Summary of the adopted conditions of bar-μ-SPE-HPLC method using graphene and zeolite as adsorbent^a.

Conditions	Graphene	Zeolite	Zeolite : graphene
Conditioning solvent	ACN	ACN	ACN
pH of sample solution	10	3	6
Volume of sample solution, mL	10	10	10
Amount of adsorbent	10 mg	25 mg	24.5 mg : 10.5 mg
Rotating speed, rpm	800	800	800
Time of extraction, min	90	120	120
Ionic strength, % NaCl	0	0	0
Solvent for desorption	0.1 M IP in IPA	0.1 M IP in ACN	7 : 3 (ACN : IPA) + 0.1 M IP
Time of desorption, min	30	30	30
Volume of desorption solvent, mL	0.6	0.6	0.6

^aIP: ion-pair (sodium heptanesulphonate).