Isocratic ion pair chromatography for estimation of novel combined inhalation therapy that blocks coronavirus replication in chronic asthmatic patients

A rapid and sensitive isocratic ion-pair chromatographic method was developed for the accurate analysis of ternary mixtures of formoterol, tiotropium, and ciclesonide in their novel combined inhalation that is widely used for the symptomatic treatment of patients with chronic obstructive disease. Analytical separation was performed using a C 8 column and ion pair mobile phase composed of acetonitrile: acidified deionized water (55: 45% v/v) containing 0.025% sodium dodecyl sulfate. The pH was adjusted to 3.0 using orthophosphoric acid and eluted isocratically at 2.0 mL/min and 40 °C applying UV detection at 237 nm. The calibration ranges were found to be 0.3–9.0 µg/mL for formoterol, 0.45–13.5 µg/mL for tiotropium, and 10.0–300.0 µg/mL concerning ciclesonide. The proposed method exhibited good repeatability, accuracy, and sensitivity (R.S.D.