On February 1, 2026, the United States Pharmacopeia (USP) officially implemented General Chapter <317>, ICO-OES Testing for Sodium Hydroxide and Potassium Hydroxide. This revision formally recognizes inductively coupled plasma–optical emission spectrometry (ICP-OES) as an approved alternative analytical method for determining assay and elemental impurities in sodium hydroxide and potassium hydroxide. This update resolves long-standing challenges associated with traditional flame atomic absorption spectroscopy (AAS), including inconsistent stability, limited reproducibility and sensitivity constraints.
The adoption reflects the ongoing modernization of compendial methods and introduces a more robust and sensitive analytical approach for excipient and pharmaceutical manufacturers.
Addressing limitations of traditional methodologies
Traditional AAS methodologies have presented several performance constraints, including:
- Ionization interference affecting analytical accuracy
- Suboptimal calibration curve linearity
- Limited reproducibility and applicability
- Insufficient analytical sensitivity
To help resolve these issues, the USP Excipient Test Methods Expert Committee (ETM EC) partnered with laboratories worldwide to evaluate next‑generation approaches. After an extensive benchmarking process, ICP‑OES showed clear improvements in sensitivity, operational efficiency and overall method stability. The technique also supports accurate measurement of sodium at 589.592 nm and potassium at 766.490 nm, reducing ionization‑related errors.
From method development to pharmacopeial adoption
The integration of ICP-OES into the USP followed a structured development and revision pathway, supported by industry collaboration.
Our laboratories have played a key role throughout this process:
- 2018 – Method development: Physical and chemical laboratories developed and fully validated an ICP-OES method for sodium determination in USP sodium hydroxide, demonstrating superior stability compared with the compendial AAS method
- 2020 – Regulatory submission: The validated method and supporting data were submitted to the USP ETM EC to support inclusion in the revision pathway
- 2022-2024 – Public consultation: The proposed method was published for public comment in the National Formulary (2022) and USP (2024)
- 2026 – Official adoption: ICP-OES was formally accepted as an approved alternative method under General Chapter <317>
This progression highlights the rigorous evaluation required for incorporation of new analytical technologies into pharmacopeial standards.
Analytical and regulatory implications
The implementation of ICP-OES under General Chapter <317> establishes a new analytical option for manufacturers performing sodium and potassium hydroxide testing.
Key technical attributes of the ICP-OES method include:
- High sensitivity for sodium and potassium quantification, minimizing ionization interference
- Improved repeatability and reproducibility compared with AAS
- Demonstrated equivalence to compendial requirements, supporting regulatory submissions
The revision supports modernization of release testing while maintaining alignment with regulatory expectations.
Supporting accelerated cGMP release testing
Leveraging a cGMP laboratory in China that has successfully passed multiple on-site quality management system inspections by the US Food and Drug Administration (FDA), we are proud to provide:
- One-stop release testing for pharmaceuticals and APIs in accordance with global pharmacopeias
- Method development and validation aligned with ICH guidelines and specific client requirements
- Global regulatory support supporting compliance with OECD, FDA, NMPA, ICH and EMA expectations to facilitate market access
Innovation driving quality and compliance
The inclusion of ICP‑OES within the USP signals continued advancement in analytical science and highlights the importance of industry collaboration in strengthening pharmacopeial standards. By making ICP‑OES available for routine use, manufacturers can achieve more consistent results, shorten development steps and maintain strong alignment with global quality expectations.
Learn more about our pharmaceutical analytical services and how we can support you with global regulatory support.
About SGS
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