Highly sensitive spectrophotometric determination of phenol in tap water coupled with solid-phase extraction

A sensitive spectrophotmetric method for the determination of phenol using a solid-phase extraction cartridge was developed. It is based on the oxidat ive coupling of 4-aminoantipyrine with phenol to form an azo compound (amin oantipyrine dye) in the presence of hexacyanoferrate(III) at pH 10. The for med azo compound was adsorbed on a Sep-Pak C-18 cartridge. After the concen trated compound was eluted with a 60%(v/v) acetonitrile solution, the absor bance was measured at 503 nm. On the other hand, a sample solution containi ng phenol was passed directly through a Porapak R-DX cartridge, and was the n eluted with a 90%(v/v) methanol solution. The elute was measured at 501 n m after adding reagents and developing the color intensity. The proposed me thods using Sep-Pak C-18 and Porapak R-DX cartridges showed a high enhancem ent factor (10 similar to 100) and made it possible to determine the 1 simi lar to 8 ng ml(-1) level of phenol with a low relative standard deviation. The recoveries of 1 and 4 ng ml(-1) phenol added to tap water were 96 and 9 5% for Sep-Pak Cls and those of 2 and 4 ng ml(-1) were 103 and 88% for Pora pak R-DX.