H-point standard additions method for simultaneous determination of sulfamethoxazole and trimethoprim in pharmaceutical formulations and biological fluids with simultaneous addition of two analytes

Multisensory Systems Based on Perfluorosulfonic Acid Membranes Modified with Polyaniline and PEDOT for Multicomponent Analysis of Sulfacetamide Pharmaceuticals

The degradation of sulfacetamide with the formation of sulfanilamide leads to a deterioration in the quality of pharmaceuticals. In this work, potentiometric sensors for the simultaneous determination of sulfanilamide, sulfacetamide and inorganic ions, and for assessing the degradation of pharmaceuticals were developed. A multisensory approach was used for this purpose. The sensor cross-sensitivity to related analytes was achieved using perfluorosulfonic acid membranes with poly(3,4-ethylenedioxythiophene) or polyaniline as dopants. The composite membranes were prepared by oxidative polymerization and characterized using FTIR and UV-Vis spectroscopy, and SEM. The influence of the preparation procedure and the dopant concentration on the membrane hydrophilicity, ion-exchange capacity, water uptake, and transport properties was investigated. The characteristics of the potentiometric sensors in aqueous solutions containing sulfanilamide, sulfacetamide and alkali metals ions in a wide pH range were established. The introduction of proton-acceptor groups and π-conjugated moieties into the perfluorosulfonic acid membranes increased the sensor sensitivity to organic analytes. The relative errors of sulfacetamide and sulfanilamide determination in the UV-degraded eye drops were 1.2 to 1.4 and 1.7 to 4%, respectively, at relative standard deviation of 6 to 9%.

Interaction of Carboxyalkylated Cellulose Nanocrystals and Antibiotics

Although antibiotics are beneficial for treating infections, their release into the environment has raised global concerns. In this work, the interactions of cellulose nanocrystal (CNC) derivatives with sulfamethoxazole (SMX), ciprofloxacin (CIP), and doxycycline (DOX) antibiotics were studied fundamentally. CNC was carboxyalkylated to bear different carbon chain lengths but similar negative charges on its surface. The highest level of adsorption of DOX on the carboxypantadecanated CNC (i.e., carboxyalkylated CNC with more carbon spacer, PCNC) occurred at pH 6.0, which was due to the electrostatic and π interactions along with hydrogen bonding. The contact angle and quartz crystal microbalance (QCM) adsorption analyses revealed a faster interaction and adsorption of DOX than other antibiotics on PCNC. The results also depicted the diffusion of DOX into the porous structure of CNC derivatives, especially that of PCNC. Also, a more compact adsorbed layer of DOX was formed on PCNC than on other CNC derivatives. Carboxyalkylation was observed to slightly reduce the surface area of CNC, while the antibiotic adsorption drastically increased the surface area of CNC due to their adsorption on the surface. XPS analysis revealed that carboxyalkylation significantly enhanced the C-C/C-H bond, while antibiotic adsorption on PCNC enhanced C-N/C-O and C-C/C-H bonds in antibiotic-loaded CNC samples. Overall, carboxyalkylated CNC was observed to have an outstanding affinity for capturing antibiotics, especially DOX, which could pave the way for the use of CNC in such applications that surface/antibiotic interactions were essential.

Separation-free spectrophotometric platforms for rapid assessment of combined antiplatelet therapy in complex matrices

Aim: To develop simple and rapid UV-spectrophotometric platforms for the simultaneous quantification of a binary mixture containing clopidogrel bisulphate (CPS) and aspirin (ASP) in complex matrices without prior separation. Experimental: Five mathematical models namely ratio-difference method, mean centering of the ratio spectra, dual wavelength, induced dual wavelength and H-Point Standard Addition method, were utilized for resolving spectral overlap by mathematical processing of ratio and zero-order absorption spectra. Analytes were extracted from tested matrices (whole blood, pharmaceutical formulations and dissolution media buffer) and quantified using the proposed methods. The methods were validated according to ICH guidelines. Results: The developed methods demonstrated limits of detection ranging from 0.67 to 1.09 μg/ml-1 for CPS and 0.49 to 0.71 μg.ml-1 for ASP. All proposed methods allowed for reliable determination of CPS and ASP in complex matrices within reported reference ranges, indicating their potential application for therapeutic drug monitoring and quality control testing.

Advanced approaches for the treatment and amplification of weak spectral signals produced by critical concentrations in white multicomponent systems

An analytical investigation was carried out to study the treatment and amplification of the spectral signals produced by critical concentrations with high accuracy and precision using two advanced approaches. The factorized-spectrum approach was applied through two novel methods which were: absorptivity centering technique via both: factorized zero order absorption spectrum (ACT-FSD⁰_ΔA) and factorized ratio spectrum (ACT-FSR_ΔP). The proposed methods were found to be linear in the ranges of (15-100 μg/mL) and (3-40 μg/mL) for ASP and MTO, respectively. Those methods were compared to the methods following the geometrical standard addition approach: ratio H-point standard addition method (RHPSAM) and geometrical induced amplitude modulation (GIAM). The approaches were applied for the determination of the minor component metoclopramide in its mixture with the major component aspirin in the challengeable ratio of (1,90) respectively in a white multicomponent system. The results obtained from the proposed approaches were statistically compared with each other. The methods were validated according to ICH guidelines where the results were found to be within the acceptable limits. The methods were found to be accurate and reliable for the determination of metoclopramide critical concentration besides aspirin concentration. The results of single factor ANOVA analysis indicated that there is no significant difference among the developed methods. These methods provided simple resolution of this binary combination from synthetic mixtures and pharmaceutical preparation and can be conveniently adopted for routine quality control analysis.

New Derivatization Methodology of 4-aminobenzoic Acid from its Dietary Supplements: Kinetic Spectrophotometric Methods for Determination

Background:

A new approach describing the validation and development of an easy, new spectrophotometric and kinetic method for identification of para-aminobenzoic acid in dietary supplement has been performed. In this study, para-aminobenzoic acid was derived in a pH-controlled environment, as a new organic compound 4(4-Benzophenylazo)pyrogallol, by incorporating diazotized para-aminobenzoic acid with pyrogallol.

Objective:

The determination of para-aminobenzoic acid was conducted by the fixed time and initial rate techniques. These approaches were based on the reaction of the compound containing paraaminobenzoic acid, 4(4-Benzophenylazo)pyrogallol, with Ag(I) to form colored product with a maximum absorbance at 468nm. Both of these techniques were adopted for constructing the calibration curves and examined for their suitability for the quantitation of para-aminobenzoic acid in dietary supplement.

Methods:

The determination process was established, using initial rate and fixed time kinetic spectrophotometric methods.

Results:

4(4-Benzophenylazo)pyrogallol was characterized using proton-nuclear magnetic resonance, Fourier-transform infrared, differential scanning calorimetry and thermogravimetric thermal methods, gas chromatography–mass techniques, and solvatochromic behavior in solvents with different polarities was also examined.

Conclusion:

For the first time, para-aminobenzoic acid was well determined by incorporating it as an organic solid compound, 4(4-Benzophenylazo)pyrogallol, through coupling pyrogallol with diazotized para-aminobenzoic acid in regulated pH medium, ranging between 5.0 to 6.0. The existence of common excipients in the dietary supplement did not produce any significant interference. F- and ttest data analysis were used for statistical comparison of the suggested techniques with that of reference method, demonstrating excellent agreement with no significant difference in the associated precision and accuracy.

Hyperbolic subtraction method: Determination of the concentration of an analyte in the presence of an unknown interferent via spectral data

A theoretical model to determine the concentration of an analyte in the presence of unknown interferents using spectral-type data is described. The method involves absorbance measurements at three wavelengths and the calculation of specific absorbances yielding a hyperbolic relationship between absorbance ratios and analyte concentrations. The concentration of the analyte of known spectrum can be determined in the presence of an interferent or mixture of interferents of unknown concentration(s) and spectra can be determined combining data for different sets of wavelengths. Application to indigo and isatin solutions in DMSO related to the so-called Maya blue problem is reported as an illustrative application example.

H-point standard addition for simultaneous reagent-free spectrophotometric determination of B1 and B6 vitamins

Vitamin deficiency is a main cause of many disorders and diseases that cannot be treated without using dietary supplements and multivitamin medications. We present here a UV-spectrophotometric method for simultaneous assay of two of the widely used vitamins, thiamine hydrochloride (vitamin B1) and pyridoxine hydrochloride (vitamin B6). The method is based on H-point standard addition to estimate the vitamins under study in their pure solutions and multivitamin ampoules by measuring the absorption of the mixture at 283 and 298 nm allowing its application in quality control laboratories. The work summarizes the theoretical basis of the H-point standard addition method. Moreover, a guide for the selection of the two wavelengths at which the calibration curves are constructed is given in this investigation. The linear ranges of the calibration graphs are 6.75-67.5 and 2.06-20.56 μg/mL for thiamine and pyridoxine, respectively. Correlation coefficients (r²) were found to be 0.9990 and 0.9899 at 283 nm and 0.9855 and 0.9995 at 298 nm for vitamin B1 and vitamin B6, respectively. Oscillator strength (f), transition dipole moment (μ) and resonance energy (R_N) were calculated. The method was successfully applied for dual determination of the vitamins in their pure solutions and multivitamin ampoules with recovery values ranging from 98.41 to 102.6 and from 95.39 to 104.9% for thiamine and pyridoxine, respectively. The accuracy and precision of the proposed method is obvious from the low relative standard deviation values which are not more than 1.19%.

Microwave assisted solid phase extraction for separation preconcentration sulfamethoxazole in wastewater using tyre based activated carbon as solid phase material prior to spectrophotometric determination

This work was chiefly encouraged by the continuous consumption of antibiotics which eventually pose harmful effects on animals and human beings when present in water systems. In this study, the activated carbon (AC) was used as a solid phase material for the removal of sulfamethoxazole (SMX) in wastewater samples. The microwave assisted solid phase extraction (MASPE) as a sample extraction method was employed to better extract SMX in water samples and finally the analysis of SMX was done by the UV-Vis spectrophotometer. The microwave assisted solid phase extraction method was optimized using a two-level fractional factorial design by evaluating parameters such as pH, mass of adsorbent (MA), extraction time (ET), eluent ratio (ER) and microwave power (MP). Under optimized conditions, the limit of detection (LOD) and limit of quantification (LOQ) were 0.5μgL^-1 and 1.7μgL^-1, respectively, and intraday and interday precision expressed in terms of relative standard deviation were >6%.The maximum adsorption capacity was 138mgg^-1 for SMX and the adsorbent could be reused eight times. Lastly, the MASPE method was applied for the removal of SMX in wastewater samples collected from a domestic wastewater treatment plant (WWTP) and river water.

Validated electrochemical and chromatographic quantifications of some antibiotic residues in pharmaceutical industrial waste water

Realistic implementation of ion selective electrodes (ISEs) into environmental monitoring programs has always been a challenging task. This could be largely attributed to difficulties in validation of ISE assay results. In this study, the electrochemical response of amoxicillin trihydrate (AMX), ciprofloxacin hydrochloride (CPLX), trimethoprim (TMP), and norfloxacin (NFLX) was studied by the fabrication of sensitive membrane electrodes belonging to two types of ISEs, which are polyvinyl chloride (PVC) membrane electrodes and glassy carbon (GC) electrodes. Linear response for the membrane electrodes was in the concentration range of 10^-5-10^-2 mol/L. For the PVC membrane electrodes, Nernstian slopes of 55.1, 56.5, 56.5, and 54.0 mV/decade were achieved over a pH 4-8 for AMX, CPLX, and NFLX, respectively, and pH 3-6 for TMP. On the other hand, for GC electrodes, Nernstian slopes of 59.1, 58.2, 57.0, and 58.2 mV/decade were achieved over pH 4-8 for AMX, CPLX, and NFLX, respectively, and pH 3-6 for TMP. In addition to assay validation to international industry standards, the fabricated electrodes were also cross-validated relative to conventional separation techniques; high performance liquid chromatography (HPLC), and thin layer chromatography (TLC)-densitometry. The HPLC assay was applied in concentration range of 0.5-10.0 μg/mL, for all target analytes. The TLC-densitometry was adopted over a concentration range of 0.3-1.0 μg/band, for AMX, and 0.1-0.9 μg/band, for CPLX, NFLX, and TMP. The proposed techniques were successfully applied for quantification of the selected drugs either in pure form or waste water samples obtained from pharmaceutical plants. The actual waste water samples were subjected to solid phase extraction (SPE) for pretreatment prior to the application of chromatographic techniques (HPLC and TLC-densitometry). On the other hand, the fabricated electrodes were successfully applied for quantification of the antibiotic residues in actual waste water samples without any pretreatment. This finding assures the suitability of the fabricated ISEs for environmental analysis.

Application of RP-HPLC method in dissolution testing and statistical evaluation by NASSAM for simultaneous estimation of tertiary combined dosages forms

A dissolution method with robust high performance liquid chromatographic (HPLC) analysis for immediate release tablet formulation was developed and validated to meet the requirement as per International Conference on Harmonization (ICH) and United States Food and Drug Administration (USFDA) guidelines. The method involved the use of Agilent ZORBAX Eclipse XDB C₁₈ column, and temperature was maintained at 30 °C. After optimization, the mobile phase was selected as phosphate buffer (KH₂PO₄, 30 mM) : ACN (60:40, v/v) with pH 3.0, and retention time R_t was found as 3.24, 4.16, and 2.55 min for paracetamol (PCM), chlorpheniramine maleate (CPM) and phenylephrine hydrochloride (PH) respectively at 265 nm and at a flow rate of 1 mL/min. The relative standard deviation (%RSD) for 6 replicate measurements was found to be less than 2%. Furthermore net analyte signal standard addition method (NASSAM) with spectrophotometer was performed for standard and liquid oral suspension. On the basis of selectivity, sensitivity and accuracy analysis, it was confirmed that this novel method could be useful for simultaneous estimation of the given drug combinations. Two-way analysis of variance (ANOVA) was applied for evaluating the statistical difference between the assay results obtained via both NASSAM and RP–HPLC methods and ultimately no significant difference was found between both the methods. All the methods and results were acceptable and confirmed that the method was suitable for intended use.