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Thin-Layer Chromatography in Food Analysis
Published in Bernard Fried, Joseph Sherma, Practical Thin-Layer Chromatography, 2017
In this procedure, the area of the spot is marked with pencil about 0.5 cm out from the edge of the spot. The encircled area is scraped off with a steel spatula onto a piece of glassine paper and carefully transferred to a centrifuge tube and extracted into a suitable solvent (5–10 ml) by shaking. Centrifugation is performed at high speed until the solution is clear (5 min). The clear solution is estimated using a spectrophotometer to determine the absorbance of the sample at the maximum absorbance or fluorescence wavelength of the component. Areas from the unused portion of the same plate, equal to that used for the sample, should be scraped and processed in the same manner, establishing the absorbance or fluorescence zero point. The standard curve can be obtained in the same manner by scraping, eluting, and measuring a series of standards.
Laboratory tutorials
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2018
Spectrophotometers are useful because of the relation of intensity of color in a sample and its relation to the amount of solute within the sample. For example, if you use a solution of red food coloring in water and measure the amount of blue light absorbed when it passes through the solution, a measurable voltage fluctuation can be induced in a photocell on the opposite side. If the solution of red dye is now diluted to half its original concentration by the addition of water, the color will be approximately half as intense and the voltage generated on the photocell will be approximately half as great. Thus, there is a relationship between the voltage and the amount of dye in the sample.
Field Investigation Techniques for Potentially Contaminated Sites
Published in Kofi Asante-Duah, Management of Contaminated Site Problems, 2019
In practice, if the antibodies are coated on the inside surface of the test tube, the sample and enzyme conjugate are combined directly in the test tube; if the antibodies are coated on magnetic or latex particles, a carefully measured amount of the solution that contains the coated particles is added to the test tube. Measured amounts of both the enzyme conjugate and the actual sample containing the target analyte are added to the test tube. The action is a timed incubation step; during the incubation, the analyte in the sample competes with the known amount of labeled antigen in the enzyme conjugate for the limited number of antibody binding sites. After incubation, the excess unbound enzyme conjugate is washed (removed) from the test tube. The amount of the enzyme conjugate that remains in the test tube is measured through the use of a colorimetric reaction. An enzyme substrate and a chromogen are added to the test tube to cause the formation of the color; this action is also a timed step, after which a solution is added to stop the formation of color. Because the amount of bound enzyme conjugate determines the amount of color, the amount of color is inversely proportional to the amount of analyte present in the sample. The color of the sample can be compared visually with a zero solution or blank for a “yes or no,” or qualitative, result. A semiquantitative result can be obtained by using a differential photometer to compare the degree of light absorbance of a sample with that of a standard or standards. Finally, a quantitative result can be obtained by generating a calibration curve of absorbance compared with concentration by using a spectrophotometer, computer software, calibration standards, and a zero solution. The light absorbance of the sample can be read from the spectrophotometer and converted into a concentration.
Emulsion system, demulsification and membrane technology in oil–water emulsion separation: A comprehensive review
Published in Critical Reviews in Environmental Science and Technology, 2023
Yuying Deng, Min Dai, Yanni Wu, Changsheng Peng
Moreover, the tiny droplets (smaller than the pore size of the membrane) in the emulsion can easily penetrate through the membrane under the additional pressure, which causes the partially soluble emulsifier to enter the filtrate (Wang et al., 2021; Zhang et al., 2014). By measuring the emulsifier concentration in the filtrate, not only the actual oil content in filtrate can be calculated, but also the membrane demulsification and separation effect can be inferrred. The methods used to determine emulsifier concentration reported in the literature include spectrophotometry, flow injection, two-phase titration, chromatography, thin layer chromatography, electrochemical, resonance scattering, capillary electrophoresis, and oscillopolarography methods (Chen et al., 2014; Dong & Meng, 2019; Lü et al., 2015). Among these, spectrophotometry is widely used because of its advantages of high detection sensitivity, simple operation, low test cost and in-situ monitoring.
Combined experimental and molecular dynamics removal processes of contaminant phenol from simulated wastewater by polyethylene terephthalate microplastics
Published in Environmental Technology, 2022
Christian Ebere Enyoh, Qingyue Wang
In order to calculate the concentration using the calibration curves and Beer–Lambert law, the absorbance from the spectrophotometer was employed. Data analysis was carried out using Microsoft Excel 2013, Origin Pro 8 (USA), and SPSS Version 23 (IBM, UK). The average and range of observations made in triplicate for each experiment are noted. Equation (1) was used to calculate the percentage of sorbate removed from the aqueous solution (% R) at a particular time t. Equation (2) was used to calculate the amount of sorbate adsorbed at equilibrium per unit mass of each PET MP. Equation (3) was used to determine the adsorption capacity for each sorbent at any time t. (3).
The use of metal hydroxide sludge (in natura and calcined) for the adsorption of brilliant blue dye in aqueous solution
Published in Environmental Technology, 2019
Ana Maria Salgueiro Baptisttella, Andressa Aziz Diniz Araújo, Matheus Caldas Barreto, Vivian Stumpf Madeira, Mauricio Alves da Motta Sobrinho
The adsorption assays to evaluate the influence of the initial pH of the solution containing NB 180 dye on the quantity adsorbed were carried in batch experiments, run in duplicate. This analysis consisted in investigating the initial pH of the solution of NB 180 dye with a concentration of 20 mg.L−1 at a range of 4–8, using a dosage of 5 g.L−1 (0.25 g / 50 mL). The solution pH was adjusted using a solution of hydrochloric acid (HCl – 0.1 mol.L−1) and sodium hydroxide (NaOH – 0.1 mol.L−1). After three hours of stirring at 200 rpm and at a temperature of 25°C, the samples were centrifuged under 4000 rpm for 3 min. The final concentration of the solution was determined using a calibration curve through the absorbance data measured using a spectrophotometer.