A standard calibration curve was constructed based on Nash methodand regression equation of y = 0.0141x + 0.0198 (R2 = 0.9961) wasobtained. Four mackerel fish extract samples were then prepared,where one sample was not modified in any way and the remaining threesamples were spiked with formaldehyde to obtain concentrations of 8,10 and 15 ppm, respectively. The unmodified sample was found tocontain 7.64 ppm of formaldehyde, while the other three spiked samples contained 9.57, 11.64 and 16.57 ppm of formaldehyde, respectively using the Nash method.