Page:NIOSH Manual of Analytical Methods - 8300.pdf/1

 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