The SENTRY CCM is connected to the plating tool via recirculation loops. Samples are drawn automatically, processed, and spiked with IQSs, which are custom-synthesized to be as nearly identical as possible in composition and structure to the analytes being measured. This high level of similarity ensures accurate and repeatable quantitation of the analytes. Once prepared, the samples are injected into an ESI-TOF MS for mass analysis. The electrospray ionization source allows for efficient conversion of solution-phase ions into the gas phase, while the TOF mass analyzer provides high mass resolution. The SENTRY CCM achieves high sensitivity by incorporating a hexapole ion guide for ion accumulation between the electrospray ionization source and the TOF mass analyzer. By varying the accumulation time, high sensitivity can be achieved for even low-count ion populations.

Following spectral acquisition, Metara’s data-analysis software compares the area of the analyte peak to the area of the IQS reagent peak. Because the concentration of the IQS reagent added during the sample preparation is known, the ratio of the analyte peak area to the IQS peak area determines the unknown concentration of the analyte in the sample being measured. The IQS reagent acts as an in situ calibration for each measurement. Traditionally, calibration curves must be constructed prior to quantitative analytical analysis These calibration curves result in inaccuracies due to the inherent drift present in all analytical techniques. In situ calibration guarantees that each sample and calibration standard undergo the same variations during both sample preparation and measurement. This results in extremely accurate quantitation because instrument drift is negated.

As the organic additives present in a plating bath age, they are broken down into products that can be either electrochemically active or inactive. While the legacy CVS (cyclic voltammetric stripping) metrology is blind to the inactive breakdown products, the active breakdown products will interfere with the measurement of the intact additives. Regardless of their activity, all breakdown products can be quantified and monitored by the SENTRY CCM. Since the SENRY CCM performs a direct measurement of each component, it is immune to the affects of the breakdown products. Therefore, a true measurement of the additive concentrations can be made.