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Orthophosphoric Acid (orthophosphoric + acid)
Selected AbstractsComparison of three methods for the extraction of arsenic compounds from the NRCC standard reference material DORM-2 and the brown alga Hijiki fuziformeAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 6 2001Doris Kuehnelt Abstract The NRCC standard reference material DORM-2 and the marine brown alga Hijiki fuziforme were extracted with water, methanol/water (9,+,1), and 1.5 M orthophosphoric acid. The extracts from DORM-2 were analyzed by HPLC,ICP-MS for arsenobetaine, arsenocholine, trimethylarsine oxide, and the tetramethylarsonium cation and the extracts from H. fuziforme for arsenous acid, arsenic acid, dimethylarsinic acid, methylarsonic acid, and four arsenoriboses. Almost no differences between the three extractants were observed when DORM-2 was investigated. Only arsenobetaine was slightly better extracted with 1.5 M orthophosphoric acid or methanol/water (9,+,1) than with water. The sum of all extractable compounds (arsenobetaine, the tetramethylarsonium cation, and a formerly unknown compound recently identified as the trimethyl(2-carboxyethyl)arsonium ion) accounted for 94% of the total arsenic when 1.5 M orthophosphoric acid was used, for 92% when methanol/water (9,+,1) was used, and for 87% when water was used. Significant differences in the extraction yields obtained for the alga were observed for arsenic acid and one of the arsenoriboses (,glycerol-ribose'). Orthophosphoric acid removed twice as much of this ribose from the algal material than water and three times more than methanol/water (9,+,1). Arsenic acid was 1.2 times better extracted with orthophosphoric acid than with water and ten times better than with methanol/water (9,+,1). Almost no differences in the extraction yields were found for dimethylarsinic acid and the other three riboses. Orthophosphoric acid extracted 76%, water 65%, and methanol/water 33% of the total arsenic from H. fuziforme. Copyright © 2001 John Wiley & Sons, Ltd. [source] Cytotoxicity of substances leached or dissolved from pulp capping materialsINTERNATIONAL ENDODONTIC JOURNAL, Issue 8 2005B. N. Cavalcanti Abstract Aim, To evaluate the cytotoxic effects of substances leached or dissolved from pulp capping materials on human pulp fibroblasts. Methodology, The substances were applied to cell cultures in conditioned media. The experimental groups were: GI (control; n = 24) , cultures treated with fresh medium; GII (n = 24) , cultures treated with calcium hydroxide cement; GIII (n = 24) , cultures treated with adhesive resin and GIV (n = 24) , cultures treated with 37% orthophosphoric acid. The media were conditioned by placing the crude materials in contact with fresh culture medium for 1 h. The cytotoxicity analysis was performed using the Trypan blue dye exclusion assay at times of 0, 6, 12 and 24 h for cell viability assay, and at 1, 3, 5 and 7 days for survival assay. Data were treated by anova (P < 0.05) and Tukey's test (P < 0.05). Results, GI and II presented similar cell viability and cell growth. GIII and IV exhibited statistically significant lower percentages of cell viability: GIV only at the 0 h experimental time, whereas in GIII this viability markedly diminished reaching values of 10% by 12 h. Cell growth was impaired only in cultures of GIII. Conclusions, Substances dissolved from the adhesive system tested were cytotoxic for human dental pulp fibroblasts in culture, whilst substances leached from calcium hydroxide were biocompatible. [source] A new chemical method of synthesis of modified nucleoside [32P]phosphatesJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 8 2008D. V. Yanvarev Abstract A simple method of chemical phosphorylation for modified nucleosides with [32P]orthophosphoric acid in the presence of BrCN is described. The yields of 5,-[32P]nucleoside monophosphates achieved are 50,65% at nominal specific radioactivities of ca. 1000,Ci/mmol. The mechanism of phosphorylation in the presence of heterocyclic amines is studied. Copyright © 2008 John Wiley & Sons, Ltd. [source] Monetite (CaHPO4) Synthesis in Ethanol at Room TemperatureJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2009A. Cuneyt Tas A straightforward process was developed to synthesize monetite (CaHPO4, dicalcium phosphate anhydrous) powders at room temperature (21°±1°C) in ethanol solutions. The process reported here constitutes an alternative to well-publicized monetite synthesis procedures based on the dehydration of brushite (CaHPO4·2H2O, dicalcium phosphate dihydrate) powders either in acidic, hot (70°,95°C) aqueous solutions or in drying ovens (200°,225°C). Submicrometer monetite powders were synthesized in ethanol (ethyl alcohol) solutions containing small aliquots of concentrated H3PO4 (orthophosphoric acid, 85%). Precipitated CaCO3 (calcium carbonate, calcite form) powders with submicrometer particles were simply stirred in the above solutions in glass bottles for 3 h. The starting Ca/P molar ratio in the synthesis bottles was 0.50. Monetite powders obtained with a stacked-nanosheets particle texture did not contain any unreacted CaCO3. Monetite powders were also found to have the ability to completely transform into apatitic (apatite-like) calcium phosphate powders when soaked in calcium-containing saline solutions (i.e., 142 mM Na+, 5 mM K+, and 50 mM Ca2+ in water) for 6 days at 37°C. [source] Synthesis, Characterization and Ionic Conductive Properties of Phosphorylated Chitosan MembranesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 5-6 2003Ying Wan Abstract Phosphorylated chitosan membranes were prepared from the reaction of orthophosphoric acid and urea on the surface of chitosan membranes in N,N -dimethylformamide. Their ionic conductivity in the wet state was investigated. Chemical modifications contributed to improved ionic conductivities of the chitosan membranes. Compared to the unmodified chitosan membranes, it was found that hydrated phosphorylated chitosan membranes with an appropriate phosphorus content showed an increasing ionic conductivity of about one order of magnitude. The phosphorylation reaction mechanism was explained based on 13C and 31P NMR measurements. It was also observed that the crystallinity of the phosphorylated chitosan membranes and the corresponding swelling indices were changed pronouncedly, but these membranes did not lose either their tensile strength or thermal stability to a significant degree in comparison with the unmodified chitosan membranes. Possible reaction mechanism for preparation of phosphorylated chitosan membranes. [source] Comparison of three methods for the extraction of arsenic compounds from the NRCC standard reference material DORM-2 and the brown alga Hijiki fuziformeAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 6 2001Doris Kuehnelt Abstract The NRCC standard reference material DORM-2 and the marine brown alga Hijiki fuziforme were extracted with water, methanol/water (9,+,1), and 1.5 M orthophosphoric acid. The extracts from DORM-2 were analyzed by HPLC,ICP-MS for arsenobetaine, arsenocholine, trimethylarsine oxide, and the tetramethylarsonium cation and the extracts from H. fuziforme for arsenous acid, arsenic acid, dimethylarsinic acid, methylarsonic acid, and four arsenoriboses. Almost no differences between the three extractants were observed when DORM-2 was investigated. Only arsenobetaine was slightly better extracted with 1.5 M orthophosphoric acid or methanol/water (9,+,1) than with water. The sum of all extractable compounds (arsenobetaine, the tetramethylarsonium cation, and a formerly unknown compound recently identified as the trimethyl(2-carboxyethyl)arsonium ion) accounted for 94% of the total arsenic when 1.5 M orthophosphoric acid was used, for 92% when methanol/water (9,+,1) was used, and for 87% when water was used. Significant differences in the extraction yields obtained for the alga were observed for arsenic acid and one of the arsenoriboses (,glycerol-ribose'). Orthophosphoric acid removed twice as much of this ribose from the algal material than water and three times more than methanol/water (9,+,1). Arsenic acid was 1.2 times better extracted with orthophosphoric acid than with water and ten times better than with methanol/water (9,+,1). Almost no differences in the extraction yields were found for dimethylarsinic acid and the other three riboses. Orthophosphoric acid extracted 76%, water 65%, and methanol/water 33% of the total arsenic from H. fuziforme. Copyright © 2001 John Wiley & Sons, Ltd. [source] | |||||||||||||