Recovery Test for Sodium Dodecylbenzenesulfonate by TOC-V WS

Importance of the Topic

Analysis of total organic carbon (TOC) is a critical quality control measure in pharmaceutical and industrial laboratories. Accurate determination of organic carbon levels ensures compliance with pharmacopeial standards and safeguards product purity. This application demonstrates how the Shimadzu TOC-VWS wet chemical oxidation analyzer fulfills stringent requirements for both recovery testing and low-level TOC measurement.

Objectives and Overview of the Study

The study aimed to verify two performance criteria defined by the Japanese Pharmacopeia: 1) recovery of sodium dodecylbenzenesulfonate carbon at 0.500 mg/L with at least 90% efficiency; and 2) precise TOC quantification below 0.05 mg/L. Recovery testing and low-level measurement capability were both evaluated using the Shimadzu TOC-VWS.

Methodology and Instrumentation

The analysis employed the TC-IC method for TOC determination. Carbon calibration curves were generated from aqueous potassium biphthalate (TC) and sodium carbonate/bicarbonate (IC) standards spanning 0–1 mgC/L. A calibration shift-to-origin correction removed background carbon from ultrapure water. For recovery assessment, a commercial sodium dodecylbenzenesulfonate solution (0.806 mg/L; 0.500 mgC/L) was measured. Low-level TOC testing used a potassium biphthalate solution adjusted to approximately 0.04 mg/L TOC with the acidify-and-sparge method.

Instrumentation

• Analyzer: Shimadzu Wet Chemical Oxidation TOC Analyzer TOC-VWS
• Measurement Mode: TC-IC with acidify-and-sparge pretreatment
• Calibration Range: 0–1 mgC/L

Main Results and Discussion

Recovery testing returned a measured carbon value of 0.494 mg/L from a nominal 0.500 mgC/L sample, corresponding to a recovery rate of 98.8%. This performance exceeds the 90% requirement set by the Japanese Pharmacopeia. Low-level TOC analysis yielded accurate results at ~0.04 mg/L with a coefficient of variation below 1%, demonstrating excellent precision and sensitivity.

Benefits and Practical Applications

• Pharmacopeial Compliance: Meets JP specification for recovery and low-level detection.
• Quality Assurance: Reliable TOC measurement for raw materials, intermediates, and final products.
• Process Monitoring: Suitability for monitoring trace organic contaminants in water and formulations.

Future Trends and Possibilities

Further enhancements may include higher-throughput autosamplers, miniaturized reagent consumption, and integration with laboratory information management systems (LIMS). Advances in oxidation chemistry and detection technology could push LOQ even lower, addressing emerging regulatory demands.

Conclusion

The Shimadzu TOC-VWS analyzer demonstrated robust recovery for sodium dodecylbenzenesulfonate and precise quantification at sub-0.05 mg/L levels, fully satisfying the Japanese Pharmacopeia’s organic carbon test requirements. Its reliable performance supports rigorous quality control and broad applicability in pharmaceutical and industrial laboratories.