Groundwater containing the process chemicals sulfolane (tetrahydrothiophene 1,1-dioxide) and diisopropanolamine (DIPA) has contaminated a wetland in the vicinity of a sour-gas natural gas processing facility. Residues of the chemicals are found in wetland soil, water and vegetation. While it is known that DIPA undergoes transformation in wetlands plants, little is known regarding the degree of transformation of sulfolane. This is due in part to the lack of analytical methods suitable for the determination of transformation products of sulfolane in vegetation. Described is a new procedure, employing electrospray ionization with reverse-phase liquid chromatography mass spectrometry for the determination of the 3-hydroxysulfolane metabolite in plant tissue. The metabolite was determined using filtered water extracts of the vegetation, preconcentrated using solid-phase extraction with no further clean up or derivatization steps. Under positive ion electrospray conditions, there was preferential formation of a series of adducts with minimal (M+H)+ formation. The same was true for negative-ions, for which the molecular ion was not observed. However, the latter was more selective for crude extracts of vegetation. Quantification was performed using selected ion monitoring of the m/z 197.03 (M+61)− adduct, elucidated as the (M−1)(CN·(H2O)2)− negative-ion. Confirmations were based on comparison of the retention time and product ion scan of an authentic standard. Instrumental detection limits were attainable in the picogram range (50–100 pg injected). Successful application of the procedure is demonstrated for the determination of the metabolite in 22 samples, collected from a sour-gas contaminated wetland and a control site. For roots, shoots, berries, seeds, grasses, and leaves, the recovery was 117±5.6% r.s.d with a detection limit of 50 ng/g. In general, the technique was rugged (based on a study period of 18 months), and relatively fast (∼25 min per sample for a batch of 10 samples). For the study period, it appears that sulfolane is also transformed in the plants in a manner similar to DIPA, suggesting that degradation of both process chemicals occurs in wetland plants.