Validation of an analytical methodology to quantify melamine in body fluids using micellar liquid chromatography.

Measurement of urine and plasma melamine-concentration is helpful in confirming melamine-associated renal diseases. A chromatographic procedure using a C18 column and a micellar mobile phase of sodium dodecyl sulphate (0.2M), buffered at pH 3 and detection set at 210 nm, was reported for the resolution and quantification of melamine in plasma and urine. In this work, direct injection was used, thus avoiding long extraction and experimental procedures. Melamine was eluted in nearly 6.3 min without overlapping the protein band or other endogenous compounds. The optimal mobile phase composition was taken by studying the influence of each chromatographic parameter. Validation was satisfactorily performed following the US Food and Drug Administration (FDA), in terms of: linearity (0.25-25 ppm; r2>0.9995 in both cases), sensitivity, limit of detection (50 ppb), limit of quantification (250 ppb), intra- and inter-day precision (R.S.D. 0.7-10.2% and 1.0-9.1%, respectively) and recovery, calculated as accuracy (85.7-103.8% and 94.8-103.6%, respectively) and robustness (R.S.D.<7.1%). The suggested methodology has been applied to the analysis of real samples of volunteers, and no melamine was found in any of them.

Analytical determination of hydroxytyrosol in olive extract samples by micellar liquid chromatography.

Hydroxytyrosol is a well-known natural phenolic component obtained from olive extract samples with antioxidant effects. A micellar liquid chromatography method to detect and quantify hydroxytyrosol in olive extract samples is described. Matrix resolution was performed using a Kromasil C18 column and a micellar mobile phase of sodium dodecyl sulphate (SDS) 0.05M and 4% methanol buffered at pH 7. Detection was set by absorbance at 280nm. Samples were diluted with 0.05M SDS at pH 3 and directly injected, thus avoiding long tedious extractions. Hydroxytyrosol was eluted in 3.5min without overlapping other matrix compounds. Validation was performed following the US FDA guideline. The main analytical parameters studied were: linearity (0.03-250µgmL-1; r2=0.999), limit of detection and quantification (3 and 30ngmL-1, respectively), intra- and inter-day precision (RSD, % <1.4 and <8.2, respectively), and robustness (RSD, %<6.6). Recoveries were in the 88.5-98.9% range.