Diclofenac acid, 2-[(2,6-dichlorophenyl)amino]benzeneacetic acid, is a non-steroidal anti-flammatory drug. The structures of two monoclinic forms of diclofenac acid with space groups of P21/c (HD1) and C2/c (HD2) were reported by Castellari and Ottani. 1 In this paper, we report on a new orthorhombic form of diclofenac acid (HD3) with the space group Pcan.Diclofenac sodium, a sodium salt of 2-[(2,6-dichlorophenyl)amino]benzeneacetic acid (2 g) was dissolved in water. The solution was acidified with 1 M HCl until a white precipitate of diclofenac acid was observed. The precipitate was filtered, washed with distilled water and dried in vacuo. The precipitate (HD3) was recrystallized from hot methanol by slow evaporation. X-ray diffraction data were collected at room temperature using a Bruker SMART CCD area detector. The collected data were reduced using SAINT, 2 and an empirical absorption correction was performed using SADABS. 3 A total of 19487 reflections were measured, of which 4267 reflections (R(int) = 0.1079) were unique. The structure was solved by direct methods and refined with anisotropic displacement parameters for all non-hydrogen atoms by full-matrix least-squares using the SHELX-97 package for PC. 4 The coordinates of the hydrogen atoms were calculated from the riding model, except Fig. 2 Molecular structure of diclofenac acid. Thermal ellipsoids are drawn at the 50% probability level.

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A simple, rapid, and sensitive colorimetric assay for ascorbic acid (AA) was developed based on poly(methacrylic acid)‐stabilized silver nanoclusters (PMAA‐AgNCs). The AgNCs were prepared via a single‐step synthesis exploiting PMAA as both a reducing agent and a stabilizer. The sensing capability of this method is based on the color change associated with the growth in size of AgNCs, which turn into nanoparticles, resulting from the reduction of free Ag+ present in AgNCs solution to Ag0 by AA. In the presence of AA, an apparent surface plasmon resonance absorption peak of the silver nanoparticles was observed at 430 nm, and its intensity increased linearly with AA concentration, so that a solution color change could be observed with the naked eye. The proposed method exhibited a linear working concentration range of 0.25–100 μM and a detection limit of 95 nM. The sensor was employed to determine AA concentration in fruit juice and vitamin C tablet samples, affording results of high accuracy.

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