Rate Of Color Development Research Articles

Rapid determination of the antimicrobial properties of surfaces using an enzymatic activity surrogate

AbstractTypical approaches for assessing the antimicrobial activity of metals‐based surfaces involve the contact of a bacterial culture with the surface for a period of time, followed by culturing on agar plates to assess the decrease in microbial viability versus controls. This is a time‐consuming methodology requiring at least 24 h to produce a set of results, which can be a bottleneck for productivity in novel materials development. An enzyme‐based method was shown to be a satisfactory and much more rapid surrogate test for this application. A β‐galactosidase solution was applied to copper, silver, and zinc‐based antimicrobial surfaces for up to 1 h, and then the rate of colour development at 578 nm was monitored for a few minutes after addition of the chromogenic enzyme substrate chlorophenol red‐β‐d‐galactopyranoside (CPRG). Highly active antimicrobial surfaces were detected by a lack of colour development, due to enzyme inhibition by the metals. The enzymatic reaction rates were quantified and compared, demonstrating that the copper sample showed the greatest inhibition effect followed by the silver and zinc samples. The antimicrobial activity was quantified using bacteria and the plate count method, and the results correlated well with this enzyme assay, demonstrating that the metals‐based antimicrobial activities of both hard and soft (textile) surfaces could be quickly assessed with this enzyme‐based methodology.

Colorimetric analysis based on solid-phase extraction with sedimentable dispersed particulates: demonstration of concept and application for on-site environmental water analysis.

A novel simple and functional colorimetric methodology for on-site environmental water analysis was proposed. This method combines coloration of the analyte and extraction of the colored species on dispersed particulates during their sedimentation in the same container. The whole analysis can be performed within 15 min by comprising the addition of 1 mL of sample solution into a 1.5-mL microtube containing the powders of coloring reagents and the sedimentable fine particulates as an adsorbent. The analyte is determined by comparing the sediment color with the standard color by visual inspection or the color information of the photo image. The potential of this methodology was demonstrated through developing colorimetry for Fe2+ with o-phenanthroline, NO2- by azo-dye formation, HCHO by the MBTH method, and PO43- by the 4-aminoantipyrine method based on the enzyme reactions. The material, size, amount of the adsorbent particles, and other conditions were optimized for each analytes. The advantages of the methodology were as follows: high sensitivity, easy controllability of the sensitivity over the wide range by the amount, size, and material of the particulates, lower interference from the colored matrix components due to obtaining the color data from not the aqueous phase but the sedimented particulates, and acceleration of the color development rate by the particulates as seen in NO2- determination as consequence shorten the operation time. A simple device equipped with twin cells was proposed for on-site analysis which contains two successive different coloring operations. The developed methods were successfully applied to the environmental water samples with the good agreement of the results with those by the usual instrumental methods.

Mixed-Linker Strategy for the Construction of Metal-Organic Framework Combined with Dyes toward Alcohol Detection.

Herein, a N-rich metal-organic framework (MOF) with four kinds of cages, Zn4(ade)2(TCA)2(H2O) (NENU-1000, Hade = adenine, H3TCA = 4,4',4″-tricarboxytriphenylamine, NENU = Northeast Normal University), was prepared by the mixed-ligand strategy. Cationic dyes can be selectively absorbed by NENU-1000 at proper concentrations, but not neutral and anionic dyes, which perhaps can be assigned to the N-rich neutral framework of NENU-1000. When NENU-1000 was introduced to a relatively lower concentration of cationic dye solutions (e.g., rhodamine B or basic red 2), the colors of these systems faded quickly. Furthermore, the faded solutions can be used for the detection of methanol and other small alcohol molecules with either the naked eye or common UV-vis spectra. The effect of the length of carbon chain, the position of the -OH group, and the number of the hydroxyl group of the alcohols was explored for the color development rate. In addition, the performance of NENU-1000 in iodine sorption and release was also studied.

Novel kinetic spectrophotometric method for estimation of certain biologically active phenolic sympathomimetic drugs in their bulk powders and different pharmaceutical formulations

A simple, selective and sensitive kinetic spectrophotometric method was described for estimation of four phenolic sympathomimetic drugs namely; terbutaline sulfate, fenoterol hydrobromide, isoxsuprine hydrochloride and etilefrine hydrochloride. This method is depended on the oxidation of the phenolic drugs with Folin-Ciocalteu reagent in presence of sodium carbonate. The rate of color development at 747–760nm was measured spectrophotometrically. The experimental parameters controlling the color development were fully studied and optimized. The reaction mechanism for color development was proposed. The calibration graphs for both the initial rate and fixed time methods were constructed, where linear correlations were found in the general concentration ranges of 3.65×10−6–2.19×10−5molL−1 and 2–24.0μgmL−1 with correlation coefficients in the following range 0.9992–0.9999, 0.9991–0.9998 respectively. The limits of detection and quantitation for the initial rate and fixed time methods were found to be in general concentration range 0.109–0.273, 0.363–0.910 and 0.210–0.483, 0.700–1.611μgmL−1 respectively. The developed method was validated according to ICH and USP 30 –NF 25 guidelines. The suggested method was successfully implemented to the estimation of these drugs in their commercial pharmaceutical formulations and the recovery percentages obtained were ranged from 97.63%±1.37 to 100.17%±0.95 and 97.29%±0.74 to 100.14±0.81 for initial rate and fixed time methods respectively. The data obtained from the analysis of dosage forms were compared with those obtained by reported methods. Statistical analysis of these results indicated no significant variation in the accuracy and precision of both the proposed and reported methods.

DELAYED COLOR BREAK IN 'TARDIVO', A LATE RIPENING MANDARIN MUTANT, IS RELATED TO A DEFECTIVE ETHYLENE RESPONSE

Delaying peel senescence in clementine mandarins is of paramount importance in the citrus industry because it extends the harvesting period and improves the shelf life of the fruits. Gibberellins and ethylene treatments have been used for delaying or accelerating color development in citrus fruit peel, respectively, indicating a prominent role of these hormones in the regulation of the external ripening process. Late ripening mutants constitute an extremely useful tool to decipher the molecular bases regulating the timing and the rate of color development in citrus fruits. Although the causes for these phenotypes may be diverse, there is recent evidence in the literature linking delayed degreening with altered ethylene sensitivity. ‘Tardivo’ is a late ripening mutant of clementine mandarin that displays a delay in peel degreening, color development and expression of carotenoids biosynthetic genes. In the present work we have explored if this phenotype is associated with altered sensitivity to ethylene. Therefore, we have examined the expression of genes involved in carotenoids, ABA biosynthesis, and ethylene signaling and biosynthetic pathways in response to ethylene. The results indicated that ‘Tardivo’ fruits displayed a transient response to ethylene but it was unable to sustain subsequent ethylene-induced gene expression. It is then concluded that the delay in color development of ‘Tardivo’ mandarin may be related to a defective sensitivity or response to ethylene.

Fatigue Determination of Photochromic Dyes in Silica and Polyamide Matrices via Analysis of CIELAB Parameters

To address reported problems in investigating photochromic dye fatigue, this paper describes a new method of “dissolved” photochromic organic dye analysis within polar silica matrices. Conditions under which a photochromic response occurs in a given material are de ned by specifying the light source (irradiation wavelength) and exposure time that leads to photochromism. Fatigue, de ned as poor lightfastness, is researched through consecutive cycles of exposure to the direct in uence of a de ned UV irradiation source. From the spectrophotometric graphic analysis in CIELAB, a conclusion can be made on the lifespan of photochromic textile products. is paper addresses issues regarding the rate of color development, and the controlled, predictable return to a colorless state, which is the base of any device working on the principle of reversibility.

Improvement of Red Color Development on the Surface of Kuruma Prawn Marsupenaeus japonicus under Various Conditions

The degree of red color development on the surface of prawns by cooking is an important index for food quality. In this study, we tested several factors that are thought to influence the red color development to identify possible correlations with various conditions. Live kuruma prawns, Marsupenaeus japonicus, (15.4 cm, 25.2 g on average) were used in this study. In case of cooking at 100 °C for 1 min after 24 h of storage at 0 °C, 5 °C, and 20 °C, the red color development rate of prawns stored at 5 °C and 20 °C was significantly lower than that of prawns cooked just after killing. In case of cooking at 100 °C, 80 °C, and 60 °C after storage for 24 h at 0 °C, there was no color development at 60 °C and significantly less color development at 80 °C compared to cooking just after killing. Preparation using 1% sodium carbonate before cooking at 80 °C could compensate for the lack of red color development. Short exposure of live kuruma prawns to low-oxygen conditions had no influence on the color development, but putting the prawns in freshwater for 3 h significantly reduced the red color development rate. In conclusion, the storage time has little influence on the red color development when the cooking temperature is sufficiently high. However, in case a large amount of prawns is cooked followed by lowering the cooking temperature and/or prawns are exposed to serious stresses before cooking, an alkaline preparation could compensate for the lack of red color development.

Effect of Roasting Conditions on Color and Volatile Profile Including HMF Level in Sweet Almonds (Prunus dulcis)

Microwave, oven, and oil roasting of almonds were used to promote almond flavor and color formation. Raw pasteurized almonds were roasted in a microwave for 1 to 3 min, in an oven at 177 °C for 5, 10, 15, and 20 min; and at 135 and 163 °C for 20 min, and in oil at 135, 163, and 177 °C for 5 min and 177 °C for 10 min. Volatile compounds were quantified in the headspace of ground almonds, both raw and roasted, by selected ion flow tube mass spectrometry. Strong correlations were found between L value, chroma, and 5-(hydroxy methyl)-2- furfural; and were independent of roasting method. Raw almonds had lower concentrations of most volatiles than roasted almonds. Conditions that produced color equivalent to commercial samples were 2 min in the microwave, 5 min at 177 °C in the oven, and 5 min at 135 °C in oil. Microwave heating produced higher levels of most volatiles than oven and oil roasting at commercial color. Sensory evaluation indicated that microwave-roasted almonds had the strongest aroma and were the most preferred. Oil-roasted almonds showed significantly lower levels of volatiles than other methods, likely due to loss of these volatiles into the oil. Alcohols such as benzyl alcohols and strecker aldehydes including benzaldehyde and methional were at higher concentrations than other volatiles in roasted almonds. The oxidation of lipids to form alkanals such as nonanal and degradation of sugars to form furan type compounds was also observed. The Maillard reaction contributed to the formation of more of the total volatiles in almonds than the lipid oxidation reaction. The level of 5-(hydroxy methyl)-2- furfural (HMF), color, volatile profile, and sensory perception can be used to develop the best roasting method, time, and temperature for almonds. The rate of color development and the production of volatiles differ under different roasting conditions. Based on the color, volatile, and sensory assessments of the 3 almonds, the use of microwave technology as a process for roasting almonds reduces processing time and leads to an almond product with better flavor than oven or oil roasting.

Harvesting fruit of equivalent chronological age and fruit position shows individual effects of UV radiation on aspects of the strawberry ripening process

The effect of UV radiation on fruit secondary compounds of strawberry cv ‘Elsanta’ was recorded taking chronological age and fruit position on the truss into account. When fruit of similar age post-anthesis, and truss position were compared, we found that the concentration of secondary compounds differed according to fruit position on the truss. UV radiation hastened the rate of colour development and resulted in an increase in fruit anthocyanin (14–31%), flavonoid (9–21%) and phenolic (9–20%) contents at harvesting; but it had no effect on fruit soluble solid content, pH and volatile composition. It did, however, increase leaf flavonoid (16%) and phenolic (8%) concentrations. Fruit ripened under a UV transparent film were firmer, smaller but greater in number than fruit ripened under a UV opaque film. Overall, the results indicate that UV radiation does not affect all aspects of strawberry ripening but independently alters rate of colour development and fruit firmness.

PECTIN‐BASED EDIBLE COATING FOR SHELF‐LIFE EXTENSION OF ATAULFO MANGO

ABSTRACTMango is a commercial but highly perishable fruit, and therefore, a longer shelf life is necessary for its successful marketing and consumer satisfaction. This study aims at evaluating the effects of edible coating, based on pectin, on the quality and shelf‐life extension of mangoes. The coating formulations included different combinations of pectin, beeswax, sorbitol and monoglyceride. The fruits were coated and stored at room temperature along with uncoated controls. Samples tested were evaluated periodically for quality parameters, which included visual observation, weight loss, respiration rate, color, firmness, pH, soluble solids (SS), titrable acidity and extent of decay. The coated‐fruits reduced the rate of color development, texture softening, weight loss, CO2 evolution and acid production (only pH and SS increased) compared with the control. The shelf life of control sample was less than a week, whereas the coated fruits remained good for over 2 weeks, thereby offering a significant advantage.PRACTICAL APPLICATIONSThe study evaluates the use of pectin‐based edible coating for extending the shelf life of mango. The formulation is a blend of hydrophilic and hydrophobic groups to provide controlled respiration and water vapor permeability. The properties of pectin films have been highlighted in a previous paper, and several applications based on the coating have been demonstrated. The present study demonstrates that modifications to the formulation were necessary in order to successfully apply it to mango. Mango is a popular commercial product with high heritability. Simple edible coatings that can help to improve the shelf life and marketability of the product will be of significant interest in the marketing of mango products.

Volatile Profile of Cashews (Anacardium occidentale L.) from Different Geographical Origins during Roasting

Volatile compounds were quantified in the headspace of Indian, Vietnamese, and Brazilian cashews, both raw and during roasting by selected ion flow tube-mass spectrometry. The optimum roasting times based on color measurements were also determined. Raw cashews were oil roasted for 3 to 9 min at 143 °C and color and volatiles measured. An excellent correlation, following a pseudo 1st-order reaction, was found between L* value and roasting time; darkness increases as roasting time increases. The optimum roasting time was 6, 8, and 9 min for Vietnamese, Indian, and Brazilian cashews, respectively. Raw cashews had lower concentrations of volatiles than roasted cashews. Most volatiles significantly increased in concentration during roasting of Brazilian, Indian, and Vietnamese cashews. Only a few volatiles significantly decreased during roasting. Ethanol and 1-heptene significantly decreased during roasting in Brazilian cashews and toluene decreased in Vietnamese cashews. Brazilian cashews had significantly higher levels of most volatiles than Indian and Vietnamese cashews. Most volatile levels in Indian and Vietnamese cashews were not significantly different. Of the volatiles, Strecker aldehydes, including methylbutanal, 2-methylpropanal, and acetaldehyde, were at the highest concentration in roasted cashews. The Maillard reaction contributed to the formation of most of the volatiles in cashews from the 3 countries. There was also degradation of sugars to form furan-type compounds and oxidation of lipids to form alkanals such as hexanal. The volatile profile during roasting of cashews can be used to determine the best roasting time for each type of cashew. The rate of color development and the production of volatiles differ for the cashews from the 3 geographical locations.

Changes in Microbial Functional Diversity and Activity in Paddy Soils Irrigated with Industrial Wastewaters in Bandung, West Java Province, Indonesia

Characteristics, such as microbial biomass, basal respiration, and functional diversity of the microbial communities, were investigated in paddy soils located in Bandung, West Java Province, Indonesia, that have been heavily polluted by industrial effluents for 31 years. Paddy soil samples (10–20 cm) were taken from two sites: polluted soils and unpolluted soils (as control sites). The polluted soils contained higher salinity, higher sodicity, higher nutrient contents, and elevated levels of heavy metals (Cr, Mn, Ni, Cu, and Zn) than unpolluted soils. Soil physicochemical properties, such as maximum water holding capacity, exchangeable sodium percentage, sodium adsorption ratio, and swelling factor, in polluted soils were much greater than those in unpolluted soils (P < 0.05). Changes in the physical and chemical soil properties were reflected by changes in the microbial communities and their activities. BIOLOG analysis indicated that the functional diversity of the microbial community of polluted soils increased and differed from that of unpolluted soils. Likewise, the average rate of color development (average well color development), microbial biomass (measured as DNA concentration), and the soil CO2 respiration were higher in polluted soils. These results indicate that major changes in the chemical and physical properties of paddy soils following the application of industrial wastewater effluents have had lasting impacts on the microbial communities of these soils. Thus, the increased activity, biomass, and functional diversity of the microbial communities in polluted soils with elevated salinity, sodicity, and heavy metal contents may be a key factor in enhancing the bioremediation process of these heavily polluted paddy soils.

Kinetics of Potato Color and Texture Development during Baking, Frying, and Microwaving with the Addition of Liquid Smoke

ABSTRACT: The rate of color and texture development in par‐fried French fries coated with liquid smoke and thermally processed was determined. Liquid smoke containing 8% to 11% carbonyls was diluted to 30% and applied to 1 side of French fries at 0%, 1%, 3%, or 5% by weight. The fries were immersion fried at 190.6 °C for 4 min, microwaved (900 watts) for 4 min, or baked at 190.6 °C for 20 min. Color and texture measurements were recorded at intervals during processing. Liquid smoke increased the rate of browning in French fries. Browning followed pseudo zero‐order kinetics, with the a value, Browning index, and total change in color (ΔE) showing the best fit. When liquid smoke was added in high concentrations the reaction rate did not increase as more liquid smoke was added because the carbonyls were no longer limiting the rate of Maillard browning. The rate of color development in French fries was also affected by the thermal processing method. Frying developed color at the fastest rate, followed by microwaving and baking. Although liquid smoke increased the rate of color development in French fries, it did not affect French fry texture. Through sensory testing, it was determined that liquid smoke can be used to improve the color of microwaveable French fries without affecting French fry flavor or texture.

Analysis and interpretation of community-level physiological profiles in microbial ecology

A rapid, community-level approach for assessing patterns of sole carbon source utilization by mixed microbial samples has been used increasingly to study microbial community dynamics. The method involves direct inoculation of environmental samples into Biolog microtiter plates, and uses color formation from reduction of a tetrazolium dye to assess utilization of 95 separate sole carbon sources during a 2–7 day incubation period. This approach, called community-level physiological profiling, has been effective at distinguishing spatial and temporal changes in microbial communities. Effective analysis of the multivariate profiles of carbon source utilization requires separation of effects caused by differences in inoculum density (i.e. overall rate of color development) from effects caused by differences in the types or activities of organisms present (i.e. relative rates, or pattern, of carbon source utilization). Further experimental studies are required to better define what fraction of the original inoculum responds in the assay, and if the profiles provide structural and/or functional information.

SURFACE COLOUR CHANGE IN WOOD DURING DRYING ABOVE AND BELOW FIBRE SATURATION POINT

A technique, useful for studying the formation of kiln brown stain in wood drying, has been developed to measure the surface colour change in a single board wood sample during drying. The wood sample is planed carefully in the green state to remove any surface wood that was damaged during cutting. The intact tracheids at the surface cause the evaporative front to remain at the surface during drying and therefore colour formation also occurs right at the surface. In this way, the colour can be measured using a spectrophotometer at various stages during drying without having to slice the sample. Experiments were carried out to measure the change in colour of wood from green to EMC corresponding to the drying schedule used. At the end of each schedule the boards were held at the EMC to determine how the colour changed below fibre saturation point. The results show that the colour of the wood continues to change below the fibre saturation point and the nature of the colour change indicates an increase in the complexity of the coloured compounds present. Further experiments were done to measure the rate of colour development at different temperatures using the technique developed. The results have shown a correlation between temperature and colour development over the range 50oC to 70oC with the rate increasing significantly above 60oC.

Effect of Near‐infrared Radiation and Jet Impingement Heat Transfer on Crust Formation of Bread

ABSTRACTRapid heat transfer methods can be used to speed up the baking process and create new product properties. This study investigates the effect of air jet impingement and infrared radiation (alone or in combination) on crust formation of par‐baked baguettes during post‐baking. The parameters investigated are crust color, crust thickness, total water loss, and heating time. The results show that infrared radiation and jet impingement, as compared with heating in a conventional household oven, increased the rate of color development of the crust and shortened the heating time. The fastest color development was obtained by combining infrared and impingement heating. The water loss rate was increased due to the high heat transfer rate, but the total water loss was reduced because of the shorter heating time. Crust thickness was most dependent on heating time and crust temperature. In general, the crust was thinner for infrared‐heated baguettes.

Kinetic spectrophotometric methods for determination of trimetazidine dihydrochloride

Four simple and sensitive kinetic spectrophotometric methods (I–IV) for the determination of trimetazidine dihydrochloride (TRMZ) have been developed. Method I was based on the oxidation of the drug with alkaline KMnO 4 producing green manganate species. Method II was based on the formation of colored condensation product between TRMZ and 4-chloro-7-nitrobenzofurazan (NBD-Cl). Method III was based on reaction of TRMZ and with 1,2-naphthoquinone-4-sulphonic acid sodium salt (NQS) forming orange colored product. Method IV was based on the formation of a violet charge-transfer complex between trimetazidine base and p-chloranil ( pCL). These reactions were followed spectrophotometrically by measuring the rate of color development at 610, 475, 485 and 560 nm for the reactions with KMnO 4, NBD-Cl, NQS, and pCL, respectively. The variables affecting the reactions were carefully investigated and the conditions were optimized. The stoichiometries of the reactions were determined, and the reactions pathways were postulated. The initial rate and fixed time methods were utilized for constructing the calibration graphs for the determination of TRMZ concentration. The assays limits of detection were 0.2–2.5 μg ml −1. The analytical performance of the methods, in terms of accuracy and precision, were statistically validated; the results were satisfactory. The methods have been successfully applied to the determination of TRMZ in commercial pharmaceutical formulations. Statistical comparison of the results with the reference method showed excellent agreement and proved that no significant difference in the accuracy and precision.

Effect of Inoculum Standardization on Community Level Physiological Profiles Of Compost Samples

The potential of Community Level Physiological Profiles (CLPPs) as a compost maturity test is significant, given the sensitivity and the simplicity of the assay. Nevertheless, application of the technique to compost requires more methodological work because of the fast changes in physicochemical and microbiological properties and the dependence of the rate of color development on the inoculum density. The aim of this work was to investigate the reliability of a new approach to standardize inoculum density and the effects of different data interpretation and storage conditions on CLPPs of compost samples with different degree of stabilization. Compost samples (fresh, air dried, frozen and air dried-rewetted) with different degree of stabilization were extracted with a two-batch procedure and then inoculated on Biolog Ecoplates. Standardization of inoculum density was performed according to microbial biomass content determined by substrate induced respiration (SIR) on fresh samples. Microplates were incubated at 30°C in the dark and optical density (OD) was measured at 592 nm every 8 hours for 7 days. Principal component analysis (PCA) was performed on various data sets: OD values at fixed average well color development (AWCD), kinetic parameters and area under the OD curve as a function of time. PCA of fresh samples showed that classification and ordination of samples according to their age were satisfactory with fixed AWCD and area under the curve data sets, suggesting the reliability of SIR for the standardization of inoculum density. These results support the most universally applicable approach to data collection, implying approximate standardization of inoculum density and continuous plate reading, but, at the same time, underline the importance of the data set construction for PCA analysis. Ordination patterns obtained from air dried samples showed a good resemblance with those obtained from fresh ones, suggesting that analyses aimed to evaluate the degree of compost maturity could be successfully performed on samples with low water content.

Community level physiological profiling as a tool to evaluate compost maturity: a kinetic approach

Although often used for soil studies, community level physiological profiles (CLPPs) have been rarely applied to compost, probably for the lack of standardized methodology. Recently, however, CLPPs have been proposed as a tool to assess the degree of maturity of compost. One of the major problems is that the rate of colour development is a non-linear process related to both time and inoculum density. The aim of this work was to investigate the suitability of data interpretation based on the kinetics of colour formation. Extracts from compost samples of different age were diluted in four different dilutions and inoculated into Biolog Ecoplates. Optical density (OD) in wells was measured (592 nm) every 8 h for 7 d. Kinetic parameters were estimated by fitting the curve of OD vs. time to a logistic growth equation. Principal component analysis (PCA) clearly showed an effect of dilution on CLPPs, but the pattern of ordination of compost by age groups was generally the same in the different dilutions. If parameters were grouped for classes of compounds, discriminant analysis was able to separate samples of different age. In particular, phenolic compounds were the class of components that most significantly contributed to sample classification.

Solid Phase Spectrophotometric Determination of Traces of Arsenate and Phosphate in Water Using Polyurethane Foam Sorbent

A simple and sensitive method for the determination of arsenate and phosphate in the µg L−1 concentration range using solid phase spectrophotometry has been developed. The method utilizes the quantitative sorption of the heteropoly blue species of arsenomolybdic and phosphomolybdic acids by polyurethane foam (PUF) sorbent prior to direct spectrophotometric measurement of the solid phase. In the same time the difference in formation behavior between the arsenomolybdic and phosphomolybdic acids at different pH values of sample solution has allowed their determination in the presence of each other. A preconcentration factor of 150 has been achieved for 100 mL samples. The detection limits are 5.4 and 1.66 µg L−1 for arsenate/As and phosphate/P, respectively and the working analytical ranges are from 5.4–54 µg L−1 and 1.6–40 µg L−1 respectively. The different experimental parameters such as rate of color development, acidity of solution and the analyte concentration have been thoroughly investigated. Analysis of natural water samples has been performed.