Citric acid

About: Citric acid is a research topic. Over the lifetime, 17745 publications have been published within this topic receiving 277125 citations. The topic is also known as: citrate & H3cit.

Iron(III) citrate speciation in aqueous solution.

Abstract: Citrate is an iron chelator and it has been shown to be the major iron ligand in the xylem sap of plants. Furthermore, citrate has been demonstrated to be an important ligand for the non-transferrin bound iron (NTBI) pool occurring in the plasma of individuals suffering from iron-overload. However, ferric citrate chemistry is complicated and a definitive description of its aqueous speciation at neutral pH remains elusive. X-Ray crystallography data indicates that the alcohol function of citrate (Cit4−) is involved in Fe(III) coordination and that deprotonation of this functional group occurs upon complex formation. The inability to include this deprotonation in the affinity constant calculations has been a major source of divergence between various reports of iron(III)–citrate affinity constants. However the recent determination of the alcoholic pKa of citric acid (H4Cit) renders the reassessment of the ferric citrate system possible. The aqueous speciation of ferric citrate has been investigated by mass spectrometry and EPR spectroscopy. It was observed that the most relevant species are a monoiron dicitrate species and dinuclear and trinuclear oligomeric complexes, the relative concentration of which depends on the solution pH value and the iron : citric acid molar ratio. Spectrophotometric titration was utilized for affinity constant determination and the formation constant for the biologically relevant [Fe(Cit)2]5− is reported for the first time.

Injectable non-immunogenic cartilage and bone preparation

Abstract: Ground bone or cartilage particles are demineralized by extraction with a low ionic strength buffer such as 20 mM HEPES containing a chelating agent and protease inhibitors, then extracted with an acidic solution such as 0.3 M citric acid, pH 4.0, containing protease inhibitors. The extracted material generally contains less than 2 % by weight phosphate and less than 100 mM calcium. The phosphate content can be further reduced by treatment of the matrix with acid phosphatase, which removes residual organic phosphate. The material is useful in a method of treatment of vesicoureteral reflux and other disorders where a bulking agent is effective in correcting the defect.

Modified resin–intermediate processing of perovskite powders: Part I. Optimization of polymeric precursors

Abstract: The formation of a polyester between citric acid (CA) and ethylene glycol (EG) was found to be a decisive factor for the foaming of resin intermediates in a Pechini-type powder process. This process was modified by changing the organic mass ratio of CA/EG which results in ceramic powders with different morphologies. The most porous resin intermediate (with or without chelated cations) was prepared using a polymeric gel made of equimolar citric acid and ethylene glycol. It was also found that a premixing of organic components, prior to adding constituent nitrate solutions, makes the whole process more controllable.