Determination of nitrofurantoin in pharmaceutical preparations using flow injection-spectrophotometry

Nitrofurantoin (NIT) is used as an antibiotic for the treatment of urinary tract infection. To determine the concentration of NIT in pharmaceutical preparations, two cost-effective extraction-free flow injection (FI) spectrophotometric methods (direct and indirect) were studied. The direct FI method was based on the reaction of NIT with potassium hydroxide and the formation of a red/orange coloured product with absorbance measured at 471 nm. The indirect method used a reduction reaction of NIT and involved an oxidative coupling step with 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH). The second method resulted in a green coloured product with absorbance measured at 610 nm. Both direct and indirect FI methods were in agreement with Beer's law over a concentration range of 5-300 µg/mL. In addition, the limit for detection of the reaction product for direct and indirect method was 1.9 and 4.8 µg/mL, respectively. FI spectrophotometric methods used in the present study can be applied for the analysis of NIT in different pharmaceutical dosage forms.