Barbiturates titration

It is, however, more likely that the discrepancies observed in the periodate oxidation of malonaldehyde concern mainly the hydroxylation step. In the mechanism proposed (5) for this reaction, it is the enol form of malonaldehyde which is hydroxylated. However, titrations of a solution of malonaldehyde, prepared by hydrolysis of an aqueous solution (33) of carefully distilled 1, 3, 3-tri-ethoxypropene (46, 47), both with strong base and with iodine, indicate that only about 80% of the enol form is present in the equilibrium solution. On the other hand, the thio-barbituric acid test (58, 59) gave consistently higher values for the malonaldehyde content of the solution. The fact that only about 80% of the enol form is present in the equilibrium solution is all the more important as it can be shown (56) by titration with strong base that the enolization is slow, and moreover does not seem to go to completion. 

Other methods for the determination of chlorine in seawater or saline waters are based on the use of barbituric acid [13] and on the use of residual chlorine electrodes [ 14] or amperometric membrane probes [15,16]. In the barbituric acid method [12], chlorine reacts rapidly in the presence of bromide and has completely disappeared after 1 minute. This result, which was verified in the range pH 7.5-9.4, proves the absence of free chlorine in seawater. A study of the colorimetric deterioration of free halogens by the diethylparaphenylene-diamine technique shows that the titration curve of the compound obtained is more like the bromine curve than that of chlorine. The author suggests... 

A plethora of weakly acidic pharmaceutical substances may be titrated effectively by making use of a suitable non-aqueous solvent with a sharp end-point. The wide spectrum of such organic compounds include anhydrides, acids, amino acids, acid halides, enols (viz., barbiturates), xanthines, sulphonamides, phenols, imides and lastly the organic salts of inorganic acids. 

Deaths, cardiac and resp have been reported during initiation and conversion of pain pts to methadone Tx from Tx w/ other opioids Uses Severe pain detox w/ maint of narcotic addiction Action Narcotic analgesic Dose Adults. 2.5-10 mg IM q3-8h or 5-15 mg PO q8h titrate as needed Feds. 0.7 mg/kg/24 h PO or IM -s- q8h T slowly to avoid resp depression X in renal impair Caution [B/D (prolonged use/high doses at term), + (w/ doses =/> 20 mg/24 h)], severe liver Dz Disp Tabs, inj SE Resp depression, sedation, constipation, urinary retention, T QT interval, arrhythmias Interactions T Effects W/ cimetidine, CNS depressants, protease inhibitors EtOH T effects OF anticoagulants, antihistamines, barbiturates, glutethimide, methocarbamol ... 

Elemental composition K 60.05%, C 18.44%, N 21.51%. An aqueous solution of the salt is analyzed for potassium (see Potassium) and for CN by a cyanide ion-selective electrode. The solution must be diluted appropriately for measurement. Alternatively, CN may be titrated by the pyridine-barbituric acid colorimetric method (see Hydrogen Cyanide.)... 

Non-aqueous titration of acidic groups is carried out in pharmacopoeial assays of barbiturates, uracils and sulphonamides. 

The uses of constant-current coulometry for the determination of drugs in biological fluids are few, basically due to sensitivity restriction. Monforte and Purdy [46] have reported an assay for two allylic barbituric acid derivatives, sodium seconal and sodium sandoptal, with electrogenerated bromine as the titrant and biamperometry for endpoint detection. Quantitative bromination required an excess of bromine hence back titration with standard arsenite was performed. The assay required the formation of a protein-free filtrate of serum with tungstic acid, extraction into chloroform, and sample cleanup by back extraction, followed by coulometric titration with electrogenerated bromine. The protein precipitation step resulted in losses of compound due to coprecipitation. The recoveries of sodium seconal and sodium sandoptal carried through the serum assay were approximately 81 and 88%, respectively. Samples in the concentration range 7.5-50 pg/mL serum were analyzed by this procedure. 

Furthermore, CD was used to assess the stability of assemblies having the same /Tm but with slightly different chemical structure. CD titrations with THF of chiral double rosette assemblies lc 3(l)EB)6 and 1c 3(BuCYA)6 in CHC13 showed values of xthf = 10% and xthf = 95%, respectively, as predicted taking in account the higher strength of the cyanurate H-bonds when compared with barbiturates. 

Some examples are titration of Pb2+ with CrO -, Ni2+ with diacetyl-dioxime, and barbituric acids with Hg2(C104)2. 

Quantitative investigation of recognition of this pair of liposomes was performed with isothermal titration microcalorimetry (ITC). It has been found that one-to-one binding between adenine and barbituric acid in the lipid/water/lipid interface occurs. However at T= 58°C, above the main lipid phase transition, the situation is different and no liposomal binding is detected. This is mainly due to the molecular disorder within the bilayer (liquid-disordered/liquid ordered phase coexistence) that limits the capacity of complementary moieties to bind, due to the weakening of the hydrogen bonds at these high temperatures. 

Sulfonamides in mixtures have been determined by titration with 0.02 M chloramine-T after bromination. The ortho dibromination is prevented by acetylation of the aromatic amino group but the reaction of side-chain substituents remains unaffected. The relative standard deviations are about 1%. Interferences even in small amounts, from barbituric acid, isoniazid, ascorbic acid, methionine, thymol and penicillins are observed (33). 

In the solid (crystalline) form the barbituric acid exists in the triketo or lactam form. In aqueous solution tautomerism to the enolic lactim occurs the enolic hydroxyl (at C-2) is acidic acid and is ionized according to the particular drug s pKa (e.g., pentobarbital = 8.0, phenobarbital = 7.5). Titrating such a solution with a stoichiometric equivalent of base such as NaOH will convert the lactam quantitatively to the barbiturate s sodium salt, which can be isolated. Many barbiturates are commercially produced both in the lactam and in the sodium enolate salt form. Of course, the salts are water soluble and thus are used to formulate injectable dosage forms including those for IV anesthetic use. 

Barbituric acid, 5,5 -nitrilodi-, monoammonium salt EINECS 221-266-6 Murexide Naples red NSC 215208 2,4,6(1H,3H,5H)-Pyrimidinetrione, 5-((hexahydro-2,4,6-trioxo-5-pyrimid-inyl)imino)-, monoammonium salt. A red basic dyestuff, now obsolete, obtained by the action of nitric acid upon guano, and subsequently treating the product with ammonia. Used as an indicator in complexometric titrations. Crystals slightly soluble in H2O, insoluble in organic solvents km = 520 nm (H2O),... 

In photometric titration cyanide ions are transformed into cyanogen chloride in the course of the reaction with chloroamine to form a red-violet compound in the presence of pyridine and barbituric acid at pH 4-5. Absorbance is measured at a wavelength of 580 nm. The method is suitable for the determination of cyanides at concentrations > 0.002 mg 1 [14,19, 63, 64]. 

Miyaji T, Kurono Y, Uekama K, Ikeda K, Simultaneous determination of complexation equilibrium constants for conjugated guest species by extended potentiometric titration Method On barbiturate-y -cyclodextrin system. Chem. Pharm. Bull. 1976 24 1155-1159. 

A colour test, specific for barbituric and thiobarbituric acids in amounts greater than 0-5 pg, uses pyridyl pyridinium dichloride as the colour reagent [111]. The quantitative determination of barbituric acid in the presence of several 5,5-disubstituted derivatives, by means of ultraviolet spectroscopic determinations and titrations in chloroform-methanol mixtures, has b n described [112]. 

Receptor 15 has been designed for the complexation of barbiturates [ref 17]. The syndiesis was accomplished by Ba -templated macrocyclization of the appropiate dialdehyde and cis-l,2-cyclohexanediamine, followed by reaction with uranyl acetate. NMR experiments in CDCI3 revealed that intramolecular self-complexation takes place and a constant Kg if-ass for this process of IS has been estimated. The association constants of three barbiturates could be determined by NMR titrations in a mixture of CDC13 and DMSO-dg (95 5). The association constants of dimethyl, diethyl, and ethylphenyl barbituric acid are 112, 97, and 45 Imol respectively. It is obvious that a sterically more demanding barbiturate results in a lower association constant. The host 15 is able to transport barbituric... 

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