title: Optimization via experimental design of an SPE-HPLC-UV-fluorescence method for the determination of valsartan and its metabolite in human plasma samples.
abstract: A chemometric approach was applied for the optimization of the extraction and separation of the antihypertensive drug valsartan and its metabolite valeryl-4-hydroxy-valsartan from human plasma samples. Due to the high number of experimental and response variables to be studied, fractional factorial design (FFD) and central composite design (CCD) were used to optimize the HPLC-UV-fluorescence method. First, the significant variables were chosen with the help of FFD; then, a CCD was run to obtain the optimal values for the significant variables. The measured responses were the corrected areas of the two analytes and the resolution between the chromatographic peaks. Separation of valsartan, its metabolite valeryl-4-hydroxy-valsartan and candesartan M1, used as internal standard, was made using an Atlantis dC18 100 mm x 3.9 mm id, 100 angstroms, 3 microm chromatographic column. The mobile phase was run in gradient elution mode and consisted of ACN with 0.025% TFA and a 5 mM phosphate buffer with 0.025% TFA at pH 2.5. The initial percentage of ACN was 32% with a stepness of 4.5%/min to reach the 50%. A flow rate of 1.30 mL/min was applied throughout the chromatographic run, and the column temperature was kept to 40+/-0.2 degrees C. In the SPE procedure, experimental design was also used in order at achieve a maximum recovery percentage and extracts free from plasma interferences. The extraction procedure for spiked human plasma samples was carried out using C8 cartridges, phosphate buffer (pH 2, 60 mM) as conditioning agent, a washing step with methanol-phosphate buffer (40:60 v/v), a drying step of 8 min, and diethyl ether as eluent. The SPE-HPLC-UV-fluorescence method developed allowed the separation and quantitation of valsartan and its metabolite from human plasma samples with an adequate resolution and a total analysis time of 1 h.
authors.affiliation: Kimika Analitikoaren Saila, Zientzia eta Teknologia Fakultatea, Euskal Herriko Unibertsitatea/UPV, Bilbo, Basque Country, Spain.
authors.forename: Gorka
authors.initials: G
authors.lastname: Iriarte
authors.forename: Nerea
authors.initials: N
authors.lastname: Ferreirós
authors.forename: Izaskun
authors.initials: I
authors.lastname: Ibarrondo
authors.forename: Rosa Maria
authors.initials: RM
authors.lastname: Alonso
authors.forename: Miren Itxaso
authors.initials: MI
authors.lastname: Maguregi
authors.forename: Lorena
authors.initials: L
authors.lastname: Gonzalez
authors.forename: Rosa Maria
authors.initials: RM
authors.lastname: Jiménez
mesh_terms: D047228:Angiotensin II Type 1 Receptor Blockers / Q000097:blood; D000959:Antihypertensive Agents / Q000097:blood; D001774:Blood Chemical Analysis / Q000379:methods; D002851:Chromatography, High Pressure Liquid / Q000379:methods* / Q000706:statistics & numerical data; D006801:Humans; D052616:Solid Phase Extraction / Q000379:methods; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013777:Tetrazoles / Q000097:blood*; D014633:Valine / Q000031:analogs & derivatives* / Q000097:blood; D000068756:Valsartan
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D000959:Antihypertensive Agents; C494196:N-(1-oxo-4-hydroxypentyl)-N-((2'-(1H-tetrazol-5-yl)(1,1'-biphenyl)-4-yl)methyl)-L-valine; D013777:Tetrazoles; D000068756:Valsartan; D014633:Valine