Chemical Oxygen Demand (COD) refers to the amount of oxidant consumed when treating water samples with potassium dichromate as an oxidant under strong acid and heating conditions, expressed in mg/L of oxygen. Chemical oxygen consumption is often used as a comprehensive indicator to evaluate the relative content of organic matter, and CODCr is one of the indicators for implementing total emission control in China.

The COD micro reflux testing method developed by Hash Company has a simple, fast, and economical operation process. The measurement results have good comparability with traditional titration methods, and can minimize the secondary pollution generated during the COD testing process. Hash Company can provide a complete analysis solution for COD micro reflux testing, including COD digesters, spectrophotometers, and supporting reagents.

Its main characteristics are:
No need to prepare reagents: Pre made reagent tubes made of chemical components required for COD testing in a certain proportion can greatly save the time required for reagent preparation;
Time saving: The entire measurement process, including steps such as water sample digestion and colorimetric determination, takes less than 3 hours;
Compact digestion device: The COD digester developed by Hash Company replaces the traditional COD reflux device and can simultaneously digest up to 25 water samples;
Low secondary pollution to the environment: Micro reflux method only requires a small amount of reagents, and carefully designed reagent tubes can prevent the volatilization of organic matter and the escape of samples, ensuring the safety of the digestion process;
● Easy to operate and learn: The illustrated operation guide facilitates the mastery of COD analysis methods in a relatively short period of time.

1. Analysis steps of COD micro reflux method:
Step 1: Preparation process of reagents and water samples. Each COD reagent tube contains 3mL of reagent. After unscrewing the bottle cap, add 2mL of water sample and tighten the cap (when using COD reagent tubes with 0-15000mg/L, only 0.2mL of water sample needs to be added).

Step 2: Dissolve the water sample
Place the COD test tube containing the water sample into the COD digester, heat and reflux at 150 ℃ for hours, and the digestion process will end. The COD digester will automatically shut down. Remove the COD reagent tube from the COD digester and cool it to room temperature.

Step 3: COD colorimetric determination
Turn on the colorimeter or spectrophotometer and enter the COD testing program. There is no need to establish a standard curve. Simply place the reagent tube into the instrument to read the COD value expressed in concentration units and record the experimental results.

2. COD analysis system
Hash Company can provide an analysis system for COD micro reflux method, including digesters, spectrophotometers, and supporting reagents.

2.1 DRB200 Dissolver
DRB200 digester is a recently developed digestion device by Hash Company, which can perform COD TOC、 The digestion process of water samples such as total nitrogen and total phosphorus can be selected within the range of 37-165 ℃ and 0-480 minutes for digestion temperature and time, respectively. According to user needs, one heating block or two independent heating blocks can be configured in the DRB200 digester (see Table 4 for product types and order numbers of the DRB200 digester).

Table 4 DRB200 Product Types and Order Numbers

Dissolver adapter (order number: 2895805): It can convert 16mm holes to 13mm holes and can be used for dissolving TNTplus pre made reagents.

Technical parameters of DRB200:
Heating speed: Heat from 20 ℃ to 150 ℃ within 10 minutes
Temperature stability: ± 2 ℃
Stored program: COD program (150 ℃, 120 minutes)
100 ℃ program (100 ℃, 30, 60, 120 minutes)
105 ℃ program (105 ℃, 30, 60, 120 minutes)
150 ℃ program (150 ℃, 30, 60, 120 minutes)
165 ℃ program (165 ℃, 30, 60, 120 minutes)
Power requirements: 100-240V, 50/60HZ
Operating environment: 10-45 ℃, maximum humidity of 90%, no condensation phenomenon

2.2 Hash series colorimeter/spectrophotometer
Hash Company provides various models of colorimeters and spectrophotometers for COD determination, including DR/5000 UV visible spectrophotometer, DR/4000V spectrophotometer, DR/2800 portable spectrophotometer, DR/890 portable colorimeter, DR/850 portable colorimeter, etc. The characteristics, technical parameters, and ordering information of various instruments can be found in the relevant sections of the spectrophotometer/colorimeter in the sample. The COD measurement range of each instrument is shown in Table 5.

Table 5 COD Measurable Range of Various Models of Spectrophotometers/Colorimeters Provided by Hash Company

Note: ● indicates that COD measurement can be performed within this range.

2.3 Hash COD prefabricated reagent tube
Hash Company provides four types of COD pre made reagent tubes with different measuring ranges. The types of reagents and order numbers are shown in Table 6.

Table 6 Types and Order Numbers of Hash COD Prefabricated Reagent Tubes