HIPPURIC ACID in urine
C6H5CONHCH2COOH
MW: 179.18
METHOD: 8300, Issue 2
8300
CAS: 495-69-2
RTECS: MR8150000
EVALUATION: PARTIAL
BIOLOGICAL INDICATOR OF:
Issue 1: 15 February 1984 Issue 2: 15 August 1994
exposure to toluene.
SYNONYMS: N-benzoylglycine
SAMPLING
MEASUREMENT
SPECIMEN:
urine, end of shift after 2 days exposure
VOLUME:
50 to 100 mL in 125-mL plastic bottle
TECHNIQUE:
VISIBLE ABSORPTION SPECTROPHOTOMETRY
ANALYTE:
complex of hippuric acid and benzenesulfonyl chloride
WAVELENGTH:
410 nm
PATH LENGTH:
1 cm
CALIBRATION:
aqueous hippuric acid standards
QUALITY CONTROLS:
frozen pooled urine; correct for creatinine content
RANGE:
0.005 to 0.5 g/L (1:5 urine dilution)
ESTIMATED LOD:
0.002 g/L
PRECISION (Sr):
0.06
ACCURACY:
not determined
PRESERVATIVE: a few crystals of thymol; keep at about 4 °C SHIPMENT:
SAMPLE STABILITY:
CONTROLS:
pack in insulated shipper with bagged refrigerant; ship by air express
stable 1 day @ 20 °C; 1 week @ 4 and 2 months @ -20 C
C;
collect pre-shift urines as well as urines from non-exposed controls
APPLICABILITY: Toluene is metabolized by the body and is excreted in the urine as hippuric acid, the glycine congugate of benzoic acid. This method is useful in screening workers exposed to toluene in the absence of xylene or styrene. The lat ter 2 compounds produce metabolites that are measured as "hippuric acid."
INTERFERENCES: In addition to positive interferences from styrene and xylene in the workplace, the ingestion of sodium benzoate in food, salicylic acid, or aspirin by the worker will produce a positive interference. A careful work history/ questionnaire is suggested.
OTHER METHODS: This method replaces P&CAM 327 [1] with minor revisions. Method 8301 (Hippuric and Methyl Hippuric Acids in urine) is a specific HPLC method and can be used in the presence of xylene, styrene, salicylic acid and aspirin . Other biological monitoring methods include measurement of blood toluene and alveolar air toluene [2].
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
