MISPE extraction

A recent review by Pichon and Haupt169 summarizes the progress in the area of utilization of MIPs for sample preparation purposes and cites several examples of solid phase extraction (MISPE) from biological matrices. The requirements and applications of MIPs are reviewed in a recent book170 and other literature.171-176... 

Solid-Phase Extraction with MIPs (MISPE). 276... 

It is interesting to mention that occasionally one may use batch MIP extraction instead of the MISPE, i.e., instead of the column or cartridge format, even with real samples [40]. 

An alternative and relatively simple approach to the same analytical problem is to carry out the large volume sample extraction with a commercial SPE disk, e.g., Cl8 disk, and then elute the analyte from the Cl8 disk with a smaller volume of suitably selected solvent onto an MISPE column [39]. 

Fig. 3 Chromatograms obtained in the analysis of a soil sample extract spiked with 0.1 pg g 1 of the selected fluoroquinolones (a) with and (b) without performing MISPE. Peak assignment 1 = enoxacin (ENO), 2 = norfloxacin (NOR), 3 = ciprofloxacin (CIP), 4 = danofloxacin (DAN), 5 = enrofloxacin (ENR) [43]...

Caro et al. made a noncovalent and a semicovalent MIP, respectively, for 4-nitrophenol (4-NP). Their purpose was to extract selectively 4-NP from river water in the presence of ten other phenolic pollutants. The MIPs were used in an online MISPE procedure employing dichloromethane as wash solvent. Figure 4 (Fig. 1 of the original) shows the experimental setup. The pump on the left is used to deliver the conditioning solutions, the sample, and the wash solvent. The two pumps on the right deliver the organic and the aqueous components of the HPLC... 

This paper shows a nice example for solving an important analytical problem using MISPE. Mycotoxins and particularly zearalenone (ZON) and /nmv-a-zearalenol (a-ZOL) present an everyday problem in food analysis. Existing sample clean-up techniques have different drawbacks. Liquid-liquid extraction is characterized by... 

The MISPE method of the authors uses a pressurized liquid extraction (also called accelerated solvent extraction) extract of the samples. This acetonitrile-methanol extract had to be dried and redissolved in acetonitrile because methanol was not compatible with the MISPE. The redissolution volume had to be relatively large (5 mL) due to solubility problems. The samples were loaded on the MIP, washed with 1 mL of water, and eluted with 3x1 mL of methanol/phosphoric acid (95 5 v/v) solution. The eluate was evaporated to dryness and redissolved in 1 mL of methanol. Final analysis was carried out by HPLC using fluorescence detection. 

Anderson RA et al (2008) Comparison of molecularly imprinted solid-phase extraction (MISPE) with classical solid-phase extraction (SPE) for the detection of benzodiazepines in post-mortem hair samples. Forensic Sci Int 174(1) 40 16... 

The first MISPE protocol reported in the literature [18] involved the use of an imprinted dispersion polymer in a column format, for the selective enrichment of pentamidine (1) in urine. In this case the high selectivity of the polymer allowed the analyte to be detected directly in the eluate without the need for any further chromatographic separation (entry A in Tables 15.1 and 15.2). In view of the high selectivity of MIPs, this is a viable approach that brings the benefits of shorter analysis times and simpler instrumentation. In most cases, however, MISPE has been used prior to a chromatographic separation step. The MIP has been applied in a batch-wise extraction [23] or in columns or cartridges [20-22,24-26,33]. 

The use of MISPE for the clean-up of beef liver extracts before quantification of atrazine (5) by HPLC-UV or ELISA was evaluated by Muldoon and Stanker (entry E in Tables 15.1 and 15.2) [24]. In both cases the application of MISPE resulted in improvements in analyte quantification. In particular for the HPLC method the use of MISPE improved the accuracy and precision and lowered the limit of detection. In the case of ELISA a better accuracy was achieved in the determination although the precision was similar. With the analyte present at ppb levels, the reliability of either determination method would have been marginal without the MISPE step. 

Fig. 15.8. Adsorption and elution of 100 pL of a placebo chewing gum extract spiked with nicotine (0.5 mg/mL) and /S-nicotyrine, cotinine and myosmine (0.05 mg/mL). The step elution was as follows MeCN 0-8 min, MeCN + 0.2 % TFA + 2.5% H2O 8-12 min, MeCN 12-15 min. The peak identity was established by separate injections and spectral analysis using a diode array detector. Rest refers to still not eluted -nicotyrine, cotinine and myosmine. In MISPE, only -nicotyrine could be detected in the adsorption and wash steps.

MISPE Molecularly imprinted solid phase extraction... 

The application of MIPs as the stationary phase in solid-phase extraction (SPE), often referred to as molecularly imprinted polymer solid-phase extraction (MIS P E), is a rapidly growing area [197-199]. With MISPE, highly specific enrichment of substances present at trace levels is possible. The technique has been applied to the analysis of drugs, for example, caffeine [200], scopolamine [201], naproxen [202], tetracycline [203], cholesterol [204] and local anesthetics [205], as well as environmental pollutants, exemplified by organophosphate flame retardants [206-208], triazines in soil and vegetable samples [71] and naphthalene sulfonates in river water [209]. 

Nicotine MISPE from in cigarette smoke extracts Haginaka et al., 2006... 

Molecularly imprinted solid-phase extraction (MISPE) is widely used for selective extraction of pharmaceuticals in variety of matrices (Rao et al, 2011 Javanbakht et al, 2010). The potential value of MISPE lies in the ability to selectively isolate specific compounds or their structural analogues from a complex matrix. The application of MIPs as sorbents allows not only preconcentration and cleaning of the sample but also selective extraction of the target analyte, which is important, particularly when the sample is complex and impurities can interfere with the quantification. 

MIPs were used as sorbent material in MISPE for metoclopramlde [MCP] in biological fluids [Javanbakht et al., 2009]. The binding capability and selectivity study of the MIPs revealed the high affinity of MIP for MCP in the aqueous environment. The optimized MISPE procedure was used to selectively extract the MCP from human serum and urine with an extraction recovery of more than 90%. The MISPE procedure resulted in efficient cleanup of trace amounts of MCP from serum and urine and the limits of detection of MCP in human serum and urine were 3 and 1.2 pgL, respectively. 

A molecularly imprinted column for liquid chromatography can be used not only to separate analytes, but also to selectively extract analytes from complex samples. This technique is called on-line Molecularly Imprinted Solid Phase Extraction (on-line MISPE), and it combines the high extraction efficiency of reverse phase SPE for aqueous samples with the high selectivity of the molecular-imprinted polymers. Examples of successful selective extraction and clean-up are reported in Figs. 9 and 10. 

In a different format, called pulsed MISPE (Fig. 11), the sample is preconcentrated on an MISPE column directly connected to the detector and the interfering substances are washed away. Then a small amount of solvent (20 pL), able to disrupt the interaction between the template and the stationary phase is used to quantitatively recover the retained analyte. This format has been applied successfully to the detection and quantification of theophylline [53] and 4-aminopyridine [54] in extracted serum, and nicotine in chewing gum [55] and tobacco [56]. 

XL PROTOCOL 3 ON-LINE MISPE OF THEOPHYLLINE IN COFFEE EXTRACTS... 

Figure 16 Extraction of theophylline from coffee extract using an on-column MISPE system.

Molecular imprinted polymer microspheres against enrofloxacin have been developed and off-line molecular imprinted solid-phase extraction (MISPE) has been applied for the extraction of enrofloxacin from bovine milk.t""i... 

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