The development and comparison of a fluorescence and a phosphorescence optosensors for determining the plant growth regulator 2-naphthoxyacetic acid

We describe two luminescence methods based on a flow-through optical sensor. A fluorescence and a phosphorescence optosensors have been developed and compared. Both techniques are fast (response time of 150 and 90 s, respectively) and simple. The fluorescence optosensor is based on the on-line immobilization of 2-naphthoxyacetic acid (β-NOA) on a non-ionic resin (Amberlite XAD-7) solid support in a continuous-flow system (10 mM glycine/HCl buffer solution at pH 2.5) and the phosphorescence one on the on-line immobilization of β-NOA on silica gel solid support in a 175 mM TlNO3 and 10 mM Na2SO3 continuous-flow system. Fluorescence and phosphorescence intensities were measured at λexc/em = 328/348 and 276/516 nm, respectively. The fluorescence optosensor was sensitive to a linear concentration range of between 2.0 and 225.0 ng mL−1 with a detection limit of 2.0 ng mL−1 and a standard deviation of 2.8% at 125 ng mL−1, and for the phosphorescence a linear concentration range between 4.9 and 250.0 ng mL−1, a detection limit of 4.9 ng mL−1 and a standard deviation of 2.23% at 150 ng mL−1. Also, a study of applicability was carried out obtaining recovery percentages around 100% with standard deviations slower than 2.2%.