Showing papers on "Buffer solution published in 1984"

Effects of pH and Temperature on the Stability and Decomposition of N,N′N″-Triethylenethiophosphoramide in Urine and Buffer

Abstract: N,N',N"-Triethylenethiophosphoramide (thiotepa) was dissolved at 100 micrograms/ml in urine or in 0.1 M sodium acetate buffer and incubated at 37 degrees or 22 degrees. After 0, 15, 30, 60, 90, and 120 min of incubation, 0.1-ml samples were extracted into ethyl acetate and analyzed by gas-liquid chromatography (1.8-m X 2-mm column packed with 3% OV225 on 100/120 Supelcoport; oven at 180 degrees; injection port and nitrogen-phosphorus detector at 230 degrees). Thiotepa was more stable at 22 degrees than at 37 degrees and at pH 6 to 7 than at pH 4 to 5.5. After 2 hr of incubation at 37 degrees, thiotepa concentrations decreased by 40% at pH 5.0 but only 10% at pH 6 or 7. Although thiotepa concentrations declined as described above, alkylating activity, as assessed by p-nitrobenzyl pyridine reactivity, was stable at all temperatures and pHs tested. Partition coefficients of thiotepa degradation products into toluene, ethyl acetate, diethyl ether, and hexane were determined after 0 and 120 min of incubation in urine at pH 4.0. The extractability of alkylating activity into these organic solvents decreased dramatically after 120 min. Thiotepa degradation products were extracted from urine at pH 4.0 after 0, 30, 60, and 120 min incubation at 37 degrees and were separated by thin-layer chromatography. In addition to thiotepa (Rf 0.15), 3 degradation products possessing p-nitrobenzyl pyridine alkylating activity (Rf 0.35, 0.52, and 0.60) were observed during the course of incubation. The structures of the materials with Rf 0.35 and 0.52 were identified by mass spectrometry and indicated that thiotepa degradation occurs by successive addition of HCl molecules with opening of the aziridine rings and conversion to 2-chloroethyl moieties.

Determination of ionization constants by spectrophotometry

Abstract: The determination of ionization constants by ultraviolet or visible spectrophotometry is more time-consuming than by potentiometry. However, spectrometry is an ideal method when a substance is too insoluble for potentiometry or when its pKa value is particularly low or high (e.g. less than 2 or more than 11). The method depends upon the direct determination of the ratio of molecular species (neutral molecule) to ionized species in a series of non-absorbing buffer solutions (whose pH values are either known or measured). For this purpose, the spectrum of the molecular species must first be obtained in a buffer solution whose pH is so chosen that the compound to be measured is present wholly as this species. This spectrum is compared with that of the pure ionized species similarly isolated at another suitable pH. A wavelength is chosen at which the greatest difference between the absorbances of the two species is observed. This is termed the ‘analytical wavelength’. Fig. 4.1, in which the base 2-amino- pyridine is used as an example, shows how these two pH values can be found.

Reagent for blood analysis

Abstract: A reagent for blood analysis comprises, as a lysing reagent for leukocyte count, tetradecyltrimethylammonium bromide and/or hexadecyltrimethylammonium chloride, dodecyltrimethylammonium chloride, and citric acid. This reagent is characterized by showing three-peaks fractionation of leukocytes in measuring by means of an automatic blood-analysis instrument. The lysing reagent is used together with a diluent comprising boric acid buffer solution, ethylenediaminetetraacetic acid and (2-pyridylthio-1-oxide) sodium.

Estimation of cellular pH gradients with 31P-NMR in intact rabbit renal tubular cells.

Abstract: To determine intracellular pH gradients rabbit renal cortical tubular cells were prepared by collagenase separation, suspended in a Krebs-Ringer buffer solution, and gassed with 95% O2-5% CO2 in a special nuclear magnetic resonance (NMR) probe. Renal tubular cellular pH was determined simultaneously from the distribution of 14C-dimethadione (DMO) (pHDMO) or the chemical shift of inorganic phosphate (pHNMR). Experiments were performed at different external pH values (pHe) ranging between 6.52 and 7.20. pHNMR, a measure of cytoplasmic pH, changed by an amount equal to the change in pHe. pHDMO, however, a measure of cytoplasmic plus mitochondrial pH, changed less than pHe as the latter increased. pHDMO, higher than pHNMR at low pHe, became equal to pHNMR at higher pHe values. By use of assumed mitochondrial volumes of 30-40% mitochondrial pH was calculated from pHDMO and pHNMR. Mitochondrial pH remained relatively constant over the entire pHe range studied. Since cytoplasmic pH fell as pHe was lowered, the transmitochondrial pH gradient increased at low pHE values. These findings suggest that the transmitochondrial pH gradient may be important in regulating metabolism.

Specific acid catalysis in the decomposition of trialkyltriazenes

Abstract: On etudie les decompositions des triazenes R−N=N−NR'R'' (R=R'=C 4 H 9 , R''=CH 3 ; R=R'=R''=CH 3 ; R=R'=CH 3 , R''=COCH 3 ; R=R'=CH 3 , R''=CO 2 C 2 H 5 )

Methods for Reliable pH Measurements of Precipitation Samples

Abstract: Significant errors in precipitation acidity determinations can result from improper use of pH electrodes. Conventional electrodes measure free hydrogen ion activity instead of hydrogen ion concentration or free acidity. Correction from activity to concentration is a function of ionic strength and can be large for the low ionic strengths typical of precipitation samples. Also, differences between sample and standard calibration buffer solution ionic strengths can result in liquid-junction potentials that affect electrode readings. Streaming potentials due to the stirring of precipitation samples can cause the single, largest error in pH. Certain procedures can be employed to reduce individual types of errors. These and methods to assess pH electrode performance are discussed.

Method for manufacturing liposomes

Abstract: A method and apparatus for manufacturing liposomes is characterized by optically monitoring the light transmission of a liposome precursor solution and controlling the flow rate and/or temperature of the precursor solution and/or a dialysis buffer solution in accordance therewith.

A phosphate-catalysed acyl transfer reaction. Hydrolysis of 4-nitrophenyl acetate in phosphate buffers

Abstract: The pseudo-first-order rate constants for the phosphate-catalysed hydrolysis of 4-nitrophenyl acetate have been determined in water at 310.5 K. The reaction has been followed spectrophotometrically by the disappearance of the ester and with n.m.r, spectroscopy by the appearance of both acetyl phosphate and the acetate ion and by the disappearance of ester. A phosphate-catalysed acyl transfer mechanism has been identified, in which the aryl ester is attacked by phosphate to give acetyl phosphate which is subsequently hydrolysed by water to acetate ion and regenerated catalyst. At concentrations of total phosphate exceeding 1.0 mol dm-3 the presence of dimeric phosphate species causes the appearance of a non-linear rate-concentration profile. Catalysis has been also been observed in 2,2'-(propane-1,3-diyldiimino)bis(propane-1,3-diol) buffer solutions.

Kinetics and Mechanism of the Degradation and Epimerization of Sodium Cefsulodin in Aqueous Solution

Abstract: The kinetics of the degradation and epimerization of cefsulodin in various buffer solutions were studied at 25°C and 0.6 ionic strength. The overall degradation was a pseudo-first-order reaction in the pH region studied. The rate law of the degradation could be approximated in terms of specific acid-base and water catalyzed hydrolysis, that is k1 (total degradation rate constant)=kH+×αH++k0+kOH-×αOH-. The apparent activation energies of the degradation reaction were 20.7, 22.3, 23.0 and 27.7 kcal mol-1 at pH values of 2, 4, 6, and 9, respectively. The epimerization of cefsulodin was proved to be catalyzed by hydroxide ion from the epimerization rate constant-pH profile, solvent effects using ethanol, and the apparent activation energies (which were 27.0 and 26.1 kcal mol-1 for the apparent forward and reverse epimerization reactions at pH 9.0, respectively). The mechanism of epimerization of cefsulodin is proposed to involve removal of the α-proton of the benzyl side chain by hydroxide ion to form an anioic intermediate. Interactions of cefsulodin with amines and aminoglycosides were also examined. The reaction was pseudo-second-order and the second-order rate constants for various amines and aminoglycosides were compared. It was found that intramolecular catalysis is the predominant factor for amines. An equation is proposed for the second-order rate constants of aminoglycosides. Peaks of unknown products in the alkaline reaction solutions could be separated under the high performance liquid chromatography conditions of the current study.

Spectrophotometric determination of rhodium(III) with butaperazine dimaleinate

Abstract: Rhodium(III) forms an orange-red 1 : 1 complex with butaperazine dimaleinate at room temperature in sodium acetate-hydrochloric acid buffer solution containing copper(II) sulphate and ascorbic acid. The orange-red complex exhibits an absorption maximum at 465 nm. Beer's law is obeyed for 0.2–28 µg ml–1 of rhodium. Sandell's sensitivity of the reaction is 0.042 µg cm–2 and the molar absorptivity is 2.44 × 103 l mol–1 cm–1. The tolerance limits of platinum metals, base metals and common anions are reported.

Biphasic photolysis of riboflavin. III. Effects of ionic strength on the photolysis.

Abstract: Riboflavin undergoes a characteristic biphasic photolysis with a low-intensity light source, depending on the ionic strength of the phosphate buffer used. In higher ionic strength phosphate buffer, an initial faster phase is followed by a slower second phase, and vice versa in lower ionic strength buffer. On the basis of the circular dichroism spectra, a side chain-isoalloxazine ring interaction through hydrogen bonding is considered to be responsible for the ionic strength dependence.

Deficiencies and improvement of methemoglobin assay.

Abstract: A day-to-day variability in results was encountered when using the Dubowski method for the routine clinical determination of methemoglobin in blood. Therefore, studies were performed to determine the source(s) of variability in the method as described by Dubowski. It was determined that complete lysing of red blood cells is dependent upon both temperature of the buffer and the amount of lysing agent. Low buffer temperatures (less than 14 degrees C) produced highly variable results. This variability can be reduced by increasing the level of lysing agent to 40 mg per 20 mL of diluted blood. It was found that by using 37 degrees C buffer solution temperature and 40 mg Triton X-100 as lysing agent per 20 mL of diluted blood (1:20 with 0.25M sodium phosphate buffer, pH 7.4), the precision (percent coefficient of variation = 2%) and the accuracy (percent coefficient variation = 5.5%) were excellent.

Valproic acid binding to human serum albumin and human plasma: effects of pH variation and buffer composition in equilibrium dialysis

Abstract: The binding of valproic acid (VPA) to human serum albumin (HSA) and to pooled human plasma has been investigated by using equilibrium dialysis with three different dialysis solutions: phosphate buffer (solution I), Krebs solution (solution II), and Krebs solution without calcium (solution III). The effect of pH variation from 6.4 to 8.2 has been also investigated. VPA free fraction increased by increasing pH with all the dialysis solutions (from 4.1% at pH 6.4 to 9.4% at pH 8.2 with solution I, from 8.1% to 11.3% with solution II, and from 10.6% to 14.3% with solution III, in plasma). At each pH value, free fraction obtained with solution III was the highest and that obtained with solution I was the lowest. Data in plasma and HSA solution were similar. In a separate experiment we compared (at pH 7.4, with plasma) the three more frequently used dialysis solutions: phosphate buffer, phosphate buffer with NaCl, and Krebs solution. They gave, respectively, a mean VPA free fraction of 7.8, 10.3, and 12.7%. These findings can explain the wide range of VPA free fraction values reported in the literature. Researchers intending to determine VPA free concentration by equilibrium dialysis should take into account these methodological aspects.

Low molecular protein having carcinostatic effect

Abstract: NEW MATERIAL:A low molecular protein having the following properties. Molecular weight, 16,000+ or -1,500; isoelectric point, 3.8+ or -0.3pH; peak of UV absorption in 0.02M tris-HCl buffer solution added with 0.1M NaCl (7.8pH), 277nm, the lowest point of the absorption, 250nm; the solution obtained by dissolving 3mg of the protein in 1ml of 0.02M tris-HCl buffer solution (7.8pH) is colorless and transparent; addition of >=70V/V% of acetone or ethanol to said solution causes precipitation; the aqueous solution is weakly acidic; color reactions of peptide bond and amino acid, positive to biuret reaction, Folin-Lawry reaction, and ninhydrin reaction after hydrolysis with hydrochloric acid. USE:A carcinostatic agent. It exhibits direct cytotoxicity to the cultured mouse L- cell in vitro, and exhibits antitumor activity against female mouse affected with A sarcoma in vivo. PROCESS:A substance having immunoactivating activity is administered to a mammal, then an endotoxin originated from Gram-negative bacteria or lectin originated from vegetable is administered thereto to induce and produce the objective low molecular protein.

Calcitonin drug through nose containing basic and/or neutral amino acid

Abstract: PURPOSE: The titled drug through nose comprising calcitonin as an active ingredient and a specific absorption promoter. CONSTITUTION: A drug composition for administration through nose, obtained by adding one or more amino acids selected from basic amino acid and/or neutral amino acid (e.g., arginine,lysine,citrulline,threonine, etc.) As an absorption promoter and calcitonin as an active ingredient to a liquid diluent or a carrier pH of an aqueous solution is preferably 3W5 with respect to stability. A citrate, tartrate, malate, etc., are used as a buffer solution. In an administration form, since it is administered to the nasal ca-vity, it is dropped or sprayed by using a drop container, spray container, or aerosol applicator for nose,etc. The concen tration is 200W6,000IU/ml, a dose is preferably 0.05W0.2ml/time, and properly onceWfive times daily in the case of an aqueous solution. COPYRIGHT: (C)1986,JPO&Japio

Stabilization of enzyme labelled antibody

Abstract: PURPOSE:To extremely reduce the lowering in enzymatic activity even in a long- term storage state ranging from preparation to use, by adding one or more of non-reducing sugars equal to or higher than disaccharides to an enzyme labelled antibody. CONSTITUTION:An enzyme labelled antibody, especially pref., an enzyme labelled antibody prepared by bonding maleimide introduced peroxidase and F(ab')2 is mixed with an adequate buffer solution with pH of 6.5-8.0 such as a phosphate buffer solution or a Tris buffer solution to prepare a solution which is, in turn, liophylized or spray dried according to a usual method to obtain a powdery preparation. In this method, one or more of non-reducing sugars equal to or higher than disaccharides such as origosaccharides for example, sucrose, trehalose, turanose, raffinose or melezitose, polysaccharides such as dextran and sugar alcohol is added to the enzyme labelled antibody at the time of mixing with the above mentioned buffer solution. By this method, at the time of preparation for obtaining the liophylized product and preservation of the preparation, the good stabilization of the enzyme labelled antibody is obtained.

Reference electrodes for use in the potentiometric determination of chloride. Part I. Assessment of mercury-mercury(I) sulphate electrodes

Abstract: Mercury-mercury(I) sulphate reference electrodes are used in the potentiometric determination of chloride. There have been various reports of their erratic behaviour, which is especially serious because chloride-selective electrodes are often working at the limits of their sensitivity in highly pure waters, such as condensed steam and boiler water. The loss of precision in e.m.f. in such circumstances has a much larger effect on the precision in concentration terms than when electrodes are working in their usual (Nernstian) sensitivity range. Commercial mercury-mercury(I) sulphate electrodes have been tested over several weeks of continuous operation so that their performance can be assessed when used under conditions similar to those of chloride monitoring, i.e., in pH 4.4 acetate buffer solution with silver chloride electrodes and 0.01 mol l–1 nitric acid solution with mercury(I) chloride electrodes. Electrodes were obtained from two manufacturers and were of two types—one with ground-glass sleeve liquid junctions and one with a ceramic-frit junction. The latter was the best of those tested. The rate of change of its potential with respect to a calomel electrode was less than 0.5 mV over 100 h and the standard deviation of its potential over a week's operation was about 0.3–0.5 mV. Deviations of potential previously reported with this type of electrode could not be reproduced in this work. Some electrodes with ground-glass sleeve junctions became erratic after 2–4 d in the nitric acid solution normally used with mercury(I) chloride sensing electrodes. Their performance was better in the acetate buffer medium used with silver chloride sensing electrodes but inferior to that of similar electrodes with ceramic frit junctions.

Effects of Al3+ Ion on Tc-99m Sulfur Colloid Preparations with Different Buffers

Abstract: The effect of aluminum ions on two Tc-99m sulfur colloid preparations, one with phosphate buffer and the other with acetate buffer, was studied by the filtration technique using Nuclepore filters of sizes 0.6 μm, 3 μm, and 10 μm. The aluminum concentrations were

Kinetic Study on Hydrolysis of Silicon Phosphate in Aqueous Alkaline Solutions

Abstract: Kinetic study of the hydrolysis of silicon phosphate, Si3(PO4)4 (hexagonal), was carried out in borax buffer solutions (pH 5–12, temperature 20–50 °C) to investigate how it acts as a hardener for alkali silicate adhesive. The silicon phosphate was found to be hydrolyzed with a resulting release of orthophosphate ion, soluble silicate ions, and colloidal silica under mild conditions; the decomposition rate increased with decreasing the particle size of the phosphate and with increasing the pH and temperature of the buffer solution. From the analysis of the decomposition rate on the basis of the shrinking core model, it was found that the decomposition rate could be adequately expressed by the rate equation based on the mixed control of diffusion through a residual layer and surface chemical reaction. This indicates that a part of the colloidal silica which resulted from the hydrolysis remains on the surface of the silicon phosphate particle and then partially limits the overall rate of the hydrolysis. The ...