Gelatine was extracted from the (liquid) test materials by heat-precipitating at 80 C for 10 min, collecting the supernatant by centrifugation, adjusting the pH to 4.4 with acetic acid, centrifuging at 4000 g for 5 min, concentrating using a 3000 Dalton molecular weight cut off filter (Vivaspin™) and eluting by solid phase extraction using specialist C18 columns (Orosep column, Orochem Technologies Inc., Naperville, IL, USA) in 5% acetonitrile containing 0.1% formic acid.