Application of core–shell technology for determination of retinol and alpha-tocopherol in breast milk

Breast milk is a main source of fat-soluble vitamins for newborns and it is needful to monitor the nutritional status prior to its application. In this work a novel, high-throughput and low-cost method for monitoring of retinol and alpha-tocopherol in breast milk was developed, validated and compared with reference method using monolithic column. For this purpose five various porous shell and monolithic columns were tested on the basis of relationship between HETP and linear mobile phase velocity, analysis time and consumption of solvents. Finally the core–shell analytical column Kinetex C18 (2.6μm, 100Å, 100×4.6mm) was chosen as the best and optimal values of flow rate, injection volume and temperature of analysis were established. The detection of retinol and alpha-tocopherol was carried out at 325 and 295nm, respectively by diode array detector. The LOD 0.004μmol/L and 0.078μmol/L, the LOQ 0.012μmol/L and 0.182μmol/L for retinol and alpha-tocopherol, respectively were calculated. The validation data showed good linearity, repeatability of retention time with RSD 0.22% and 0.12%, repeatability of peak area with RSD 6.94% and 1.75%, recovery 114.1–116.3% and 99.0–108.6% for retinol and alpha-tocopherol, respectively. Moreover, the newly developed method substantially decreased the solvent consumption by about 263mL per 100 samples with the total time of analysis 1.75min in comparison with analysis time 1.80 of the reference method. ► Porous shell and monolithic columns technologies were tested, investigated and compared. ► Analytical column Kinetex C18 was chosen for determination of vitamins. ► Validated separation method was applied to real human breast milk samples.