Plasma methionine determination by capillary electrophoresis-UV assay: application on patients affected by retinal venous occlusive disease.
Methionine is an important amino acid involved in protein synthesis and transmethylation reactions. It is also the precursor of homocysteine and cysteine, two important risk factors for cardiovascular diseases. As homocysteine research has gained impulsion, the evaluation of plasma methionine concentrations has acquired importance. Methionine measurement generally has been performed by HPLC after o-phthalaldehyde derivatization. Its separation from other amino acids is time-consuming. We set up a new specific capillary electrophoresis method in which analyte derivatization was avoided by sample concentration before analysis. Methionine was detected by UV absorbance at 204 nm with a detection limit of 0.5 micromol/L. By a capillary with an effective length of 50 cm filled with 125 mmol/L Tris phosphate buffer at pH 2.3, the separation occurred in less than 14 min. Precision tests indicated a good test repeatability for both migration times (coefficient of variation [CV]<0.3%) and areas (CV<2.0%). Moreover, a good reproducibility of intraassay and interassay tests was obtained (CV<2.9% and CV<3.5%, respectively). The Passing-Bablok regression and the Bland-Altman test for methods comparison suggest that the data obtained by our method and by a reference HPLC assay are similar. Assay performance was evaluated measuring methionine concentrations in retinal venous occlusive disease.
Zinellu
Angelo
A
Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy. angelozinellu@libero.it
Sotgia
Salvatore
S
Usai
Maria Franca
MF
Zinellu
Elisabetta
E
Posadino
Anna Maria
AM
Gaspa
Leonardo
L
Chessa
Roberto
R
Pinna
Antonio
A
Carta
Francesco
F
Deiana
Luca
L
Carru
Ciriaco
C
D000368:Aged; D001681:Biological Assay; D016022:Case-Control Studies; D015331:Cohort Studies; D019075:Electrophoresis, Capillary / Q000379:methods* / Q000592:standards; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008715:Methionine / Q000097:blood*; D008875:Middle Aged; D012169:Retinal Vein / Q000378:metabolism; D012170:Retinal Vein Occlusion / Q000097:blood* / Q000473:pathology; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature
D008715:Methionine