Micro-magnetic particles frit for capillary electrochromatography

This paper presents a new method for making frit using soft-ferrite-based micro-magnetic particles (MMPs) in a micro-space, such as in a capillary tube. The MMPs-frit was made by injecting an aliquot of 10 μm (outer diameter; o.d.)-MMPs-suspension in methanol (ca. 1 mg/ml) into a capillary tube (75 μm inner diameter (i.d.) × 375 μm o.d. × ca. 35 cm length) that was already sandwiched between a pair of cylindrical Neodium (Nd-Fe-B) magnets (1.5 mm o.d. × 1.5 mm height, 280 mT) at a position where the frit was made. The MMPs were trapped in the capillary tube as a frit due to the attraction of the magnets placed at surface on the capillary tube. With regard to durability, the frit was stable for methanol flow with a flow rate of 400 μl/min at room temperature. Using such a frit, a capillary column (20 cm long) was prepared by injecting a 5 μm (o.d.)-ODS-particle suspension in methanol (ca. 0.4 mg/μl) into the capillary tube. The MMPs-frits-ODS-packed column was stable for methanol for a flow pressure less than 20 MPa. When comparing the present column with a conventional sintered-frits-ODS-packed column for the purposes of separating five kinds of biogenic amines by means of an on-column derivatization capillary electrochromatography (CEC), the performance of the MMPs-frits capillary column was almost equivalent to that of the sintered-frits-ODS-packed column.