Search

In this study, the fibrous mesoporous silica F-SiO2 was functionalized with 3-aminopropyltriethoxysilane (APTES). The reversible thermochromic composites of fibrous mesoporous silica (F-SiO2) and amino group-modified fibrous mesoporous silica (F-SiO2-NH2) microspheres loaded with cresol red-boric acid (CR-BA) were termed as S2 (F-SiO2/CR-BA) and SN2 (F-SiO2-NH2/CR-BA), respectively. The materials obtained were characterized by infrared spectroscopy, transmission electron microscopy, scanning and transmission electron microscopy, differential scanning calorimetry, and thermogravimetric analysis. The fibrous morphology of this rigid carrier was maintained after loading with the CR-BA composite system. Owing to the APTES modification, the F-SiO2-NH2/CR-BA composites underwent more severe color changes than the F-SiO2/CR-BA composites. In addition, the F-SiO2-NH2/CR-BA composites can recover the original color in only 210 s, illustrating excellent reversibility.

Aims: To develop simple, sensitive and direct spectrophotometric methods for the estimation of widely prescribed antidiabetic hypoglycemic agent Glimepiride in pure and pharmaceutical dosage form. Place and duration of study: Research Centre of Taywade Group of Institution Koradi, Nagpur affiliated to Rashtrasant Tukadoji Maharaj Nagpur University Nagpur between June 2020 and March 2021. Methodology: Two spectrophotometric methods were developed based on ion-pair formation of drug with Cresol Red dye (Method A) and Bromophenol Blue dye (Method B) in methanol and chloroform. The possible reaction mechanism was proposed with evaluation of statistical parameters. The methods were validated for its application to determine Glimepiride in bulk as well as in pharmaceutical formulations Results: The Beer's law was found linear in the range 10 - 60 µgml-1 at 450 nm for method A and 2 - 20 µgml-1 at 578 nm for method B, respectively. The linear regression equation obtained by applying least square regression analysis for Glimepiride were found to be Absorbance = 0.0136 x Concentration in µgml-1 + 0.028; R2 = 0.9965 for method A and Absorbance = 0.0428x Concentration in µgml-1 +0.0722; R2 = 0.9949 for method B. The Sandell's sensitivity was found to be 0.0696 and 0.0177 for method A and B respectively. The apparent molar absorptivity calculated to be for both methods were 6.6724 x103 and 2.0999 x104 l mol-1 cm-1. Conclusion: Two direct spectrophotometric methods for determination of Glimepiride have been developed successfully and validated for sensitivity, accuracy, precision, repeatability and robustness as per ICH guidelines. The developed methods are suitable for the routine estimation of Glimepiride in pure and dosage form.

Aims and Objectives: To develop simple, sensitive and direct spectrophotometric methods for the estimation of widely prescribed antidiabetic hypoglycemic agent Glimepiride in pure and pharmaceutical dosage form. Application of spectrophotometric technique for development of methods. Optimization of reaction parameters and spectral characteristics for developed methods. To propose possible reaction mechanism for developed methods. Application of the developed methods for quantification of the drug in formulations. Validation of the developed method as per ICH guidelines. Methodology: Two spectrophotometric methods were developed based on ion-pair formation of drug with Cresol Red dye (Method A) and Bromophenol Blue dye (Method B) in methanol and chloroform. The possible reaction mechanism was proposed with evaluation of statistical parameters. The methods were validated for its application to determine Glimepiride in bulk as well as in pharmaceutical formulations Results: The Beer's law was found linear in the range 10 - 60 µgml-1 at 450 nm for method and 2 - 20 µgml-1 at 578 nm for method B, respectively. The linear regression equation obtained by applying least square regression analysis for glimepiride were found to be Absorbance = 0.0136 x Concentration in µgml-1 + 0.028; R2 = 0.9965 for method A and Absorbance = 0.0428 x Concentration in µgml-1 + 0.0722; R2 = 0.9949 for method B. The Sandell's sensitivity was found to be 0.0696 and 0.0177 for method A and B respectively. The apparent molar absorptivity calculated to be for both methods were 6.6724 x103 and 2.0999 x104 l mol-1 cm-1. Conclusion: Two direct spectrophotometric methods for determination of Glimepiride have been developed successfully and validated for sensitivity, accuracy, precision, repeatability and robustness as per ICH guidelines. The developed methods are suitable for the routine estimation of Glimepiride in pure and dosage form. The developed methods can act as a tool for quality control of drug in analytical laboratories.

Two accurate spectrophotometric methods described for the estimation of carbamazepine (CBZ) in both pharmaceutical and pure form. These methodologies are attached to the bromination of CBZ by bromine formed in instantly from the bromate-bromide reaction. The general procedure includes the additional of a known amount of bromate-bromide reagent in an acidic mediocre to CBZ. After the reaction is integrated, the unreacted bromine was reacted with a steady amount of methylene blue, and the absorbance was measured at 665 nm (method A) or, cresol red could be used for the reaction and the absorbance moderated at 517 nm (method B). Beer’s law was submitted from 0.45 to 15.00 μg/mL CBZ with a molar absorptivity of 4.93 × 103 L/mol.cm for method A and from 0.50 to 12.00 μg/mL CBZ with a molar absorptivity of 1.37 × 104 L/mol.cm for method B. The proposed methods were effective for the determination of CBZ in tablets with great precision and accuracy.

This study investigated the polymer film composite of polyvinyl alcohol (PVA), trichlorethylene (TCE) and cresol red (CR) dye irradiated with gamma (γ) rays for potential application as radiation dosimetry. The film was prepared via the solvent-casting method with varying concentrations of TCE. Film samples were exposed to radiation from a γ-rays radiation source of 60Cobalt isotope. Color changes before and after γ-rays irradiation were observed, and the optical properties of the polymer films were investigated by spectrophotometry. Results show that increasing the radiation dose physically changed the color of the polymer film, from purple (pH &gt, 8.8) without radiation (0 kGy) to yellow (almost transparent) (2.8 &lt, pH &lt, 7.2) at the highest dose (12 kGy). The concentration of acid formed due to irradiation increased with the increase in irradiation doses and at higher TCE content. The critical doses of PVA-TCE composites decreased linearly with the increase of TCE composition, facilitating an easy calibration process. The dose response at 438 nm increased exponentially with increasing radiation dose, but showed an opposite trend at the 575 nm band. An increase in the TCA concentration indicated a decrease in the absorption edge and an increase in activation energy, but both decreased for all TCE concentrations at higher doses. The energy gap for the direct and the indirect transitions decreased with increasing TCE concentration and γ-rays radiation dose. The results of this study demonstrated the potential application of PVA-TCE-CR polymer film as γ-rays irradiation dosimetry in a useful dose range of 0–12 kGy.

In this study, thermosensitive luminous fibers (TLFs) were prepared by wet spinning, using polyacrylonitrile as the filament material and rare-earth long-afterglow luminescent materials as the optical source. Reversible thermochromic cresol red-boric acid (CB) pigment in the TFLs served as the luminescence conversion agent. The reflectivity curves and fluorescence spectra were recorded at 25 and 65 °C to investigate the thermosensitive characteristics of the TLFs. The results demonstrated that CB pigment functioned as a luminescent conversion agent that could convert the luminescence of rare-earth luminescent materials depending on the temperature. The luminescence of the TLFs can be converted from blue to fuchsia upon changing their temperature due to the structural transformation of the CB dye. The thermosensitivity can also be verified by observing the TLFs in water at 65 °C with the naked eye.

A series of highly efficient, solid-state sensors for direct colorimetric detection of gaseous CO2 and SO2 is described. The basic components of the sensors are a CO2 and SO2-responsive, tertiary amino alcohol, such as triethanolamine, and a pH-indicator dye, e.g. cresol red, immobilized on a porous γ-aluminum oxide support. These sensors show distinct visual responses to low levels of CO2 and SO2 present in air. A structure–performance relationship was also established for these sensors. To increase the shelf-life, tertiary amino alcohols were covalently attached to the porous alumina support. These porous alumina-supported tertiary amino alcohols also offer potential for use as adsorbents for acidic gases such as CO2 and SO2 with the ability to selectively release these under different conditions, allowing easy separation from a gas stream.

Impurities in sulphonephthalein indicator salts can result in significant errors in seawater pH determinations. To ensure suitable measurement accuracy and intercomparability on a global basis, impurities must be removed from all indicators used for oceanographic CO 2 system analyses. Previous work has described an effective HPLC (high-performance liquid chromatography) procedure for purification of meta-cresol purple, but the technique is labor-intensive, with each HPLC run producing only a small batch of purified indicator. This work describes the use of flash chromatography to more efficiently produce large batches of purified meta-cresol purple (mCP) and cresol red (CR), the preferred indicators for direct water column determinations of seawater pH. Several batches of unrefined mCP and CR of independent origin were prepared by flash chromatography. Indicator purity was then assessed in two ways: by (a) HPLC verification and (b) pH measurements of highly buffered solutions. HPLC chromatograms of the various flash-prepared mCPs indicated that the process did not always result in a completely pure product. In terms of performance, however – i.e., pH measurements of highly buffered solutions – no differences were observed between an HPLC-purified reference mCP and the flash-purified mCPs. HPLC examination of the flash-purified CRs indicated that every product was free of detectable impurities. No differences were seen in comparative pH measurements made with the purified CRs. The flash chromatography procedures outlined in this work are suitable for producing bulk quantities of mCP and CR for use in high-precision spectrophotometric pH measurements in seawater.

A simple, accurate, and rapid extraction spectrophotometric procedure has been developed for the determination of some phenothiazine drugs such as chlorpromazine hydrochloride (CPH) and trifluoperazine dihydrochloride (TFPH) in pure form and their pharmaceutical preparations. The procedures are based on the reaction between the examined drugs (CPH and TFPH) and Alizarin Red S (AR), Bromocresol Purple (BCP), Chlorophenol Red (CPR) and Cresol Red (CR) producing ion-pair complexes which can be measured at the optimum wavelengths. The optimizations of the reaction conditions were investigated. Beer’s law is obeyed in the concentration ranges 1.77–96 μg ml −1 . The molar absorptivity and Sandell sensitivity are also calculated. The correlation coefficient for both drugs was ⩾0.9995 ( n = 5) with a relative standard deviation (R.S.D.) ⩽0.38. The methods are successfully applied to determine CPH and TFPH in pharmaceutical formulations.

Analysis of compounds having biological activity is very important nowadays. This work shows the possibility of using the visualizing agents such as janus blue, methylene violet, gentian violet, methyl green, cresol red, rodamine B, malachite green, methylene blue, eosin yellowish, and metanil yellow to visualize the selected quinolones and fluoroquinolones after their separation using the TLC method. The visualizing effects were estimated after dipping the chromatographic plates in solutions of the mentioned above visualizing agents and drying at room temperature, at 120°C, or was estimated directly after dipping in solutions of the visualizing agents. The detection limit of quinolones and fluoroquinolones investigated in the conditions of visualization that gave the best visualizing effects was determined. The detection limits for cinoxacin, pipemidic acid, ofloxacin, and pefloxacin were: 0.1 µg, 0.1 µg, 0.5 µg, and 0.75 µg, respectively.

Two simple and sensitive extractive spectrophotometric methods have been described for the analysis of clarithromycin in pure form and in pharmaceutical formulations. The methods involved formation of yellow colored chloroform extractable ion-association complexes of clarithromycin with bromothymol blue (BTB) and cresol red (CR) in buffered aqueous solution at pH 4. The extracted complexes showed maximum absorbance at 410 and 415 nm for BTB and CR, respectively. Beer's law is obeyed in the concentration ranges 0.1-20 μg mL"' and 2.0-20 μg mL"' of clarithromycin with molar absorptivity of 2.01 x 10 4 and 4.378 x 10 3 for BTB and CR, respectively. The composition ratio of the ion-association complex was clarithromycin: BTB and CR = 1:1 as established by Job's method. The methods have been applied to the determination of drug in commercial formulations. The results of analysis were validated statistically and through recovery studies.

Two different sulfonephthalein indicators, cresol red (CR) with a pKa of approximately 8.3 and bromothymol blue (BTB) with pKa of approximately 7.4, were tested for an analysis of freshwater over a broad range of pH and total alkalinity values. Measurements from an autonomous sensor system using a 1 cm optical path length were compared to those using a 10 cm path length on a benchtop spectrophotometer. The indicator pH perturbation was quantified with a thermodynamic model and nonlinear least-squares analysis. The laboratory study found that the perturbation-corrected pH differed between the 1 cm (large indicator perturbation) and 10 cm (small indicator perturbation) optical path length measurements from -0.017 to +0.15 with a median of +0.0041 pH units for CR and from -0.015 to +0.026 with a median of -0.0008 pH units for BTB. Precision was +0.0005-0.013 and +0.0001-0.0027 pH units for the 1 and 10-cm-path-length measurements, respectively. The autonomous sensor was deployed for 14 days in a local creek. Simultaneous glass pH electrode measurements had a large negative and drifting offset (-0.15 to -0.40 pH units) compared to the indicator-based measurements. This study is the first in situ comparison between potentiometric and spectrophotometric pH methods in a freshwater system.

Two simple, rapid and sensitive extractive spectrophotometric methods have been developed for the assay ofcinnarizine (CNR) in pure and pharmaceutical formulations. The methods are based on the formation of chloroform soluble ion-association complexes of CNR with thymol blue (TB) and with cresol red (CR) in NaOAc-AcOH buffer of pH 3.6 for TB and in KCl-HCl buffer of pH 1.6 for CR with absorption maxima at 405 nm and at 403 run for TB and CR, respectively. Reaction conditions were optimized to obtain the maximum color intensity. The systems obeyed Beer's law in the range of 0.6-15.8 and 0.8-16.6 μg mL -1 for TB and CR, respectively. Various analytical parameters have been evaluated and the results have been validated by statistical data.

The white rot fungus (WRF) Pleurotus ostreatus produced manganese peroxidase (MnP) and manganese-independent peroxidase (MIP) activities during solid state fermentation of wheat straw, a natural lignocellulosic substrate. Most of the sulfonphthalein (SP) dyes were decolorized by MnP at pH 4.0. The higher K m for meta -cresol purple (40 μM) and lower K m for ortho -cresol red (26 μM) for MnP activities explained the preference for the position of methyl group at ortho than at meta on chromophore. Bromophenol blue decolorizing activity was higher at pH 3.5 and decreased as the concentration of Mn II was increased. SP-decolorizing activity was associated not only with MnP but also with MIP. Additional bromine group along with the methyl group on SP chromophores decreases the rate of decolorization. Bromination of sulfonphthalein chromophore makes them the poorer substrate for MnP. This is evident from the higher K m for bromocresol green (117 μM) when compared to bromocresol purple (36 μM) and bromophenol blue (78 μM). The order of preference for the SP dyes as substrate for the MnP-catalyzed decolorizing activity is phenol red > ortho -cresol red > meta -cresol purple > bromophenol red > bromocresol purple > bromophenol blue > bromocresol green and the order of preference for the SP dyes as substrate for the MIP-catalyzed decolorizing activity is bromocresol green > bromophenol blue > bromocresol purple > bromophenol red > meta -cresol purple > ortho -cresol red > phenol red. Inhibition of PR decolorizing activity by NaN 3 provided the evidence of decolorizing activity as an oxidative process.

The reaction between four pH indicators with a large pKa value and human serum albumin and its application to the determination of the serum albumin concentration were studied. In the reaction of Bromothymol Blue (BTB), Phenol Red, Cresol Red and Thymol Blue with serum albumin, although a change in the color shade did not occur, the absorbance of the reaction mixture decreased. Since this absorbance decrease was largest in the reaction of BTB(the molar absorbance decrease at pH 7.4 was 7.59×104 l mol−1 cm−1), which was sufficiently sensitive to measure the serum albumin concentration, the BTB color reagent at pH 7.4 was applied to its determination. The measurement values by the BTB method correlated with those by the dye-binding method using the Bromocresol Green method(r = 0.965, y = 1.21x−4.25, n = 90) and with those by a method using Bromocresol Purple(r = 0.953, y = 1.04x + 3.56, n = 90). The mean value of the BTB method (41.8 g/l) was higher than those of the Bromocresol Green method (38.1 g/l) and the Bromocresol Purple method(36.6 g/l). Since the reaction of BTB was carried out at pH 7.4, where serum protein does not precipitate, the addition of a detergent for preventing the precipitation of serum protein is not required. Therefore, the use of this color reagent contributes to decreasing water pollution by the detergent and acid used in the conventional methods.

Interaction of aqueous sulfonephthalein dyes, viz., phenol red, cresol red and cresol purple with alkyltrimethylammonium and alkylpyridinium halide surfactants in submicellar concentration ranges of the surfactants has been studied by UV–VIS spectroscopy. The spectral changes of the dyes observed on addition of the surfactants at concentrations far below critical micelle concentration (c.m.c.) indicate the formation of doubly deprotonated dye anions, which otherwise are formed only at much higher pH in the absence of the surfactant. The equilibrium constants for the interactions were determined. The deprotonation has been found to increase considerably with increase in hydrophobicity of the surfactant. It has been suggested that combined electrostatic–hydrophobic interaction increases acidity of the sulfonephthalein dyes in their closely packed dye–surfactant ion-pairs, formed at concentrations of surfactant far below c.m.c., causing deprotonation of the dye.

These films contain a mixture of two dyes namely, 2,6 dichloro phenol indophenol sodium salt (DCP) and cresol red (CR) indicator with different concentrations of chloral hydrate in poly (vinyl alcohol). The color of this film changes in two steps, i.e. from green to yellow and finally to red color. Due to irradiation, first the bleaching reaction for DCP takes place in the absorbed dose range up to about 17 kGy, followed by the transformation of CR to its acidic form due to the presence of chloral hydrate in the dose range up to 50 kGy. The response of these films can be modified by changing the chloral hydrate concentration and the ratio of the two dyes. As a result, these films can be used as a dosimeter in the two dose ranges. The dosimetric parameters, e.g. dose response, effect of relative humidity and temperature during irradiation on response as well as pre- and post-irradiation stability of these films are investigated.

This article reports on an evaluation of simple and inexpensive techniques for monitoring ‘off‐gassing’ from costume accessories, which may be made with cellulose nitrate (CN) and cellulose acetate (CA). As they degrade, CN and CA produce acidic emissions, which not only accelerate the decomposition process of the objects themselves but also promote the fading of dyes and the degradation of nearby objects. pH indicator dyes, namely cresol red, cresol purple, Congo red, methyl orange and cochineal, applied to paper, cotton tape and threads, were tested for their suitability and then for their usefulness in monitoring a collection of 15 hair accessories, one of CA, one of tortoiseshell and 13 of CN, and three fans. As well as a cresol type recommended by another author (Julia Fenn) for the lower pH emissions from CN, it is suggested that Congo red or methyl orange for the higher pH emissions from CA should be used simultaneously. It was noted that cotton tape and cotton thread exhibited better resi...

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

Phencyclidine forms ionic associates with Bromoxylenol Blue, Cresol Red, Eriochrome Cyanine R, Orange I, Amido Black 10B and Xylenol Blue. The associates are extractable with chloroform and the extracts exhibit absorption maxima in the region 407 - 625 nm. Maximum extraction of the associates was achieved after two to five minutes at pH 2 - 5. The method allows detection of PCP in aqueous solutions at concentrations of 0.32 mg.ml−1 to 1.94 mg.ml−1 and determination at 0.74 mg.ml−1 to 5.15 mg.ml−1.

The effect of root canal filling pastes containing calcium oxide resp. calcium hydroxide on the alkalinity of extracted human teeth was investigated using a colour indicator (cresol red). An aqueous suspension of calcium hydroxide (Pulpdent), which is normally used for temporary root canal filling, most consistently produced alkalinity. Removal of the smear layer following instrumentation of the root canal led to increased proportion of alkaline-positive spots in dentinal locations distant from the canal. A clearly smaller effect was found with a calcium salicylate cement (Sealapex) and an oil-paste (Gangraena Merz), both of which are available for definite root canal fillings. Following removal of the smear layer, these hard-setting preparations caused moderate alkalinity in dentin adjacent to the canal but no effect was observed in locations more distant from the canal. Neither at locations adjacent to nor distant from the root canal was alkalinity found when another calcium salicylate cement (Apexit) was used. Apparently the release of hydroxyl ions into root dentin from calcium hydroxide containing root canal filling materials is not solely influenced by the absolute amount of calcium hydroxide, but also depends on other ingredients which variably inhibit the release of these ions.

Ethylmorphine, morphine, codeine, cocaine, sernyl (PCP), LSD, 3-quinuclidinyl benzilate (BZ) provide, together with Cresol Red, ion-associates that are extractable by chloroform. The extracts of the ion-associates prove the absorption maxima in the interval 405 to 415 nm. Maximum extraction of the analytes of the ion-associates is reached after 4 minutes, taking readings of different pH values in 4 intervals of 1.5. This method allows detect of alkaloids and synthetical psychopharmaca row of quantities between 0.45 μg.ml−1 and 1.55 μg.ml−1 and to determine 1.05 μg.ml−1 to the amount 2.99 μg.ml−1 of the analytes in the aqueous solutions.

Two fan-shaped bile acid trimers have been synthesized via CuI-catalyzed azide–alkyne cycloaddition (CuAAC) ‘click chemistry’, and their extraction experiments of cresol red sodium (CR) and pyrene were investigated in the polar and non-polar solvents, respectively. The transmission electron microscopy (TEM) results showed that the homogenous hollow capsules formed with the diameter size range of 40–70 nm in a solution of water and acetone. Thus the amphiphilicity of fan-shaped bile acid trimers might be used as the promising candidate in biological and drug delivery applications.

The interaction of Cresol Red derivatives (Cresol Red (o-Cresolsulfonphthalein), Cresol Red-DA (3,3'-Bis [N,N-di (carboxymethyl) aminomethyl]-o-cresolsulfonphthalein) and Cresol Red-DA-Fe(III) (3,3'-Bis [N,N-di (carboxymethyl) aminomethyl]-o-cresolsulfonphthalein-Ferrous(III)) with bovine serum albumin (BSA) were studied by the combination of ultraviolet spectroscopy, circular dichroism (CD) spectroscopy, fluorescence spectroscopy and synchronous fluorescence spectroscopy. On that basis, the sonodynamic and sonocatalytic damages of Cresol Red derivatives to BSA under ultrasonic irradiation were also investigated by means of corresponding spectrum technology. Meanwhile, some influenced factors such as ultrasonic irradiation time, Cresol Red derivatives concentration and ionic strength on the damage degree of BSA molecules were also reviewed. In addition, the binding site and damage site of BSA molecules were estimated by synchronous fluorescence spectra. Finally, the results of oxidation-extraction photometry (OEP) using several reactive oxygen species (ROS) scavengers indicated that the damage of BSA molecules is mainly due to the generation of ROS. Perhaps, this paper may offer some important subjects for broadening the application of Cresol Red derivatives in sonodynamic therapy (SDT) and sonocatalytic therapy (SCT) technologies for tumor treatment.

International audience; Cresol Red (CR) pH indicator was encapsulated into silica network using the sol–gel process. Transparent monolithic disks of entrapped CR were obtained in the presence of cetyl trimethyl ammonium bromide (CTAB) or dodecyl dimethyl amino oxide (Genaminox LA,GLA) alkyl hydroxyethyl dimethyl ammonium chloride (HY, R = 12–14) and TX-100 surfactants. UV/VIS spectra showed that the encapsulated CR retains its structure in terms of its response to pH. At the neutral conditions it is found that the HY surfactant is considered as proton donor as favor the cationic form of the indicator, while CTAB surfactant favor the neutral, however GLA surfactant, the anionic form of CR is more favored because GLA has a zwitterionic head. The surfactant GLA with TEOS has shifted the equilibrium to the ionized form of CR due to the electrostatic interaction between the surfactant and the CR anion. Therefore their pH range is dependent on the nature of a surfactant used. It is found that the HY surfactant is more efficient as far as loading of CR is concern and it widened the working pH range.

A new method is proposed for the determination ofo-Cresol Red in Xylenol Orange and semi-Xylenol Orange by third-order derivative spectrophotometry at 491 nm in a medium of 0.09 mol/1 sulphuric acid. A linear relationship exists between d3A/dλ3 and theo-Cresol Red concentration (1–12 μg/ml), with a standard deviation of 0.11 μg/ml (n = 8) for 10 μg/ml ofo-Cresol Red.

Ion-associates of N,N-diethyllysergamide with the sulfophthaleins: Bromoxylenol Blue, Eriochrome Cyanine R, Xylenol Blue, and Cresol Red, and the azo dyes: Acid Black I and Orange-I were studied by extraction spectrophotometry. The extraction recoveries, distribution ratios, conditional extraction constants and limits of detection and determination were calculated.

If buffer/indicator systems are used as optical thermometers in multicuvettes, the temperature resolution is limited by errors of optical measurements produced mainly by variations of pathlength and blank transmittance of the wells. Theoretical and practical approaches show that, in multicuvettes, a between-well temperature resolution of < 0.05 degrees C can be achieved by multiwavelength photometry with use of the Tris/cresol red indicator system. Using up to three absorbances (A0, A1, A2) measured in the same well at different wavelengths for calculation of differences, quotients, and quotients of differences, we found the optimum temperature signal to be In(A1/A2), with equal-ranking absorbances changing with temperature in opposite directions. We have used the method successfully to measure the temperature profiles and temporal dynamics of temperatures at all positions in two types of multicuvettes under controlled conditions, or not controlled thermostatically.

Analytical possibilities of apparent content curves for ternary systems are studied. The mathematical method proposed is applied to UV-Vis spectrophotometric and fluorimetric techniques. Samples containing fluoresceine/eosine/acridine and methyl red/methyl orange/cresol red are resolved by fluorimetry and UV-spectroscopy, respectively. Results obtained are in agreement with the theoretical contents in both cases.

An extraction method based on the butanol—water system is used in an improved spectrophotometric determination of Xylenol Orange (XO), Semi-Xylenol Orange (SXO) and Cresol Red (CR) in mixtures. Small amounts of SXO in the presence of much greater amounts of XO, and small amounts of XO in the presence of large amounts of SXO can be determined with good accuracy after extractive separation of the compound to be determined, from the bulk of the other components of the mixture.

Dye-binding stoichiometry and selectivity of the reactions of several standard proteins and protein matrices with the phthalein dye cresol red (CR) are presented. Spectrophotometric measurements show that the interactions are selective; amino acids, peptides, and albumin-type proteins do not react at all. The optimum analytical conditions of the reactive proteins—human gamma globulin (HGG), casein (C), milk protein (MP), soya bean (SBM), meat (MM), and fish meals (FM)—with CR are given. Dye-binding values obtained with soya bean meals are complemented by the sodium dodecyl sulfate-polyacrylamide gel electrophoretic patterns (SDS-PAGE) of the same samples, in order to show a qualitative picture of the molecular weight distribution of three untreated samples when comparing them to their respective denatured ones.

[reaction: see text] The high reactivity of the chloroacetyl group has been exploited for the synthesis of bile acid based first and second generation dendrons with multiple hydroxyl groups. The synthesis involves only a few steps and avoids the use of protecting groups for the terminal hydroxyl groups. These dendritic structures with facially amphiphilic bile acid backbones on the periphery were able to solubilize cresol red, a hydrophilic dye, in a nonpolar solvent. HPLC analysis of the dendrons suggests that hydrophobicity increases with increase in oligomer size, but in each generation, the dendrons with a higher degree of branching are less hydrophobic.

An optical biosensor based on immobilised carbonic anhydrase and its application to the determination of the anti-glaucoma agent acetazolamide by enzyme inhibition measurements, is described. The enzyme and a pH indicator dye, cresol red, were physically immobilised in overlapped sol-gel thin films, in a dual-layer format. Carbonic anhydrase catalyses the dehydration of HCO3-, which in turn causes a change of pH in the microenvironment of the sensor. By following the colour transition of cresol red, the enzymatic reaction as well as its inhibition by acetazolamide can be monitored. The sensor was integrated in a flow cell and coupled to a continuous flow system operating on a multicommutation and binary sampling approach. Measurements were made at pH 6.0 at the wavelength of 570 nm. Linear response was obtained for acetazolamide concentrations between 1.0 and 10.0 mmol l(-1), with a sampling frequency of 22 samples h(-1) and a detection limit of 0.2 mmol l(-1). The results obtained in the analysis of real samples were in good agreement with those obtained by a reference method, showing no significant differences at a confidence level of 95%.

A new optical CO(2) sensor based on the luminescence intensity change of the europium(III) complex tris(thenoyltrifluoroacetonato) europium(III) dihydrate ([Eu(tta)(3)]) caused by the absorption change of various pH indicators-thymol blue, phenol red, or cresol red-with CO(2) was developed and its CO(2) sensing properties were investigated. For all the CO(2) sensors using pH indicators the observed luminescence intensity from [Eu(tta)(3)] at 613 nm increased with increasing CO(2) concentration. The linear calibration method based on the plot of (I(100)-I(0))/(I-I(0)) versus the inverse of CO(2) concentration was suggested, where I(0) and I(100) were luminescence intensities at 613 nm of the CO(2) sensor film in 100% nitrogen and 100% gaseous CO(2). In all cases the plots showed good linearity and the correlation factors of the plots, r(2), were 0.991 for thymol blue, 0.990 for phenol red, and 0.998 for cresol red. The slopes of the plots (A/B) for thymol blue, phenol red, and cresol red were 2.2, 5.2, and 9.0%, respectively. The response times of the CO(2) sensor film were 4.0 s for thymol blue, 4.4 s for phenol red, and 8.8 s for cresol red for switching from nitrogen to CO(2), and the recovery times of films were 36 s for thymol blue, 39.2 s for phenol red, and 56.6 s for cresol red for switching from CO(2) to nitrogen. The signal changes were fully reversible and hysteresis was not observed during the measurements. The highly sensitive CO(2) sensor was developed using thymol blue as an indicator for the CO(2)-sensing probe.

Two sensing ensembles based on the common squaramide host 2 and the acid–base indicators Cresol Red (CR) and Bromocresol Green (BG) are described. Both couples were characterized in EtOH–H2O mixtures by UV-Vis spectroscopy. Analysis of the binding curves and the corresponding Job plots indicate 1 : 1 binding between the indicators CR or BG and host 2. The sensing solutions are responsive to sulfate and/or phosphate anions in water, changing the coloration of the solution. As in other indicator displacement assays (IDA), host 2 translates the chemical event into a colorimetric response that is analyzed by spectrophotometry. However, since other anions present in natural waters do not result in color changes, this method allows the quantification of sulfate and phosphate in water.

Results of the characterisation of a quasi-distributed optical fibre chemical sensor are presented. Sensors have sections of cladding containing immobilised chemically sensitive compounds. Optical time domain reflectometry technique is used for sensor interrogation exploiting evanescent wave interactions. Responses of Cresol Red and cryptocyanine dye based sensors to alkaline and acid vapours are presented and discussed.

The leakage of chloride from electrodes during measurements of the alkaline Bohr effect of hemoglobin (by the proton release method) amounted to 1-5 mM concentration of the anion depending on the type of electrode employed. This concentration, together with the amount of chloride found to be intrinsically bound to hemoglobin (0.2-0.6 mM), could mask the contribution of chloride to various hemoglobin functions. In addition, the concentration of chloride was found to affect the pH of buffers as measured either with a pH meter or with the dye, cresol red. Thus, for 20 mM phosphate buffer, the pH was lowered almost 0.4 pH units in the presence of 0.30 M chloride. For Tris-acetate buffer, the same concentration of chloride led to an increase in pH of about 0.05 units.

Observations of sulfonephthalein absorbance ratios provide the basis for very precise measurements of seawater pH. Our analyses, using cresol red, indicate that meaningful pH comparisons at sea can be obtained at the level of ±0.001 pH units or better. Comparison of replicate seawater samples obtained from different Niskin bottles exhibited, in most instances, agreement within 0.0005 pH units. The procedures involved in multiwavelength pH measurements are quite simple relative to the required methodology in single wavelength observations.

A rapid, sensitive and reliable mixed indicator paper strip impregnated with dimethyl yellow (0.05%), cresol red (0.1%) and mercuric chloride (1.0%) in methanol has been developed for the detection of phosphine (PH3) in air at the permissible level (TLV). The paper strip turns red in the presence of phosphine. It is highly sensitive and has better shelf-life than indicator strips impregnated with dimethyl yellow plus mercuric chloride or cresol red plus mercuric chloride.

We evaluated the analytical performance of the Hitachi 704 automatic analyzer. The spectrophotometer showed a linearity of response at 340 nm up to 2.8 A. Photometric imprecision measured bichromatically at 340 and 376 nm was 0.49% at 0.16 A, 0.14% at 0.46 A, and 0.17% at 0.76 A. Imprecision of the sample probe was 0.4% for 5, 10, and 20 microL, and the volume delivered deviated -2.4%, -4.4%, and -4.2% from these preset volumes, respectively. Imprecision of the reagent probe over the range 50 to 500 microL ranged from 0.14% to 0.29%; volume delivered deviated from +1.7% to +4.4%). At equilibrium, the temperature in the cuvets was 29.8 (SD 0.05) degree C as measured by cresol red spectrophotometry. No sample carryover was detected. Reagent carryover was detected when a bilirubin assay was preceded by a total protein assay and when lactate dehydrogenase was measured after alanine aminotransferase. Imprecision for nine tests at three concentrations ranged from 1.1% to 4.4%. Comparison of methods with the SMAC II as reference method showed good results. Precision was better than reported for the Hitachi 705 automatic analyzer.

1. It is not always feasible to determine pH on board ship, owing to bad light and other conditions, although it may be possible to collect water samples.2. By preserving the water samples on collection with mercuric chloride solution (four drops per 100 c.c. of water) and by taking care to leave only a small air-space in the bottles it is possible to keep the water practically unchanged for many days.3. Test tubes containing such water (10 c.c.) plus 0·02% cresol red (0·5 c.c.) have been-kept unchanged for three weeks at 12–14° C. and for two days at 33° C, whereas unpreserved water showed a drop in pH of 0·05 unit in one day at 12° C.4. McClendon buffer solutions may also be preserved by mercuric chloride, but in this case a small correction must be applied since complex formation leads to a removal of effective buffer salts from the solution and a small decrease in pH.

Cresol red was found to be the most suitable of the six colour pH indicators tested for the colorimetry of CO2 concentration within the range of 100 to 2000 p.p.m. In the region near pH 8-2 (corresponding approximately to 300 p.p.m. CO2)this indicator is most suitablein view of its low unit concentration, although somewhat greater differences in absorbancy can be found on changing pH by one unit if an approximately six-fold higher concentration of thymol blue is used. For higher concentrations of CO2 (pH below 7-5) phenol red is most appropriate. Tropaeolin 000 and aurin (rosolic acid) are not suitable. It is more convenient in spectrophotometry and colorimetry using filters with narrow spectral ranges to apply any of the above indicators in the green-yellow-orange spectral region rather than in blue radiation.

Mice can be vitally stained with many of the phthalein indicators. The staining is diffuse, appearing to interfere not at all with health in the case of the majority of the dyes. The color phenomena show that these retain the character of indicators. A special technique has been evolved for the determination of the hues of the various organs, which are readily modified by extraneous influences. The ability to recognize that the pH has thus been altered is a signal advantage of the indicator method. Phthaleins of slightly alkaline range or one that trenches slightly on acidity have been employed for the work here reported. Cresol red, phenol red, and brom phenol red have proved especially useful. The observations with the three agree closely in pointing to the existence of notable differences between the reaction of the blood and that within the tissues generally. The hue of blood plasma from the right heart is such as to suggest that its reaction lies at about pH 7.38 ordinarily, whereas that of the most alkaline of the tissues, judging from its color, the connective tissue, would appear to have a pH of 7.2 or slightly less. The tendons seem to be nearly but not quite so alkaline. The other stained tissues without exception, are of a hue which would indicate that the reaction lies beyond the range of phenol red on the acid side, that is to say is at least as acid as pH 6.6. In a subsequent paper observations which accord with these findings, carried out with indicators of frankly acid range, will be described. On the exposure of tissues to air, without disturbance of the circulation, some of them become alkaline. In the case of connective tissue, at least, the change is a consequence of the escape of carbon dioxide. The gas passes readily in and out, exerting a practically immediate influence on the color of the tissue bared by eversion of a skin flap; and so much may be absorbed on exposure to pure carbon dioxide, when the surface is large, that a general acidosis results. The precise interpretation of the color changes in terms of pH waits necessarily upon further work.

A 1% solution of mercuric chloride in 0.1% cresol red in ethanol, impregnated onto celite and filled into a glass tube [17.8 cm × 0.2 cm (i.d.)] could accurately determine even 0.06 μg phosphine in air. The samples were injected quickly through a rubber septum cap on the glass tubes under low suction. A red coloured band developed instantaneously, the length being proportional to the concentration of phosphine. A calibration curve was prepared with known concentrations of phosphine. The concentrations present in a fumigation chamber were determined and compared with concurrent chemical analysis. There was close agreement between the two methods. A 1:3 and 1:6 mixture of phosphine and ammonia produced two bands, a yellow ammonia band preceding the red phosphine band. However, ammonia interfered with the proper development of the phosphine band.

A method is described for the sub-micro determination of bromine in organic compounds. A colorimetric finish is used employing cresol red as a reagent. 2–40 μg of bromine were determined with standard deviations of 0.08–0.16 μg. Straight line calibration curves were obtained within this range. Interferences were given only by chloride and iodide, provided that oxidising and reducing agents were absent. The procedure has been succesfully applied to the analysis of a number of organic materials.

A pH-scale in ethylene glycol is defined, based on potentiometric measurements for a cell without liquid junction: glass electrode || 0.1M (HCl + KCl), ethylene glycol | AgCl:Ag; and a potentiometric-spectrophotometric method for the determination of pK-value of acid-base indicators in ethylene glycol on the basis of this pH scale is proposed, in which the pH scale is established and the pK-value determined in a single titration at constant ionic strength. The following pK-values of indicators are reported: Cresol Red-3.00, Thymol Blue-3.39, Bromophenol Blue-6.49, Bromocresol Green-7.38, Bromocresol Purple- 9.00 and Cresol Red (2nd change)-11.07. A linear relationship was found between the pK-values of four sulphonphthalein indicators in ethylene glycol and in water according to the following equation (pK(HI)(c))(EG) = 2.3 + 1.1 (pK(HI)(c))(W). An attempt is made to explain this dependence, based on the idea of solute-solvent interaction of species of the same charge type.