Abstract
A colorimetric assay is described for the measurement of Pluronic F-68 in animal cell culture medium. The assay is based on the formation of a complex with cobalt thiocyanate as previously developed for the measurement of Pluronic in liver tissue. To adapt the assay for the lower detection levels required in cell culture medium, the absorbance of the complex was measured at 328 nm. The reproducibility of the assay was improved by washing the complex with ethyl acetate. The addition of a critical volume of ethanol was found to be necessary to reduce the interference caused by unknown components of the culture medium. The assay was linear between concentrations of 0.01 and 0.2% (w/v) Pluronic in serum-free medium. At the lower level of detection of 0.01% (w/v), the coefficient of determination (R2) was 0.998. The presence of serum in the medium decreased the sensitivity of the assay, which nevertheless was linear from 0.04 to 0.16% (w/v) Pluronic. The sensitivity and precision of the method are appropriate to study the dynamics of Pluronic in large-scale cell cultures in which Pluronic is added to reduce hydrodynamic cell damage.