| Summary: | A photocolorimeter for rapid automatic titration of free fatty acids is described. The solvents, absolute ethanol and hexane, form a single-phase titration mixture containing Nile blue indicator. The titrant, NaOH in 60% ethanol, is delivered by a motor-driven microsyringe; as alkali is added and the titration mixture turns pink, the intensity of light reaching a photocell through a 600 mμ interference filter increases. Increased current is generated until at a preselected number of microamperes a cut-off switch is activated which halts the drive motor.Titrations of FFA in the range 150-1500 μeq/liter of palmitic acid standard are accomplished in approximately 1 min with a standard error of the mean of ±1.3-6.5 μeq/liter. The titration end point is independent of the operator. The solutions are stable and the daily titration blank and calibration remain constant. The procedure, therefore, is relatively simple and is quickly set up for routine determinations.
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