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.

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 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.

200. The colorimetric determination of pH in milk and whey by means of the “Wulff” pH tester

1938 ◽  
Vol 9 (3) ◽  
pp. 336-338 ◽  
Author(s):  
E. Aschaffenburg
Keyword(s):  
Colorimetric Method ◽  
Cheddar Cheese ◽  
Titratable Acidity ◽  
Colorimetric Determination ◽  
Expensive Equipment ◽  
Hydrogenion Concentration ◽  
The Relationship

It has been repeatedly pointed out(1, 2, 3) that the properties of cheese during the different stages of its manufacture should be correlated with the hydrogenion concentration rather than with the titratable acidity. Little systematic work has, however, so far been carried out in this direction, except for a study of the relationship between pH and titratable acidity in Cheddar cheese by Brown & Price(4). In planning work on similar lines, it was realized that the potentiometric methods of determining pH require expensive equipment and skilled attention, so that a supplementary colorimetric method, if sufficiently accurate to indicate the major changes in pH, should appeal more strongly to the practical cheesemaker on account of its cheapness and simplicity and the ease with which the outfit can be transported.

Enzymic colorimetric determination of phosphatidylglycerol in amniotic fluid.

1984 ◽  
Vol 30 (4) ◽  
pp. 534-537 ◽  
Author(s):  
J D Artiss ◽  
M W McGowan ◽  
D R Strandbergh ◽  
E Epstein ◽  
B Zak
Keyword(s):  
Amniotic Fluid ◽  
Fetal Lung ◽  
Aqueous Sample ◽  
Colorimetric Determination ◽  
Glycerol Phosphate ◽  
Ionic Detergent ◽  
Catalyzed Reactions ◽  
Enzyme Catalyzed Reactions ◽  
Hydrolysis Of

Abstract We describe a procedure for the enzymic, colorimetric determination of phosphatidylglycerol in amniotic fluid. After extraction into chloroform:methanol (2:1 by vol) and evaporation, the phospholipid-containing residue is redissolved in a non-ionic detergent, which thus provides an aqueous sample. The subsequent enzymic reaction sequence involves phospholipase-catalyzed hydrolysis of glycerol from its phospholipid. Subsequent enzyme-catalyzed reactions phosphorylate this glycerol and oxidize the resulting glycerol phosphate to produce hydrogen peroxide, which is reacted to produce an intense red chromogen in the peroxidase-catalyzed coupling of 4-aminoantipyrine and 2-hydroxy-3,5-dichlorobenzenesulfonate. When used in conjunction with previously reported enzymic techniques for determination of lecithin and sphingomyelin, this procedure may provide an accurate and precise "lung profile" for assessment of fetal lung maturity.

Colorimetric Determination of Terbutaline Sulfate and Orciprenaline Sulfate via Nitrosation and Difference Spectrophotometry

1987 ◽  
Vol 70 (3) ◽  
pp. 568-571 ◽  
Author(s):  
Mohamed E El-Sadek ◽  
Hisham E Abdel Latef ◽  
Afaf A Aboul Khier
Keyword(s):  
Hydrochloric Acid ◽  
Sodium Nitrite ◽  
Colorimetric Method ◽  
Dosage Forms ◽  
Alkaline Media ◽  
Colorimetric Determination ◽  
Pharmaceutical Dosage Forms ◽  
Terbutaline Sulfate ◽  
The Difference

Abstract A colorimetric method is proposed for determination of terbutaline sulfate, orciprenaline sulfate, and their dosage forms. The suggested method depends on nitrosation of the 2 drugs by using sodium nitrite and hydrochloric acid. Addition of sodium hydroxide increases the intensity of the color developed. The difference between absorption values measured in acid and alkaline media is taken as a measure of concentration. Variables were carefully studied and optimized. Results for both compounds adhered to Beer's law over the range 2- 28 μg/mL. The method has proved to be accurate and precise for analysis of pharmaceutical dosage forms.

Sulfuric Acid/Hydrogen Peroxide Digestion and Colorimetric Determination of Phosphorus in Meat and Meat Products: Collaborative Study

1991 ◽  
Vol 74 (1) ◽  
pp. 22-26 ◽  
Author(s):  
David K Christians ◽  
Thomas G Aspelund ◽  
Scott V Brayton ◽  
Larry L Roberts
Keyword(s):  
Hydrogen Peroxide ◽  
Sulfuric Acid ◽  
Collaborative Study ◽  
Meat Products ◽  
Colorimetric Determination ◽  
Pork Sausage ◽  
Relative Standard ◽  
Significant Difference ◽  
Standard Deviations

Abstract Seven laboratories participated In a collaborative study of a method for determination of phosphorus in meat and meat products. Samples are digested In sulfuric acid and hydrogen peroxide; digestion Is complete In approximately 10 mln. Phosphorus Is determined by colorimetric analysis of a dilute aliquot of the sample digest. The collaborators analyzed 3 sets of blind duplicate samples from each of 6 classes of meat (U.S. Department of Agriculture classifications): smoked ham, water-added ham, canned ham, pork sausage, cooked sausage, and hamburger. The calibration curve was linear over the range of standard solutions prepared (phosphorus levels from 0.05 to 1.00%); levels in the collaborative study samples ranged from 0.10 to 0.30%. Standard deviations for repeatability (sr) and reproducibility (sR) ranged from 0.004 to 0.012 and 0.007 to 0.014, respectively. Corresponding relative standard deviations (RSDr and RSDR, respectively) ranged from 1.70 to 7.28% and 3.50 to 9.87%. Six laboratories analyzed samples by both the proposed method and AOAC method 24.016 (14th Ed.). One laboratory reported results by the proposed method only. Statistical evaluations Indicated no significant difference between the 2 methods. The method has been adopted official first action by AOAC.

Determination of Sevin Insecticide Residues in Fruits and Vegetables

1964 ◽  
Vol 47 (2) ◽  
pp. 283-286
Author(s):  
D P Johnson
Keyword(s):  
Fruits And Vegetables ◽  
Collaborative Study ◽  
Colorimetric Determination ◽  
Average Recovery ◽  
Insecticide Residues ◽  
Chromogenic Agent ◽  
Hydrolysis Of ◽  
Concentration Levels ◽  
Good Agreement

Abstract Collaborative study of a method for Sevin insecticide residues was repeated with apples and lettuce as test crops. The method is based on alkaline hydrolysis of Sevin and colorimetric determination of the resulting 1-naphthol with p-nitrobenzenediazonium fluoborate as chromogenic agent. Data from 5 collaborators were in good agreement with an average recovery of 87.8% at 2 concentration levels. It is recommended that the method be adopted as official, first action.

Colorimetric determination of potassium in whole blood, serum, and plasma.

1985 ◽  
Vol 31 (9) ◽  
pp. 1464-1467 ◽  
Author(s):  
S T Wong ◽  
J Spoo ◽  
K C Kerst ◽  
T G Spring
Keyword(s):  
Whole Blood ◽  
Colorimetric Method ◽  
Direct Determination ◽  
Ion Pair ◽  
Photometric Method ◽  
Colorimetric Determination ◽  
Two Dimensional ◽  
Subsequent Formation ◽  
Blood Specimens

Abstract This spectrophotometric method for the direct determination of potassium in serum or plasma is based on the selective complexing of potassium by a specific macrocyclic polyether, with the subsequent formation of an ion-pair with a colored anion. The colored anion is extracted into an organic solvent, clarified by centrifugation, and then measured at 415 nm. The absorbance of the chromogen varies linearly with [K+] to at least 15 mmol/L. Results of this colorimetric method (y) correlate well with the results obtained by a flame-photometric method (y = 1.04x - 0.22, r = 0.97, n = 81), with CVs ranging from 2 to 4%. We observed no interferences from lipemia, added bilirubin, or various electrolytes. We also evaluated the use of this reagent in a new automated blood analyzer developed by Abbott, a two-dimensional centrifugal system (Clin Chem 31:1457-1463, 1985). Potassium determined with this system (y) correlated well with results by flame photometry: y = 1.02x + 0.02 (r = 0.94, n = 168). With this system one can use whole-blood specimens in measuring potassium.

Direct Colorimetric Determination of Hippuric Acid in Urine

1972 ◽  
Vol 18 (4) ◽  
pp. 349-351 ◽  
Author(s):  
Katsumaro Tomokuni ◽  
Masana Ogata
Keyword(s):  
Hippuric Acid ◽  
Colorimetric Method ◽  
Color Reaction ◽  
Colorimetric Determination ◽  
Benzenesulfonyl Chloride

Abstract A direct colorimetric method is described for determination of hippuric acid in urine. Hippuric acid dissolved in pyridine—water (1:1) produces a color (Amax = 410 nm) when benzenesulfonyl chloride is added. With the method based on this color reaction, urinary hippuric acid follows the Beer-Lambert law up to 1 mg/ml.

Colorimetric Determination of Dillapiole in Wheat

1979 ◽  
Vol 62 (1) ◽  
pp. 203-204
Author(s):  
Swadesh K Handa
Keyword(s):  
Sulfuric Acid ◽  
Colorimetric Method ◽  
Chromotropic Acid ◽  
Colorimetric Determination ◽  
Wheat Grain ◽  
Maximum Absorbance

Abstract A rapid colorimetric method has been developed for determining residues of dillapiole (3,4-methylenedioxy-5,6-dimethoxy allyl benzene) in wheat grain. Dillapiole is reacted with sulfuric acid to liberate formaldehyde which reacts with chromotropic acid to yield a pink compound with maximum absorbance at 575 nm. The method can detect 1—15 μg residue /ml.

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