DETERMINATION OF NEUTRAL AND ACIDIC SUGARS IN SOIL BY CAPILLARY GAS-LIQUID-CHROMATOGRAPHY AFTER TRIFLUOROACETIC-ACID HYDROLYSIS

A new method for the simultaneous, quantitative determination of neutr al and acidic sugars liberated from non-cellulosic soil carbohydrates is described. A single hydrolytic step with 4 M trifluoroacetic acid ( TFA) at 105 degrees C for 4 h is suggested to be more effective in rel easing sugar monomers from soil than other recommended hydrolysis proc edures (2.5 M H2SO4 reflux for 20 min followed by 12 M H2SO4 for total sugar hydrolysis; 1 M HCl for 5 h at 105 degrees C or for 7 h at 100 degrees C: 4 M TFA at 125 degrees C for 1 h or 2 M TFA at 105 degrees C for 2 h). Different materials were tested for purification (cation e xchange resin, activated carbon, C-18, XAD-4, XAD-7). and the combinat ion of the cation exchange resin and of XAD-7 is recommended. Analysis of purified monomers involved separation of O-methyloxime-trimethylsi lyl derivatives by capillary gas-liquid chromatography in 21 min. Resu lts were compared with those obtained from spiked soil samples, result ing in a high recovery of standard mixtures (70-109% for individual su gars) processed in the way proposed here. The method was sensitive and characterized by simple, accurate and rapid work-up and, therefore, i s suitable for routine use. (C) 1997 Elsevier Science Ltd.