A simple micro-batch ion-exchange resin extraction method coupled with reverse-phase HPLC (MBRE-HPLC) to quantify lactoferrin in raw and heat-treated bovine milk

Lactoferrin is an iron-binding cationic glycoprotein (pI = 8.7) beneficial for mammal health, especially udder and milk preservation. A new simple two-step method of quantification was developed. Lactoferrin in 1 mL of bovine skim milk was first adsorbed onto 100 mg of macroporous sulfonated-resin at pH 6.8 by rotary stirring for 90 min at 20-25 degrees C. After washing the resin, lactoferrin was desorbed using 1 mL of 2M NaCl containing phenylalanine as a dilution marker, then fully resolved and quantified by RP-HPLC at 220 nm using a wide-bore C4 silica column. This robust, inexpensive and flexible method improves selectivity (no protein interference) and sensitivity compared to previous HPLC methods. In-laboratory validation demonstrated its linearity (25 to 514 mu g Lf mL(-1)), accuracy (110 to 98% recovery), and precision (< 4%), which were comparable to immuno-based methods. The results for individual raw cow's milk were strongly correlated with results using an ELISA test.