High-Sensitivity Analysis of Nonylphenol in River Water Using GC-MS/MS

n Analytical Conditions Nonylphenol (NP) is used as a raw material for the production of surfactants, and as an antioxidant used to protect rubber and plastics, etc. However, in recent years, it has been specified as a substance that can cause endocrine disruption in the environment (environmental hormone). NP, a type of alkylphenol, can theoretically exist as 211 structural isomers. Among these, the main component that is generated by the reaction of nonene (trimer of propylene) with phenol is the branched 4-nonylphenyl (4-NP). Analysis is conducted by solid phase extraction – gas chromatography – mass spectrometry, and quantitation is conducted by (1) establishing the composition ratio of the 13 isomers included in a 4-NP standard mixture, (2) calculating the concentration of each of the detected 13 isomers using a calibration curve generated for each isomer, and (3) multiplying each isomer by the corresponding composition ratio, and calculating the sum. However, when conducting GC/MS measurement of each isomer separately, the type of the analytical column or the instrument sensitivity may adversely affect the peak of the low-composition-ratio twelfth isomer. Therefore, we investigated the use of a high m/z selectivity triple quadrupole gas chromatograph-mass spectrometer (GC-MS/MS). By optimizing the MS/MS analytical conditions, selective detection of thirteen 4-NP isomers was achieved with high sensitivity. Further, in the analysis of NP in river water, which typically contains many contaminants, analysis was possible without adversely affecting identification accuracy, even when omitting the cleanup procedure that may reduce the recovery rate. For the nonylphenol standard mixture, we used a 4-nonylphenol standard (Code No.: 28640-96, Kanto Chemical), a 4(3,6-dimethyl-3-heptyl) phenol-C6 standard solution (Code No.: 043-32861, Wako Pure Chemical Industries), and a p-n-nonylphenol-d4 standard (Code No.: 141-07081, Wako Pure Chemical Industries). The standard solutions for generating a calibration curve were prepared at concentrations of 0.01, 0.05, 0.1, and 0.5 μg/mL, respectively, and for all of the c a l i b r a t i o n c u r v e s t a n d a rd s o l u t i o n s e r i e s , 4(3,6-dimethyl-3-heptyl) phenol-C6 (surrogate) was prepared to obtain a concentration of 0.1 μg/mL, and p-n-nonylphenol-d4 (internal standard) was prepared to obtain a concentration of 0.1 μg/mL.