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Chementator: A ‘litmus’ test for heavy metals

By Chemical Engineering |

Toshishige M. Suzuki and his colleagues at the Tohoku Center of National Institute of Advanced Industrial Science & Technology (AIST; Sendai, Japan; edlinks.chemengonline.com/5827-538) has developed a new analytical test strip that can quickly detect parts-per-billion (ppb) concentrations of heavy metal ions in water. Up to now, existing test strips for metal ions have not been sensitive enough to detect ppb levels, and they are not very reliable due to the leakage of test reagents, says Suzuki. The new test strips make it possible to avoid expensive analytical instruments needed for detecting low concentrations, and the associated time and costs required for routine analysis of water quality, he says. To make the test strips, a technique known as re-precipitation is used to prepare an aqueous dispersion of organic nano-particles. Common indicator dyes (those having a conjugated aromatic system) are used for detecting metal ions, such as dithizone, 1-(2-pyridylazo)-2-naphthol (PAN), and bathophenanthroline (Bathophen). The dispersion is uniformly applied to a cellulose-ester-type membrane filter. Because nano-sized indicator pigments are used, they remain bound to the membrane, even when rubbed with the fingers or when the strip…
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