Solid phase extraction , sample pretreatment

Pankey et al.21 described a rapid, reliable, and specific enzyme multiplied immunoassay technique (EMIT ) for amitriptyline, nortriptyline, imipramine, and desipramine in sera. To overcome crossreactivity, solid phase extraction was included in sample pretreatment. Disposable 1 mL columns packed with covalently labeled silica gel were conditioned with HPLC-grade methanol (1 mL) and then with de-ionized or distilled water (1 mL). Serum (calibrator, control, or patient sample, 500 L) was applied onto the column, eluted to waste, washed with 900 /uL of wash solution containing acetonitrile (236.1 g/L) and ion-pairing reagent in acetate buffer, pH 4.2, washed with 500 fiL of mobile phase solution containing acetonitrile (393.5 g/L) in methanolic phosphate buffer, pH 7.0,... 

Lopez-Avila et al. [59] used microwave assisted extraction to assist the extraction of polyaromatic hydrocarbons from soils. Another extraction method was described by Hartmann [60] for the recovery of polyaromatic hydrocarbons in forest soils. The method included saponification of samples in an ultrasonic bath, partitioning of polyaromatic hydrocarbons into hexane, extract cleanup by using solid-phase extraction, and gas chromatography-mass spectrometric analysis using deuterated internal standards. Polyaromatic hydrocarbons were thermally desorbed from soils and sediments without pretreatment in another investigation [61]. 

The sample pretreatment steps for surfactant analysis such as extraction and concentration can be carried out in a variety of ways. Most of the common and well tested procedures have been described by Schmitt [46]. Solid phase extraction (SPE) with C2, Cg or Cis and divinyl benzene resins as well as special phases, e.g. graphitised carbon black (GCB), can be adequate methods, especially for SPE of metabolites from... 

Extraction efficiency. Recovery of the analyte from biological matrix after sample pretreatment (i.e., liquid-liquid extraction, solid-phase extraction, protein precipitation, etc.) to remove endogenous substances. 

For analyzing amphenicol residues in liquid samples such as milk, a pretreatment centrifugation step for fat removal is usually required (21, 22). Dilution of milk samples with water prior to solid-phase extraction cleanup is also often needed (23, 24). Semisolid samples such as muscle, kidney and liver, require, however, more intensive sample pretreatment. The most popular approach for tissue break-up is through use of a mincing and/or a homogenizing apparatus. 

Prior to analysis of -lactam residues in liquid foods such as milk, a pretreatment step for fat removal, accomplished by centrifugation (69-71), is usually required. In instances where milk is to be submitted to ultrafiltration, dilution with water/acetonitrile (72-76) or water/acetonitrile/methanol (77-79) is often needed. Milk filtration (80) or dilution with acetate (81, 82) or phosphate buffers (83) is sometimes essential prior to solid-phase extraction. Unlike milk, semisolid food samples such as muscle, kidney, and liver require normally more intensive sample pretreatment. Tissue break-up is mostly carried out by the combined use of a mincing apparatus and a tissue homogenizer. 

When analyzing milk samples for nitro furan residues, dilution with sodium chloride solution (155) or lyophilization (156) prior to extraction may be required. Dilution of egg samples with water prior to their solid-phase extraction has been also reported (157). Semisolid samples such as muscle, kidney, and liver, require a more intensive sample pretreatment. This involves use of a mincing apparatus followed by sample homogenization in water (37), sodium chloride solution (155), or dilute hydrochloric acid (158). 

When liquid samples such as serum, plasma, milk, or honey are not to be extracted using direct liquid-liquid partitions with organic solvents but through use of solid-phase extraction or matrix solid-phase dispersion techniques, dilution with water (323, 324), phosphate buffer saline (325), or phosphoric acid (326, 327) is often the only sample preparation procedure applied. Milk analysis sometimes requires further pretreatment for fat removal (328). Centrifugation at about 7000g at 4-10 C for 20 min is the usually applied procedure for making the fat floating on top of milk readily eliminated. 

In addition to solid-phase extraction and chemical vapour generation, other sample pretreatment procedures (including liquid-liquid extraction, precipitation, dialysis and even distillation) can be automated and coupled to the spectrometer. 

Fig. 19 Randomly scattered low internal standard (IS) responses observed for incurred samples only, whose IS responses were within normal range during repeat analyses. Analyte olanzapine IS olanzapine-d3 sample pretreatment at clinic 25 % (w/v) L-ascorbic add added to plasma in a ratio of 1.25 100 (v/v) extraction MCX (mixed-mode strong cation exchange)-based solid-phase extraction. An incurred sample was coded for reassay when its IS response was outside 50 % of the mean IS response of the accepted calibration standards and quality controls. Reproduced from ref. [36] with permission from Elsevier...

Ahrer et al. [69] developed methods for the determination of drug residues in water based on the combination of liquid chromatography (LC) or capillary electrophoresis (CE) with mass spectrometry (MS). A 2 mM ammonium acetate at pH 5.5 and a methanol gradient was used for the HPLC-MS allowing the separation of a number of drugs such as paracetamol, clofibric acid, penicillin V, naproxen, bezafibrate, carba-mazepin, diclofenac, ibuprofen, and mefenamic acid. Apart from the analytical separation technique, water samples have to be pretreated in order to get rid of the matrix components and to enrich the analytes the usual way to accomplish this aim is to perform a solid-phase extraction... 

Liquid-liquid extraction (LLE), solid phase extraction (SPE), and solid phase micro-extraction (SPME) are frequently applied for sample pretreatment. The type of extraction is highly related to the type of metabolites selected for determination. In previous metabolomics studies, extraction was focused on compounds of adequate stability that could be extracted together (carbohydrates, esters, amino acids, or organic acids). 

The analysis of target molecules in complex mixtures often requires pretreatment steps [5]. First, if the analyte is present in low concentration, it needs to be concentrated in order to be detected by standard analytical techniques. Secondly, if it is present in a complex mixture of similar compounds, a clean-up step is required. Solid phase extraction (SPE) has become a widely used technique for sample... 

After generation, the metabolites must be extracted and isolated. A variety of sample pretreatment methods can be applied, such as protein precipitation, liquid extraction, liquid-liquid extraction (LLE), solid-phase extraction (SPE), and microdialysis. Cleanup prior to LC-MS analysis is essential to reduce endogenous interferences and small peaks at every m/z in the mass spectra. The cleanup step also facilitates the data processing and peak detection in the chromatogram. 

Nevertheless, the authors observed that several molecular masses between 3-5 kDa were detected exclusively in the fat body tissue collected from bacteria-challenged larvae of this flesh-fly while others were only present in control flies [55]. Such approach evidenced the sensitivity and potency of MALDI-MS to perform peptide mass fingerprints directly on tissues or organs. Analyzing complex biological samples by MALDI-MS without any pretreatment of the sample e.g. solid-phase extraction, LC) has thus become a reality. 

Figure 11.3 Separation of potato tissue glycoalkaloids on an amino phase [reproduced with permission from K. Kobayashi, A.D. Powell, M. Toyoda and Y. Saito, J. Chromatogr, 331 (1989)]. Conditions sample, extract from young potato plantlets after solid-phase extraction pretreatment column, 30cm x 3.9mm i.d. stationary phase, [xBondapak NH2 mobile phase, ethanol-acetonitrile-potassium dihydrogenphosphate (3 2 1) UV detector, 205 nm. Peaks 1 = a-chaconine with Rq =/3-D-glucose, R2 — R3 —a-i-rhamnose 2 — a-solanine with Rl =/3-D-galactose, R2 = /3-D-glucose, R3 —a-L-rhamnose.

Khrolenko, M., Dzygiel, P., Wieczorek, P. (2002). Combination of supported hquid membrane and solid-phase extraction for sample pretreatment of triazine herbicides in juice prior to capiUary electrophoresis detennination. J. Chromatogr. A, 975, 219-27. 

Until recently, samples for FIA were already extracted. Altered, centrifuged or pretreated in some way prior to assay. However, some sample preparation and preconcentration steps can now be accommodated in FIA. Some examples are on-line liquid-liquid extraction, solid phase extraction and ion-exchange procedures. In this way, FIA is managing to convert some traditionally labour-intensive steps into automated operations that have higher precision and faster throughput. FIA can also tolerate other sample types, such as fermentation broth samples and even gases through the use of silicon membrane separators and gas diffusion systems, respectively. 

While LOV can have similar applications to LOG, it has found a particular niche in online sample pretreatment methods where the valve allows automation and miniaturisation of these traditionally labour intensive steps. Examples include solid phase extraction, ion exchange and solvent extraction. Compared to macrosample pretreatment, LOV offers the following advantages ... 

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