Solid phase sample application

FIGURE 5.16 Template scheme (top view) for solid phase sample application (SPSA) and process of performance (cross section of steps a to e) 1 — base of the device, 2 — glass plate, 3 — adsorbent layer, 4 — sample, 5 — top of the device, 6 — plunger to compress. Step a Template placed onto the preparative plate Step b Marking by means of a thin needle Step c Scraped out channel on the preparative plate Step d Filling in of the prepared mixture of sample and deactivated adsorbent Step e Compression by means of a plunger. (From Botz, L., Nyiredy, Sz., and Sticher, O., J. Planar Chromatogr, 3, 10-14, 1990. With permission.)... 

Botz et al. (1990) and Nyiredy (1996) described a solid-phase sample application method and device that is useful for both capillary-and forced-flow PLC. The initial zone produced is homogeneous within the entire cross section of the preparative layer and has an extremely sharp edge leading to the chromatographic layer, with the advantage of in situ sample concentration and cleanup. 

Botz, L., Nyiredy, Sz., and Sticher, O. (1990). A new solid phase sample application method and device for preparative planar chromatography. J. Planar Chro-matogr.—Mod. TLC 3 10-14. 

Figure 5 Principle of solid phase sample application, (a) The preparative chromatoplate is put in the SPSA device, (b) a prorile is scratched out from the stationary phase, (c) removal of the sorbent from the channel, (d) the channel is filled with the prepared deactivated sorbent, (e) the solid phase sample is pressed to ensure optimal contact between the stationary phase of the plate and the applied sample. (1, lower part of the device 2, glass plate 3, stationary phase 4, adsorbed sample 5, upper part of the device 6, form to press solid sample.) (Reproduced from Ref. 42, with permission.)...

The solid phase sample application mode can easily be used for linear OPLC separations (42) the prepared plate is placed horizontally, without the cover plate, in the OPLC chamber, and the separation can be started with a relatively high mobile phase velocity (high inlet pressure). Note that when using OPLC, the channel has to be completely filled, otherwise part of the mobile phase can overflow onto the surface of the sample, which can distort the separation process. If the channel is filled completely, any possible lack of correct contact between the stationary phase and the sample containing the inert support has, due to the forced flow, no effect on the efficiency of the separation. 

P.D. McDonald and E.S.P. Bouvier, Solid Phase Extraction Applications Guide and Bibliography, A Resource for Sample Preparation Methods Development, Waters, Milford, MA... 

Lloret, S. M., Legua, C. M., and Ealco, P. C., Preconcentration and dansylation of aliphatic amines using Ci8 solid-phase packings. Application to the screening analysis in environmental water samples, J. Chromatogr., 978, 59-69, 2002. 

The present state of the art in direct solid sampling methods for gas chromatographic analysis of additives encapsulated in polymers is reviewed. Techniques considered are static and dynamic headspace methods, thermal desorption and solid phase microextraction. Applications for each method are discussed. 54 refs. 

In gas-solid extractions the sample is passed through a container packed with a solid adsorbent. One example of the application of gas-solid extraction is in the analysis of organic compounds for carbon and hydrogen. The sample is combusted in a flowing stream of O2, and the gaseous combustion products are passed through a series of solid-phase adsorbents that remove the CO2 and 1T20. 

A method which uses supercritical fluid/solid phase extraction/supercritical fluid chromatography (SE/SPE/SEC) has been developed for the analysis of trace constituents in complex matrices (67). By using this technique, extraction and clean-up are accomplished in one step using unmodified SC CO2. This step is monitored by a photodiode-array detector which allows fractionation. Eigure 10.14 shows a schematic representation of the SE/SPE/SEC set-up. This system allowed selective retention of the sample matrices while eluting and depositing the analytes of interest in the cryogenic trap. Application to the analysis of pesticides from lipid sample matrices have been reported. In this case, the lipids were completely separated from the pesticides. 

The first bioanalytical application of LC-GC was presented by Grob et al. (119). These authors proposed this coupled system for the determination of diethylstilbe-strol in urine as a replacement for GC-MS. After hydrolysis, clean-up by solid-phase extraction and derivatization by pentafluorobenzyl bromide, the extract was separated with normal-phase LC by using cyclohexane/1 % tetrahydrofuran (THE) at a flow-rate of 260 p.l/min as the mobile phase. The result of LC-UV analysis of a urine sample and GC with electron-capture detection (ECD) of the LC fraction are shown in Ligures 11.8(a) and (b), respectively. The practical detection limits varied between about 0.1 and 0.3 ppb, depending on the urine being analysed. By use of... 

Electropherograms of a urine sample (8 ml) spiked with non-steroidal anti-inflammatory drugs (10 p-g/ml each) after direct CE analysis (b) and at-line SPE-CE (c). Peak identification is as follows I, ibuprofen N, naproxen K, ketoprofen P, flurbiprofen. Reprinted from Journal of Chromatography, 6 719, J. R. Veraait et al., At-line solid-phase exti action for capillary electrophoresis application to negatively charged solutes, pp. 199-208, copyright 1998, with permission from Elsevier Science. 

Several extraction methods for water samples are applicable, such as solvent extraction, SPE using a cartridge and disk and solid-phase microextraction (SPME). 

Kennedy et al. developed a lasalocid immunoassay for application to residues in chicken meat and liver samples. The antibody was specific and did not cross-react with salinomycin, maduramicin, or monensin. Sample preparation consisted of homogenization in aqueous acetonitrile, removal of fat from an aliquot of the aqueous acetonitrile by hexane extraction, and evaporation of acetonitrile. The sample was then reconstituted with assay buffer. Liver required an additional solid phase extraction step. The LOQ was 0.02 xgkg for muscle and 0.15 agkg for liver. These workers were able to use the system to determine the half-life of lasalocid in the tissues. 

Solid-phase sorbents are also used in a technique known as matrix solid-phase dispersion (MSPD). MSPD is a patented process first reported in 1989 for conducting the simultaneous disruption and extraction of solid and semi-solid samples. The technique is rapid and requires low volumes (ca. 10 mL) of solvents. One problem that has hindered further progress in pesticide residues analysis is the high ratio of sorbent to sample, typically 0.5-2 g of sorbent per 0.5 g of sample. This limits the sample size and creates problems with representative sub-sampling. It permits complete fractionation of the sample matrix components and also the ability to elute selectively a single compound or class of compounds from the same sample. Excellent reviews of the practical and theoretical aspects of MSPD " and applications in food analysis were presented by Barker.Torres et reported the use of MSPD for the... 

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