Page:NIOSH Manual of Analytical Methods - 8301.pdf/1

 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