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Three azo dyes compounds based on chromotropic acid have been synthesized and their chemical structures confirmed by spectra tools (FTIR and 1H-NMR). Their corrosion inhibition effect has been studied on carbon steel corrosion in 0.5 M sulfuric acid solution using potentiodynamic polarization and weight loss techniques. The findings have shown that the azo dyes tested are effective inhibitors of corrosion. With increased concentration, the inhibition effectiveness of all the azo dyes studied rises. Surface morphology has been studied. Also, the azo compounds inhibitors were investigated using density functional theory (DFT). The calculated quantum chemical parameters were calculated. The theoretical results are consistent with the experimental data reported.

The determination of the ozone concentration in the atmosphere is an urgent need but most current methods are limited by large-scale equipment or complex procedures. Herein, a gas–liquid chemiluminescence (GL-CL) assay based on a portable GL-CL detector platform was reported for the fast and sensitive online determination of ozone. Graphene quantum dots (GQDs) and Triton X-100 were employed to synergistically enhance the CL intensity of chromotropic acid (CA)–ozone. The increase was about seven-fold upon the addition of GQDs and Triton X-100. The potential enhancement mechanism was also investigated. The speculated CL enhancement mechanism was that GQDs could catalyze dissolved oxygen in the CA solution to produce more free radicals in the presence of UV-light, and these radicals converted CA into more active compounds that could react with ozone and emit photons. The free radicals, active compounds and luminophores were protected from water quenching by micelles produced by dissolving Triton X-100 in water and as a result, CL was markedly enhanced. Most importantly, the response time of the GL-CL detector platform towards ozone was less than 0.5 s. Based on this outcome, a GL-CL assay for detecting atmospheric ozone was successfully developed with a linear range from 0.1 to 150 ppbv and a detection limit of 0.02 ppbv. This work provides a rapid and sensitive method for the online measurement of ozone, and has great potential in environmental applications; the potential applications of GQDs and Triton X-100 in the field of GL-CL have also been highlighted.

Background Allergic contact dermatitis to tattoo ink may last from weeks to years. Formaldehyde is a strong sensitizer that may be present in predispersed tattoo inks. Objectives The aim of this study was to evaluate the presence of formaldehyde in predispersed tattoo inks using the chromotropic acid method. Methods Tattoo inks from 39 companies were evaluated. Inclusion criteria included availability to purchase inks online through US tattoo product wholesalers or individual Web sites. Brands were grouped based on prevalence of use: common, uncommon, or rare. For common brands, 8 colors (primary colors, secondary colors, black, and white) were purchased. For uncommon and rare brands, 5 colors (primary colors, black, and white) were purchased. Each ink was tested with standard chromotropic acid method procedures; concentration of formaldehyde released was quantified using spectrophotometry. Results In total, 127 tattoo inks were purchased and tested. Ninety-three (73%) tested positive for formaldehyde release; 34 (27%) tested negative. Formaldehyde release did not correlate with color or brand. At least 1 ink from all brands (except 1) was positive for formaldehyde release. Conclusion Approximately three-quarters of selected US tattoo inks tested positive for formaldehyde release. Clinicians should be aware of tattoo ink as a potential source of formaldehyde.

A novel organic cocrystal salt hydrate (CTPTH) of Chromotropic acid with 1,10-phenanthroline was successfully obtained using both traditional solution method and liquid-assisted grinding method, a green approach. The formation and characterization were done by Powder x-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis, and the structural confirmation by single crystal x-ray diffraction. The molecular properties were studied using density functional theory, B3LYP/def2-SVP including dispersion correction (D3) to calculate the HOMO and LUMO energies using Orca and Gaussian packages. The calculated geometric parameters were in good agreement with those of experimentally observed. The non-bonding interaction between the CTPTH and active site of the crystal structure of quorum-quenching N-Acyl homoserine lactone lactonase (PDB: 2BR6) in bacterium was studied by molecular docking. The total energy of ligand interaction of CTPTH with the receptor is found to be − 42.78 kcal mol−1. The Hirshfeld surfaces were mapped over dnorm for the identification and quantification of robust synthons for a better understanding of the overall packing pattern of CTPTH. In addition, the antibiofilm efficacy of CTPTH against the pathogenic bacterium Pseudomonas aeruginosa was also determined.

A new type of symmetrical bis-crown ether is prepared by connecting dibenzo-18-crown-6 ether on both sides of the chromotropic acid, and then grafting the aforementioned bis-crown ether onto polyvinyl alcohol matrix to prepare a series of anion exchange membranes (AEMs), which their have high conductivity and strong alkali stability. These synthesized membranes were named B-CX%-P AEMs (x is the mass percentage of the symmetrical bis-crown ether (B–C)). Then, the chemical structure of aforementioned AEMs were verified by means of 1H NMR, FT-IR and UV. Meanwhile, the OH− conductivity, alkaline stability and single cell performance of the synthesized membrane were also investigated. The results revealed that the conductivity of B–C30%-P membrane is the highest at 80 °C (235 mS cm−1), and the power density is also the highest (197 mW cm−2), and the alkali stability of the membrane synthesized in this paper was also improved. The conductivity at 80 °C was only reduced by 4%, which was obtained by immersing the B–C30%-P membrane immersed in 6 mol L−1 KOH solution for 168 h, which the aforementioned results proved that the synthesized membrane in this research had excellent OH− conductivity and alkaline stability.

The electrospray ionisation mass spectrometric (ESI-MS) behaviour of various complexes of beryllium have been investigated in the work described in this paper. These beryllium complexes were analysed in situ on a small scale by preparing appropriate molar mixtures of the Be2+ ion with ligands in a range of solvent systems. In view of the toxicity of beryllium compounds, this combinatorial type screening, involving miniscule amounts of material in solution, proved to be a safe strategy to pursue the coordination chemistry of beryllium. A variety of beryllium complexes were generated with various ligands in solutions and subjected to detailed characterisation by ESI-MS. These ligands, containing functional groups or architecture of interest, varied from simple ligands such as the acetate ion to more common beryllium chelators including hydroxy keto ligands (maltol, tropolone), malonic acid, chromotropic acid and citric acid. Generally, there was excellent correlation between the species observed in the mass spectrum and those confirmed to exist in solution by other techniques. This lent strong credence to the ESI-MS methodology used as an efficient analytical technique for the easy screening of a diverse range of potential ligands for the divalent beryllium ion.

The interaction of pinanediol with 2-fluorophenylboronic acid and several other substituted phenylboronic acids was studied in 40% vol. aqueous acetonitrile by 1H and 11B NMR, potentiometric and spectrophotometric titrations at variable pH values. The experimental results reveal the formation of a very stable trigonal ester (Ktrig ≈ 2 × 104 M-1) and a significantly less stable tetrahedral hydroxocomplex (Ktet ≈ 5 × 103 M-1) in contrast to the traditionally observed inverted order of stabilities KtrigKtet. Comparison of the crystal structure of the trigonal ester isolated from aqueous acetonitrile with the DFT simulated structure of the respective hydroxocomplex shows that an unusual order of stabilities KtrigKtet is observed in spite of the existence of the usual strain release effect in the O-B-O angle considered responsible for the typically observed increased stability of the tetrahedral hydroxocomplex. A complementary study of the stability of the six-membered cyclic boronate esters of chromotropic acid demonstrated the order Ktrig ≪ Ktet although the strain was absent in these esters. The results for m-, p-substituted phenylboronic acids show that the stability of both five- and six-membered trigonal esters formed with pinanediol and chromotropic acid, respectively, is insensitive to electronic effects but the electron accepting substituents stabilize the hydroxocomplexes. It follows from the whole set of results that Ktet can be much larger than Ktrig in the absence of the strain, but with a sufficiently acidic diol, and that the presence of the strain does not necessarily make Ktet larger than Ktrig for a less acidic diol with a purely saturated hydrocarbon backbone. Thus, the electronic effects manifested in the acidity of the diol appear to be more significant than the strain release effect in determining the Ktet/Ktrig ratio.

BACKGROUND Aerosolized liquid (e-liquid) of electronic cigarettes can be toxic. Beyond the solvent (propylene glycol, vegetable glycerin) and nicotine, little is known about the liquid composition. Formaldehyde, a carcinogen and source of contact dermatitis, has been reported in the vaporized e-liquid, but no studies have assessed the actual e-liquid. OBJECTIVE The aim of the study was to evaluate e-liquid products for the presence of formaldehyde. METHODS Sixteen e-liquid products were purchased and analyzed for the release of formaldehyde using the chromotropic acid method of detection. RESULTS Of the 16 e-liquids purchased, 4 (25%) were positive for the presence of formaldehyde; 2 were flavored and 2 were nonflavored. All positive e-liquids were in pods or disposable electronic cigarette devices, and 2 were purchased from local vape shops. The average nicotine content in the positive e-liquids was 3.85% versus 4.03% in the negative e-liquids. CONCLUSIONS The e-liquid products contain toxic chemicals not declared on product labels, as shown in this study with 25.0% of e-liquids containing formaldehyde. All positive e-liquids were within pods or disposable devices. Continued analysis of e-liquids and increased product regulation are needed.

Hydroquinone (HQ) and catechol (CT) are considered as environmental pollutants with high toxicity. We have developed a simple electrochemical sensor using an anodized glassy carbon electrode modified with a stable 2-(phenylazo) chromotropic acid- (CH-) conducting polymer (PCH/AGCE). The PCH/AGCE sensor showed good electrocatalytic activity and reversibility towards the redox of HQ and CT in phosphate buffer solution (PBS, pH 7.0). The cyclic voltammetry (CV) in mixed solution of HQ and CT showed that the oxidation peaks of them became well resolved with a peak separation of 0.1 V. The detection limits of HQ and CT were 0.044 and 0.066 μM, respectively, in a wide linear response range of 1–300 μM for both. Moreover, the sensor displayed an excellent selectivity in the presence of common interferences. This study provided a simple, sensitive, and high recovery method for simultaneous and quantitative determination of HQ and CT in aqueous medium.

Background Formaldehyde resins may be used in textiles. Objective The aim of the study was to investigate the presence of formaldehyde in textiles using the chromotropic acid method. Method Clothing scraps (from local department store tailors, n = 77) and upholstery fabric cuttings (from a furniture reupholstery store, n = 22) were collected. Each fabric was cut into a 1-cm square and tested using the chromotropic acid method. Samples were retested in a systematic fashion (every 10th sample) to assess reproducibility. Results All 99 clothing and upholstery fabrics tested negative for formaldehyde release. Conclusions Our study suggests that textile manufactures may be using nonformaldehyde resins for durable press finishing in clothing likely to be tailored as well as fabrics used for furniture reupholstery. Additional studies involving other metropolitan areas and a variety of fabrics are needed to confirm these findings.

Background Formaldehyde is a common preservative and strong sensitizer. Objective The aim of the study was to evaluate the release of formaldehyde from baby/toddler wet wipes using the chromotropic acid method (CAM). Methods An online search of best-selling baby wipes was conducted. None declared formaldehyde or formaldehyde-releasing preservatives. Standard CAM procedures were used: a 1 × 1-in square of fresh wipe was placed in a bottle with an open vial of 4 mg/1 mL of chromotropic acid and sulfuric acid solution, sealed, and stored for 48 hours. Formalin and water served as controls. A blinded investigator graded color change (negative, indeterminate, mild, moderate, or strong). For quality control, 20% of all samples as well as all positives were retested. Results Fifty-one popular and highly reviewed baby and toddler wet wipe products were tested using CAM. Twelve wipes (24%) released formaldehyde (8 mild, 4 moderate/strong). Chromotropic acid method testing of 9 wipes (18%) was indeterminate and 30 (59%) were negative. Conclusions Almost one quarter of baby/toddler wet wipes released formaldehyde when evaluated with CAM. Patients and clinicians should be aware of this potentially undeclared source of this common allergen.

In order to develop a novel detection method for the degree of polymerization (DP) of insulating papers, methanol was used as an indicator to explore the relationship between methanol concentration and DP in this paper. After extraction from oil, the methanol was oxidized and reacted with chromotropic acid to generate a purple-red compound. The spectral detection method was used to detect the concentration of methanol by absorbance, and then, the corresponding relationship between the concentration of methanol and the DP of insulating paper was established. Moreover, the detection methods based on furfural and methanol were compared. The results showed that methanol appeared during the initial aging period of the insulation paper, and the linear relationship between the methanol concentration and the DP of insulating paper was good. Compared with furfural, methanol was more sensitive to the change of DP in the early aging period, which proved that methanol could be used as a new type of indicator of insulating paper.

The concentration of methanol in transformer oil has proved to be an effective indicator in the aging of paper/oil insulation. Traditional methods for detecting the concentration of methanol in transformer oil use gas chromatography (GC) and gas chromatography-mass spectrometer (GC-MS). Because these traditional methods are time consuming and are high skill operations, an improved method for detecting the concentration of methanol, which is rapid and is a lower skill operation, is proposed in this paper. This method detects the concentration of methanol using spectroscopy. Potassium permanganate is added to oxidize methanol into formaldehyde, which reats with chromotropic acid producing a mauve complex. From processing the spectrum of the complex using partial least squares, the linear correlation coefficient is increased to 0.999 and the minimum detected concentration is down to 10 parts per billion.

Oil-paper insulation in transformers plays an important role in the operation of power grid. At present, the aging (life assessment) of transformers are mainly conducted based upon the degree of polymerization, concentration of furfural, and the gas analysis of CO and CO2 in the transformer oil. However, these techniques lack sensitive response, especially in the early aging of oil-paper insulation. Methanol as a new indicator to evaluate the aging of insulating paper, is getting more and more attention. An evaluation method based on the measurement of methanol concentration using ultraviolet–visible spectrometer was proposed in this work. After the extraction from transformer oils, the methanol was oxidized using potassium permanganate. Then, chromotropic acid was used to react with the oxidation products (formaldehyde) to form a mauve clathrate, finally, the methanol content was measured using the spectroscopy. Different from traditional spectroscopy which calculate only by absorbance at the characteristic wavelength, this paper use the partial least squares method, obtain the relationship between the absorbance at selected regions and the concentration of methanol. The minimum detection limit for the proposed method was 10 ppb, whereas the correlation coefficient for the relationship between the absorbance and the concentration of methanol was as high as 0.99.

Chromotropic Acid Grafted Amphoteric Polyurethane (CAGAPU) was synthesized with Chromotropic Acid (CA) as a modifier for Polyurethane (PU). The structure of CAGAPU was confirmed by FT-IR, 1H-NMR. The retanning process and the experiments of CAGAPU with formaldehyde indicate the following: (1) The leather retanned by CAGAPU can be comparable or surpassed to the market PU-based retanning system in terms of shrinkage temperature and sensory performance. (2) The leather collagen fibers are smoother and orderly which provides a potential value for the appearance of the leather and fur industry. (3) The CAGAPU retanned system can bring down the free formaldehyde content in aldehyde tanned leather significantly. (4) The optimum dosage of CAGAPU is 20 g and the best retanning time is 6 h (5) The CAGAPU retanned system can reduce the free formaldehyde, Biochemical Oxygen Demand (BOD), Total Dissolved Solids (TDS) and Total Suspended Solid (TSS) from the source which retard pound on the economy and environment greatly compare to the traditional governance. Therefore, this paper provides the possibility for the sustainable development of leather. The work has changed the traditional way of “terminal treatment” and realized the “initial treatment” and may also offer a new idea of solving the problem of formaldehyde in the newly decorated houses or in the air.

A novel detection scheme using chromatographic retention was proposed for paper-based analytical devices (PADs). Using a wax printer and an ink-jet printer, the PADs consisted of a straight-flow channel, a circular sample zone, and a band of brilliant green (BG) printed at the connection between the sample zone and the flow channel. When a constant volume of a sample solution was applied to the sample zone, the BG band formed a colored bar along the flow channel that marked the adsorption and desorption of the paper substrate according to the principles of chromatography. If the sample solution contained an anionic complex of boric acid with chromotropic acid, the anionic complex enhanced desorption of the BG from the paper substrate via the formation of an ion-pair with the BG, which resulted in an elongated colored bar. Fundamental equations for the retention behavior of the BG on the PADs were derived using a model based on chromatographic principles and ion-pairing formation. A retardation factor, Rf, was correlated with the concentration of boric acid contained in the sample solutions. To enhance the adsorption of the BG, 2,2,6,6-tetramethylpiperidine 1-oxyl was used to oxidize the paper substrate. The oxidized paper substrate shortened the colored bar of a blank solution and formed a clear boundary for the color. When the analytical conditions were optimized for pH and the concentration of chromotropic acid, the PAD permitted the measurement of boric acid for a concentration ranging from 0.3 to 3 mM. The proposed model was validated when the fitting curve was calculated using the derived equations, which resulted in good agreement with the experimental data.

In this report, two chromotrope dyes, chromotropic acid (CA) and chromotrope 2R (CR), were explored as inhibitors against mild steel corrosion in 1.0 M sulfuric acid solutions at 303 K. Electrochemical, spectroscopic, chemical, and microscopic techniques, namely, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy, mass loss, and scanning electron microscopy (SEM), have been employed to evaluate the inhibition efficiencies (%IEs) of the examined organic dyes. The %IEs were found to increase with the inhibitors' concentrations, while they decreased with rising temperature. The outcomes of the PDP technique displayed that the examined inhibitors operated as mixed-type inhibitors with anodic prevalence. The impedance spectra described by Nyquist and Bode graphs in the corrosive environment and in the presence of various concentrations of the examined inhibitors showed single depressed capacitive loops and one-time constants. This behavior signified that the mild steel corrosion was managed by the charge transfer process. The SEM micrographs of the surfaces of mild steel samples after adding the examined inhibitors revealed a wide coverage of these compounds on the steel surfaces. Thus, the acquired high %IEs of the examined inhibitors were interpreted by strong adsorption of the organic molecules on the mild steel surface. This constructed a shielding layer separating the alloy surface from the corrosive medium, and such adsorption was found to follow the Langmuir isotherm. Furthermore, the evaluated thermodynamic and kinetic parameters supported that the nature of such adsorption was mainly physical. Results obtained from all employed techniques were consistent with each other and revealed that the %IE of the CR inhibitor was slightly higher than that of CA under similar circumstances. Finally, the mechanisms of both corrosion of mild steel in sulfuric acid solutions and its inhibition by the tested organic dyes were also discussed.

Methanol naturally exists in all plant products. In recent years, the consumption of certain kinds of herbal distillates has led to blurred vision, leading to neurotic blindness in Iran. The advanced methods needed for determination of methanol are not available in all parts of poor and developing countries. In this study, we evaluated some herbal distillates’ methanol with a new kit compared to gas chromatography for determining the efficacy of the kit. A gas chromatography apparatus was used to determine methanol concentration of 57 herbal distillates. At the same time, a spectrophotometer device was also used along with a newly designed kit based on the modified chromotropic acid method for the same purpose. All examined samples have different amounts of methanol from 21 to 770 mg/l. The methanol content of all samples was higher than the used kit’s limit of quantification (5 mg/l). The attained results by two used methods were very close together in both minimum (21 and 22 mg/l) and maximum (770 and 690 mg/l) amounts. The comparison of results was shown, and some of available herbal distillates in Iran have enough amounts of methanol to create chronic type of methanol poisoning. Our results suggested that the used kit had suitable efficacy for quantitative determination of herbal distillates’ methanol content. It was proved that the type of the herbal distillate did not affect the kit’s function. The new kit can be easily used with minimal equipment for quality control of herbal distillates in food industry area.