Formation Of Azo Dye Research Articles

Chromium speciation from tannery wastewater using spectroscopic techniques

The toxicity and reactivity of chromium (Cr) depend on its chemical form or oxidation state which directs the significance of chromium speciation. Cr(VI) is a ‘Class A’ carcinogen whereas Cr(III)) is considered as essential for metabolism. In this work, concentrations of Cr species in different sampling sites of a tannery effluent have been spectroscopically determined. Cr(VI) was determined by UV-visible spectrophotometer through azo dye formation. Total Cr was determined by FAAS while Cr(III) was through subtraction. The Cr(IV) concentration before and after treatment was found in close proximity since the wastewater treatment process was evidently not effective at reducing the level of Cr(IV) in the waste stream (i.e., 3.34 mg/ L versus 3.15 mg/L). The Cr(VI) concentration after treatment (3.15 mg/L) is more than 31 times higher than the permissible limit of WHO (0.1 mg/L). Furthermore, the concentration of Cr(VI) in the downstream of the receiving river (0.59 mg/L) is more than 12 times higher than the upstream (0.046 mg/L) while Cr(III) in the downstream (25.73 mg/L) is more than 50 times higher than the upstream concentration (0.51 mg/L), confirming that the pollution of the river is from the tannery effluent.

Spectrophotometric determination of Meloxicam in Pure Form and its Pharmaceutical Formulation following azo dye formation with 4-nitroaniline

A fast, cheap, and straightforward spectrophotometric method has been proposed to determine meloxicam (MEL) in its pure form and pharmaceutical formulation. The technique involves diazotizing the (NH2) group in 4-nitroaniline with NaNO2 followed by a reaction with meloxicam to produce a stable and colored complex in a basic medium. This complex demonstrates maximum absorbance at 514 nm. The developed method's linearity ranges from 2.0 - 25 μg mL-1, and the molar absorptivity is 1.5989×104 L mol-1 cm-1. The RSD% is lower than 1.55%. Additionally, the limit of detection (LOD) is 0.2019 μg mL-1. The method successfully determines the pharmaceutical preparation containing meloxicam (Loxim tablets) with a recovery rate of no less than 97.9%.

Synthesis, characterization, and dyeing performance of Novel Bisazo disperse dyes: A combined spectroscopic and computational study

Disperse dyes are a versatile class of coloring agents with applications spanning textiles to advanced optical materials. This study details the synthesis and spectroscopic characterization of innovative bisazo disperse dyes, which are derived from benzidine-based compounds. The synthetic process involves the use of two distinct couplers, namely acetylacetone and ethyl acetoacetate. The reaction of these couplers with benzidine derivatives yields two specific bisazo dyes: diethyl 2,2′-(2,2′-([1,1′-biphenyl]-4,4′-diyl)bis(hydrazin-2-yl-1-ylidene))bis(3-oxobutanoate) 3 and 3,3′-(2,2′-([1,1′-biphenyl]-4,4′-diyl)bis(hydrazin-2-yl-1-ylidene))bis(pentane-2,4‑dione) 4. The reaction of these azo compounds with hydrazine and phenylhydrazine results in the formation of azo dyes that incorporate a pyrazole ring 5–7. All the disperse azo compounds were characterized and identified through various spectroscopic methods, including UV-visible, FT-IR, NMR (both 1H and 13C), and elemental analysis. Examining the UV–vis profiles of the disperse dyes 3–7 revealed the maximum absorbance values (λmax) were affected by the change of the coupler moieties and more significant sensitivity to changes in pH. The polyester fabric (PE-F) was dyed by disperse dyes 3–7 in presence of the dispersing agent DYEWELL-002 and the fastness data were measured according to the standard procedures. The color strength (K S-1) and exhaustion (%E) values of the dyed fabrics are calculated and discussed. The synthesised bisazo dyes were subjected to computational calculations using DFT with B3LYP method and 6–31G(d,p) basis set to examine the dyeing efficiencies and anticipate the mechanism of the dyeing process. The computational analyses assessed the dipole moment, chemical reactivity descriptors and molecular electrostatic potential. Analysis of the chemical descriptor parameters revealed that the highest dyeing strength was exhibited by dye 3, as indicated by the ELUMO, EHOMO, ∆E, S, and η parameters, while dye 6 had the highest dyeing strength based on the values of χ and µ parameters.

Colorimetric analysis based on solid-phase extraction with sedimentable dispersed particulates: demonstration of concept and application for on-site environmental water analysis.

A novel simple and functional colorimetric methodology for on-site environmental water analysis was proposed. This method combines coloration of the analyte and extraction of the colored species on dispersed particulates during their sedimentation in the same container. The whole analysis can be performed within 15 min by comprising the addition of 1 mL of sample solution into a 1.5-mL microtube containing the powders of coloring reagents and the sedimentable fine particulates as an adsorbent. The analyte is determined by comparing the sediment color with the standard color by visual inspection or the color information of the photo image. The potential of this methodology was demonstrated through developing colorimetry for Fe2+ with o-phenanthroline, NO2- by azo-dye formation, HCHO by the MBTH method, and PO43- by the 4-aminoantipyrine method based on the enzyme reactions. The material, size, amount of the adsorbent particles, and other conditions were optimized for each analytes. The advantages of the methodology were as follows: high sensitivity, easy controllability of the sensitivity over the wide range by the amount, size, and material of the particulates, lower interference from the colored matrix components due to obtaining the color data from not the aqueous phase but the sedimented particulates, and acceleration of the color development rate by the particulates as seen in NO2- determination as consequence shorten the operation time. A simple device equipped with twin cells was proposed for on-site analysis which contains two successive different coloring operations. The developed methods were successfully applied to the environmental water samples with the good agreement of the results with those by the usual instrumental methods.

Development of a simple analytical method for the determination of nitrite in waters using redox reaction and smartphone.

In this study, it was aimed to perform the colorimetric determination of nitrite in waters using the redox reaction of iodide in acidic conditions with smartphone. The simple redox reaction of iodide and nitrite in an acidic medium was used instead of the conventional nitrite methods based on the formation of azo dye. The quantitative relationship between the yellow-colored iodine formed because of the reaction and nitrite was determined by the digital image-based colorimetric method (DIC). In the optimal experimental conditions, detection limit and R2 values were determined as 0.02mg/L and 0.9925, respectively. New method (Redox-DIC method) was validated by the standard Griess Method for nitrite in lake waters. The perfect recovery results (94-112%) were calculated for lake, river, tap, and spring waters spiked at different concentrations, and very good (< 5.0%) percent relative standard deviation values were recorded. Unlike conventional nitrite methods, organic reagents and solvents were not used in this method. The method is fast, simple, and low cost.

Dispersive liquid‐liquid microextraction followed by magnetic nanoparticles retrieval of extract for separation and preconcentration of tetracycline from real samples before its selective spectrophotometric determination based on azo dye formation

AbstractA sensitive and selective method is reported for the determination of the low amount of tetracycline in real samples. The tetracycline is extracted and preconcentrated by dispersive liquid‐liquid microextraction followed by retrieval of the extract with magnetic solid‐phase extraction. The extracted analyte is determined by a selective spectrophotometric method based on the formation of a water‐soluble violet mono azo dye between the tetracycline and diazotized p‐nitroaniline in the basic medium. The dispersive liquid‐liquid microextraction was performed using acetonitrile as the disperser solvent and 1‐octanol as the extracting solvent. The extracted tetracycline in the dispersive liquid‐liquid microextraction step was retrieved by dispersed hydrophobic oleic‐acid‐modified Fe3O4 magnetic nanoparticles. Thus, the method enjoyed the high surface area and strong magnetism properties of these nanoparticles avoiding the time‐consuming centrifugation or column‐passing processes. Finally, the tetracycline was eluted from the magnetic solid phase into 0.5 ml of ethanol, and coupled with diazotized p‐nitroaniline in the basic medium for spectrophotometric quantification. Under the optimum conditions, good linearity (in the range of 7.6–650.0 μg/L with R2 = 0.9987), low detection limit (2.3 μg/L), and preconcentration factor of 30.0 were obtained. The proposed method was successively applied to the determination of tetracycline in different samples.

Spectrophotometric Analysis of Vancomycin Hydrochloride in Pure and Pharmaceutical Injections via Batch and Cloud Point Extraction Techniques

Development of a precise and delicate reaction has been acquired for the determination of vancomycin hydrochloride using batch and cloud point extraction (CPE) methods. The first method is based on the formation of azo dye as a result of diazotized dapsone coupled with vancomycin HCl (VAN) in a basic medium. The sensitivity of this reaction was enhanced by utilizing a nonionic surfactant (Triton X-114) and the cloud point extraction technique (second method). The azo dye formed was extracted into the surfactant-rich phase, dissolved in ethanol and detected at λmax 440 nm spectrophotometrically. The reaction was investigated using both batch and CPE methods (with and without extraction), and a simple comparison between the two developed methods was made. The conditions that affect the extraction process and the sensitivity of the methods have been carefully examined. The linearity of the calibration curves was in the range of 3-50 and 0.5- 25 µg.mL-1 with limits of detection of 0.806 and 0.462 µg.mL-1 for VAN in both batch and CPE procedures, respectively. The percentage of relative standard deviation (R.S.D.%) for the two methods was better than 2.54% and 2.83%, respectively. The recommended procedures have been effectively used to assay VAN in commercial injections.

A thermodynamic study for the stability of some aromatic complexes formation derived from the reaction of 4-dimethyl amino benzaldehyde with diazotized dinitro aniline reagents.

Abstract The basis of this research includes the preparation of aromatic azoimine complexes resulting from the coupling reaction (4) of Schiff bases with diazotized dinitroaniline reagent. Ultraviolet spectra, infrared spectra, and melting points are among the most important physical methods used to identification the right compounds prepared in this study. After that, the stoichiometric ratios of the components of the complex were determined using the molar ratio method, and we got a ratio of (1:1) for all the studied complexes. Finally, the factors that affect the stability constant values were studied, namely: A-Effect of acidity function: These stability constants were studied for each of the prepared complexes at each acidic function (pH) and different temperatures, and we obtained values for the stability constants, which are evidence of the preparation of stable azo complexes. B-The effect of temperature: These stability constants were calculated at a range of temperature (313–273oK) which allowed us to know that the reactions of formation of azo dyes are spontaneous and exothermic from the negative values of (∆G and ∆H) respectively, as well as the negative (∆S) value that supports what was mentioned previously. C-Effect of Structure: The location and the type of function group also has an effect on the values of the stability constants of the prepared complexes, and this was proved by the variation in the values of the stability constants.

Dispersive liquid–liquid microextraction and diffuse reflectance-Fourier transform infrared spectroscopy for iodate determination in food grade salt and food samples

A novel method based on diffused reflectance Fourier-transform infrared spectroscopy (DRS-FTIR) was employed for iodate determination in food grade salt and food products. The method attained sensitivity that was comparable to or better than that in most of the contemporary spectrophotometric methods. This was realized through a combination of azo dye formation and dispersive liquid–liquid microextraction of dye when a 37-fold enrichment was obtained. FT-IR enabled integrating alternative target peak, and freedom in sample solvent composition relative to UV–visible spectrophotometry where the solvent polarity, pH, and presence of ions may affect the spectral properties of the measurable coloured species. Food samples containing iodide or covalently bonded iodine were oxidized with alkaline permanganate for mineralization and iodate formation. Optimization of both reaction conditions was carried out by means of response surface methodology. The method had a linear range 0.04–10 mg kg−1 iodate and limit of detection of 4.4 µg kg−1.

Determination of Nitrite in Meat by Azo Dye Formation

A nitrite has been determined by developing a simple and sensitive spectrophotometric method which is involve the reaction between nitrite and ρ-bromoaniline to form the corresponding diazonium ion which is afterward coupled with salbutamol in the presence of ammonia solution to form a yellow water-soluble and stable azo dye showing maximum absorption at 442 nm. A 0.1 - 3 μg NO2-/10 mL is follow of Beer's law, i.e., 0.1 - 3.0 ppm with Sandell's sensitivity index of 4.24 × 10-4 µg.cm-2 and e, the molar absorptivity of 1.08606 × 105 L.mol-1. cm-1. The limit of detection and the limit of quantitation is calculated for determination of nitrite which is 0.0199 µg.ml-1 and 0.0274 µg.ml-1 severally. The applicability of this method has been tested by as saying nitrite in curing meat samples.

A Novel method of CFIA/Merging zones technique for assay of Doxycycline in bulk and pharmaceutical preparation depending on Azo dye formation

A Novel method of CFIA/Merging zones technique for assay of Doxycycline in bulk and pharmaceutical preparation depending on Azo dye formation

4-Nitrophenol imprinted core-shell poly(N-isopropylacrylamide-acrylic acid)/poly(acrylic acid) microgels loaded with cadmium nanoparticles: A novel catalyst

4-nitrophenol imprinted poly(N-isopropylacrylamide-acrylic)/poly(acrylic acid) [p(NIPAM-AAc)/p(AAc)] microgels are synthesized by precipitation polymerization. 1 and 95 mol % of AAc is incorporated in core and shell of synthesized microgels respectively, so that shell can be swollen up to large extent instead of core part. Cd nanoparticles are synthesized within core using in situ reduction. Size of Cd nanoparticles and structure of microgels are analyzed by STEM, FTIR and UV–Vis spectroscopy. Series of 4-NP and its derivatives (nitroarenes and azo dyes) are reduced by using synthesized microgel as catalyst in aqueous medium. Significant difference in apparent rate constant (kapp), percentage reduction and reduction time among 4-NP and its derivatives is observed. This shows that 4-NP imprinting has affected the sieve of microgels and orientation of carboxyl groups (COOH) of AAc. Effect of solvents on catalytic reduction of 3-NP is also studied using synthesized microgel as catalyst. Significant difference in kapp, percentage reduction and reduction time of 3-NP in different solvents is also observed. 95% AAc in imprinted shell is observed as capable catalyst for reduction of 4-NP template and its derivatives. Synthesized microgel has multiple features: 4-NP imprinting, core-shell structure and 95% AAc in shell. All of these features are helped in the catalytic reduction of nitro compounds. The compounds similar to 4-NP are reduced more as compared to other compounds due to 4-NP imprinting. This shows that synthesized MIP is more effective for reduction of compounds similar to 4-NP. High mol percentage of AAc monomer within shell is facilitated the diffusion of substrates towards nanoparticles embedded in core. Possible product formation of nitroarenes and azo dyes in the presence of microgel was reported. Effect of different solvents on catalytic reduction of 3-NP is also observed.

Nitrate/Nitrite determination in water and soil samples accompanied by in situ azo dye formation and its removal by superabsorbent cellulose hydrogel

In the present work, an efficient method is developed for the spectrophotometric determination of nitrite and nitrate ions in water and soil samples by in situ formation of azo dye (Griess reagent) which showed λmax at 385 nm. The reaction condition and the concentration of reagents used are optimized. The molar absorptivity, Sandell’s sensitivity, detection limit and quantification limit of the method are found to be 3.22 × 104 L mol−1 cm−1, 1.98 × 10−6 µg cm−2, 0.0030 µg mL−1 and 0.0092 µg mL−1 respectively with the linearity range up to 2.6 µg mL−1. The formation of azo dye is confirmed by 1H and 13C Nuclear Magnetic Spectroscopy. The azo dye formed during the determination is effectively removed using custom made ecofriendly cellulose modified hydrogel in order to reduce organic load in the test samples. The structure, morphology and the thermal properties of hydrogel are determined by Fourier-transform infrared spectroscopy, scanning electron microscopy and thermogravimetric analysis respectively. The dye removal mechanism involves pseudo second order kinetics, adsorption is found to be spontaneous based on the thermodynamic parameters and it is befitting to Freundlich isotherm model.

Spectrophotometric Determination of Paracetamol using a Newly Synthesized Chromogenic Reagent 4-[(2-amino-1, 3thiazol-4-yl)amino]nitro benzene

This study describes the new simple and accurate spectrophotometric method for the determination of paracetamol after the formation of azo dye with a new chromogenic reagent 4 [(2-amino-1,3thiazol-4-yl)amino] nitrobenzene to form an orange-coloured product measured at 425 nm. The molecular structure of the newly synthesized compound was confirmed by several spectroscopic techniques such as UV-visible, FTIR, 1HNMR, and mass spectroscopy. Newly synthesized compound was in vitro screened against several bacterial species. The experimental conditions that affect the reaction were carefully optimized and under the optimized conditions, a linear relationship was obtained in the concentration range of 5–25mg.L−1 of paracetamol. A reaction with a new chromogenic reagent has been occurred at a stoichiometric ratio of 1:1. This method has a limit of detection of 1.334 mg.L-1 and Sandell's sensitivity of 0.0235 mg.cm-1 for new azo dye product.

Sensitive assay of pharmaceutical amines in environmental samples and formulations by oxygenated graphene quantum dots

Oxygenated graphene quantum dots (GQDs) were prepared and used as a new colorimetric reagent for analysis of pharmaceutical amines. Citric acid was thermalized to prepare GQDs with functional groups along their edges. The prepared GQDs were used as a coupling reagent in an azo dye formation for dapsone (DAP) and metoclopramide (MET) determination. The characterization was done by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, X-ray diffraction spectroscopy, Energy dispersive X-ray spectroscopy, EDX-mapping, dynamic light scattering, photoluminescence spectroscopy, Raman and FT-IR spectroscopy. DAP and MET were diazotized by nitrite to their related diazonium cations in acidic condition through a flow injection manifold. Then they were coupled to GQDs to produce the yellow colored products. Detection of the products was performed by spectrophotometry at 423 nm. Various chemical and instrumental parameters were optimized by a univariate procedure and a central composite design (CCD) chemometrics approach. The analytical method showed the linear calibrations for DAP and MET in the ranges of 0.03–20 and 0.1–40 µg mL−1, respectively. The limit of detection for both DAP and MET was of 0.01 µg mL−1, respectively. The inter-day experiments showed a satisfactory robustness of the method for determination of DAP and MET. The sample throughput found in this method was about 60 h−1. Lake, river and well water samples as well as soil samples along with some pharmaceutical formulations were analyzed.

Electrochemical behavior study of salicylic acid following azo dye formation with 2,4-dinitrophenylhydrazine: Analytical evaluation

A new simple, accurate and cost-effective chronoamperometry (CA) - based approach coupled with azo coupling reaction has been put forward for quantitative analysis of salicylic acid. The reaction involves a two-step process of oxidation of the 2,4-dinitrophenylhydrazine (DNPH) by potassium iodate to give a 2,4-dinitrophenylhydrazinium cation at 0–5 °C and coupling with salicylic acid (SA) to form red salicylic acid-derived azo dye. Electrochemical impedance spectroscopy, square wave voltammetry and chronoamperometry methods were used to characterize the electrochemical behavior of the salicylic acid-derived azo dye. Studies on different variables affecting the reaction were optimized. Under the optimal conditions, amperometric studies showed that the current response exhibits a wide linearity range from 0.1 to 0.0005 mmol L−1 for SA and the limit of detection and quantification are found to be 0.0001 and 0.0015 mmol L−1 (S/N = 3 & 10) respectively. Therefore, the developed method was successfully applied for routine determination of SA in pharmaceutical samples.

Spectrophotometric Method for the Determination of Metronidazole in Pharmaceutical products based on the Formation of Azo dye

Two simple, rapid, sensitive and accurate spectrophotometric methods have been developed for the estimation of metronidazole. The method depends on the reduction of Metronidazole molecule with zinc powder and hydrochloric acid followed by diazotization and coupling with 2-hydroxybenzaldehyde to give yellow colored in alkaline medium with an absorption maximum at 457 nm. Under optimized experimental conditions Beer's law was obeyed in the concentration ranges 3.0 to 15.0 μg/ml and 25.0 to 37.0 μg/ml. Also, by using p-aminoacetophenone as a coupling agent to form orange colored with an absorption maximum at 490 nm. Beer's law was obeyed in the concentration ranges 3.0 to 40.0 μg/ml. The Sandell's sensitivity, the molar absorptivity, correlation coefficient, detection limit and the regression equation were calculated. Both techniques were applied successfully to a wide variety of pharmaceutical preparations

Microchemical Plant in a Liquid Droplet: Plasmonic Liquid Marble for Sequential Reactions and Attomole Detection of Toxin at Microliter Scale.

Miniaturizing the continuous multistep operations of a factory into a microchemical plant offers a safe and cost-effective approach to promote high-throughput screening in drug development and enforcement of industrial/environmental safety. While particle-assembled microdroplets in the form of liquid marble are ideal as microchemical plant, these platforms are mainly restricted to single-step reactions and limited to ex situ reaction monitoring. Herein, we utilize plasmonic liquid marble (PLM), formed by encapsulating liquid droplet with Ag nanocubes, to address these issues and demonstrate it as an ideal microchemical plant to conduct reaction-and-detection sequences on-demand in a nondisruptive manner. Utilizing a two-step azo-dye formation as our model reaction, our microchemical plant allows rapid and efficient diazotization of nitroaniline to form diazonium nitrobenzene, followed by the azo coupling of this intermediate with target aromatic compound to yield azo-dye. These molecular events are tracked in situ via SERS measurement through the plasmonic shell and further verified with in silico investigation. Furthermore, we apply our microchemical plant for ultrasensitive SERS detection and quantification of bisphenol A (BPA) with detection limit down to 10 amol, which is 50 000-fold lower than the BPA safety limit. Together with the protections offered by plasmonic shell against external environments, these collective advantages empower PLM as a multifunctional microchemical plant to facilitate small-volume testing and optimization of processes relevant in industrial and research contexts.

Nitric Oxide Sensing through Azo-Dye Formation on Carbon Dots.

Carbon dots (C-dots) prepared through heating of aminoguanidine and citric acid enable bimodal (colorimetric and fluorescence) detection of nitric oxide (NO) in aqueous solutions. The C-dots retained the functional units of aminoguanidine, which upon reaction with NO produced surface residues responsible for the color and fluorescence transformations. Notably, the aminoguanidine/citric acid C-dots were noncytotoxic, making possible real-time and high sensitivity detection of NO in cellular environments. Using multiprong spectroscopic and chromatography analyses we deciphered the molecular mechanism accounting for the NO-induced structural and photophysical transformations of the C-dots, demonstrating for the first time N2 release and azo dye formation upon the C-dots' surface.

Silver Nanoparticles and Metallic Silver Interfere with the Griess Reaction: Reduction of Azo Dye Formation via a Competing Sandmeyer-Like Reaction.

Silver (Ag) is the most common nanomaterial (NM) in consumer products. Much research has been focused on elucidating the potential impact of Ag-containing NMs on human health, e.g., cytotoxicity, genotoxicity, or proinflammatory responses. In the case of proinflammatory responses, a frequently used end point is the induction of nitric oxide (NO), which is indirectly quantified as nitrite (NO2-) with the Griess reaction. After preliminary studies in a macrophage-like cell culture system showed anomalous false negative results in the presence of silver nanoparticles (Ag NPs), we studied the influence of Ag on the detection of NO2- in a cell-free environment. Solutions containing a known concentration of NaNO2 were prepared in H2O, PBS, or complete cell culture medium (CCM) and analyzed using the Griess reaction in the presence of Ag in its metallic or ionic state. In Milli-Q H2O, the impact of salts on the detection was investigated using NaCl and KBr. After completion of the Griess reaction, the samples were analyzed spectrophotometrically or chromatographically. It was found that the presence of metallic but not ionic Ag interfered with the quantification of NO2-. The effect was more pronounced in PBS and H2O containing NaCl or KBr. The chromatographical analysis provided evidence of a competing reaction consuming the intermediate diazonium salt, which is critical to the Griess reaction. These findings demonstrate yet another substantial interference of NMs with a frequently used in vitro assay. If gone unnoticed, this interference might cause false negative results and an impaired hazard assessment of Ag NMs.