First Method for Trace-Level Quantification of the Potential Genotoxic Impurity Bis(neopentyl glycolato)diboron Using GC–MS

B2(neo)2 is emerging as the preferred borylating reagent for Suzuki coupling reactions, outperforming widely used alternatives such as bis(pinacolato)diboron (B2pin2) and tetrahydroxy diboron (BBA). This preference is attributed to its greater reactivity and ease of handling, notably because it minimizes the risk of hydrogen evolution. Moreover, the lower stability and presence of oligomers in boronic acids further highlight the advantages of B2(neo)2. However, many boronic acid and ester reagents pose a risk as potential genotoxic impurities (GTIs), requiring stringent control strategies in drugs and formulated drug products. This article presents the first highly selective and specific analytical method for the precise quantification of bis(neopentyl glycolato)diboron [B2(neo)2] in active pharmaceutical ingredients (APIs) and intermediates using gas chromatography–mass spectrometry (GC–MS). Although the analyte of interest did not exhibit an M•+ ion in GC–MS, its fragments were well-characterized by gas chromatography-high-resolution mass spectrometry. Quantification relied on the signature fragment of m/z 211 and another intense fragment of m/z 69, while additional fragments of m/z 55, 56, and 70 were utilized for qualification. A systematic method optimization was conducted in the selected ion monitoring mode involving column screening, gas flow, and oven program optimization using the most intense fragment of m/z 69. The final optimized method was validated in compliance with ICH guidelines, using Losartan as a model API. It achieved a limit of detection of 2 ppm (0.01 ppm) and a limit of quantification of 10 ppm (0.05 ppm). The method demonstrated linearity from 10 ppm (0.05 ppm) to 200 ppm (1 ppm), with recovery values between 88 and 106%.