Application Notes: Reflectometry – Hydroxymethylfurfural (HMF) in honey

Reflectometric Determination after Conversion with a Barbituric Acid Derivative and an Aminophenazone Derivative

Reagents:

Prod. No. 117952 Reflectoquant^® Hydroxymethylfurfural (HMF) Test
Prod. No. 117246 Reflectometer RQflex^® 20
Prod. No. 116754 Water for analysis
Prod. No. 116730 Reflectoquant^® Blank Strips
Prod. No. 117989 Test vessels

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

Sample Preparation

Weigh 2.5 g of honey into a test vessel, dissolve with approx. 4 mL of water for analysis, transfer quantitatively to a 10-mL volumetric flask, and make up to the mark with water for analysis. Prepare larger sample volumes according to the above instructions as necessary.

Blank

Every type of honey gives rise to a more or less intense blank value depending on its intrinsic color. This blank value is determined by immersing a blank strip into the prepared honey sample solution and measuring it in the reflectometer. Select the HMF method beforehand by means of the bar code.

It is advisable to take the blank value into consideration even when light-colored types of honey are being investigated.

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 1 second. Allow excess liquid to run off via the long edge of the strip onto an absorbent paper towel.

Approx. 10 seconds before the end of the reaction time, insert the test strips all the way into the strip adapter with the reaction zones facing the display.

After the end of the reaction time, read off the result from the display in mg/l hydroxymethylfurfural.

The result [mg/l] is automatically stored. (Please refer to the RQflex^® operating instructions and the package insert of the Reflectoquant^® Hydroxymethylfurfural (HMF) Test.)

Calculation

HMF content [mg/kg] = (measurement result [mg/l] - blank [mg/l]) x 4 / 1.4

Measurement Results

A series of tests with 50 different types of honey were measured with the Reflectoquant^® HMF Test. The results were compared with those obtained using the official DIN methods DIN 10751-3 (HPLC). The factor of 1.4 used in the calculation formula is used to balanced effects of the honey matrix on the test.

Figure 1. HMF Reflectoquant versus HPLC