Lin Sf

Rapid analysis of melamine in infant formula by sweeping-micellar electrokinetic chromatography

In the present study, an analytical method using capillary electrophoresis with on-line preconcentration technique was developed for rapid determination of melamine in infant formula. Both stacking and sweeping preconcentration techniques had been investigated for the comparison of their effectiveness in melamine analysis. The limit of detection of melamine standard was 0.5 ng/mL for the field amplified sample stacking (FASS) technique and 9.2 ng/mL for the sweeping technique. Although the FASS technique provided better concentration efficacy than the sweeping technique, the matrix effect was more profound with the former. Matrix effect was evaluated by comparing the enhancement factor (EF) of melamine standard and post-extraction spiked infant formula solution. The EF was changed from 429.86 +/- 9.81 to the level less than 133.31 with significant peak distortion in the FASS system, and it was remained unchanged in the sweeping system. Sweeping-micellar electrokinetic chromatography (sweeping-MEKC) was demonstrated to be most suitable for real sample analysis. Under optimum sweeping-MEKC conditions, melamine content in infant formulas could be determined within 6 min. The developed solid phase extraction (SPE) procedures coupled with the sweeping-MEKC method was subjected to method validation. Run-to-run repeatability (n = 3) and day-to-day reproducibility (n = 3) of peak area were within 3.6% and 4.8% RSD, respectively. The accuracy was tested by spiking 0.5 and 2 microg/mL of melamine standard in the melamine contaminated milk powder provided by the European Commission, and the recoveries were 93.4 +/- 0.5% and 98.7 +/- 0.4%, respectively. Results of this study show a great potential for the sweeping-MEKC method as a tool for the fast screening of melamine in infant formulas.

Rapid determination of aristolochic acids I and II in herbal products and biological samples by ultra-high-pressure liquid chromatography-tandem mass spectrometry

Aristolochic acids (AAs) are a mixture of structural-related compounds, in which aristolochic acid I (AA I) and aristolochic acid II (AA II) are reported to be correlated with Aristolochic acid nephropathy (AAN). In this work, a rapid and sensitive ultra-high-pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed to determine AA I and AA II in herbal products and biological fluids. By using gradient elution with a mobile phase composed of a mixture of 10mM ammonium formate buffer (pH 3.0) and acetonitrile, AAs could be determined within 10 min. Under optimum UHPLC-MS/MS conditions, the limit of detections was 0.14 and 0.26 ng mL(-1) for AA I and AA II, respectively. Run-to-run repeatability and intermediate precision of peak area for AA I and AA II were less than 5.74% relative standard deviation (RSD). Accuracy was tested by spiking 10, 100 and 1000 ng mL(-1) in rat serum and the recoveries were within 76.5-92.9%. Matrix effects were within 78.8-127.7%. The developed method was successfully applied to determine AA I and AA II in several herbal products and to investigate their pharmacokinetic behavior in female Wister rats. The result shows that the developed UHPLC-MS/MS method is efficient, sensitive, and accurate for the determination of AA I and AA II in herbal products and biological samples.

Using sweeping-micellar electrokinetic chromatography to determine voriconazole in patient plasma

Invasive fungal infection is a life-threatening condition; its occurrence has increased significantly over the past 20 years. We have developed a sensitive and efficient sweeping-micellar electrokinetic chromatography (sweeping-MEKC) method to quantify voriconazole, a potent triazole antifungal drug, in patient plasma. Solid phase extraction (SPE) conditions were first optimized to minimize plasma interference while maintaining a high recovery; the sweeping-MEKC conditions were then systematically optimized to obtain a high sweeping efficiency with good selectivity. Under the optimal analytical conditions, voriconazole was baseline-separated from endogenous materials within 10.5 min with a limit of detection of 0.075 microg mL(-1). The background electrolyte comprised 40 mM phosphoric acid, 110 mM sodium dodecyl sulfate, and 20% acetonitrile. In terms of method repeatability, the relative standard deviations (RSDs) of the migration time and the peak area (intra-day; n=6) were both less than 5.5%; in terms of intermediate precision, and the RSDs of the peak area and the migration time (inter-day; n=3) were both less than 6.3%. We successfully applied this developed method to the quantitative determination of plasma voriconazole levels in 16 patients; the results correlated well with those obtained through analyses using high-performance liquid chromatography. This sweeping-MEKC method is accurate and efficient and appears to be applicable to therapeutic drug monitoring and clinical research.