Increasing the rate of the hydrogen evolution reaction in neutral water with protic buffer electrolytes

Electrocatalytic generation of H2 is challenging in neutral pH water, where high catalytic currents for the hydrogen evolution reaction (HER) are particularly sensitive to the proton source and solution characteristics. A tris(hydroxymethyl)aminomethane (TRIS) solution at pH 7 with a [2Fe-2S]-metallopolymer electrocatalyst gave catalytic current densities around two orders of magnitude greater than either a more conventional sodium phosphate solution or a potassium chloride (KCl) electrolyte solution. For a planar polycrystalline Pt disk electrode, a TRIS solution at pH 7 increased the catalytic current densities for H2 generation by 50 mA/cm2 at current densities over 100 mA/cm2 compared to a sodium phosphate solution. As a special feature of this study, TRIS is acting not only as the primary source of protons and the buffer of the pH, but the protonated TRIS ([TRIS-H]+) is also the sole cation of the electrolyte. A species that is simultaneously the proton source, buffer, and sole electrolyte is termed a protic buffer electrolyte (PBE). The structure–activity relationships of the TRIS PBE that increase the HER rate of the metallopolymer and platinum catalysts are discussed. These results suggest that appropriately designed PBEs can improve HER rates of any homogeneous or heterogeneous electrocatalyst system. General guidelines for selecting a PBE to improve the catalytic current density of HER systems are offered.

P23 Tolerability of prednisolone and dexamethasone in children in saudi arabia and the united kingdom

BackgroundCorticosteroids are used to treat conditions including acute asthma and croup where they are often given in short-courses. This study evaluated the tolerability and palatability of oral prednisolone and dexamethasone in children in Saudi Arabia (SA) and the UK.MethodsA prospective observational/interview study was performed. Palatability was evaluated by asking patient/parent’s opinions of the taste and acceptability of the medication. Children pointed at the appropriate face on a scale depicting: 1 ‘dislike very much’, 2 ‘dislike a little’, 3 ‘not sure’, 4 ‘like a little’ and 5 ‘like very much’.1 Tolerability, in particular nausea, vomiting and abdominal pain was evaluated by direct questioning of the patient/parents after each administration. Data was collected over three months in each centre. Patients aged 2–18 years treated with oral prednisolone or dexamethasone in hospital were approached to participate.ResultsIn SA, 122 patients (89 asthma, 33 croup), aged 2–10 years (mean=4.3) were recruited: 52 received prednisolone base tablets; 37 prednisolone sodium phosphate syrup; 33 dexamethasone elixir. In the UK, of 133 patients (80 asthma, 53 croup) aged 2–16 years (mean=4.9): 38 received prednisolone base tablets; 42 prednisolone sodium phosphate soluble tablets; 53 dexamethasone sodium phosphate oral solution.SA: Day 1 prednisolone base tablet palatability scores: 1 (88.5%); 2 (11.5%). Day 2 scores: 1 (64.4%); 2 (28.9%); 3 (6.7%). Day 1 prednisolone sodium phosphate solution palatability scores: 1 (48.6%); 2 (40.5%); 3 (10.8%). Day 2 scores: 1 (10.8%); 2 (67.6%); 3 (21.6%). Day 1 dexamethasone elixir palatability scores: 1 (27.3%); 2 (48.5%); 3 (24.2%).UK: Day 1 prednisolone base tablet palatability scores: 1 (76.3%); 2 (13.1%); 3 (5.3%); 4 (5.3%). Day 2 scores: 1 (61.3%); 2 (19.4%); 3 (16.1%); 4 (3.2%). Day 1 prednisolone sodium phosphate soluble tablet palatability scores: 1 (35.7%); 2 (26.2%); 3 (23.8%); 4 (11.9%) 5 (2.4%). Day 2 scores: 1 (16.7%); 2 (58.2%); 3 (16.7%); 4 (4.2%); 5 (4.2%). Day 1 dexamethasone sodium phosphate solution palatability scores: 1 (5.7%); 2 (28.3%); 3 (37.7%); 4 (17%); 5 (11.3%).Dexamethasone sodium phosphate solution had the highest palatability scores (P<706;0.0001). The score was lowest for prednisolone base tablets in both centres (P<0.0001).In SA prednisolone base tablets were associated with more cases of nausea (24 vs 7) and vomiting (5 vs 0) than prednisolone sodium phosphate syrup (p=0.008 and p=0.073 respectively). In the UK vomiting occurred significantly more frequently with prednisolone base tablets (8) than prednisolone sodium phosphate soluble tablets (2) (p=0.041).In both centres dexamethasone was associated with less side effects but with no significant difference between the formulations. Vomiting (1 vs 0), nausea (7 vs 3) and abdominal pain (10 vs 8) occurred more with dexamethasone sodium phosphate solution than dexamethasone elixir (p=1, p=0.53 and p=0.55 respectively).ConclusionsDexamethasone sodium phosphate solution was the most palatable preparation. Prednisolone base tablets were rated the least palatable and were also the least well tolerated. Palatability scores seemed to improve with second doses.ReferenceH. Hames H, Seabrook JA, Matsui D, Rieder MJ, Joubert GI. A palatability study of a flavoured dexamethasone preparation versus prednisolone liquid in children. Can. J. Clin. PharmacolJanuary 2008;15(1):e95–8.

Observational study on the palatability and tolerability of oral prednisolone and oral dexamethasone in children in Saudi Arabia and the UK

BackgroundShort-course oral corticosteroids are routinely used to treat acute asthma and croup. We evaluated their tolerability and palatability in Saudi Arabian (SA) and UK children.MethodsProspective observational/interview study (3 months in each country). Palatability was evaluated using a 5-point facial Hedonicscale and tolerability by direct questioning of patient/parents.ResultsIn SA, of 122 patients (2–10 years) recruited, 52 received prednisolone base tablets, 37 prednisolone sodium phosphate syrup and 33 received dexamethasone elixir. In the UK, of 133 patients (2–16 years), 38 received prednisolone base tablets (mainly crushed and dispersed), 42 prednisolone sodium phosphate soluble tablets and 53 received dexamethasone sodium phosphate oral solution.In both countries, dexamethasone had the highest palatability scores (SA mean: 1.97; UK mean: 3) and prednisolone base tablets had the lowest (SA mean: 1.12; UK mean: 1.39). Palatability scores improved for all formulations of prednisolone with each subsequent daily dose.In SA, prednisolone base tablets were associated with more nausea (24vs7 patients) and vomiting (5vs0 patients) than sodium phosphate syrup (p=0.008 and p=0.073, respectively). In the UK, vomiting occurred more frequently with prednisolone base (8 patients) than sodium phosphate soluble tablets (2 patients) (p=0.041).In both centres, dexamethasone was associated with less side effects. Vomiting (1vs0 patients), nausea (7vs3 patients) and abdominal pain (10vs8 patients) occurred more with dexamethasone sodium phosphate solution than dexamethasone elixir.ConclusionsDexamethasone sodium phosphate solution was the most palatable preparation. Prednisolone base tablets were rated least palatable and were least well tolerated. Palatability scores improved with each dose taken.

Removing Thallium (I) Ion from Aqueous Solutions Using Modified ZnO Nanopowder

In this study, the adsorption of thallium (I) ion as a dangerous pollutant from aqueous solution onto modified ZnO nanopowder as a fairly cheap adsorbent has been examined in batch mode. It was known that modification of the adsorbent was necessary to reach a significant adsorption percentage. The adsorbent used here was modified by sodium phosphate solution. The effect of experimental conditions such as initial pH of solution, contact time, adsorbent dosage, initial concentration of thallium and temperature is studied. The results showed the dependence of the adsorption percentage to these conditions specially its pH. The maximum adsorption percentage of Tl (I) ions at 25±1oC was 92.8%. Freundlich isotherm model provided a better fit with the experimental data than Langmuir and Temkin isotherm models by high correlation. Separation factor, RL, values showed that modified ZnO nanopowder was favorable for the adsorption of Tl (I) ion. The negative value of ΔH0 showed that Tl (I) sorption is an exothermic process and the negative value of ΔS0 represented that there is a little decrease of randomness at the solid-solution interface during sorption.