Voltammetric and flow amperometric determination of drug guaifenesin in pharmaceutical and biological samples using screen-printed sensor with boron doped diamond electrode

New voltammetric and flow amperometric methods for the determination of guaifenesin (GFE) using a perspective screen-printed sensor (SPE) with boron-doped diamond electrode (BDDE) were developed. The electrochemical oxidation of GFE was studied on the surface of the oxygen-terminated BDDE of the sensor. The GFE provided two irreversible anodic signals at a potential of 1.0 and 1.1 V (vs. Ag|AgCl|KCl sat.) in Britton-Robinson buffer (pH 2), which was chosen as the supporting electrolyte for all measurements. First, a voltammetric method based on differential pulse voltammetry was developed and a low detection limit (LOD = 41 nmol L-1), a wide linear dynamic range (LDR = 0.1-155 μmol L-1), and a good recovery in the analysis of model and pharmaceutical samples (RSD <3.0 %) were obtained. In addition, this sensor demonstrated excellent sensitivity and reproducibility in the analysis of biological samples (RSD <3.2 %), where the analysis took place in a drop of serum (50 μL) without pretreatment and additional electrolyte. Subsequently, SP/BDDE was incorporated into a flow-through 3D printed electrochemical cell and a flow injection analysis method with electrochemical detection (FIA-ED) was developed, resulting in excellent analytical parameters (LOD = 86 nmol L-1, LDR = 0.1-50 μmol L-1). Moreover, the mechanism of electrochemical oxidation of GFE was proposed based on calculations of HOMO spatial distribution and spectroelectrochemical measurements focused on IR identification of intermediates and products.

Green highly sensitive and selective spectroscopic detection of guaifenesin in multiple dosage forms and spiked human plasma

Guaifenesin (GUA) is determined in dosage forms and plasma using two methods. The spectrofluorimetric technique relies on the measurement of native fluorescence intensity at 302 nm upon excitation wavelength "223 nm". The method was validated according to ICH and FDA guidelines. A concentration range of 0.1-1.1 μg/mL was used, with limit of detection (LOD) and quantification (LOQ) values 0.03 and 0.08 µg/mL, respectively. This method was used to measure GUA in tablets and plasma, with %recovery of 100.44% ± 0.037 and 101.03% ± 0.751. Furthermore, multivariate chemometric-assisted spectrophotometric methods are used for the determination of GUA, paracetamol (PARA), oxomemazine (OXO), and sodium benzoate (SB) in their lab mixtures. The concentration ranges of 2.0-10.0, 4.0-16.0, 2.0-10.0, and 3.0-10.0 µg/mL for OXO, GUA, PARA, and SB; respectively, were used. LOD and LOQ were 0.33, 0.68, 0.28, and 0.29 µg/mL, and 1.00, 2.06, 0.84, and 0.87 µg/mL for PARA, GUA, OXO, and SB. For the suppository application, the partial least square (PLS) model was used with %recovery 98.49% ± 0.5, 98.51% ± 0.64, 100.21% ± 0.36 & 98.13% ± 0.51, although the multivariate curve resolution alternating least-squares (MCR-ALS) model was used with %recovery 101.39 ± 0.45, 99.19 ± 0.2, 100.24 ± 0.12, and 98.61 ± 0.32 for OXO, GUA, PARA, and SB. Analytical Eco-scale and Analytical Greenness Assessment were used to assess the greenness level of our techniques.

Two green and sensitive spectrofluorimetric approaches for determination of Ambroxol and guaifenesin in their single and combined pharmaceutical formulations

Ambroxol hydrochloride (AMX) and guaifenesin (GFN) are approved drugs utilized to treat coughs through their potent mucolytic and expectorant properties. Due to their massive, combined administration in many illnesses, there is a persistent need for their concurrent estimation in different pharmaceutical formulations. Two sensitive, environmentally friendly spectrofluorimetric methods were developed. AMX was determined using the first method (I) without interference from GFN. This method depends on the quenching of Erythrosine B (EB) native fluorescence at 552 nm after excitation at 527 nm due to the formation of a non-fluorescent AMX-EB ion-pair complex in Britton-Robinson buffer (BRB) solution pH (3.5). The concentration plot is linear over the 0.25-5.0 μg/mL range, with a mean percent found value of 99.74%. Method (II) depends on measuring the native fluorescence of aqueous GFN solution at two analytical wavelengths, either 300 or 600 nm, after excitation at 274 nm. Relative fluorescence intensity (RFI)-concentration plots are linear over the ranges of 0.02-0.5 and 0.1-2.0 μg/ml, with mean percent found at 99.96% and 99.91% at dual wavelengths, respectively. The proposed methods were successfully applied to assay both drugs in raw materials and different single and combined pharmaceutical formulations. These methods have been thoroughly validated following International Committee on Harmonisation (ICH) guidelines. National Environmental Methods Index, Analytical Eco-Scale, and Green Analytical Procedure Index were used to prove greenness, thereby enhancing their applicability. The proposed techniques provide straightforward, precise, and cost-effective solutions for routine formulation analysis in quality control laboratories.

Fast concurrent determination of guaifenesin and pholcodine in formulations and spiked plasma using first derivative synchronous spectrofluorimetric approach

Guaifenesin and pholcodine are frequently co-formulated in certain dosage forms. A new fast first derivative synchronous spectrofluorometric method has been used for their simultaneous analysis in mixtures. Here, first derivative synchronous spectrofluorometry enabled the successful simultaneous estimation of guaifenesin at 283 nm and pholcodine at 275 nm using a wavelength difference (Δλ) of 40 nm. The method was fully validated following International Council of Harmonization guidelines. For guaifenesin and pholcodine, linearity was determined within the corresponding ranges of 0.05-0.30 and 0.10-6.0 μg/ml. The two drugs were effectively analyzed using the developed approach in their respective formulations, and the results showed good agreement with those attained using reference methods. The method demonstrated excellent sensitivity, with detection limits down to 0.007 and 0.030 μg/ml and quantitation limits of 0.020 and 0.010 μg/ml for guaifenesin and pholcodine, respectively. Therefore, the procedure was successful in determining these drugs simultaneously in vitro in spiked plasma samples and syrup dosage form. The developed methodology also offered an environmentally friendly advantage by utilizing water as the optimal diluting solvent throughout the whole work. Different greenness approaches were investigated to ensure the method's ecofriendly properties.

Robust Chromatographic Methods for the Analysis of Two Quaternary Mixtures Containing Paracetamol, Codeine, Guaifenesin and Pseudoephedrine or Phenylephrine in their Dosage Forms

Two simple validated and highly selective methods for analysis of paracetamol, codeine, guaifenesin and pseudoephedrine or phenylephrine quaternary mixtures were developed. The first method is a high performance liquid chromatography with diode array detection method where separation was successful using Agilent C18 (150 × 4.6 mm) column, gradient elution of phosphate buffer pH 3, methanol and acetonitrile and diode-array detection at 210 nm. The second method is a HPTLC method followed by densitometric measurement of the spots at 257 nm. Separation was carried out on Merck HPTLC aluminum sheets of silica gel using methylene chloride: methanol: glacial acetic acid: ammonia (17.8: 1.68: 0.4: 0.12, v/v) mobile phase. The methods were applied successfully for analysis of both quaternary mixtures in laboratory-prepared tablets and also validated in regards to linearity, precision, accuracy, sensitivity and stability.

Application of derivative emission fluorescence spectroscopy for determination of ibuprofen and phenylephrine simultaneously in tablets and biological fluids

Two sensitive, rapid, and accurate derivative emission spectrofluorimetric methods applying zero crossing techniques were developed for simultaneous determination of binary mixtures of ibuprofen (IBU) and phenylephrine hydrochloride (PHE) in pure powder, synthetic mixture and combined tablets. The proposed methods were performed via measuring the intersected drug derivative amplitude of one drug at the zero crossing points for the other one and vice versa. The two methods rely on the measurement of the combined drugs native fluorescence after excitation at 270 nm in methanol directly, followed by differentiation using first (D₁) and second derivative (D₂) techniques. Applying the D₁, IBU was measured quantitatively at 293.1 nm at zero crossing of PHE, on the other side; PHE was measured quantitatively at 300.7 nm at zero crossing of IBU. By the same way, applying the D₂, the wavelengths selected were 303.5 nm for IBU and 312.9 nm for PHE. The concentration plots of derivative fluorescence intensity were rectilinear over the range of 0.5-10 μg/mL and 0.025-0.5 μg/mL for IBU and PHE, respectively. The results obtained with average % recoveries ± RSD are 99.73 ± 0.72 (IBU, D₁), 99.49 ± 0.95 (PHE, D₁), 99.79 ± 0.47 (IBU, D₂), and 99.88 ± 0.34 (PHE, D₂) were in good agreement with the comparison method. The proposed methods offer high sensitivity that enable direct analysis of IBU and PHE in spiked human plasma. The proposed methods were entirely validated in terms of ICH guidelines.

Derivative synchronous spectrofluorimetry: Application to the analysis of two binary mixtures containing codeine in dosage forms

Two binary mixtures containing codeine (COD) with either ibuprofen (IBU), mixture 1, or with phenylephrine hydrochloride (PE), mixture 2, were analyzed using three simple eco-friendly spectrofluorimetric methods without the need to a prior separation step. The first method is derivative emission spectrofluorimetry using λ_ex = 236 nm and 275 nm for mixtures 1 and 2, respectively. The second method is constant-wavelength synchronous spectrofluorimetry using ∆λ = 100 nm and 60 nm for mixtures 1 and 2, respectively. The last method is constant-energy synchronous spectrofluorimetry where a wave number interval of -7000 cm^-1 was used for the analysis of the two binary mixtures. All measurements were performed in acetate buffer pH 5 and thus no toxic volatile solvents were used increasing method greenness. High sensitivity was attained for the three studied drugs where the lower limits of quantitation of COD, IBU and PE reached 0.064, 0.512 and 0.087 μg/mL, respectively. Analysis of the two binary mixtures in their tablet and liquid dosage forms was performed with good accuracy and precision using the developed methods. The results of the proposed and reported methods were statistically evaluated using one-way ANOVA test and no significant difference among them was obtained. In addition, all aspects of ICH guidelines on analytical method validation were conducted.

Micelle-enhanced direct spectrofluorimetric method for the determination of linifanib: Application to stability studies

A new simple stability-indicating spectrofluorimetric method has been developed and validated for the determination of the tyrosine kinase inhibitor, linifanib (LNF). The proposed method makes use of the native fluorescence characteristics of LNF in a micellar system. Compared with aqueous solutions, the fluorescence intensity of LNF was greatly enhanced upon the addition of Tween-80. The relative fluorescence intensity of LNF was measured in a diluting solvent composed of 2% Tween-80: phosphate buffer pH 8.0 (20: 80, v/v) using excitation and emission wavelengths of 290 and 450 nm, respectively. The proposed method was fully validated as per the ICH guidelines. The recorded fluorescence intensity of LNF was rectilinear over a concentration range of 0.3-2 μg/ml with a high correlation coefficient (r = 0.9990) and low limits of detection (0.091 μg/ml) and quantitation (0.275 μg/ml). The applicability of the method was extended to study the inherent stability of LNF under different stress degradation conditions including, alkaline, acidic, oxidative, photolytic and thermal degradation. Moreover, the method was utilized to study the kinetics of the alkaline and oxidative degradation of LNF. The pseudo-first order rate constants and half-lives were calculated.

An eco-friendly direct spectrofluorimetric method for the determination of irreversible tyrosine kinase inhibitors, neratinib and pelitinib: application to stability studies

A new rapid and simple stability-indicating spectrofluorimetric method has been developed for the determination of two irreversible tyrosine kinase inhibitors (TKIs), neratinib (NER) and pelitinib (PEL). The method is based upon measurement of the native fluorescence intensity of both drugs at λ_ex 270 nm in aqueous borate buffer solutions (pH 10.5). The fluorescence intensity recorded at 545 nm (NER) and 465 nm (PEL) were rectilinear over the concentration range of 0.1-10 μg/mL for both drugs with a high correlation coefficient (r > 0.999). The proposed method provided low limits of detection and of quantitation of 0.07, 0.11 μg/mL (NER) and 0.02, 0.05 μg/mL (PEL), respectively. The method was successfully applied for the determination of NER and PEL in bulk powder. The proposed methods were fully validated as per the International Conference on Harmonisation (ICH) guidelines. The application of the method was extended to stability studies of both NER and PEL under different forced-degradation conditions (acidic-induced, base-induced, oxidative, wet heat, and photolytic degradation). Moreover, the kinetics of the base-induced and oxidative degradation of both drugs was investigated and the pseudo-first-order rate constants and half-lives were estimated at different temperatures. Also, an Arrhenius plot was applied to predict the stability behaviour of the two drugs at room temperature. Copyright © 2016 John Wiley & Sons, Ltd.

Green approach using monolithic column for simultaneous determination of coformulated drugs

Green chemistry and sustainability is now entirely encompassed across the majority of pharmaceutical companies and research labs. Researchers' attention is careworn toward implementing the green analytical chemistry principles for more eco-friendly analytical methodologies. Solvents play a dominant role in determining the greenness of the analytical procedure. Using safer solvents, the greenness profile of the methodology could be increased remarkably. In this context, a green chromatographic method has been developed and validated for the simultaneous determination of phenylephrine, paracetamol, and guaifenesin in their ternary pharmaceutical mixture. The chromatographic separation was carried out using monolithic column and green solvents as mobile phase. The use of monolithic column allows efficient separation protocols at higher flow rates, which results in short time of analysis. Two-factor three-level experimental design was used to optimize the chromatographic conditions. The greenness profile of the proposed methodology was assessed using eco-scale as a green metrics and was found to be an excellent green method with regard to the usage and production of hazardous chemicals and solvents, energy consumption, and amount of produced waste. The proposed method improved the environmental impact without compromising the analytical performance criteria and could be used as a safer alternate for the routine analysis of the studied drugs.

Rapid and selective determination of pitavastatin calcium in presence of its degradation products and co-formulated drug by first-derivative micelle-enhanced and synchronous fluorimetric methods

New, selective and rapid methods are presented for determination of PIT in the presence of its hydrolytic degradation products and co-formulated drug, EZE. These methods are derivative micelle enhanced native fluorescence and synchronous fluorimetry.