Hydrazine determination in allopurinol using derivatization and SPE for sample preparation

Area of Science:

• Analytical Chemistry
• Pharmaceutical Analysis
• Organic Chemistry

Background:

• Hydrazine is a crucial pharmaceutical synthesis intermediate but poses significant toxicity risks.
• Accurate determination of hydrazine at low parts per million (ppm) levels is essential for pharmaceutical safety.
• Allopurinol, an active pharmaceutical ingredient (API), requires stringent quality control for impurities like hydrazine.

Purpose of the Study:

• To develop and validate a sensitive analytical method for quantifying hydrazine in allopurinol API.
• To address the challenge of determining hydrazine, which lacks a chromophore and is not retained in reversed-phase liquid chromatography (RPLC).
• To establish a reliable method applicable to other polar APIs requiring hydrazine impurity analysis.

Main Methods:

• Hydrazine derivatization using benzaldehyde to form a UV-detectable and RPLC-retentive benzaldehyde azine.
• Solid phase extraction (SPE) with a C18 column to remove the highly concentrated allopurinol matrix.
• Reversed-phase liquid chromatography (RPLC) for the separation and quantification of the derivatized hydrazine.

Main Results:

• Successful determination of hydrazine in allopurinol API at a 2.5 ppm level.
• Demonstration that benzaldehyde azine possesses adequate UV absorption and RPLC retention.
• Validation of the liquid chromatographic method for limit testing, confirming its accuracy and reliability.

Conclusions:

• The developed method, involving derivatization and SPE-RPLC, accurately quantifies low ppm levels of hydrazine in allopurinol API.
• This analytical approach is effective for overcoming challenges associated with hydrazine's lack of chromophore and RPLC non-retention.
• The method's applicability extends to other APIs that are more polar than benzaldehyde azine and soluble in aqueous solvents at high concentrations.