Antimony leached from plastic bottles may form a novel citrate complex in citrus juices, which could affect its toxicity, report researchers in Greece.

Helle Rüsz Hansen and Spiros Pergantis at the University of Crete measured the total concentration and chemical form of antimony in fruit juices and drinking water packaged in polyethylene terephthalate (PET) bottles using two highly sensitive analytical techniques: anion exchange HPLC and ICP-MS.

Sampling commercially available orange and lemon juices in a variety of packaging, they found evidence of the presence of elevated antimony concentrations (0.28 to 1.05 ppb) in carbonated and still juices from bottles made of PET. 

Levels were highest in samples that had passed their expiry date and increased with the number of expired days, confirming that most of the antimony came directly from the container. Antimony levels were also higher in samples stored in glass bottles and aluminium cans than in cartons. Citrus juices contained both complexed Sb(V) and the more toxic Sb(III), whereas drinking water contained only uncomplexed Sb(V).

Antimony trioxide is used as a catalyst in PET manufacture and is a suspected cancer-causing agent that is listed as a priority pollutant by the EU. The World Health Organisation recommends a maximum concentration of 20 ppb for drinking water. Earlier this year William Shotyk and colleagues at the University of Heidelberg, Germany, raised questions about the chemical form of antimony when they discovered that water could be contaminated by leaching from plastic bottles.

Shotyk considers this latest work by Pergantis and Rüsz Hansen to be 'an important first step toward understanding the chemical speciation of antimony in acidic beverages'.

'The concentrations of antimony reported for beverages stored in glass, cans, and PET are comparable, raising new questions about the chemical form of antimony in these materials, the rate of antimony release from the solid to the solution, and the chemical properties of the fluid which affect the dissolution rate,' Shotyk said.

Citric acid has been reported to leach and preserve the oxidation state of antimony species found in solid materials, which may be significant in toxicity studies. According to Pergantis, 'the identification of a novel complex of antimony with citrate in juices is important because very little is currently known about the chemical behaviour of antimony in the presence of biomolecules or other organic ligands.'

'Our study is also of general interest as it reports leaching of antimony from PET containers into juices.' Pergantis continued, 'of course, as analytical techniques become more and more sensitive such occurrences will be reported at a greater frequency.'

He pointed out that 'it should be clarified, however, that despite the elevated antimony concentrations in these juices, compared to juices contained in cartons, the measured concentrations are still well below the guideline concentrations recommended for antimony in drinking water.'

Although such concentrations have previously been evaluated to be of little or no concern to human health, Pergantis and Rüsz Hansen conclude that a notable difference between antimony in drinking water and citrus beverages is the chemical form in which the antimony is present.

'At the end of the day,' said Pergantis, 'it is up to epidemiologists and toxicologists to tell us if the measured concentrations are of any concern.' 

Kathryn Lees