Application Notes: Reflectometry – Glucose in Honey

Reflectometric determination after conversion with glucose oxidase and peroxidase

Reagents:

Cat. No. 116720 Reflectoquant® Glucose Test
Cat. No. 117246 Reflectometer RQflex® 20

This application note pertains to RQflex® 20 and all discontinued instruments (RQflex® 10, RQflex® plus)

Sample preparation:
Homogenize the honey sample by stirring with a glass rod. Exactly weigh 1.0 g of honey into a 200-ml glass beaker and with stirring dissolve with 80 ml of distilled water. Quantitatively transfer to a 100-ml volumetric flask, make up to the mark with distilled water, and mix thoroughly. Subsequently draw off 1.0 ml, place this volume in a 25-ml volumetric flask, and make up to the mark with distilled water. Use this sample for the analysis.

honeycomb

Note:
In aqueous solution, the α form and the β form of glucose are in equilibrium (mutarotation). In the Reflectoquant® Glucose Test the determination takes place via the β form of glucose. After the Glucose has dissolved, before the analysis it is hence essential to leave the solution to stand until equilibrium has been reached. In liquid honey the glucose is already in equilibrium and the sample can be used for the analysis directly after the sample preparation procedure.

In the case of crystalline honey the following procedure applies:

Leave the crystalline honey to stand for 2 hours after the sample-preparation procedure and subsequently use for the analysis.

Alternatively, with stirring dissolve crystalline honey with 80 ml of distilled water previously heated to approx. 90 °C. Allow to cool to room temperature and subsequently transfer quantitatively to a 100-ml volumetric flask, make up to the mark with distilled water, and mix thoroughly. Subsequently draw off 1.0 ml, place this volume in a 25-ml volumetric flask, and make up to the mark with distilled water. The sample prepared in this manner can be used directly for the analysis.


Analysis:

Press the START button of the reflectometer and at the same time immerse both reaction zones of the test strip in the prepared sample (15 - 30 °C) for 15 seconds. Subsequently remove the strip and allow excess liquid to run off via the long edge of the strip onto an absorbent paper towel. After 60 seconds measure the test strip in the reflectometer. The result [mg/l] is automatically stored. (Please refer to the RQflex® operating instructions and the package insert of the Reflectoquant® Glucose Test.)

Calculation:

Glucose content [g/kg] = Result [mg/l] x 10
Sample weight [g]


Measurement results - comparison with the enzymatic method:

Sample Reflectoquant® [g/kg] Enzymatic [g/kg]
1 311 320
2 306 315
3 418 412

Materials

     
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