A Shortened Method for the Fluorometric Determination of Phenylalanine

1969 ◽  
Vol 15 (1) ◽  
pp. 15-23 ◽  
Author(s):  
John A Ambrose
Keyword(s):  
Amino Acids ◽  
Incubation Temperature ◽  
Fluorometric Method ◽  
Fluorometric Determination ◽  
Reagent Blank ◽  
Ninhydrin Reaction ◽  
Fluorescence Reaction ◽  
Fluorescence Level ◽  
Ruhemann’S Purple

Abstract As a result of a study of the classic ninhydrin reaction with amino acids (which results in the production of Ruhemann’s purple), and the fluorescence reaction occurring between ninhydrin and phenylalanine in the presence of a dipeptide, the initial incubation period in the fluorescence reaction was shortened from 2 hr. to 16 min. This improvement in the fluorometric method for the determination of phenylalanine was accomplished by (1) decreasing the initial incubation pH from 5.8 to 5.0, and (2) increasing the incubation temperature from 60° to 85°. A study of the effect of pH on the fluorescence level in both the acid and alkaline reactions demonstrated the presence of fluorescence pH plateaus. These plateaus indicate that the fluorescence level was relatively unaffected by a change in pH within specified ranges. A study of the specificity led to the discovery that the inclusion of a peptide control was necessary to correct for one type of nonspecific fluorescence. To make this correction, it was necessary to add the reading of the serum blank to that of the reagent blank, and to subtract this total from the sample reading.

QUANTITATIVE CHROMATOGRAPHIC METHODS: PART 5. AN IMPROVED NINHYDRIN–HYDRINDANTIN REAGENT

1961 ◽  
Vol 39 (2) ◽  
pp. 417-425 ◽  
Author(s):  
A. T. Matheson ◽  
E. Tigane ◽  
C. S. Hanes
Keyword(s):  
Amino Acids ◽  
Quantitative Determination ◽  
Filter Paper ◽  
High Stability ◽  
Reagent Blank ◽  
Chromatographic Methods ◽  
Ruhemann’S Purple

An improved ninhydrin–hydrindantin reagent has been developed for the quantitative determination of amino acids and peptides separated on filter paper chromatograms. This represents a modification of a reagent described earlier, which was based in turn upon the well-known solution of Moore and Stein. The present reagent has been in use for several years and has shown the advantages of high stability, extremely low and steady reagent blank values, and approximately stoichiometric yields of Ruhemann's purple for most amino acids. In addition to its use for determinations on excised areas from filter paper chromatograms, conditions are defined for the use of the reagent for determinations of amino acids in solutions.

Rapid Fluorometric Determination of Benzo(a)pyrene in Foods

1982 ◽  
Vol 45 (2) ◽  
pp. 139-142 ◽  
Author(s):  
YASUHIDE TONOGAI ◽  
SHUNJIRO OGAWA ◽  
MASATAKE TOYODA ◽  
YOSHIO ITO ◽  
MASAHIRO IWAIDA
Keyword(s):  
Detection Limit ◽  
Peak Height ◽  
Excitation Wavelength ◽  
Activated Alumina ◽  
Fluorometric Method ◽  
Fluorometric Determination ◽  
Standard Curve ◽  
Layer Chromatography ◽  
Entire Procedure

A simple and rapid fluorometric method for determining benzo (a) pyrene in foods was developed. Benzo (a) pyrene is extracted from foods with n-hexane:ether mixture (4:1), purified through a column of activated alumina and determined fluorometrically. An excitation wavelength of 295 nm and emission wavelength of 403 nm were used for calculating concentrations of benzo (a) pyrene. The peak height at 403 nm and baseline between 392 and 418 nm were employed to derive a standard curve for quantitating benzo (a) pyrene. A calibration curve for between 0.04 – 4 ng/ml of benzo (a) pyrene was used. Recoveries of benzo (a) pyrene from 14 kinds of food spiked at levels of 20 and 2ppb were within the range of 79.5 – 93.8% and 50.0 – 80.6%, respectively. The entire procedure takes only one hour with the detection limit being 0.1 ppb. Benzo (a) pyrene detected was reconfirmed by thin-layer chromatography.

ANTIMONY TRICHLORIDE – ETHANOL PRECIPITATION FOR THE FLUOROMETRIC DETERMINATION OF RIBOFLAVIN IN PORK

1947 ◽  
Vol 25f (2) ◽  
pp. 133-140 ◽  
Author(s):  
Jessie R. Lewis ◽  
Paul R. Gorham
Keyword(s):  
Antimony Trichloride ◽  
Fluorometric Method ◽  
Fluorometric Determination ◽  
Ethanol Precipitation

A fluorometric method suitable for routine analyses is presented in which interfering substances in papain–takadiastase extracts of pork are precipitated in the presence of 0.02% antimony trichloride and 47.5% ethanol. Antimony trichloride prevents the adsorption of riboflavin upon the precipitate. Recoveries of 95 to 100% are obtained. Determinations by this method correlate well with those obtained microbiologically: for eight samples of fresh pork, four cooked, and four uncooked, r =.94; for 20 samples of cured pork, four cooked, and 16 uncooked, r =.98.

Fluorometric Determination of Selenium in Foods

1974 ◽  
Vol 57 (2) ◽  
pp. 368-372 ◽  
Author(s):  
Milan Ihnat
Keyword(s):  
Standard Deviation ◽  
Milk Powder ◽  
Skim Milk ◽  
Skim Milk Powder ◽  
Food Samples ◽  
Fluorometric Method ◽  
Fluorometric Determination ◽  
Relative Standard ◽  
The Mean

Abstract A fluorometric method using 2,3-diaminonaphthalene for estimating selenium has been evaluated with regard to its applicability to food samples. Charring of the sample during digestion appeared to result in losses of native and added selenium from some samples, so a modified wet digestion procedure was introduced. Digestion first in nitric acid followed by a mixture of nitric-perchloric-sulfuric acids substantially reduced the incidence of sample charring for a variety of foods. The mean apparent recovery of selenium added as selenite or selenate at 100 and 500 ng levels to 0.1 and 1.0 g corn cereal, skim milk powder, and meat and 0.1 g fish was 101.0%; the actual recovery of the same levels of selenium from standard solutions was 96.6%. For a variety of samples containing 5—750 ng native or added selenium, the standard deviation as 4.7 + 1.95 X 10-2W ng, where W = ng selenium in the sample taken for analysis. The relative standard deviation (RSD) as a function of selenium weight (ng) was 50% (10), 6.7% (100), 4.3% (200), 3.1% (400), 2.7% (600), and 2.5% (800). The detection limit (weight of selenium at which RSD = 50%) was 10 ng at a mean blank level of 25 ng.

Fluorometric Determination of Histamine in Tuna: Collaborative Study

1977 ◽  
Vol 60 (5) ◽  
pp. 1131-1136 ◽  
Author(s):  
Walter F Staruszkiewicz
Keyword(s):  
Collaborative Study ◽  
Colorimetric Method ◽  
Fluorometric Method ◽  
Fluorometric Determination ◽  
Canned Tuna

Abstract Six samples of canned tuna, albacore, yellow-fin, and skipjack, in water or oil pack were analyzed in duplicate by a fluorometric method and the AOAC colorimetric method. For the fluorometric method, recoveries of histamine added to acceptable tuna averaged 99% with a range of 91 to 107%. Agreement between laboratories for the analyses of decomposed tuna containing 20–200 mg histamine/100 g sample was excellent. Results from the fluorometric method are comparable with those from the AOAC colorimetric method ; the fluorometric method has been adopted as official first action.

A Fluorometric Method for Measuring Leucine Aminopeptidase Activity in Red Blood Cells, Serum, or Tissues

1970 ◽  
Vol 16 (5) ◽  
pp. 412-415 ◽  
Author(s):  
Tetsuo Uete ◽  
Hiroko Tsuchikura ◽  
Kiichi Ninomiya
Keyword(s):  
Blood Cells ◽  
Leucine Aminopeptidase ◽  
Test Sample ◽  
Tissue Homogenate ◽  
Aminopeptidase Activity ◽  
Supernatant Fluid ◽  
Fluorometric Method ◽  
Fluorometric Determination ◽  
Amine Solutions

Abstract A fluorometric determination of leucine aminopeptidase activity in a biological system is described, which is simpler and more sensitive than colori-metric methods. Serum or tissue homogenate is incubated with L-β-naphthylamide at pH 7.2 and 37°C for 10 min. After incubation, ethanol is added to stop the reaction and protein is precipitated. The fluorescence of j3-naphthylamine in the supernatant fluid is measured. Since β-naphthylamide reduces the intensity of the fluorescence of s-naphthyl-amine, solutions used in preparing the standard s-naphthylamine curve must have the same concentration of L-leucyl-s-naphthylamide present as in the test sample.

Fluorometric Determination of Methyl Anthranilate in Concord Grape Juice

1976 ◽  
Vol 59 (2) ◽  
pp. 269-272
Author(s):  
Donald J Casimir ◽  
James C Moyer ◽  
Leonard R Mattick
Keyword(s):  
Correlation Coefficient ◽  
Grape Juice ◽  
Methyl Anthranilate ◽  
Fluorometric Method ◽  
Fluorometric Determination ◽  
Juice Concentrate ◽  
Concord Grape ◽  
Colorimetric Procedure

Abstract A method is described for the determination of methyl anthranilate in Concord grape products. A sample of juice, concentrate, pulp, or essence is steam distilled in a micro-Kjeldahl unit and the fluorescence of the distillate collected in pH 7 buffer is measured directly with a fluorometer. The method is rapid and sensitive to 0.1 ppm methyl anthranilate. A correlation coefficient of 0.988 was found between the AOAC colorimetric procedure and the fluorometric method.

Automated Fluorometric Method for the Determination of Morphine in Urine

1972 ◽  
Vol 55 (4) ◽  
pp. 880-887
Author(s):  
M Sansur ◽  
A Buccafuri ◽  
S Morgenstern
Keyword(s):  
Methadone Maintenance ◽  
Fluorometric Method ◽  
Fluorometric Determination ◽  
Automated Method ◽  
Maintenance Program ◽  
Extraction Step ◽  
Sample Segment ◽  
Methadone Maintenance Program ◽  
Layer Chromatography

A sensitive and specific automated method for the fluorometric determination of morphine in urine was developed. The analysis is performed at a rate of 40 samples/hr. The method is based on the oxidation of morphine to the fluorescent pseudo-morphine dimer. Morphine is extracted from urine at pH 9.4 with a mixture of organic solvents. The organic phase is washed with a dilute buffer at pH 9.4 and is further extracted with a dilute alkaline solution. Following the third extraction step, 2 equal portions of the alkali phase are buffered to pH 9.4. Potassium ferricyanide solution is added to the sample segment and water is added to the “blank” segment. Each of these solutions enters a separate fluorometer and the fluorescence is recorded. An increment in fluorescence of the sample as compared to the blank indicates the presence of morphine. Concentrations as low as 0.2 μg free morphine/ml urine are easily detected. Five hundred subjects from a Methadone Maintenance Program have been tested. Results show excellent agreement with determinations on the same samples by thin layer chromatography.

Influence of Cations on the Ninhydrin Reaction for the Determination of Amino-Acids

Nature ◽  
1953 ◽  
Vol 172 (4377) ◽  
pp. 543-543 ◽  
Author(s):  
HANAN MEYER ◽  
EMANUEL RIKLIS
Keyword(s):  
Amino Acids ◽  
Ninhydrin Reaction

THE QUANTITATIVE ESTIMATION OF FROST INJURY AND RESISTANCE IN BLACK LOCUST, ALFALFA, AND WHEAT TISSUES BY DETERMINATION OF AMINO ACIDS AND OTHER NINHYDRIN-REACTING SUBSTANCES RELEASED AFTER THAWING

1964 ◽  
Vol 42 (6) ◽  
pp. 637-649 ◽  
Author(s):  
D. Siminovitch ◽  
H. Therrien ◽  
F. Gfeller ◽  
B. Rheaume
Keyword(s):  
Amino Acids ◽  
Black Locust ◽  
Quantitative Estimation ◽  
Freezing Temperature ◽  
Freezing Injury ◽  
Tree Bark ◽  
Freezing Process ◽  
Frost Injury ◽  
Ninhydrin Reaction

Amino acids and other soluble α-amino compounds are liberated into a leaching medium from tissues of black locust bark, alfalfa, and wheat that are frozen to temperatures which are injurious to the tissues. The amounts liberated increase with lowering in freezing temperature and are proportional to the loss in vital capacity of the tissue. Insignificant amounts of amino acids are released by leaching of non-frozen tissue while a maximum is reached at freezing temperatures which are completely lethal. The amino acids liberated from frozen and thawed tissues must originate from the destruction of living cells by the freezing process. The determination of the concentration of amino acids in the medium in which the plant tissues are leached after freezing can be used therefore as a quantitative method for the estimation of the injury sustained in the freezing.The use of the ninhydrin reaction for the purpose of this determination is described and its application to the estimation of freezing injury and resistance in a variety of hardy and non-hardy tissues of alfalfa, wheat, and black locust tree bark is shown. The extension of this procedure to the determination of injury produced by toxic and other detrimental agents is indicated.

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