Quantitative analysis of 2-methoxy-3,5-dimethylpyrazine as an earthy-musty off-odor compound in drinking water using HS–SPME–GC–MS

Abstract

The presence of off-odors can influence the overall taste of drinking water, with earthy-musty odors often being perceived as indicator of stale or poor-quality water. Recently, earthy-musty off-odor from drinking water was reported in some part of South Korea. The earthy-musty off-odor compound was identified as 2-methoxy-3,5-dimethylpyrazine (2-MDMP) through simultaneous steam distillation and solvent extraction-gas chromatography-mass spectrometry (SDE-GC–MS) and GC–olfactometry (GC-O). For quantitative analysis of 2-MDMP in drinking water, headspace-solid phase microextraction-GC–MS (HS–SPME–GC–MS) method was optimized in terms of salt concentration, absorption temperature, and absorption time. Validation of the method confirmed its reliability, with linearity (R² = 0.9998) at working range of 2.5–500 ng/mL, limit of detection (0.83 ng/mL), and limit of quantification (2.5 ng/mL). The method also demonstrated that precision and accuracy were satisfactory. Using validated HS–SPME–GC–MS, the concentration of 2-MDMP in drinking water exhibiting earthy-musty off-odor was quantified to 77.2 ng/mL.