Hydrophilicity, solid-phase extraction

Heller D, Nochetto CB, Rumel NG, Thomas MH, Development of multi-class methods for drug residues in eggs hydrophilic solid-phase extraction clean-up and liquid chro-matography/tandem mass spectrometry analysis of tetracycline, fluoroquinolone, sulfonamide, and -lactam residues, J. Agric. Food Chem. 2006 54 5267-5278. 

Betalains are vacuolar plant pigments. Hence their hydrophilic nature is comprehensible. Although they are slightly soluble in ethanol and methanol, water is the best snited solvent both for stability and solnbility reasons. In contrast to the antho-cyanins, the betalains are even more polar as can be demonstrated by shorter retention times in RP-HPLC and lower solubilities in alcoholic solutions. The varying polarities may also be beneficially used to separate anthocyanins from betalains on an RP-18 solid-phase extraction cartridge (Stintzing, unpublished data). 

Recently, solid phase extraction (SPE) has been used to isolate members of this class of compounds. No solid phase support has been used exclusively and both hydrophobic- and hydrophilic-based solid phase extraction columns have been used for this assay. 

R. Loos, M.C. Alonso and D. Barcelo, Solid-phase extraction of polar hydrophilic aromatic sulfonates followed by capillary zone electrophoresis-UV absorbance detection and ion-pair liquid chromatography-diode array UV detection and electrospray mass spectrometry. J. Chromatogr.A 890 (2000) 225-237. 

Abu Ruz S, Millership J, Heaney L, McElnay J. 2003. Simple liquid chromatography method for the rapid simultaneous determination of prednisolone and cortisol in plasma and urine using hydrophilic lipophilic balanced solid phase extraction cartridges. J Chromatogr B Biomed Sci Appl 798(2) 193-201. 

Solid-phase extraction seems to be more suitable for multiresidue cleanup. This procedure has become the method of choice for isolation and/or cleanup of -lactam antibiotics from biological matrices, because it requires low solvent consumption, it is generally less time-consuming and labor-intensive, and offers a variety of alternative approaches that allow better extraction of the more hydrophilic -lactam antibiotics such as ampicillin. It is usually performed using reversed-phase Ci8 (69-71, 80-83, 90, 92-94, 99, 107, 112-116, 121-125) or Cg (103), anion-exchange (95, 124), and polar diol (95) or alumina (101, 113) sorbents. In recent applications, some workers demonstrated the potential of online solid-phase extraction in the determination of monobasic penicillins in bovine muscle tissues using a reversed-phase Cis 5 m cartridge and an automated... 

The selection of adsorbent packing material is based on the polarity of pollutants to be analyzed. The nonpolar hydrophobic adsorbents retain the nonpolar analytes and allow the polar substances to pass through the column. The hydrophilic adsorbents adsorb the polar components, allowing the nonpolar materials to pass through. Various stationary phases for solid phase extraction are listed below in Table 1.5.1. 

Notes LOD, limit of detection MeOH, methanol EtOH, ethanol ACN, acetonitrile EtAC, ethyl acetate SPE, solid phase extraction HLB (hydrophilic lipophilic balanced) TFA, trifluoroacetic acid GC, gas chromatography TMS, trimethylsilyl MS, mass spectrometry HPLC, high-performance liquid chromatography DAD, diode array detector NMR, nuclear magnetic resonance ESI, electrospray ionization APCI, atmospheric pressure chemical ionization CE, capillary electrophoresis ECD, electrochemical detector CD, conductivity detector TLC, thin layer chromatography PDA, photodiode array detector. 

Fontanals, N., Marce, R.M., Borrull, F. New hydrophilic materials for solid-phase extraction. Trends Anal. Chem. 24, 394-406 (2005)... 

Fiehn, O. and Jekel, M., Comparison of sorbents using semipolar to highly hydrophilic compounds for a sequential solid-phase extraction procedure of industrial wastewater. Anal. Chem., 68, 3083-3089, 1996. 

In contrast to penicillin, the hydrophilic cephalosporin is more suitable for solid-phase extraction. For high yield and purity extraction, a combination of several, different chromatographic steps is used. 

Eontanals N, Marcd RM, Borrull F. (2004). Solid-phase extraction of polar compounds with a hydrophilic copolymeric sorbent. Journal of Chromatography A 1030 63-68. 

Solid phase extraction (see Chapter 3) has been successfully used to extract Sudan dyes from spices using a surface-modified polymeric-based column that has hydrophilic, hydrophobic, or tt-tt retention mechanisms. This particular phase can be used to extract both polar and nonpolar compounds. An example of a Sudan red dye is given in Figure 11.7. 

The sample pretreatment used to determine procyanidins and their metabolites in plasma samples (from rats) is off-line solid-phase extraction (SPE) with hydrophilic-lipophilic balanced (HLB) copolymer. Both cartridges (60 mg) [31,32] and microelution SPE plates (pSPEs) (2 mg) [33,36,37] have been used as the device format. For the analysis of tissues (also from rats), such as the liver, brain, aorta artery, and adipose tissue, these were first freeze-dried and then pretreated by off-line Ll.F. (with the solution made up of methanol, water, and phosphoric acid) followed by pSPE [35-37]. The use of two sample pretreatments (LLE and pSPE) is due to the complexity of the tissue sample compared with the biofluid plasma sample. The extraction recoveries (%Rs) for determining the procyanidins catechin, epicatechin, dimer B2, and trimer in the plasma samples by pSPE [33] and SPE [31] were higher... 

Li, A.C., Junga, H., Shou,W.Z., et al. (2004) Direct injection of solid-phase extraction eluents onto silica columns for the analysis of polar compounds isoniazid and cetirizine in plasma using hydrophilic interaction chromatography with tandem mass spectrometry. Rapid Communications in Mass Spectrometry, 18, 2343-2350. 

Aspects of sample preparation have been reviewed. Phenols and aromatic amines, although amenable to EC oxidation detection, tend to be relatively water soluble and thus polar extraction solvents such as ethyl acetate may have to be used if liquid-liquid extraction (LLE) is to be employed. Solid-phase extraction (SPE), using disposable cartridges or plastic syringe barrels packed usually with chemically-modified silica materials (Table 4.2) analogous to those used in HPLC columns, but with greater porosity, provides an alternative and may be more effective in extracting relatively hydrophilic analytes. On-line sample preparation procedures such as prior to EC detection have also been described. 

Turrell E, Stobo L, Lacaze JP, Piletsky S, Piletska E (2008) Optimization of hydrophilic interaction liquid chromatography/mass spectrometry and developmtait of solid-phase extraction for the determination of paralytic shellfish poistming toxins. J AOAC Int 91 1372-1386... 

With liquid samples as oils, OL isolation has been realized by two main techniques liquid-liquid extraction (LLE) and solid-phase extraction (SPE) [14, 73]. LLE is based on transfer of the phenolic fraction from VOO to a more hydrophilic phase such as pure methanol or methanol-water mixtures with different alcohol concentrations [42 14]. Ultrasounds can be used as auxiliary energy to accelerate and improve LLE. The main advantages of ultrasound-assisted LLE are shortened extraction time, reduced reagent and sample volume, and improved extraction efficiency [32, 48]. After extraction, cleanup and pre-concentration steps are... 

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