Today, just like to do something to kill the time....
The Difficulty is How to isolate/remove the polar pigments (chlorophyll and carotinoids) /fatty acids, organic acids before LC-MS/ GC-MS?
Strongly recommend the combine of PSA and GCB (PSA= primary-secondary amine, GCB = graphitized carbon black)
Steps:
(1) Sample preparation and extraction
Sample: 10g of cucumber/strawberries were homogenized and placed in a 50mL PTFE centrifuge tube.
Solvent: 10mL of acetonitrile were added to homogenate Shake for 1 minute, until uniform
Salts: 4.0g MgSO4 (anhydrous powder or granular), 1.0g NaCl, 1.0g trisodium citrate dihydrate
0.5g disodium hydrogencitrate sesquihydrate
Salts were added and vigorously shaken for 1 minute. Sample was centrifuged and the supernatant removed for cleanup. Pesticides standards (200ng/mL) were spiked in at this point
(2) Sample extract cleanup ( Here, Do not recommend any brand to hurt "Fair Play Spirit" )
1mL of supernatant from the previous step was placed into several 2mL polypropylene centrifuge tubes, each containing one of the following adsorbent mixes:
• 500 mg PSA
• 250-300 mg GCB,
• 1.2 g MgSO4
• 4.0 mL Acetone/Toluene(3/1)
• Shake and Centrifuge
Samples were shaken with the adsorbents for 30 seconds (carbon for 2 minutes), then centrifuged to produce a clear supernatant for GC/MS analysis.
GC-MS:
Column: A 30m, 0.18mm ID, 0.14µm.
Sample: Custom pesticide mix 200µg/mL each pesticide,
Inj.: 1.0µL splitless (Hold 1 min.)
Inj. temp.: 250°C
Carrier gas: Helium
Flow rate: Constant linear velocity @ 40cm/sec
Oven temp.: 40°C (hold 1 min.) to 320°C @ 12°C/min.
Det: Aiglent 6890N-5973 MSD
Transfer line temp.: 300°C
Ionization: Electron ionization
Mode: Selected ion monitoring (SIM)
Results:
Should soak/wash the fruits before eating
email me if want the assay results (not public, not panic).
