scholarly journals Determination of Catalyst Surface Acidity in Liquids by a Pulse Liquid Chromatographic Technique

2005 ◽  
Vol 23 (9) ◽  
pp. 739-749 ◽  
Author(s):  
Paolo Carniti ◽  
Antonella Gervasini ◽  
Serena Biella
Keyword(s):  
Surface Acidity ◽  
Lower Amount ◽  
Chromatographic Technique ◽  
Solvent Flow Rate ◽  
Acidic Sites ◽  
Catalyst Acidity ◽  
Set Up ◽  
Liquid Chromatographic

A pulse liquid chromatographic technique, set up by using an HPLC apparatus, is proposed for the characterization of the surface acidity of solid acids in liquids in view of their use as catalysts in liquid–solid reactions. Dosed amounts of solutions of two different basic probe molecules (2-phenylethylamine, pKa = 9.84 and aniline, pKa = 4.63) in solvents of different polarity were injected onto solid samples (acidic resins, Amberlites and a mixed silica–zirconia oxide) at a constant solvent flow rate. Titration with the weakest basic probe (aniline) rather than 2-phenylethylamine generally led to a lower amount of acidic sites. The amount of acidic sites determined at the surface was greatly affected by the solvent. With silica–zirconia, a higher amount of acidic sites was established by titration in apolar rather than polar solvents. The results have been compared with those obtained by conventional methods, i.e. ion exchange employing salts and, for silica–zirconia, Hammett titrations. The quite satisfactory results obtained are of some importance in establishing valuable relationships between catalyst acidity and catalytic activity in various solvents.

scholarly journals ANALYTICAL METHOD DEVELOPMENT AND VALIDATION OF ATOMOXETINE HYDROCHLORIDE USING RAPID HIGH-PERFORMANCE LIQUID CHROMATOGRAPHIC TECHNIQUE

2018 ◽  
Vol 11 (11) ◽  
pp. 118
Author(s):  
Zubaidur Rahman ◽  
Vijey Aanandhi M ◽  
Sumithra M
Keyword(s):  
High Performance ◽  
Method Development ◽  
High Sensitivity ◽  
High Performance Liquid Chromatographic ◽  
Hplc Method ◽  
Chromatographic Technique ◽  
Pharmaceutical Dosage Form ◽  
Rp Hplc ◽  
Liquid Chromatographic

Objective: A simple, novel, sensitive, rapid high-performance liquid chromatographic (RP-HPLC) method has been developed and validated for quantitative determination of atomoxetine HCl (ATH) in bulk and formulations.Methods: The chromatographic development was carried out on RP-HPLC. The column used as Xterra RP 18 (250 mm × 4.6 mm, 5 μ particle size), with mobile phase consisting of methanol: water 80:20 V/V. The flow rate was 1.0 mL/min and the effluents were monitored at 270 nm.Results: The retention time was found to be 5.350 min. The method was validated as per International Conference on Harmonization Guideline with respect to linearity, accuracy, precision, and robustness. The calibration curve was found to be linear over a range of 2–10 μg/mL with a regression coefficient of 0.9999. The method has proved high sensitivity and specificity.Conclusion: The results of the study showed that the proposed RP-HPLC method was simple, rapid, precise and accurate which is useful for the routine determination of ATH in bulk drug and in its pharmaceutical dosage form.

scholarly journals Direct Injection Liquid Chromatographic Technique for Simultaneous Determination of Two Antihistaminic Drugs and Their Main Metabolites in Serum

2007 ◽  
Vol 90 (2) ◽  
pp. 384-390 ◽  
Author(s):  
Samy Emara ◽  
Alaa El-Gindy ◽  
Mostafa K Mesbah ◽  
Ghada M Hadad
Keyword(s):  
Human Serum ◽  
Simultaneous Determination ◽  
Chromatographic Technique ◽  
Simple Liquid ◽  
Good Precision ◽  
Active Metabolites ◽  
Serum Samples ◽  
Antihistaminic Drugs ◽  
Liquid Chromatographic

Abstract A very simple liquid chromatographic technique was developed and validated for the simultaneous determination of 2 antihistaminic drugs, loratadine (LT) and terfenadine (TR), and their major active metabolites, desloratadine (DL) and fexofenadine (FX), respectively, in human serum. LT, DL, TR, and FX from directly injected serum samples were enriched on a protein-coated RP8 silica precolumn (10 4.6 mm id) while serum constituents, such as proteins and salts, were eluted to waste. Using an online column-switching system, the drugs and their metabolites were quantitatively transferred and separated on a second analytical column (Shim-pack 5 μm particle size cyanopropyl, 250 × 4.6 mm id) followed by ultraviolet detection at 243 nm for LT and DL and 220 nm for TR and FX. Very good precision, accuracy, and linearity were obtained over the range of 101000 ng/mL for LT and DL, 10500 ng/mL for TR, and 103000 ng/mL for FX in human serum. High extraction recoveries from serum ranging from 96.03 to 98.19, 95.44 to 97.26, 95.61 to 98.17, and 95.60 to 97.89 for LT, DL, TR, and FX, respectively, were obtained.

Synthesis and Structural Characterization of Ca14NbxIn1-xAs11 (x ≈ 0.85)

2016 ◽  
Vol 257 ◽  
pp. 147-151 ◽  
Author(s):  
Yi Wang ◽  
Svilen Bobev
Keyword(s):  
Physical Properties ◽  
Side Reaction ◽  
Structure Type ◽  
Major Product ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ongoing Work ◽  
Set Up

Single-crystals of the new compound Ca14NbxIn1–xAs11 have been obtained from a solid-state reaction in a sealed Nb ampoule. The initial experiment had been set up with the aim to investigate the effect of electron doping (via In) on the crystal structure and physical properties of Ca14MnAs11. Subsequent single-crystal X-ray diffraction and elemental analysis work suggested that instead of Ca14MnxIn1–xAs11, the major product of the reaction is the phase Ca14NbxIn1–xAs11. This supposition was corroborated when the title compound was synthesized from a reaction of Ca, In and As in a sealed Nb ampoule, proving that, 1) Mn metal is not included in the structure, and 2) that the inadvertent side reaction of As with the walls of the Nb container is the source of the niobium. The overall structure is isotypic with the tetragonal Ca14AlSb11 structure type (space group I41/acd), although some marked differences between the two must be noted. Current ongoing work is focused on the synthesis of phase pure polycrystalline samples and determination of the physical properties of this unusual transition metal Zintl phase.

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