Micro-Flow Imaging
MFI was used to detect particles up to 70 µm. A MFI5200 (ProteinSimple,
Santa Clara, USA), equipped with a silane coated flow cell
(1.41x1.76x0.1 mm) and controlled by the MFI View System Software
version 2 was used. Prior to each measurement the system was flushed
with purified water. The background was zeroed by using solvent and
performing the optimize illumination procedure. Samples of 1 mg/mL
adalimumab were analyzed without a predefined pre-run volume because of
the limited amount. Flow rate was 0.17 ml/min and camera shot rate was
22 flashes per second. Data was analyzed with MFI View Analysis Suite
version 1.2. For each product, stuck, edge, and slow-moving particles
were removed by the software before analysis. Because no pre-run volume
could be used, the data was recorded throughout the entire run but
processed only in the time window from 0.7 to 1.7 min where, based on
the trend chart option in the software, the measurement was stable for
all samples. The equivalent circular diameter was calculated as
described earlier (20).