National Institute for Occupational Safety and Health

“ Stable 30 days @ 4o C Collect samples from unexposed, matched population.
APPLICABILITY: Hippuric acid and methyl hippuric acids are the principal metabolites of toluene and xylene, respectively. An occupational exposure to either of these organic solvents may be monitored by following the pattern of excretion of these metabolites in urine. Due to overlap in the range of hippuric acid concentration between exposed workers and non-exposed workers, monitoring urinary hippuric acid concentrations are better suited for groups of workers than for individuals [2] . ”

“ Meth yl hippuric acids are not found in non-exposed humans. 2. Th e T hres hold Lim it Value (TL V® ) [9] for u rine sam ples collected at the en d of a work shift is 1.6 g/g creatinine for hippuric acid a nd 1 .5 g/g crea tinine for m ethyl hipp uric acids.
NIOSH Manual of Analytical Methods (NMAM) , Fourth Edition HIPPURIC and METHYL HIPPURIC ACIDS in urine: METHOD 8301, Issue 3, dated 15 March 2003 - page 4 of 5 EVALUATION OF METHOD: LOD/LOQ studies were p erform ed u sing standard s in synthetic u rine, standards in pooled urine, and standards in water. ”

“ HPL C system consistin g of sam ple injector, pump, ultraviolet detector at 254 nm, strip chart recorder, integrator, RP C18 column, and column heater (Supelco Discovery #322 201-01 or eq uivalent) . 4. Heated water bath purged by nitrogen blow-down apparatus. 5. Centrifuge. 6. Analytical balance. 7. ”