Showing papers on "Reagent published in 1980"

Spectrophotometric determination of ammonia: a study of a modified Berthelot reaction using salicylate and dichloroisocyanurate

Abstract: A reaction scheme for the spectrophotometric determination of ammonia by means of a modified Berthelot reaction is proposed, in which salicylate, dichloroisocyanurate and complex cyanides are the principal reagents. The experimental results presented are consistent with, and support, the reaction scheme proposed. It is suggested that the complex cyanides act on two stages of the reaction, firstly to stabilise monochloramine at pH values (12–13) at which it is normally unstable and hence facilitate the formation of 5-aminosalicylate from salicylate (this step is the rate determining step of the reaction), and secondly, to accelerate the oxidative coupling of 5-aminosalicylate with salicylate to form the indophenol dye [possibly via a hexacyanoferrate(III) intermediate]. It is shown that the optimum pH of reaction is a result of a complex inter-relationship of a number of equilibria and it thus remains necessary to optimise the pH value for each combination of reagents used. The implications of this study on the choice of reagents for the determination of ammonia by the Berthelot reaction are noted.

Novel reagent system for converting a hydroxy-group into an iodo-group in carbohydrates with inversion of configuration. Part 2

Abstract: Isolated primary and secondary hydroxy-groups in carbohydrate derivatives are transformed into iodo-groups with inversion of configuration on treatment with either triphenylphosphine, iodine, and imidazole or triphenyl-phosphine and 2,4,5-tri-iodoimidazole at elevated temperatures. At lower temperatures, primary hydroxy-groups may be selectively replaced by iodo-groups.

Determination of atmospheric sulfur dioxide without tetrachloromercurate(II) and the mechanism of the Schiff reaction

Abstract: Formaldehyde (7 mM) buffered at pH approx. 4 is used to stabilize atmospheric SO/sub 2/ as hydroxymethanesulfonic acid. Equilbrium data for the above reaction are presented. Sulfite, liberated from the compound by base, is added to acidic pararosaniline for color development by the Schiff reaction, and absorbance is measured at 580 nm. The procedure has been optimized with regard to acidity and reagent concentrations. The method is comparable to the West-Gaeke method in absorption and recovery efficiency, sensitivity, and precision. No unusual interferences are observed due to O/sub 3/, NO/sub 2/, and transition-metal ions, except Mn(II). A novel ion chromatographic procedure to determine hydroxymethanesulfonate and sulfate in the same sample is also described. Enhancement of sensitivity in the colorimetric method by solvent extraction has been studied. Investigations into the mechanism of the Schiff reaction and structure of the products have established the validity of the alkylsulfonic acid theory. Mechanistically an aminocarbinol seems to be the first intermediate, which undergoes subsequent nucleophillic substitution by bisulfite ion. To account for the high absorptivity of the product, we suggest that the sulfonic acid group is significantly ionized.

Multi-purpose blood diluent and lysing agent for differential determination of lymphoid-myeloid population of leukocytes

Abstract: A method and reagent system is described for differential determination of more that one class of leukocyte populations, using an automatic blood cell analyzer. The reagent system includes a blood diluent and stromatolyzing reagent. The blood diluent is an osmotically balanced aqueous solution of ingredients for maintaining erythrocyte morphology, blood cell stabilizing, buffering and bacteriostatic action. The stromatolyzing reagent is a mixture of an aqueous solution of quaternary ammonium salts, a chromagen forming agent and an additive which is a non-cationic surfactant. The quaternary ammonium salts, with the additive, serve the purpose of positioning, relative to one another and a volume reference point, the lymphoid and myeloid populations. The additive also acts to prevent or to reduce the amount of protein deposit in the sensing orifices of the analyzer, which deposit tends to accumulate from the cell debris resulting from blood cell stromatolyzation.

Monoclonal Anti‐A from a Hybrid‐Myeloma: Evaluation as a Blood Grouping Reagent

Abstract: A monoclonal anti-A antibody has been evaluated and found suitable for use as a potent routine ABO grouping reagent, without the use of additives. The IgM anti-A (MH2/6D4) is secreted into the tissue culture supernatant by a permanent line of cloned cells derived by fusion of anti-A producing spleen cells and a mouse myeloma cell line. This is a cost-effective reagent which should reduce production costs by over 50%. This reagent has the advantages inherent in monoclonal antibodies among them the availability of unlimited quantities of unvarying antibody of known properties.

A coupled-enzyme equilibrium method for measuring urea in serum: optimization and evaluation of the AACC study group on urea candidate reference method.

Abstract: We describe a coupled-enzyme equilibrium method for measuring urea in serum, which is performed on supernates prepared by treating each specimen with Ba(OH)2 and ZnSO4 (Somogyi reagent). Analytical recovery of [14C]urea added to a variety of matrices was essentially complete (mean, 100.6%) for the supernates after precipitation. Nine variables were univariately examined in arriving at the reaction conditions for the method: glutamate dehydrogenase, urease, 2-oxoglutarate, ADP, Tris . HCI, NADH, EDTA, pH, and temperature. The reagent is stable for at least 48 days at--20 degrees C and for 23 days at 4 degrees C. Mean analytical recovery of urea (14 mmol/L) added to seven different specimens (three different matrices) was 100.8%. The analytical linear range of the method extends to 30 mmol of urea per liter. Of 22 potential interferents, only bilirubin at 1 mmol/L (580 mg/L), hemoglobin at 10 g/L, and hydroxyurea at 6 mmol/L showed more than 2% interference. We discuss precision and effects of specimen dilution, and compare results for 100 human serum specimens with those measured for the same specimens with four other urea methods. We examined the effects of measuring a blank, consisting of sample and reagent without urease, with each specimen.

Synthesis and characterization of poly/glutaraldehyde/ - A potential reagent for protein immobilization and cell separation

Abstract: The aldol condensation of aqueous glutaraldehyde in the pH range 7-13.5 yielded water-soluble and water-insoluble poly(g1utaraldehyde) (PGL), the molecular weight of which was of the order of 12 to 20000. The structure of PGL was elucidated by means of UV, IR spectrophotometry, electrochemical studies, and the analysis of reaction products of PGL with hydroxylamine hydrochloride. The structure of PGL polymers prepared in a wide pH range was found to be similar. The main differences consisted of changes in the concentration of functional groups. Sufficient evidence was obtained to explain the presence in PGL of the primary hydroxyl and of the carboxyl groups as due to a Cannizzaro reaction. Electrochemical studies confirmed the spectrophotometric evidence of the presence of conjugated aldehyde groups. Recent investigations of water-soluble or -insoluble PGL or of PGL in the form of microspheres indicate that these polymers may yield important immunoreagents for biological research. Glutaraldehyde has many applications in different areas. It is used as a protein cross-linking agent,' for fixation of living cells2 or t i ~ s u e s , ~ and for sterilization of hospital e q ~ i p m e n t ; ~ it was also found to serve as an efficient binding agent of antibodies to micro sphere^.^ Glutaraldehyde was used in a variety of reactions for relatively long periods of time at physiological pH. It was only recently realized that under these conditions a considerable amount of glutaraldehyde is polymerized through the aldol condensation mechanism,6 and many reported reactions of glutaraldehyde are actually reactions of glutaraldehyde as well as of poly(g1utaraldehyde). Although a large number of studies were carried out in the past on the nature of aqueous gl~taraldehyde,~-'' little information is available on the structure of the solid aldol condensation product which was frequently considered to be an impurity associated with glutaraldehyde.12 The present study showed that polymerization of glutaraldehyde under basic conditions results in the production of water-soluble and -insoluble polymers and that these polymers contain nonconjugated aldehyde, conjugated aldehyde, hydroxyl, and carboxyl groups. The weight ratio of the soluble to the insoluble polymer and the concentration of the functional groups were found to be dependent on the pH of the polymerization medium. Poly(glutara1dehyde) might be used as a new reagent in protein chemistry and other areas. Only recently the polymer was found to constitute a valuable new reagent for the immobilization of antibodies on solid substrate^.'^ Furthermore, a new method was developed for the preparation of poly(glutara1dehyde) in the form of micro~pheres . '~ The microspheres were used for cell labeling and cell separation and are suitable also for immobilization of enzymes, drugs, and proteins. Experimental Section (a) Reagents. The following materials were acquired from commercial sources and were used without any further treatment: pyridine, phthalic anhydride, and hydroxylamine hydrochloride (Matheson Coleman and Bell), fluorescein isothiocyanate (Polysciences), tetraethylammonium perchlorate (Southwestern Analytical Co.), and ferrofluid (Ferrofluidic Co., Burlington, Mass.). Aqueous glutaraldehyde (Aldrich) was purified by treatment with activated carbon followed by filtration. Dimethylformamide, (DMF), dimethyl sulfoxide (Me2SO) and crotonaldehyde were vacuum distilled. (b) Apparatus. Infrared and UV spectra were obtained with a Fourier transform IR (FTS-l5C, Houston Instruments) and a Cary 219 spectrophotometer (Varian), respectively. Gel permeation chromatography (GPC) was carried out with the high-pressure liquid chromatography Model 6000, fitted with a refractive index detector (Water Associates). The GPC was carried out with dimethylformamide as a solvent and a column of styragel lo5, lo4, lo3 8, (pore size); polystyrene was used for calibration. Dupont thermal analyzer 900, Model 950 TGA, was used for thermogravimetric analysis. Polarograms were obtained with a Princeton Applied Research (PAR) Model 174 polarographic analyzer and recorded with a Hewlett Packard Model 7004 x-y recorder. Cyclic voltammograms were obtained by means of a PAR Model 173 potentiostat driven by a conventional signal generator. The voltammograms were recorded with the x-y recorder. Controlled potential coulometry was studied with the PAR Model 173 potentiostat equipped with a Model 179 digital coulometer. The reference calomel electrode was isolated from the main cell compartment by means of a fritted glass disk. The auxiliary electrode was a platinum wire (diameter 0.076 cm) sealed in soft glass. The working electrode was a hanging mercury drop electrode. (c) Synthes is of PGL. Glutaraldehyde was added to an appropriate deaerated buffer solution and then the mixture was placed on a mechanical shaker for 72 h. The white-yellowish precipitated polymer was filtered, washed with water, and then dried under vacuum at 45 \"C. The mother liquor was dialyzed extensively against distilled water and lyophilized in order to obtain the soluble PGL in solid form. The synthesis of PGL microspheres was already described.14 (d) Aldehyde Group Determination. The aldehyde content of PGL was determined from the percent nitrogen of the oxime prepared by the heterogeneous reaction of PGL with aqueous hydroxylamine hydr~chlor ide. '~~ '~ PGL (50 mg) was shaken a t room temperature for 24 h with 500 mg of hydroxylamine hydrochloride. The polymer was then filtered, washed with water, and dried under vacuum a t 45 \"C. A similar nitrogen content was obtained when the reaction was carried out a t 60 \"C or a t room temperature but a t pH 6.0. (e) Carboxy1,Group Determination. The carboxyl content of the polymer in the salt form was determined by ashing the samples and in the acid form by titration of the polymer dissolved in DMF/H20 (1:l) with 0.3 M NaOH. Similar results were obtained when the titration was carried out in warm pyridine. The agreement between the ashing method and the titration method was of the order of 15%. (f) Hydroxyl Group Determination. The determination of the hydroxyl content was based on the phthalation method.17-19

Colorimetric estimation of vitamin A with trichloroacetic acid.

Abstract: Publisher Summary This chapter discusses the use of trichloroacetic acid method for colorific estimation of vitamin A in serum and liver tissue. In this method, trichloroacetic acid crystals (50 g), freshly washed with solvent, are dissolved in alcohol-free distilled chloroform (25 ml). This gives about 50 ml of reagent that is stable for 5 h with daylight excluded. Optical density readings tend to decrease with storage for longer periods, up to 24 h. No color is given by vitamin A with reagent exposed to bright diffuse sunlight for several hours. It is observed with this method that the colors produced from vitamin A, its acetate, and palmitate with the Carr-Price antimony trichloride reagent and trichloroacetic acid reach the same intensity for any given amount of vitamin. The concentration of trichloroacetic acid controls the rate of formation and stability of anhydrovitamin, which may be correlated with loss of vitamin A or its acetate. It is important to observe that change occurs without appearance of blue color in the weaker acid medium. Formation of anhydrovitamin with fine-structure absorption follows protonation of vitamin A, and the slower formation from vitamin A acetate reflects differences in the rates of dehydration and deacetoxylation.

Radioiodination by use of the Bolton-Hunter and related reagents.

Abstract: Publisher Summary This chapter discusses the radioiodination by the use of the Bolton-Hunter and related reagents. Iodinated N -succinimidyl 3-(4-hydroxyphenyl)propionate (Bolton-Hunter reagent) is the first conjugation reagent that has been widely used to prepare tracers for immunoassay. Similar reagents derived from methyl p -hydroxybenzimidate and diazotized aniline have been synthesized and used to iodinate proteins, but not specifically for use in immunoassay. The Bolton-Hunter reagent is a 125 I-labeled acylating agent prepared by the chloramine-T method that reacts spontaneously and under mild conditions primarily with lysine residues. Use of this reagent supplements, the chloramine-T and lactoperoxidase methods, in which radioactive iodide is introduced into the phenol ring of tyrosine or related moieties and to some extent into histidine residues. The Bolton-Hunter reagent is an excellent alternative in case labeling tyrosine that leads to loss of immunoactivity or biological activity, or when the substrate lacks the appropriate group. Since the Bolton-Hunter reagent was introduced, it has been used to label a wide variety of targets, including viruses and cell lysates as well as pure compounds. One of its most important applications has been the preparation of iodinated antigens and hapten derivatives of high specific activity for use in radioimmunoassay.

Improved direct specific determination of serum iron and total iron-binding capacity.

Abstract: Serum iron is released from transferrin and reduced at pH 1.7 by treating serum with a 10 g/L ascorbic acid solution in 0.1 mol/L HCl. When ferrozine is added to this reagent, it forms a complex with iron that is as intensely colored as at higher pH values, and under these conditions no turbidity is produced. The second major interference, that from copper, is eliminated by adding 1 g of thiosemicarbazide per liter, which at a low pH forms a stable, uncolored complex with copper without affecting the reaction of ferrozine with iron.

Automatic analytical apparatus

Abstract: An automatic analytical apparatus which comprises a single reaction line and in which reaction vessels are carried step by step along the reaction line, a sample and reagent are delivered to the reaction vessel during each carrying step to obtain a test liquid, and the test liquid thus obtained is subjected to a photometric operation, characterized by comprising (a) sample and reagent delivering means for delivering the sample and reagent into a plurality of reaction vessels in succession, respectively, during each carrying step of the reaction vessel, and (b) means for subjecting the photometric operation to a plurality of test liquids at separate positions at the same time during each carrying step of the reaction vessel.

One-step synthesis of 5′-azido-nucleosides

Abstract: Regioselective azidation of unprotected or appropriately protected nucleosides was conducted by means of the reagent triphenylphosphine–carbon tetrabromide–lithium azide. By use of this reagent, 5′-azido-5′-deoxynucleosides were prepared conveniently in one step from nucleosides in high yields. Secondary hydroxy-groups of appropriately 5′-protected nucleosides were also converted by the reagent to azido-functions with complete inversion.

An ab initio calculation of the rate constant for the OH+H 2→H2O+H reaction

Abstract: The rate constants for OH+H2 reactions are calculated, using the reagent and saddle point parameters from table I and 6.2 kcal/mole barrier estimate. (AIP)

A New Reagent for Determination of Isocyanates in Working Atmospheres by HPLC Using UV or Fluorescence Detection

Abstract: A new liquid chromatographic method with increased sensitivity has been developed for the determination of isocyanates common in industrial environments The isocyanates are converted to stable urea derivatives by reaction with 9-(N-methylaminomethyl)-anthracene These derivatives were analyzed using high performance liquid chromatography on a bonded octadecylsilyl phase using isocratic elution with acetonitrile/water and detected either by a UV or a fluorescence detector The method was applied to toluene 2, 4- and 2, 6-diisocyanate (2, 4- and 2, 6-TDI), hexamethylene diisocyanate (HDI) and 4, 4-diphenylmethane diisocyanate (MDI) The influence of various salts on the retention of the reagent amine was studied, as well as the separation of the urea derivatives on different C18-phases The detection limit is about 1 · 10−4 mg/m3 for the isocyanates investigated, using either UV or fluorescence detection This means that the new method is ten to twenty times more sensitive than the previously desc

Methyl‐triisopropoxy‐titanium, a highly selective nucleophilic methylating reagent. Preliminary Communication

Abstract: Replacement of lithium or magnesium by titanium can furnish nucleophilic organometallic reagents of high selectivity as exemplified by the title compound 1 (see Tables 1–3).

A phenol‐hypochlorite manual determination of ammonium‐nitrogen in Kjeldahl digests of plant tissue

Abstract: A phenol‐hypochlorite (Berthelot) procedure for determining NH4‐N in acid digests of plant tissue is described. EDTA suppresses Cu interference and precipitation of hydroxides and phosphates. The oxidizing reagent includes an alkaline buffer to account for variations in acidity between digestion solutions, the main source of error in an unbuffered procedure. The reagent combinations and addition sequence employed allow for delays of up to at least 30 minutes between reagent additions without affecting the final colour intensity. The proposed procedure is as sensitive as similar methods used for determining NH4‐N in natural waters and yields results which agree well with those obtained by steam distillation.

2,5-Dimethoxybenzyl alcohol: a convenient self-indicating standard for the determination of organolithium reagents

Abstract: A method for the determination of organolithium reagent is described using 2,5-dimethoxybenzyl alcohol as a self-indicating primary standard.

Reagent for the quantitative determination of water

Abstract: A reagent for the quantitative determination of water in combination with a titration solution containing iodine is described. The reagent contains sulfur dioxide and an anhydrous alkali metal acetate in 2-methoxy ethanol or a mixture of 2-methoxy ethanol and methanol in a volume ratio of at least 10:90. The reagent is characterized in that when it is left to stand no precipitate forms and the increase in control value is kept to a minimum.

1-Benzyl-1,4-dihydronicotinamide as a reagent for replacing aliphatic nitro groups by hydrogen. An electron-transfer chain reaction

Abstract: Die Titelverbindung (II) kann, als Modell von NAD(P)H (reduziertes Nicotinamid-Adenosindinucleotid-phosphat), zur Substitution von aliphatischen Nitrogruppen, z.B. in (I), durch Heingesetzt werden [→(III)].