Experimental
Chemicals
Melamine (108-78-1) and Cyanuric Acid
(108-80-5) standards were obtained from
Sigma-Aldrich.
Extraction
Liquid-Liquid-Extraction (LLE) of pet
food samples was performed using
the following procedure:
•
Add 5mL of acetonitrile to 5g
of homogenized sample
•
Mix thoroughly and let stand for
15-30 minutes
•
Add 5mL of saturated NaCl, mix and
let stand for another 15-30 minutes
•
Separate by centrifugation and
inject the top layer
Further dilution of the extract with water/
acetonitrile (50/50) might be necessary if
the sample is heavily contaminated.
Liquid Chromatography
A Shimadzu Prominence LC system
containing a CBM-20A system controller,
two LC-20AD pumps, a semi-micro
gradient mixer SUS-20A, and a SIL-20AC
autosampler was used. Separation
was performed on a GL Science Inertsil
HILIC 5μm (150x3mm) column at a temperature of 40°C with a mobile
phase of (A) acetonitrile + 10mM
ammonium acetate and (B) water +
10mM ammonium acetate at a flow of
0.5mL/min. The gradient using normal
phase conditions is listed in Table 1.
An injection volume of 5μL was used.
Mass Spectrometry
An API 3200™
LC/MS/MS System
equipped with Turbo V™
source and
Electrospray Ionization (ESI) probe was used to detect both targeted analytes in
Multiple Reaction Monitoring (MRM)
mode. Precursor and product ions with
corresponding Declustering Potentials
(DP) and Collision Energies (CE) of the
detection of Cyanuric Acid in negative
polarity and Melamine in positive
polarity