Sarzamin Khan

Determination of captopril using selective photoluminescence enhancement of 2-mercaptopropionic modified CdTe quantum dots

A photoluminescent probe for the determination of captopril is proposed based on the enhancement of luminescence from 2-mercaptopropionic modified CdTe quantum dots (2-MPA-CdTe QDs). Under optimum conditions, the calibration model (the Langmuir binding isotherm) was linear up to 4.8 × 10−4 mol L−1 with equilibrium binding constant of 3.2 × 104 L mol−1 and limit of detection (xb + 3 sb) of 2.7 × 10−7 mol L−1 (59 ng mL−1). The approach was tested in the determination of captopril in pharmaceutical formulations and the results were in agreement with the ones obtained using reference method. The possible mechanism of interaction is also investigated by Raman and electronic absorption spectroscopy and dynamic light scattering.

Spectrofluorimetric determination of tetrabenazine after photochemical derivatization in basic medium.

Photochemical derivatization is proposed for the spectrofluorimetric determination of tetrabenazine (TBZ). A central composite design was used to adjust experimental conditions (60 min of UV in a 0.45 mol L(-1) NaOH solution) enabling the improvement of the analyte signal-to-blank ratio of one order of magnitude, when compared to the TBZ original fluorescence. Limit of quantification was 4.7×10(-8) mol L(-1) but the detection power can be improved at least 10 times using solid phase extraction that also allows the separation of the analyte from matrix components, enabling the analysis of biologic fluids. Linear range covered at least three orders of magnitude. The combined uncertainty of the determination (at a 5×10(-6) mol L(-1)) was 16%. Recoveries of TBZ in the analyses of a pharmaceutical formulation were in agreement with the ones obtained using a HPLC method. Recovery in saliva (5×10(-7) mol L(-1) of TBZ) was 90±3% (n=3). The procedure minimizes the use of toxic chemical derivatization reagents and the generation of hazardous waste.

Photochemical derivatization of amitriptyline using a green chemistry approach: fluorimetric determination and photochemical reaction mechanism

Intense fluorescence from amitriptyline (AMT) was achieved after photochemical derivatization in an acidic aqueous medium (60 min of UV irradiation of solutions containing 0.027 mol L−1 HCl). After the reaction, fluorescence was significantly enhanced enabling the indirect fluorimetric determination of AMT in drugs and in a pharmacopoeia reference material. The limit of quantification (LOQ) was 1.3 × 10−7 mol L−1 and measurement uncertainty was about 6% at the concentrations close to the LOQ and less than 4% at higher concentrations. The mechanism of the photoreaction was proposed based on the identification of the products and on its kinetics. Studies aiming at the determination of AMT in human serum indicate the potential of the approach as a cheap and simple screening procedure for tricyclic antidepressants.

Gold nanoparticles coupled with graphene quantum dots in organized medium to quantify aminoglycoside anti-biotics in yellow fever vaccine after solid phase extraction using a selective imprinted polymer

HIGHLIGHTSAuNPs were synthesized on a dispersion of GQDs‐amino using NaBH4 as reducing agent.Reaction was made in organized solution containing the cationic surfactant CTAB.Kanamycin amplify photoluminescence from the AuNPs‐GQDs‐amino‐CTAB probe.The instrumental detection limit was 30nmolL−1.Solid phase extraction using an aminoglycoside selective MIP ensured selectivity.Kanamycin was detected in pharmaceutical formulation and in yellow‐fever vaccine. ABSTRACT The determination of kanamycin sulfate was made indirectly by measuring its effect on photoluminescent amino functionalized graphene quantum dots (GQDs‐amino) associated with gold nanoparticles (AuNPs) that were produced by the reduction of AuCl4 with NaBH4 in an aqueous dispersion of GQDs‐amino (obtained by the pyrolysis of citric acid and glutathione) also containing the cationic surfactant CTAB. The AuNPs‐GQDs‐amino‐CTAB system presents a suppressed photoluminescence that is amplified in the presence of kanamycin. Under optimized experimental conditions, the photoluminescence amplification of the nanomaterial system showed a linear response as a function of kanamycin concentration, covering three orders of magnitude (10−7 to 10−5molL−1). The use of solid phase extraction with a cartridge packed with aminoglycoside selective molecularly imprinted polymer ensured selectivity in determinations made on yellow‐fever vaccine and veterinary pharmaceutical formulations. The analytical results were statistically similar to those obtained with an HPLC‐based fluorescence method (after chemical derivatization). The proposed method is a simple, sensitive and selective approach that does not involve the use of toxic reagents employed for chemical derivatization of aminoglycoside antibiotics.