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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.

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 new thread-based platform for colorimetric detection of nitrite was developed based on a modified Griess assay. Cellulose thread was chemically modified with a p-aminobenzoyl group and impregnated with chromotropic acid as a coupling reagent. The functionalization of the thread was confirmed by Raman spectroscopy. The diazotization and coupling reaction occurred along the length of the thread to produce a colored band in the presence of nitrite. This allowed the measurement of the length of thread in relation to nitrite concentration. In this method, the optimum concentration of chromotropic acid for nitrite detection was 5 mM in 0.10 M sulfuric acid mixed with 0.2 M citric acid. With a sample volume of 15 μL, the obtained working range for nitrite detection was from 50 to 1000 μM, where the lowest nitrite concentration that could produce color on the platform was 25 μM. The proposed method was successfully used to detect nitrite in three different types of samples with acceptable recoveries (92.4–115.4 %) and Relative Standard Deviation (RSD) (4.3–10.4 %).

A simple, accurate, and economical method has been proposed to measure formaldehyde in aqueous samples. The method is based on quantification of classical chromotropic acid – formaldehyde violet spots developed on TLC. Different parameters such as concentration of chromotropic and sulfuric acid, time of heating and order of application of reagents have been studied to find out the optimum working procedure. Spots have been quantified by scanning the spotted TLC and analyzing the image in computer with Visual Basic 6.0 based graphic application. The study consisted of developing an appropriate calibration line, analyzing artificial and real samples, and comparing the new method with a standard spectrophotometric method (NIOSH Method-3500, 1994). It has been concluded that the present method had the capability for measuring formaldehyde in aqueous samples at trace level with high precision and accuracy, particularly when dealing with turbid and small volume samples where the standard method failed.

A film of benzenesulfonamide azo dye has been prepared by spray pyrolysis method onto BK7 glass substrate with average thickness of 2.7 μm. This azo dye was derived from sulfamethoxazole and chromotropic acid by the Fox method. The optical constants (refractive index, n, extinction coefficient, k, dielectric constant, ɛ, optical, σopt, and electrical, σe, conductivities) were calculated for azo dye film by using spectrophotometer measurements of the absorption, transmittance and reflectance at normal incidence in the spectral range 300–900 nm. Third order nonlinear properties has been characterized by calculating the effective thermal nonlinear refractive index, n2, and thermo-optic coefficient, dn/dT, of the azo dye solution using thermal lens technique. Furthermore, the thermal lens effect was utilized to demonstrate all optical switching for the sample solution.

Polypyrrole nanofibers (PPy-NF) were prepared by an oxidative template assembly method and utilized for the fabrication of N-doped activated carbon nanofibers (N-AC-NF). Capacitor cells, containing N-AC-NF electrodes were used for capacitive dye removal (CDR) from aqueous solutions. It was found that CDR method can be used for the removal of triphenylmethane and chromotropic acid family dyes from aqueous solutions. The analysis of cyclic voltammetry, galvanostatic charge-discharge and impedance spectroscopy data, coupled with results of quartz crystal microbalance studies, provided an insight into the influence of chemical structure, size, charge-to mass ratio, concentration and redox-active ligands of the dyes on the capacitive behavior, dye removal efficiency, reversibility and cyclic stability of the cells. The CDR method offers advantages for the dyes of chromotropic acid family, due to larger voltage window, good capacitive behavior, improved cyclic stability and higher power-energy characteristics. It was found that charge storage mechanism is mainly attributed to double layer capacitance. CDR is a promising method for water purification, which offers advantages of energy saving and simple electrode regeneration.

We report a sensitive and selective method for determination of boron in uranium samples by spectrofluorimetry in synchronous derivative mode. This method is based on the complexation of non-fluorescent boron with fluorescent chromotropic acid to form fluorescent boron–chromotrope complex. The spectrum of native fluorescence of chromotropic acid seriously overlaps with that of the complex and hence, synchronous derivative mode was employed in which physical separation of excess ligand and complex is not necessary. With the optimized experimental and instrumental conditions, limit of detection obtained is 2 ng mL −1 . The linear concentration range is 5–100 ng mL −1 with regression coefficient better than 0.997. The precision is better than 5% at 10 ng mL −1 level and 3% at 50 ng mL −1 level ( n =9). Fluorescence quenching by residual matrix elements in the final sample solution is corrected by slope-ratio method. The method is validated with reference materials and successfully applied to the uranium nuclear fuels with the accuracy of ±10%. The proposed method reduces sample size requirement; thereby reducing load of uranium recovery from analytical waste in case of enriched uranium based samples.

Chromotropic acid disodium salt (CHR) and its derivatives, such as 2,7-Bis(2-sulfophenylazo)chromotropic acid tetrasodium salt (CHR-BS), 2-(phenylazo)chromotropic acid disodium salt (CHR-P) and 2-(1-naphthyldiazenyl)chromotropic acid disodium salt (CHR-N) were investigated as new anionic dopants for chemical polymerization of polypyrrole (PPy) for application in electrodes of electrochemical supercapacitors (ES). The analysis of electron microscopy data and electrochemical testing results provided an insight into the influence of dopant structure, size and charge on the PPy powder morphology and electrochemical performance of PPy electrodes. The increase in the size and charge of the dopant molecules resulted in reduced powder agglomeration and lower particle size. The use of CHR-BS allowed the fabrication of non-agglomerated PPy powders with particle size below 50 nm. It was found that new anionic dopants allowed the fabrication of ES electrodes with high mass loading in the range of 20–40 mg cm −2 and good electrochemical performance. Due to the higher charge to mass ratio of CHR and CHR-BS, compared to CHR-P and CHR-N, the CHR and CHR-BS doped PPy showed higher capacitance. The specific capacitance of 7.2 F cm −2 was achieved using CHR-BS doped PPy. Moreover, CHR-BS doped PPy electrodes showed excellent cycling stability. The ES cells, containing CHR-BS doped PPy electrodes showed promising electrochemical performance.

Chromotropic acid (CTA), a dihydroxynaphthalenedisulfonic acid is a reagent that is widely used for dyestuff manufacture, as a chromogen-forming reagent for the analysis of formaldehyde and as an intermediate for azo derivatives used as analytical reagents. The synthesis of two new CTA-based macrocyclic tetra-sulfonamides 7 and 7a and their corresponding bis-sulfonamides 10 and 10a and their complexation properties toward tetra-n-butylammonium halides were studied. The X-ray structure of 10a was determined and it provided key evidence for an unexpected photochemical reaction that the tetra-sulfonamides underwent.

The enzyme-catalysed cleavage of ester bonds of poly(lactic-co-glycolic acid) (PLGA) has been monitored by an improved approach for the quantification of glycolic acid as indicator of copolymer hydrolysis. Glycolic acid released into the degradation medium was determined colorimetrically using chromotropic acid. The assay established is sensitive, as well as being both rapid and economical. The proposed method was applied to assess enzymatic degradation of a series of PLGA polyesters containing different proportions of monomers, end groups of PLGA chains and molecular weights. Among 22 commercially available hydrolytic enzymes (i.e. esterases, lipases and proteases) from different sources, the lipases from Candida antarctica, Candida cylindracea, Candida rugosa, Mucor miehei, Rhizopus arrhizus and porcine pancreas and the esterase from M. miehei all had a significant effect on PLGA degradation, often increasing the rate of ester bond cleavage by a factor of 25 compared to non-enzymatic hydrolysis. The most remarkable substrate specificity was observed for C. antarctica lipase with the rate of degradation being directly proportional to the glycolic acid content. In contrast, degradation by M. miehei esterase and R. arrhizus lipase were nearly independent of PLGA structure.

Electrophoretic deposition (EPD) method has been developed for the fabrication of manganese dioxide (MD)–multiwalled carbon nanotubes (MWCNTs) nanocomposites. Cationic tyramine hydrochloride (TA) and anionic gallic acid (GA), chromotropic acid disodium salt (CA) and benzoic acid (BA) were investigated as charging additives. The results of deposition yield measurements, quartz crystal microbalance studies and Fourier transform infrared spectroscopy data showed that OH groups are involved in the adsorption of the phenolic compounds on the MD nanoparticles. The adsorption mechanism is based on the deprotonation of the OH groups and surface complexation of Mn ions. It was shown that the phenolic molecules, such as TA, GA and CA can be used as charging additives for the EPD of MD. Composite MD–MWCNTs films were prepared by cathodic and anodic EPD using TA and GA, respectively. In this approach, TA and GA were used as common charging additives for two different materials: MD and MWCNTs. Scanning electron microscopy studies showed the formation of composite films containing well-dispersed MWCNTs in the MD matrix. The results of the thermogravimetric analysis demonstrated that the amount of the MWCNTs in the composite materials can be varied. The composite films were studied for the application in electrochemical supercapacitors (ES). The ES electrodes showed good capacitive behavior in the 0.5 M Na2SO4 electrolyte in a voltage window of 0–0.9 V versus a standard calomel electrode (SCE). The films prepared by cathodic EPD showed higher specific capacitance (SC) compared to the films prepared by anodic EPD with the highest SC of 553 F g−1 at the scan rate of 2 mV s−1.

The proton transfer reactions between chromotropic acid (CTA) and some amines including benzylamine (BA), triethylamine (TEA), pyrrolidine (PY) and 1,8-bis(dimethylamino) naphthalene (DMAN) have been investigated spectrophotometrically in methanol. A long wavelength band at 365 nm has been recorded due to the proton transfer (PT) complex formation. The proton transfer equilibrium constants K PT were estimated utilizing the minimum–maximum absorbances method. It has been found that K PT were not depend on the amine p K a values, but strongly depend on the formed structures of the PT complexes. Job ’ s method of continuous variations and photometric titrations were applied to identify the compositions of the formed PT complexes where 1:1 complexes (proton donor: proton acceptor) were produced. Due to the rapidity and simplicity of the proton transfer reactions and the stability of the formed complexes, a rapid and accurate spectrophotometric method for the determination of CTA was proposed for the first time.

Two simple and highly sensitive spectrophotometric methods were developed for the quantitative determination of the drug sildenafil citrate (SC), Viagra, in pure form and in pharmaceutical formulations, through ion-associate formation reactions (method A) with mono-chromotropic acid azo dyes, chromotrope 2B (I) and chromotrope 2R (II) and ion-pair reactions (method B) with bi-chromotropic acid azo dyes, 3-phenylazo-6-o-carboxyphenylazo-chromotropic acid (III), bis-3,6-(o-hydroxyphenylazo)-chromotropic acid (IV), bis-3,6-(p-N,N-dimethylphenylazo)-chromotropic acid (V) and 3-phenylazo-6-o-hydroxyphenylazo-chromotorpic acid (VI). The reaction products, extractable in methylene chloride, were quantitatively measured at 540, 520, 540, 570, 600 and 575 nm using reagents, I–VI, respectively. The reaction conditions were studied and optimized. Beer's plots were linear in the concentration ranges 3.3–87.0, 3.3–96.0, 5.0–115.0, 2.5–125.0, 8.3–166.7 and 0.8–15.0 μg mL −1 with corresponding molar absorptivities 1.02 × 10 4 , 8.34 × 10 3 , 6.86 × 10 3 , 5.42 × 10 3 , 3.35 × 10 3 and 2.32 × 10 4 L mol −1 cm −1 using reagents I–VI, respectively. The limits of detection and Sandell's sensitivities were calculated. The methods were successfully applied to the analysis of commercial tablets (Vigoran) and the recovery study reveals that there is no interference from the common excipients that are present in tablets. Statistical comparison of the results was performed with regard to accuracy and precision using Student's t - and F -tests at 95% confidence level. There is no significant difference between the reported and proposed methods with regard to accuracy and precision.

A method for solid phase extraction of trace metals such as Cd2+, Cr6+, Cu2+, Fe3+, Mn2+, Ni2+, Pb2+ and Zn2+ using nanometer-sized alumina coated with chromotropic acid prior to determination by inductively coupled plasma atomic emission spectrometry (ICP-AES) has been developed. Various influencing parameters on the separation and preconcentration of trace metals, pH, flow rate, sample volume, amount of adsorbent, concentration of eluent and sorption kinetics have been studied. The detection limits for Cd2+, Cr6+, Cu2+, Fe3+, Mn2+, Ni2+, Pb2+ and Zn2+ were found to be 0.14, 0.62, 0.22, 0.54, 0.27, 0.28, 0.53 and 0.38 ng ml− 1, respectively. The adsorption capacity of the solid phase adsorption material is 10.3, 11.3, 14.5, 16.4, 15.1, 11.7, 15.4 and 16.8 mg g− 1 for Cd2+, Cr6+, Cu2+, Fe3+, Mn2+, Ni2+, Pb2+ and Zn2+, respectively. The preconcentration factor was obtained in the range of 50–100 for all studied metal ions. Coexisting ions over a high concentration range have not shown any significant effects on the determination of aforesaid metal ions. The accuracy of the proposed method was tested by standard reference materials (NIST 1643e: water, NIST 1573a: tomato leaves and NIST 1568a rice flour) and natural waters and the results obtained were in good agreement with the certified values.

The present work reports the first sequential injection (SI) method for the spectrophotometric determination of Ti(IV). The method is based upon the reaction of Ti(IV) with chromotropic acid (CA) in acidic medium to form a water-soluble complex (lambda(max)=420nm). The chemical and instrumental variables of the system that affected the reaction were studied. Selectivity was greatly enhanced using ascorbic acid. A linear calibration graph was obtained in the range 0.2-10.0mgl(-1) Ti(IV) at a sampling frequency of 24h(-1). The precision was satisfactory (s(r)=1.5% at 5.0mgl(-1) Ti(IV), n=12) and the 3sigma limit of detection, c(L), was 0.7mgl(-1) (n=10). The developed method proved to be adequately selective and was applied successfully to the analysis of real samples (dental implant and natural Moroccan phosphate rock) giving accurate results based on recovery studies (98-105%).

In this work, polyurethane foam (PUF) loaded with 2-(6'-methyl-2'-benzothiazolylazo)chromotropic acid (Me-BTANC) was packed in a minicolumn and it was used in an on-line preconcentration system for cadmium and lead determination. Optimum hydrodynamic and chemical conditions for metal sorption were investigated. The effects of several foreign substances on the adsorption of cadmium and lead were also reported. The enrichment factor obtained was 37 (Cd and Pb) for 180 s preconcentration time. The proposed procedures allowed the determination of metals with detection limits (3 sigma) of 0.80 and 3.75 microg L(-1) (0.10 and 0.47 microg g(-1) of solid sample) for cadmium and lead, respectively. The precision of the procedures was also calculated: 3.1 (Cd 10 microg L(-1)) and 4.4% (Pb 100 microg L(-1)). The accuracy of the procedure was checked by analysis of the certified reference materials Spinach Leaves and Fish Tissue. Cadmium and lead contents in environmental samples (black tea, spinach leaves, natural and tap water) were determined by applying the proposed procedure.

The present work reports the first spectrofluorimetric gas-diffusion flow injection (GD-FI) assay for the determination of chlorine dioxide in water samples (tap, mineral and soda water). The method is based on the fluorescence quenching of chromotropic acid (CA) (λex. = 347 nm, λem. = 371 nm) caused by the analyte. The chemical and instrumental variables of the system were studied in terms of maximum sensitivity. The gas-diffusion cell was thermostated at 40 °C to enhance the vaporization of chlorine dioxide and thus the sensitivity of the method. The quenching effect of chlorine dioxide on CA was linear in the range 0.09–3.41 mg l− 1, while the precisions either close to the quantitation limit or near to the middle of the linear section of the calibration graph were satisfactory in both cases (sr = 2.6% and 1.5% (n = 10) at 0.17 and 1.71 mg l− 1 level, respectively). The developed method proved to be adequately selective and sensitive with 3σ limit of detection equal to cL = 0.03 mg l− 1. The application of the assay to spiked tap, mineral and soda water samples yielded accurate results with recovery values in the range 94.1–105.9%.

An agarose-based anion exchanger (Q-Sepharose) was loaded with chromotropic acid (CTA) and used for column preconcentration and determination of copper by flame AAS. Preliminary experiments indicated that a sample pH of 5.7-6.5 is best suited for accumulation of copper and a 2.5ml portion of a 0.02moll(-1) HCl solution can efficiently desorb the analyte from the column. An incomplete factorial design was used for optimization of five different variables that affect recovery of copper. The results indicated that ionic strength, pH and sample volume variables are the most important effects, respectively. Hence, these variables and their possible interactions were studied more carefully. In optimized conditions, the column could tolerate up to 0.18moll(-1) sodium nitrate in the matrix. A 5ml portion of a 0.02moll(-1) CTA was sufficient for loading of a 0.5ml column prior to preconcentration of copper from a 150ml sample solution. Matrix ions of Ca(2+), Mg(2+), Na(+) and K(+) and potentially interfering ions of Pb(2+), Ni(2+), Cd(2+), Co(2+), Zn(2+) and Mn(2+) with relatively high concentrations did not have any significant effect on the recovery of the analyte. A preconcentration factor of 60 and a detection limit of 1.0mugl(-1) was obtained for the determination of copper by the flame AAS method. A precision better than 2.5%, expressed as R.S.D., was also achieved. Application of the method to tap water and two different river water samples resulted in values well confirmed by direct determinations with ET-AAS.

Ozone has become the oxidant of choice for water disinfection, especially in large water treatment facilities. This paper describes a fast and sensitive method for the determination of ozone content by reaction with photoactivated chromotropic acid (CA, 4,5-dihydroxynaphthalene-2,7-disulfonic acid), which results in intense chemiluminescence (CL). Freshly ozonated water from a recirculating ozonizer/reservoir is injected into a carrier stream of deionized water in the flow-injection mode. This flow mixes with a stream of photoactivated CA solution in a spiral cell placed directly on top of an inexpensive miniature (8mm diameter active area) photomultiplier tube (PMT). Alkaline CA is photoactivated by passing it through a FEP-Teflon((R)) coil (residence time approximately 50s) wrapped around a 1W UV lamp emitting at 254nm; without photoactivation, the signal is approximately 70-fold lower. The S/N=3 limit of detection for aqueous ozone is 3mugl(-1) and good response slope is obtained up to an ozone concentration of 1.4mgl(-1), the highest that could be made in this study. The response obeyed a quadratic equation with r(2)=0.9984. No interference from permanganate ion is observed. The proposed system was applied to the monitoring of ozonation status of a playa lake water that exhibited significant ozone demand.

A novel, single and robust solid surface fluorescence-based sensing device assembled in a continuous flow system has been developed for the determination of trace amounts of aluminium in water samples. The proposed method is based on the transient immobilization of the target species on an appropriate active solid sensing zone (C18 silica gel). The target species was the fluorogenic chelate, formed as a result of the on-line complexation of Al(III) with chromotropic acid (CA) at pH 4.1. The fluorescence of the complex is continuously monitored at an emission wavelength of 390 nm upon excitation at 361 nm. The instrumental, chemical and flow-injection variables affecting the fluorescence signal were carefully investigated and optimized. After selecting the most suitable conditions, the sensing system was calibrated in the range 10–500 μg l−1, obtaining a detection limit of 2.6 μg l−1, and a R.S.D. of 2.2%, with a sampling frequency of 24 h−1. In addition, the selectivity of the proposed methodology was evaluated by performing interference studies with different cations and anions which could affect the analytical response. Finally, the proposed method, which meets the EU regulations regarding the aluminium content in drinking waters, was satisfactorily applied to different water samples, with recoveries between 97 and 105%. The simplicity, low cost and easy operation are the main advantages of the present procedure.

This work reports the application of a sequential-injection analysis (SIA) method for the determination of boron. The method relies on the enhancement of the fluorescence ( λ ex =313 nm, λ em =360 nm) of chromotropic acid (4,5-dihydroxynaphthalene-2,7-disulphonic acid-CA) as a result of its complexation with boric acid (BA). Individual zones of the sample, the CA solution in a suitable buffer and a NaOH solution were aspirated in the holding coil of the SIA apparatus. As the zones were propelled towards the detector, zone penetration in the sample–CA interfaces occurred resulting in the formation of the strongly fluorescent BA–CA complex. The native fluorescence of the CA was quenched by the alkaline environment established as a result of the mixing at the CA–NaOH interface. The chemical and instrumental parameters affecting the fluorescence intensity were investigated and the influence of potential interferents was investigated. After selecting the most suitable conditions, the calibration plot for boron was linear in the range of 8–350 μg l −1 with a 3 σ limit of detection of 3 μg l −1 and a relative standard deviation of 2.7% at the 90 μg l −1 boron level ( n =8). Finally, the method was applied to the determination of boron in natural waters and pharmaceutical products with revoveries in the range of 96–106%.

In the present study, a spectrophotometric method for the determination of formaldehyde by using chromotropic acid was devised, in which the use of potentially hazardous and corrosive concentrated sulfuric acid was eliminated and advantageously replaced by a mixture of H 3 PO 4 and H 2 O 2 . The reaction between formaldehyde and chromotropic acid (CA) in a concentrated phosphoric acid medium was accelerate by irradiating the mixture with microwave energy for 35 s (1100 W), producing a violet–red compound ( λ max =570 nm). Beer's Law is obeyed in a concentration range of 0.8–4.8 mg l −1 of formaldehyde with a good correlation coefficient ( r =0.9968). The proposed method was applied in the analysis of formaldehyde in commercial disinfectants. Recoveries were within 98.0–100.4%, with standard deviations ranging from 0.03 to 0.13%.

The complex formation reactions of boric and boronic acids (RB(OH) 2 : R=OH, n-Bu, Ph, and m -NO 2 Ph) with 4-isopropyltropolone (Hipt) and chromotropic acid (H 2 cht 2− ) have been studied kinetically at various pH. The reactions of H 2 ipt + with boronic acids were faster than those of Hipt by a factor of 1.5–11, and fully deprotonated ipt − also reacted with m -NO 2 PhB(OH) 2 , but slower than Hipt. The tetrahedral m -NO 2 PhB(OH) 3 − ion did not react with Hipt. Reaction routes for the complexation of boric acid with chromotropic acid could not be specified because of the unexpected problem of proton ambiguity. Mechanism for the reactions of boronic acids with bidentate ligands was discussed in terms of rate determining chelate ring closure. It was concluded that at least one proton is necessary for the OH − in the tetrahedral intermediates to be eliminated smoothly as water, and a doubly hydrogen-bonded intermediate was proposed for the reactions with diprotic ligands.

An electrochemical method for the determination of lead has been developed using overoxidized polypyrrole (OPPy) electrode doped with 2(2-pyridylazo)chromotropic acid anion (PACh 2� ). The PACh 2� acts both as a chelating agent and a counter anion within the polypyrrole matrix. In a typical assay, Pb 2� is accumulated on a solid electrode via the formation of a lead � /PACh complex at open circuit. The electrode containing the Pb 2� PACh 2� is then transferred to a 0.1 M acetate buffer where it is subjected to differential pulse anodic stripping voltammetry. The resulting stripping peak current was linearly related to the concentration of lead. The method has been optimized with respect to pH, concentration of chelating agent, accumulation time, reduction potential and time. The detection limit was found to be 10 ng ml � 1 with a linear range of 0 � /200 ng ml � 1 . The method has been validated for the determination of lead using spiked potable water at 25 ng ml � 1 . The average recovery was 93.4% with a relative standard deviation of 8.54%. # 2002 Elsevier Science B.V. All rights reserved.

Four chelating matrices prepared by coupling Amberlite XAD-2 with chromotropic acid (AXAD-2-CA or 1), pyrocatechol (AXAD-2-PC or 2) and thiosalicylic acid (AXAD-2-TSA or 3) through azo spacer and impregnation of Amberlite XAD-7 with xylenol orange (AXAD-7-XO or 4) have been studied for enrichment of lead(II). All the four resins quantitatively sorb Pb(II) at pH 3.0-8.0 when the flow rate is maintained between 2 and 10 mlmin(-1). HNO(3) (0.5-4.0 M) instantaneously elutes Pb(II) from all the four chelating resins. The sorption capacity is in the range 16.0-186.0 mumolg(-1) and loading half time (t(1/2)) between 3.2 and 15.5 min. The tolerance limits of electrolytes (NaCl, NaBr, NaNO(3), Na(2)SO(4), Na(3)PO(4)) and cations (Ca and Mg) are reported. Phosphate interferes in the sorption with 3 and 4. The limit of detection and limit of quantification have been found to be in the ranges 2.44-7.87 and 2.76-8.64 ngml(-1), respectively. Lead has been determined in river (RSD approximately 2.6-12.8%) and tap (RSD approximately 1.8-7.2%) water samples.

A spectrophotometric method for the determination of dipyrone in pharmaceutical preparations is proposed. This method is based on selective oxidation of dipyrone, in the presence of sulphuric acid, splitting off formaldehyde which reacts with chromotropic acid, also in a sulphuric acid medium, producing a violet–red compound (λmax 575 nm). Beer’s law is obeyed in a concentration range of 0.57–5.7 ppm dipyrone with an excellent correlation coefficient (r=0.9997). The results show a simple, accurate, selective and readily applied method to the determination of dipyrone in pharmaceutical products. The analytical results obtained for these products by the proposed method are in agreement with those of the Brazilian Pharmacopoeia procedure. No interference was observed from common excipients in formulations. Recoveries were within 98.7–101.2%, with standard deviations ranging from 0.2 to 1.7%.

A new inorgano-organic ion exchanger has been prepared by anchoring chromotropic acid (4,5-dihydroxynapthalene-3,7-disulphonic acid, disodium salt) onto zirconium molybdate (ZM). The inorgano-organic ion exchanger has been termed ZMCA. ZM and ZMCA have been characterised for elemental, spectral and thermal analyses. Chemical stability in several acidic, basic and organic media has been assessed. Ion exchange capacity (i.e.c.) for these materials has been determined and the effect of heating on i.e.c. has been studied. The distribution coefficient Kd for several metal ions has been determined and compared. The new material ZMCA exhibits high Kd values for several metal ions compared with ZM. It is also stable up to a fairly high temperature, besides exhibiting stability in different acidic, basic and organic media. ZMCA thus exhibits the characteristics of a promising ion exchanger.

A new ultraviolet spectrophotometric method for hexavalent chromium in water based on the oxidation of chromotropic acid by Cr(VI) in 0.12 mol/liter HCl medium is described. The molar absorptivity is 1.76 × 10 4 liters·mol −1 cm −1 . The detection limit is 0.024 μg ml −1 Cr. This sensitive and very simple ultraviolet spectrophotometric method for microquantitative determination of Cr(VI) in water has good precision and accuracy.

The β -type complex formed between yttrium and p -carboxychlorophosphonazo (CPApK) has been studied. It was found that Y-CPApK complex can give a maximum absorptivity in a buffer media of HAc–NaAc ranging from pH 3.5–4.3 and at a wavelength of 732 nm. Under the conditions employed, the molar absorptivity was found to be 7.72×10 4 l mol −1 cm −1 and the molar ratio of Y-CPApK was 1:2. The linear range was within 2–16 μg of yttrium in 25 ml solution. One of the characteristics of the complex was its high tolerance for calcium and hence a method of separation and enrichment of microamounts of yttrium by using calcium oxalate precipitate was developed and applied to measure yttrium in nickel-base alloys. The parameters which were related to the formation of the β -type complex of Y-CPApK were discussed and a comparison of existing β -type complexes between yttrium and the chlorophosphonazo reagents of chromotropic acid was made.

Objective: Five methods for oxalate analysis in urine are compared with respect to reliability, accuracy, and practicability. Results: Suppressed and unsuppressed ionchromatography, as well as the enzymatic Sigma-Kit, achieve low coefficients of variation for the within-batch imprecision (1.1–8.0%) and between-day imprecision (1.6–7.2%). The results of these methods are comparable and the mean recovery rate ranges between 99.7% and 100.9%. The enzymatic Boehringer-Kit gives higher CV (3.1–9.5%) and the results are lower than those obtained by the methods mentioned above; the recovery rate is sufficient (92.4%). Conclusion: The handling of the chromatographic methods is very easy, whereas the enzymatic methods require more manual work. In relation to sample throughput, changes for the enzymatic methods are about twice as high as for the chromatographic methods. In respect to reliability and accuracy, the chromotropic acid method cannot be recommended (recovery rate 68%).

A highly sensitive and selective spectrofluorimetric method for the determination of 0.05-2.00 ?g germanium is described. Germanium is treated with chromotropic acid at pH 2.5 and the resultant anionic complex is extracted as an ion pair with rhodamine B into toluene. Addition of butanol to the organic extract releases the fluorescent dye and facilitates its measurement at 570 nm after exciting at 540 nm. The method provides a detection limit of 0.003 ?g ml-1 and is virtually free from interference from extraneous ions. The relative standard deviation is 2.9% for ten determinations of 1.0 ?g germanium. The method has been applied to the determination of germanium in various ores, minerals and rock samples.A highly sensitive and selective spectrofluorimetric method for the determination of 0.05-2.00 ?g germanium is described. Germanium is treated with chromotropic acid at pH 2.5 and the resultant anionic complex is extracted as an ion pair with rhodamine B into toluene. Addition of butanol to the organic extract releases the fluorescent dye and facilitates its measurement at 570 nm after exciting at 540 nm. The method provides a detection limit of 0.003 ?g ml-1 and is virtually free from interference from extraneous ions. The relative standard deviation is 2.9% for ten determinations of 1.0 ?g germanium. The method has been applied to the determination of germanium in various ores, minerals and rock samples.

In this paper, the new topological indices A(x1)-A(x3) suggested in our laboratory and molecular connectivity indices have been applied to multivariate analysis in structure-property studies. The topological indices of twenty asymmetrical phosphono bisazo derivatives of chromotropic acid have been calculated. The structure-property relationships between colour reagents and their colour reactions with ytterbium have been studied by A(x1)-A(x3) indices and molecular connectivity indices with satisfactory results. Multiple regression analysis and neural networks were employed simultaneously in this study.

An ultra-sensitive and highly selective nonextractive fluorimetric method is presented for the rapid determination of aluminium at nano-trace levels using chromotropic acid as a fluorimetric reagent [lambda(ex) = 360 nm and lambda(em) = 390 nm] in the pH range of 4.1-4.7. The fluorescence intensity of the metal chelate (2:3 complex) reaches a constant value within 1/2 hr and remains unchanged for over 48 hr. The fluorescence intensity aluminium concentration calibration curve is collinear between 1 and 300 ng/ml of Al. A constant fluorescence intensity is obtained over a wide range (1:50-1:1500) of Al:reagent molar concentrations. Large excesses of over 60 cations, anions and complexing agents (like tartrate, oxalate, phosphate, thio-urea, SCN(-), etc.) do not interfere in the Al determination. The developed method was successfully used in assaying aluminium in several standard reference materials (Al-bronze, brass, stainless steel) as well as in some environmental and biological samples. The method is very precise and accurate (S.D = +/-0.001 on 10 ng/ml; 11 determinations).

We evaluated two chemical methods for quantifying mannitol in serum, based on the oxidation of mannitol by periodate, and measurement of the formaldehyde formed with chromotropic acid (colorimetry) or acetylacetone (fluorometry). We found interference in these methods by serum glycerol. Additionally, a high-performance liquid chromatography (HPLC) method was evaluated and found to be specific but impractical for routine use. We therefore, developed an enzymatic fluorometric procedure, based on the oxidation of mannitol by beta-NAD to fructose and NADH, in the presence of the enzyme mannitol dehydrogenase (MD). MD is not commercially available and was partially purified from cultures of Leuconostoc mesenteroides. This new method is specific, sensitive, simple, and accurate and is proposed as the method of choice for measuring mannitol in the serum of patients who received this sugar alcohol during routine hemodialysis treatment.

Chromogens of different classes, viz., arylazo derivatives of resorcinol, naphthols, naphthylamines, chromotropic acid and its cyclic modification, and also someformazans, are investigated using high-resolution solid-state NMR 13 C CP MAS. The technique revealed spectral data pertinent to the similarity and difference of the compounds in the solid state and in solution.

The quantitative spectrophotometric determination of V(V) by its catalytic effect on the oxidation of chromotropic acid [the disodium salt of 4,5-dihydroxynaphthalene-2,7-disulphonic acid (CS)] by potassium bromate has been adapted to a flow system employing a rapid sample and reagent introduction manifold, in which valves and carrier streams are omitted without decreasing the precision or increasing the sample consumption relative to flow-injection analysis (FIA). Measurements are made at 420 nm. Coexisting Fe(III) can be determined simultaneously at the same wavelength by its more rapid colour chelate formation with CS. An accurate determination of V(V) and Fe(III) in the mixture was developed with a sample throughput of about 60 hr.

Boron as boric acid was determined with chromotropic acid using a fluorescence detection—flow injection system. The flow system consisted of three streams, a carrier, a reagent and an alkaline solution. By mixing 0.5 M sodium hydroxide solution as the alkaline solution, the high background fluorescence of the reagent was diminished and the sensitivity was enhanced. The determinable concentration of boric acid was in the range 1 × 10−8–1 × 10−4 M. The detection limit was 5 × 10−9 M of boron, corresponding to a signal-to-noise ratio of 3. The sample throughput was 60 h−1. The method was applied to the determination of boron as boric acid in water samples.

Formaldehyde in air was detected and assayed with a piezoelectric quartz crystal coated with a 7,10-dioxa-3,4-diaza-1,5,12,16-hexadecatetrol/chromotropic acid solution. Water vapor and several gaseous interferents were removed by passing the sampling stream through a column of anhydrous magnesium perchlorate. The response curves were linear in the concentration ranges 0.4-4.5 and 0.4-3.6 ppm v/v CH(2)O with and without the scrubber column, respectively. A single coating was used for 12 days (500 assays) without significant loss in sensitivity. With a single-point daily recalibration, the useful lifetime of the coating is about 2 months.

A simple, rapid and sensitive method has been worked out for spectrophotometric determination of macro and micro amounts of alumina in ceramic raw materials and finished products, including glasses. The method is based on the extraction of aluminum oxinate into chloroform after masking of titanium with chromotropic acid and of iron with ascorbic acid and 1,10-phenanthroline or ferrocyanide at pH 5.2. The absorbance is measured at 385 nm. Interference by Cu, Zn, Cd, Ni and Co, when present, is overcome by stripping them as cyanide complexes by shaking the chloroform extract with potassium cyanide solution. Zr is masked with quinalizarin sulphonic acid and fluoride with BeSO(4).

Bisulphite is an unsuitable reagent for removing the excess of periodate from solution prior to the determination of formaldehyde, because the reaction is too slow. Serious errors may arise, but they can be eliminated by using an excess of myo-inositol to reduce the periodate.

The preconcentration of aluminium(III) traces in the form of anionic complexes on an anion-exchanger is described. The ligands used to form anionic complexes are hydroxide, sulphosalicylic acid, chromotropic acid and 2-(4-sulphophenyl)-1,8-dihydroxynaphthalene-3,6-disulphonic acid. Recoveries were evaluated under different conditions and in the presence of potential interferences (surfactants, inorganic salts, organic anions). The experimental behaviour is compared with that which can be predicted from the computed distribution of the different species. The results show that chromotropic acid is superior for the recovery and preconcentration of Al(III).

A method of estimating urinary oxalate is described. Impurities which might otherwise interfere with the estimation are removed by means of an ion-exchange resin. The oxalate is then reduced to glycolic acid, which forms a coloured compound with chromotropic acid. It can then be estimated colorimetrically. No special equipment is required, oxalate recovery is good, and the method is reproducible and precise.

The effect of carboxyl sulpho and arsono groups on the protonation and dissociation constants of mono-azo and bis-azo chromotropic acid derivatives has been investigated. From the value obtained for the effect of the substituents the equation ortho -effect = log K ortho -log K para has been derived. The causes of the effect are discussed

This paper reports the results of investigations into photo-chemical oxidation and reduction of Fe 2+ /Fe 3+ and Ti 3+ /Ti 2+ redox systems, that are used to constitute a redox cell. The investigations have been carried out with the object of developing a suitable photo activator to charge redox cells by photochemical means. The present work investigates the photo-oxidation of Fe 2+ /Fe 3+ and the photo-reduction of Ti 3+ /Ti 2+ in presence of chromotropic acid (1,8-dihydroxynaphthalene-3,6-disulfonic acid).

l,8-Dihydroxynaphthalene-4-sulfonic acid (DHNS) is described as a new reagent for the extraction—spectrophotometric determination of boric acid. The reagent and its boron complex are extracted into 1,2-dichloroethane as ion-associates with tetradecyldimethyl-benzylammonium chloride (zephiramine). The extracted complex of boron—DHNS—zephiramine has the composition 1:2:3 and is stable to back-washing with 1 M sodium chloride solution (pH 9.2), whereas the excess of reagent co-extracted is removed to the aqueous phase. The apparent molar absorptivity of the complex in the organic phase is 2.45 × 10 4 l mol -1 cm -1 at 341 nm, which is 1.7 times larger than that with chromotropic acid. Addition of EDTA prevents most interferences. The improved method with DHNS is successfully applied to the determination of boron as boric acid in waters. The exchange equilibrium constants, , for the reagent and complex were also determined for four monovalent anions (X - = Cl - , Br - , NO 3 - and I - ). Some of these constants are compared with those pertaining to chromotropic acid and 1,8-dihydroxynaphthalene.

The stepwise stability constants of complexes of chromotropic acid with Cr(III). Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) are determined by the Calvin-Bjerrum potentiometric titration method in a medium of 0.1 μ ionic strength and at 27±0.1°C. The solid complexes of the previously mentioned transition metal ions in addition to V(IV) and Mn(II) were prepared and subjected to elemental analysis, IR. thermogravimetric and thermal conductimetric studies. It was found that for all specimens the activation energies lie in the range of typical semiconductors. The conduction mechanism was explained according to the ligand field theory.

A passive sampling device based on the principle of diffusion has been developed for the determination of formaldehyde in ambient air. The sampler consists of a capped glass tube (with approximate dimensions of 2.4 × 9 cm) containing a glass-fiber filter treated with NaHSO3. In the field, the device collects a sample by being uncapped for a specified sampling time. After being recapped and returned to the laboratory, the filter is analyzed by the chromotropic acid (CTA) method. Laboratory validation studies were conducted by exposing the sampling devices for 1 week to dry formaldehyde gas generated by passing trioxane vapor over an acid catalyst bed. In these tests, formaldehyde concentrations ranged from 0.05 to 0.80 mL/m3. Reproducibility was excellent, with relative standard deviations averaging 5.4% for five constant concentrations. The lower detection limit was determined to be 3.6 mL/m3 h. In an occupational environment an 8-h sample would be sufficient to detect compliance with the OSHA permissible exposure limit of 3 mL/m3; in a residential environment a 1-week sample would allow detection of 0.025 mL/m3 for indoor air quality audits.

The possibility of using bromopyrogallol red, chromatropic acid and alizarin red S as complexing agents for the selective separation of Ti and Zr from the other metal ions was investigated. Bromopyrogallol red was used for the separation of titanium(IV) from Co(II), Cu(II), Cr(III) and Fe(III), chromotropic acid for the separation of titanium from Ni, Cu and Fe, and alizarin red S for the separation of zirconium from Cu, Ni and Al. Using chromotropic acid it is possible to separate titanium(IV) from large excess of metal ions giving weak complexes. By elution of metal ions which formed less stable complexes with the complexing agent no evidence of ligand in the eluate was discovered. This proves that very strong binding of ligand on anion-exchange resin occurs. It was found that for separation of Ti, chromotropic acid is more suitable than bromopyrogallol red.

Five recognised methods for estimating formaldehyde were compared for suitability for determining residual free formaldehyde levels in veterinary vaccines. For products in which no formaldehyde neutralization procedure had been used, the acetylacetone (Hantzsch) reagent method gave less variable results than the methods using phenylhydrazine, MBTH, tryptophan or chromotropic acid reagents. The Hantzsch reagent method was also the quickest to carry out and did not involve the use of hazardous chemicals. For vaccines in which metabisulphite had been used to neutralize formaldehyde the phenylhydrazine and MBTH reagent methods were both suitable for estimating residual free formaldehyde, the MBTH method being the less variable and less hazardous of the two. None of the methods could be applied directly to oil-emulsion vaccines.