Abstract: In an acetate buffer of pH 6.0,and in the presence of CTMAB,a stable complex,having the mole ratio (Co∶R) of 1 to 3,was formed between cobalt ion and nitroso R salt,which was concentrated on C18 solid phase extraction column,achieving a concentration multiplication of 100 times.The colored complex on the column was eluted with 1.00 (±0.01) mL of ethanol,the absorbance of which was measured at 530 nm with a 1 cm cell using reagent blank as reference solution.Beer′s law was obeyed in the range of 0.05-5.0 mg·L-1.This method has been applied to the determination of cobalt in some foodstuff samples and water samples,giving results in consistency with the results found by AAS,and values of RSD′s (n=5) and recoveries of ≤2.5% and in the range of 97%-103%.