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.

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.

Fluorometric Determination of Plasma 11-Hydroxycorticosteroids. II. Studies on the Specificity of the Method

1973 ◽  
Vol 19 (7) ◽  
pp. 718-724 ◽  
Author(s):  
Luis E Mejer ◽  
Roberta C Blanchard
Keyword(s):  
Fatty Acids ◽  
Thin Layer ◽  
Total Cholesterol ◽  
Thin Layer Chromatography ◽  
Plasma Cortisol ◽  
Fluorometric Method ◽  
Fluorometric Determination ◽  
Main Component ◽  
Layer Chromatography

Abstract We have investigated the specificity of the fluorometric method we proposed [Clin. Chem. 19, 710 (1973)] for plasma or serum 11-hydroxycorticosteroid determinations. The principal specific fluorogenic contaminants in the cortisol-containing extract of plasma, as detected by thin-layer chromatography and chemically, were triglycerides and total cholesterol. These contaminants contributed an average of 1.6 µg/dl to the total normal cortisol value. Fatty acids were also found, but did not fluoresce. Nonspecific serum fluorogens were quantitated at 1.3 ± 1.2 µg/dl. Cortisol, corticosterone, and fluorogenic contaminants represented an average of 62.0, 29.1, and 9.9%, respectively, of the total fluorometric plasma cortisol value obtained (expressed in terms of cortisol standard). A ratio of 8.3 ± 2.4 was found for cortisol/corticosterone when each component was determined in terms of its respective standard. Fluorescence scans of the plasma cortisol extract indicated cortisol to be the main component present, accompanied by minor fluorescent contaminants.

Fluorometric Measurement of Fecal Bile Acids

1968 ◽  
Vol 14 (4) ◽  
pp. 348-359 ◽  
Author(s):  
Donald T Forman ◽  
Charles Phillips ◽  
Walter Eiseman ◽  
C Bruce Taylor
Keyword(s):  
Bile Acids ◽  
Human Subjects ◽  
Mixed Diet ◽  
Fluorometric Method ◽  
Fluorometric Determination ◽  
Fecal Bile Acids ◽  
Normal Human ◽  
Layer Chromatography ◽  
Total Bile Acids

Abstract A method is described for the fluorometric determination of fecal bile acids. The method combines solvent extraction and thin-layer chromatography (TLC) isolation technics with a fluorometric method for measuring total bile acids. Recoveries of individual bile acids added to feces averaged 107% with a standard deviation of ± 5.6%. Bile acid excretion in normal human subjects on a self-selected mixed diet ranged from 196 to 460 mg. total bile acids per 24 hr.

Fluorometric determination of magnesium in serum with 2-hydroxy-1-naphthaldehyde salicyloylhydrazone.

1989 ◽  
Vol 35 (7) ◽  
pp. 1492-1496 ◽  
Author(s):  
P C Ioannou ◽  
D G Konstantianos
Keyword(s):  
Regression Analysis ◽  
Intensive Care ◽  
Linear Regression Analysis ◽  
Colorimetric Method ◽  
Fluorometric Method ◽  
Fluorometric Determination ◽  
Serum Samples ◽  
Standard Curve ◽  
Relative Standard

Abstract This simple, rapid, sensitive fluorometric method for determining magnesium is based on formation of a fluorescent complex of magnesium with 2-hydroxy-1-naphthaldehyde salicyloyl-hydrazone in alkaline ethanolic medium (lambda ex = 420 nm, lambda em = 460 nm). The detection limit of the method is 0.05 microgram/L (2 nmol/L) and the relative standard deviations (CVs) are 0.8%, 1.1%, and 2.5% at magnesium concentrations of 50, 5.0, and 0.50 microgram/L, respectively. The standard curve is linear from 0 to 250 micrograms/L (0-10 mumol/L). We investigated the chemistry of the reaction, and have applied the method to determine magnesium in 100-fold-diluted, otherwise untreated serum samples. Within-run CVs for the method were 1.7%, 1.1%, and 1.3% at mean magnesium concentrations of 15.7, 26.4, and 36.2 mg/L, respectively. Day-to-day CVs were 2.7%, and 3.6% at mean magnesium concentrations of 10.1 and 25.5 mg/L, respectively. Samples from 96 hospitalized patients in intensive-care units were analyzed by the proposed method (y) and by an automated colorimetric method involving Magon sulfonate reagent (x). Linear regression analysis of the results yielded: y = 1.01x - 0.04 (r = 0.982, Sxy = 0.90).

Fluorometric Method for Determination of 1,2-Unsaturated Aldehydes in Autooxidized Lipids with 2,4-Diaminotoluene

1990 ◽  
Vol 73 (4) ◽  
pp. 590-594
Author(s):  
Teruhisa Hirayama ◽  
Shinji Miura ◽  
Mariko Araki ◽  
Yoshiko Takeo ◽  
Tetsushi Watanabe
Keyword(s):  
Methyl Oleate ◽  
Acidic Condition ◽  
Emission Wavelength ◽  
Excitation Wavelength ◽  
Fluorometric Method ◽  
Unsaturated Aldehydes ◽  
Liquid Chromatographic

Abstract A simple fluorometric method has been developed to determine 1,2-unsaturated aldehydes in autooxidized lipids. 1,2- Unsaturated aldehydes were allowed to react with 2,4-diamlnotoluene in acidic condition and the products, 7-amlno-6- methylqulnoline derivatives, were determined by a fluorometric procedure at 394 nm (excitation wavelength) and 494 nm (emission wavelength). Finally, 1902.9, 1738.8, and 2149.2 μg/g of 1,2-unsaturated aldehydes as 2-propenal were detected in 20-h autooxidized methyl oleate, methyl llnoleate, and methyl llnolenate, which contained 98.5, 223.2, and 355.6 μg/g, respectively, of thlobarblturlc acid reactive substances as malondialdehyde. In a preliminary liquid chromatographic LC determination of 2-propenal In autooxidized lipids, 29, 20, and 57 μg/g, respectively, of 2- propenal were detected In 20-h autooxidized methyl oleate, methyl llnoleate and methyl llnolenate. The 2-propenal can be detected as 7-amlno-6-methylqulnoline by using LC-fluorometrlc procedure at levels of 100 pg.

Fluorometric estimation of triglycerides in serum by a modification of the method of Bucolo and David.

1977 ◽  
Vol 23 (2) ◽  
pp. 286-288 ◽  
Author(s):  
E B Rietz ◽  
G G Guilbault
Keyword(s):  
Blood Serum ◽  
Spectrophotometric Method ◽  
Serum Triglyceride ◽  
Excitation Wavelength ◽  
Free Glycerol ◽  
Fluorometric Method ◽  
Nadh Fluorescence ◽  
Instrument Response ◽  
Serum Triglyceride Concentration

Abstract An enzymic, flurometric method is described for determination of triglycerides (and glycerol) in blood serum, a modification of the method of Bucolo and David [Clin. Chem. 19, 476 (1973)]. Commercially available reagent kits are used. The rate of disappearance of NADH fluorescence at 460 nm (excitation wavelength, 365 nm) is monitored and related to serum triglyceride concentration, corrected for the content of free glycerol. We compared the results obtained fluorometrically to the ultraviolet spectrophotometric Boehringer Neutral Fat method used at Gentofte Hospital, Copenhagen. Instrument response and concentration were linearly related in the range 0.27 to 2.7 mmol of triglycerides per liter of serum with the fluorometric method. The CV was 0.9% for the fluorometric method, 3.7% for the spectrophotometric procedure. The fluorometric method requires less reagents, time, and calculations than does the spectrophotometric method.

Comparison of Postcolumn Derivatization-Liquid Chromatography with Thin-Layer Chromatography for Determination of Aflatoxins in Naturally Contaminated Corn

1990 ◽  
Vol 73 (4) ◽  
pp. 579-581 ◽  
Author(s):  
Rodney W Beaver ◽  
David M Wilson ◽  
Mary W Trucksess
Keyword(s):  
Liquid Chromatography ◽  
Detection Limit ◽  
Thin Layer ◽  
Thin Layer Chromatography ◽  
Correlation Coefficient ◽  
Low Levels ◽  
Aflatoxin B2 ◽  
Layer Chromatography ◽  
Postcolumn Derivatization

Abstract Quantitation of aflatoxins by liquid chromatography with postcolumn iodine derlvatization (LC-PCD) and fluorescence detection was compared with quantitation by the AOAC CB method, 968.22. Thirty-seven naturally contaminated corn samples were ground and then divided. One portion was extracted, and the extract was cleaned up and analyzed by thin-layer chromatography according to the CB method. The second portion was extracted and cleaned up In a similar fashion, but quantitation was by the LC-PCD method. For aflatoxin B1, concentrations ranging from 0 to 150 ng/g, results obtained by the 2 methods were fitted to a linear equation with the LC-PCD results as the dependent variable. The correlation coefficient was 0.99, the Intercept was near 0, and the slope was near 1. For aflatoxin B2, the correlation coefficient was 0.97, and the Intercept was near 0. However, the slope of the equation relating LC-PCD concentration to TLC concentration was only 0.5. We believe that this lack of equivalence between the methods for determination of aflatoxin B2 is due to overestlmatlon by the TLC method because the low levels present are near the TLC detection limit for B2.

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 Plasma 11-Hydroxycorticosteroids. I. Rapid Procedure for Clinical Screening

1973 ◽  
Vol 19 (7) ◽  
pp. 710-717 ◽  
Author(s):  
Luis E Mejer ◽  
Roberta C Blanchard
Keyword(s):  
Small Groups ◽  
Excitation Wavelength ◽  
Plasma Samples ◽  
Fluorometric Determination ◽  
Clinical Screening ◽  
Rapid Procedure ◽  
Specificity And Sensitivity ◽  
Accuracy And Precision ◽  
Sensitivity Specificity

Abstract A method proposed by Kitabchi and Kitchell [Anal. Biochem. 34, 529 (1970)] for the fluorometric determination of plasma 11-hydroxycorticosteroids has been modified. It is simplified by eliminating centrifugations, by processing all samples consecutively (rather than in small groups), by using disposable test tubes, and by prealkalinizing standards and blanks as well as plasma samples. Specificity and sensitivity are increased by measuring fluorescence at 520 nm, with an excitation wavelength of 470 nm. Effects of prealkalinization and time of fluorescence development on final cortisol values were studied. Large fluorescence increases are possible after 60 min of fluorescence development. Cortisol recoveries were not changed by the use of phase-separating filter paper nor were cortisol values altered by partial aging of the fluorescence reagent. Sensitivity, specificity, accuracy, and precision of the proposed method are reported.

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.

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