DETERMINATION OF COPPER AT NG ML-1 LEVEL IN SURFACE WATER USING THE ELECTROPHILIC SUBSTITUTION REACTION BETWEEN CU(II) AND 3-(3-SULFOPHENYLAZO)-6-(4-CHLORO-2-PHOSPONOPHEN-YLAZO)-4,5-DIHYDROXYNAPHTHALENE-2,7-DISULFONIC ACID-CA(II) COMPLEX

The chromophore, 3-(3-sulfophenylazo)-6-(4-chloro-2-phosponophenylazo)-4,5-dihydroxynaphthalene-2,7-disufonic acid (MSCPA) was synthesized to complex Cu(II) and Ca(II) in aqueous solution at pH 6.47. Both the Cu(II)-MSCPA and Ca(II)-MSCPA complexes were characterized by spectral correction technique and the results have shown that complexes Cu(MSCPA)(3) and Ca(MSCPA) were formed. An interesting phenomenon was found that Cu(II) Substituted Ca(II) of the Ca(II)-MSCPA complex. The competitive substitution complexation (CRC) has been applied to the detection Of Cu (II) with good selectivity. The light-absorption ratio variation approach (LARVA), which produces all obvious increase of sensitivity, has been applied to detection of copper in trace level in surface water. The limit of detection of Cu(II) is only 2.0 ng mL(-1). The percentage of recovery of Cu(II) in samples and the experience compared with AAS both obtained satisfactory results.