Screening of conditions controlling spectrophotometric sequential injection analysis

Area of Science:

• Analytical Chemistry
• Spectrophotometry
• Chemometrics

Background:

• Chemometrics offers advantages over univariate methods but is underutilized for optimizing sequential injection analysis (SIA).
• Previous vis-spectrophotometric SIA optimization focused narrowly on flow rate and reagent concentrations, neglecting other critical parameters.

Purpose of the Study:

• To comprehensively screen and identify critical conditions influencing vis-spectrophotometric SIA performance.
• To develop and validate a novel SIA method for diclofenac determination using chemometric optimization.

Main Methods:

• A new vis-spectrophotometric assay for diclofenac was developed, involving oxidation by permanganate in sulfuric acid.
• A 26 full-factorial design was employed to systematically evaluate the impact of sample/reagent volumes, flow rate, and reagent concentrations.
• Method performance was assessed based on sensitivity, rapidity, and reagent consumption.

Main Results:

• The study identified the relative importance of various factors affecting vis-spectrophotometric SIA performance.
• Diclofenac was successfully assayed in pharmaceutical formulations including tablets, injections, and gels.
• The comprehensive screening provided insights into optimizing similar SIA methods.

Conclusions:

• While 64 experiments were conducted, the findings offer a roadmap to reduce future development time and effort for SIA methods.
• It is recommended to use fractional-factorial design, response surface, or simplex methods for initial optimization over full-factorial designs.
• For vis-spectrophotometric SIA methods with two reagents, the order of influence on performance is: sample volume > flow rate ≈ major reagent concentration >> major reagent volume ≈ minor reagent concentration >> minor reagent volume.