Lc ms ms grade formic acid

Acetamiprid, flonicamid, thiacloprid, thiamethoxam,
and nitenpyram standard solutions were purchased from Accustandard
(New Haven, CT, USA) with purity ≥99.7%. Imidacloprid and clothianidin
were purchased from Sigma-Aldrich (St. Louis, MO, USA) with purity
of 99.9%. Dinotefuran was purchased from Chem Service (West Chester,
PA, USA) with purity of 99.2%. The isotope-labeled internal standards
(IS) for Imidacloprid-d₄ (99.2%), clothianidin-d₃ (98.9%), and thiamethoxam-d₃ (99.8%) were purchased from C/D/N Isotopes, Inc. (Quebec,
Canada). LC-MS/MS grade formic acid and ammonium formate were purchased
from Sigma-Aldrich. HPLC grade reagents, including acetonitrile and
water, were purchased from J. T. Baker (Center Valley, PA, USA). Vial
(1.5 mL with 0.2 μm nylon filter) were purchased from VWR international
(Radnor, PA, USA). QuEChERS extraction salt packages, which include
4 g of MgSO₄, 1 g of NaCl, 1 g of sodium citrate, and 500
mg of of disodium citrate sesquihydrate in each salt pack, and 2 mL
of QuEChERS dispersive SPE containing 50 mg of PSA + 50 mg of C18
+ 150 mg of MgSO₄ or 50 mg of PSA + 50 mg of graphitized
carbon black (GCB) + 150 mg of MgSO₄ or 25 mg of PSA +
7.5 mg of GCB + 150 mg of MgSO₄ ceramic homogenizer were
purchased from Agilent Technologies (Santa Clara, CA, USA).