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The selective fluorescence sensing of hypochlorite (ClO−) was achieved at pH 7.4 by a simple analytical procedure through the fluorescence quenching of autoclave synthesized carbon dots (CDs), which used as precursor an adduct formed between 3-aminophenylboronic acid (APBA) and alizarin red S (ARS). The use of this adduct allowed the preparation of CDs with a red shifted emission (560 nm) and excitation in the visible range (490 nm). Quantification of hypochlorite was achieved at physiological pH (pH 7.4) in aqueous solutions by fluorescence quenching with a linearity range of 0–200 μM (limit of detection of 4.47 μM, and limit of quantification of 13.41 μM). The selectivity of hypochlorite sensing was confirmed by comparison with other potential analytes, such as glucose, fructose and hydrogen peroxide. Finally, the validity of the proposed assay was further demonstrated by performing recovery assays in different matrices. Thus, this CDs allows the fluorescent sensing of ClO− with spectral properties more suitable for in vitro/in vivo applications.

In this paper, the potential of confocal microfluorescence spectroscopy is explored for the characterization of selected red lake pigments and paints based on alizarin, purpurin and eosin (weak, medium and strong emitters). The anthraquinone pigments have been used since ancient times by artists, and eosin lakes were used by impressionist painters. Reconstructions of artists paints based on 19th century recipes are examined. The paints were made using the lake pigments bound in a range of binding media including gum arabic, collagen, a vinyl emulsion and linseed oil. The acquisition of the spectra is rapid, with high spatial resolution and the data reliable and reproducible. Together with full emission spectra, it was possible to acquire well-resolved excitation spectra for purpurin, alizarin and eosin based colors. The present investigation suggests that micro-emission fluorescence can also be used as a semi-quantitative method for madder lake pigments, enabling the determination of purpurin lake ratio in a mixture of purpurin and alizarin, which is important for provenance studies. The data obtained with microfluorescence emission with those acquired with fiber-optic fluorimetry are compared. The spatial resolution used, 8 [mu]m, is appropriate for the analysis of individual pigments particles or aggregates in a paint film. Micro-emission molecular fluorescence proved to be a promising analytical tool to identify the presence of selected red lake pigments combined with a range of binding media. http://www.sciencedirect.com/science/article/B6THP-4PD4X9S-1/1/9160e8925e9e8f8b24617f15558da5b7

The preconcentration of fluoride is achieved on-line by converting it to trimethylsilane which then diffuses through a gas permeable membrane to be absorbed in a stationary sodium hydroxide acceptor stream. This stream is enclosed in the sample loop of an injection valve and after preconcentration, the fluoride sample is flushed into a flow injection manifold for spectrophotometric analysis by the zirconium/alizarin S procedure at 520 nm. The method is suitable for fluoride analysis in the range 0.1-10 mg/l at a sampling rate of 17/hr. Phosphate does not interfere and aluminium and iron can be tolerated at 200 and 500 times the fluoride concentration, respectively. The LOD was calculated to be 0.055 mg/l and LOQ was found to be 0.18 mg/l.

This work presents the use of sequential injection analysis (SIA) and the response surface methodology as a tool for optimization of Fenton-based processes. Alizarin red S dye (C.I. 58005) was used as a model compound for the anthraquinones family, whose pigments have a large use in coatings industry. The following factors were considered: [H 2 O 2 ]:[Alizarin] and [H 2 O 2 ]:[FeSO 4 ] ratios and pH. The SIA system was designed to add reagents to the reactor and to perform on-line sampling of the reaction medium, sending the samples to a flow-through spectrophotometer for monitoring the color reduction of the dye. The proposed system fed the statistical program with degradation data for fast construction of response surface plots. After optimization, 99.7% of the dye was degraded and the TOC content was reduced to 35% of the original value. Low reagents consumption and high sampling throughput were the remarkable features of the SIA system.

The membrane filtration was examined as an effective and selective method for collection of Al(III) ions from aqueous solutions using Alizarin Yellow R, one of a pH-indicator, as a precipitating reagent. For preparation of aqueous solutions without precipitate or turbidity, a non-ionic surfactant, Triton X-100, was used as a solubilizing reagent for insoluble materials. Three metal ions, Al(III), V(III) and Cu(II) ions, were able to be collected as yellow-orange precipitates from aqueous solutions controlled in a range of pH 4-7, pH 4-9, and pH 5.5-12, respectively, on a membrane filter by filtration under suction. Hydrogen peroxide and o-phenanthroline were found to be capable of masking V(III) and Cu(II) ions in a range of pH 5.5-8 in which Al(III) ions were collected. This membrane filtration was applied to selective separation and determination of Al(III) ions in tap water.

A sensitive and selective procedure for the determination of trace silver(I) at alizarin violet modified carbon paste electrode has been developed. Silver(I) was accumulated on the electrode surface via complex formation with modifier in 0.1 mol/L acetate buffer (pH 5.2). After electrochemical reduction of silver(I) had been carried out, the reoxidation wave of silver(0) appeared at 0.05 V (versus SCE) on scanning the potential in the positive direction in 0.1 mol/L H2SO4 + 2.0 × 10−4 mol/L KBr. For a preconcentration time of 3 min, the detection limit is 1.0 × 10−10 mol/L and the linear range is from 3.0 × 10−10 to 1.2 × 10−7 mol/L. Many coexisting metal ions have little or no effect on the determination of silver(I). The proposed method was applied to the determination of silver in waste water and zinc alloy samples with satisfactory results.

Fluorophotometric determinations of cobalt(II) and hydrogen peroxide were investigated by using the fluorescence reaction between fluorescein-hydrazide (fl-NHNH2), and/or hydrogen peroxide, cobalt(II), respectively. The calibration graphs were liner in the range of 0–6.0 ng cobalt(II) and 0–1000 ng hydrogen peroxide per 10 ml at an emission wavelength (Em) of 530 nm with an exicitation wavelength (Ex) of 508 nm, respectively. These proposed methods were selective and simple, and the effect of foreign ions was negligible in comparison with conventional reported methods such as nitroso R,4-(2-pyridylazo)resorcinol(PAR), alizarin, pyridine-2-aldehyde-2-pyridinehydrazone, stilbazo-cobalt(II), etc.

This paper presents a method of determination of aluminium in tree samples (wood, leaves, roots) based on the cathodic adsorptive stripping voltammetry. Al(III) complexed with alizarin S was determined by ASV method using a hanging mercury drop electrode. Optimal conditions were found to be: accumulation time 30–90 s, accumulation potential − 0.70 V versus SCE, supporting electrolyte 0.1 M ammonia-ammonium chloride buffer at pH 8.2 and concentration of alizarin 1 × 10−5 M. The response of the system, a linear current-concentration relationship was observed up to 8 × 10−6 M. The developed method has been tested by analysing international reference materials (BCR 62 Olive leaves and BCR 101 spruce needles).

Alizarin, Alizarin S, quinizarin and quinalizarin have been compared as acid-base indicators with Bromocresol Green and Methyl Orange as reference indicators. The chromaticity co-ordinates, complementary chromaticity co-ordinates, p K a values, transition pH-range, pH of maximum colour change, optimum concentration for titrations and the quality of colour change were determined. The results show all four to be good indicators with a colour change quality similar to that of Bromocresol Green.

The complexation reaction between Alizarin complexan ([3-N,N-di(carboxymethyl)aminomethyl]-1,2-dihydroxyanthraquinone; H(4)L) and zinc(II), nickel(II), lead(II), cobalt(II) and copper(II) has been studied by a spectrophotometric method. All these metal ions form 1:1 complexes with HL; 2:1 metal:ligand complex were found only for Pb(II) and Cu(II). The stability constants are (ionic strength I = 0.1, 20 degrees C): Zn(2+) + HL(3-) right harpoon over left harpoon ZnHL(-) log K +/- 3sigma(log K) = 12.19 +/- 0.09 (I = 0.5) Ni(2+) + HL(3-) right harpoon over left harpoon NiHL(-) log K +/- 3sigma(log K) = 12.23 +/- 0.21 Pb(2+) + HL(3-) right harpoon over left harpoon PbHL(-) log K +/- 3sigma(log K) = 11.69 +/- 0.06 PbHL(-) + Pb(2+) right harpoon over left harpoon Pb(2)L + H(+) log K approximately -0.8 Co(2+) + HL(3-) right harpoon over left harpoon CoHL(-) log K 3sigma(log K) = 12.25 + 0.13 Cu(2+) + HL(3-) right harpoon over left harpoon CuHL(-) log K 3sigma(log K) = 14.75 +/- 0.07 Cu(2+) + CuHL(-) right harpoon over left harpoon Cu(2)L + H(+) log K approximately 3.5 The solubility and stability of both the reagent and the complexes and the closenes of the values of the stability constants make this reagent suitable for the photometric detection of several metal ions in the eluate from an ion-exchange column.

The characteristics of the mixed-ligand titanium(IV)-fluoride-alizarin complex, including the optimum conditions of formation and extraction into methyl isobutyl ketone, are described. A simple and sensitive procedure for spectrophotometric determination of titanium has been developed. At pH 9.5–10.3 titanium reacts with alizarin in the presence of fluoride to form a red-violet complex that is completely extractable into methyl isobutyl ketone, and has its absorption maximum at 513 nm. The molar absorptivity at 513 nm is 7.0 × 104l.mole−1.cm−1. Beer's law is obeyed up to 22 μg of titanium in 30 ml of solution. The method has been used for the determination of titanium in an oxide mixture and aluminium alloy samples.

A critical examination has been made at the 0·01 M level of the performance of various indicators for the titration of calcium in the presence or absence of magnesium with EDTA. The bis -azo dye Acid Alizarin Black SN is recommended for the titration of calcium in pure solution, and for solutions where the magnesium/calcium ratio does not exceed 1:12. For higher ratios, quantitative recovery of calcium and satisfactory end-points are only obtained when Calcon is used as indicator. The range of application of Acid Alizarin Black SN can be extended if 1:2-diamino-propane- n:n' -tetra-acetic acid is used in place of EDTA as titrant.

Indicators and electrode systems for the titration of weak acids in 1,1,3,3-tetramethylguanidine as solvent have been investigated. A glass electrode coupled with a silver-silver bromide reference is found to give the most reliable results. Alizarin yellow and azo violet give results in agreement with potentiometric end-point values. A large potassium ion effect is observed in this solvent. Attempts to differentiate several pairs of acids were unsuccessful, because the solvent showed a strong leveling effect.

This method was developed for the determination of zirconium in plutonium-uranium-‘fissium’ alloys. A sample of the alloy containing 40–100 μg of zirconium in 10 N nitric acid is separated from plutonium and from some of the palladium by anion exchange. The effluent is analyzed for plutonium since more than 60 μg will interfere. The ruthenium is removed by fuming with perchloric acid. The uranium and molybdenum do not interfere in reasonable quantities as they exist in this alloy. The alizarin red- S lake is formed in 0–1 N nitric acid, and its absorbancy is measured by means of the Beckman Model B spectrophotometer at 520 mμ. The color is stable for several hours and reproducible within 3–5 per cent of the amount present. The interference of the alloying constituents and reagents are given. The time required for duplicate analyses is about 3½, and the equipment and techniques used are standard.

Optimum conditions are established for the formation of the zirconium-alizarin S lake. Trichloracetic acid exerts a stabilisation action over the lake in hydrochloric acid solutions, enabling extraction of the lake with butanol over a large range of pH. The butanol lake solutions are stable almost indefinitely. The distribution constant has been determined, and the 1:1 composition of the complex in butanol proved by the continuous variations, the slope ratio and the molar ratio methods. Lambert-Beer's law is obeyed up to at least 11 μg of zirconium. The influence of elements commonly associated with zirconium in its natural compounds is less in butanol than in the case of determinations in an aqueous medium.

The polarographic determination of aluminium as its complex with alizarin in the pH range 9.2-10.1, with the cathode ray polarograph, is described. A solvent extraction procedure is used to eliminate interferences from many other metals.

A comparison is made of a number of direct complexometric titrations previously published for the determination of yttrium and the lanthanons. Working and ‘optimum’ pH ranges are obtained for what are considered to be the best indicators. Alizarin Red S screened with Methylene Blue, Erioehrome Black T, Copper-Naphthyl Azoxine and Xylenol Orange. The precision and accuracy of the selected methods are determined by carrying out replicate titrations on standard solutions of ceriumIII, yttrium and ytterbium. The results, together with additional observations made on the behaviour of indicators in the different methods, suggest that Xylenol Orange at pH 5.8 to 6.4 is most satisfactory and convenient for direct titrations.

A study has been made of the comparative suitability of the ceriumIII, lanthanum and praseodymium chelates of alizarin complexan as reagents for the spectrophotometric determination of microgram amounts of fluoride. The ceriumIII reagent is most sensitive at pH v v , but the most sensitive means of determination is to use the lanthanum reagent in aqueous solution at pH 5.2 with measurement at 281 mμ. This procedure is 200% more sensitive than the standard method at 620 mμ.

The complex of lanthanum with alizarin Red S in acetate medium has been studied spectrophotometrically since it appears to be promising for the determination of the chemical yield in radioactivation analysis of rare earth elements. At pH 4.6 (acetate buffer) the molecular ratio lanthanum: alizarin Red S is 1:2.

The optimum pH range of the ceriumIII-alizarin complexanate method for fluoride has been established as pH 5.0–5.2 at which value the method may be applied over a wide concentration range from 5 μg of fluoride ion (0.1 ppm) to 1.6 mg (>160 ppm) using a conventional spectrophotometer. The nature of the changes produced in the colour system by variation of pH are briefly discussed and the interference of 23 selected cations and 3 common anions has been examined. Practically all of the serious cationic interference can be overcome by the simple addition of a masking agent but, in a few cases, a preliminary extraction with 8-hydroxyquinoline and chloroform is required.

The behaviour of alizarin-9-imine as an indicator in acetonitrile and pyridine media has been studied. The protonation constant in acetonitrile, K(I) = a(Hi) + a(H(+)) . a(I) = 10(-3.4), has been determined. Organic acids, amino-acids, and aliphatic and aromatic amines have been titrated with errors below 2%.

The polarographic behaviour of 9,10-anthraquinone ( I ) and some of its dihydroxy derivatives, such as alizarin ( II ), quinizarin ( III ) and chrisazin ( IV ) has been studied in the presence of proton donors of HA and HB + type. After optimization of conditions for reversible reduction of the anthraquinones, various polarographic techniques were used for the determination of anthraquinones in chloroform. In the dc method, the relative standard deviation for the determination of 1m M concentrations was about 1.5%. In the ac method, the detection limit was 0.1 μg/ml and the relative standard deviation for determination at the 0.2 μg/ml level was 2%. The proposed methods are usable for the simultaneous determination of I and II , II and III , II and IV , and have been applied to the determination of 9,10-anthraquinone in papers and black liquors.

A simple and sensitive extractive spectrophotometric determination of fluoride with the cerium(III)-alizarin complexan chelate has been investigated. The fluoro chelate formed is extracted into n-pentanol containing triethylamine. It is possible to achieve under selected conditions a selective extraction of the cerium(III)alizarin complexan-fluoride chelate. The stability of the chelate, the effect of temperature and the low absorbance of the blank are discussed. It is found that it is necessary to add a pH 9 buffer before the extraction. Procedures are given for the determination of 0.1-1 mug of fluoride in a 4-ml sample and 5-25 mug of fluoride in a 90-ml sample.

Alizarin Red S, Pyrocatechol Violet and Xylenol Orange are shown to be effective adsorption indicators for the titrations of hexacyanoferrate(II) and oxalate with Thorium(IV) solution. The action of the indicators can be explained by the theory of surface compound formation.

In order to decide whether Alizarin Fluorine Blue (alizarin complexan, 3-amino-methylalizarin-N,N-diacetic acid) is a suitable reagent for the spectrophotometric determination of aluminium, values of the stability constants for some reactions of this reagent with aluminium(III) and iron(III) have been determined spectrophotometrically in a medium containing 20 % dioxan and 80 % water at ionic strength 0.1. The values of the constants that were determined are log K(Al)(AlHL) = 14.3, log K(2Al)(Al2L) = 25.3 and log K(Fe)(FeHL) = 19.6. These results were employed in the design of a method for the spectrophotometric determination of aluminium in the presence of iron and titanium. The Sandell sensitivity is 0.01 mug/cm(2) and the coefficient of variation for 34 determinations was 0.9 %.