) moisture analysis being the preferred method within the industry. The nature and special characteristics of each sample, as well as the chemical state of the water in it, determine the appropriate method for the water measurement. Bulk or free water is easy to determine using several methods. On the other hand, the determination of tightly bound water is very difficult and can only be achieved using a limited number of methods. Certain samples must first be pulverized before the determination to release the substances of interest." One such method is by volumetric KF in conjunction with a high speed homogeniser.

Metrohm, as market leaders for instrumentation for Karl Fisher analysis, have designed such a system which can be completely automated, with the ability to analyse up to 100 samples at a time. The system incorporates the flexibility and accuracy of the Metrohm Sample Processor Instruments. Sample size reduction and homogenization can be carried out, for example, with the Polytron 1300 D homogenizer from Kinematica. To trigger the required actions, transfer commands are used to send defined three-digit numerical codes from Metrohms very own tiamo titration software to the control unit of the homogenizer. Not only can the instrument be switched on and off, its speed can also be set in the range 7000...30,000 rpm. It is also possible to vary the speed of rotation within the method sequence to adapt it to the particular conditions. For instance, the sample can be disintegrated at 25,000 rpm with the subsequent determination taking place at 7000 rpm". If the 786 Swing Head of the Robotic Sample Processor is equipped with the Robotic Arm then the homogenizer can even be used with multiple-row sample racks. This means that large sample series can be processed without any problem.

Between determinations the homogenizer can be cleaned automatically by one of two methods. The stirrer is either immersed in a special beaker containing a rinsing solution (e.g. water/ethanol mixture) and switched on briefly, or cleaning can be carried out using the spray nozzles built into the titration head of the Robotic Arm. In both cases carryover is reliably prevented and accuracy and precision is improved since the analysis is performed in the same way each and every time.