Spectrophotometric method for the determination of 1,2-propylene glycol

A spectrophotometric method is proposed for the determination of 1,2-propylene glycol. It is based on the ADH/ AlDH catalyzed oxidation of propylene glycol by NAD⁺. The NADH formed is measured at 340 nm. Alcohol dehydrogenase from equine liver was found to be much more effective than that of yeast. No enantiomeric selectivity for s(+) propylene glycol was observed. A linear relation was found in the concentration range from 5 to 50 mg/L. The method achieves a correlation coefficient of r = 0.996 and a relative standard deviation of 1.37%. The limit of quantitation was calculated to 9.6 mg/L. Since the total reaction volume was restricted to 800 μL, only 2.8 units of AlDH and 8 units of ADH were sufficient to develop the final absorption within 30 min. Received: 16 April 1997 / Revised: 19 June 1997 / Accepted: 25 June 1997     

Enthalpy characteristics of L-asparagine interaction with glycerol, ethylene glycol, and 1,2-propylene glycol in aqueous solutions

Integral dissolution enthalpies ??_sol H ^m of L-asparagine in the mixtures of water with glycerol, ethylene glycol, and 1,2-propylene glycol at the concentration of organic solvents up to 0.24 mole fraction were measured by the calorimetry method. The standard enthalpies of dissolution (??_sol H ⁰) and transport (??_tr H ⁰) of amino acids from water to the mixed solvents were derived. The calculated enthalpy coefficients of the molecule pair interactions of L-asparagine-cosolvent are positive, except for the amino acid-glycerol-water system. The data obtained are interpreted in terms of prevalence of different types of interactions in solution and effect of the cosolvent nature on the thermochemical characteristics of the L-asparagine dissolution.     

Abraham model correlations for describing solute transfer into anhydrous 1,2-propylene glycol for neutral and ionic species

Experimental solubility, acid-dissociation constants (pK_a) and activity coefficient data have been compiled from the published pharmaceutical and chemical literature for neutral organic molecules and ionic species dissolved in anhydrous 1,2-propylene glycol. The compiled experimental data were transformed into molar solubility ratios, water-to-anhydrous propylene glycol (P) and gas-to-anhydrous propylene glycol (K) using standard thermodynamic relationships. The derived Abraham model correlations described the observed solubility and partition coefficient data of neutral organic compounds and ionic species to within 0.18 log units and 0.18 log units (or less), respectively.     

Thermochemical characteristics of the interaction of L-cysteine with glycerol,ethylene glycol,and 1,2-propylene glycol in aqueous solutions

Integral enthalpies of dissolution Δ_sol H ^m of L-cysteine in mixtures of water with glycerol, ethylene glycol, and 1,2-propylene glycol at concentrations of organic solvents of up to 0.37 mole fraction were measured by calorimetry of dissolution. The standard values of the dissolution enthalpies (Δ_sol H°) and the transfer enthalpies (Δ_tr H°) of amino acid from water to the mixed solvent were calculated. It was shown that the calculated enthalpic coefficients of the pair interactions of L-cysteine with cosolvent molecules have positive values. The obtained data are interpreted from the viewpoint of the prevalence of different types of interactions in the solutions and influence of the cosolvents nature on the thermochemical characteristics of amino acid dissolution.     

Thermochemical characteristics of interactions of DL-alanine in aqueous solutions of glycerol, ethylene glycol, and 1,2-propylene glycol

The method of dissolution calorimetry was used to measure the integral enthalpy of dissolution ??_sol H ^m of DL-alanine in mixtures of water with glycerol, ethylene glycol, and 1,2-propylene glycol at a concentration of organic solvent up to 0.32 mole fraction. The standard dissolution enthalpy (??_sol H ⁰) and transport enthalpy of amino acids from water to mixed solvent (??_tr H ⁰) were calculated. The calculated enthalpy coefficients of pair interactions of the DL-alanine molecules with the polyol molecules are positive and less than these values for L-alanine. The effect of interactions of different types in solution and the structural features of biomolecules and co-solvents on the enthalpy of dissolution characteristics of amino acids were considered.     

Thermochemical investigation of interaction of L-serin with glycerol,ethylene glycol,and 1,2-propylene glycol in aqueous solutions

By the method of dissolution calorimetry integral enthalpies of dissolution Δ_sol H ^m of L-serine are measured in the mixtures of water with glycerol, ethylene glycol, and 1,2-propylene glycol at the concentration of the organic solvent up to 0.42 mole fraction. The standard values of enthalpies of dissolution (Δ_sol H ⁰) and transfer (Δ_tr H ⁰) of amino acids from water to mixed solvents are calculated. The calculated values of the enthalpy coefficients of pair interactions of L-serine with the molecules of co-solvents are positive. The data obtained are interpreted in terms of prevalence of different types of interactions in solutions and the influence of nature of co-solvents on the thermochemical characteristics of the dissolved amino acids.     

Selective detector of 1,2-propylene glycol dinitrate, 1, propylene glycol mononitrate,and 2-propylene glycol mononitrate using gas chromatography/ thermal energy analyzer or liquid chromatography/ electrochemical detection

Mono- and di-nitrated propylene glycols can be separated and detected using either a gas chromatogph equipped with a nitro-specific thermal energy analyzer (g.c./t.e.a.) or a high-performance liquid chromatograph equipped with an electrochemical detector in the reductive mode (l.c./e.c.). The g.c./t.e.a. exhibits a linear range of three orders of magnitude and provides detection limits in the μg ml^?1 range or lower for these three compounds. The l.c./e.c. provides a linear response over two orders of magnitude and is best suited for the determination of propylene glycol dinitrate. Trapping of these glycols on Amberlite XAD-2 resin is discussed.     

Synthesis of propylene carbonate from urea and 1,2-propylene glycol over ZnO/NaY catalyst

Propylene carbonate (PC) was produced from 1,2-propylene glycol (1,2-PG) and urea in a continuous-flow fixed bed reactor over heterogeneous ZnO catalyst supported on NaY. Among different ZnO loadings of ZnO/NaY catalysts, 5 wt% ZnO loadings of ZnO/NaY showed the highest activity. Characterization and reaction results indicated that the catalysts with a balanced strength of acid and base sites performed well for the synthesis of propylene carbonate from urea and 1,2-PG.     

Spectrophotometric determination of chromium with 1,2-diaminocyclohexanetetraacetic acid

Chromium(III) forms a water-soluble complex with DCTA. The violet complex has maximum absorbance at 540 mμ and obeys Beer's law from 2 to 150 μg chromium per ml. The molar extinction coefficient is 245. Determinations of copper and chromium, cobalt and chromium, and nickel and chromium in presence of each other are described. The complex contains chromium and the reagent in a ratio of 1 : 1. The stability constant of the complex is 1.9·10²².     

Standard enthalpies of dissolution of L-alanine in the water solutions of glycerol, ethylene glycol, and 1,2-propylene glycol at 298.15 K

The integral enthalpies of dissolution Δ_sol H ^m of L-alanine in mixtures of water with glycerol, ethylene glycol, and 1,2-propylene glycol under the concentration of organic solvents up to 0.32 mole fraction were measured by means of calorimetry. The standard values of the dissolution enthalpies (Δ_sol H ^o) and transfer enthalpies (Δ_tr H ^o) of amino acids from water to the mixed solvent were calculated. It was shown that the calculated enthalpic coefficients of pair interactions of L-alanine with cosolvent molecules have positive values. The data obtained are interpreted from the viewpoint of prevalence of different types of interactions in the solutions and influence of the cosolvents nature on the thermo-chemical characteristics of amino acid dissolution.     

Spectrophotometric determination of the pH scale in ethane-1,2-diol

A highly selective method is described for the determination of gallium at the ppm-level in manganese nodules and geological reference samples. After dissolution of the sample, gallium is adsorbed on Dowex 1 (chloride form) from hydrochloric acid solution containing titanium trichloride, which reduces iron(III) so that it is not adsorbed. After elution with dilute nitric acid and evaporation, gallium is determined by atomic-absorption spectrometry with an air-acetylene flame.     

介孔分子筛MCM-41负载磷钨酸催化合成香兰素1,2-丙二醇缩醛

以香兰素和1,2-丙二醇为原料,以介孔分子筛MCM-41负载磷钨酸为催化剂,环己烷为带水剂,合成了香兰素1,2-丙二醇缩醛.考察了醛醇物质的量比、反应时间、带水剂用量、催化剂用量及负载量对产率的影响.实验表明,介孔分子筛MCM-41负载磷钨酸是合成香兰素1,2-丙二醇缩醛的理想催化剂,较优反应条件为:n(香兰素)∶n(1,2-丙二醇)=1∶2.4,负载量为50%,催化剂用量为反应物总质量的2.0%,带水剂环己烷15mL,回流反应2.0h,香兰素1,2-丙二醇缩醛的收率达92%以上.     

Spectrophotometric method for the determination of telmisartan with congo red

In pH 2.50 HCl-NaAc buffer solution, the reaction between telmisartan and congo red could form ionassociation complex, which has the maximum absorbance at 593 nm in the spectrophotometric experiment. Under this wavelength, the Beer’s law was obeyed within the concentration range of 1.08 × 10⁻⁶−2.24 × 10⁻⁵ M. The linear regression equation was A = −0.1913 × 10⁵ c + 0.0286 (C: M). The regression coefficient r was 0.9986. The apparent molar coefficient ɛ₅₉₃ was 1.63 × 10⁴ L mol⁻¹ cm⁻¹ and the detection limit was 5.66 × 10⁻⁷ M. The established method having high sensitivity and good selectivity could be applied to the determination of telmisartan in pharmaceutical, urine and blood plasma samples with satisfactory results. The reaction mechanism was also discussed by using density functional theory methods. The result obtained was consilient with experimental data. The article is published in the original.)     

Spectrophotometric method for phosphine residue determination in coriander

Spectrophotometric method for the determination of phosphine (PH₃) residues in coriander has been developed based on the reaction of phosphine with silver nitrate in 2% aqueous isopropanol. The yellow chromophore formed has an absorption maximum at 430 nm and the linear relation between the absorbances at 430 nm and the concentration of PH₃ is obeyed in the range of 0.02 to 0.17 g. The method is sensitive with a detection limit of 0.008 g and can be applied for determination of 0.02 g/g residue in coriander. Recovery of added PH₃ from a closed system ranges from 96 to 101%.