Evaluation of the quality of colour changes of complexometric indicators in the titration of copper (II) with EDTA by tristimulus colorimetry

The quality of colour changes of the indicators hematoxylin, 4(2-pyridylazo)resorcinol (PAR), xylenol orange, pyrocatechol violet, chromazurolS and eriochrome cyanineR in the complexometric titration of copper(II) with ethylenediaminetetraacetic acid (EDTA) were studied with the help of tristimulus colorimetry, utilising a comparative study of the parameters SCD (specific colour discrimination), CIE La^*b^* 1976 and LABHNU 1977. Hematoxylin was found to be the best indicator among those studied. A screened indicator, viz. PAR + malachite green (52), was developed to enhance the quality of colour transition at the end-point and the accuracy of the titrimetric determination.     

Screened indicators in anhydrous acetic acid medium: Chromatic evaluation of their transitions

Three efficient indicators consisting of Malachite Green and a screening dye for use in anhydrous acetic acid media have been designed by use of complementary tristimulus data. The transition quality can be evaluated by plotting the relative greyness of the indicator against free perchloric acid concentration. Several bases have been successfully determined titrimetrically with use of these indicators.     

Colour changes of chemical indicators-III: colour specification and its accuracy

The systematic deviations involved in methods for computation of chromaticity co-ordinates have been studied for the specification of indicator colour changes. The weighted ordinale method (Deltalambda = 10 nm) has proved to be satisfactory for evaluation both of C.I.E. and complementary co-ordinates. The C.I.E. colour specification should be included among basic data about chemical indicators.     

Evaluation of colour changes of indicators: the supercolor program

SUPERCOLOR is a microcomputer program for the computation of chromaticity parameters from spectrophotometric data. The program is written in BASIC for the HP-200 computer series and it allows the characterization of indicator colour transitions in the standard CIE chromaticity systems. The numerical results for up to 12 indicators can be compared in the same plot for each chromatic system, so that colour changes are easily compared. The pK_a values, pH transition ranges, pH of maximum colour change, SCD values and optimum indicator concentration for visual titrations can be calculated, as well as the colour coordinates.SUPERCOLOR also provides subroutines for computation of screened indicators and simulation of the colour changes of these indicators or other indicator/inert dyes mixtures. The results for some common indicators are presented.     

Electrophoretic determination of pK-values of indicators and their relation to colour changes

The pK-values of Xylenol Orange, Pyrocatechol Violet, Thorin and Alizarin Complexone were determined electrophoretically on the basis of the Kiso equation. The colour changes of Xylenol Orange and Alizarin Complexone were found to take place at slightly higher pH values than the electrophoretically determined pK-values. The Kiso-equation for determination of the pK values by electrophoresis yielded reproducible results and the method is useful for complicated substances because the procedure is simple, the equipment inexpensive and only microamounts of the substances are needed.     

Specification of colour changes of metallochromic indicators in the titration of bismuth with EDTA

The quality of the colour changes at the end-point in the complexometric titration of bismuth(III) with EDTA, using the indicators Hemotoxylin, PAN [1-(2-Pyridylazo)-Naphthol-2], PAR [4-(2-Pyridylazo)-Resorcinol], Xylenol Orange and Thoran is studied by means of the CIE 1931 trichromatic system, using specific colour discrimination (SCD) and colour difference (DeltaE*). The indicators are arranged in order of colour change quality. Of the indicators studied, Hemotoxylin is recommended as the most suitable for this titration.     

Benchmarking and quality management indicators in three medical laboratories

The aim of this study was to calculate various annual quality management indicators and implement them as a management tool in laboratories. The study was performed in three laboratories over five years, from 2000 to 2004. These laboratories are part of the XHUP (Public Hospital Network in Catalonia). We collected 20 annual items over five years and calculated 20 annual indicators. The Laboratory Manual Index Program from the College of American Pathologists was used as a reference. We also compared an analytical quality indicator versus productivity and calculated annual budget laboratory deviation. The information obtained from these indicators provides laboratories with a useful benchmarking tool to determine the results of management change and understand the real situation in laboratories. We found a lack of standardisation in management data. A future area of work could involve unifying some of the different characteristics. Presented at the Conference Quality in the Spotlight, March 2006, Antwerp, Belgium.     

Salt effect on the dissociation constant of acid-base indicators

The effect of the ionic environment on the dissociation constant of acid-base indicators is accounted for by using the specific interaction theory (SIT) of Broensted, Scatchard, and Guggenheim. It is shown that the SIT may be applied to evaluate the activity coefficients of organic ions, regardless of their size and structure, if suitable modifications are introduced.     

Effect of the solvent on the equilibria of acid-base indicators in aprotic and amphiprotic solvents

The dissociation constants of a series of indicators inN,N-dimethylformamide medium have been determined, and compared with those for the indicators in other aprotic solvents (dimethylsulphoxide and acetonitrile) and in some amphiprotic solvents (water, methanol, ethanol, propan-2-ol and tertbutanol). The effect of the solvent characteristics on the pK values have been evaluated, and the pK + p _ws ^t (H⁺) values shown to be linearly correlated with the Dimroth and ReichardtE _T ^N and acceptor number solvatochromic parameters.     

Solvent polarity indicators: Extraction of some coumarin indicator dyes

Study of the extraction of ten different coumarins (unsubstituted, 6-methyl-, 7-methyl-, 4-hydroxy-, 7-hydroxy-, 7-hydroxy-4-methyl-, 7-methoxy-, 7-amino-4-methyl-, 7-diethyl-amino-4-methyl-, and 3-carboxy-) with nine organic solvents shows that the percentage extraction is generally high. Cyclohexanone and heptane were found to be, respectively, the most and least effective extracting solvents for the compounds under study. The results are discussed in terms of the effect of different solvent polarity parameters on the extraction process.     

ICP-OES同时测定矿泉水界限指标中的4种元素

矿泉水界限指标中的四种矿物质元素锌、锂、锶、偏硅酸(以H₂SiO₃计),国标方法需每种元素分别测定且步骤繁琐,本实验采用ICP-OES对矿泉水中这4种元素的含量进行同时测定,四种元素的检出限在0.01~0.10 mg/L,对市售矿泉水进行了检测,加标回收率在83 %~100 %,相对标准偏差为0.31 %~1.96 %,方法简便省时,精密度和准确度较高,可以作为一种鉴别矿泉水品质的方法。     

Calculations of D‐wave bound states and resonance states of the screened helium atom using correlated exponential wave functions

We have investigated the effects of screened Coulomb (Yukawa) potentials on the bound ^1,3D states and the doubly excited ^1,3 D^e resonance states of helium atom using highly correlated exponential basis functions. The Density of resonance states are calculated using stabilization method. Highly correlated exponential basis functions are used to consider the correlation effect between the charged particles. A total of 18 resonances (nine each for ¹ D^e and ³ D^e states) below the n = 2 He ⁺ threshold has been calculated. For each spin states, this includes four members in the 2pnp series, three members in the 2snd series, and two members in 2pnf series. The resonance energies and widths for various screening parameters ranging from infinity to a small value for these ^1,3 D^e resonance states are reported along with the bound‐excited 1s3d ^1,3 D state energies. Overall behavior of the spectral profile of 1s3d ¹D state of helium atom due to electron‐electron and electron‐nucleus screening are also presented. Accurate resonance energies and widths are also reported for He in vacuum. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Colour specification of pyridine-2-aldehyde and 6-methylpyridine-2-aldehyde p-nitrophenylhydrazones as indicators for pH determination

The physicochemical properties, chromaticity co-ordinates and chromatic parameters for pyridine-2-aldehyde p-nitrophenylhydrazone and 6-methylpyridine-2-aldehyde p-nitrophenylhydrazone (proposed as new indicators for calorimetric pH measurements) are reported. The sensitivity and rapidity of colour change have been evaluated in terms of specific colour discrimination (SCD), pH of maximum colour change and half band-width of change of SCD (in terms of pH). The chromatic separations calculated from the co-ordinates obtained by the CIE 1976 recommendations (CIELUV or CIELAB) and the LABHNU 1977 colour space are compared and correlated with the standard deviation of colour matching.     

Isotopes in groundwater as indicators of climate changes

Isotopes of the water molecule (δ¹⁸O and δ²H) are a well-used tool for investigating groundwater origin and history (i.e. tracing the recharge conditions over time, processes occurring during infiltration of rainwater towards aquifers and those involved in the water-rock interaction, and mixing of different waters).This review covers several large European aquifers (Portugal, France, UK, Switzerland, Germany, Hungary, and Poland), which were investigated in terms of their recharge conditions, and the story of the groundwater at a large scale, involving recent, Holocene and Pleistocene components and their eventual mixing.     

A comparative study of the behaviour of Crystal Violet,alizarin-9-imine and quinalizarin-9-imine as indicators in anhydrous acetic acid medium

A comparative study has been made of the behaviour of alzarin-9-imine, quinalizarin-9-imine and the widely used Crystal Violet as indicators in anhydrous acetic acid medium. The protonation constants of quinalizarin-9-imine, and the properties required by a base if it is to be titratable in acetic acid medium with use of the indicators studied, the chromaticity co-ordinates, optimal concentration for titration and the quality of the colour changes have been determined. The results obtained show Crystal Violet and alizarin-9-imine to be very good indicators in acetic acid medium but alizarin-9-imine gives better end-point location. Quinalizarin-9-imine is also a good indicator but exhibits poorer colour change quality than the other two.     

Properties of hydrogen molecular ion with static screened coulomb and exponential cosine screened coulomb potentials

We have investigated the properties of hydrogen molecular ion (H) interacting with screened Coulomb potentials. Two types of potentials have been considered, namely, static screened Coulomb potential and exponential cosine‐screened Coulomb potential. Simulating the localized motion of the nuclei by using high powers of the internuclear coordinate in the generalized Hylleraas‐type wave function we have been able to obtain reasonably accurate binding energies for 1¹S(J = 0, ν = 0) and 2¹S(J = 0, ν = 1) states for various values of the screening parameter within the frame work of Ritz variational method. Borromean bindings are found to exist in the ion for a wide range of the screening parameter. Furthermore, expectation values for various operators and cusp condition have been calculated. Results for the unscreened case are in nice agreement with some of the accurate results available in the literature. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Synthesis and characterization of fluorescent starch using fluorescein as fluorophore: potential polymeric temperature/pH indicators

A convenient method for attaching fluorescein (via its epoxy derivate) to natural starch and its temperature/pH‐sensitive qualities of fluorescence were investigated. 3‐epoxypropoxy fluorescein (EPF) was first synthesized through the reaction between fluorescein and epichlorohydrin, and starch‐bearing fluorescein (ST‐EPF) was prepared via ring‐opening reaction with EPF in dimethyl sulfoxide (DMSO) solution, in the presence of NaH as a catalyst. Both of them were characterized by the methods of ¹H NMR, MS, IR, XRD, UV–Vis, and luminescence spectra, respectively. The chemiluminescent and photophysical behaviors of the dye fluorescein derivative and the polymer‐containing fluorescein were studied. The results indicated that ST‐EPF could still provide temperature and pH sensitivity similar to that of fluorescein and could achieve better long‐term stability and fast equilibrium response. ST‐EPF had an excellent linear response between relative fluorescence intensity and temperature in the range of 0–60°C and a nonlinear relationship between relative fluorescence intensity and pH in the wide range of 0.0–12.0, and so it has promise as an optical transducer for temperature and pH value determinations. Copyright © 2008 John Wiley & Sons, Ltd.     

Structure of cholesteric gels and their electrically induced light scattering and colour changes

Abstract

Networks with a helical structure containing large amounts of low mass liquid crystal molecules (gels) were produced by photopolymerization of a nematic diacrylate in the presence of low mass cholesteric mixtures. Prior to polymerization the systems selectively reflected a band of circularly polarized light. Upon polymerization, the gels obtained gave rise to two reflection peaks which were subsequently associated with polymer rich and polymer poor phases. At high network concentrations (>40 per cent w/w) one of the peaks did not appear, indicating that the behaviour of the molecules which were not chemically attached to the network was totally dominated by the network. From the gap required for the suppression of the rotation of the director, it was estimated that the molecules, which were not crosslinked, were confined in layers thinner than 85 nm. The gels were very transparent and did not give rise to excess light scattering as compared with the monomeric state. Upon application of an electric field, colour changes as well as light scattering were induced. These efffects were found to be highly dependent on the state of the polarization of the light as well as the kind of field applied. The response times were very short and they depended strongly on the structure of the network.     

Studies on adsorption indicators : Titration of iodide in presence of chloride. mechanism of the colour changes during argentometric titrations with congo red as adsorption indicator

Congo red is a suitable indicator for the titration of iodide in presence of chloride with silver solution at pH 5–5.5. The behaviour of congo red as an adsorption indicator is described in detail. The silver compound of congo red has been isolated and its properties investigated.     

Suitability of sterin dose indicators for control of certain food irradiation processes

Sterin indicator, a new label dosimeter was evaluated for reliability and suitability as a device for discriminating and monitoring radiation treatment. Two versions, Sterin-125 and Sterin-300 were irradiated with gamma rays at dose ranges of 75–175 Gy and 200–400 Gy respectively. The irradiated samples were evaluated subjectively using Multiple Comparison Difference technique and their stability was tested under dark and differing light and temperature conditions. The results showed that these Sterin labels are generally reliable and useful but are affected by doses lower than designated threshold and by extended exposure to light sources.