Nitrazine Yellow Research Articles

Portable Photoacoustic Analytical System Combined with Wearable Hydrogel Patch for pH Monitoring in Chronic Wounds.

Timely diagnosis, monitoring, and management of chronic wounds play crucial roles in improving patients' quality of life, but clinical evaluation of chronic wounds is still ambiguous and relies heavily on the experience of clinician, resulting in increased social and financial burden and delay of optimal treatment. During the different stages of the healing process, specific and dynamic changes of pH values in the wound exudate can be used as biomarkers to reflect the wound status. Herein, a pH-responsive agent with well-behaved photoacoustic (PA) properties, nitrazine yellow (NY), was incorporated in poly(vinyl alcohol)/sucrose (PVA/Suc) hydrogel to construct a wearable pH-sensing patch (PVA/Suc/NY hydrogel) for monitoring of pH values during chronic wound healing. According to Rosencwaig-Gersho theory and the combination of 3D printing technology, the PA chamber volume and chopping frequency were systematically optimized to improve the sensitivity of the PA analytical system. The prepared PVA/Suc/NY hydrogel patch had excellent mechanical properties and flexibility and could maintain conformal contact with skin. Moreover, combined with the miniaturized PA analytical device, it had the potential to detect pH values (5.0-9.0) free from the color interference of blood and therapeutic drugs, which provides a valuable strategy for wound pH value monitoring by PA quantitation. This strategy of combining the wearable hydrogel patch with portable PA analysis offers broad new prospects for the treatment and management of chronic wounds due to its features of simple operation, time savings, and anti-interference.

Microfluidic paper-based analytical device for the speciation of inorganic nitrogen species

A microfluidic paper-based analytical device (μPAD) utilizing gas-diffusion separation and solid-phase reduction was developed for the first time for the determination of both ammonium and nitrate, which are the dominant inorganic nitrogen species in environmental waters. The device consists of 3 filter paper layers accommodating the sample, reagent and detection zones. The reagent zone is separated from the detection zone by a semipermeable hydrophobic membrane and acts as a solid-phase reactor where nitrate is reduced to ammonia by Devarda's alloy microparticles, integrated into a μPAD for the first time. The detection zone incorporates the acid-base indicators bromothymol blue (BTB) or nitrazine yellow (NY) and changes colour in two steps. Initially the colour change is caused by ammonia generated by the reaction of ammonium and sodium hydroxide in the sample zone. This colour change is followed by a subsequent colour change as a result of the ammonia produced by the reduction of nitrate by the Devarda's alloy microparticles. The corresponding reflectance value changes are used for the quantification of the two inorganic nitrogen species in the ranges 6.5–100.0 or 2.1–15.0 mg N L−1 for ammonium and 18.2–100.0 or 4.2–15.0 mg N L−1 for nitrate when BTB or NY are used, respectively. Under optimal conditions the limits of quantification of ammonium and nitrate in the case of BTB were determined as 6.5 and 18.2 mg N L−1, respectively, while the corresponding values in the case of NY were found to be 2.1 and 4.2 mg N L−1. The newly developed μPAD was stable for 62 days when stored in a freezer and 1 day at ambient temperature. It was validated with a certified reference material and successfully applied to the determination of ammonium and nitrate in spiked environmental water samples and soil extracts.

Behavior of Sulfonephthalein and Azo dyes as effective pH sensors in hybrid materials

The behavior of pH indicators belonging to two different families, Sulfonephthalein and Azo in the Organically modified silicates (OrMoSil) polymer matrix, was investigated. The fraction and the dimension of the OrMoSil organic moiety were co-modulated with the cationic surfactant Hexadecyltrimethylammonium p-toluenesulfonate concentration. Two matrices were tested: the former based on Tetraethyl orthosilicate/ Trimethoxyphenylsilane (TEOS/FTMS), the latter, more lipophilic, based on TEOS/Dodecyl-TEOS. The working interval of Bromothymol Blue (BB) and Nitrazine Yellow (NY), with the co-variation of cationic surfactant amount, C, was wider for the matrix based on TEOS/Dodecyl-TEOS. The overall working interval of BB was between pH 5.80 and 12.50 and between 6.00 and 11.30 for NY. Among the pH indicators characterized by transitions between non-complementary colors, the most important results could be achieved with Methyl Red (MR). With the addition of Tetrabromophenol Blue (TBB), the sensitivity gradually rises with a linear hue profile between pH = 4.20 and pH = 11.90 with a small amount of dye for only one spot. In correspondence of the molar ratio nTBB/nMR = 0.233, there is the inversion point characterizing a spot working as an “on-off” sensor centered at pH = 4.15 suitable for pH measurement of acidic soils.

Kinetic response of pH colorimetric sensors: Role of the cationic surfactant concentration and amount and type of solvent used in the preparation of the sensing spot

A pH colorimetric sensor array (CSA) with a kinetic response comparable to those of the pH-meter was prepared. The signal comes from the Hue coordinate (H) and RGB profiles of some pH indicators such as Bromothymol Blue (BB) and Nitrazine Yellow (NY) in polyvinylidene fluoride (PVDF)-supported organically modified silicate (OrMoSil) spots. The t95 is of the order of 50–150 s for RGB coordinates but is lowered of one order of magnitude employing the H coordinate as the detection signal. The addition of the Hexadecyltrimethylammonium p-toluenesulfonate (CTApTs) additive in the interval 0.10 < R < 0.15 gCTApTs/gprecursors, determined the minimum time to reach the basic and the acidic plateau (t95b and t95a) for both the indicators (BB: 5 and 32 s; NY: 2 and 7 s). At concentration ratio, R > 0.19 gCTApTs/gprecursors, the transition from the basic to the acid form was hindered by the cationic interface due to the surfactant. The CTApTs concentrations, leading to a t95 lower than one minute, were in the interval 0.10 < R < 0.37 gCTApTs/gprecursors for NY and 0.10 < R < 0.28 gCTApTs/gprecursors for BB, comparable to the response time of the potentiometric measurements. Indeed, the kinetic profiles did not change with the amount and type of solvent.

Surface Functionalization of Cotton Fabrics by Photo-Grafting for pH Sensing Applications

This paper investigates the photo-grafting of a halochromic molecule on cotton fabric surfaces. Nitrazine yellow (NY) dye was modified with a methacrylate moiety (GMA) obtaining a photo-reactive dye (GMA-NY), which was covalently grafted onto the cellulosic substrate by means of UV irradiation. The photo-grafting reaction was studied by FT-IR spectroscopy, while the pH response of the functionalized fabric was evaluated at different pH conditions (i.e., acidic and alkaline conditions) both in wet and vapor environments by spectrophotometric analyses. The results showed that the photo- grafting of the modified dye onto the fabric was successful: treated cotton clearly changed color when subjected to different pH. It was thus demonstrated that the GMA- NY dye, photo-grafted on cotton, can successfully impart pH sensing properties to the fabric, which can therefore find numerous applications in the area of smart textiles.

Development of a micro-distillation microfluidic paper-based analytical device as a screening tool for total ammonia monitoring in freshwaters

An easy-to-use, portable 3D microfluidic paper-based analytical device (μPAD) for the determination of total ammonia (i.e., ammonia + ammonium) in freshwaters is described. It consists of two layers of paper patterned with hydrophilic circular zones, one impregnated with sodium hydroxide (sample zone) and another (detection zone) with an acid-base indicator (nitrazine yellow (NY) or bromothymol blue (BTB)), separated by a μ-distillation chamber. Ammonium ions present in the water sample are converted into ammonia gas by reaction with sodium hydroxide in the sample zone. Ammonia then diffuses through a headspace and reacts with an acid-base indicator in the detection zone, the reflectance of which can be related to the total ammonia concentration. The analytical signal at 7.8 mg L−1 offered by the μ-distillation chamber-based μPAD is more than double of that obtained using a gas-permeable membrane.The proposed μPAD is characterised by a limit of detection of 0.32 or 0.47 mg N L-1 and working concentration ranges of 0.5–3.0 mg N L-1 or 2.0–10 mg N L-1 when using NY or BTB indicators, respectively. This is the first μPAD whose working range covers almost the entire trigger value range (0.32–2.3 mg N L-1) for ammonia nitrogen in freshwater systems which makes it suitable as a field screening tool for ammonia in freshwaters. An inter- and intra-device repeatability of 7.6% and 9.0%, respectively, has been achieved for the NY-based μPAD (3 mg N L-1) and 13 and 2.5% (8 mg N L-1) for the BTB-based μPAD. The NY-based μPAD is stable under vacuum for at least 12 days at room temperature, and 56 days if stored in a freezer (≤−20 °C).

Synergistic removal of Cu(II) and nitrazine yellow dye using an eco‐friendly chitosan‐montmorillonite hydrogel: Optimization by response surface methodology

ABSTRACTA comprehensive feasibility study on adsorption of Cu(II) and a water‐soluble nitrazine yellow (NY) dye by chitosan‐montmorillonite (CS‐MMT) hydrogel as the biosorbent was investigated as a function of biosorbent dosage, initial concentration, pH, temperature, and the presence of salts. Box–Behnken methodology was applied to optimize the adsorption experiments. Maximum adsorption values were determined as 132.74 mg/g and 144.41 mg/g at pH = 5.0, for Cu(II) and NY dye, respectively. Equilibrium isotherms of Langmuir and Freundlich were analyzed by the non‐linear regression model. The equilibrium data were well described by Freundlich model and the adsorption process well fitted pseudo‐second order kinetics. The enthalpy change of adsorption (ΔH°) were calculated as −3.78 kJ/mol and −5.75 kJ/mol for Cu(II) and NY dye, respectively, indicating that the adsorption processes were exothermic. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43664.

Characterization of nitrazine yellow as a photoacoustically active pH reporter molecule.

Throughout the fields of biomedical imaging, materials analysis, and routine chemical analysis, it is desirable to have a toolkit of molecules that can allow noninvasive/remote chemical sensing with minimal sample preparation. Here, we describe the photophysical properties involved in photoacoustic (PA) measurements and present a detailed analysis of the requirements and complications involved in PA sensing. We report the use of nitrazine yellow (NY) as a well-behaved PA pH reporter molecule. Both the basic and acidic forms of NY are photoacoustically well-behaved and allow for rapid and noninvasive measurement of pH in either transparent or turbid media. We also find that the serum protein-bound form of NY is photoacoustically well-behaved and should permit applications in noninvasive 3D imaging (e.g., the lymphatic system).

Influence of catalyst in the synthesis of a cellulose-based sensor: Kinetic study of 3-glycidoxypropyltrimethoxysilane epoxy ring opening by Lewis acid

Hybrid halochromic sensor coatings were realized immobilizing Nitrazine Yellow (NY) onto cotton fabrics via the epoxy group of 3-glycidoxypropyltrimethoxysilane (GPTMS) silica precursor in acidic condition. Boron trifluoride diethyl etherate (BF3OEt2) in a various percentage range (1–10%, w/w GPTMS) has been used to catalyze the epoxide ring opening. In order to optimize the system, an FTIR study has been developed and kinetic data were obtained for the epoxy ring opening process. A linear correlation between the obtained kinetic rates and BF3 percentage was observed. By nuclear magnetic resonance (NMR) analysis in solution the real structure of NY, derived from an attack of diazonium salt to para hydroxyl position, was confirmed and the final product of the reaction between NY and GPTMS was characterized. Finally, the different amounts of catalyst were found to affect the coatings wash fastness and the halochromic response of the cellulose-based sensors.

Application of Glassy Carbon Electrode Modified with a Bilayer of Multiwalled Carbon Nanotube and Polypyrrole Doped with Nitrazine Yellow for Voltammetric Determination of Naltrexone

AbstractA new sensitive electrochemical sensor was fabricated based on a layer by layer process. In this process the glassy carbon electrode (GCE) is first coated by a thin film of multiwalled carbon nanotubes (MWCNTs). In the next step, the electropolymerization of pyrrole in the presence of Nitrazine Yellow (NY) as a dopant anion is performed on the surface of the MWCNTs precoated electrode. The electrochemical response characteristics of the modified electrode toward naltrexone (NTX) were studied by means of linear sweep voltammetry (LSV). A remarkable increase (∼19 times) was observed in the anodic peak current of NTX on the surface of the modified electrode relative to the bare GCE. The effects of experimental parameters on the electrode response such as, drop size of the cast MWCNTs suspension, pH of the supporting electrolyte, accumulation conditions and the number of cycles in the electropolymerization process were investigated. Under the optimum conditions, the modified electrode showed a wide linear response to the concentration of NTX in the range of 4.0×10−8–1×10−5 mol L−1 with a detection limit of 12 nmol L−1. The prepared sensor exhibited high sensitivity, stability and good reproducibility for the determination of NTX. This sensor was successfully applied for the accurate determination of trace amounts of NTX in pharmaceutical and clinical preparations.

Color transitional dyes as indicators of ionic boundaries in sodium dodecylsulfate polyacrylamide gel electrophoresis.

Several dyes were evaluated for their potential use as indices of ionic boundaries and pH discontinuities during polyacrylamide gel electrophoresis (PAGE). Dye selection was based largely upon color transition over the pH intervals present in the commonly used Tris-HCl-glycine buffer systems. In the absence of sodium dodecylsulfate (SDS) nitrazine yellow, cresol purple, cresol red, and phenol red had relative mobilities (relative to the chloride boundary; RC1) of 1.00 at 20% polyacrylamide concentration (% T) compared to bromophenol blue (BPB) for which RC1=0.77. The homologue of BPB, 3, 4, 5, 6-tetrabromophenolsulfonephthalein (TBPS), exhibited a useful color transition over the pH 6.6-8.2 range but was an equally poor indicator of the chloride boundary at 20% T in the absence of SDS (RC1=0.73). The RC1 of other dyes was increased in the presence of SDS, particularly the cationic dye neutral red which complexes with micellar but not monomeric SDS. In the presence of SDS, all dyes except neutral red exhibited RC1 of 1.00 at 15% T, whereas only neutral red and nitrazine yellow had RC1 values of 1.00 at lower gel concentrations. Partial characterization of SDS, in terms of RC1 and zone broadening, was performed in a system devoid of extraneous SDS in the gel or electrolytes.

The sodium hydroxide erosion assay: a revision of the alkali resistance test.

Burckhardt proposed the alkali resistance method as a means of assessing the integrity of the stratum corneum barrier in 1947. Researchers after Burckhardt largely found the test unreliable and nonreproducible; it therefore fell into disuse worldwide. We have upgraded the procedure by exposing the skin to 1.0 M sodium hydroxide under strictly specified conditions for successive 1-min periods until the emergence of the first erosions, revealed by staining with nitrazine yellow. Histology showed that the erosions were follicular and limited to the epidermis. The test was highly reproducible and repeatable. We demonstrated the usefulness of the test in the following ways: (1) the erosion time increased with aging, correlating with a thickened horny layer; (2) as few as five Scotch tape strippings greatly decreased the erosion time, although transepidermal water loss was only slightly increased; (3) slight damage to the horny layer by a 24-h exposure to 0.01% sodium lauryl sulfate sharply reduced the erosion time; (4) the erosion time decreased after daily open applications for 3 weeks of clobetasol propionate, corresponding to the thinned horny layer; (5) daily applications of petrolatum increased the erosion time. This new version of the alkali resistance test, renamed the sodium hydroxide erosion assay, promises to be a useful tool for studying the horny layer barrier in healthy and diseased skin.

Improved Competitive Indicator Methods for the Study of ɑ-Cyclodextrin Complexes

The competitive indicator method for studying molecular complexes is extended to systems forming 1:1 (SL) and 1:2 (SL2) complexes of substrate (S) and ligand (L). A modification is described for slightly soluble substrates, in which the presence of solid substrate establishes a constant concentration of uncomplexed substrate. These methods are applied to complexes of α-cyclodextrin with some aromatic substrates, with methyl orange as the indicator in acid solution; nitrazine yellow is introduced as an indicator for these studies in basic solution.

Nitrazine yellow: A new indicator

Nitrazine yellow: A new indicator