1,3-Diphenylguanidine (DPG), 1,3-di-o-tolylguanidine
(DTG), and 1,2,3-triphenylguanidine (TPG) are rubber additives widely
present in the indoor environment. Nevertheless, little is known about
their human exposure. We developed a method for the quantification
of DPG, DTG, and TPG in human urine, using high-performance liquid
chromatography-tandem mass spectrometry. The quantitative analysis
of target analytes at parts-per-trillion levels in urine was optimized
using hydrophilic–lipophilic balanced solid-phase extraction
and isotopic dilution. The method limits of detection and quantification
were in the range of 0.002–0.02 and 0.005–0.05 ng/mL,
respectively. The recoveries of all analytes in human urine fortified
at 1, 5, 10, and 20 ng/mL concentrations were in the range of 75.3–111%,
with standard deviations of 0.7–4%. The repeated measurement
of similarly fortified human urine yielded intra-day and inter-day
variations of 0.47–3.90 and 0.66–3.76%, respectively.
The validated method was applied in the measurement of DPG, DTG, and
TPG in real human urine samples, which revealed the occurrence of
DPG in children’s urine samples (n= 15) with
a detection frequency of 73% and at a median concentration of 0.05
ng/mL. DPG was found in 20% of adults’ urine samples (n= 20).