A comparison of methods for the extraction of smectites from calcareous rocks by acid dissolution techniques

Clay Minerals ◽  
1992 ◽  
Vol 27 (1) ◽  
pp. 73-80 ◽  
Author(s):  
R. J. Cook
Keyword(s):  
Sodium Acetate ◽  
Acetate Buffer ◽  
Acetate Buffer Solution ◽  
Exchangeable Cation ◽  
Lithium Acetate ◽  
Buffer Solution ◽  
Acid Dissolution ◽  
Sodium Acetate Buffer Solution ◽  
Octahedral Cations ◽  
Bulk Chemistry

AbstractFour methods of extracting clays from calcite-rich samples were compared: (i) sodium acetate buffer solution; (ii) lithium acetate buffer solution; (iii) hydrochloric acid; (iv) liquid cation-exchange acid. The methods were tested on mixtures consisting of 80% calcite, 10% quartz and 10% hectorite. Potassium had previously been exchanged on to the interlayer sites of the clay. XRD traces of the extracted clays appeared identical with those of the original clays except for a sharpening of the 001 reflection. The bulk chemistry of the clay was unchanged except by the HCl extraction, which appeared to cause a stripping of the octahedral cations. With all of the methods the exchangeable cation content was altered; the sodium acetate method, for example, retained only 17% of the original exchangeable K+, the other methods all retaining <10%.

scholarly journals Stability of Sulfonamides, Nitrofurans, and Chloramphenicol Residues in Preserved Raw Milk Samples Measured by Liquid Chromatography

2002 ◽  
Vol 85 (6) ◽  
pp. 1415-1419 ◽  
Author(s):  
Mario Noa ◽  
Norma Perez ◽  
Rey Gutierrez ◽  
Irma Escobar ◽  
Gilberto Diaz ◽  
...  
Keyword(s):  
Liquid Chromatography ◽  
Cold Storage ◽  
Sodium Acetate ◽  
Raw Milk ◽  
Acetate Buffer ◽  
Acetate Buffer Solution ◽  
Sodium Acetate Buffer ◽  
Buffer Solution ◽  
Milk Samples ◽  
Sodium Acetate Buffer Solution

Abstract A stability study was made of 10 antimicrobials: 6 sulfonamides, 3 nitrofurans, and chloramphenicol residues in raw milk samples preserved with 0.1% potassium dichromate (K2Cr2O7) and 0.05% mercuric bichloride (HgCl2) during cold storage for 7 days. Preserved milk samples fortified with 50 ppb of each antimicrobial were analyzed by liquid chromatography (modified AOAC Method 993.32). Drugs were extracted with chloroform–acetone after solvent evaporation residues were dissolved with aqueous sodium acetate buffer solution (0.02M, pH 4.8), and fat was removed with hexane. Sulfonamides and chloramphenicol were detected at 275 nm (UV) by using a gradient system of sodium acetate buffer solution–acetonitrile starting at 95 + 5 (v/v) and finishing at 80 + 20 (v/v). Nitrofurans were detected at 375 nm (UV) isocratically with sodium acetate buffer solution–acetonitrile (80 + 20, v/v). Residues stability was measured through recovery data. Sulfamethoxazole, sulfachloropyridazine, nitrofurazone, furazolidone, and furaltadone residues remained stable in the presence of either preservative for 7 days. Sulfamethazine and chloramphenicol were not affected by K2Cr2O7, but had significant losses ( p &lt;0.05) when HgCl2 was used: 26.2 and 13.4%, respectively. Average recoveries of sulfamonomethoxine, sulfamerazine, and sulfathiazole significantly decreased by Day 7, with losses of 17.1, 17.2, and 23.2% for K2Cr2O7, and 23.3, 20.7, and 48.0% for HgCl2, respectively. During 5 days of cold storage all antimicrobials tested, except sulfathiazole, remained stable in milk samples preserved with 0.1% K2Cr2O7 or 0.05% HgCl2.

scholarly journals Liquid Chromatographic Determination of Multiple Sulfonamides, Nitrofurans, and Chloramphenicol Residues in Pasteurized Milk

2002 ◽  
Vol 85 (1) ◽  
pp. 20-24 ◽  
Author(s):  
Norma Perez ◽  
Rey Gutierrez ◽  
Mario Noa ◽  
Gilberto Diaz ◽  
Hector Luna ◽  
...  
Keyword(s):  
Sodium Acetate ◽  
Chromatographic Determination ◽  
Acetate Buffer ◽  
Acetate Buffer Solution ◽  
Gradient System ◽  
Sodium Acetate Buffer ◽  
Buffer Solution ◽  
Pasteurized Milk ◽  
Sodium Acetate Buffer Solution ◽  
Liquid Chromatographic

Abstract A rapid and selective liquid chromatographic method was developed to detect 6 sulfonamides, 3 nitrofurans, and chloramphenicol residues in pasteurized milk. The 10 drugs were extracted with chloroform–acetone and the organic phase was evaporated; the residues were dissolved in an aqueous sodium acetate buffer solution 0.02M (pH = 4.8), and the fat was removed by washing with hexane. The aqueous layer was collected, filtered, and injected. The 6 sulfonamides and chloramphenicol were detected at 275 nm ultraviolet (UV) using a gradient system starting with sodium acetate buffer solution–acetonitrile (95 + 5) and finishing with sodium acetate buffer solution–acetonitrile (80 + 20). Nitrofurans were detected at 375 nm (UV) isocratically with sodium acetate buffer solution–acetonitrile (80 + 20). For 50 ppb fortified milk, the average recoveries were (sulfathiazole) 65.52%; (sulfamerazine) 75.36%; (sulfamethazine) 93.94%; (sulfachlorpyridazine) 75.94%; (sulfamethoxazole) 85.18%; (sulfamonomethoxine) 83.45%; (chloramphenicol) 104.17%; (nitrofurazone) 91.81%; (furazolidone) 100.76%; and (furaltadone) 72.38%. Method detection limits ranged from 4 ppb (nitrofurazone) to 16 ppb (sulfamethazine). Some matrix interferences (3–7 ppb) were observed only with sulfonamides.

Enzymatic hydrolysis of chitosan in acetate buffer solution

2015 ◽  
Vol 88 (4) ◽  
pp. 647-651 ◽  
Author(s):  
V. V. Chernova ◽  
A. S. Shurshina ◽  
M. V. Bazunova ◽  
E. I. Kulish
Keyword(s):  
Enzymatic Hydrolysis ◽  
Acetate Buffer ◽  
Acetate Buffer Solution ◽  
Buffer Solution ◽  
Hydrolysis Of

Collaborative Study of an Ultraviolet Method for Measuring Diquat Content in Formulations

1968 ◽  
Vol 51 (6) ◽  
pp. 1304-1305
Author(s):  
A A Carlstrom
Keyword(s):  
Systematic Error ◽  
Random Error ◽  
Coefficient Of Variation ◽  
Collaborative Study ◽  
Acetate Buffer ◽  
Acetate Buffer Solution ◽  
Buffer Solution ◽  
Standard Curve ◽  
Two Samples

Abstract The ultraviolet method for diquat described by Yuen, Bagness, and Myles in 1967 was collaboratively studied with formulations containing 2 lb diquat/gal. A portion of the sample is diluted with an acetate buffer solution and the absorbance is measured at 310 mμ the diquat content is obtained by reference to a standard curve prepared from known diquat concentrations. Single determinations on two samples by thirteen collaborators show an overall coefficient of variation of 2.4%. The coefficient of variation for random error is 1.0%, and for systematic error 1.6%. The method is recommended for adoption as official, first action.

Preparation and characterization of a poly-o-phenylenediamine film modified glassy carbon electrode as a H2O2 sensor

2013 ◽  
Vol 91 (11) ◽  
pp. 1077-1084 ◽  
Author(s):  
Wenying Zhai ◽  
Xiuying Tian ◽  
Yun Yan ◽  
Yuehua Xu ◽  
Yuechun Zhao ◽  
...  
Keyword(s):  
Cyclic Voltammetry ◽  
Glassy Carbon Electrode ◽  
Glassy Carbon ◽  
Electrochemical Impedance ◽  
Monomer Concentration ◽  
Acetate Buffer ◽  
Acetate Buffer Solution ◽  
Carbon Electrode ◽  
Modified Glassy Carbon Electrode ◽  
Buffer Solution

A poly-o-phenylenediamine film modified glassy carbon electrode (PoPD/GC) was successfully prepared by cyclic voltammetry in acetate buffer solution. The polymerization mechanism of oPD is discussed. The impedance behavior and morphology of the PoPD membrane were characterized using cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy, respectively. It is discovered that the PoPD/GC prepared only in acetate buffer solution had dual electrocatalytic activity toward the oxidation and reduction of H2O2. The optimal buffer solution pH, scanning rate, monomer concentration, and number of scannings for film forming were 4.2, 0.05 V s−1, 6.0 mmol L−1, and 30, respectively. The linear ranges between the anodic (Δia) or cathodic (Δic) current and H2O2 concentration were 0.07−1.0 × 104 and 0.04−4.5 × 104 μmol L−1, respectively. The corresponding calibration curves were Δia (μA) = 8.03c (mmol L−1) + 6.36 (n = 18, R2 = 0.9989) and Δic (μA) = −5.52c (mmol L−1) − 0.77 (n = 18, R2 = 0.9990) with a detection limit of 0.03 and 0.02 μmol L−1 (S/N = 3), respectively. The PoPD/GC prepared in the optimal conditions showed good stability and quick response (<0.2 s) to H2O2, which was successfully applied to the determination of H2O2 in real water samples with satisfactory results.

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