After careful optimization, the microemulsion samples were
prepared in 15.0 mL polypropylene bottles. The resultant mixture that
formed microemulsion consisted of 1.00 g of biodiesel, 0.100 mL conc.
HNO3, 0.250 mL 2% (w/v) CsCl, for sodium and potassium determination,
or 0.250 mL 2% (w/v) KCl, for calcium and magnesium determination,
as ionization suppressor, and 1.15mL 0.2% (v/v) HNO3, diluted
with n-propanol to 10.0 mL. Soon after that, it was hand shaken
resulting in a visually homogeneous system. Analytical microemulsions
were prepared in the same way, replacing the samples with organometallic
standards.