Journal of Lipid Research, Vol. 7, 745-749, November 1966
Copyright © 1966 by Lipid Research, Inc.

Automatic titration of plasma fatty acids by photocolorimetry

Robert P. Noble

The Sharon Research Institute, The Sharon Hospital, Sharon, Connecticut

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.

Supplementary key words automatic • photocolorimeter • titration • free fatty acids • single phase • Nile blue

Submitted on May 17, 1966
Accepted on July 27, 1966

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