7;his work shows that diffuse reflecrance measurements, usingfiber optical
devices, can give rapid quam’tm‘ve results for application with spot tests
determination where little sample manipulation is a desirable feature. The
experiments were performed with a Hewlen Packard diode array
spectrophotometer HP8452A and a Labsphere RSA-HP-84 refZectance accessory.
The quantitative rtflectance measurements of different complexes such as Fe (III)
with thiocyanate, Cr (W) with dipheylcarbazide and Ni (II) with
dimethylglvoxime could be obtained by forming rhe complexes on filter paper.
Calibration curves were obtained for each metal by plomng the optical density
of the reflectance signal (Ad vs. the log of the molldm’ concentration, from
1.5XIO’to 3.6~10~rnolldm‘for Fe (III),from 8.00xIO-’to .?.&l~I0~mol/dm‘
for Cr W) andfrom 1.00~ 10’ to 8.00~ 102 mol/dm)for Ni (II), with correlation
co@cienrs of 0.9986 for Fe (III), 0.9878 for Cr (Vl) and 0.9892 for Ni (II). 7;he
results obtained show that it is possible to perform quantitative spot-test analvsis
using reflectance measurements in the lisible region of the spectrum.