Starch

Starch exists as a carbohydrate in nature, derived from fruits, grain, and vegetables. It is utilized by the body once it has been broken down to glucose, a sugar which is consumed by cell metabolism. The biggest source of starch is corn, followed by potatoes, tapioca and wheat. Starch recently has also been used to produce biodegradable plastics for environmental purposes. Starch production worldwide has been estimated at more than 50 million metric tons, and growing.

In the analytical chemistry lab starch is an indicator mainly used for Iodometry, although it is suitable for other assays such as iron assay, etc. There are many forms of starch (corn, potato, etc.), but basically they react the same way when used to detect an endpoint – they exhibit the same very dark iodide complex, then become clear at endpoint.

The starch can interfere with titration results if added early in the titration (containing an excess of iodide salt) by binding with the iodide and producing an incorrect results – so it is best to add it near the expected endpoint, in order to minimize this interference affect.

The starch indicator solution is not an easy one to prepare, as it requires boiling temperature and stirring. In addition, it typically has an opaque appearance as opposed to “water white”. In the past, it was common to use mercuric iodide as a preservative, but this is not commonly used anymore. Exaxol’s proprietary process produces Starch Indicators which are nearly water white, and uses a nontoxic preservative for the wet chemistry laboratory. Our starch solutions/indicators are prepared in our ISO 17025 Accredited laboratory.