A new validation approach applied to the GC determination of impurities in organic solvents

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Organic solvents such as methanol, acetone, dichloromethane or toluene are frequently used in the pharmaceutical industry. The manufacturing of new active pharmaceutical ingredients (APIs) under GMP conditions commands to control adequately the quality of the different ingredients happening in the synthesis. Organic solvents have therefore to be controlled and their purity has to be determined before any GMP synthesis. A selective gas chromatography (GC) method has been developed to determine the purity of acetone, dichloromethane, methanol and toluene. Using this method, the main contaminants of each organic solvent can be quantified. Moreover, the developed method allows the simultaneous determination of ethanol, isopropanol, chloroform, benzene, acetone, dichloromethane, methanol and toluene. Propionitrile was used as the internal standard. The separation was obtained on a CP-SIL 8-CB low bleed/MS column (60 m × 0.32 mm i.d. × 1.0 μm coating thickness). The GC method was fully validated using a new approach based on the accuracy profile as a decision tool. The determination of β-expectation tolerance intervals for the estimation of total error – including both bias and precision – is used to better reflect the actual performances of the method, which is definitively the objective of the validation. The different validation criteria such as selectivity, response function, trueness, precision, accuracy, linearity or limits of detection and quantification were considered. The method was found to be able to quantitate with a good accuracy impurities around the 0.1% (v/v) concentration level for the different solvents.