An isocratic HPLC charged aerosol detector (CAD) method was developed, validated, and applied for the determination of individual bile acids in human gastric and duodenal aspirates. The method requires a low volume of aspirates (50-100 ml) and minimal sample pretreatment. A Hypersil BDS RP-C 18 column (250 3 4.6 mm, 5 mm particle size) was equilibrated with a mobile phase composed of methanol-[ammoniun formate 20 mM, formic acid 0.5%, triethylamine 0.2% (pH 3)] 67:33 v/v. Its flow rate was 1 ml/min. The elution times for taurocholate, glycocholate, taurochenodeoxycholate, ursodeoxycholate, glycochenodeoxycholate, cholate, and glycodeoxycholate were approximately 9.9, 16.2, 18.2, 21.3, 31.6, 34.5, and 38.5 min, respectively. Calibration curves in the mobile phase were constructed in the concentration range of 0.5-500 mM. Limits of detection and quantification were in the range of 0.07-0.60 mM and 0.20-1.80 mM, respectively. This method was applied first, in gastric aspirates collected in the fasted state, in which bile acid presence is minimal and, second, in duodenal aspirates collected in the fed state, in which a large number of potentially interfering compounds exists. Intra-day relative standard deviation in fasted gastric aspirates and in fed duodenal aspirates was less than 2.2% and 6.0%, respectively.-Vertzoni, M., H. Archontaki, and C. Reppas. Determination of intralumenal individual bile acids by HPLC with charged aerosol detection. J. Lipid Res. 2008Res. . 49: 2690Res. -2695

An isolated droplet generator (IDG) has been used as a novel solution sample introduction system for laser-induced breakdown spectroscopy (LIBS). The IDG converts liquid samples to equally-spaced, uniform-sized droplets. The droplets are introduced into the region where a high-powered Nd:YAG laser beam is focused. The resulting analyte emission is spectrally and temporally resolved. The dependence of analyte emission intensity on several parameters (droplet radius, droplet production frequency, etc.) is examined. A flow injection analysis (FIA) manifold has been used to introduce samples to the IDG for quantitative analysis. Performance characteristics of the FIA/IDG/LIBS method are given. Calibration curves linear over 3 orders of magnitude have been obtained for several elements. Detection limits for solutions with the FIA/IDG/ LIBS system are in the low ppm range.

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Cyclodextrins (CDs) are a well-known class of supermolecules that have been widely used to protect drugs against conjugation and metabolic inactivation as well as to enhance the aqueous solubility and hence to ameliorate the oral bioavailability of sparingly soluble drug molecules. The hepatoprotectant drug silibinin can be incorporated into CDs, and here we elucidate the interaction between the drug and the host at the molecular level. The complexation product of silibinin with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) is characterized by Differential Scanning Calorimetry, mass spectrometry, solid and liquid high-resolution NMR spectroscopy. The chemical shift changes using (13)C CP/MAS on the complexing of the guest with the host provided significant information on the molecular interactions, and they were in agreement with the 2D NOESY results. These results point out that in both solid and liquid forms, the drug is engulfed and interacts with HP-β-CD in identical manner. Molecular dynamics calculations have been performed to examine the thermodynamic characteristics associated with the silibinin-HP-β-CD interactions and to study the stability of the complex. To approximate the physiological conditions, the aqueous solubility and dissolution characteristics of the complex at pH states simulating those of the upper gastrointestinal tract have been applied. To evaluate the antiproliferative activity of silibinin-HP-β-CD complex comparatively to silibinin in MCF-7 human cancer cells, MTT assays have been performed.

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