Commonly Used Sample Preservation Techniques for Laboratory Water – Table 3 (Nitrite Nitrogen, Organic Carbon, etc.)

Table of Content [Hide]

Common Water Sample Preservation Techniques

The table lists the requirements for water sample preservation techniques. The preservation time, container material selection, and application of preservation measures all depend on the components and properties of the sample. However, real-world water samples vary greatly; therefore, the requirements listed in the table are not absolute guidelines. Each analyst should verify the applicability of these requirements in their specific work, and the sample collection and preservation methods should be clearly specified when developing analytical method standards.

Furthermore, if there are incompatibilities between the analytical method to be used and the protective agent and container material, it is often necessary to take several samples from the same water body and analyze them using different preservation methods to determine the most suitable protection method and container.

Common Sample Preservation Techniques – Table 3

(This table only contains general requirements for sample preservation. Due to the complex properties of natural water and wastewater, the stability of each type of sample treated according to the following methods needs to be verified before analysis.)

1 Project to be tested		2 Container Category	3 Save method	4 Analysis location	5 Storage time	6 suggestion
A thing reason , change study and born change point Analysis	COD	G	Refrigerate in the dark at 2-5℃ and acidify with H2SO4 _{until pH}< 2-20℃ (generally not used) .	Laboratory Laboratory Laboratory	As soon as possible January	If the COD is caused by the presence of organic matter, then acidification is necessary. When the COD value is low, it is best to store the product in a glass bottle.
	BOD	G	Refrigerate in the dark at 2-5℃ and freeze at -20℃ (generally not used).	laboratory laboratory	As soon as possible in January	When the BOD value is low, it is best to use a glass container.
	Kiedada Nitrogen ammonia nitrogen	P or G P or G	Acidify with sulfuric acid (H₂SO₄) to pH < 2 and refrigerate at 2–5°C.	laboratory	ASAP	To inhibit the metabolism of nitrifying bacteria, bactericides such as allyl thiourea, mercuric chloride, or chloroform should be considered.
	Nitrate nitrogen	P or G	Acidify to pH < 2 and refrigerate at 2-5°C	laboratory	24h	Some wastewater samples cannot Preservation requires on-site analysis.
	Nitrite nitrogen	P or G	Refrigerate at 2-5℃	laboratory	ASAP
	Organic carbon	G	Acidify with H2SO4 to pH < 2 and refrigerate at 2–5°C.	laboratory laboratory	24h1 week	Testing should be conducted as soon as possible. In some cases, the freeze-drying method (-20°C) can be used. It is recommended to add the extractant used in the analytical method immediately after sampling, or to perform extraction on-site.
	Organochlorine pesticides	G	Refrigerate at 2-5℃
	Organophosphorus pesticides		Refrigerate at 2-5℃	laboratory	24h	It is recommended to add the extractant used in the analytical method immediately after sampling, or to perform extraction on-site.
	"Free" cyanide	P	The method of storage depends on the method of analysis.	laboratory	24h
	phenol	BG	Use CuSO4 to inhibit biochemical reactions and acidify with H2PO4 or adjust the pH to >12 with NaOH.	laboratory	24h	The method of storage depends on the analysis method used.