Determination of Tartaric Acid in Tolterodine Tartrate Drug Products by IC with Suppressed Conductivity Detection

Importance of the topic

Counterion analysis in pharmaceutical salts is critical for verifying drug identity, dosage accuracy, and safety. Tolterodine tartrate, a quaternary ammonium compound used to treat urinary incontinence, requires precise quantification of its tartaric acid counterion to ensure product quality and regulatory compliance.

Objectives and study overview

This work aimed to develop and compare two ion chromatography methods for rapid and accurate determination of tartaric acid in tolterodine tartrate capsules. One method employs electrogenerated hydroxide eluent, while the other uses manually prepared carbonate/bicarbonate eluent.

Methodology

Sample preparation involved opening and averaging the weight of five capsules (average 0.184 g each), dissolving the powder in water, sonicating, filtering, and diluting to yield approximately 12.6 mg/L tartaric acid. Standards were prepared from a 1000 mg/L tartaric acid stock to obtain working concentrations of 5, 10, 15, and 20 mg/L.

Chromatographic conditions:

• Condition 1: IonPac AS20 column, 20 mM KOH eluent generated by eluent generator module, flow rate 1.0 mL/min, injection volume 10 µL, column temperature 30 °C, suppressed conductivity detection, run time 10 min.
• Condition 2: IonPac AS22 column, 6 mM Na₂CO₃/1.4 mM NaHCO₃ manual eluent, flow rate 1.2 mL/min, injection volume 10 µL, column temperature 30 °C, suppressed conductivity detection, run time 12 min.

Used instrumentation

Analysis was performed on a Thermo Scientific RFIC system comprising a dual gradient pump, eluent generator module, CR-ATC trap column, ASRS 300 suppressor, autosampler, and Chromeleon CDS software.

Main results and discussion

Both methods showed excellent linearity (r² ≥ 0.9990) over the 5–20 mg/L range. The assay results averaged 98.4% (Condition 1) and 96.0% (Condition 2) of the label claim, with RSD ≤ 0.74%. Spiked recoveries ranged from 100% to 103%, confirming method accuracy.

Benefits and practical applications

Electrogenerated eluent automation eliminates manual reagent preparation, reduces error risk, and achieves higher throughput. The carbonate/bicarbonate approach offers a robust manual alternative with straightforward reagent handling.

Future trends and applications

Advancements in eluent generation technology, fast IC columns, and data integration are expected to further shorten analysis times, improve sensitivity, and expand multi-anion profiling capabilities in pharmaceutical quality control.

Conclusion

Two validated IC protocols provide reliable, precise, and efficient determination of tartaric acid in tolterodine tartrate capsules. The RFIC-based hydroxide method offers the fastest analysis, while the carbonate/bicarbonate method remains a dependable option for routine QC laboratories.

References

• Dionex Application Note 190 Determination of Sulfate Counter Ion and Anionic Impurities in Aminoglycoside Drug Substances by IC with Suppressed Conductivity Detection LPN1946 2007
• Deshpande GR Rao BM Someswararao N Quantitative Determination of Tartaric Acid in Tolterodine Tartrate by IC Using Conductivity Detection RASAYAN J Chem 2009 2 101–107