A reagent-free method based on a photo-induced fluorimetry in a sequential injection system

According to the current demands of environmentally friendly analytical chemistry and with a view to achieving lower reagent consumption with improved analytical performance, an automatic methodology composed of a photoreactor and fluorimetric detection (λ_exc = 287 nm, λ_em = 378 nm) was developed. To this end, a sequential injection analysis (SIA) system was developed for indomethacin determination using ultra-violet (UV) light which promotes an increase in the fluorescence of indomethacin. This increase in sensitivity makes it possible to apply this methodology to a dissolution test and to determine indomethacin in pharmaceutical formulations.The calibration graph for indomethacin was linear between 4.10 × 10⁻⁶ and 9.00 × 10⁻⁵ mol L⁻¹and the detection limit was 1.23 × 10⁻⁶ mol L⁻¹. The method was proven to be reproducible with a R.S.D. < 5% and sampling rate of approximately 20 per hour. The potential effect of several compounds commonly used as excipients on analytical signals was studied and no interfering effect was observed. Statistical evaluation at the 95% confidence level showed good agreement between the results obtained for the pharmaceutical samples with both the SIA system and comparison batch procedures.