DETERMINATION OF CARBOHYDRATES IN SOLUBLE (INSTANT) COFFEE BY ANION-EXCHANGE CHROMATOGRAPHY WITH PULSED AMPEROMETRIC DETECTION - SUMMARY OFCOLLABORATIVE STUDY

A collaborative study was conducted to validate a liquid chromatograph ic (LC) method for determining free and total (after acid hydrolysis) carbohydrate profile of soluble (instant) coffee. Carbohydrates were s eparated on a pellicular anion-exchange column with pure water as mobi le phase and detected by pulsed amperometry. Precisions in determining free and total carbohydrates were very similar. Average RSD(r) and RS D(R) values were 4.5 and 14.3%, respectively, for carbohydrate levels > 0.3%, with individual values ranging, respectively, from 2.2 to 4.6% and 9.9 to 24.2% for mannitol, 1.6 to 7.3% and 4.9 to 21.1% for arabi nose, 1.7 to 8.1% and 4.1 to 12.9% for galactose, 2.4 to 8.7% and 6.1 to 24.3% for glucose, 1.8 to 6.8% and 10.0 to 11.6% for sucrose, 3.7 t o 7.4% and 22.5 to 27.8% for xylose, 2.0 to 7.0% and 10.6 to 24.4% for mannose, and 2.9 to 5.2% and 15.5 to 18.4% for fructose (free form on ly). The technique's precision was considered good, taking into accoun t the usual peak integration problems always encountered in LC procedu res, the low levels of free carbohydrates, the hydrolysis step, and th e relative lack of experience of most participating laboratories. Exce pt for the pair rhamnose/arabinose, the method allows good and reprodu cible separation of carbohydrates found in soluble coffee and, therefo re, is suitable for routine analysis. The anion-exchange chromatograph ic method with pulsed amperometry for determining carbohydrates in sol uble (instant) coffee has been adopted first action by AOAC INTERNATIO NAL.