GGA, What is it?

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Glucose and Glutamic acid (GGA)

This is the material used in the BOD test in order to make sure that the seed is producing sufficient but not excessive oxidative potential. This allows the BOD test to be standardized. The GGA is not itself a "standard" per se, but it is a standardizing solution. The results of the GGA bottle are also used as a control for the test. The wise analyst will make sure to increase seeding if the GGA is heading low, or to decrease seeding if the GGA is headed higher. Commercial formulations of this are available.



Glucose is a simple sugar and is the base of the cellulose molecule. Since this molecule is the base unit of many other types of organic matter, it is a primary food source for microorganisms and as a result makes an ideal material for setting seed strength in the BOD test. In the BOD test there should be 150 mg/L of this material in the GGA.

Glutamic Acid


Glutamic acid is one of the essential amino acids. It is added to the BOD "Standard" GGA in order to stabilize the response. It was found that with glutamic acid the expected value was more reproducible than it was without. In the BOD test there should be 150 mg/L of this material in the GGA.

Problems with Preparation

The glucose and glutamic acid must both be dried before use. If this drying is not done correctly then it is possible that low GGA will result. Weighing the material is crucial as the standard must be weighed very carefully to be very close to 150 mg/L of each material exactly. The third problem with preparation is that the material is light and easy to dislodge before dissolution. The final and last opportunity for error is that the material might be under diluted or over diluted.

Commercial Formulations

It is recommended that a commercial formulation is used for the preparation of the GGA. Behind blank and seed issues the GGA is the the third most likely issue in the BOD test. The following link will take you to one of the most trusted of these.

Hach Glucose and Glutamic Acid (GGA)

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