Impurity Analysis Methods in Ammonium Metatungstate

Impurity analysis in AMT is crucial for quality control, especially in high-purity applications such as catalysts and electronic materials. Common impurities in AMT include molybdenum (Mo), iron (Fe), sodium (Na), potassium (K), silicon (Si), and other metallic or non-metallic elements. These impurities may originate from raw materials, production processes, or equipment contamination.

Common Analysis Methods

1. Inductively Coupled Plasma Mass Spectrometry (ICP-MS):
o Capable of detecting multiple trace elements simultaneously with extremely high sensitivity (down to ppb level).
o Particularly suitable for trace impurity analysis in high-purity AMT.
o Example: Catalyst-grade AMT requires Mo content to be below 0.01%.

2. Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES):
o Suitable for detecting metallic impurities at ppm-level concentrations.
o Provides fast and accurate quantification of Fe, Na, K, and other elements.

3. Atomic Absorption Spectroscopy (AAS):
o Used for precise analysis of specific elements such as Fe and Na.
o Samples are atomized using a flame or graphite furnace, and absorption at characteristic wavelengths is measured.

4. X-ray Fluorescence Spectroscopy (XRF):
o A non-destructive technique suitable for routine impurity analysis of solid AMT samples.
o Effective for detecting major and minor elemental impurities.

5. Ion Chromatography (IC):
o Used for analyzing water-soluble anionic impurities, such as chloride, sulfate, and nitrate.
o Offers high sensitivity and selectivity, allowing precise monitoring of dissolved contaminants.

6. Thermogravimetric Analysis (TGA):
o Measures changes in sample mass upon heating to detect volatile impurities or residual organic compounds.

7. Ultraviolet-Visible Spectrophotometry (UV-Vis):
o Allows quantitative analysis based on the absorption spectrum characteristics of specific impurities.