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Urine Analysis by GC/MS.

The incidence of urine analysis has substantially increased in the contemporary analytical laboratory. It
has been found very useful in toxicology studies, as a diagnostic tool, in pollution monitoring, and for
forensic purposes. Some examples of the use of GC/MS in urine analysis will be given here, but it
should be pointed out that new areas of application are being continuously reported in the literature.

4,4'-Methylenebis(2-chloroaniline) (MBOAC) is commercially important and is used in the polymer
industry to cure urethane elastomers and epoxy-resins. It is a reported carcinogen and therefore
exposure to the material is carefully controlled. One of the methods of monitoring exposure is to
determine the level of MBOAC in urine. Jedrzejczak and Gaind [17] developed an extraction procedure
followed by a GC/MS analysis to measure trace amounts of MBOAC in urine.

The procedure was based on the hydrolysis of MBOCA conjugates followed by solvent extraction after
adding deuterium labeled benzidined as an internal standard. To 5 ml of urine was added 0.2 ml of the
8
standard and 2 ml of 1M phosphate buffer (pH=10). The mixture was heated at 80°C for 90 minutes to
hydrolyze the conjugated MBOCA. 3 ml of ethyl acetate and 1 ml of 2.5% w/w aqueous ammonia were
then added to the cooled mixture. The mixture was vigorously shaken with 50 µl of pentafluoro-
propionic anhydride for 2 minutes and evaporated to dryness. The residue was then dissolved in 1 ml of
ethyl acetate and a 1 µl taken for analysis. The separation was carried out on a 30 m capillary column
320 µm I.D. with a stationary phase film thickness of 1 µm. The column was directly coupled to the ion
source of a Hewlett-Packard mass spectrometer which was operated in the negative ion chemical
ionization mode using methane as the reagent gas. An example of the single ion monitoring of a sample
is shown in figure 5.18.

The deuterated standard furnished an ion at m/z=464, whereas the MBOCA produced a major ion at
m/z = 538. The peak at 538, shown in figure 5.18, is from a sample that contained 125 µg of MBOCA
per liter.