( ne divinyl benzene polymer (1 cc/25 mg)...)Determination of the Chloramphenicol residues in milk and milk products using LC/MS/MS

ne divinyl benzene polymer (1 cc/25 mg) were used for solid phase extractions. After solid phase extraction and drying under nitrogen the sample was redissolved in water and then filtered on a 0.45 μm cellulose filter. An Agilent 1100 Series HPLC equipped with an autosampler and degasser (Agilent, Palo Alto, CA, USA) was used for chromatographic analysis in this study. Eluent A consists of H2O with 2 mM ammonium acetate and eluent B is methanol. A 50μL sample was injected onto a Luna column (50 mm x 2.0 mm, 3 μm particle size) (No. 008-4256-B0 Phenomenex, Torrance, CA, USA) equipped with a guard column (No. AJ0-4350, Phenomenex, Torrance, CA, USA). The sample was eluted with the following gradient at a flow rate of 350 μL/min:

An API 3000 LC/MS/MS system with a TurboIonSpray source was operated in the negative ion mode using the following parameters:

Nebulizer gas (air): 8

Curtain gas (N2): 10

CAD gas (N2): 7

Dwell time: 250 ms/MRM transition

Temperature: 400C

Ion spray voltage (IS): -3500

Entrance potential (EP): 10

Declustering potential (DP): -30

Focusing potential (FP): -300

Cell exit potential (CXP): -15

The collision energy (CE) was optimized for each of the 4 MRM transitions monitored throughout the HPLC run. The collision energy for each MRM transition is listed below:

Under these conditions, the m/z 152 product ion was the base peak (Figure 3).

Results and Discussion

Commission Decision 2002/657/EC set the performance criteria for mass spectrometric detection as a confirmatory method following either an on-line or an off-line chromatographic separation. When mass fragments are measured a system of identification poi
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