Nelson-Somogyi Method: Understanding Blood Glucose Metabolism Testing

Nelson-Somogyi Method

The Nelson-Somogyi method is a colorimetric assay for the determination of glucose in blood or other biological fluids. It is based on the reduction of cupric ions to cuprous ions by glucose, which is then quantified by the formation of a colored complex with arsenomolybdate.

Principle

The Nelson-Somogyi method is based on the following reactions:

1. Glucose + Cu2+ → Gluconic acid + Cu+

2. Cu+ + Arsenomolybdate → Arsenomolybdate-Cu+ complex (blue color)

Procedure

1. To a test tube, add 1 mL of blood or other biological fluid.

2. Add 5 mL of Nelson-Somogyi reagent (a mixture of copper sulfate, sodium carbonate, and sodium arsenate).

3. Mix well and heat the mixture in a boiling water bath for 15 minutes.

4. Cool the mixture to room temperature and add 1 mL of arsenomolybdate reagent (a mixture of ammonium molybdate, sulfuric acid, and sodium arsenite).

5. Mix well and let the mixture stand for 10 minutes.

6. Read the absorbance of the solution at 540 nm using a spectrophotometer.

Calculations

The concentration of glucose in the sample can be calculated using the following formula:

```

Glucose concentration (mg/dL) = Absorbance × 100

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Reference Range

The normal range for blood glucose levels in adults is 70-110 mg/dL.

Clinical Significance

The Nelson-Somogyi method is a simple and reliable method for the determination of blood glucose levels. It is used in the diagnosis and management of diabetes mellitus and other conditions that affect glucose metabolism.