“…A differential UV spectrophotometric procedure has also been used for the determination of MTD in pharmaceutical formulations in the presence of germanium dioxide at 292 nm (Davidson, 1984). MTD has been determined in the visible region after reaction with 2,3,5-triphenyltetrazolium chloride (El-Rabbat, Omar, 1978), potassium bromate (Mohamed, Salem, 1984), vanillin (Salem, 1985, p-dimethylaminocinnamaldehyde (Walash, Abououf, Salem, 1985), molybdophosphoric acid in sulphuric acid medium (Issopoulos, 1989), Fe(III), o-phenanthroline (Issopoulos, 1990), ferric chloride (Zivanovic, Vasiljevic, Radulovic, 1991), neotetrazolium chloride (Issopoulos, Economou, 1993), metaperiodate (Nevado, Gallego, Laguna, 1995), barbituric acid (Aman et al, 1998), isoniazid in the presence of N-bromosuccinimide (Nagaraja et al, 1998), polyphenol oxidase enzyme (Vieira, Fatibello Filho, 1998), diazotized sulfanilamide in the presence of molybdate (Nagaraja, Vasantha, Sunitha, 2001a), semicarbazide hydrochloride in the presence of potassium persulfate (Nagaraja et al, 2001b), ammonium molybdate (Ribeiro et al, 2005a;Ribeiro, Pezza, Pezza, 2005b), 2,2-diphenyl-picrylhydrazyl (Matos, Silva, Ribeiro, 2012) and ferric chloride/nitroso-R-salt (Al Abachi, Hadi, 2013). However, most of these methods suffer from several disadvantages, such as long-waiting times or a heating step for reaction development, instability of the colored species, complex procedure, requirement for nonaqueous media, poor detection limit, or lack of previous application to pharmaceutical formulations.…”