Fiber-in-Tube Solid Phase Extraction (FIT-SPE) for Miniaturized Sample Preparation Process

A typical analytical separation procedure has several important steps: sample preparation, isolation, identification, quantitation, statistical evaluation and final decision. Each step is alwayscritical to obtain correct results to fulfill the analytical purpose. In these various steps sample     

High-performance liquid chromatographic assay for glucuronidation activity of 7-ethyl-10-hydroxycamptothecin (SN-38), the active metabolite of irinotecan (CPT-11), in human liver microsomes

A simple and sensitive assay for glucuronidation activity of 7-ethyl-10-hydroxycamptothecin (SN-38), the active metabolite of irinotecan (CPT-11), in human liver microsomes by high-performance liquid chromatography (HPLC) with fluorescence detection is reported. The method was validated for the determination of SN-38 glucuronide (SN-38G) with respect to specificity, linearity, recovery, stability, precision, accuracy, and limits of detection and quantitation. There was no interference from matrix and non-enzymatic reactions. The calibration curve for SN-38G was linear from 5 to 500 nM. Average recoveries ranged from 98 to 100% in spiked human liver microsome samples, and the SN-38G was stable at 4 degrees C for at least 72 h. The newly developed method was found to be more sensitive and selective than previous methods using thin layer chromatography and HPLC. The limit of quantitation for SN-38G was 5 nM (2.5 pmol/assay). The intra- and inter-day precision and accuracy were less than 7 and 4%, respectively. The intra- and inter-day precision of enzyme assay for UDP-glucuronosyltransferase (UGT) activity toward SN-38 in human liver microsomes was less than 4%. With this improved sensitivity, the kinetics of SN-38 glucuronidation in human liver microsomes could be determined more precisely. Therefore, this method is applicable to in vitro study on the side effects and drug interactions of CPT-11 using small amounts of biological sample.     

The correlation between molecular polarizability of PAHs and their retention data on various stationary phases in reversed-phase HPLC

Summary The equation for the potential energy of interactions established for gas-liquid chromatography has been confirmed in reversed phase liquid chromatography. Equations derived for molecular polarizabilities of PAHs and their retention data have very high correlation coefficients. The results indicate that the inductive effect between solute and stationary phase is the main one and the dispersive effect is very small compared with the inductive effect but its contribution increases with the carbon chain length of the stationary phase.     

Chromatographic performance of deuterated solvents in reversed phase micro high performance liquid chromatography

The chromatographic performance of the deuterated solvents, CD₃OD and D₂O, has been investigated in reversed-phase micro high performance liquid chromatography. The chromatographic performance of CD₃OD is only slightly superior to that of CH₃OH. However, the performance of D₂ is significantly superior to that of H₂O, separation of aromatics being improved by about 30%. D₂ is a particularly powerful solvent for the separation iof deuterated and non-deuterated compounds.     

Fullerenes separation with monomeric type C30 stationary phase in high-performance liquid chromatography

The temperature effect on the separation of fullerenes in LC was examined using monomeric type C30, C18 and C8 alkyl bonded stationary phases. It appears that the C30 phase exhibits superior separation ability for fullerenes. It is observed that the maximum retention temperature of fullerenes on the C30 phase is around 20 degrees C. A strong correlation between the changes in NMR spectra and the retention behavior of the solutes was found. The interpretation of the retention behavior of fullerenes on the alkyl bonded stationary phases, including the behavior in subambient temperature, is discussed using the information obtained by CP-MAS solid-state NMR spectroscopy and LC.     

Determination of 4-hydroxy-2-nonenal in primary rat hepatocyte cultures by liquid chromatography with laser induced fluorescence detection

An HPLC (high performance liquid chromatography) method with laser induced fluorescence (LIF) detection is described for the determination of 4-hydroxy-2-nonenal (HNE) formed from lipid peroxidation in rat hepatocytes. Carbonyl compounds were fluorescently labelled by incubating the hepatocyte samples with a tagging reagent, 4-(2-carbazoylpyrrolidin-1-yl)-7-nitro-2,1,3-benzoxadiazole (NBD-ProCZ), at 60 degrees C for 10 min. The hydrazone derivatives were extracted with a C18 solid phase extraction (SPE) cartridge and separated on a reversed-phase HPLC column. The detection limit was 2.5 fmol or 0.5 nM (5 microL injection) of HNE in the cell homogenate. Method precision (C.V.) was 5% at the 5 nM level. The method has been used to determine free HNE in rat hepatocyte samples treated with several pro-oxidant toxins. A significant HNE increase (from 4 to 27.6 pmol/10(6) cells) was observed with the samples treated by allyl alcohol. The results were in accordance with those for malondialdehyde formation as measured by a thiobarbituric acid (TBA) assay.     

Surface derivatization of poly(p-phenylene terephthalamide) fiber designed for novel separation and extraction media

The surface derivatization of poly(p-phenylene terephthalamide) fiber was studied. The obtained surface-derivatized filaments were packed into a fused-silica capillary to evaluate its surface characteristics by using GC. As the stationary phase for GC the surface-derivatized fibers showed higher retention for alkanes and alkylbenzenes than that with the untreated Kevlar fiber. The improvements on the retention power and the peak shape were observed on the benzyl-modified fibrous stationary phase. The derivatized fibrous materials were also evaluated as the extraction medium in fiber-in-tube SPE, and the effect of the surface modification on the extraction power was compared to the parent fiber. The results indicated that the modified fiber possessed a higher extraction power than the untreated fiber. Based on the facts, the successful modification of the fiber surface was estimated.     

Molecular-shape recognition of polycyclic aromatic hydrocarbons in reversed phase liquid chromatography

Summary The molecular-shape recognition of polycyclic aromatic hydrocarbons has been studied on various stationary phases in reversed-phase high-performance liquid chromatography. The examined stationary phases were phenyl-, diphenyl-, triphenyl- and benzyl-bonded silicas. The results of regression analysis inidcated that triphenylsilica is the best packing material to recognize the difference in the molecular-shape of structural isomers. This fact was confirmed by the separation of 4-ring isomers.     

Direct coupling of microcolumn liquid chromatography with in-tube solid-phase microextraction for the analysis of antidepressant drugs

The direct coupling of in-tube solid-phase microextraction (in-tube SPME) with microcolumn liquid chromatography (micro-LC) has been investigated for the analysis of antidepressants in human urine. The use of in-tube SPME has been clearly shown to be advantageous for the on-line coupling of the SPME method, as the sample pretreatment technique, with micro-LC as the separation technique. This is because much smaller amounts of the sample solutions, desorption solvents and the mobile phase are required compared with conventional SPME-LC systems. The parameters for preconcentration have been investigated for the extraction capillary with the newly developed 'wire-in-tube' configuration.