Color Development Time Research Articles

2D Fe/Co-MOF/SOX cascade reactors for fast noninvasive detection of sarcosine level in prostate cancer urine

Sarcosine plays a key role in screening for early prostate cancer. However, the several already reported peroxidase mimics immobilized with sarcosine oxidase (SOX) utilized to detect uriary sarcosine still have some limitations such as complex synthesis process, using of expensive heavy metals to mimic enzyme activity and long color development time. Herein, an inexpensive peroxidase-like 2D Fe/Co-MOF nanosheet was prepared by a simple solvent modulation method. The resultant 2D Fe/Co-MOF nanosheets have strong peroxidase activity, with its Vmax value for H2O2 of 15.3 × 10-8 M/s, being 1.76 times that of HRP. Then, using the 2D Fe/Co-MOF as a peroxidase model for anchoring natural SOX to construct 2D Fe/Co-MOF/SOX , which can act as a cascade reactor for detection of sarcosine. Considering the above properties, a platform for the detection of sarcosine was built based on a colorimetric method. Because of presence of the high ratio of Fe2+ caused by the electron transfer from Co2+ to Fe3+, large specific surface area and plentiful active sites, 2D Fe/Co-MOF/SOX with TMB (3,3′,5,5′-tetramethylbenzidine) colorimetric reagent could have fast color development and can be applied conveniently and fastly in an early screening tool for prostate cancer patients. The sarcosine could be quantified by peroxidase activity with a detection range of 1–400 μM and a limit of detection (LOD) of 0.324 μM. More importantly, the average sarcosine concentration of 21.367 μM and 1.871 μM was detected in patient’s and normal urine (n = 5), respectively, which showed an excellent screening effect and a great potential in early prostate cancer.

수묵(⽔墨) 기법을 응용한 티타늄 구조색 발색 기법 연구

The purpose of this study is to present new color application possibilities using an anodizing device so that titanium, which is friendly to the human body and the environment, can be widely used in the art and design fields.In this study, it was found that controlling the appropriate viscosity of the glue that bonds titanium to paper is of utmost importance in order to develop the planned color. It was found that when the viscosity of the glue is low, the adhesion is weak, making it easy for the titanium to separate from the paper, and when the viscosity is high, the color development time is longer than normal. This study is a new structural color application method that has not been seen in the titanium anodization method until now. Through this study, we were able to confirm its usability in a variety of fields as well as art and design.

Research on the Influence of Thermal Decomposition of Magnesium Chloride Hexahydrate on the Preparation of Magnesium Oxide and Hydrated Magnesium Hydroxide

Magnesium chloride hexahydrate is an important intermediate product in magnesite processing. In order to promote the efficient utilization of magnesite resources, based on the pyrolysis interval of magnesium chloride hexahydrate, the relationship between magnesium oxide with different physicochemical properties and the apparent properties of hydrated magnesium hydroxide was studied. The results show that the effect of temperature on magnesium oxide sintering is stronger than that of holding time. With the increase of calcination temperature and the extension of holding time of magnesium chloride hexahydrate, the calcined product magnesium oxide was sintered into large particle size with the characteristic particle size D<sub>50</sub> of 33.89 μm. The crystal was distorted, the chemical activity deteriorated, and the color development time was up to 407 s. When hexahydrate magnesium chloride was calcined at 480 °C with 2 h, it decomposed almost completely. The product, magnesium oxide, consisted of uniformly distributed small coral rod-like particles with strong chemical reactivity and a color development time of 115 s. The particles were small and evenly distributed, with a characteristic particle size D50 of 1.36 μm, and the highest specific surface area reached 7.292 m<sup>2</sup>/g. The hydrated magnesium hydroxide particles had well-defined edges and corners, with a characteristic particle size D50 of 1.59 μm and a uniform particle size distribution.

P-chromophore stability of Mehlich-1 and Mehlich-3 under Braga & Defelipo or Murphy & Riley dosing methods

ABSTRACT The performance of colorimetric methods for P quantification has been overlooked by researchers for decades. We investigated the performance of two blue colorimetric methods for P quantification, Braga and Defelipo (B&D) and Murphy and Riley (M&R), using two commonly soil P extractants, Mehlich-1 (M1) and Mehlich-3 (M3). Specifically, we evaluated the color development time and its stability in different soil extractant solution proportions (1:1 or 1:4 v/v), the optimum wavelength, limits of detection, and element quantification. Our results indicate that M3 leads to lower limits of detection and quantification for both colorimetric methods, particularly for B&D. For M1, the volumetric ratio (1:1 or 1:4) did not influence color development and both B&D and M&R methods showed a fast color development. However, B&D showed greater color stability (from 5 to 600 min) and an optimum wavelength of 711 nm, while M&R was stable from 27 to 600 min an optimum wavelength of 889 nm. For M3 soil extractant, there are important issues, such as M&R being unstable and B&D presenting slow color development. In addition, the spectral profile obtained from soil extractant was different from the one obtained by the calibration curve without soil for both M&R and B&D. Therefore, the adoption of original methods on P quantification in M3 extracting solution represents a potential source of error, leading to wrong P fertilizer recommendations. Thus, the best option for P quantification in M3 extracts seems to be the use of Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES).

Rapid screening of inorganic arsenic in groundwater on-site by a portable three-channel colorimeter

Rapid screening of inorganic arsenic (iAs) in groundwater used for drinking by hundreds of millions of mostly rural residents worldwide is crucial for health protection. Most commercial field test kits are based on the Gutzeit reaction that uses mercury-based reagents for color development, an environmental concern that increasingly limits its utilization. This study further improves the molybdenum blue (MB) colorimetric method to allow for faster screening with more stable reagents. More importantly, a portable three-channel colorimeter is developed for screening iAs relative to the WHO drinking water guideline value (10 µg/L). Adding the reducing reagents in sequence not only prolongs the storage time to > 7 days, but also accelerates the color development time to 6 min in conjunction with lowering the H2SO4 concentration in chromogenic reagents. The optimal pH ranges from 1.2 to 1.3 and is achieved by acidifying groundwater to 1% (V/V) HCl. With detection limits of 3.7 µg/L for inorganic arsenate (iAs(V)) and 3.8 µg/L for inorganic arsenite (iAs(III)), testing groundwater with ∼10 µg/L of As has a precision < 20%. The method works well for a range of phosphate concentrations of 48–950 µg/L (0.5–10 µmol/L). Concentrations of total_iAs (6–300 µg/L), iAs(V) (6–230 µg/L) and iAs(III) (0–170 µg/L) for 14 groundwater samples from Yinchuan Plain, Pearl River Delta, and Jianghan Plain, are in excellent agreements (linear regression slope: 0.969–1.029) with the benchmark methods. The improved chemistry here lays the foundation for the MB colorimetric method to become a commercially viable screening tool, with further engineering and design improvement of the colorimeter.

Paper-Based Colorimetric Sensor for Hydrogen Peroxide Based Upon a Graphene Oxide/Platinum-Cobalt Nanocomposite

The peroxidase-like properties of a graphene oxide/platinum-cobalt nanocomposite and the rapid color development mechanism of 3,3′,5,5′-tetramethylbenzidine (TMB) through the decomposition of ·OH from H2O2 were utilized to prepare a nonlabelled, simple, and sensitive paper-based colorimetric sensor. This sensor allows visualization of the results and instantaneous detection, enabling quantitative measurement of H2O2. The graphene oxide/platinum cobalt composite was synthesized using a two-step procedure. Its properties were investigated using transmission electron microscopy (TEM), Raman spectroscopy, and energy-dispersive X-ray spectroscopy (EDS). The composite was subsequently transferred onto a paper substrate to create the colorimetric sensor. The optimal catalytic conditions were a composite concentration of 201.17 µg/mL, a color development time of 3 min, a TMB concentration of 2 mmol·L−1, and a pH of 4. Using the optimal conditions, the paper-based colorimetric sensor has a linear range for H2O2 from 1.0 × 10−5 to 0.1 mol·L−1, with a limit of detection of 1.0 × 10−6 mol·L−1 which is comparable or better than comparable methods. This paper-based colorimetric sensor has potential applications for the rapid determination of hydrogen peroxide.

Quantitative determination of Hexavalent chromium using a microtiter plate: Analytical performance, operational efficiency, and fixation of a colorimetric reagent in the plate wells

Efficient and sensitive trace determination of Cr(VI) in small sample volumes is an important issue for environmental protection and the sustainable development of industries. A microtiter plate and a microplate reader have been applied to the colorimetric determination of Cr(VI) using 1,5-diphenylcarbazide (DPC) as indicator, to realize an efficient method with low detection limits. The DPC reagent was fixed on the plate well and the time for color development was significantly reduced (<1 min) compared to conventional methods by using small volume reaction vessel which made it possible to perform determinations of Cr(VI) in a short period of time. The lower limit of quantification of 0.021 mg/L obtained with this method is better than that of the microplate method reported previously, and is comparable to general analytical methods with large sample volumes. In addition, when the chromogenic reagent is fixed to the plate with a water-soluble polymer, the lower limit of quantitation is comparable as that of the unfixed reagent. This results in improved instrument portability and more efficient analytical operations.

Construction of a highly efficient DNA nanotube sensor with peroxide-like activity.

The G-quadruplex/heme complexes are special DNA-based artificial metalloenzymes with peroxidase-like activity and are widely used in biosensing and biocatalysis. However, their peroxidase-like activity is not satisfactory. Due to the high programmability and good stability of DNA, DNA as a scaffold material is promising for enhancing the activity of artificial metalloenzymes. In this work, an effective DNA nanotube-based peroxidase was constructed using a self-assembly strategy. To improve the activity of G-quadruplex/heme complexes, a new method for the construction of G-quadruplex/heme complex arrays was proposed in a simple and inexpensive way. By designing the toes of DNA nanotubes as G-quadruplexes, G-quadruplex arrays could be formed on pure DNA nanotubes, and then the G-quadruplex arrays bind to heme to form a nanotube-supported DNAzyme termed as DNTzyme. Agarose gel electrophoresis, circular dichroism, and fluorescence microscopy were used to characterize DNTzyme. What is more, because the loading of DNAzyme on DNA nanotubes can increase their biological stability, a hydrogen peroxide detection sensor was constructed using the enhanced enzymatic activity and excellent stability of DNTzyme. The sensor could accurately and efficiently detect peroxide and show enhanced fluorescence with a detection limit of 49 nM for H2O2 and 1.4 μM for TBHP, and a color development time of about 5 min. This sensor is expected to have applications in bio-detection, biocatalysis, and drug delivery.

Optimization of the molybdenum blue method for estimating the antioxidant activity of natural products

Context: The present experimental conditions of the molybdenum blue spectrophotometric method, used for antioxidant activity estimation, promote the degradation of flavonoids with potential interferences in the above determination. Aims: To evaluate the effects of physicochemical factors on the formation of the complex for optimizing the total antioxidant activity method to better estimate the antioxidant activity of natural products. Methods: A 34-1 fractional experimental design was applied. Independent variables were temperature, color development time, type of acid and acidity, and the dependent variable was the absorbance of the complex. The concentration of ammonium molybdate tetrahydrate and sodium hydrogen phosphate remained constant throughout the study. The effects of the reducing agent and its concentration were studied independently. The effect of acidity in a wide range of values, the color development time considering temperature, the influence of co-solvents, and the antioxidant activity of various natural metabolites were also evaluated. Results: Acid concentration and temperature greatly influenced the complex formation, making the type of acid and incubation time less significant. Ascorbic acid showed a shorter color development time than reference metabolites. Ethanol negatively influenced the amount of complex formed. The proposed conditions for developing this method were: type of acid, HCl or H2SO4; acid concentration 0.01 N; incubation temperature 65°C; and incubation time 40 min. Under these experimental conditions, the ranking order of antioxidant activity was pyrogallol&gt;quercetin&gt;ascorbic acid&gt;gallic acid&gt;rutin. Conclusions: The new experimental conditions for the molybdenum complex assay give a more reliable determination of the antioxidant activity of natural products.

Изучение реакции ионов Cu(II) с N-(бензоил)-N'-(фенилсульфонил)гидразином в аммиачных средах спектрофотометрическим методом

The reaction of complexation of N-(benzoyl)-N'-(phenylsulfonyl)hydrazine with Cu(II) ions in an ammonia medium has been studied. The absorption spectra of the reagent and its complex with Cu(II) ions have been recorded and analyzed. The optimal conditions for the formation of the complex compound were found: the pH range of complex formation; optimal time for color development; amount of photometric reagent. Under optimal conditions for the complex formation of BPSH with Cu(II) ions, a calibration graph was constructed. The Bouguer-Lambert-Beer law is fulfilled in the range from 0,5 to 1,75 mg Cu(II) in 25 ml of solution. The true (19389) and apparent (4708) molar light absorption coefficients were calculated. The methods of saturation, equilibrium shift, curve intersection, isomolar series, and conductometric titration were used to determine the molar ratios in a solution of a complex compound – [Сu(II)]:[BFSH] = 1:1 and 1:2. According to the Babko method, the conditional stability constant of the complex was calculated – 2,45∙1013. The convergence and correctness of the spectrophotometric technique were determined by the method of mathematical statistics.

Разработка метода прямого экстракционно-спектрофотометрического определения молибдат-ионов в системе антипирин – сульфосалициловая кислота – вода

The stratified system antipyrine - sulfosalicylic acid - water eliminates the use of toxic organic solvents, allows for the group extraction of macro- and micro-quantities of elements into a small volume (~ 2 ml) water-organic phase, in this phase many photometric reagents are easily dissolved. The extraction-spectrophotometric method for the determination of molybdate-ions with phenylfluorone has been developed. The optimal conditions for the formation of a colored compound with an organic reagent have been determined: light absorption maximums; optimal time for color development; photometric reagent amount, linearity range of the calibration graph. In optimal conditions for the complexation of phenylfluorone with MoO42- (λ = 526 nm, τ = 20 min, CR = 5·10-5 mol/l), a calibration graph is constructed. The Bouguer-Lambert-Beer’s law is fulfilled in the range from 10 to 60 μg Mo(VI)/20 ml. The molar coefficient of light absorption is calculated, which is 9.2∙104. The effect of interfering ions on the direct extraction-spectrophotometric determination of molybdate ions is studied. It is found that the determination of 50.0 μg of molybdenum(VI) does not interfere with: 5000 - fold molar excess of Ni(II), Co(II), Cr(III), Mn(II), Cd(II), Zn(II), Pb(II); 500 - fold molar excess of Re(VII); 1 - fold molar excess of In(III), W(VI).

Спектрофотометрическое определение ионовCo(II) сN-(2-гидроксибензоил)-N'-(п-тозил)гидразином в аммиачных средах

A technique has been developed for the spectrophotometric determination of Co(II) ions with N-(2-hydroxybenzoyl)-N'-(p-tosyl)hydrazine (GBSH) in an ammonia medium. The absorption spectra of the reagent and its complex with Co(II) ions have been recorded and analyzed. The optimal conditions for the formation of the complex compound were found: the pH range of complex formation; optimal time for color development; amount of photometric reagent. Under optimal conditions for the complexation of GBSG with Co(Ⅱ) ions, a calibration graph was constructed. The Bouguer-Lambert-Beer law is fulfilled in the range from 0.3 to 2.4 mg Co(II) in 25 ml of solution. The true and apparent molar light absorption coefficients were calculated. The true molar coefficient of light absorption of the complex compound GBSG with Co(Ⅱ) ions in an ammonia medium is 750. The molar ratios in the solution of the complex compound [Co(Ⅱ)]:[GBSG] = 1:1 and 1:2. The conditional stability constant of the GBSG complex with Co(Ⅱ) ions was calculated using the Babko method and it is 3.24∙1012. The convergence and correctness of the spectrophotometric technique were determined by the method of mathematical statistics.

Spectrophotometric determination of iron (III) catalyst in organic compound chlorinations

In the science or industrial practice of chemical processes, iron (III) is sometimes used as a catalyst in organic compound chlorinations due to its effectiveness and low cost. Thus, a fast and easy method of determination in the system is useful especially when metallic iron is used as a precursor which is readily converted into iron (III) chloride by the gaseous chlorine used in the chlorination reactor. In the latter case, the determination of the produced catalytically effective iron (III) is a prerequisite for controlling the kinetic progress of chlorination. In this work, a method for the spectrophotometric determination of iron (III) chloride in organic media after complexation with methyl ethyl ketone is investigated. The formation of a strong o-complex of iron (III) with methyl ethyl ketone allows direct determination of iron at 360 nm.Beer’s law is valid up to absorbance 2.42, where the iron (III) concentration is 20.7 mg·L-1, with molar absorptivity (e) equal to 6.532×103 L·mol-1·cm-1 and Sandell’s sensitivity 8.5×10-3 ug·cm- 2. Standing time for color development is of the order of a few seconds and stability of color measurements exceeds 12 months. The method may be used among other applications in organic compounds chlorinations catalyzed by iron. These systems are complicated due to the coexistence of various complexes. Nevertheless, the method proposed being simple, fast, and not depending on the composition of the chlorination mixture and the amount of methyl ethyl ketone added was found to be suitable.

Optimization of the salicylate method for ammonia quantification from nitrogen electroreduction

• The salicylate method was optimized for aqueous and non-aqueous samples. • The factors that affect the quantification results were identified. • The proposed methods exhibit a good reproducibility for a given reagent brand. • The detailed experimental procedures are included in this work. The salicylate method is one of the colorimetric methods that is used for ammonia quantification in nitrogen (electro)fixation. While the salicylate method offers advantages in that it avoids working with toxic reagents and does not generate toxic fumes, ammonia quantification is sensitive to the exact experimental conditions (e.g. color development time, exposure to light, etc.) and to a number of interferences (e.g. pH of the samples, presence of interferents, etc.), which leads to reproducibility problems. In this work, the influence of different factors on the ammonia quantification in Nitrogen Reaction Reduction (NRR) using the salicylate method was examined, both in aqueous media and in non-aqueous media. The detailed experimental procedures presented in this work, provide an optimized reference method for quantifying ammonia in NRR screening experiments using the salicylate method.

РАЗРАБОТКА СПЕКТРОФОТОМЕТРИЧЕСКОЙ МЕТОДИКИ ОПРЕДЕЛЕНИЯ ИОНОВ Cu(II) C N-(2-ГИДРОКСИБЕНЗОИЛ)-N'-(п-ТОЗИЛ)ГИДРАЗИНОМ В АММИАЧНЫХ СРЕДАХ

A spectrophotometric method for the determination of Cu (II) ions with N- (2-hydroxybenzoyl) -N '- (p-tosyl) hydrazine (GBSH) in ammonia media has been developed. The optimal conditions for the formation of a complex compound are found: the wavelength of maximum light absorption; pH complexation; optimal time for color development; the amount of photometric reagent. Under optimal conditions of complexation of GBSG with Cu (Ⅱ) ions (λ = 401 nm, pH = 9.2, τ = 30 minutes, VGBSG = 3.75 ml), a calibration graph is constructed. The Bouguer-Lambert-Beer law is fulfilled in the range from 0.13 to 1.59 mg Cu (II) / 25 ml. The true molar light absorption coefficient of the complex compound of HBSG with Cu (Ⅱ) ions in the ammonia medium was 1480. The molar ratios in the solution of the complex compound were determined by the methods of saturation, shift of equilibria and conductometric titration - [Cu (Ⅱ)]: [HBSG] = 1: 1. According to Babko's method, the conditional constant of stability of the GBSG complex with Cu (Ⅱ) ions was calculated and it was 4.4 × 1010. The reproducibility and relative error of the developed photometric technique were determined by the method of mathematical statistics.

Temperature impact on monochloramine, free ammonia, and free chlorine indophenol methods.

A commercial colorimetric indophenol (IP) method is used for determining monochloramine (NH2Cl) concentrations for process control in chloraminated public water systems and chloramine-related research. The NH2Cl - IP method excludes some quality control procedures typically included in drinking water methods and is not approved by the United States Environmental Protection Agency (U.S. EPA) for compliance monitoring. Therefore, the authors developed and validated a more complete NH2Cl-IP method, building on the commercial technique, as a candidate for future approval. During method development, temperature impact on color development was investigated. Color development time increased as temperature decreased. Below 20 °C, times needed for full color development were greater than those reported in the commercial method, reaching nearly three times longer at 5 °C. This observed temperature dependence also applies to free ammonia and free chlorine indophenol methods. To avoid measurement errors of samples analyzed below 20 °C, use of reaction times determined in this study is recommended for these indophenol methods.

Verification of Suppression of Color Tone Variation at the Time of Stainless Steel Chemical Color Development

Verification of Suppression of Color Tone Variation at the Time of Stainless Steel Chemical Color Development

Analysis of influencing factors for the determination of ammonia nitrogen in water by spectrophotometry

The research is supported by a Project Funded by the brand professional project form Yancheng teachers college (2016) and the teaching reform and practice of medicinal chemistry (2018YCTUJGY006) and the innovation and entrepreneurship training program for college students in jiangsu province （ 201910324016Z ） Abstract The content of ammonia nitrogen in water was determined by national standard method - nessler's reagent spectrophotometry. Through comparison, it was found that the method of reagent configuration, the amount of reagent, the detection wavelength, the color development time and the temperature had an impact on the analysis results in the ammonia nitrogen measurement in water by the reagent spectrophotometry. Based on the experimental results, the factors influencing the determination of ammonia nitrogen by spectrophotometry with nessler's reagent were discussed. Keywords Nessler's reagent spectrophotometry, Ammonia nitrogen, Influencing factors, Blank value, ABS value, Correlation coefficient. DOI : 10.7176/JEP/10-31-08 Publication date: November 30 th 2019

Identification of Harvest Maturity Indicators for ‘Hass’ Avocado Adaptable to Field Conditions

‘Hass’ avocado (Persea americana) is a fruit in high demand in international markets, and Colombia is expanding its export to the United States. Avocado quality and shelf life are related to its harvest time. However, there is not enough information on harvest indicators in Colombia that allow producers to adequately harvest fruit to comply with market requirements. Therefore, the aim of this study was to estimate maturity indicators during two harvest periods. We harvested fruit between the years 2016 and 2017 in eight farms distributed in three regions of the Department of Antioquia, Colombia, and selected those in the postanthesis stages. We assessed variables such as fruit color, weight, dimensions, oil content (OC), and dry matter (DM). The results were analyzed using simple and multiple regressions as well as by principal component analysis (PCA). The results showed a high linear relation between DM and OC (R2 ≥ 78.88) and a significant relation between OC, rainfall, fruit development time, and environmental temperature. Nondestructive indicators that allow the establishment of DM in the field (R2 ≥ 73.57) varied according to the region and included fruit color (L*, b*), volume (P ≤ 0.05), and fruit development time. These indicators could reduce maturity heterogeneity during the harvest period.

Measurement of Chlorine Dioxide in Water by DPD Colorimetric Method

In order to solve the problems of chlorine dioxide in water by DPD colorimetric method, this paper discusses the effects of the formulation, temperature, color development time and amount of color reagent on the measurement process, improving the on-line instrument for domestic and drinking water in chlorine dioxide measurement precision and accuracy.