BACs and DADMACs in solutions were quantified using a liquid chromatography (LC) system ( Infinity II) equipped with a single quadrupole mass selective detector (MSD) (Agilent Technologies, Santa Clara, CA). All samples were spiked with an internal standard and diluted as necessary. A Kinetex EVO C18 column (2.6 µm particle size, 2.1 mm i.d. × 50 mm) was used for separation. Gradient elution was performed using aqueous ammonium acetate solution (10 mM), acetonitrile, and isopropanol as eluents. All compounds were measured with m/z values corresponding to their molecular masses.