Plasticizer migration test parameters and data analysis

A plasticizer migration test attempted to detect bisphenol A (BPA) and six common phthalates found in medical devices, namely butyl benzyl phthalate (BBP), di-n-butyl phthalate (DBP), di(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DNOP), diisononyl phthalate (DINP), and diisodecyl phthalate (DIDP). BPA calibration standards were prepared with a series of acetonitrile dilutions. A six-point calibration curve was established, covering a range of 50–500 ng/mL. Custom phthalate calibration standards were prepared using a series of methanol dilutions, with concentrations ranging from 50 to 500 ng/mL. An aliquot of 990 μL from each phthalate standard was mixed with 10 μL of internal DEHP-D4 standard stock solution (24.9 ppm) to prepare a calibration curve. The concentration of the internal standard at each calibration level was 249 ng/mL. The concentration of BPA and six phthalates were verified using the linear calibration curves.

The LC-MS/MS analysis for BPA was performed using an API 4000 system (Applied Biosystems), with an Agilent 1260 series HPLC system (MN, USA). Phthalate was analyzed using an API 3200 System (Applied Biosystems), with an Agilent 1200 series HPLC-DAD system. Both HPLC systems were equipped with an Agilent Eclipse XDB-C8 column (150 × 2.1 mm, 3.5 μm particle size). For the BPA assay, the test solution was first diluted 20 times with acetonitrile. The mobile phase comprised an equal mixture of deionized water and acetonitrile. The injection volume was 5 μL, and the flow rate was 0.4 mL/min. Mass spectrometry (MS) was performed in negative electrospray ionization (ESI) mode with a capillary voltage of −4500 kV, nitrogen gas (40 L/h), and a desolvation temperature of 450°C. Multiple reaction monitoring was performed, and BPA ions were scanned at 93.1, 133, and 212 m/z. Conversely, the phthalate assay comprised a gradient mobile phase, prepared from a mixture of water and 5 mM ammonium acetate in methanol. The test solution was diluted 20 times with acetonitrile before loading. The injection volume was 10 μL, and the flow rate was 0.4 mL/min. MS was performed under APCI-positive ESI with a capillary voltage of 5500 V, nitrogen gas (50 L/h and 55 L/h), and a desolvation temperature of 500°C. Multiple reaction monitoring was performed, which detected DEHP-D4 at 153 m/z, BBP at 149, 205, and 239 m/z, DBP at 149, 205, and 121 m/z, DEHP at 149, 167, and 279 m/z, DIDP at 149, 289, and 307 m/z, DINP at 149, 275, and 293 m/z, and DNOP at 149, 261, and 121 m/z. The concentration of the compounds was calculated using the formula: concentration (ng/mL) × dilution factor × volume (mL).