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How sweet is your HPLC?


Sugar is a simple carbohydrate belonging to a class of chemically-related sweet-flavored substances. Since sugars are omnipresent in our life, we need the tools and applications to reliably analyse or purify them.

Sugars typically found in foods and beverages are monosaccharides (galactose, glucose, and fructose) and disaccharides (sucrose, lactose, and maltose). Sorbitol, xylitol, mannitol and erythritol are a type of sugar alcohol that because of their relative sweetness, are also used as sweeteners.

We were all told as children that too much sugar rots our teeth. However, the adverse effects of sugar according to health organisations can be even more drastic than dental issues. The WHO (World Organization of Health) and American Heart Association urge people to restrict their added sugar intake due to their association with obesity, heart disease and type II diabetes.

To keep control of sugar levels, it is helpful to know how much sugar there is in the food and beverages we consume. Nutritional labelling is a great controlling aid, as food products are required to list sugar and total carbohydrate content. The measurement of sugars in food stuffs are typically carried out via HPLC.

Another issue facing the food and beverage industry is adulteration. Good examples are wine and honey. The price of natural bee honey is much higher than other sweeteners making it susceptible to adulteration with cheaper sweeteners, primarily sucrose. As well as sucrose, high fructose corn syrup and lactose (high in calories) are added to some foods to increase sweetness at a low cost. Adulteration can often be monitored via HPLC.

Sugars and sugar alcohols display almost no ultraviolet absorption, and are therefore typically detected using a differential refractive index detector (RID), evaporative light scattering detector or electrochemical detector. The choice of detector depends on the method type (gradient or isocratic) and sensitivity required. Refractive index detection is a so-called universal detection method that can detect almost any sample components that have a different refractive index from the mobile phase. This detection method is the most common for sugars, arguably due to its low cost and robustness.

The KNAUER dedicated AZURA Analytical Sugar System is equipped with a differential refractive index detector (AZURA RID 2.1L), an isocratic pump (AZURA P 6.1L), manual injection valve and column thermostat (AZURA CT 2.1) and is compatible with a range of separation columns. This simple and low maintenance system offers a price optimised configuration, able to cover a wide range of standard applications.

Preparative HPLC can be readily used to purify monosaccharides and their simple derivatives from synthetic or natural matrices. A similar system to the AZURA Analytical Sugar System is the dedicated AZURA Semi-Preparative Sugar System. This system can be operated up to 10 ml/min, and the extended dynamic range of the included refractive index detector make the system appropriate for analytical and semi-preparative purposes. The extended dynamic range option enables the linear dynamic range of the AZURA RID 2.1L to be broadened in +100  per cent (-1000 µRIU offset) or -100 per cent (+1000 µRIU offset). This prevents the need to dilute samples, which saves time and money and diminish additional errors during sample preparation (e.g. pipetting errors).

The analysis and purification of sugars is an essential task for increasing awareness and improving health. Simple KNAUER system solutions are available for fulfilling the modern challenges facing the food and beverage industries.


  • Routine analysis of ingredients in wine
  • Simplified scale up for sugars
  • Xylitol HPLC extraction from fermented biomass
  • Semi-preparative xylitol purification

Contact Details:
KNAUER Wissenschaftliche Geräte GmbH
Hegauer Weg 38,
14163 Berlin, Germany
+49 30 809727-0,
+49 30 8015010 (Fax)

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