Automated titration system for the assay of absorbent gel materials in diapers

Abstract

The present manual method to quantitatively determine absorbent gel materials (AGM) in diapers utilizes an extraction procedure followed by an acid-base titration. However, this method is laborious and time-consuming. To overcome this situation, we have introduced a fully automated titration system by integrating automated extraction baths, and an autotitrator. The novel system contains a Zymate XP robot, three sample racks (36 pads/rack), a Mettler titrator, three bubbling extraction baths, three pumps, two balances, and a waste container. A paddle mixer was previously used to facilitate extraction of the AGM out of diapers. However, this method requires skillful people and a fairly long sample-preparation time. A new bubbling air method was developed, and the results give more than 98% recovery after 6 minutes of bubbling. Three bubbling extraction baths are used simultaneously, providing a greater number of sample preparations per unit of time. This robotic system was developed to automatically prepare samples, react AGM with excess HCl, and titrate the excess HCl with NaOH. The amount of AGM in the diaper is automatically calculated using of a Microsoft Excel spreadsheet. © 1997 John Wiley & Sons, Inc. Lab Robotics and Automation 9: 237–242, 1997