HIPPURIC and METHYL HIPPURIC ACIDS in urine (1) (2) (3) (4)
hippuric acid 2-methyl hippuric acid 3-methyl hippuric acid 4-methyl hippuric acid
C6 H5 CONHCH2 CO2 H CH3 C6 H5 CONHCH2 CO2 H CH3 C6 H5 CONHCH2 CO2 H CH3 C6 H5 CONHCH2 CO2 H
METHOD: 8301, Issue 3
CAS:
RTECS: MR815000
Issue 1: 15 February 1984 Issue 3: 15 March 2003
Exposure to toluene and xylenes
hippuric acid: N-benzoylglycine 2-methyl hippuric acid: N-(o-Toluoyl) glycine 3-methyl hippuric acid: N-(m-Toluoyl) glycine 4-methyl hippuric acid: N-(p-Toluoyl) glycine
SAMPLING SPECIMENS:
495-69-2 42013-20-7 27115-49-7 27115-50-7
EVALUATION: PARTIAL
BIOLOGICAL INDICATOR OF: SYNONYMS: (1) (2) (3) (4)
FW: 179.18 193.20 193.20 193.20
8301
1. Pre-shift urine 2. End of shift urine after 2 days exposure
VOLUME:
Complete spot void
PRESERVATIVE:
A few crystals of thymol; store @ 4o C
SHIPMENT:
Pack in styrofoam shipper with bagged refrigerant, ship overnight
MEASUREMENT TECHNIQUE:
HPLC-UV DETECTION
ANALYTES:
(1) hippuric acid (2) 2-methyl hippuric acid (3) 3- & 4-methyl hippuric acids
EXTRACTANT:
Ethyl acetate
INJECTION VOLUME: 10 :L
SAMPLE STABILITY: CONTROLS:
WAVELENGTH:
254 nm
COLUMN:
Reverse phase (C18), run at 37o C
MOBILE PHASE:
84/16/0.025% (v / v / v) water / acetonitrile / glacial acetic acid; 1.5 mL/min
CALIBRATION:
Synthetic urine solutions of analyte.
RANGE:
10.0 to 1000 µg/mL.
ESTIMATED LOD:
(1) 4 µg/mL (2) 5 µg/mL (3) 6 µg/mL NOTE: See Method Evalution
PRECISION ( þ r ):
(1) 0.020 (see Table 1) (2) 0.015 (see Table 1) (3) 0.011 (see Table 1)
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]. INTERFERENCES: None known; however, para- and meta- isomers elute together in this system. There are other sources of hippuric acid such as food preservatives, ethyl-benzene, and styrene. OTHER METHODS: This is based on the method of Matsui, et al [3]. Method 8300 can be used for screening. Isotachophoresis has also been used [4]. More recent HPLC methodologies provide better resolution for these compounds [5].
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition
