we propose a procedure for the determination of lactic acid or lactate in biological fluids , which is simple and low cost with respect to the known methodologies . this procedure can be used by unskilled personnel and it can be implemented in disposable test strips and portable measure devices . the procedure is based on the photochemical reaction of lactic acid with fe , which is reduced to fe when irradiated with uv light . the fe , produced proportionally to the amount of lactate in the sample , is determined electrochemically or using its reaction with a colored complexing agent , such as 1 , 10 - phenanthroline , and determined by spectrophotometry . this method is advantageous both for the low cost of the reagents employed , and for their short and long term stability .