Fabrication of novel bone haemostasis sheet by using sugar-containing hydroxyapatite and plant-derived polymer

The fabrication conditions of bone-haemostasis sheet were examined by using (i) phosphoryl oligosaccharides of calcium (POs-Ca), sugar-containing hydroxyapatite ( s -Ca 10 (PO 4 ) 6 (OH) 2 : s -HAp) derived from POs-Ca and (ii) natural plant-derived polymers (locust bean gum (LBG), guar gum (GG) and alginate (AG)). The sol, which had been prepared by dissolving 2 mass% LBG/GG and 2 mass% AG into 200 cm 3 deionized water and then by agitating at the speed of 20 000 r.p.m., was immersed into 3 mass% POs-Ca solution at room temperature for 24 h; it was hydrothermally treated at 100°C for 5 h, and then freeze-dried at −50°C for 24 h to form porous composite sheet. The microscopic observation showed that the pore sizes were controlled in the range of 5–100 µm by the optimization of LBG/GG ratio. The composite sheet showed the noted uptake of simulated body fluid (1426%) at 37.0°C and also the human blood. Thus, the porous composite sheet was found to be a promising candidate of the bone haemostasis, on the basis of the data of haemostasis, uptake ability of SBF and solubility in acetic acid–sodium acetate buffer solution.

Solubility of Magnesium-Containing β-Tricalcium Phosphate: Comparison with that of Zinc-Containing β-Tricalcium Phosphate

The purpose of this study was to determine the solubility of magnesium-containing tricalcium phosphate (MgTCP) over a magnesium content range from 0 to 10 mol%, and to compare it with that of zinc-containing tricalcium phosphate (ZnTCP). MgTCP powders with various Mg contents were immersed in 0.08M acetic acid and sodium acetate buffer solution of pH 5.5 at 25±2 °C. Solubility product, Ksp = (Ca2+)3-x(Mg2+)x(PO4 3-)2, was calculated. From the Ksp data, the solubility of MgTCP in the pH range from 5 to 7.5 was inversely calculated. The solubility of MgTCP decreased with increasing Mg content. The negative logarithm of solubility product (Ksp) was regressed as pKsp = 29.041+0.90467C-0.18069C2+0.025962C3-0.00192C4-0.000055199C5 , where C is the Mg content of MgTCP in mol%. In the magnesium content range from 0 to 10 mol%, the solubility of MgTCP is higher than that of ZnTCP containing the same amount of zinc.

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

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 <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.

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

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.

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

Four 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%.