Comparison of the Usefulness of SPE Cartridges for the Determination of β-Blockers and β-Agonists (Basic Drugs) in Environmental Aqueous Samples

Table 4

Standard SPE procedures applied to reversed phases (Procedure 1) and cation-exchange phases (Procedure 2).

Step	Procedure 1	Procedure 2
Conditioning	3 mL MeOH, 3 mL deionized water	3 mL MeOH, 3 mL deionized water pH 3 (adjusted by HCl solution)
Sample loading	250 mL water; (not modified)	250 mL water, pH 3.0; (adjusted by HCl)
Flushing	3 mL deionized water	3 mL 5 % formic acid in water, 3 mL MeOH
Drying	20 min	—
Eluting	5 mL MeOH	3 mL 5 % ammonium hydroxide in MeOH