2. Reagents and solutions
Lactose was purchased from Shanghai Second
Reagents Factory (China) and used without further pur-
ification. Three milk powder samples were Nestle soluble
milk powder, Campina Birch Tree full creammilk powder
and Anlene Hi-Calcium fat-free milk powder, respec-
tively. Each milk powder sample was carefully weighed
and dissolved with doubly distilled water, then ®ltered
with 0.22-mm te¯on ®lter paper (Shanghai Bandao Pur-
i®cation Material Factory, China). Prior to use, the
sample solution was diluted with the electrophoresis
medium (0.1 mol/l NaOH) to the required concentration.
NaOH (0.1 mol/l) solution was used as the electro-
phoresis medium. In this alkaline solution, copper work-
ing electrode shows excellent response to carbonhydrates
including lactose (Colon, Dadoo & Zare, 1993).