Iodine in the Air - Chromatography Investigates

Iodine is an essential ingredient for life on Earth. Many mammals - including humans - and plants require iodine to function. Iodine is known as a halogen - and is found in the periodic table in the same group as chlorine and bromine. They are highly reactive elements and like to form salts with alkaline metals. In fact, halogen means salt producer.

Although there are many methods to analyse iodine compounds formation in soils and rocks, there is relatively little research regarding iodine speciation in air. A recent paper in the journal Atmospheric Chemistry and Physics - Iodine speciation and size distribution in ambient aerosols - reports on work by Chinese scientists that helps to rectify this shortcoming.

Iodine - your thyroid loves it

Iodine is one of the many micronutrients or ingredients that we all need. It is an essential element that is used to make the hormones that control our metabolism. Our thyroid gland - located just below the larynx - takes iodine and combines it with the amino acid tyrosine to make the hormones thyroxine (T4) and triiodothyronine (T3). T3 and T4 are released into our bloodstream where they are transported around our bodies to help control our metabolism. The cells in the thyroid are the only cells in our bodies to absorb iodine and every cell in our body needs T3 and T4 for metabolism regulation.

Iodine all around us, in sea, soil and air

The researchers report how iodine speciation has been reported and measured in water supplies, rain, soil and animal tissues. But previous aerosol studies have shown only three iodine species, iodine ions, iodate ions and total soluble iodine (SOI), and their distribution and concentrations have varied with location.

Most models assume that iodate ions make up most of the iodine concentration in the atmosphere. It is thought that SOI is formed by the reaction of aerosol organic matter with hypoiodous acid. Organic iodine compounds are more toxic to humans than either of the other species and their speciation is described as the most significant knowledge gap in aerosol iodine chemistry. So, the studying of iodine speciation can only increase our understanding of the formation and chemistry of iodine species.

Sampling aerosols by the coast

The researchers took samples over a five-month period near a coastal area where algae farming takes place. It is thought that there is a link between the farming and iodine speciation. The aerosols were analysed using liquid chromatography-mass spectrometry. The use of chromatography to analyse environmental samples is discussed in the article, Detection of molecular markers in aquatic sediments by ion profiles obtained by GC/MS system.

The researchers report that there was a correlation between algae farming and iodine formation during the sampling period. They also reported that the methods they developed could be used to accurately measure iodine species and formation in aerosols. Understanding more about the chemistry of iodine aerosols can help us understand more about our atmosphere.