Norfloxacin (>98%), resorcinol (>99%), and toluene (>99.5%) were purchased from Sigma Aldrich (Darmastadt, Germany). Norfloxacin was a mixture of polymorph A, polymorph C, and the sesquihydrate Form I (Ref Code PUZGAT). See Figure S1 for further details [31 (link)].
The following chemicals were used to prepare buffer solutions: ethylenediamine (>98.8%) from J. T. Baker (Radnor, PA, USA), and trifluoroacetic acid (>99%) and acetic acid (>99%) from Merck (Darmastadt, Germany). To reach the desired pH value, 1 M sodium hydroxide Titrisol® or 0.5 M hydrochloric acid Titrisol®, also from Merck, were added.
For the dissolution rate determination, the following reagents were used: dimethyl sulfoxide (>99.9%, DMSO), potassium dihydrogen phosphate (>99.5%), 0.5 M potassium hydroxide Titrisol®, and 0.5 M hydrochloric acid Titrisol®, all from Merck. Potassium chloride (>99%) was from Sigma.
For HPLC quantification, acetonitrile (HPLC gradient-grade) from Fisher Scientific (Hampton, NH, USA) and a mixture of sodium dihydrogen phosphate monohydrate (>99%) and disodium monohydrogen phosphate (>99%) from Merck were used.
Water was purified by a Milli-Q plus system from Millipore (Bedford, MA, USA), with a resistivity of 18.2 MΩ cm.
The following chemicals were used to prepare buffer solutions: ethylenediamine (>98.8%) from J. T. Baker (Radnor, PA, USA), and trifluoroacetic acid (>99%) and acetic acid (>99%) from Merck (Darmastadt, Germany). To reach the desired pH value, 1 M sodium hydroxide Titrisol® or 0.5 M hydrochloric acid Titrisol®, also from Merck, were added.
For the dissolution rate determination, the following reagents were used: dimethyl sulfoxide (>99.9%, DMSO), potassium dihydrogen phosphate (>99.5%), 0.5 M potassium hydroxide Titrisol®, and 0.5 M hydrochloric acid Titrisol®, all from Merck. Potassium chloride (>99%) was from Sigma.
For HPLC quantification, acetonitrile (HPLC gradient-grade) from Fisher Scientific (Hampton, NH, USA) and a mixture of sodium dihydrogen phosphate monohydrate (>99%) and disodium monohydrogen phosphate (>99%) from Merck were used.
Water was purified by a Milli-Q plus system from Millipore (Bedford, MA, USA), with a resistivity of 18.2 MΩ cm.