MICELLAR MODIFIED SPECTROPHOTOMETRIC DETERMINATION OF NITROBENZENES BASED UPON REDUCTION WITH TIN(II), DIAZOTIZATION AND COUPLING WITH THE BRATTON-MARSHALL REAGENT

Nitrobenzenes, such as the antibiotic chloramphenicol, the vasodilator nicardipine, and the herbicides dinitramin, dinobuton, fenitrothion, methylparathion, oxyfluorfen, parathion, pendimethalin, quintozene, an d trifluralin, were determined by using a spectrophotometric method in the visible region (540 nm). The method was based on the reduction of the nitrobenzenes to arylamines with tin(II) chloride, diazotisation of the arylamines and coupling of the diazonium ions with the Bratton- Marshall reagent. The two latter reactions were performed in a micella r medium of sodium dodecyl sulphate. The linear calibration range was 2 x 10(-6) to 7_x 10(-5) M (r> 0.999), with limits of detection in the 10(-7) M level, which is 2-6 fold lower with respect to the correspon ding spectrophotometric procedure in non-micellar medium. The procedur e was applied to the analysis of the compounds in commercial preparati ons (pharmaceuticals and herbicide formulations) and in water samples, with good recoveries. (C) 1998 Elsevier Science B.V. All rights reser ved.