Highly fluorescent nitrogen-doped carbon quantum dots prepared using sucrose and urea: Green synthesis, characterization, and use for determination of torsemide in its tablets and plasma samples.

A simple and facile microwave-assisted method was developed for the synthesis of highly fluorescent nitrogen-doped carbon quantum dots (N-CQDs) using sucrose and urea. The produced quantum dots exhibited a strong emission band at 376 nm after excitation at 216 nm with quantum yield of 0.57. The as-prepared N-CQDs were characterized using Fourier-transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) images, and ultraviolet-visible (UV-visible) spectra. The average particle size was 7.7 nm. It was found that torsemide (TRS) caused an obvious quenching of the fluorescent N-CQDs; so, they were used for its spectrofluorometric estimation. An excellent linear correlation was found between the fluorescence quenching of N-CQDs and the concentration of the drug in the range of 0.10 to 1.0 µg/mL with limit of quantitation (LOQ) of 0.08 µg/mL and limit of detection (LOD) of 0.027 µg/mL. The method was successfully applied for the assay of the drug in its commercial tablets and spiked human plasma samples, and the results obtained were satisfactory. Complex GAPI was used for greenness assessment of the analytical procedures and the pre-analysis steps. Interference likely to be introduced from co-administered drugs was also studied.

Spectrofluorometric determination of cinacalcet hydrochloride: greenness assessment and application to biological fluids andin-vitrodissolution testing.

A facile, simple, green and sensitive spectrofluorometric method was developed for determination of the calcimimetic drug cinacalcet hydrochloride. It is used for the treatment of hyperparathyroidism. The drug showed high native fluorescence intensity at 320 nm after excitation at 280 nm. The method was linear over the range of 5.0-400.0 ng ml-1with excellent correlation (R2= 0.9999). Limit of detection (LOD) and limit of quantitation (LOQ) values were 1.19 and 3.62 ng ml-1, respectively. The percentage recovery was found to be 100.42% ± 1.39 (n=8). The proposed method was successfully applied for determination of cinacalcet in spiked human plasma samples with % recoveries of (87.23 to 109.69%). Two recent greenness metrics (GAPI and Analytical Eco-Scale) were chosen to prove the eco-friendly nature of the method. Furthermore, the proposed method was successfully applied to dissolution study of commercial cinacalcet tablets. The interference likely to be introduced by some commonly co-administrated drugs such as metoprolol and itraconazole was studied; the tolerance limits were calculated.

Estimation of Two Diuretics Using Fluorescent Nitrogen Doped Carbon Quantum Dots: Application to Spiked Human Plasma and Tablets.

Highly fluorescent nitrogen doped carbon quantum dots (N-CQDs) were prepared by a single-step method based on microwave heating of cane sugar and urea. The produced N-CQDs were applied as nano-sensors for the spectrofluorimetric determination of eplerenone and spironolactone. A strong emission band at 376 nm was obtained after excitation at 216 nm due to the produced N-CQDs. The native fluorescence of N-CQDs was obviously quenched upon adding increased concentrations of each drug. A strong correlation was found between the fluorescence quenching of N-CQDs and the concentration of each drug. The method was found to be linear over the range of 0.5 to 5.0 µg/mL for eplerenone and 0.5 to 6.0 µg/mL for spironolactone with LOQ of 0.383 µg/mL and 0.262 µg/mL. The developed method was further extended for determination of both drugs in their pharmaceutical tablets and spiked human plasma. The results obtained were statistically compared with those of reported methods. The mechanism of fluorescence quenching of N-CQDs by the two drugs was discussed.

Use of green fluorescent nano-sensors for the determination of furosemide in biological samples and pharmaceutical preparations.

BACKGROUND: Carbon quantum dots (CQDs) are new class of carbon nanoparticles. Recently, they have been widely used as fluorescent probes due to their easy accessibility, optical properties and chemical inertness. Many available precursors are used in the synthesis of carbon quantum dots. The electrical and optical properties of CQDs could be enhanced by doping hetero atoms such as nitrogen or sulfur into their structure. OBJECTIVE: The current work presents the synthesis and characterization of water-soluble nitrogen doped carbon quantum dots (N-CQDs) and their use as fluorescent nano-sensors for the spectrofluorimetric determination of furosemide in its pharmaceutical preparations and spiked human plasma. METHODS: A domestic microwave was used to prepare the N-CQDs by heating a solution of sucrose and urea till complete charring (about ten minutes). The produced N-CQDs exhibit a strong emission band at 376 nm after excitation at 216 nm. Furosemide caused a quantitative quenching in the fluorescence intensity of the produced N-CQDs. RESULTS: The proposed method was validated according to ICH Guidelines. The method was found to be linear over the range of 0.1-1.0 µg/mL with LOQ of 0.087 µg/ml. CONCLUSION: Ecofriendly nano fluorescent sensors (N-CQDs) were successfully synthesized. The size of N-CQDs was distributed in the range of 6.63 nm to 10.23 nm with an average of 8.2 nm. The produced N-CQDs were used as fluorescent probes for the estimation of furosemide in its pharmaceutical preparations as well as spiked human plasma samples.

Two spectroscopic methods for estimation of anti-migraine medications: Sumatriptan and Zolmitriptan based on nucleophilic substitution reaction.

Sensitive and selective spectrophotometric and spectrofluorimetric methods have been developed for the estimation of two anti-migraine drugs, namely sumatriptan succinate (SUM) and zolmitriptan (ZOL). These methods depend on producing a yellow-coloured product after the reaction of the two drugs with 7-chloro-4-nitrobenz-2-oxa-1,3-diazole (NBD-Cl). The reaction products exhibited maximum absorbance at 481 nm in borate buffer of pH 9 and fluorescence emission peak at 540 nm after excitation at 470 nm for the two drugs. The linear ranges were 5-60 µg/ml for SUM and 5-50 µg/ml for ZOL in the spectrophotometric method (Method I), whereas this was 0.4-4 µg/ml for SUM and 0.5-5 µg/ml for ZOL in the spectrofluorimetric method (Method II). The method validity was assessed according to International Council for Harmonisation (ICH) guidelines. Statistical analysis of the results obtained from the proposed and comparison methods confirmed that the proposed methods were highly accurate and precise. The suggested methods could be used for the determination of the mentioned drugs in both pure form and in tablets.

Spectrofluorimetric investigation for determination of sumatriptan succinate: application to tablets and spiked human plasma.

A simple and highly sensitive spectrofluorimetric method for the estimation of sumatriptan succinate has been investigated. The suggested method depends on the determination of the intrinsic fluorescence properties of the drug in aqueous systems at λem 350 nm following λex at 225 nm. The linearity range was 10-100 ng/ml, with a detection limit and quantitation limit of 1.2 and 3.6 ng/ml, respectively. The suggested method was sufficiently successful for determination of sumatriptan its pharmaceutical tablets as well as in spiked human plasma. Moreover, the validation parameters were determined following International Council for Harmonisation guidelines. Statistical analysis of the obtained results from the proposed and reference methods showed no significance difference between the two methods regarding accuracy and precision.