Indophenol Dye Research Articles

Determination of ammonium and nitrate in soils by digital colorimetry.

A method of digital colorimetric determination of ammonium and nitrate in soils is proposed. The method is based on corresponding photometric procedures of ammonium and nitrate determination after potassium chloride extraction from soil samples. Ammonium is determined as an indophenol dye, and nitrate is determined as an azo dye. The original procedures were modified to overcome the lower sensitivity of the digital colorimetric method. For ammonium determination, the time required for the reaction to proceed completely was studied. Along with the use of a 96-well microplate protected from ambient light by a special frame, mathematical correction of scattered radiation using black ink and taking the images by a scanner in transmission mode without any post-processing, the resulting colorimetric methods proved to provide accuracy and sensitivity close to those of the spectrophotometric method, and the overall analysis speed for tens of samples was even higher. Limits of detection and quantitation for NO3- were 0.42 and 1.4mg/kg, and for NH4+, they were 1.1 and 3.7mg/kg, which is lower than for standard methods. The methods' validity was proven by the analysis of standard samples and by the analysis of soil samples collected in several districts of the Moscow region.

Oxidative Coupling Assay for Mesalazine Determination in Pharmaceuticals and Spiked Human Plasma Utilizing Syringic Acid

This study reports on developing a simple, cost-effective, highly sensitive spectrophotometric method for measuring mesalazine (MSZ). The method utilizes the oxidative coupling of MSZ with syringic acid (4-hydroxy 3,5-dimethoxybenzoic acid) in the presence of dissolved oxygen under alkaline conditions to form a stable indophenol dye with a characteristic blue color, which can be measured at 615 nm. Beer’s law was found to be obeyed over the range of 1.25–50 µg·mL−1, with a molar absorptivity of 0.53 × 104 mol−1·L−1·cm−1. Moreover, the method exhibited excellent sensitivity, with a limit of detection (LOD) of 0.093 µg·mL−1 and a limit of quantitation (LOQ) of 0.282 µg·mL−1. The proposed method was found to be selective, as it could effectively detect MSZ in the presence of certain interfering species. The proposed method was validated according to current ICH guidelines and demonstrated good accuracy, with recoveries ranging between 98 and 100% and a relative standard deviation of less than 0.6%. Overall, this method provides a promising tool for the sensitive and accurate determination of MSZ in its pure form, pharmaceutical formulations, and biological samples.

Methodological considerations of the acetaminophen Detection Kit®: Involvement of molecular oxygen (O2) in an indophenol reaction

The Acetaminophen Detection Kit® (Kanto Chemical Company Co. Inc., Tokyo, Japan) is a colorimetric test based on an indophenol reaction. The test involves three reactions: deproteination of the sample, hydrolysis of acetaminophen to yield p-aminophenol, and coupling p-aminophenol with a derivative of phenol in alkali conditions to form a blue-colored indophenol dye. The kit was devised to accomplish these three reactions with only two reagents, allowing the prompt diagnosis of acetaminophen overdose in emergency medicine.In the user instructions included with the kit and in reports introducing the kit, the chemical composition of the two reagents was not disclosed. Details about the composition can be found in the Safety Data Sheet from the manufacturer; however, there is little explanation about the principle (mechanism) of the coupling reaction. This lack of information appears to have hampered the use of this kit in forensic medicine. In this report, we conducted the coupling reaction by successively adding the two reagents to a p-aminophenol (intermediate molecule) solution with the reaction vessel open to the air and under an anaerobic condition. Development of the blue color was inhibited in the absence of air but gradually developed when the reaction vessel was opened to air. Thus, the coupling reaction is an oxidation–reduction (redox) reaction that requires molecular oxygen (O2) dissolved from the air to act as an oxidant. This finding corroborates statements in previous reports and will hopefully facilitate the use of the kit for forensic purposes.

Simple cloud point microextraction based on indophenol dye formation for mesalazine determination in pharmaceutical and biological samples

An efficient, sensitive, and environmentally friendly technique for determining mesalazine concentrations in pure drug dosage forms and blood serum using room temperature cloud point microextraction (RT-MCPE) is proposed in this study. The procedure relies on the formation of a blue indophenol dye in an alkaline medium that occurs due to an oxidative coupling reaction between mesalazine and syringic acid. The resultant dye can shift from blue to pink by forming an ion-pair complex with the acetate buffer (pH 3) used. To separate the dye from the surrounding aqueous environment, sodium sulfate (Na2SO4) and a nonionic surfactant, Triton X-114, were added to the solution, allowing the dye molecules to form micelles around the surfactant at room temperature. After using NaOH to restore the blue colour of indophenol, the solution was diluted and its absorbance at 635 nm was measured using a visible spectrophotometer, with all the experimental parameters optimised. The calibration curve exhibited linearity in the range of 0.25–10 μg mL−1 mesalazine, with a limit of detection of 0.04 μg mL−1. The method allowed for the accurate determination of the mesalazine content in drug dosage forms and serum, with an average recovery rate of 99.2% and a preconcentration factor of approximately 20. It yielded comparable results to traditional HPLC measurements, suggesting that it can serve as a reliable alternative or supplementary method for mesalazine determination.

Biodegradation of paraffin wax using Bacillus sp. SASH for quality improvement of crude oil properties

Biodegradation has become the most preferred and sustainable mean of reducing paraffin wax, removing paraffin deposition in pipelines and improving the flow of petroleum products. The current study focuses on the isolation of bacteria that has the capability to utilize paraffin as a sole carbon source and has been screened using 2,6-dichlorophenol indophenol (DCPIP) dye as redox indicator. The bacterium was identified as Bacillus sp. SASH according to its 16S rRNA gene sequence analysis. It is a moderate halophile that can grow in seawater at pH 7 and 37 °C. Bacillus sp. SASH was able to degrade various paraffinic products such as paraffin wax, heavy wax distillates, and liquid paraffin and it showed up to 84% paraffin wax degradation. Gas chromatography–mass spectrometry analysis revealed that higher carbon chains after retention time of 18 min were removed after treatment of the wax with the bacterium. Bacillus sp. SASH enhanced the flow of different petroleum products by reducing their viscosity and pour point values. It was also able to reduce the viscosity and improve the flow of crude oil by 60%.

Optical System Based on Nafion Membrane for the Detection of Ammonia in Blood Serum Samples

The blood ammonia (NH3) level is one of the most important hepatic biomarkers for the diagnosis and monitoring of liver pathologies and infections. In this work, we developed an optimized optical biosensing method to extract and quantify the ammonia contained in complex-matrix samples emulating the blood serum. First, the approach was tested with solutions of phosphate-buffered saline (PBS) and ammonia chloride. Then, further trials were carried out with solutions of fetal bovine serum (FBS). The ammonia was extracted from the tested samples through a customized cell, and it was optically quantified by exploiting the indophenol reaction. The extraction cell included a cation-exchange membrane in Nafion, which was chemically pre-treated through cleaning procedures of sulfuric acid and hydrogen peroxide to keep a basic pH in the ammonia solution and to avoid contaminants in the membrane. From the NH3 solution, the indophenol reaction produced light-reactive indophenol dye molecules, which were used as colorimetric indicators. Through absorbance measurements of the indophenol dye solution at 670 nm wavelength, we were able to detect and quantify the ammonia level in the samples both with a spectrophotometer and a customized miniaturized read-out system, obtaining a detection limit of 0.029 µmol/mL.

Indophenol and related dyes

Abstract This article covers three closely related types of colorant: the indophenol class of dyes plus those of their indaniline and indamine counterparts. Their roots stretch all the way back to the mid-nineteenth-century period during which synthetic dyes were successfully commercialized for the first time. The early history and subsequent development of these classes are briefly surveyed along with their chemistry. Two of their most important applications involve the synthesis of the dyes as part of the coloration process: the development of images from photographic film and the dyeing of hair. This introduction to indo dyes closes by describing their role in these and other coloration processes.

Oxidative Coupling-Base Reaction for the Indirect Spectrophotometric Determination of Paracetamol in Drug Formulations

A simple, rapid, and specific spectrophotometric method was developed for the determination of paracetamol in pure form and drug formulations. The method depended on the hydrolysis of paracetamol to p-aminophenol, which, oxidized under the effect of dissolved oxygen to benzoquinoneimine. In the alkaline medium, benzoquinoneimine reacts with Methyldopa to produce a high stabile indophenol dye. The absorbance was measured at 580 nm, and the molar absorptivity was found to be 7.75 x 10-5 L/(mol cm). Paracetamol was determined in pharmaceutical products in the 10–100 μg.mL-1 concentration range with a detection limit of 1.5 μg.mL-1 PAP. The developed method can be applied to the determination of both paracetamol and p-aminophenol in the presence of each other without prior separation. The proposed method is successfully employed for the determination of paracetamol in various synthetic mixtures and pharmaceutical preparations. Our obtained results were statistically compared with those given by the similar methods and the procedures evaluated as regards to both figures of merit and ease of applicability.

Physiochemical and molecular features of the necrotic lesion in the Heterobasidion-Norway spruce pathosystem.

In the forest of Northern Hemisphere, the fungi Heterobasidion annosum (Fr.) Bref. s.l. causes severe root and stem rot diseases, dramatically reducing the wood quality of conifer trees. The hallmark of the host response during the infection process is the formation of necrotic lesions and reaction zones. To characterize physiochemical and molecular features of the necrotic lesion, we conducted artificial inoculations on Norway spruce plants at different developmental stages: seedlings, young and mature trees. The results were further compared against data available on the formation of reaction zones. Strong necrosis browning or enlarged necrotic lesions were observed in infected tissues. This was accompanied by elevated pH. However, the increased pH, around 6.0 in necrotic lesions, was not as high as that documented in reaction zones, above 7.0 as marked by the intensity of the blue colour in response to 2,6-dichlorophenol indophenol dye. Peroxidase activity increased in infected plants and RNA-seq analysis of necrotic lesions showed marked upregulation of defence-related genes. Our findings highlight similarities and differences between the reaction zone and necrotic lesion formation in response of conifer trees to biotic stress.

Spectrophotometric Assay of Mesalazine in Pharmaceutical Preparations Via Oxidative coupling reaction with o-cresol and sodium metaperiodate

A simple, straightforward, rapid, sensitive and an accurate UV-VIS spectrophotometric method was suggested for the determination of mesalazine in bulk sample and in dosage forms. The method is relying on the oxidation of mesalazine by sodium metaperiodate followed by coupling with o-cresol in alkaline medium to form a blue indophenol dye which absorbs at 645 nm. Beer's law is obeyed in the concentration range 0.4- 12 µg/ml of the drug with good accuracy (average recovery) 101.38% and precision (RSD) is less than 3.5%. The molar absorptivity is 22435 l.mol-1.cm-1 with detection limit 0.101 µg/ml and 0.338 µg/ml as quantification limit. The recommended method is effectively applied to the determination of mesalazine in pharmaceutical dosages (tablets and capsule). The analytical results were well-matched with the standard method British pharmacopeia) and validated good accuracy and precision.

Impact of Composting on Growth, Vitamin C and Calcium Content of Capsicum chinense

The nutritional quality of the food has become a serious concern in existing agricultural system as the present world aims to enhance only the food production. A field experiment was carried out to study the effect of different fertilizers on growth, vitamin C and calcium content in yield of Capsicum chinense at Regional Agricultural Research and Development Center, Makandura consisting four treatments as without fertilizer (control/ T1), only compost (T2), compost + inorganic fertilizer (T3) and only inorganic fertilizer (T4) with a randomized complete block design (RCBD) replicating four times. Vitamin C content was measured by Indophenol dye redox titration method and calcium content was analyzed by atomic absorption spectrophotometer. Data was analyzed using analysis of variance. The highest growth was recorded in T3 and no significant differences between treatments in growth parameters at 50% flowering stage.The Vitamin C content was highest in treatment with only compost (T2) and the lowest in treatment compost + inorganic fertilizer (T3). The results indicated that yield from organically managed crops contain significantly higher amount of vitamin C (9.24±2.27 mg/100g, p= 0.0274). The highest calcium content was found in T1 (control) (1.1±0.05 %) and a significant difference (p= 0.0296) was observed between T1 (control) and T3 (calcium=0.75±0.12 %). Compost alone can be used to produce food with high amount of vitamin C. Use of inorganic fertilizer alone or integration of compost with inorganic fertilizer was less effective in producing high quality nutritious foods.

Selective colorimetric detection of dissolved ammonia in water via modified Berthelot’s reaction on porous paper

Continuous monitoring and rapid on-site determination of toxic ammonia in various aqueous systems are important for maintaining water quality and preserving the environment. Though several methods such as flow-based spectrophotometry are currently utilized for this purpose, there is still need for more selective ammonia determination. We present a new detection route for quantifying NH3 in water samples by means of the evaporation of dissolved ammonia into headspace, followed by selective detection using a colorimetric sensor. Gaseous NH3 detection is attained by the selective formation of blue indophenol dye through modified Berthelot’s reaction on porous paper. To optimize the sensing layer in terms of uniform and intense coloration, the water-soluble powder reagents were homogeneously dispersed in nonpolar cyclohexane and then deposited by a vacuum-assisted filtration on the paper substrate. The formation of indophenol blue was activated under highly humidified conditions through selective chemical reactions between solid-state Berthelot’s reagents and NH3. The colorimetric response of the low-cost paper sensors was saturated within 10min, and color change was observed by the naked eye for an ammonia solution of 10mg/L. Furthermore, the response magnitude was not affected by addition of 0.1wt% polar organic solvents (ethanol, acetone, dimethylformamide or acetic acid) or inorganic salts (NaCl, KCl, MgSO4 or CaSO4), suggesting a good detection cross-selectivity.

AN IMPROVED MICROMETHOD FOR THE DETERMINATION OF ACETAMINOPHEN IN PLASMA BY VISIBLE SPECTROPHOTOMETRY: APPLICATION TO A PHARMACOKINETIC STUDY IN RABBITS

Objective: To report a simple and economic alternative spectrophotometric micro-method for the determination of acetaminophen using 200 µl of plasma sample.Methods: The analyses were based on a simple colorimetric test in which p-aminophenol, after an acidic hydrolysis step, is reacted with phenol in an alkaline medium to form an indophenol dye which exhibits a maximum extintion at 625 nm. The micro method was validated according to the international criteria, and then it was used for the quantification of plasma levels of acetaminophen after rectal administration of 100 mg of the drug to male New Zealand rabbits.Results: The analytical recovery was 100.97%, with solutions of 5−25 µg/ml (plasma/water). The linearity with plasma solutions was good (R2 = 0.995), at the same concentration levels. The within-run and between-run precision, as well as accuracy expressed as coefficient of variation, were less than 8%. The mean accuracy was 102.24%. The stability was proved for a one-week period at −20 °C. The pharmacokinetic parameters were computed by non-linear regression analysis. The non-compartment model analysis was used to fit the in vivo data.Conclusion: The validation parameters were within acceptable limits for clinical studies. The analysis was adequate for the determination of acetaminophen in small plasma samples, and it can be easily adapted by any hospital or clinical laboratory with non-special equipment.

Study on the role of Nocardia farcinica in enhancing the flow rate of crude oil

ABSTRACTMicrobial degradation of paraffin wax is an efficient method of removing wax deposition from pipelines and enhancing the flow rate of crude oil. The present study was carried out to isolate a potential paraffin-degrading organism from oil wells of Gujarat. Screening for bacteria-utilizing paraffin wax as the sole source of carbon was carried out using 2,6-dichlorophenol indophenol (DCPIP) dye as redox indicator. The selected organism was identified as Nocardia farcinica by 16S rRNA sequencing. Nocardia farcinica showed 100% degradation of heneicosane, 65.99% degradation of docosane, and 50.59% degradation of tricosane, the major components of paraffin wax, in 8 days, which was observed by gas chromatography. Eicosane (86%) and heneicosane (80%) were utilized more by the selected organism compared with octacosane (61%) and triacontane (58%) (DCPIP dye method). Gas chromatographic analysis revealed that the selected organism degraded 50% of paraffin crude oil in 10 days. To determine the ability of the selected organism to enhance flow rate, parameters such as viscosity (cps), surface tension (d/cm2), pour point (°C), and flow rate (min/2 ml) were determined, and the result showed significant reduction in all the parameters after the addition of Nocardia farcinica. The viscosity and surface tension of crude oil were reduced by 22 and 6.30 points, respectively, after the addition of Nocardia farcinica. Pour point and flow rate were reduced by 2 and 11 points, respectively, when compared with control. The above findings indicate that Nocardia farcinica isolated from crude oil plays a major role in enhancing the flow rate of crude oil.

Extraction of ammonia and nitrite using modified magnetite iron oxide nanoparticles before spectrophotometric determination in different water samples

A new analytical approach was developed for the extraction and determination of ammonia and nitrite in environmental water samples involving magnetic solid-phase extraction (MSPE) with magnetite nanoparticles (MNPs) as the adsorbent. The procedure is based on the derivatisation of ammonia based on Berthelot reaction. The obtained indophenol dye was extracted using MSPE and determined spectrophotometrically at 655 ± 3 nm. Nitrite ion is determined after its reduction to ammonia in the presence of Zn/HCl. The main factors that affected the extraction efficiency were studied and optimised. The method gave calibration curves for ammonia with good linearity in the range 10–550 µg L−1, and correlation coefficients (r) higher than 0.99. The detection and quantification limit was found to be 3.1 and 10.2 µg L−1, respectively. The method showed good precision and accuracy, with intra- and inter-assay precisions of less than 6.6% at all concentrations. The recoveries ranged 89–105% and 88–105%, for ammonia and nitrite determination, respectively. The method was applied to the determination of the target analytes in real samples.

New insights into dye chemistry and physics

A review of the academic dye research performed by the Port Sunlight group and its coworkers over the past 15 years is presented. The work is focused on three areas: (1) substrate structure; (2) dye interactions in aqueous solution and on substrates; (3) dye degradation and products. For substrates, a detailed model of the nanoenvironment experienced by chemicals within cellulose fibre is given, showing the different environments and remarkable mobility of absorbed chemicals. Advanced nuclear magnetic resonance diffusion measurements provide the complex pathways by which compounds find their way in and out of the fibre. For dye interaction, detailed theoretical and experimental studies are reported on three model dye systems, the anionic monoazo dye Orange II, the bisazo anionic dye CI Direct Blue 1, and cationic monoazo thiazolium dyes, providing a comprehensive picture of their structure. A quantitative mechanism of dye binding to cellulose is shown. Resonance Raman provides an effective forensic tool for dye identification, even from single fibres. The products and kinetics of Orange II dye degradation by one‐electron reduction in aqueous solution is given, with the identification of an indophenol dye end‐product. In cellulosic materials the reduction mechanism is similar to solution, when the higher microviscosity is accounted for. Hydrolysis of thiazolium dyes occurs at both aromatic rings of the dye but on different timescales. Measurement and calculations of the electronic structures of one‐electron‐reduced and ‐oxidised dyes are presented. The mechanism of photooxidation by sunlight of azo dyes in cotton is delineated.

Novel chromogenic aminopeptidase substrates for the detection and identification of clinically important microorganisms

A series of amino acid derivatives 8–10, 42 and 43 have been prepared as chromogenic enzyme substrates in order to detect aminopeptidase activity in clinically important Gram-negative and Gram-positive bacteria. Enzymatic hydrolysis liberates the amino acid moiety and either a 4-aminophenol or a 4-dialkylaminoaniline derivative which undergoes oxidative coupling with 1-naphthol or a substituted 1-naphthol giving an indophenol dye. Substrates and 1-naphthols were incorporated into an agar-based culture medium and this allowed growth of intensely coloured bacterial colonies based on hydrolysis by specific enzymes. Red/pink coloured colonies were produced by the substrates 8–10 and blue coloured colonies were formed by the substrates 42 and 43. The l-alanyl aminopeptidase substrates 8 targeted l-alanyl aminopeptidase activity and gave coloured colonies with a range of Gram-negative bacteria. Substrates 9 targeted β-alanyl aminopeptidase activity and generated coloured colonies with selected Gram-negative species including Pseudomonas aeruginosa. Three substrates for l-pyroglutamyl acid aminopeptidase (10a, 10c and 43) were hydrolysed by enterococci and Streptococcus pyogenes to generate coloured colonies. Two yeasts were also included in the study, but they did not produce coloured colonies with any of the substrates examined.

Selective Determination of Catechin among Phenolic Antioxidants with the Use of a Novel Optical Fiber Reflectance Sensor Based on Indophenol Dye Formation on Nano-sized TiO2

The optical sensor for "tea catechins" was built by immobilizing 2,2'-(1,4-phenylenedivinylene)bis-8-hydroxyquinoline (PBHQ) on TiO₂ nanoparticles (NPs). The sensor worked by "indophenol blue" dye formation on PBHQ-immobilized TiO₂ NPs as a result of p-aminophenol (PAP) autoxidation with dissolved O₂ at pH 10. Among quercetin, rutin, naringenin, naringin, gallic acid, caffeic acid, ferulic acid, p-coumaric acid, catechin, epicatechin, epicatechin gallate, epigallocatechin, epigallocatechin gallate, and trolox, only catechin group antioxidants delayed the color formation on NPs, as measured by the reflectance signal at 710 nm. For quantitative analysis, reflectance signal versus time was recorded, and the difference between the areas under curve (ΔAUC) in the presence and absence of catechin was correlated (r = 0.98) to catechin concentration. The selectivity of the sensor for catechins was shown in tea infusions compared to other plant extracts and was ascribed to the nonplanar structure of catechin interfering with the formation of perfectly conjugated indophenol blue on TiO₂ surface.

Reductive Reaction Mechanisms of the Azo Dye Orange II in Aqueous Solution and in Cellulose: From Radical Intermediates to Products

Reductive reaction mechanisms of the azo dye Orange II (Acid Orange 7) in aqueous solution have been studied from radical intermediates through to the final products using a combination of nanosecond time-resolved UV-visible absorption spectroscopy, steady-state photolysis, and HPLC techniques. The dye is reduced by photochemically produced 2-hydroxy-2-propyl radicals at a near-diffusion-controlled rate (k2 = 2.2 x 10(9) dm3 mol(-1) s(-1)) to give the dye radical anion, which then disproportionates (k3 = 2.6 x 10(8) dm3 mol(-1) s(-1)) to re-form the parent dye and a hydrazine. The hydrazine decomposes to 4-aminobenzenesulfonate and a naphthylimine species, which hydrolyses to give 1,2-naphthoquinone; this naphthoquinone and 4-aminobenzenesulfonate react to give a species that reacts further in the presence of air to form an indophenol dye. The reduction of Orange II has also been studied in cellophane, where the rate constant for dye reduction by 2-hydroxy-2-propyl radicals is approximately two orders of magnitude lower than that in aqueous solution.

An optical fibre reflectance sensor for p-aminophenol determination based on tetrahydroxycalix[4]arene as sensing reagent

A fibre-optic sensor for p-aminophenol (PAP) based on the use of 25,26,27,28-tetrahydroxycalix[4]arene (CAL4) immobilised onto Amberlite XAD-16 and reflectance spectrometry has been developed. The sensor is based on the reaction of PAP with CAL4 in presence of an oxidant to produce an indophenol dye. The reflectance measurements were carried out at a wavelength of 620 nm since it yielded the largest divergence different in reflectance spectra before and after reaction with the analyte. A highly linear calibration curve ( r 2 = 0.992) was observed in the PAP concentration range of 0.5–35 ppm (linear within 0.5–5.5 ppm) with a calculated limit of detection (LOD), defined as the lowest concentration level of analyte that the proposed method can detect to be statistically different from an analytical blank (i.e., yielding an analytical response greater than three times the standard deviation of a blank), of 0.109 ppm. The sensor response from different probes ( n = 5) gave an RSD of 1.8% at 10.9 ppm PAP concentration. The response time of the optical one-shot sensor was 5 min for a stirred solution. The intra- and inter-assay variability (as relative standard deviation: RSD) was approximately 2 and 4%, respectively. The lifetime of the blank sensor (CAL4 adsorbed onto XAD-16) was at the order of weeks–months when protected from light, while of the analyte sensor (XAD-16 + CAL4, to which the oxidation product of PAP is coupled) was at the order of days when protected from air and light. Using the optical sensing probe, PAP in urine, pharmaceutical and pharmaceutical wastewater was determined. Although aminophenols showed serious interference, the method was not affected from common ions and from various important drug active constituents present in urine and pharmaceutical effluents such as acetaminophen, acetylsalicylic acid, sorbitol, and caffeine. The proposed technique was tested by replicate analysis of several complex samples with spiked PAP, with recoveries ranging between 97 and 102%.