Search results
Results from the WOW.Com Content Network
DPPH-I (m.p. 106 °C) is orthorhombic, DPPH-II (m.p. 137 °C) is amorphous and DPPH-III (m.p. 128–129 °C) is triclinic. [2] DPPH is a well-known radical and a trap ("scavenger") for other radicals. Therefore, rate reduction of a chemical reaction upon addition of DPPH is used as an indicator of the radical nature of that reaction.
McIlvaine buffer is a buffer solution composed of citric acid and disodium hydrogen phosphate, also known as citrate-phosphate buffer.It was introduced in 1921 by the United States agronomist Theodore Clinton McIlvaine (1875–1959) from West Virginia University, and it can be prepared in pH 2.2 to 8 by mixing two stock solutions.
Preparation [ edit ] Dragendorff's reagent is prepared by mixing a concentrated solution of potassium iodide with a solution of bismuth subnitrate in a diluted acid ( acetic acid or tartaric acid , hydrochloric acid or sulfuric acid is rarely being used) as a low pH is mandatory for this reagent.
The Trolox equivalent antioxidant capacity (TEAC) assay measures the antioxidant capacity of a given substance, as compared to the standard, Trolox.Most commonly, antioxidant capacity is measured using the ABTS Decolorization Assay.
Prepare a series of standards diluted with 0.15 M NaCl to final concentrations of 0 (blank = No protein), 250, 500, 750 and 1500 μg/mL. Also prepare serial dilutions of the unknown sample to be measured. Add 100 μL of each of the above to a separate test tube (or spectrophotometer tube if using a Spectronic 20).
To apply this method, analysts prepare multiple solutions containing equal amounts of unknown and spike them with varying concentrations of the analyte. The amount of unknown and the total volume are the same across the standards and the only difference between the standards is the amount of analyte spiked.
In titrations, the concentration of analyte in solution can be determined by titrating the standard solution against the analyte solution to determine the threshold of neutralization. [9] For example, to calculate the concentration of hydrogen chloride, a standard solution of known concentration, such as 0.5 M sodium hydroxide, is titrated ...
The color intensity of the resulting solution is then measured by a colorimeter and checked against a calibration curve to determine the nitrite ion concentration. [ 4 ] To analyze nitrate concentrations quantitatively, the sample is first passed through a copper-cadmium column to reduce the nitrate ions quantitatively to nitrite ions, and the ...