Spectrofluorometric determination of nicardipine, nifedipine and isradipine in pharmaceutical preparations and biological fluids

A Design-assisted Spectrofluorometric Method Utilizing a One-pot Fluorescent Probe for the Quantitation of some Calcium Channel Blockers

Based on their reaction with highly fluorescent carbon quantum dots (CQDts), a precise and reliable spectrofluorometric approach was developed for the determination of three calcium channel blockers. The studied drugs are: lercanidipine, nimodipine and nifedipine. (CQDts) were produced using a one-step hydrothermal method with ascorbic acid as the carbon source. The produced CQDts were capped by alcohol to create yellow emitters displaying a high fluorescence emission at 524 nm when excited at 325 nm. The fluorescence intensity of CQDts was noticeably quenched by each of the three calcium channel blockers. The relation between their concentrations and fluorescence quenching is linear over the concentration range of 0.5-20 µg/mL for each of the three drugs. A full factorial design was used to optimize the effect of variable factors. Therefore, under optimum experimental design conditions, the detection limits for lercanidipine, nimodipine, and nifedipine were 0.11 ± 1.09, 0.10 ± 0.25 and 0.12 ± 0.71 µg/mL, respectively. The LOQ was 0.33, 0.30, and 0.37 µg/mL respectively. The quenching of fluorescent CQDts occurred through the inner filter effect (IFE) for nimodipine, while it was mixed with dynamic quenching for lercanidipine and nifedipine. The proposed method was effectively used to determine the cited drugs in their pharmaceutical products and had an acceptable level of precision. The selectivity of the CQDts system towards the studied drugs was examined indicating no interference from interfering species.

Insights for applying N,S-doped carbon dots as a fluorescent nanoprobe for estimation of some nitro-calcium channel blockers

A facile and simple one-step hydrothermal approach was adopted for fabrication of N and S co-doped carbon quantum dots probe (NSCDs) by using thiosemicarbazide as a dopant and citric acid as a precursor. The prepared NSCDs with a high quantum yield of 0.58 were characterized using UV-visible spectroscopy, IR spectroscopy and high-resolution transmission electron microscopy. The as-obtained NSCDs could be deemed as an effective fluorescent nanosensor for the determination of some anti-hypertensive nitro-calcium channel blockers (Nitro-CCBs) including nicardipine (NIC), nifedipine (NIF) and nimodipine (NIM) whether in pure form or in their pharmaceutical formulations. Measurements of NSCD emission intensity were performed at 416 nm after being excited at 345 nm. Nitro-CCBs could induce quenching in the native fluorescence of NSCDs due to the inner filter effect and static quenching mechanism. The studied compounds were investigated within linear detection range of (10.0-100.0 µM) for NIC, (5.0-60.0 µM) for NIF and (5.0-60.0 µM) for NIM. Correlation coefficients are greater than or equal to 0.9998 and detection limits are ranged between 0.55 and 1.86 µM. The proposed method was extended to estimate the studied compounds in different pharmaceutical samples with high % recoveries ranging from (97.95 to 101.28%) and low % relative standard deviation values (less than 2%). Validation of the developed spectrofluorimetric method was done along with the International Council of Harmonization requirements.

Flourimetric study on antidiabetic combined drugs; empagliflozin and linagliptin in their pharmaceutical formulation and human plasma

Empagliflozin and linagliptin are newly approved FDA combination that used for the treatment of type 2 diabetes mellitus (T2DM) under trade name Glxambi. Two spectroflourimetric methods were developed for simple quantitative determination of empagliflozin and linagliptin in their pharmaceutical formulation and human plasma without need any tedious processing operations. Empagliflozin has a native fluorescence nature, therefore can be directly determined by measuring emission peak at 305 nm after excitation at 234 nm. There is no any interference from linagliptin at this emission wavelength. On the other hand, linagliptin is a very weak florescent compound that needs to react with fluorogenic reagent to be quantitatively determined without any reaction of empagliflozin. So, quantitative analysis of linagliptin was achieved by coupling with NBD-Cl which is an electro active halide reagent (targeting only Linagliptin with no effect on empagliflozin). Dark yellow fluorophore with high fluorescence is a result of this reaction and can be measured at emission wavelength 538 nm after excition at wavelength 469 nm. Experimental conditions of the suggested methods were well checked and optimized. The regression plots were found to be linear over the range of 40-1200 ng/mL and 3-700 ng/mL for empagliflozin and linagliptin, respectively. The obtained results by the suggested methods were statistically compared with those obtained by the reported methods, showing no significant difference with respect to accuracy and precision at p = 0.05.

An innovative validated spectrofluorimetric method for determination of Lisinopril in presence of hydrochlorothiazide; application to content uniformity testing

A new sensitive and discriminating spectrofluorimetric method has been developed and validated for determination of Lisinopril, one of the angiotensin converting enzyme inhibitors, in its pure bulk form and pharmaceutical tablets. The reaction of Lisinopril with ethylacetoacetate and formaldehyde in acidic buffered medium (pH3.8) has yielded a pale yellow product that exhibited a high fluorescence measured at 438nm after excitation at 350nm. All the experimental parameters affecting the formation and stability of the produced fluorophore were carefully investigated and optimized to give the maximum sensitivity. The fluorescence intensity was directly proportional to the drug concentration in the range of 0.5-4.5μg/mL with a limit of detection equal to 0.16μg/mL. The method was successfully applied in the analysis of the commercially available pharmaceutical tablets containing the single drug or its binary mixtures with Hydrochlorothiazide. Furthermore, the developed procedure was adapted for studying the content uniformity test of some dosage forms containing the cited drug.

Resonance Rayleigh scattering and resonance nonlinear scattering methods for the determination of nicardipine hydrochloride using eosin Y as a probe

A novel, highly sensitive, simple and quick method to determine nicardipine hydrochloride by RRS, SOS and FDS were established.

Quantification of isradipine in human plasma using LC-MS/MS for pharmacokinetic and bioequivalence study

A highly sensitive and rapid method for the analysis of isradipine in human plasma using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was developed. The procedure involves a simple liquid-liquid extraction of isradipine and amlodipine (IS, internal standard) with methyl-t-butyl ether after alkaline treatment and separation by RP-HPLC. Detection was performed by positive ion electrospray ionization (ESI) in multiple reaction monitoring (MRM) mode, monitoring the transitions m/z 372.1-->m/z 312.2 and m/z 408.8-->m/z 237.9, for quantification of isradipine and IS, respectively. The standard calibration curves showed good linearity within the range of 10 to 5000 pg/mL (r(2)>or=0.9998). The lower limit of quantitation (LLOQ) was 10 pg/mL. The retention times of isradipine (0.81 min) and IS (0.65 min) suggested the potential for high throughput of the proposed method. In addition, no significant metabolic compounds were found to interfere with the analysis. This method offered good precision and accuracy and was successfully applied for the pharmacokinetic and bioequivalence studies of 5 mg of sustained-release isradipine in 24 healthy Korean volunteers.