Cracked COD Tubes? How to Identify & Avoid Risks

COD water quality testing is an important part of environmental monitoring, and the quality of digestion colorimetric test tubes is directly related to the accuracy of test results and the safety of operation. However, during use, the test tubes may bring potential risks due to defects in the cover, collision damage, or scratches and cracks. In order to ensure the reliability of the experiment and the safety of personnel, it is important to understand how to identify and deal with these common problems.

For the safety of your instrument and personal safety, do not use the COD digestion test tube when the following situations occur.

1. The cover is short of material, deformed and bulged, and the middle layer of the septum leaks. In this case, the cover cannot be used.

As shown in the figure, the middle layer is red, which has the risk of contaminating the reagent. Some middle layers are white and should also be observed for leakage.

Want to know more about COD Test Tube, please check this article: COD Test Tube with PP Screw Cap for Water Analysis

2. Any collision will cause the stress at the collision position of the tube to change, resulting in the tube bursting due to uneven stress during digestion or cooling.

Potential factors for collision:

(1) Collision occurred when adding samples without paying attention;

(2) The packaging of the test tube is not a soft partition, for example, some manufacturers will insert the test tube into the instrument and send it to customers;

(3) The packaging causes the tubes to collide with each other (the pore size of the foam box is too large, or it is packaged in a bag);

(4) Collision occurred during repeated use and cleaning;

(5) When putting it into the digestion instrument, it was not slowly put in and the hand was loosened in the middle;

(6) When the tubes are cooled, they are directly thrown into the water together or put into the test tube rack without slowly putting them in.

3. Scratches and cracks. It is recommended to observe with light before loading reagents and digestion.

Test tubes with slight scratches can be used. There is no obvious sense of frustration when scratching them by hand. It is not recommended to use them in the following situations.

(1) Long scratches. This is caused by friction. The length exceeds half of the entire test tube. There is obvious resistance when touching it by hand.

(2) Annular scratches. Annular scratches that exceed two-thirds of the test tube. There is obvious resistance when touching it by hand.

(3) If you want to compare colors, obvious scratches in the colorimetric area will affect the absorbance.

Please note: Do not use cracked test tubes directly, as this is very risky.