Of ninhydrin

D) Spraying solution. A solution of 0-2 g. of ninhydrin in a mixture of 99 ml. of redistilled n-butanol and i ml. of glacial acetic acid. 

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. 

The reaction of ninhydrin with an < -amino acid occurs in several steps. 

Draw resonance forms for the purple anion obtained by reaction of ninhydrin with an n-amino acid (Problem 26.53). 

The percentages of amino acids in silk fibroin which Poison et al. (224) found by direct visual and indirect photometric analysis of ninhydrin paper-partition chromatograms are shown in Table VII. The percentages obtained for alanine, glycine, and serine appear to be reasonably accurate, inasmuch as they agree closely with those found by other methods. It would be of interest to determine alanine by the microbiological method reported recently by Sauberlich and Baumann (238), in view of the widely different values found for this amino acid by the described ninhydrin-chromatographic procedure and the selec-... 

Amino Acids. Early observations on the liberation of amino acids by plant roots were reviewed by Loehwing (94), Rademacher (121), and Borner (12). Free amino acids have been isolated from soil fractions (119), and the excretion of a variety of ninhydrin-positive compounds by plant roots has been demonstrated under controlled conditions by Katznelson et al. (18), Rovira (121), and Pearson and Parkinson (115). 

Treatment of ninhydrin 431 with excess allyltrimethylsilane 82 and triflic acid in acetonitrile affords dehydrated ninhydrin 660 in 55% yield and the O-silylated product 661 in 18% yield [43] (Scheme 5.59). 

Prepare a 40% solution of KI prepare a 1.7% solution of bismuth subnitrate in 20% acetic acid mix 5 ml of the first solution with 20 ml of the second solution add 75 ml of H2O spray the plates and warm Prepare a 0.2% solution of ninhydrin in n-butanol and add 3-ml acetic acid spray plates and heat for 3 to 5 min at 100 to 110°C... 

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. 

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. 

With a solution of ninhydrin in pyridine, 4(5)-aminoimidazole (25 R = H) gave a grass-green color, and with ferric chloride solution in acetic acid a purple coloration was observed. Acidic solutions of bromine and potassium permanganate were decolourized by 4(5)-aminoimidazole (25 ... 

FIGURE 5.6 Reaction of ninhydrin (trioxohydrindene hydrate) with the amino group of a bound residue (A) generates the Schiff s base. Hydrolysis after shift of the double bond generates the aldehyde and another amine which reacts (B) with a second molecule of ninhydrin to give an equilibrium mixture of the anion depicted and its tetraoxo form with a maximum of absorbance at 570 nm. 

Materials Required Silica gel-G mobile-phase (glacial acetic acid water butan-l-ol 20 20 20 60) 100 ml solution (1) dissolve 0.1 g of sample in 5 ml of 2 M ammonia solution (2) dilute 1 ml of soln. (1) to 50 ml with water solution (3) dilute 5 ml of solution (2) to 20 ml with water Solution (4) dissolve 10 mg of glutamic acid EPCRS in sufficient water to produce 50 ml solution (5) dissolve 10 mg of glutamic acid EPCRS and 10 mg of aspartic acid EPCRS in sufficient water to produce 25 ml ninhydrin solution (0.2% w/v solution of ninhydrin in a mixture of 95 vols. of butan-l-ol and 5 vols of 2 M acetic acid ) 50 ml ... 

Ninhydrin assay. Our method to determine reactivity towards ninhydrin was a modification of a method described previously (Moore and Stein, 1954 Moore, 1968). Briefly, dried samples were dissolved in 0.10 ml 0.1 M acetic acid and mixed with an equal volume of ninhydrin reagent (Sigma). After 15 minutes in a boiling water bath, samples were diluted with 0.80 ml ethanol/water (1 1 by vol.) and measured for absorbance at 550 nm on a flow-through spectrophotometer (Vitatron). Standards containing 0-0.6 mM leucine in 0.1 M HAc were included. Values were therefore calculated as leucine-equivalents. 

Solid enols such as dimedone (255) are able to substitute one of the hydroxyl groups of ninhydrin (254) upon milling and give a quantitative yield of the... 

The easy access of a hydroxy group of ninhydrin (254) to its substitution and the presence of the carbonyl groups makes this highly reactive compound an interesting starting point for cascade reactions with amino compounds. These have been mechanistically investigated with AFM on six different faces of 254 and strictly relate to the crystal packing [94]. 

To perform the ninhydrin test a solution of ninhydrin in ethanol or acetone (0.2% w/v) is sprayed lightly over the plate. Brown to purple colors develop slowly (within 1-2 min) upon heating to 60-90 °C. The spray is stable for several weeks. 

The electron-rich thiophene ring system can be annelated by intramolecular Friedel-Crafts acylation reactions to give fused thiophenes <99IJC648, 99JMC2774>. The synthesis of a thiophene isostere of ninhydrin involved an intramolecular Friedel-Crafts acylation <99SL1450>. Specifically, treatment of thiophene 86 with thionyl chloride followed by aluminum chloride gave annelated thiophene 87. The synthesis of isothianinhydrin 88 was then accomplished in six steps from 87. 

Hydration of the middle carbonyl group of ninhydrin removes both pairs of repulsions. 

Kirk, L.K., Lewis, B. A.. Ross. D.A. Morrison, M.A. (1987) Identification of ninhydrin-positive caprolactam metabolites in the rat. Food chem. Toxicol., 25, 233-239... 

The Chemistry of Ninhydrins and Other Cyclic 1,2,3-Tricarbonyl Compounds A. Schoenberg and E. Singer, Tetrahedron, 1978, 34, 1285-1300. 

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