Chemical Oxygen Demand (COD)

Instrumental Kits

Range Method Kit Cat. No.
0-150 ppm (LR) USEPA-accepted* Dichromate Reactor Digestion K-7350S*
0-150 ppm (LR) USEPA-accepted* Dichromate Reactor Digestion K-7355*
0-150 ppm (LR) Mercury-free Dichromate Reactor Digestion K-7351S
0-150 ppm (LR) Mercury-free Dichromate Reactor Digestion K-7356
0-1500 ppm (HR) USEPA-accepted* Dichromate Reactor Digestion K-7360S*
0-1500 ppm (HR) USEPA-accepted* Dichromate Reactor Digestion K-7365*
0-1500 ppm (HR) Mercury-free Dichromate Reactor Digestion K-7361S
0-1500 ppm (HR) Mercury-free Dichromate Reactor Digestion K-7366
0-15,000 ppm (HR+) Not USEPA Approved* Dichromate Reactor Digestion K-7370S*
0-15,000 ppm (HR+) Not USEPA Approved* Dichromate Reactor Digestion K-7375*
0-15,000 ppm (HR+) Mercury-free Dichromate Reactor Digestion K-7371S
0-15,000 ppm (HR+) Mercury-free Dichromate Reactor Digestion K-7376

CHEMetrics offers two dichromate reactor digestion methods (USEPA-accepted and Mercury-free) for fast, easy, safe determinations of COD levels in waste water — at about 30% lower cost than competitor's vials! Our COD Reagent Vials can be used with CHEMetrics® photometers and with spectrophotometers that accept 16 mm diameter round bottom cells. Furthermore they may be used with Hach® photometers and spectrophotometers without modification of the factory calibrations.

The Dichromate Reactor Digestion Method

CHEMetrics offers two Dichromate Reactor Digestion Methods for the fast, easy and safe determinations of Low, Mid, and High Range COD in waste water: USEPA-accepted Method and Mercury-Free Method. Mercuric Sulphate is used in the former method to eliminate Chloride interferences. If negligible Chloride interference is expected, then the Mercury-Free Method is applicable, dependent on reporting requirements. Different quantity packs are available to suit requirements.

CHEMetrics leakproof, Teflon-lined (PTFE) screw capped COD vials contain a premeasured solution of Sulphuric Acid and the oxidant Potassium Dichromate. The Dichromate in the reagent gives it an orange colour, and the extent to which the colour has faded after digestion is proportionate to the amount of Dichromate used up in the oxidation process, and thus the COD value.

To perform the test, the analyst removes the screw cap from each vial, adding a premeasured quantity of sample and replacing the cap. The vials are heated for 2 hours at 150°C in a digestor block, as heat is required to accelerate the oxidation process. The vials are allowed to cool in a vial rack, after which time they can be measured using a photometer or spectrophotometer that accepts 16mm diameter cells.

CHEMetrics COD vials can be directly used in our V-2000 multi-analyte photometer, CHEMetrics' single analyte COD photometers, as well as in many Hach1 spectrophotometers and colorimeters (see pdf below for complete list). Built-in Hach COD methods and calibrations can be used without the need for a new calibration. A generic calibration equation is included within the CHEMetrics™ kit for use with other spectrophotometers. A set of 2 calibration solutions are also available to assist in generating a standard curve specific to your existing non-CHEMetrics instrument. Contact us to confirm compatibility if you already possess a spectrophotometer, photometer or colourimeter.

Click here for more information on CHEMetrics COD Reagent Vial kits and cost savings over competitors.

USEPA Methods for Analysis of Water and Wastes, Method 410.4 (1983).
APHA Standard Methods, 22nd ed., Method 5220 D-1997.
A. M. Jirka and M. J. Carter, "Micro Semi-Automated Analysis of Surface and Wastewaters for Chemical Oxygen Demand," Analytical Chemistry, Vol. 47, p.1397 (1975).
J. A. Winter, "Method Research Study 3, Demand Analysis, An Evaluation of Analytical Methods for Water and Wastewater," USEPA, 1971.
ASTM D 1252-00, Chemical Oxygen Demand (Dichromate Oxygen Demand) of Water, Test Method B.

* Contains mercury.  Dispose according to county, national or EU laws.

1 No endorsement by Hach Company is implied or intended.

USEPA Acceptance Letter for CHEMetrics COD Vials
CHEMetrics COD Test Kits Accuracy Data
Hach vs CHEMetrics COD Vial QC Performance Data Report
COD Comparison Notes - comparing CHEMetrics Vials to alternative suppliers
Hach Instruments that work with CHEMetrics COD Reagent Vials

Why COD?

The determination of Chemical Oxygen Demand (COD) is widely used in municipal and industrial laboratories to measure the overall level of organic contamination in waste water. The contamination level is determined by measuring the amount of oxidant required to oxidise the organic matter in the sample. This is equivalent to amount of oxygen that would be used up by the contaminated water during natural decay as waste water effluent.

COD Accessories

All materials for COD lab set up (with the exception of the digestor block) are available from Galgo, including COD reagent vials, COD vial rack, photometer (single or multi-analyte) and calibration standards.

Accessory Description Specification / Range
V-2000 Multi-Analyte Photometer LR, HR, HR+
A-7320 COD Photometer (Low Range) 0 - 150 ppm (LR)
A-7325 COD Photometer (High Range) 0 - 1,500 ppm (HR) &
0 - 15,000 ppm (HR+)
A-0107 Vial Rack 40 Vials
A-7301 COD Calibration Standard, 200ml 1,000 ppm
A-7310 COD Calibration Standard, 200ml 10,000 ppm

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