SPDS Set 1 ERP Book

CHON-003

Question

Response

General

AOAC Method Number:

CHON-003

Chondroitin by IR and Dimethylmethylene Blue (DMMB) Spectrophotometry

Method Title:

Method Author(s):

Not given

Reviewer Name:

Professor Nour Eddine ES-SAFI

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.

Summary of Method

Method Scope / Applicability:

Not Specific to CS

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.

General Comments About the Method:

Method Clarity

Poor

Pros/Strengths

Simple

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.

Cons/Weaknesses