Materials and Reagents

1. 1.5 ml microcentrifuge tube
   
2. 0.2 μm nylon filter (Sigma-Aldrich, catalog number: Z259969 )
   
3. 100 ml glass syringe
   
4. Pipette tip
   
5. Fresh Arabidopsis thaliana tissues (any plant part you want to test, 50-100 mg is sufficient)
   
6. L-cysteine (Sigma-Aldrich, catalog number: 778672 )
   
7. Gamma-glutamylcysteine (γ-Glu-Cys) (Sigma-Aldrich, catalog number: G0903 )
   
8. L-Glutathione reduced (Sigma-Aldrich, catalog number: G4251 )
   
9. Double distilled water (supplied by School of Life Sciences, University of Science and Technology of China)
   
10. Double distilled water
    
11. Hydrochloric Acid (HCl) (Sigma-Aldrich, catalog number: 435570 ) (see Recipes)
    
12. 2-(N-Morpholino)ethanesulfonic acid hydrate (MES) (Sigma-Aldrich catalog number: M8250 ) (see Recipes)
    
13. Ethylenediaminetetraacetic acid disodium salt dihydrate (EDTA^.2Na^.2H₂O) (Sangon Biotech, catalog number: A100105 ) (see Recipes)
    
14. Monobromobimane (mBBr) (Sigma-Aldrich, catalog number: 69898 ) (see Recipes)
    
15. Trifluoroacetic acid (TFA) (Sigma-Aldrich, catalog number: 302031 ) (see Recipes)
    
16. Acetonitrile (OCEANPAK, catalog number: Ac00030281 ) (see Recipes)
    

Equipment

1. Analytic balance (Mettler-Toledo International Inc., model: ML104 )
   
2. Mortar and Pestle
   
3. Refrigerated microcentrifuge (Thermo Fisher Scientific, Eppendorf, model: 5424R )
   
4. 37 °C degree incubator (Shanghai Jinghong Laboratory Instrument, model: GNP-9080 )
   
5. Reverse-phase C18 column (5 µm, 110A, 150 x 4.6 mm) (Phenomenex, model: Gemini C18 column ) or equivalent, guard column (Phenomenex, SecurityGuard Standard, model: AJ0-7597 )
   
6. HPLC equipment (Agilent Technologies, model: 1200 series )
   
   1. Pump (Agilent Technologies, model: G1312A )
      
   2. Sampler (Agilent Technologies, model: G1328A )
      
   3. Column heater (Agilent Technologies, model: G1316A )
      
   4. FLD detector (Agilent Technologies, model: G1321A )
7. 200 μl pipette
   
8. pH meter (Thermo Fisher Scientific, Mettler Toledo, model: FE20–FiveEasy Plus^TM )
   
9. Ultrasonic cleaner (Shanghai Sonxi Ultrasonic Instrument, model: DS-2510DT )
   

Software

1. Suitable data collection and processing software (Agilent Technologies, model: 1200 ChemStation)
   
2. Standard curve plotting (Microsoft Excel)
   

Procedure