Heavy metal detection has long been a challenging task in water quality analysis. Actual water samples often contain multiple heavy metal ions. When testing for one or several target heavy metal ions, interference’s are likely to occur. This article briefly introduces how to avoid interference’s when detecting heavy metals in water, and the analysis is divided into the following aspects:
- Eliminate interference by adjusting the pH value of water samples
In practical water quality analysis, adjusting the pH of water samples can reduce interference’s during heavy metal testing. The pH can be controlled according to the acid effect curve and kept within the allowable range for target heavy metal ions. This prevents target heavy metal ions from forming complexes and avoids interference. It should be noted that this method is not suitable if interfering ions form complexes with similar or higher stability than target ions, and alternative approaches should be adopted.
- Reduce interference via complex masking treatment.
Masking technology refers to adding specific reagents to react with interfering ions and lower their effective concentration. For example, the ch-elates formed by ferric ions and aluminum ions with EDTA have higher stability than those formed by magnesium and calcium ions. If these four ions coexist in water samples, ferric ions and aluminum ions need to be treated first before detection. It is necessary to verify whether the added masking reagents will affect the target ions to be measured. The heavy metal online monitor can obtain more reliable data after proper masking pretreatment.
- Remove interference by precipitation masking method.
This method works by adding reagents to make interfering ions form precipitates and reduce their concentration. The precipitates generated should have low water solubility, good stability, and form colorless, compact crystalline precipitates. Otherwise, the subsequent test results will be affected.
- Eliminate interference through red-oxreactions.
Red-ox reactions can change the valence state of interfering ions to achieve the purpose of interference removal.
With the continuous development of industry and agriculture in China, water pollution remains a concern. Relevant authorities have formulated requirements to regulate wastewater discharge from enterprises. Enterprises adopt water quality analyzers and heavy metal online monitors to track water quality changes, ensuring safe reuse and discharge of wastewater.
