What was found
ON DESCENT, PASSING 18000 FT, CHECKLIST CALLED, APU STARTED & BLEED AIR TRANSFERRED TO APU. PASSING 9000 FT, BEGAN TO SMELL A VINEGAR ODOR. ODOR BECAME WORSE, ASKED CABIN CREW TO SEE WHERE IT WAS COMING FROM. SOURCE UNVERIFIED. AS PRECAUTION, TURNED OFF CABIN AC & DC POWER. ENG BLEED AIR RE-SELECTED & APU OFF. DONNED OXY MASKS. ACFT RETAINED VINEGAR ODOR FROM CARGO TO COCKPIT AFTER LANDING. MAINT INSP LT & RT E/E RACKS, WINDSHIELD TERMINALS, UNDER GLARE SHIELD, VISUAL INSP WIRES & E/E UNITS, NO DISCREPANCIES FOUND. ACFT SYS OPS CHECKS PERFORMED & PNEUMATIC SYS CHECKED. NO DISCREPANCIES FOUND. PRIOR T/O DEPART, ACFT DE-ICED. SUSPECT DE-ICING FLUID INTRODUCED INTO APU INTAKE. MAINT FLT TO BE PERFORMED . OPEN