Analytical Method: ADMI Color Measurement for Prove

Photometric determination using the indophenol blue method after extraction with calcium chloride solution

Materials and reagents:
Cat.No. 173016 Spectroquant^® VIS Spectrophotometer Prove 100 or
Cat.No. 173017 Spectroquant^® UV/VIS Spectrophotometer Prove 300 or
Cat.No. 173018 Spectroquant^® UV/VIS Spectrophotometer Prove 600
Cat.No. 114946 Rectangular cells 10 mm and/or
Cat.No. 114944 Rectangular cells 50 mm
Cat.No. 116754 Water for analysis
Cat.No. 100716 Sulfuric acid 25 % for analysis
Cat.No. 105588 Sodium hydroxide solution min. 10 % for analysis
Cat.No. 100246 Platinum Cobalt Color Reference Solution (HAZEN 500) with 500 mgl/l Pt
Membrane filter, max. pore size 0.45 µm

Method:
Spectrophotometric measurement in the range 400 – 700 nm at 10-nm intervals. Evaluation acc. to Allen (see the literature¹⁾).

Measuring range:
10 – 500 units Pt-Co in the 10-mm rectangular cell (method No. 2517)
2.0 – 100.0 units Pt-Co in the 50-mm rectangular cell (method No. 2518)

Working instructions:

Sample preparation:
Filter turbid sample solutions over a membrane filter.
To do this, first pre-rinse the membrane filter with approx. 50 ml of water GR, subsequently re-rinse with approx. 50 ml of sample, and discard the filtrate.
Filter a further 50 ml of sample over the pre-rinsed membrane filter and collect the filtrate for analysis.

Zeroing the photometer:
For each measurement series, a zero adjustment is required.
It is recommended to use the same cell for zero adjustment and for sample measurement.
The zeroing procedure for the measurement series is automatically prompted by the instrument.
For zero adjustment fill the corresponding rectangular cell with water for analysis.
After prompting, place the filled rectangular cell in the cell compartment, the zero adjustment is executed automatically.
Confirm the implementation of zero adjustment with "OK".
The zero value is valid for the entire measurement series.

Measurement at the original pH:
Select method 2517 or method 2518 from method list.
Prior to the measurement of the first sample the system automatically prompts a zero adjustment (procedure see "Zeroing the photometer").

Transfer the sample solution into the corresponding rectangular cell and place the rectangular cell into the cell compartment, the measurement is performed automatically.
Confirm measurement with "OK".
The measurement result is shown in the display.

Press "START" to start the measurement procedure for the next sample. The system does not prompt a repeat of the zero adjustment.

Measurement at pH 7.0:
Check the pH of the sample and adjust, if necessary, to pH 7.0 with sulfuric acid or sodium hydroxide solution. Select method 2517 or method 2518 from method list.
Prior to the measurement of the first sample the system automatically prompts a zero adjustment (procedure see "Zeroing the photometer").

Transfer the sample solution pH 7.0 into the corresponding rectangular cell and place the rectangular cell into the cell compartment, the measurement is performed automatically.
Confirm measurement with "OK".
The measurement result is shown in the display.

Press "START" to start the measurement procedure for the next sample. The system does not prompt a repeat of the zero adjustment.

Procedure control:
To check the method Platinum Cobalt Color Reference Solution (HAZEN 500) with 500 mgl/l Pt, Cat. No. 100246, can be used. This original concentration must be diluted to a value in the middle of the measurement range using water for analysis or distilled water and analyze.

Adjustment:
The ADMI factor of 1400 used for determining the measurement result can be adjusted by the user. The corrected ADMI factor is calculated as follows:

ADMI factor_corrected = ADMI factor x (nominal value process control / measurement result process control)

To change the ADMI factor select method 2517 or method 2518 from "Methods".
Press "Settings" and select "Factors" from the list.

Tap on the entry field "ADMI Factor", enter the corrected ADMI factor, and confirm with "OK".

Literature:
1. Allen, W.; Prescott, W. B.; Derby, R. E.; Garland, C. E.; Peret, J. M.; Saltzman, M.; 1973. Determination of color of water and wastewater by means of ADMI color values. Proc. 28th Ind. Waste Conf., Purdue Univ., Eng. Ext. Ser. No. 142:661ff
2. Standard Methods for the Examination of Water and Wastewater, 21^th Edition, APHA 2120 F
3. McClaren; The Adams-Nickerson Color Difference Formula; J. of the Society of Dyers and Columnists; 86, 354ff
4. Bridgeman; Inversion of the Munsell value equation; J. of Optical Society of America; 1953; 499ff