Absorbance of ninhydrin solution

Table II. Absorbance of Ninhydrin Solution Obtained from Silk Fabrics After...

Figure 4. Absorbance of ninhydrin solution obtained from fabric 605 (Lots 1 and 2) after heating at 150 °C as a function of fiber concentration. Key open symbols, Lot 1 filled symbols, Lot 2.

Figure 7. Absorbance of ninhydrin solution obtained from fabric 605 (Lot 2) as a function of irradiation time.

Absorbance of ninhydrin solution silk fabrics after heating, 120-22,125 silk fabrics exposed to light, 123-24 Accelerated aging of cellulosic textiles, effect of... 

Ninhydrin Assays. Ninhydrin tests were performed using a modified procedme of Taylor et al. " APS Silica (10-75 mg) of various loadings (0.857, 0.571, and 0.343 mmol NH2/g Silica) was added to phosphate buffer (5 mL, 100 mM, pH 6.5), and 1 mL of a 5% w/v solution of ninhydrin in ethanol was added to the sluny. After stirring for an hour in a boiling water bath, the mixture was allowed to cool slowly to room temperature. The silica was then filtered and washed three times with 70°C distilled water. The filtrate was collected, added to a volumetric flask, diluted to 100 mL, and the absorbance of this solution at 565 mu was measured using a UV-visible spectrophotometer. The reference solution was prepared as above with unmodified amine-free silica. Calibration standards were prepared with aliquots of a 1 mg/mL solution of APS in ethanol. 

Dried peptidyl resin (2-10 mg) was placed in a test tube and the weight determined to the nearest 0.1 mg. To this tube and a blank tube was added 76% phenol/EtOH (w/w, 4 drops), 0.0002 M KCN/ pyridine (8 drops), and 0.28 M ninhydrin/EtOH (4 drops). The test tubes were heated at 100 °C for 7 min and then diluted to 5 mL with 60% EtOH. The tubes were mixed thoroughly and the resin allowed to settle. The absorbance of the solutions was obtained at 570 nm. The pmol g of amine was calculated using the following equation ... 

In the ion-exchange technique, separated amino acids exiting (eluting) from the end of the chromatography column mix with a solution of ninhydrin and undergo a rapid reaction that produces an intense purple color. The color is detected by a spectrometer, and a plot of elution time versus spectrometer absorbance is obtained. 

Rao et al. [46] reported the use of a spectrophotometric method for the determination of primaquine phosphate with ninhydrin. Standard solution of 0.01% primaquine phosphate solution (3 mL) or solution prepared from the drug or its tablets was mixed with 2 mL of water, 5 mL of 2-methoxyethanol and then with 4 mL of ninhydrin reagent. The mixture was boiled for 35 min, and, after cooling and dilution to 25 mL with water, the absorbance was measured at 570 nm versus a reagent blank. Beer s law was obeyed from 4 to 20 pg/mL with recoveries of 99.4— 100.2% for 25 mg of primaquine phosphate. 

Table IV. Absorbance of the Ninhydrin Solution Obtained from Treated and Untreated Silk Fabric Lot 2 After Heating...

Ninhydrin Assay for Adsorbed Proteins. Measurements were made by a colorimetric procedure based on the reaction of ninhydrin with amino acids (25). The films were hydrolyzed in 5 ml of 2.5N NaOH for 2 hrs in capped plastic tubes in a boiling water bath. Then 1.5 ml of glacial acetic acid was added and mixed next I ml of ninhydrin reagent was added and mixed. [The reagent was three times more concentrated in ninhydrin, SnCb, and citrate than prescribed by Moore and Stein (25)]. The tubes were capped and boiled 20 mins more. The solution was clarified by centrifugation, and the absorbance read immediately at 570 nm on a Beckman DB spectrophotometer. If necessary, the sample was diluted with 50-50 2-propanol-water. Calibration curves (absorbance vs. fig of protein) were constructed in the 0-30 and 0-100 fig range with known amounts of each type of protein subjected to this same analysis procedure. 

In a new approach for the direct determination of free and bound sialic acid, an acidic ninhydrin assay has been proposed [263]. Heating of solutions of sialic-acid-containing material with ninhydrin/acetic acid/37% HCl at 100 C yields a stable chromophore, the absorbance of which can be measured at 470 nm. 

Their relative abundance can be determined by first treating the amino acids with ninhydrin (see Fig. 3-56) to create a colored derivative, or fluorescamine to generate a fluorescent derivative. The concentration of each amino acid is proportional to the absorbance (or fluorescence) of the solution. The technique was originally used to help identify proteins, but it is now more commonly used as the most accurate way to determine the concentration of a protein sample. 

Reagents which form a derivative that strongly absorbs UV/visible radiation are called chromatags an example is the reagent ninhydrin, commonly used to obtain derivatives of amino acids which show absorption at about 570 nm. Derivatisation for fluorescence detectors is based on the reaction of non-fluorescent reagent molecules (fluorotags) with solutes to form fluorescent... 

N-a-acety1-L-lysine (0.5 mmole) and glucose (1.0 mmole) are dissolved in 1 ml 0.1 M K2HP0 buffer solution. The solution is heated in a closed vessel for 5 h at 100°C. Then the solution is made 6 N with HC1 and heated at 105° for 24 h. The hydrolysate is evaporated in vacuo. A solution of the residue in 20 ml water can be used for the TLC production of furosine spots. For quantitative evaluation the same absorbance was assumed for the ninhydrin reaction product both arginine and furosine. 

In an amino acid analyzer, the hydrolysate passes through an ion-exchange column. The solution emerging from the column is treated with ninhydrin, and its absorbance is recorded as a function of time. Each amino acid is identified by the retention time required to pass through the column. 

The listed amount of methacrylic acid was contained in the HEM A monomer used to form the poly (HEM A)/Silastic hydrogels, which had 20% grafted poly(HEMA). These hydrogels were equilibrated for 45 hrs at 37°C in 0.5mg/ml protein solutions in the listed solvents and then rinsed in the equilibration solvent, using decantation and dilution and 15 min of stirring. Ninhydrin assays were then used to determine absorbed protein. 

Six to eight standard dilutions in an appropriate concentration range for each amino acid are prepared 2 ml of amino acid solution and 2 ml of buffered ninhydrin are mixed in a test tube, heated in a boiling water bath for 15 min, cooled to room temperature, and 3 ml of 50% ethanol added. The extinction is read at 570 nm (or 440 nm for proline) after 10 min. Standard plots of concentration versus absorbance are drawn for each amino acid. The scraped layer corresponding to each spot is extracted with 70% ethanol in a known minimum volume, and ninhydrin reaction is performed followed by spectrophotometry. The concentration of unknown samples is read from the standard plots. TLC/den-sitometry was used to determine 0.5 mg/L of phenylalanine in blood serum as an indicator of phenylketonuria (181). 

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