Application of capability indices and control charts in the analytical method control strategy

Area of Science:

• Analytical Chemistry
• Quality Control
• Method Validation

Background:

• Analytical method control is crucial for reliable results.
• Process capability indices (Cpm, Cpk) and control charts are common tools.
• Assessing method capability against stringent requirements is essential.

Purpose of the Study:

• To assess the utility of control charts combined with Cpm and Cpk indices in analytical method control strategies.
• To evaluate method capability using different criteria for specification and control limits.
• To determine if the analytical method meets analyst and analytical target approach requirements.

Main Methods:

• Utilized traditional X-chart and moving range chart for monitoring over two years.
• Applied Cpm and Cpk indices to assess method capability.
• Defined specification limits based on analyst and method requirements.
• Modeled using Size Exclusion Chromatography (SEC) with light-scattering detection data.

Main Results:

• Confirmed the analytical method is in-control and stable over the study period.
• Found that equal specification and control limits (Cpm = 1) did not meet proposed capability requirements.
• Demonstrated that the method fails to meet the analytical target approach requirements.

Conclusions:

• Control charts and capability indices are useful for assessing analytical method stability.
• The evaluated method, while stable, lacks the required capability for certain stringent applications.
• Further refinement of method performance or requirements is needed to meet analytical target approaches.