Six dissociable groups exist in tetrahydrofolic acid in the range Ho -3.0 to pH 14. The assignments in tetrahydrofolic acid by titrimetric and spectrophotometric comparisons with model compounds, +uninobenzoylglutamic acid and 2-amino-6,7-dimethyl-5,6,7,8-tetrahydro-4-pteridinone, are as follows: acidic ionization of amide, pK’ 10.5; Ns, pK’ 4.82; y-carboxyl, pK’ 4.8; cr-carboxyl, pK’ 3.5; N1, ...

A modification of the semiautomated assay method of Antonis (1965. J. Lipid Res. 6:307-312) for free fatty acid is presented. Free fatty acids are extracted from serum or plasma into di-n-butyl ether-2-methoxyethanol; the extract is almost free from phospholipids. The acids are analyzed in a portion of extract by a copper soap method using diphenylcarbazide. The extractant, being less dense tha...

An acid-titration method for the determination of bicarljonate and titratable acid in the one sample of urine is described. The method needs only one manipulation of the sample of urine, and was devised to simplify routine laboratory methodology. The accuracy and precision of the urinary bicarbonate method during routine laboratory use is comparable to that obtained by using the Van Slyke manom...

Microbiological tests have aided greatly in the isolation work on “L&o!x~ciZZus casei factor,” demonstrated by Snell and Peterson in 1940 (l), and “folic acid,” the nutrient required by Streptococcus lactis R as defined by Mitchell et al. (2). It seems likely that bacterial assays will continue to play an important role in the study of these compounds, since development of chemical methods has ...

The fluorine content of drinking waters has become a matter of great interest to those concerned with the control and diminution of dental caries. In the U.S.A. many are of the opinion that the epidemiological studies of Dean (1938) and his co-workers (Dean, Arnold & Elvove, 1942) provide convincing evidence for the belief that, within certain limits, there is an inverse relationship between th...

Based on the nitrogenous base or tertiary amine moiety in zolmitriptan (ZMT), an anti-migraine drug, two highly accurate and selective titrimetric methods are proposed for the determination of ZMT in bulk drug and pharmaceuticals. In these methods, the drug dissolved in glacial acetic acid, was titrated with acetous perchloric acid and end point determined either visually by using crystal viole...

Four simple titrimetric procedures are described for the determination of lisinopril (LNP) in bulk and in pharmaceuticals based on the neutralization of basic-amino and acidic carboxylic acid groups present in LNP. Method A is based on the neutralization of basic amino groups using perchloric acid as titrant in anhydrous acetic acid medium. Method B, method C and method D are based on neutraliz...

Two simple titrimetric methods have been developed for the determination of hydroxyzine dihydrochloride (HDH) in pure form and in tablets. The principle of the methods are simple acid-base reactions in which the hydrochloride content of the drug was determined by titrating with an aqueous standardized NaOH solution either visually using phenolphthalein as indicator (method A) or potentiometrica...

The elements of the mechanized fluorometric lipase (EC 3.1.1.3) assay of Fleisher and Schwartz [Clin. Chem. 17, 417 (1971)] were made optimum; a manual adaptation was also developed. Hydrolysis of the monodecanoyl fluorescein substrate by hog pancreatic lipase is a zero-order reaction. The hydrolytic activity of normal human serum, serum from hospitalized patients without pancreatitis, and seru...

Chloride concentrations in sweat were measured by "vacancy liquid chromatography," a technique in which anions eluting from an ion-exchange column in the presence of an elution buffer which absorbs at 280 nm cause a decrease in absorbance proportional to the concentration of the anion. Less than 1 microL of sweat suffices for this analysis, which takes 5 min per sample. Results were comparable ...