Acetylacetone-formaldehyde reagent for the spectrophotometric determination of some sulfa drugs in pure and dosage forms

Paper-based analytical device for sensitive colorimetric determination of sulfonamides in pharmaceutical samples

Sulfa drugs are frequently used to treat infections, particularly in antibiotic resistant people. There are several techniques available to determine sulfa drugs, however, they are laborious operation, reagent consumption, expensive, and need specialized types of equipment. Here, a new, very simple and inexpensive paper-based analytical device described for the determination of five sulfa drugs: sulfacetamide, sulfadiazine, sulfamerazine, sulfamethoxazole, and sulfathiazole in pharmaceutical preparations. The method is a one-step reaction, based on the colorimetric reaction between acid-hydrolyzed sulfa drugs and 4-dimethylaminobenzaldehyde. Using a smartphone, the RGB value of color intensity was used as an analytical signal. The paper-based device displayed linear ranges of 0.10-5.00 µg mL-1, linear correlations ranging from 0.9903 to 0.9972, limits of detection 0.0030 to 0.0082 µg mL-1, and RSD of ≤0.258 under optimal conditions. The suggested approach was applied for determining five sulfa drugs in pharmaceutical formulations. This approach is appropriate for pharmaceutical applications since it is inexpensive, simple to utilize, sensitive, and selective.

A newly designed sticker-plastic sheet platform and smartphone-based digital imaging for protein assay in food samples with downscaling Kjeldahl digestion

A low-cost and reliable analytical method based on the combination of a newly designed sticker-plastic sheet platform, digital image-based colorimetry and down scaled Kjeldahl digestion is proposed for the determination of protein content in food samples. The yellowish-brown colloidal products, obtained from the reaction between the ammonium-nitrogen after digestion and the working Nessler's reagent on the miniaturized sticker-plastic sheet platform, were captured for imaging with a smartphone camera. The operational parameters and reaction conditions were optimized. A down scaled Kjeldahl digestion procedure was performed using the newly designed digestion block. The parameters influencing the digestion efficiency, including the mass of the sample, volume of acid, mass of the catalyst and digestion time, were evaluated. Under the selected conditions, a linear calibration in the range of 5-60 mg L^-1 ammonium-nitrogen was obtained with limits of detection and quantification of 2.8 and 7.6 mg L^-1, respectively. The repeatability and reproducibility were 6.7% and 8.8%, respectively. The accuracy of the proposed method was evaluated by applying the developed procedure for milk powder and feeding stuff reference materials and comparing it with the conventional Kjeldahl method. The proposed method was successfully applied for the determination of protein contents in soy foods and protein-based foods. The results agreed well with those obtained from the conventional Kjeldahl method.

Spectroscopic investigation of π-acceptors in the determination and photoinduced degradation of Sulfacetamide

The presence of expired and unused Sulfacetamide (SA) drug in water led to a global need for the development of effective advanced method for the quantitative analysis and for minimizing its occurrence in the nature. To find new effective photochemical decomposition method close to that obtained by the well-known Fenton reaction, the photodegradation of SA was investigated in presence of dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and/or other common additives at two different wavelengths (365 and 256 nm). The role of DDQ in the degradation process of SA was evaluated in comparison to the other investigated π-acceptor systems (Chloranilic acid (CHL) and Picric acid (PA)). While the photodegradation process of SA was hardly to proceed in the absence of a catalyst and/or additive, addition of DDQ and NaNO₂ to the solution of SA induced decomposition of about 94% of SA within 25 min upon the exposure to light source at 256 nm. On the other hand, SA was quantitatively analyzed by recording the absorbance of its charge transfer (CT) products with DDQ, CHL and PA at a certain wavelength. CHL is preferred with concentrated samples of SA, while PA is recommended for diluted samples of SA. SA → DDQ has a widely range of stability over the pH range of 4.5-12.0. While SA → CHL is stable only in the acidic medium (pH = 4.8-5.6), SA → PA is steady in the basic medium (pH = 7.5-11.0). The nature of the DDQ CT complex was investigated in the solid state. The electronic structures of the complexes were studied by calculating the time dependent density functional theory (TDDFT) spectra.

Sensitive inexpensive spectrophotometric and spectrofluorimetric analysis of ezogabine, levetiracetam and topiramate in tablet formulations using Hantzsch condensation reaction

Two highly sensitive, simple and selective spectrophotometric and spectrofluorimetric assays have been investigated for the analysis of ezogabine, levetiracetam and topiramate in their pure and in pharmaceutical dosage forms. The suggested methods depend on the condensation of the primary amino-groups in the three drugs with acetylacetone and formaldehyde according to Hantzsch reaction yielding highly fluorescent yellow colored dihydropyridine derivatives. The reaction products of ezogabine, levetiracetam and topiramate were measured spectrophotometrically at 418, 390 and 380nm or spectrofluorimetrically at λ_em/ex of 495/425nm, 490/415nm and 488/410nm, respectively. Various experimental conditions have been carefully studied to maximize the reaction yield. At the optimum reaction conditions, the calibration curves were rectilinear over the concentration ranges of 8-25, 60-180 and 80-200μg/mL spectrophotometrically and 0.02-0.2, 0.2-1.2 and 0.2-1.5μg/mL spectrofluorimetrically for ezogabine, levetiracetam and topiramate, respectively with good correlation coefficients. The suggested methods were applied successfully for the analysis of ezogabine, levetiracetam and topiramate in their commercial tablets with high percentage recoveries and negligible interference from various excipients in pharmaceutical dosage forms. The results were statistically analyzed and showed the absence of any significant difference between both developed and published methods. The procedures were validated and evaluated by the ICH guidelines revealing good reproducibility and accuracy. Therefore, the two proposed methods may be considered of high interest for practical and reliable analysis of ezogabine, levetiracetam and topiramate in pharmaceutical dosage forms.

A sensitive method for the determination of Sulfonamides in seawater samples by Solid Phase Extraction and UV-Visible spectrophotometry

The authors have developed a sensitive spectrophotometric method for determination of sulfonamide derivatives such as sulfanilamide (SAA), sulfadiazine (SDZ), sulfacetamide (SCT) sulfamethoxazole (SMX), sulfamerazine (SMR), sulfadimethoxine (SDX), sulfamethiazole (SMT) and Sulfathiazole (STZ). This method is based on the Bratton-Marshall reaction, which involves the diazotization of sulfonamides with sodium nitrite under acidic conditions, followed by coupling with N-(1-naphtyl) ethylenediamine dihydrochloride (NED) to form a pink colored compound. Therefore, the Bratton-Marshall method was modified by optimizing the reaction conditions, which allows us to determine a low concentration range of sulfonamides compared to the reported methods. The limits of detection and quantification obtained were 0.019-0.05 and 0.06-0.16μgmL^-1, respectively. In comparison with other reported methods using different coupling agents, the proposed method was found to be the most simple and sensitive for sulfonamides determination. In this paper, the modified method was successfully employed for the determination of sulfonamides in drinking water, seawater and pharmaceutical and veterinary formulations. The purpose of this work is to optimize and develop a simple method for extraction and concentration of sulfonamides present as residues in seawater and their quantification with the recommended spectrophotometric method. Solid phase extraction (SPE) of sulfonamides from seawater samples was evaluated using Oasis HLB cartridges (3mL, 540mg). The recovery efficiency was investigated in the sulfonamides concentration range comprised between 0.19 and 126ngmL^-1. The ease of use of this extraction method makes it very useful for routine laboratory work.

Compatible validated spectrofluorimetric and spectrophotometric methods for determination of vildagliptin and saxagliptin by factorial design experiments

Simple, selective and reproducible spectrofluorimetric and spectrophotometric methods have been developed for the determination of vildagliptin and saxagliptin in bulk and their pharmaceutical dosage forms. The first proposed spectrofluorimetric method is based on the dansylation reaction of the amino group of vildagliptin with dansyl chloride to form a highly fluorescent product. The formed product was measured spectrofluorimetrically at 455 nm after excitation at 345 nm. Beer's law was obeyed in a concentration range of 100-600 μg ml(-1). The second proposed spectrophotometric method is based on the charge transfer complex of saxagliptin with tetrachloro-1,4-benzoquinone (p-chloranil). The formed charge transfer complex was measured spectrophotometrically at 530 nm. Beer's law was obeyed in a concentration range of 100-850 μg ml(-1). The third proposed spectrophotometric method is based on the condensation reaction of the primary amino group of saxagliptin with formaldehyde and acetyl acetone to form a yellow colored product known as Hantzsch reaction, measured at 342.5 nm. Beer's law was obeyed in a concentration range of 50-300 μg ml(-1). All the variables were studied to optimize the reactions' conditions using factorial design. The developed methods were validated and proved to be specific and accurate for quality control of vildagliptin and saxagliptin in their pharmaceutical dosage forms.

A sensitive spectrophotometric method for the determination of sulfonamides in pharmaceutical preparations

A new, simple and sensitive spectrophotometric method for the determination of some sulfonamide drugs has been developed. The method is based on the diazotization of sulfacetamide, sulfadiazine, sulfaguanidine, sulfamerazine, sulfamethazine, sulfamethoxazole, and their coupling with 8-hydroxyquinoline in alkaline media to yield red coloured products with absorption maxima at 500 nm. Beer's law is obeyed from 0.1-7.0 microg mL-1. The limits of quantification and limits of detection were 0.11-0.18 and 0.03-0.05 microg mL-1, respectively. Intraday precision (RSD 0.1-0.5%) and accuracy (recovery 97.3--100.8%) of the developed method were evaluated. No interference was observed from common adjuvants. The method has been successfully applied to the assay of sulpha drug in pharmaceutical formulations.

Iminodibenzyl as a novel coupling agent for the spectrophotometric determination of sulfonamide derivatives

A rapid, selective and simple spectrophotometric method for the determination of sulfa-drugs is described. The method is based on the formation of violet colored azo product by the diazotization of sulfonamides, viz. sulfathiazole (SFT), sulfadiazine (SFD), sulfacetamide (SFA), sulfamethoxazole (SFMx), sulfamerazine (SFMr), sulfaguanidine (SFG) and sulfadimidine (SFDd) followed by a coupling reaction with iminodibenzyl in alcohol medium. Absorbance of the resulting violet azo product is measured at 570-580 nm and is stable for 24 h at 27 degrees C. Beer's law is obeyed in the concentration range of 0.05-6.0 microg ml(-1) at the wavelength of maximum absorption. The method is successfully employed for the determination of sulfonamides in various pharmaceutical preparations and common excipients used as additives in pharmaceuticals do not interfere in the proposed method. The method offers the advantages of simplicity, rapidity and sensitivity without the need for extraction or heating. A reaction mechanism is proposed for the formation of the violet azo product.