MOLECULAR MODELING, REACTIVITY PARAMETERS AND SPECTROCHEMIC STUDIES OF ε-CAPROLACTAM AND o-PHENANTROLINE

In this work, molecular models were obtained, and the reactivity parameters of ε-caprolactam and ophenanthroline were calculated to evaluate the interaction in the formation of complex molecular compounds. It was observed that the main electron donor atoms, in the formation of the metal-ligand bond, are centered mainly on the oxygen and nitrogen atoms, respectively, which are sterically more favorable in these species. Conductance measurements in an aqueous solution were obtained to observe the electrolytic behavior of these compounds. Infrared spectra were also recorded to characterize vibrational transitions in identifying these species when present in complex systems. Molecular spectra of absorption in the UV-visible region were recorded to evaluate the spectrochemical properties of these individual ligands and further verify their influence on the formation of complex molecular systems. The parameters evaluated include the molar absorptivity ε, integrated absorption coefficient, oscillator force, and transition dipole moment. It was observed that the ε parameter indicates molecular transitions in the 190 – 300 nm region and the near-infrared, and the oscillator strength is typical of molecules used as dyes and sensitizers for optical light-emitting systems or light-to-electricity converters.

A Novel Spectrophotometric Determination and Kinetic Study of Sulfamethoxazole in Pure and Tablet Formulation using 9-chloroacridine Reagent

A spectrophotometric method has been developed for analysis of Sulfamethoxazole (SMX) in pure and dosage forms. The method is based on the reaction of the SMX with 9-chloroacridine (9-CA) reagent in organic and acidic medium, to produce a yellow product having maximum absorption at 448 nm. Beer’s law was obeyed in the concentration range 1-30 μg.ml-1 with molar absorptivity of 1.63x104 L.mol-1.cm-1 with good detection and quantification limits. Accuracy (Average recovery %) and precision are 98.43% and 0.651, respectively. The proposed method was applied successfully for determination of Sulfamethoxazole in its commercial dosage form as tablet and agree well with the official method. The equilibrium constant and the thermodynamic functions (ΔHo, ΔGº and ΔSº) of the complex formation were estimated. The study revealed that the complex formation could occur spontaneously, the type of interacting forces between SMX and 9-CA are physical is nature and association increases the order of the studied systems. The results of kinetic parameters indicated that, the reaction is pseudo first order with respect to SMX. The rate constant at various temperatures and the thermodynamic functions of activation were determined. Theoretical parameters were calculated by applying the semi-empirical Austin method (AM1). These parameters are helped to suggest reaction mechanism and supporting other results.

Multivariate analytical methods for simultaneous estimation of Atenolol and Hydrochlorothiazide in bulk and tablet dosage form

The present study aimed to develop simple, accurate and precise FTIR and UV spectrophotometric methods for the quantification of Atenolol and Hydrochlorothiazide in bulk and tablet dosage forms. FT-IR method like classical least squares (CLS) was developed within the range of 2366.69-3433.44; 1564.40-1673.30 cm- UV methods like Cramer’s matrix method (method-I) and linear regression analysis (Method II) were developed and they are based upon constructing the matrix set by using molar absorptivity values at 275.60 nm and 270.40 nm. The assay values for FTIR- CLS method were 102% and 108 % for Atenololand Hydrochlorothiazide respectively. Cramer’s matrix method results were found to be 95.15% and 104% for Atenolol and Hydrochlorothiazide respectively and for linear regression method they were found to be 98.50% and 106% (w/w).

SPECTROPHOTOMETRIC METHODS FOR DETERMINATION OF SOFOSBUVIR AND DACLATASVIR IN PURE AND DOSAGE FORMS

Objective: Two simple, sensitive and accurate spectrophotometric methods have been developed for the determination of sofosbuvir (SOF) and daclatasvir (DAC) in pure forms and pharmaceutical formulations. Methods: The proposed methods are based on the oxidation of SOF and DAC by a known excess of cerium(IV) ammonium nitrate in sulphuric acid medium followed by determination of unreacted cerium(IV) by adding a fixed amount of indigo carmine (IC) and alizarin red S (ARS) dyes followed by measuring the absorbance at 610 and 360 nm, respectively. The experimental conditions affecting the reaction were studied and optimized. Results: The beer’s law was obeyed in the concentration ranges of 0.2-3.0, 0.2-4.0 for SOF and 0.5-4.5 and 0.5-5.0 μg/ml for DAC using IC and ARS methods, respectively with a correlation coefficient ≥ 0.9991. The calculated molar absorptivity values are 2.354 × 104, 1.933 × 104 for SOF and 1.786 × 104 and 2.015 × 104 L/mol. cm for DAC using IC and ARS methods, respectively u. The limits of detection and quantification are also reported. Intra-day and inter-day precision and accuracy of the methods have been evaluated. Conclusion: The methods were successfully applied to the assay of SOF and DAC in tablets and the results were statistically compared with those of the reference method by applying Student’s t-test and F-test. No interference was observed from the common tablet excipients. The accuracy and reliability of the methods were further ascertained by performing recovery studies using the standard addition method.

Spectrophotometric determination of atenolol via oxidation and bleaching color reaction for methyl red dye

A selective and sensitive spectrophotometric method has been suggested for the quantitative assay of atenolol (ATNL) as pure and in its manufactural formulation(Tablet). The suggested procedure included oxidation of ATNL with an excess quantity of the oxidant N-bromosuccinimide (NBS), and then the excess of NBS was occupied in bleaching the color of methyl red dye(MRD), then measuring the absorbance of remaining MRD at 518 nm. The absorbance of the unbleached color of MRD corresponds to the ATNL concentration in the sample solution. Beer’s law was followed in the range of 0.1-2.0 μg.ml−1with molar absorptivity value equal to 8.8864x104 l.mol−1. cm−1. The suggested method was applied to the assay of ATNL in commercial tablets, with satisfactory results.

Spectrophotometric assay of Nicotinamide in Pharmaceutical Dosages

The reaction of nicotinamide and alizarin reagent using charge transfer reaction at a pH of 5.54 lead to produce a red colored compound measured at 527 nm., while the blue colored complex was formed using the oxidation reduction reaction between nicotinamide and chromate at pH 3.49 in the presence of an indigo cochineal dye. Theses tow colored products were measured at 527 and 610 nm respectively using two simple, fast and an accurate spectrophotometric methods. The linearity of the charge transfer method was followed Beer’s law 0.4 - 32 μg while the oxidation reduction method was obeyed Beer’s law from 1.6 - 40 μg in depending on the concentration range. Molar absorptivity was 1.95×104 and 2.16×104 mol−1 cm−1 for the red and blue colored complex respectively. Finally, the values of Sandal’s sensitivity were 0.00626 and 0.00565 μg−2 cm−1 for the first and second methods respectively. These two methods have been applied to quantify the amount of nicotinamide in pharmaceuticals with good recovery.

Spectrophotometric Determination of p-aminobenzoic acid via Diazotization and Coupling reaction

A simple and accurate spectrophotometric method to assay p-aminobenzoic acid (PABA) has been suggested. The method based on the diazotization of PABA via reaction with nitrite ions which liberated in the medium through the reaction of sodium nitrite with hydrochloric acid, then coupling the dizotised-PABA(D-PABA)with 1-naphthylamine -7-sulphonic acid (1-NASA) to form an intense colored pink azo dye ,it is water-soluble , very stable and has a maximum absorbance at 525 nm. The absorbance was increase with the increasing of PABA amounts in the solution, and the linearity from 2.5 to70 µg in 10 ml (0.25to7 µg.ml-1).The molar absorptivity and Sandell ҆s sensitivity values have been calculated they equal to 3.6057x104 L.mol-1 cm -1 and 0.0037993 µg. cm-2 respectively. The two values above demonstrated a good sensitivity of the suggested method. The method has been used in estimated PABA resulted from analysis of folic acid in tablet.

Unsymmetrical cyanine dye via in vivo hitchhiking endogenous albumin affords high-performance NIR-II/photoacoustic imaging and photothermal therapy

Herein, an unprecedented synergistic strategy for the development of high-performance NIR-II fluorophore is proposed and validated. Based on an unsymmetrical cyanine dye design strategy, the NIR-II emissive dye NIC was successfully developed by replacing only one of the indoline donors of symmetrical cyanine dye ICG with a fully conjugated benz[c,d]indole donor. This minor structural change maximally maintains the high extinction coefficient advantage of cyanine dyes. NIC-ER with endogenous albumin-hitchhiking capability was constructed to further enhance its in vivo fluorescence brightness. In the presence of HSA (Human serum albumin), NIC-ER spontaneously resides in the albumin pocket, and a brilliant ~89-fold increase in fluorescence was observed. Due to its high molar absorptivity and moderate quantum yield, NIC-ER in HSA exhibits bright NIR-II emission with high photostability and significant Stokes shift (>110 nm). Moreover, NIC-ER was successfully employed for tumor-targeted NIR-II/PA imaging and efficient photothermal tumor elimination. Overall, our strategy may open up a new avenue for designing and constructing high-performance NIR-II fluorophores.

Spectrophotometric determination of iron (III) catalyst in organic compound chlorinations

In the science or industrial practice of chemical processes, iron (III) is sometimes used as a catalyst in organic compound chlorinations due to its effectiveness and low cost. Thus, a fast and easy method of determination in the system is useful especially when metallic iron is used as a precursor which is readily converted into iron (III) chloride by the gaseous chlorine used in the chlorination reactor. In the latter case, the determination of the produced catalytically effective iron (III) is a prerequisite for controlling the kinetic progress of chlorination. In this work, a method for the spectrophotometric determination of iron (III) chloride in organic media after complexation with methyl ethyl ketone is investigated. The formation of a strong o-complex of iron (III) with methyl ethyl ketone allows direct determination of iron at 360 nm.Beer’s law is valid up to absorbance 2.42, where the iron (III) concentration is 20.7 mg·L-1, with molar absorptivity (e) equal to 6.532×103 L·mol-1·cm-1 and Sandell’s sensitivity 8.5×10-3 ug·cm- 2. Standing time for color development is of the order of a few seconds and stability of color measurements exceeds 12 months. The method may be used among other applications in organic compounds chlorinations catalyzed by iron. These systems are complicated due to the coexistence of various complexes. Nevertheless, the method proposed being simple, fast, and not depending on the composition of the chlorination mixture and the amount of methyl ethyl ketone added was found to be suitable.

Estimation of thiamine hydrochloride and sulphite using charge transfer complex reaction

A new spectrophotometric method is used for estimating Thiamine hydrochloride in its pure form and pharmaceutical formulations, the present method depends on the reaction between Thiamine hydrochloride and chrome azurol S to form a red complex which exhibit maximum absorption at 510 nm, the addition of Sulphite to the resulted red complex is bleaching it and this step was used for the determination of Sulphite which is considered an attacker of Thiamine hydrochloride, therefore, this method was developed for determination of Thiamine hydrochloride in presence of Sulphite. The linearity of the proposed method was obeyed Beer’s law from 2 to 48 and 0.04 to 2.4 ppm for Thiamine hydrochloride and Sulphite respectively. Also, the method sensitivity was measured by molar absorptivity values 5.9×104 l.mol-1.cm-1 and 1.68×104 l.mol-1.cm-1 for Thiamine hydrochloride and Sulphite respectively. The present method accuracy (average recovery) 100.06% and 100.04% the precision (RSD) of the method is ±0.98 - ±1.27% and ±0.76 - ±1.47 of Thiamine hydrochloride and Sulphite respectively. This method was applied for the estimation of B1 and SO32- in pharmaceutical preparations and various water samples respectively.