4-Nonylphenol, a degradation product of ethoxylated alkylphenols, due to its harmful effects on the environment, has been banned in European Union countries, alongside their precursors. The guide on quality of drinking water from the United States Environmental Protection Agency (US EPA) recommends a maximum concentration of 28 µg L-1 for fresh water. In Brazil, there is no clear legislation containing values of maximum concentration of 4-nonylphenol. Due to this lack of regulation, a continuous monitoring is necessary for this pollutant in environmental samples. The occurrence of 4-nonylphenol (4-NP) in the surface waters of Guandu River in the state of Rio de Janeiro, Brazil, was studied by using solid-phase extraction and reversed phase liquid chromatography separation with UV detection. The analytical method satisfies these requirements, being able to detect and quantify 4-NP in a desired concentration range. Of the 19 samples analyzed, 4-nonylphenol was detected in 12, quantified in 2, showing concentration levels of 1.73 and 2.32 µg L-1 in Santa Cruz and Paracambi, respectively. This is the main hydrographic basin in the state of Rio de Janeiro, where water is collected for treatment and later distributed to most cities in the metropolitan region, including Rio de Janeiro City, and these results are therefore alarming.

ABSTRACT This paper aims to gather and discuss important information about nonylphenol, such as physical chemistry properties, toxicity and analytical methods in various matrices. As a degradation product of ethoxylated alkylphenols, nonylphenol presents a higher degree of reactivity than its precursor. Due to its harmful effects on the environment, use and production of nonylphenol has been banned in European Union countries, alongside their precursors. The guide on quality of drinking water (USEPA) recommends a maximum concentration of 28 µg L-1 for fresh water. In Brazil, there is no clear legislation containing values of maximum concentration of nonylphenol. Due to this lack of regulation, a continuous monitoring is necessary of this pollutant in environmental samples. This paper aims to encourage further studies on nonylphenol, seen as a critical environmental pollutant. For proper monitoring is necessary to have reliable analytical methods and easy to perform in routine analysis.