Solid-phase extraction, with online

Niederlander H.A.G. et al., 2006. High throughtput therapeutic drug monitoring of clozapine and metabolites in serum by online coupling of solid phase extraction with liquid chromatography-mass spectrometry. J Chromatogr B 834 98. 

Pruvost A. et al., 2000. Fully automated determination of eserine N-oxide in human plasma using online solid-phase extraction with liquid chromatography coupled with electrospray ionization tandem mass spectrometry. J Mass Spectrom 35 625. 

Wissiack R., Rosenberg E., and Grasserbauer M., 2000. Comparison of different sorbent materials for online solid-phase extraction with liquid chromatography-atmospheric pressure chemical ionization mass spectrometry of phenols. J Chromatogr B 896 159. 

Aguilar, C., Bomil, F., and Marce, R. M., Online and offline solid-phase extraction with styrene-divinylbenzene membrane extrachon disks for determining pesticides in water by reversed-phase liquid chromatography-diode array detection, J. Chromatogr. A, 754, 77-84, 1996. 

Figure 2 Instrument arrangement for online solid-phase extraction with column switching. Pa and Pb, pumps Ci, extraction column for the online SPE C2, analytical column Vi and V2, injection and switching valves position 1, switching valve is positioned for online SPE cleanup and preconcentration position 2, switching valve is positioned to transport sample to the analytical column.

A recent method [ 114] for the speciation of organotin compounds in seawater combines solid-phase extraction, online HG, and GC with MIAE. This method enjoys a 0.5 pg detection limit for tin. 

In our laboratories, a cycle time of 90 sec can be achieved with a dilution factor of 1 25 for a given sample concentration, allowing the purity and identity control of two and a half 384-well microtiter plates per day. The online dilution eliminated an external step in the workflow and reduced the risks of decomposition of samples in the solvent mixture (weakly acidic aqueous solvent) required for analysis. Mao et al.23 described an example in which parallel sample preparation reduced steps in the workflow. They described a 2-min cycle time for the analysis of nefazodone and its metabolites for pharmacokinetic studies. The cycle time included complete solid phase extraction of neat samples, chromatographic separation, and LC/MS/MS analysis. The method was fully validated and proved rugged for high-throughput analysis of more than 5000 human plasma samples. Many papers published about this topic describe different methods of sample preparation. Hyotylainen24 has written a recent review. 

Typical instrument set-ups for online sample preparation, for example, solid phase extraction and sample pre-concentration, require the control of a six-port valve with an additional special column and a second pump. Ideally, this system will be fully controlled by the data acquisition software (Figure 3.12 (A)). 

Solid phase extraction (SPE) is fast and can work as a clean-up method when combined with capillary electrophoresis or used prior to HPLC/MS.34-37 Kerns et al.35 described an online alternating parallel SPE column with MS/MS detection and a turn-around time of 1.1 min. 

Bourgogne E., Grivet C., and Hopfgartner G., 2005. Determination of talinolol in human plasma using automated online solid phase extraction combined with atmospheric pressure chemical ionization tandem mass spectrometry. J Chromatogr B 820 103. 

Chao M. et al., 2005. Rapid and sensitive quantification of urinary N7-mthelguanine by isotope-dilution liquid chromatography/electrospray ionization tandem mass spectrometry with online solid-phase extraction. Rapid Commun Mass Spectrom 19 2427. 

Gon9alves J.C.S. et al., 2005. Online solid-phase extraction coupled with high-performance liquid chromatography and tandem mass spectrometry (SPE HPLC-MS-MS) for quantification of bromazepam in human plasma. Ther Drug Monit 27 601. 

Hogenboom A.C., Niessen W.M.A., and Brinkman U.A., 1999a. Online solid-phase extraction-short-column liquid chromatography combined with various tandem mass spectrometric scanning strategies for the rapid study of transformation of pesticides in surface water. J Chromatogr A 841 33. 

Marchese A. et al., 1998. Determination of pranlukast and its metabolites in human plasma by LC/MS/MS with Prospekt online solid-phase extraction. J Mass Spectrom 33 1071. 

Raices R.S.L. et al., 2003. Determination of stavudine in human serum by online solid-phase extraction coupled to high-performance liquid chromatography with electrospray ionization tandem mass spectrometry Application to a bioequivalence study. Rapid Commun Mass Spectrom 17 1611. 

Microdialysis to monitor the chemistry of extracellular space in human tissue is a challenging technique that has been applied in the neurosciences to measure neurochemical composition in vivo.104 Microdialysis coupled online with in-tube solid phase extraction (SPE) and ICP-MS has been developed by Sun et al.105 for the in vivo determination of several trace metals in order to study the transfer kinetics of trace elements in brain extracellular fluid. 

China) after digestion with aqua regia and using flow injection online solid phase extraction ICP-MS in order to minimize the isobaric interferences is discussed by Fang et al6i... 

In a method proposed by Booth et al. (141) for the determination of phylloquinone in various food types, extracted samples are subjected to silica solid-phase extraction followed, in the case of meat or milk samples, by further purification using reversed-phase solid-phase extraction or liquid-phase reduction extraction, respectively. The final test solution is analyzed by NARP-HPLC, and the fluorescent hydroquinone reduction products of phylloquinone and the internal standard are produced online using a postcolumn chemical reactor packed with zinc metal. 2, 3 -Dihydrophylloquinone, a synthetic analog of phylloquinone, is a suitable internal standard for the analysis of vegetable juice, whole milk, and spinach. Another synthetic analog, Ku23), is used for the analysis of bread and beef, because a contaminant in the test solution coelutes with dihydro-phylloquinone. 

Solid-phase extraction could be coupled online with HPLC. This is becoming increasingly important, because it makes it possible to handle all the situations in which large series of samples have to be analyzed routinely, and therefore rapid, (semi-) automatic, and unattended analysis is an aspect of major concern. Moreover, sensitive trace level determination requires the analysis of total samples or sample extracts rather than aliquots, under conditions in which analyte losses, due to evaporation or irreversible sorption to the vessels walls, and contamination, caused by the solvent or reagents used, laboratory air, and/or sample manipulation in general, must be rigorously minimized (45,46). 

S. Emara, H. Askal and T. Masujima, Rapid determination of methotrexate in plasma by high-performance liquid chromatography with online solid-phase extraction and automated precolumn derivatization , Biomed. Chromatogr. 12 338-342 (1998). 

Tollback, J., Tamburro, D., Crescenzi, C. and Carlsson, H. (2006) Air sampling with Empore solid phase extraction membranes and online single-channel desorption/ liquid chromatography/mass spectrometry analysis determination of volatile and semi-volatile organophosphate esters. Journal of Chromatography A, 1129,1-8. 

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