Short- and Long-Term Stability of Aromatic Amines in Human Urine

Abstract

Several aromatic amines (AAs) are established by the International Agency for Research on Cancer as carcinogenic (group 1) or probable/possible carcinogens to humans (group 2A/2B). AAs can be found in mainstream and sidestream smoke from combustible tobacco products, as well as in certain environmental pollution and occupational exposure from several chemical industry sectors. Exposure to AAs can be estimated by measuring their concentrations in urine; however, information about the short-term and long-term stabilities of AAs in urine need to be characterized before conducting large-scale population studies on AA exposure and the potentially harmful effects of AA exposure. In this report, the storage stability of o-toluidine, 2,6-dimethylaniline, o-anisidine, 1-aminonaphthalene, 2-aminonaphthalene, and 4-aminobiphenyl fortified in pooled, filtered, non-smokers' urine is analyzed by isotope dilution gas chromatography-triple quadrupole mass spectrometry (ID GC-MS/MS). The six AAs were measured in urine samples stored at ~20 °C (collection temperature), 4 °C and 10 °C (short-term transit temperatures), and -20 °C and -70 °C (long-term storage temperatures) over a 10-day period. All six analytes were stable for 10 days at transit and long-term storage temperatures but showed reduced recovery at 20 °C. The instability of the target AAs at 20 °C suggests that immediate storage of freshly voided urine at low temperatures is needed to attenuate degradation. A subset of the urine samples was analyzed following a longer storage duration at -70 °C: all AAs were stable for up to 14 months at this temperature. The stability of the six AAs in urine samples can be maintained at the various temperature levels and storage times expected in a typical study set.

Keywords: aromatic amines; human urine; long-term stability; short-term stability.

Figure 1

Structures of six aromatic amines assayed for stability testing.

Figure 2

Single time-point urinary concentration of 4ABP stored at the different storage conditions for short-term stability testing. Dotted line denotes the characterized mean for a given QC pool and corresponding dashed lines denote ±2σ from the characterized mean, as listed in Table 1. The characterized mean for a given QC pool is included as the zero time-point.

Figure 3

Single time-point urinary concentration of 4ABP stored at 20 °C for short-term stability testing. Dotted line denotes the characterized mean for a given QC pool and corresponding dashed lines denote ±2σ from the characterized mean, as listed in Table 1. The characterized mean for a given QC pool is included as the zero time-point.

Figure 4

Single time-point urinary concentration of 4ABP stored at −70 °C for long-term stability testing. Dotted line denotes the characterized mean for a given QC pool and corresponding dashed lines denote ±2σ from the characterized mean, as listed in Table 1. The characterized mean for a given QC pool is included as the zero time-point.