Colorimetric Determination of Benzocaine, Lignocaine and Procaine Hydrochlorides in Pure Form and in Pharmaceutical Formulations Using p-Benzoquinone

A simple, fast, and cost-effective smartphone-based digital imaging method for quantification of lidocaine hydrochloride in pharmaceutical formulations

OBJECTIVE

A simple, highly specific, accurate and fast method by smartphone-based digital imaging was developed for estimating lidocaine hydrochloride in pharmaceutical formulations.

MATERIAL AND METHODS

To obtain the images, a Galaxy A03 Core smartphone and an image acquisition device developed in the laboratory were used to control the incident factors in reproducibility of the measurements. The processing of the images was carried out with the Color Grab application. Finally, the absorbance values were calculated using the RGB intensity values of blank, standard, and sample solutions. The proposed method was compared with spectroscopic and chromatographic methods.

RESULTS

The reaction between copper and lidocaine hydrochloride was characterized, showing better results in an equimolar ratio and maintaining the pH of the solution above 11.5. The use of the device for the capture of digital images allowed to control those sensitive parameters for reproducibility so that the analytical measurements showed adequate precision and accuracy. Validation of the main parameters of the method showed compliance with acceptance criteria. The application of the method for the analysis of injectable samples achieved reliable results, which were statistically similar to other reference instrumental methods.

CONCLUSION

The proposed method presented figures of merit in relation to linearity, precision, selectivity, accuracy, and robustness; it was carried out by designing and manufacturing a device for capturing digital images on a smartphone, which were analyzed to obtain RGB intensity values. These data are finally used to calculate absorbance values of solutions. All these elements provide this work with innovative characteristics in the field of analysis for control of pharmaceutical formulations.

Determination of Benzocaine in Pharmaceutical Formulations by Indirect SERRS Assay Combined with Azo Coupling

Coupled with an azo coupling reaction, a simple, rapid, sensitive, and effective surface-enhanced resonance Raman scattering (SERRS) detection method for benzocaine was developed. In our study, benzocaine which is used clinically as a local anesthetic was derived with p-aminothiophenol into a corresponding azo product within 5 min, resulting in a strong SERRS response with the simple addition of Ag NPs excited with a 532 nm laser. The linear correlation between SERRS intensity of dominant bands and logarithm of benzocaine concentration was investigated for quantitative determination. The method reached a limit of detection (LOD) down to 0.139 and 0.0788 μg/mL calculated with two peak intensity ratios (I1568/I2260 and I1331/I2260), which is comparable to most studies reported previously, and meanwhile had superiority in simplicity and rapidness. The quantitative measurements for pharmaceutical preparations with benzocaine were conducted without complex extraction and enrichment processes. It was indicated that the SERRS assay combined with azo derivatization reaction has implications for practical applications in more complicated systems involving biological samples, in which appropriate and simplified pretreatments were conducted to remove interfering components.

Development and Characterization of Films for Food Application Incorporating Porphyran Extracted from Porphyra dioica

Non-biodegradable plastic is one of the biggest environmental problems of our lifetime and, considering the present societal needs, it will get worse. Consequently, there is an urgent need to develop sustainable and renewable alternatives to plastic, such as plastic-like materials obtained from biodegradable polymers, namely sulfated polysaccharides, considered one of the most viable alternatives. There is also a need to obtain these materials in an environmentally and economically sustainable way. The hereby developed process of obtaining film-forming solutions from semi-refined porphyran (PorphSR) uses a green solvent (hot water) with a high extraction yield of semi-refined porphyran (26.66 ± 0.27%) in a reproducible way and with low levels of contaminants. The obtained semi-refined porphyran showed good antioxidant potential in all tests performed: HPSA (Δ0.066 ± 0.002), DPPH (2.23 ± 0.78%), FRAP (0.420 ± 0.014 eq. ascorbic acid µg mg−1 of extract) and ABTS (20.46 ± 0.90%). After being cast into films, the most notable antioxidant properties were those of the semi-refined porphyran in the DPPH, FRAP and ABTS assays and of the pectin, (PorphSR_PcT and PorphSR_PcT_Gly) in the HPSA assay. Morphologically, the films showed relatively homogeneous and low roughness surfaces. It is concluded that the described method to obtain semi-refined porphyran is feasible and reproducible, and that the developed films, mainly PorfP2_PcT_Gly, proved to be a potential candidate for non-biodegradable plastic substitutes.

New spectral resolution techniques for resolving and determining the components in binary fixed-dose combinations

Four spectrophotometric approaches were performed to determine a binary combination of Phenazone and Benzocaine in pure powder form and in pharmaceutical formations. This investigation submits the application of four techniques contingent on the presence of the extended area of the spectra of one compound in the binary mixture, these methods include Absorptivity Centering (a-centering), Absorbance Subtraction (AS), Amplitude Modulation (AM) and Concentration Value (CV). The linearity range for the above-mentioned approaches was found to be 3.0-15.0 μg/mL for Benzocaine in a-centering method and 3.0-30.0 μg/mL for Benzocaine and Phenazone in other advanced methods. The four techniques were evaluated as per ICH criteria and were successfully utilized for the determination of Phenazone and Benzocaine existing in pharmaceutical formulations. All results gained by the submitted approaches were statistically compared with a previously published method, and no important differences were detected.

Spectrophotometric and electrical studies of charge transfer complexes of 2-amino-1,3,4-thiadiazole with pi-acceptors

Charge transfer (CT) complexes formed between 2-amino-1,3,4-thiadiazole as donor and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), p-chloranil (p-CHL), o-chloranil (o-CHL), p-bromanil (BRL) and chloranilic acid (CHA) as acceptors, have been studied spectrophotometrically. Benesi-Hildebrand and Job continuous variation methods were applied to the determination of association constant (K), molar extinction coefficients (epsilon), dipole moment and stoichiometric ratio, respectively. The solid CT complexes have been synthesized and characterized by different spectral methods. The spectral changes reveal that the CT interaction depends on the type of the acceptors. The magnetic properties of the various complexes were also investigated. The electrical properties for the solid CT complexes are measured from which the activation energies are calculated.