Spectroquant® ADMI Color Measurement

Description

Method: Spectrophotometric, analogous APHA 2120F (ADMI weighted-Ordinate Spectrophotometric Method)

Introduction
The ADMI color scale originates from the “American Dye Manufacturers Institute” (ADMI) and is defined, just like the Pt/Co color scale, by the color of hexachloroplatinate solutions.
The ADMI value is determined by measuring the transmittances (transmittances) in the wavelength spectrum between 400 and 700 nm and subsequent calculation according to Allen (see literature reference1). Since the last step in the calculation of the ADMI value is based on the ΔE value of the sample relative to water, this method can also be used to determine ADMI values for colors that lie beyond the yellow-orange range of the Pt/Co scale.
The method is analogous to the APHA 2120 F standard (see literature reference2).

Experimental
This Application Note describes the determination of the ADMI color value in liquid samples.
The methods are preprogrammed on the corresponding Spectroquant® photometers.

Method
The ADMI value is determined by measuring the transmittances (transmittances) in the wavelength spectrum
between 400 and 700 nm and subsequent calculation according to Allen (see literature reference1).
Measuring range
method No. 2518 2.0 – 100.0 units Pt-Co in the 50-mm rectangular cell (linear method)
method No. 2517 10 – 600 units Pt-Co in the 10-mm rectangular cell (linear method)
method No. 2516 10 – 1000 units Pt-Co in the 10-mm rectangular cell (nonlinear method)

Sample material
Clear liquid samples
Turbid liquid samples after filtration

Reagents, Instruments and Materials:

Reagents
Water for analysis or distilled water

Only necessary if pH adjustment is needed:
ZA. 002.133 Sulfuric acid 25 % for analysis
Sodium hydroxide solution min. 10 % for analysis

Only necessary for checking the method:
ZA.002.134 Platinum Cobalt Color Reference Solution (HAZEN 500) with 500 mgl/l Pt

Instruments
For the cobalt measurement one of the following Spectroquant® photometers is necessary:
Spectroquant® VIS Spectrophotometer Prove 100 or
Spectroquant® UV/VIS Spectrophotometer Prove 300 or
Spectroquant® UV/VIS Spectrophotometer Prove 600

Software for data maintenance
The Spectroquant® Prove Connect to LIMS software package provides an easy way to transfer your data into
a preexisting LIMS system. This software can be purchased; contact our sales team (sales@idealmedical.co.za)

Materials
Rectangular cells 10 mm and/or
Rectangular cells 50 mm

Only necessary for turbid solutions
Membrane filter, max. pore size 0.45 µm

Analytical approach
Sample preparation
• Filter turbid sample solutions over a membrane filter. To do this, pre-rinse the membrane filter with approx. 50 ml of water for analysis, then re-rinse with approx. 50 ml of the sample solution and discard the filtrate. Filter a further 50 ml of the sample solution over the pre-rinsed membrane filter and use the filtrate for the analysis.

• Determination at the original pH: Filter turbid samples if necessary.
• Determination at pH 7.0: Filter turbid samples if necessary. Check the pH of the sample and, if necessary, adjust to pH 7.0 with sulfuric acid or sodium hydroxide solution.

Measurement
• Open the methods list () and select Method No. 2516 resp. 2517 or 2518 „ADMI”.
• Zeroing the photometer
The photometer must be zeroed prior to each new measurement series. The zero-adjustment procedure for the measurement series is automatically prompted by the instrument.
It is advisable to zero the photometer using the same cell as the one used for the measurement sample or else a cell with identical optical characteristics and an identical absorption (matched pair).

For the zero adjustment fill a corresponding rectangular cell with water for analysis. After prompting, insert the filled rectangular cell into the cell compartment. The zero adjustment is performed automatically.
Confirm the performance of the zero-adjustment procedure by clicking on . The zero adjustment is valid for the entire measurement series.

• Measuring the sample solution
Fill the sample solution into a corresponding rectangular cell and insert the cell into the cell compartment. The measurement is performed automatically. Confirm the measurement by clicking on .
• Read off the result in mg/l from the display.
• Click to start the measurement procedure for the next sample. A renewed zero adjustment
is not necessary.
Data transfer Prove spectrophotometers
After measurement transfer the values measured on the Prove spectrophotometer using Prove Connect to LIMS.