Use of transmitted room-temperature phosphorescence to improve nalidixic acid determination

A method for nalidixic acid (NA) determination by transmitted room-temperature phosphorescence is proposed, The antibacterial agent NA in acidic solution shows native fluorescence; when NA is spotted on a filter paper precoated with beta-cyclodextrin and lead (II) acetate and dried for 5 min, phosphorescence results, The transmitted phosphorescence was measured directly with the use of a homemade sample holder, The excitation and emission wavelengths were 330 and 417 nm, respectively. The applicable concentration range was between 0.06 and 4.50 mu g/mL with a relative standard deviation of 2.8% and a detection limit of 0.02 mu g/mL. The method was applied to the determination of NA in human urine and pharmaceuticals, with recoveries from 97.5 to 105.5%.