Chemiluminescent determination of xanthine oxidase activity in milk

1999 ◽  
Vol 66 (3) ◽  
pp. 441-448 ◽  
Author(s):  
STEFANO GIROTTI ◽  
SANDRO LODI ◽  
ELIDA FERRI ◽  
GRAZIELLA LASI ◽  
FABIANA FINI ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Enzyme Activity ◽  
Detection Limit ◽  
Sample Preparation ◽  
Xanthine Oxidase ◽  
Milk Sample ◽  
Uht Milk ◽  
Milk Samples ◽  
Chemiluminescent Method

A chemiluminescent method for determining xanthine oxidase (XOD) activity was developed and applied to the assay of milk enzyme activity using a photomultiplier luminometer. Various kinds of milk and cream samples were analysed for XOD content. In pasteurized milk, XOD activity depended on the fat content and in UHT milk it disappeared owing to the heat treatment. Milk sample preparation was very simple, requiring only homogenization at 40°C followed by a 1[ratio ]10 dilution with UHT (‘XOD-free’) milk. The assay was carried out at 25°C. The response obtained from XOD standard solutions in milk was linear from 0·1 to 500 enzyme units (U) l−1, but for the actual milk samples values ranged only from 1 to 135 U l−1. The detection limit at 2 SD was 0·1 U l−1 in milk, while in buffer it was 100 times lower. The intra-assay and interassay CV for XOD activity in milk were 6–12%.

Fluorometric determination of uric acid in bovine milk

2010 ◽  
Vol 77 (4) ◽  
pp. 438-444 ◽  
Author(s):  
Torben Larsen ◽  
Kasey M Moyes
Keyword(s):  
Heat Treatment ◽  
Uric Acid ◽  
Xanthine Oxidase ◽  
Bovine Milk ◽  
Oxidase Inhibitor ◽  
Enzymatic Oxidation ◽  
Fast Method ◽  
Xanthine Oxidase Inhibitor ◽  
Milk Samples

The primary objective of this study is to validate a new fast method for determination of uric acid in milk. The method is based on an enzymatic-fluorometric technique that requires minimal pre-treatment of milk samples. The present determination of uric acid is based on the enzymatic oxidation of uric acid to 5-hydroxyisourate via uricase where the liberated hydrogen peroxide reacts with 10-acetyl-3,7-dihydroxyphenoxazine via peroxidase and the fluorescent product, resorufin, is measured fluorometrically. Fresh composite milk samples (n=1,072) were collected from both Jersey (n=38) and Danish Holstein (n=106) cows from one local herd. The average inter- and intra-assay variations were 7·1% and 3·0%, respectively. Percent recovery averaged 103·4, 107·0 and 107·5% for samples spiked with 20, 40 or 60 μmof standard, respectively, with a correlation (r=0·98;P<0·001) observed between the observed and expected uric acid concentrations. A positive correlation (r=0·96;P<0·001) was observed between uric acid concentrations using the present method and a reference assay. Storage at 4°C for 24 h resulted in lower (P<0·01) uric acid concentrations in milk when compared with no storage or samples stored at −18°C for 24 h. Addition of either allopurinol (a xanthine oxidase inhibitor) or dimethylsulfoxide (a solvent for allopurinol) did not affect milk uric acid concentrations (P=0·96) and may indicate that heat treatment before storage and analysis was sufficient to degrade xanthine oxidase activity in milk. No relationship was observed between milk uric acid and milk yield and milk components. Authors recommend a single heat treatment (82°C for 10 min) followed by either an immediate analysis of fresh milk samples or storage at −18°C until further analysis.

scholarly journals Simultaneous Determination of C18 Fatty Acids in Milk by GC-MS

Separations ◽  
2021 ◽  
Vol 8 (8) ◽  
pp. 118
Author(s):  
Meiqing Chen ◽  
Yangdong Zhang ◽  
Fengen Wang ◽  
Nan Zheng ◽  
Jiaqi Wang
Keyword(s):  
Fatty Acids ◽  
High Sensitivity ◽  
Raw Milk ◽  
Uht Milk ◽  
Milk Samples ◽  
Accuracy And Precision ◽  
Different Temperatures ◽  
Chromatographic Resolution ◽  
Commercial Milk

The determination of C18 fatty acids (FAs) is a key and difficult aspect in FA profiling, and a qualified method with good chromatographic separation and high sensitivity, as well as easy methylation, is required. A GC-MS method was established to simultaneously determine C18 FAs in milk. To simplify the methylation protocol for milk samples, besides a base-catalyzation methylation (50 °C for 20 min), the necessity of an additional acid-catalyzation was also studied using different temperatures (60 °C, 70 °C, 80 °C, and 90 °C) and durations (90 min and 150 min). The results showed that the chromatographic resolution was improved, although three co-eluted peaks existed. The base-catalyzation was sufficient, and an additional acid-catalyzation was not necessary. The proposed method was validated with good sensitivity, linearity, accuracy, and precision, and then applied in determining C18 FAs in 20 raw milk and 30 commercial milk samples. UHT milk presented a different profile of C18 FAs from raw milk and PAS milk samples, which indicated that excessive heating could change the profile. Overall, the proposed method is a high-throughput and competent approach for the determination of C18 FAs in milk, and which presents an improvement in chromatographic resolution and sensitivity, as well as a simplification of methylation.

scholarly journals Sestavení kompetitivní enzymové imunoanalýzy pro stanovení α-laktalbuminu  a β-laktoglobulinů kravského mléka

1999 ◽  
Vol 17 (No. 1) ◽  
pp. 5-14 ◽  
Author(s):  
L. Karasova ◽  
P. Rauch ◽  
L. Fukal
Keyword(s):  
Capillary Electrophoresis ◽  
Milk Sample ◽  
Polyclonal Antibodies ◽  
Whey Proteins ◽  
The Other ◽  
Milk Samples ◽  
Heat Treated ◽  
Very High ◽  
Raw Cow’S Milk

Polyclonal antibodies were raised against three immunogens- a-lactalbumin (LA), -lactoglobulin A (LGA) and B (LGB). Using these antibodies the procedures of an indirect competitive enzyme immunoassay (ELISA) were constructed, optimized a nd characterized for determination of indi vidual immunogens. It was found that ELISA of LA is very specific without any inter­ ferences of other whey proteins. However, in ELlSAs of both lactoglobulins A and B were demonstrated very high interferences of the other genetic varian t (cross-reactivities  20-280% depending on antibody and immu nogen). An excellent sensitivity of ELISA for all proteins (detection limits for LA, LGA and LGB were 13, 0.4 and 54 ng/ml, respectively) makes it possible to analyze milk samples diluted more than 1000 times. Average values of variation coefficient were in the range 16-27%. A compari­ son of whey protein determinations in raw cow's milk by ELISA and by capillary electrophoresis resulted in the best similarit y in results of LA concentration. The decrease of LA, LGA and LGB concen trations was detected by using capillary electrophoresis for an analysis of whey from heat-treated milk, while ELISA of the same milk sample showed the increase of LGB immunoreac­ tivity to 700%.

scholarly journals Detection by multiplex PCR of Staphylococcus aureus , S. intermedius and S. hyicus in artificially contaminated milk

2016 ◽  
Vol 46 (8) ◽  
pp. 1418-1423
Author(s):  
Eliezer Avila Gandra ◽  
Maria Aparecida Fernandez ◽  
Jorge Adolfo Silva ◽  
Wladimir Padilha da Silva
Keyword(s):  
Detection Limit ◽  
Multiplex Pcr ◽  
Target Species ◽  
Bacterial Strains ◽  
Detection Thresholds ◽  
Uht Milk ◽  
Milk Samples ◽  
Whole Milk ◽  
Species Specific ◽  
Coagulase Positive Staphylococcus

ABSTRACT: This research aimed to detect coagulase-positive Staphylococcus (CPS) directly in samples of artificially contaminated milk, using multiplex PCR (mPCR). Standard and isolated bacterial strains of S. aureus, S. epidermidis, S. hyicus, S. intermedius, Listeria monocytogenes and Escherichia coli species were used, evaluating the specificity and detection limit of mPCR, for artificially contaminated UHT milk. Primers specific for the nuc gene (NUC1-NUC2 were used for S. aureus, NUC3-NUC4 for S. hyicus and NUC5-NUC6 for S. intermedius). It was possible to detect the three target species by mPCR, directly from bovine whole milk, with adequate specificity and acceptable detention limit for identification of coagulase-positive Staphylococcus (CPS) in foods. The specificity was determined by the amplification of species-specific fragments, and the detection limit was assessed by the detection thresholds obtained for the three species (103 CFU mL-1). From these results, the mPCR described, with the proposed set of primers, has the potential for use in precise identification and differentiation between CPSs in milk samples.

scholarly journals Determination of Sodium Azide in Beverages by Ion Chromatography

2000 ◽  
Vol 83 (6) ◽  
pp. 1410-1414 ◽  
Author(s):  
Harumi Oshima ◽  
Eiji Ueno ◽  
Isao Saito ◽  
Hiroshi Matsumoto
Keyword(s):  
Detection Limit ◽  
Sample Preparation ◽  
Sodium Hydroxide ◽  
Ion Chromatography ◽  
Sodium Azide ◽  
Convenient Method ◽  
Sodium Hydroxide Solution ◽  
Hydrazoic Acid ◽  
Suppressed Conductivity Detection

Abstract A convenient method for determination of sodium azide in beverages using ion chromatography is described. This method combines the specificity for azide with a simple sample preparation using a bubble and trap apparatus that removes any interferences. Sodium azide in a sample was acidified, and the azide was converted to the volatile hydrazoic acid, which was trapped in 2.5mM sodium hydroxide solution. Determination was performed by isocratic ion chromatography using suppressed conductivity detection. Calibration curves were linear for 0.5 to 20 μg/mL sodium azide and the detection limit was 0.05 μg/mL. Recoveries of sodium azide from spiked samples (10.0 μg/g) were more than 82.6%. The method was then used to analyze various beverages.

scholarly journals LC-MS/MS Determination of 21 Non-Steroidal Anti-Inflammatory Drugs Residues in Animal Milk and Muscles

Molecules ◽  
2021 ◽  
Vol 26 (19) ◽  
pp. 5892
Author(s):  
Marta Pietruk ◽  
Piotr Jedziniak ◽  
Małgorzata Olejnik
Keyword(s):  
Sample Preparation ◽  
European Commission ◽  
Coefficient Of Variation ◽  
Chromatographic Separation ◽  
Chromatographic Column ◽  
Commission Decision ◽  
Milk Samples ◽  
Animal Milk ◽  
Inflammatory Drugs

The presented procedure combines experience from two LC-MS/MS methods previously developed by our team for NSAIDs determination in meat and milk. The novelty was a modification of sample preparation and combining LC-MS/MS method for milk and muscle. The clean-up procedure was investigated, leading to a change from SPE to dSPE with C18 bulk sorbent. Unlike most of the existing methods, chromatographic separation was achieved on a C8 chromatographic column. This method was developed and validated under European Commission Decision 2002/657/EC. Recovery for milk samples values between 86.3% to 108%, with the coefficient of variation, varied from 5.51% to 16.2%. The recovery for muscle was calculated to be between 85.0% and 109%, and the coefficient of variation was—4.73% to 16.6%. The validation results prove that the method is suitable for confirmatory purposes in milk and muscle. Of 452 samples tested in 2019 and 2020, two have been identified as non-compliant.

The Determination of Quartz in Perlite by X-ray Diffraction

1989 ◽  
Vol 33 ◽  
pp. 493-497 ◽  
Author(s):  
R. D. Hamilton ◽  
N. G. Peletis
Keyword(s):  
Detection Limit ◽  
Sample Preparation ◽  
Accurate Determination ◽  
Analytical Techniques ◽  
Crystalline Silica ◽  
X Ray Diffraction ◽  
X Ray ◽  
Precision And Accuracy ◽  
Improved Technique

AbstractIARC's designation of crystalline silica as a “probable carcinogen” triggered the requirement to label products containing greater than 0.1 % crystalline silica. For perlite and other materials which may contain crystalline silica in levels close to 0.1% an accurate determination is critical from both legal and marketing considerations.Existing analytical techniques for the determination of crystalline silica at levels of less than 1.0% were found to be inadequate to meet the new requirements. An improved technique based on x-ray diffraction has been developed specifically to analyze perlite for crystalline silica, which occurs largely in the form of quartz, at the 0.1%. level. The technique employs long counting times and improved sample preparation and mounting to increase both precision and accuracy, and to lower the detection limit to less than 0.1%.The technique was tested on a large number of samples from a variety of sources and proven to give excellent results for all types of expanded perlites and perlite ores. The procedures developed are applicable to a wide variety of materials in addition to perlite.

Ratio of Lactulose to Furosine as Indicator of Quality of Commercial Milks

1994 ◽  
Vol 57 (8) ◽  
pp. 737-739 ◽  
Author(s):  
NIEVES CORZO ◽  
TERESA DELGADO ◽  
ESPERANZA TROYANO ◽  
AGUSTIN OLANO
Keyword(s):  
High Temperature ◽  
Ambient Temperatures ◽  
Uht Milk ◽  
Milk Samples ◽  
Powder Milk ◽  
Reconstituted Milk ◽  
Ultra High Temperature

Storage of ultra high temperature (UHT) milk at high ambient temperatures gave rise to a decrease of the ratio of lactulose to furosine contents. The lactulose/furosine (Lu/Fu) ratio in UHT milks resulted to be around 16 times higher than in commercial powder milk samples so, the determination of the Lu/Fu ratio in freshly processed UHT milk seems to be useful to detect the presence of reconstituted milk.

Determination of polybrominated diphenyl ethers in milk samples. Development of green extraction coupled techniques for sample preparation

2016 ◽  
Vol 38 (3-4) ◽  
pp. 460-468 ◽  
Author(s):  
Paula Berton ◽  
Sabrina B. Mammana ◽  
Daniela A. Locatelli ◽  
Nerina B. Lana ◽  
María B. Hapon ◽  
...  
Keyword(s):  
Sample Preparation ◽  
Polybrominated Diphenyl Ethers ◽  
Green Extraction ◽  
Milk Samples ◽  
Diphenyl Ethers ◽  
Coupled Techniques

Chemiluminescence Detection of Nitrite in Nonfat Dried Milk Powders

1982 ◽  
Vol 65 (3) ◽  
pp. 616-618
Author(s):  
Robert C Doerr ◽  
Robert A Gates ◽  
Walter Fiddler
Keyword(s):  
Statistical Analysis ◽  
Sample Preparation ◽  
Colorimetric Method ◽  
Chemiluminescence Detection ◽  
Milk Samples ◽  
Dry Milk ◽  
Nonfat Dry Milk ◽  
No Sample Preparation

Abstract Determination of nitrite in nonfat dry milk powders by chemiluminescence detection was compared with a colorimetric method specifying Griess reagents. The chemiluminescent technique requires no sample preparation, is free from apparent interferences, and is sensitive to 25 ppb nitrite. Statistical analysis shows no difference at P = 0.05 between the colorimetric and chemiluminescent methods, based on the analysis of 16 commercial nonfat dry milk samples.

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