Fig. 4From: Multiple analytical methods for determination of formoterol and glycopyrronium simultaneously in their novel combined metered dose inhalerFirst derivative of the ratio spectra of GLY (0.9, 1.8, 2.25, 4.5, 9, 13.5 and 18.0 µg/mL) when 3.6 µg/mL FF was used as divisor (240, 259 nm)Back to article page