Objective To develop an ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the simultaneous determination of 33 aromatic primary amines in medical-grade thermoplastic polyurethane (TPU).

Methods The target compounds were extracted using 80% methanol and PBS solution containing 10% ethanol as the solvents. The 80% methanol extract was filtered through and diluted to one-fifth of the original concentration. The PBS extract was processed through an HLB solid-phase extraction column (3 mL, 60 mg, methanol and water equilibrium), eluted with 5 mL methanol, filtered, and diluted to 5 mL with methanol. Then, analysis was performed using UPLC-MS/MS. Chromatographic separation was performed using an Agilent InfinityLab Poroshell 120 EC-C18 column (150 mm × 3.0 mm, 2.7 μm) with methanol (A) and deionized water containing 0.1% formic acid (B) as the mobile phases. Gradient elution was conducted with a column temperature of 40 ℃, a flow rate of 0.2 mL/min, and an injection volume of 1 μL. Mass spectrometry analysis was performed using an electro-spray ionization (ESI) source in multiple reaction monitoring (MRM) positive ion mode. The standard curves, quantification limits, precision, recovery rates, and matrix effects of the method under different extraction conditions were evaluated.

Results The 33 aromatic primary amines analyzed in the study showed good linearity (r > 0.998) within the 2-100 ng/mL concentration range. Detection limits ranged from 0.1 to 0.5 ng/mL, and quantification limits ranged from 0.3 to 1.7 ng/mL. Recovery rates for the 33 aromatic primary amines in 80% methanol samples ranged from 70.7% to 116.0%. Recovery rates for 31 aromatic primary amines in PBS samples containing 10% ethanol ranged from 74.9% to 113.8%. The intra-day and inter-day precision for different samples was both less than 10%, indicating good sample stability. Analysis of aromatic primary amine content in sample extracts using this method revealed that methylenedianiline (MDA) was detected in all 6 initially tested samples. Under simulated extraction at 37 ℃ and accelerated extraction at 60 ℃, 3 samples exhibited continuous or delayed MDA release. 2,4'-MDA was detected in 2 samples during the initial limit extraction phase and remained detectable in 1 sample under 60 ℃ accelerated aging conditions, but no release was observed under the 37 ℃ simulated physiological environment. 2,2'-MDA was detected only in two samples during initial limit extraction and was not released in subsequent simulated or accelerated extraction processes.

Conclusion The UPLC-MS/MS method demonstrates high sensitivity and accuracy, meeting the requirements for precise detection of 33 aromatic primary amines in medical-grade TPU and providing reliable technical support for risk assessment and quality control of aromatic primary amines in these materials and products.