20 M AT 10 % ON CHRONOSORB WHP 80 TO 100 MESH .
6 . MICROSYRINGES , 10 UL .
23.4 . METHOD
PUT TWO LITRES OF WINE INTO THE DISTILLATION FLASK , INTRODUCE A FEW MILLILITRES OF ETHANOL INTO THE TWO COLLECTING TUBES SO THAT THE POROUS PARTS OF THE GAS DISPERSION RODS ARE COMPLETELY IMMERSED . COOL THE TWO TUBES EXTERNALLY WITH THE FREEZING MIXTURE . CONNECT THE FLASK TO THE COLLECTING TUBES AND BEGIN TO FLUSH THE APPARATUS WITH NITROGEN AT A RATE OF THREE LITRES PER HOUR . HEAT THE WINE TO 80 C WITH THE HEATING MANTLE , DISTIL AND COLLECT 40 TO 50 ML OF DISTILLATE .
PREPARATION OF THE GAS CHROMATOGRAPH
IT IS RECOMMENDED THAT THE FOLLOWING CONDITIONS ARE USED :
_ INJECTOR TEMPERATURE : 200 C ,
_ COLUMN TEMPERATURE : 130 C ,
_ HELIUM GAS CARRIER FLOW-RATE : 20 ML PER MINUTE .
INTRODUCE WITH A MICROSYRINGE A VOLUME OF THE STANDARD SOLUTION SUCH THAT THE PEAK CORRESPONDING TO THE ALLYL ISOTHIOCYANATE CAN BE EASILY IDENTIFIED ON THE GAS CHROMATOGRAM .
INTRODUCE AN ALIQUOT OF THE DISTILLATE INTO THE CHROMATOGRAPH . A PEAK WITH THE SAME RETENTION TIME AS THAT OF THE ALLYL ISOTHIOCYANATE IN THE SAMPLE .
UNDER THE CONDITIONS DESCRIBED ABOVE COMPOUNDS NATURALLY PRESENT IN THE WINE WILL NOT PRODUCE INTERFERING PEAKS ON THE CHROMATOGRAM OF THE SAMPLE SOLUTION .