True or Filtered Color is determined by filtering samples through a 0.45 micron filter before analyzing the sample in a spectrophotometer. When running large amounts of samples on automated systems, this filtering can become time consuming and heavy on resource usage. An alternative method (Bennett and Drikas 1993) for determining true color without filtering has been established, through the use of a turbidity meter to quantify the contribution from solids present in the sample. MANTECH can easily combine automated Turbidity and Color analysis on one system, determined from one sample, to provide True Color results without the need to filter.
The determination is as follows:
C - Color result (Cu)
A - sample absorbance (Abs)
l - cell path length (cm)
E - scattering coefficient estimated at 0.00264 NTU-1 cm-1
t - turbidity (NTU)
ϵ - color absorptivity coefficient determined through calibration (Cu-1 cm-1)