Extraction methods for the removal of phospholipids and other endogenous material from a biological fluid.

BACKGROUND: A comparison of three different sample preparation techniques for the analysis of plasma samples has been investigated to highlight the effect that these approaches have on the removal of endogenous material. The three techniques under investigation are: SPE, support assisted liquid-liquid extraction and nonspecific solvent-based protein precipitation. RESULTS: Comparisons are made on the practicalities of each approach and to allow a semiquantitative assessment between the effectiveness of these different techniques the relative amounts of phospholipids present within the sample are analyzed. Total ion chromatograms are also obtained to further study the effects of different extraction techniques in the removal of endogenous components from a biological matrix. Both of these approaches provide a very coarse measure of the cleanliness of the extracts and demonstrate that support assisted liquid-liquid extraction and an optimized SPE approach remove a greater amount of endogenous material. CONCLUSION: This study highlights the importance of sample preparation in removing endogenous material, which may have a detrimental effect on the performance of a bioanalytical assay.

Daptomycin determination by liquid chromatography-mass spectrometry in peritoneal fluid, blood plasma, and urine of clinical patients receiving peritoneal dialysis treatment.

A 13-min LC-MS method was developed for the determination of daptomycin, a new potent antibiotic, in peritoneal fluid, blood plasma, and urine of patients receiving renal replacement therapy. Chromatography was performed on a C(18) column and detection was performed by a single-quadrupole mass spectrometer coupled to LC via an electrospray interface (ESI). The column effluent was also monitored at 370 nm using a photodiode-array detector. The developed method provided a linear dynamic range for concentrations from 0.5 microg mL(-1) to 100 microg mL(-1). Method precision and accuracy were found to be satisfactory for clinical application, thus the method was successfully used for the analysis of daptomycin in pharmacokinetic studies. The drug was preventively administered against Gram-positive infections to 19 clinical patients undergoing peritoneal dialysis. Peritoneal fluid, blood plasma, and urine samples were collected at 13 time points over a period of 48 h. Clinical samples were analysed following simple sample-preparation procedures and daptomycin was unambiguously detected and quantified.