Figure 2. Total ion chromatograms from SIM GC/MS of (
a) one microgram per liter standard mix, (
b)
Detroit wastewater, March 1998, and (c) Minnesota River, March 1998. [IS, internal standard; NP, 4-
nonylphenol; NP1-3EO, 4-nonylphenol-mono, di, or triethoxylate]