Evaluating Substitution of Hazardous Solvents in USP Monograph HPLC Methods.

Abstract

BACKGROUND: Hazardous solvents, such as dichloromethane (DCM), n-hexane, and acetonitrile (ACN), are widely used in HPLC methods, posing significant health and environmental risks. OBJECTIVE: To evaluate the feasibility and impact of substituting hazardous solvents with greener alternatives in USP monograph methods. METHODS: Six high-impact solvents were identified from USP-NF monographs. Two representative monographs per solvent were selected. Substitution strategies were assessed, and performance was compared using system suitability and sample acceptance criteria. Greenness improvement was evaluated using the Analytical GREEnness (AGREE) metric. RESULTS: Performance remained equivalent across all twelve substitution cases. In almost every instance, only the mobile phase required modification, either by direct substitution or by adjusting the solvent-to-buffer ratio, except for one case that required a minor adjustment in column temperature. The AGREE Greenness metric increased by 18-65% in ten out of twelve cases; for n-hexane, improvements were modest at just 6% when replaced with n-heptane but exceeded 40% when substituted with supercritical CO₂. CONCLUSIONS: Greener solvents are highly likely to replace hazardous solvents used in compendial chromatography methods without loss of performance. HIGHLIGHTS: Demonstrated performance equivalency for greener solvent substitutions; Quantified greenness improvements using AGREE; Discussed strategies to implement greener solvents in USP monograph methods.