In the small intestine, lactose is split into galactose and glocose by the enzyme lactase. The monosaccharides can then be resorbed and metabolised. People with lactose intolerance suffer from flatulence and diarrhoea as a result of a shortage of lactose or reduced lactase activity. The lactose arrives in the colon unsplit, and is fermented by there by intestinal bacteria. These people are recommended to follow a lactose-free or low in lactose diet.
Lactose is extracted from the sample material aqueously. During quantification, interfering constituents are removed according to matrix (for example acetic acid protein precipitation, enzymatic splitting of disruptive monosaccarides and disaccarides). After separation using HPLC on a special column, and after electrospray ionisation using mass spectrometry (MS/MS), the lactose content is determined on the basis of characteristic disintegration of the quasi-molecule ions and formate adducts.
Fig 1-3: Quantifier 387 -> 161 (MRM of the molecule ion formate adduct)
With the aid of this method, in diverse matrices (for example nut nougat creme, milk powder) lactose can be selectively and precisely determined to a detection limit of 0.01g/100g.