CONCENTRATION OF PENTACHLOROPHENOL WITH M IXED HYDROXIDE OF IRON(III)AND MAGNESIUM AS A MEANS OF PRECONCENTRATION FOR THE SPECTROPHOTOMETRIC DETERMINATION

Pentachlorophenol (PCP) was coprecipitated with a mixed hydroxide of i ron(III) and magnesium at about pH 12 and extracted with 1-pentanol. A 3 ml portion of 1 mol . dm(-3) iron(III) chloride solution and 6 ml o f 2 mol . dm(-3) magnesium chloride solution were added to a 500 mi of sample solution and pH was adjusted to 12 with sodium hydroxide to pr ecipitate the mixed hydroxide of iron(III) and magnesium with which PC P was coprecipitated. The suspention was stirred for 60 min. After cen trifugal separation, the precipitate was dissolved with 4 mi of 5 mol . dm(-3) sulfuric acid, and pH of the reddish solution was adjusted wi th sulfuric acid to the range from 1 to 2. The total volume of the red dish solution was made up to 40 mi with distilled water and was extrac ted with 5 mi of 1-pentanol. A small amount of sulfuric acid was added into the extract. The absorbance of extract was measured at 290 nm ag ainst 1-pentanol. PCP as low as 50 ppb could be determined. NH4+, Ca2, CO32-, SO42-, BO3-, NO2-, NO3-, F-, SiO42- and PO43- as much as 1 x 10(-3) mol . dm(-3) did not interfered.