In the current work, an automated procedure for photometric determination of N-ureide in soybean tissues is described. The photometric procedure was based on the reaction of N-ureide with hypochlorite, followed by its reaction with phenol in an alkaline medium, forming the indophenol blue compound, monitored at 660 nm. The flow system manifold based on the multicommuted process was tailored to allow its integration with a LED-based photometer in order to form a compact unit. After setting the appropriated operational conditions related with instrument setup and analytical procedure, the overall effectiveness was ascertained by the determination of N-ureide in soybean tissues. Accuracy assessed by applying the paired t-test between results obtained using a reference method showed that there is no significant difference at 95% confidence level. Other useful features were also achieved, such as a linear response ranging from 30 up to 260 µmol L-1 N-ureide (r = 0.9995); a detection limit of 1.0 µmol L-1 N-ureide, a relative standard deviation of 3% (n = 15), consumption of 0.55 and 6.8 mg hypochlorite and phenol per determination, respectively; waste generation of 3.3 mL per determination and sampling throughout 36 determinations per hour.
multicommuted flow analysis; LED-based photometer, N-ureides; soybean; green chemistry
