3-D amperometry is a new technique introduced with the ICS-3000 Chromatography system. It allows postrun analysis of multiple integration periods to determine the ideal integration period for a particular compound. This allows specific detection and the use of integration ratios to determine if analytes have unique signatures based on their oxidation/reduction properties. In the figure below, the top illustration shows a typical waveform and integration period for the conventional AAA-Direct waveform. During postrun data analysis, two integration periods were applied to the respective data set. Labeled numerator and denominator, the peak areas generated from these integration periods were used to determine peak area ratios for Leucine, HEPES and Dulbecco's Media.

3-D amperometry is a new technique introduced with the ICS-3000 Chromatography system.

• In the analysis of the cell culture media Dulbecco's Modified Eagle's F-12 Mixture using AAA-Direct^™, initial results suggested a Leucine concentration 10X higher than reported on the label.
• Further analysis suggested a coeluting peak.
• 3-D amperometry was used to determine and quantify that the coeluting peak was HEPES buffer. 1-D amperometry is integration of a certain period within a waveform. The solid red line within the waveform shows the integration period of the waveform. This is illustrated in the figure below.

The peak area ratios determined in these experiments are shown in the table below. From these studies, it was determined that the major component in the peak was actually HEPES buffer.

3-D amperometry is rapidly advancing the analysis capabities of electrochemical detection. In conjunction with new types of working electrodes, analyte identification in complex matrices will become even more powerful.