MACHEREY-NAGEL 985022 NANOCOLOR COD 60 Tube Test Instructions

: June 3, 2024
: MACHEREY-NAGEL

Table of Contents

Overview
Method
Interferences
Reagents and accessories
Quality control
Procedure
References
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Download This Manual (PDF format)

NANOCOLOR®COD 60
REF: 985022
Test Instructions

Overview

The test is suitable for the photometric determination of the chemical oxygen demand (COD). The test is in accordance with DIN ISO 15705–H45 and is equivalent to the methods EPA 410.4, APHA 5220D and DIN 38409–H41-1.
The test is suitable for water, surface water, ground and drinking water and wastewater.

Measuring range: 5–60 mg/L O2 (method 0221)
Number of tests: 20
Wavelength for photometric determination: 345 / 365 nm
Shelf life: 12 months
Reaction time: 120 minutes
Storage temperature: 2–8 °C
Storage conditions: protected from sunlight, upright.

Method

The organic compounds of a sample are oxidized by heating the sample in a mixture of sulphuric acid and potassium dichromate. The chemical oxygen demand (COD) of a ater sample is the concentration of oxygen that is equivalent to the amount of potassium dichromate consumed.
The change in the potassium dichromate concentration is determined via the change in absorbance after digestion.

Interferences

The foreign materials shown here do not interfere with the test up to the indicated concentrations (in mg/L). The cumulative effect of different interfering ions has not been ested. Data in mg/L: • Cl – 1500
Important: For samples in which the chloride content is high, shake the tube to suspend the precipitate prior to adding the sample. If the chloride content is greater than 500 mg/L, you must dilute the sample or use a chloride masking agent (REF 918911). Once it has reacted in the heating block, the solution must not be cloudy; turbidity can esult in suppressed COD values. The use of precipitated mercury sulphate will allow the turbidity to settle.
This method is not suitable for analyzing seawater.
Turbidity leads to lower measured values.

Reagents and accessories

Contents of reagents set:

20 test tubes R0
Required devices:
MACHEREY-NAGEL photometer
MACHEREY-NAGEL heating block
Digital piston pipette 1–5 mL (REF 916909) with pipette tips
(REF 916916)
Safety bottle for shaking COD tubes (REF 91637)

Standards

NANOCONTROL COD 60 (REF 92522)
NANOCONTROL Multistandard Sewage outflow 2 (REF 925010) www.mn-net.com

Sampling and preparation
See DIN EN ISO 5667-3-A 21.

Quality control

The measurement of a blank value and a standard is recommended before every measuring series as quality control measure.
Quality data: The following data were determined during production according to ISO 8466-1 and DIN 38402-A51:

Number of LOTs: 50
Standard deviation of the method: ± 0.97 mg/L O2
Coefficient of variation of the process: ± 2.95 %
Confidence interval: ± 2.24 mg/L O2 Specified data for procedure:
Sensitivity (absorbance of 0.010 A corresponds to): 0.39 mg/L O2
Accuracy of a measurement value: ± 3.87 mg/L O2 LOT-specific certificates are available at www.mn‑net.com.

Procedure

Open round cell and hold slightly tilted
Pipette 2 mL of sample into test tube
Seal test tube and shake vigorously (use safety bottle, cuvette will become hot!).
Heat for 2 h at 148 °C or for 30 min at 160 °C
Take the tube from the heating block
Shake again after 10 min. while still warm
Cool to room temperature
Clean outside of test tube
Measure

Notes
Test a sample of COD-free water (REF 918993) to generate a blank value for the reagent.
The solution remains cloudy until heated.
When using a standard, the measured value is constant over a period of min. 30 min.
Correction value e. g. for colored or turbid samples possible (see photometer manual).
When using other photometers, make sure measurements are possible in test tubes (16 mm OD) and calibrate the method.
Information regarding safety can be found on the box’ label and in the safety data sheet. You can download the SDS from www.mn‑net.com/SDS.
10/2019

MACHEREY-NAGEL GmbH & Co. KG · Neumann-Neander-Str. 6–8 · 52355 Düren · Germany

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