Glycine-sodium hydroxide

Ke and Regier [71] have described a direct potentiometric determination of fluoride in seawater after extraction with 8-hydroxyquinoline. This procedure was applied to samples of seawater, fluoridated tap-water, well-water, and effluent from a phosphate reduction plant. Interfering metals, e.g., calcium, magnesium, iron, and aluminium were removed by extraction into a solution of 8-hydroxyquinoline in 2-butoxyethanol-chloroform after addition of glycine-sodium hydroxide buffer solution (pH 10.5 to 10.8). A buffer solution (sodium nitrate-l,2-diamino-cyclohexane-N,N,N. AT-tetra-acetic acid-acetic acid pH 5.5) was then added to adjust the total ionic strength and the fluoride ions were determined by means of a solid membrane fluoride-selective electrode (Orion, model 94-09). Results were in close agreement with and more reproducible than those obtained after distillation [72]. Omission of the extraction led to lower results. Four determinations can be made in one hour. 

For the assay of a-D-mannosidase, the incubation mixture employed in our laboratory contained 0.5 ml of M acetate buffer at a pH appropriate for the particular enzyme preparation, 1.5 ml of 16 mM p-nitrophenyl a-D-mannopyranoside, 1.5 ml of water (which could be replaced by other additives as required), and 0.5 ml of suitably diluted, enzyme preparation. After 1 hour at 37°, the reaction was terminated, and the color was developed by adding 4 ml of 0.4 M glycine-sodium hydroxide buffer, pH 10.5. The mixture was centrifuged for 15 minutes at 1500 g, and the color intensity of the liberated p-nitrophenol (25-150 fig) in the supernatant liquor was measured on a Spekker photoelectric absorptiometer, with use of Ilford No. 601 violet filters having maximal transmission at 430 nm, and a 1-cm light path. Separate control-experiments for enzyme and sub-... 

Lobster hemocyanin in glycine-sodium hydroxide buffer at pH 9.6 undergoes a reversible whole molecule-half molecule dissociation which is very sensitive to the level of free calcium ion present (12). This dissociation process is also very sensitive to pH (12). Cann and colleagues have developed, by simulation techniques (13,14), a general picture of the kinds of partial or complete boundary resolution that may be expected for such coupled systems in various types of transport experiments. Kinetic investigations of the lobster hemocyanin system under the conditions of the present study were developed by using stopped-flow... 

To 1 ml. of 0.2 M acetic acid-sodium hydroxide buffer at the appropriate pH was added 0.5 ml. of 0.04 M o-nitrophenyl /3-galacturonide solution adjusted to the same pH, followed by 2 ml. of water and 0.5 ml. of enzyme. After 1 hr. at 38°, the reaction was terminated by adding 4 ml. of 0.4 M glycine-sodium hydroxide buffer of pH 10.0, and the mixture was centrifuged at 1500 g for 15 min. The intensity of the yellow color was read with the Spekker absorptiometer, using Ilford No. 601 violet filters (maximum transmission at 435 him). 

The assay method of Dalziel is convenient. In a recording ultraviolet spectrophotometer set at 340 nm is placed a 3-mL quartz cuvette containing 2.4 mL of 0.10 M glycine-sodium hydroxide buffer solution, pH 9, 500 pL of a 54 mM solution of ethanol 1n the same buffer, and 100 pL of a 15 nM solution of NAD, also in the same pH 9 buffer. The volume is made up to 3.0 mL, and the assay initiated by the addition of 10 pL of a 1 mg per mL solution of HLADH in 0.10 M "Tris-hydrochloric acid buffer", pH 7.4. The change in optical density at 340 nm 1s monitored at 25°C and the activity calculated from the following equation ... 

I 0.04 M glycine-sodium hydroxide buffer (pH 10.32), in aqueous methanol. 

The glycine-sodium hydroxide mixtures are less useful than the others because of the marked variation of hydrogen ion concentration with temperature. 

The marked influence of temperature on the pH of sodium hydroxide solutions is due of course to the large increase of the ionization constant of water. The pH of glycine-hydrochloric acid mixtures is unaffected by temperature variation, whereas glycine-sodium hydroxide solutions are extremely temperature-sensitive. Such behavior is to be expected on the basis of the hybrid ion structure of amino acids. 

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