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Question
Response
General
AOAC Method Number:
CHON-003
Method Title:
Chondroitin by IR and Dimethylmethylene Blue (DMMB)
Spectrophotometry
Method Author(s):
Not given
Reviewer Name:
Professor Nour Eddine ES-SAFI
Summary of Method
CHON-003 method presents results dealing with the use of
UV-visible spectrophotometry for the quantitative analysis
of chondroitin sulfate in raw material and finished products
after reaction with dimethylmethylene blue reagent.
Method Scope / Applicability:
Not Specific to CS
General Comments About the
Method:
The method is simple but critical in terms of time,
photometric determination at 525 nm and may be not
specific for chondroitinsulphate.
Although recent studies have demonstrated the efficiency of
DMMB over other assays this method suffers from multiple
drawbacks. The reagent used is unstable, interferences with
DNA or other negatively charged molecules seriously modify
the response, and, in addition, the GAG-dye complex is not
stable in solution, and GAG measurements are not accurate
because of this instability. Indeed, variations of the time
between sample measurements may modify results.
Furthermore, accuracy, precision, and linearity are poor and
even unacceptable at levels of less than 5mg/ml of GAGs.
Method Clarity
Poor
Pros/Strengths
Simple
Cons/Weaknesses
The dimehtylmethylene blue dye binding method used for
determination of galactosaminoglycan is not specific to
sulfated GAGs. The dye also reacts with negatively charged
polymers (e.g. hyaluronic acid and nucleic acids) and anions
to form metachromasia. It is important to know that the
color yield of metachromasia differs between CS
preparations with different structure.
CHON-003