Colorimetric Determination of Total Iodine in Foods by Iodide-Catalyzed Reduction of Ce+4

1986 ◽  
Vol 69 (4) ◽  
pp. 687-689 ◽  
Author(s):  
Peter W F Fischer ◽  
Mary R L’Abbé ◽  
Alexandre Giroux
Keyword(s):  
Detection Limit ◽  
Reference Material ◽  
Standard Reference Material ◽  
Dairy Products ◽  
Colorimetric Method ◽  
Colorimetric Determination ◽  
Acid Digestion ◽  
Total Iodine ◽  
Relative Standard

Abstract An earlier acid digestion determination of iodine in foods was modified to provide an improved detection limit and to allow for the analysis of a greater variety and larger amounts of foods. The organic material in the sample was oxidized overnight by concentrated nitric acid, followed by digestion in a mixture of concentrated sulfuric and 70% perchloric acid. The iodine was determined by an automated colorimetric method based on the iodide-catalyzed reduction of Ce+4 by As+3. The method had an average relative standard deviation of 3.1% for the samples analyzed, and a detection limit of 0.1 ng/mL in the digested solution and 5 ng/g in a 2 g sample prior to digestion. The recovery of added iodine ranged from 90.3 to 101.3%, using external standards. Samples analyzed included NBS Standard Reference Material 1549, and composites of a variety of dairy products, meat, eggs and fish, cereals, and potatoes. The iodine detected in these samples ranged from 9 ng/g for the potato group to 3360 ng/g for the standard reference material.

Colorimetric Determination of Potassium in Plasma and Serum by Reflectance Photometry with a Dry-Chemistry Reagent

1992 ◽  
Vol 38 (7) ◽  
pp. 1371-1372 ◽  
Author(s):  
R H Ng ◽  
K M Sparks ◽  
B E Statland
Keyword(s):  
Reference Material ◽  
Standard Reference Material ◽  
Colorimetric Assay ◽  
Ion Selective Electrode ◽  
Colorimetric Determination ◽  
Selective Electrode ◽  
Flame Photometer ◽  
Near Patient Testing

Abstract We evaluated a colorimetric assay of potassium in plasma and serum with the Boehringer Mannheim Reflotron reflectance photometric analyzer, which is designed for near-patient testing in hospitals and physicians' offices. This potassium method does not require calibration or instrument maintenance by the operator. Analysis of 30 microL of plasma or serum takes approximately 140 s. Within-day imprecision (CV) was 1.0-1.2%. Total CVs over a 1-month period were 1.0-1.4%. Patients' results from the Reflotron correlated well with those from the IL 643 flame photometer and the Beckman Synchron CX3 ion-selective electrode methods. The accuracy of Reflotron values was also verified with Standard Reference Material 956 from the National Institute of Standards and Technology.

Simple Colorimetric Determination of Carrageenan in Jellies and Salad Dressings

1991 ◽  
Vol 74 (6) ◽  
pp. 1019-1022 ◽  
Author(s):  
Yoshie Yabe ◽  
Takahiro Ninomiya ◽  
Takashi Tatsuno ◽  
Taro Okada
Keyword(s):  
Gas Chromatography ◽  
Detection Limit ◽  
Alcian Blue ◽  
Coefficient Of Variation ◽  
Capillary Gas Chromatography ◽  
Colorimetric Method ◽  
Sample Solution ◽  
Colorimetric Determination ◽  
Chromatography Method

Abstract A simple, rapid colorimetric method is described for the determination of carrageenan (CAR) in foods such as jellies and salad dressings. Alcian blue reagent is added to the sample solution prepared from these foods, then CAR is precipitated selectively as a CAR-alcian blue complex. The precipitate is dissolved in monoethanolamine and determined colorimetrically at 615 nm. Overall recovery for jelly was 93.3% with a coefficient of variation (CV) of 5.8%. Overall recovery for salad dressing was 91.9% with a CV of 3.0%. The detection limit was 0.05%. The results obtained by the proposed method were similar to those obtained by a capillary gas chromatography method.

Acid Digestion Determination of Iodine in Foods

1981 ◽  
Vol 64 (1) ◽  
pp. 71-74
Author(s):  
Peter W F Fischer ◽  
Mary R L’abbé
Keyword(s):  
Standard Deviation ◽  
Relative Standard Deviation ◽  
Colorimetric Method ◽  
Acid Digestion ◽  
Milk Samples ◽  
Relative Standard ◽  
Dry Ashing

Abstract A method for determining iodine in food is described. The samples were digested using a mixture of sulfuric, nitric, and perchloric acids. The iodine was determined by an automated colorimetric method based on the iodide-catalyzed reduction of Ce+4 by As+3. For milk samples, the relative standard deviation for the method was less than 3%, and the recovery of 125I added to milk and carried through the method ranged from 96 to 102%. The method was compared with 4 other procedures and was superior to alkaline dry ashing methods.

Colorimetric Determination of Carbaryl in Wettable Formulations

1971 ◽  
Vol 54 (1) ◽  
pp. 128-130
Author(s):  
Eugenio E Vonesch ◽  
Maria H C K de Riveros
Keyword(s):  
Detection Limit ◽  
Colorimetric Method ◽  
Colorimetric Determination ◽  
Technical Products

Abstract A rapid colorimetric method is described for the determination of carbaryl in technical products and wettable formulations, based on the reaction of carbaryl with diazotized 2,5-dichloroaniline. This reaction is sensitive to 0.1 μg, with a detection limit of 0.2 ppm. Recoveries of pure carbaryl were excellent and analyses of technical products were reproducible.

Rapid Colorimetric Determination of Activity of Subtilisin Enzymes in Cleaning Products

1989 ◽  
Vol 72 (6) ◽  
pp. 881-882
Author(s):  
Allan E Klein ◽  
John Freiberg ◽  
Steven Same ◽  
Maryanne Carroll
Keyword(s):  
Colorimetric Method ◽  
Hydrolytic Activity ◽  
Colorimetric Determination ◽  
Cleaning Product ◽  
Cleaning Products ◽  
Spontaneous Hydrolysis ◽  
Relative Standard ◽  
Determination Of Activity ◽  
Hydrolysis Of

Abstract A new colorimetric method is described for the determination of enzymatic activity of subtilisin in cleaning products. The procedure is more rapid and precise than the casein digestion methods commonly used to assay protease activity. The principle of the colorimetric method depends on the determination rate of p-nitrophenol released on hydrolysis of N-CBZ-L-leucine-/Miitrophenyl ester at pH 8.0 by subtilisin, with correction for any nonenzymatic (spontaneous) hydrolysis of the substrate. Because of the broad range of hydrolytic activity of this enzyme, and the difficulties in predicting its proteolytic activity, this hydrolytic rate was chosen as a general indicator of subtilisin enzyme behavior. The slope for 7 replicate standard curves generated over a 6 week period exhibited a relative standard deviation of 7.5%, and 8.0% for 20 replicates with an enzyme cleaning product. Papain does not interfere with this assay.

Β-Cyclodextrin-Cross-Linked Polymer Microcolumn Dynamic Preconcentration/analysis for Trace Cadium

2011 ◽  
Vol 284-286 ◽  
pp. 82-86
Author(s):  
Xia Shi Zhu ◽  
Ying Gu ◽  
Ting Ting Hou
Keyword(s):  
Standard Deviation ◽  
Detection Limit ◽  
Reference Material ◽  
Water Samples ◽  
Enhancement Factor ◽  
Optimum Conditions ◽  
Column Method ◽  
Relative Standard ◽  
Trace Cadmium

The adsorptive capability of β-Cyclodextrin-cross-linked polymer(β-CDCP) for cadmium was assessed in this work using column method. It was found that the complex (Cd(II)-5-Br-PADAP) could be quantitatively retained on the β-CDCP in the pH 8.5, eluted completely with 1.5 mol×L-1HCl. Under the optimum conditions, the linear range, detection limit (DL) and the relative standard deviation (R.S.D.) was 2.0-60.0 μg×L-1, 7.8 ng×L-1and 2.20% (n=3, c=20.0 μg×L-1) respectively. The separation of Cd(II) was achieved from water samples with an enhancement factor of 20. Moreover, the β-CDCP could be used repeatedly and offered better recovery. The method was validated using a certified reference material, and applied for the determination of trace cadmium in water samples.

Colorimetric Determination of Fluoride in Drinking Groundwater using a Polymeric Zirconium Complex of 5-(2-Carboxyphenylazo)-8-Hydroxyquinoline

2013 ◽  
Vol 12 (7) ◽  
pp. 460-465
Author(s):  
Sameer Amereih ◽  
Zaher Barghouthi ◽  
Lamees Majjiad
Keyword(s):  
Drinking Water ◽  
Detection Limit ◽  
Complex Formation ◽  
Molar Absorptivity ◽  
Colorimetric Determination ◽  
Zirconium Complex ◽  
Reliable Determination ◽  
Percentage Recovery ◽  
Quantitation Limit

A sensitive colorimetric determination of fluoride in drinking water has been developed using a polymeric zirconium complex of 5-(2-Carboxyphenylazo)-8-Hydroxyquinoline as fluoride reagents. The method allowed a reliable determination of fluoride in range of (0.0-1.5) mg L-1. The molar absorptivity of the complex formation is 7695 ± 27 L mol-1 cm-1 at 460 nm. The sensitivity, detection limit, quantitation limit, and percentage recovery for 1.0 mg L-1 fluoride for the proposed method were found to be 0.353 ± 0.013 μg mL-1, 0.1 mg L-1, 0.3 mg L-1, and 101.7 ± 4.1, respectively.

The fluorimetric determination of cerium and terbium

1989 ◽  
Vol 54 (3) ◽  
pp. 616-621 ◽  
Author(s):  
Záviš Holzbecher
Keyword(s):  
Rare Earth ◽  
Detection Limit ◽  
Rare Earth Elements ◽  
Fluorimetric Determination ◽  
Fluorescence Maximum ◽  
Relative Standard ◽  
And Shifts ◽  
Hcl Medium ◽  
Fold Excess

It has been found that phosphoric acid decreases the first excitation maximum of Ce(III) at 256 nm, increases the second excitation maximum at 297 nm and shifts the fluorescence maximum from 350 to 346 nm. Under optimum conditions, with λexc = 297 nm and λem = 346 nm, Ce(III) can be determined fluorimetrically with a detection limit of 1.2 ng ml-1 in 12M-H3PO4 medium. No interference was observed from a 20-200 fold excess of HCl, H2SO4, Na, K, NH4+, Al and the rare earth elements. HNO3 interferes and Ce(IV) and Fe(III) interfere strongly. It follows from the stereofluorograms of Ce and Tb that the spectra of the two elements are practically independent. The detection limit for Tb(III) in 0.02-2.5M-H2SO4 medium for λexc = 222 nm and λem = 494 nm is 33 ng ml-1. No interference was observed from a 5-20 fold excess of Al3+ and the other rare earth elements. The determination is slightly less sensitive in H3PO4 or HCl medium. The relative standard deviation of the measurement for 10 ng ml-1 Ce(III) or 50 ng ml-1 Tb(III) is about 3%.

Colorimetric Determination of Hydroxyproline as Measure of Collagen Content in Meat and Meat Products: NMKL Collaborative Study

1990 ◽  
Vol 73 (1) ◽  
pp. 54-57 ◽  
Author(s):  
Kurt Kolar
Keyword(s):  
Collaborative Study ◽  
Colorimetric Method ◽  
Meat Products ◽  
Acid Oxidation ◽  
Colorimetric Determination ◽  
Mean Values ◽  
Collaborative Studies ◽  
Freeze Dried ◽  
Analytical Result

Abstract A colorimetric method for the determination of hydroxyproline as a measure of collagen in meat and meat products has been collaboratively studied in 18 laboratories. The method includes hydrolysis with sulfuric acid, oxidation with chloramine- T, and formation of a reddish purple complex with 4- dimethylaminobenzaldehyde. Five frozen and 3 freeze-dried samples were tested, ranging in content from 0.11 to 0.88% and from 0.39 to 4.0% hydroxyproline, respectively. The mean values of 2 identical samples were 0.245 and 0.251 %. The average recovery from a spiked sample was 96.1 %. The hydroxyproline content of a known sample (a mixture of 2 samples in the ratio 5:2) was calculated to 1.42%, which agrees well with the analytical result, 1.40%. In comparison with other collaborative studies, based on the ISO analytical method, the repeatability and reproducibility of this method agree well with the other results. This method was accepted as an official NMKL method by all national Committees, and has been adopted official first action by AOAC as an NMKLAOAC method.

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