A simple, sensitive, and rapid spectrophotometric method for the assay of glyphosate (= N-(phosphonomethyl)glycine) in various formulations (Roundup, Excel Mera 71) and environmental water samples is described. The method is based on the reaction of glyphosate with ninhydrin in presence of sodium molybdate in neutral aqueous medium at 1008 to give a Ruhemanns purple product having the VIS absorption maximum at 570 nm (Scheme, Fig. 1). The product is stable for 10 h. Beers law is obeyed in the concentration range of 0.1 -3.5 mg ml À1 . The molar absorptivity and Sandells sensitivity are 3.2816 · 10 4 l mol À1 cm À1 and 5.2 ng cm À2 , respectively ( Table 1). The method is highly reproducible, as confirmed by the relative-standard-deviation (r.s.d.) values (1.70%; Table 2). Recovery studies establish that this method is accurate ( Table 5) and can be successfully employed for the determination of glyphosate.

A simple, rapid and sensitive spectrophotometric method has been developed for the trace determination of nitrite using Dapsone and α-Naphthol. The proposed method is based on the diazotization of Dapsone followed by coupling with α-Naphthol in sodium hydroxide medium to give an intense pink coloured azo dye. The dye shows absorption maximum at 540 nm. The molar absorptivity and Sandell’s sensitivity being 5.749 × 104l mol-1cm-1and 0.24 ng cm-3respectively. Tolerance limit for interfering ions and complexing agents were reported. Other analytical parameters and applications of the method for analysis of tap water, lake water, and industrial effluents have been investigated.

A rapid, sensitive Spectrophotometric method for the determination of ultra trace amount of carbaryl (1- Napthyl-N- Methyl Carbamate) is proposed. The method is based on an alkali hydrolysis of carbaryl in the presence of methanolic KOH, followed by coupling with diazotized 4-41- diaminodiphenyl sulfone in an alkaline medium. The water soluble pink dye obtained shows an absorption maximum at 540 nm. The system obeys Beer’s law over the range of 0.06-2.0μg mL-1. The absorptivity of the coloured product is 7.014 × 104l mol-1cm-1and the developed colour is stable for 48h. The detection limit of Carbaryl is 0.0102 μg mL-1. This method is a very good alternative tool and it can be used successfully for the determination of carbaryl residue in environmental water and grain samples.

A sensitive and rapid spectrophotometric method for the determination of reduced methyl parathion (=O,O-dimethyl O-(4-nitrophenyl) phosphorothioate) is described. The method is based on the interaction of diazotized reduced methyl parathion with 8-hydroxyquinoline (=quinolin-8-ol; 8-HQ) and 3-aminophenol (3-AP) as new coupling agents. Absorbances of the resulting chromophores are measured at 430 and 440 nm, respectively, and colored products were stable for at least 2 days. Beer's law is obeyed over the methyl parathion concentration range 0.2-5.5 microg ml(-1) for 8-HQ and 0.5-6.0 microg ml(-1) for 3-AP. From the data, it was confirmed that the two coupling agents can be effectively applied for the determination of methyl parathion in environmental and commercial samples.