Arsenic III vs Total Arsenic: What is the Difference?

Arsenic III and arsenic V are two different oxidation states of the chemical element arsenic.

Arsenic III, also known as arsenite, is the trivalent form of arsenic and has a charge of +3. It is highly soluble in water and can easily dissolve in groundwater, making it a major concern in drinking water. Inorganic arsenic III compounds are highly toxic and have been linked to various health problems such as skin lesions, cardiovascular disease, and some types of cancer.

On the other hand, arsenic V, also known as arsenate, is the pentavalent form of arsenic and has a charge of +5. It is less soluble in water than arsenite and is typically found in soils and rocks. Arsenate is not as toxic as arsenite, but it can still pose a risk to human health through long-term exposure.

In water, arsenic normally occurs in the oxidation states III and V. Therefore, a total arsenic measurement is a combination of the concentration of arsenic III and arsenic V.

Measuring both arsenic III and total arsenic is important for several reasons:


Both forms of arsenic can have harmful effects on human health. Measuring total arsenic allows for a more comprehensive assessment of the potential health risks associated with arsenic exposure in drinking water.

Source Identification

Knowing the ratio of arsenic III in the total arsenic measurement can provide important information about the source of arsenic contamination in drinking water. For example, high levels of arsenic III may indicate contamination from industrial sources, while low arsenic III but high total arsenic levels may indicate agricultural runoff.

Treatment Options

Different treatment options may be more effective at removing one form of arsenic compared to the other. By measuring both arsenic III and total arsenic, it is possible to determine the most effective treatment options for removing arsenic from drinking water.

Compliance with Regulations

In many countries, drinking water regulations specify maximum permissible levels for both arsenic III and total arsenic. Measuring both forms allows water utilities to ensure that they are in compliance with these regulations.

By measuring both forms of arsenic, a more complete picture of the arsenic content in drinking water can be obtained. This information is critical in determining the appropriate course of action to reduce exposure to arsenic and ensure the safety of the drinking water.


Palintest’s Kemio Solution

Our Kemio instrument uses a sophisticated electrochemical technique to test for heavy metals in water. The Kemio arsenic sensor range includes sensors to test for both arsenic III and total arsenic which measure in the range of 2 to 250 μg/L.

The test doesn’t require any specialist training, and the arsenic sensors provide users with a safer testing method than other common field-testing procedures, which use toxic chemicals such as mercury bromide in the testing process. Tests can be performed on-site in minutes, meaning that a user can test for both arsenic III and total arsenic across more locations in a single day.

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