The methods currently used for the estimation of tryptophan are based on one of the following principles: Reaction with aldehydes in acid solution (1, Z), with glyoxylic acid (3), with mercury salts and nitrous acid (4,5), by determination after isolation from its mercury salt (6)) or by the use of Marshal’s reagent (7). Of the above mentioned methods, those based on aldehyde reactions and on t...

Several new descriptions of colorimetric methods for the determination of blood sugar have been described in recent years (for example, Polis and Sortwell, 1946; Somogyi, 1945; Nelson, 1944; Haslewood and Strookman, 1939). These procedures are all based on the use of alkaline copper reagents and on the production of molybdenum blue by the action of cuprous copper on complex molybdic acid soluti...

The method to be described for the determination of hemoglobin depends upon the comparison, in a calorimeter, of carbon monoxide hemoglobin solutions, one of which has a known hemoglobin content. Hoppe-Seyler (1) was the first to describe carbon monoxide hemoglobin and to make use of this stable combination for estimating the hemoglobin content of blood. He devised a “double pipette” for compar...

In 1926 we (1) published a calorimetric method for the estimation of blood calcium, in which the calcium is precipitated from an alkalinized trichloroacetic acid filtrate as calcium phosphate and determined as phosphate by the Benedict and Theis (2) method for the estimation of inorganic phosphorus. We have since simplified and shortened this method and in this paper we wish to report our impro...

The method to be described for the determination of hemoglobin depends upon the comparison, in a calorimeter, of carbon monoxide hemoglobin solutions, one of which has a known hemoglobin content. Hoppe-Seyler (1) was the first to describe carbon monoxide hemoglobin and to make use of this stable combination for estimating the hemoglobin content of blood. He devised a “double pipette” for compar...

Turbidimetric methods for assay of hyaluronidase activity are based upon the measurement of the optical density of suspensions of substrateprotein combination in an acid environment (1). The reliability of this measurement depends upon careful control of the conditions under which turbidity develops (2), and even then the relation between substrate concentration and optical density is linear ov...

The method to be described for the determination of hemoglobin depends upon the comparison, in a calorimeter, of carbon monoxide hemoglobin solutions, one of which has a known hemoglobin content. Hoppe-Seyler (1) was the first to describe carbon monoxide hemoglobin and to make use of this stable combination for estimating the hemoglobin content of blood. He devised a “double pipette” for compar...

Biopharmaceutical products must be proved to be minimized as much as possible of contaminating host cell proteins (HCPs) prior to approval by the regulatory authorities. Commonly, ELISAs are used for HCP determination and authorities ask for clear and manifest proof that the antibodies used in the HCP ELISA are fit for purpose. Their suitability needs to be shown, not only by the obtained ELISA...

Following the introduction by Duncombe of a colorimetric micromethod for the determination of free fatty acids (FFA) dissolved in chloroform, we studied the optimum conditions for chloroform extraction of FFA from blood or other biological fluids. A degree and rate of extraction similar to those with Dole’s extraction mixture were obtained. Phospholipids are not extracted by the procedure descr...

‘THE RECENT DEVELOPMENT of a new colorimetric procedure (TransAc*), for the determination of serum glutamic oxalacetic transaminase utilizing the diazonium salt, 6-benzamido-4-methoxy-m-toluidine diazonium chloride, as the color developer with a specificity for oxalacetic acid, prompted the following experiments. Determination of glutamic oxalacetic transaminase activities were performed accord...