PubMed · 14578510
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Davide Ricci, Pier Carlo Braga. 2004. Imaging methods in atomic force microscopy.. https://doi.org/10.1385/1-59259-647-9%3A13
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An analytical method for simultaneous determination of erythromycin propionate and its active metabolite, erythromycin base, in human plasma by high-performance liquid chromatography-electrospray mass spectrometry (HPLC-ESI-MS) was developed and validated. Roxithromycin was selected as the internal standard. The samples were directly injected after simple deproteinized procedure only. The separation was achieved on a Johnson Spherigel analytical column packed with 5 microm C18 silica, employing acetonitrile -0.1% formic acid aqueous solution (50:50) as mobile phase. The quantification of target compounds was obtained by using a selected ion monitoring (SIM) at m/z 790.7 for erythromycin propionate, m/z 734.7 for erythromycin base and m/z 837.8 for roxithromycin. The correlation coefficients of the calibration curves were better than 0.997 (n=6), in the ranges from 2 ng/ml to 1 microg/ml, and from 1 to 10 microg/ml for erythromycin propionate and base. The method can provide the necessary sensitivity, precision and accuracy to allow the simultaneous determination of both compounds in a patient's plasma following a single administration of erythromycin stinoprate capsule (500 mg erythromycin base equivalent).
Roscovitine, a purine analogue that selectively inhibits cyclin-dependent kinases, has been considered as a potential anti-tumor drug. The determination of roscovitine in plasma and urine was performed using microextraction in packed syringe as on-line sample preparation method with liquid chromatography and tandem mass spectrometry. The sampling sorbent utilized was polystyrene polymer. 2H3-lidocaine was used as internal standard. The limit of detection for roscovitine was as low as 0.5 ng/mL and the lower limit of quantification was 1.0 ng/mL. The accuracy and precision values of quality control samples were between +/-15% and < or =11%, respectively. The calibration curve was obtained within the concentration range 0.5-2000 ng/mL in both plasma and urine. The regression correlation coefficients for plasma and urine samples were > or =0.999 for all runs. The present method is miniaturized and fully automated and can be used for pharmacokinetic and pharmacodynamic studies.
The increasing scientific interest in nitric oxide (NO) necessitates the development of novel and simple methods of synthesising NO on a laboratory scale. In this study we have refined and developed a method of NO synthesis, using the neutral Griess reagent, which is inexpensive, simple to perform, and provides a reliable method of generating NO gas for in-vivo sensor calibration. The concentration of the generated NO stock solution was determined using UV-visible spectroscopy to be 0.28+/-0.01 mmol L(-1). The level of NO(2) (-) contaminant, also determined using spectroscopy, was found to be 0.67+/-0.21 mmol L(-1). However, this is not sufficient to cause any considerable increase in oxidation current when the NO stock solution is used for electrochemical sensor calibration over physiologically relevant concentrations; the NO sensitivity of bare Pt-disk electrodes operating at +900 mV (vs. SCE) was 1.08 nA micromol(-1) L, while that for NO(2) (-) was 5.9 x 10(-3) nA micromol(-1) L. The stability of the NO stock solution was also monitored for up to 2 h after synthesis and 30 min was found to be the time limit within which calibrations should be performed.