An infrared spectrophotometric method of estimating polyethylene glycol 4000.

In studies of intestinal absorption non-absorbed markers are used to indicate changes in volume of the contents of the bowel. Polyethylene glycol 4000 (PEG 4000), a popular marker, has been shown to fulfil the criteria of a volume indicator (Hyden, 1956b; Jacobson, Bondy, Broitman, and Fordtran, 1963; Maddrey, Serebro, Marcus, and Iber, 1967; Shields, Harris, and Davies, 1968). The concentration of PEG 4000 in biological fluids is usually determined by the turbidimetric method of Hyden (1956a) or one of its modifications (Lundh, 1958), both of which are based on the development of a PEG-TCA-Ba complex when PEG is exposed to trichloracetic acid (TCA) in the presence of barium ions. However, these methods are not entirely satisfactory (Malawer and Powell, 1967) and have the additional disadvantages of being tedious and time-consuming and requiring a considerable amount of glassware. This paper describes a technique for the estimation of PEG 4000 by infrared spectrophotometry and compares its accuracy and precision with those of the turbidimetric methods (Hyden, 1956a; Lundh, 1958).