Flow-Injection Spectrophotometric Determination of Novalgin in Pharmaceuticals Using Micellar Medium

Patrícia Los WEINERT1), João Roberto FERNANDES2), Leonardo PEZZA1) and Helena Redigolo PEZZA1)

1) Instituto de Química-UNESP 2) Departamento de Química-FC/UNESP

(Received April 23, 2007) (Accepted July 17, 2007)

A sensitive flow-injection (FI) procedure with spectrophotometric detection in a micellar medium is proposed for the determination of novalgin. The method is based on the instantaneous formation of a red-orange product (λmax = 510 nm) after the reaction between novalgin and p-dimethylaminocinnamaldehyde (p-DAC) in a dilute acid medium. The sensitivity of this reaction was increased by a factor of 5.6 in the presence of sodium dodecyl sulfate (SDS). Experimental design methodologies were used to optimize the chemical and FI variables. The calibration curve was linear in the range of 1.45 × 10-6 to 2.90 × 10-5 mol L-1 with an excellent correlation coefficient (r = 0.9999). The detection limit was 1.31 × 10-7 mol L-1 (n = 20, RSD = 2.0%). No interferences were observed from the common excipients. The results obtained by the proposed method were favorably compared with those given by the iodometric reference method at 95% confidence level.

Anal. Sci., Vol. 23, p.1383, (2007)