Cyclodextrin-Modified Micellar UPLC for Direct, Sensitive and Selective Determination of Water Soluble Vitamins in Milk.

Cyclodextrin-modified micellar ultra pressure liquid chromatography (CD-MUPLC) was firstly developed and directly applied to the simultaneous determination of water-soluble vitamins thiamine hydrochloride (VB1), pyridoxine hydrochloride (VB6) and ascorbic acid (VC) in milk samples. A hybrid isocratic mobile phase consisting of β-cyclodextrin (β-CD, 5.0 mmol L-1) and cetyltrimethylammonium bromide (CTAB, 0.1 mol L-1) in the presence of acetic acid (0.1 mol L-1) at pH 2.9 on a RP-C18 column at 25.0°C was successfully used. The separation of vitamins was achieved in less than 10 min at a 0.2 mL min-1 flow rate showing adequate linearity at 245 nm in the ranges of 5.0-500.0 μg L-1 for VB1, 5.0-1000.0 μg L-1 for VB6 and 5.0-10000.0 μg L-1 for VC with coefficients of variation (r2) of 0.9999, 0.9987 and 0.9971, respectively. In addition, limits of detection obtained were 0.885, 1.352 and 1.358 μg L-1 and limits of quantification were 2.681, 4.096 and 4.115 μg L-1 for VB1, VB6 and VC, respectively. The high sensitivity of the proposed CD-MUPLC-UV method permitted its applications to the determination of water-soluble vitamins VB1 (32-488 μg L-1), VB6 (82-95 μg L-1) and VC (790-45000 μg L-1) in breast and bovine milk samples. The relative standard deviations and recoveries ranged between 0.07 and 2.14% and between 85.27 and 114.8%, respectively, indicating the accurate and precise measurements without any negative impact of matrix. The current analytical method illustrated several advantages including direct, sensitive, selective and non-consuming organic solvents over the hitherto published methods. These features could be attributed to the four-point competitive interactions among analytes, pseudostationary phases and modified C18 stationary phases.