Ion Suppression Study for Tetracyclines in Feed

Table 1

Sample pretreatment methods tested for the cleanup of tetracyclines from animal feeds.

	Method
	1	2	3	4
Extraction	40 mL McIlvaine buffer-EDTA 0,1 M	40 mL DCM McIlvaine buffer-EDTA 0,1 M (1 : 3)	40 mL McIlvaine buffer-EDTA 0,1 M	40 mL McIlvaine buffer-EDTA 0,1 M
SPE; Loading pH	4.2	4.2	2.5	10
Cartridge	Oasis HLB (60 mg)	Oasis HLB (60 mg)	Oasis MCX (60 mg)	Oasis MAX (60 mg)
Wash (2 mL)	H2O	H2O	(1) FA 2% (v/v)	(1) NH3
			(2) MeOH	(2) MeOH
Elution (2 mL)	MeOH	MeOH	MeOH : NH3 (95 : 5)	MeOH : FA (95 : 5)
Final step	Evaporation with N2 and reconstitution with mobile phase	Evaporation with N2 and reconstitution with mobile phase	Dilution with 8 mL acetic acid 10% (v/v)	Dilution with 8 mL H2O (v/v)