Solid-phase extraction derivatizing

C. L. Hsu and R. R. Walters, Assay of the enantiomers of ibutilide and artilide using solid-phase extraction, derivatization and achhal-cliiral column-switcliing high-performance liquid cliromatography , J. Chromatogr. B 667 115-128 (1995). 

Analytes can be separated from complex matrices by sample preparation techniques that include liquid extraction, supercritical fluid extraction, and solid-phase extraction. Dilute ionic analytes can be preconcentrated by adsorption onto an ion-exchange resin. Nonionic analytes can be concentrated by solid-phase extraction. Derivatization transforms the analyte into a more easily detected or separated form. 

A.M. Idris, On-line coupling of solid-phase extraction, derivatization reaction and spectrophotometry by sequential injection analysis application to trifluoperazine assay in human urine, J. Pharmacol. Toxicol. Method 56 (2007) 330. 

Gerecke, A.C. et al.. Determination of phenylurea herbicides in natural waters at concentrations below 1 ng using solid-phase extraction, derivatization, and solid-phase microextraction-gas chromatography-mass spectrometry, /. Chromatogr. A, 930, 9, 2001. 

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... 

To determine secondary alkanesulfonates in sewage wastewaters, solid phase extraction (SPE) and a single-step procedure which combines elution and injection port derivatization for analysis with GC-MS were developed [36]. Again a tetrabutylammonium ion pair reagent was employed both to elute the secondary alkanesulfonates as their ion pairs from CI8-bonded silica disks and to derivatize sulfonate ion pairs under GC injection port conditions. Secondary alkanesulfonates were effectively recovered from samples of raw sewage (>92%) and from primary (>98%) and secondary (>85%) effluents. No... 

Milbemectin consists of two active ingredients, M.A3 and M.A4. Milbemectin is extracted from plant materials and soils with methanol-water (7 3, v/v). After centrifugation, the extracts obtained are diluted to volume with the extraction solvent in a volumetric flask. Aliquots of the extracts are transferred on to a previously conditioned Cl8 solid-phase extraction (SPE) column. Milbemectin is eluted with methanol after washing the column with aqueous methanol. The eluate is evaporated to dryness and the residual milbemectin is converted to fluorescent anhydride derivatives after treatment with trifluoroacetic anhydride in 0.5 M triethylamine in benzene solution. The anhydride derivatives of M.A3 and M.A4 possess fluorescent sensitivity. The derivatized samples are dissolved in methanol and injected into a high-performance liquid chromatography (HPLC) system equipped with a fluorescence detector for quantitative determination. 

Mallat, E. and Barcelo, D., Analysis and degradation study of glyphosate and of aminomethylphosphonic in natural waters by means of polymeric and ion-exchange solid-phase extraction columns followed by ion chromatography-post-column derivatization with fluorescence detection, /. Chromatogr A, 823, 129, 1998. 

The analytes are typically extracted from the biological matrix using solvent extraction or solid phase extraction (SPE). Most analytes require some form of chemical derivatization prior to analysis by GC-MS techniques, whereas with LC-MS-MS no further treatment of the extract is required. The extracts obtained from urine are relatively dirty because of the many endogenous compounds that are present. It is for this reason that the very selective techniques of GC-MS-MS, GC-HRMS, or LC-MS-MS are required to detect some of the prohibited substances that have low detection levels. 

Hernandez R, Falco P, Cabeza A. 1997. Liquid chromatographic analysis of amphetamine and related compounds in urine using solid-phase extraction and 3,5-dinitrobenzoyl chloride for derivatization. J Chromatogr Sci 35(4) 169-175. 

Molins-Legua C, Campinc-Falco P, Sevillano-Cabeza A, Ped-r6n-Pons M. 1999. Urine polyamines determination using dansyl chloride derivatization in solid-phase extraction cartridges and HPLC. Analyst 124 477-482. 

For reliable identification of a residue, detailed information about the molecular structure of the analyte is essential. The total information about the molecular structure of the analyte is the sum of the information derived from each individual analytical step of tire method. Frequently used selective analytical steps based on chromatography or immunoaffinity, provide more or less general indirect information. For example, solid-phase extraction (SPE) cleanup followed by liquid chromatography/ultraviolet detection (LC/UV) has been suggested for screening and quantification of ivermectin residues in liver, but presumptive positive samples can be confirmed by derivatizing an aliquot of the SPE eluate and reanalyzing the fluorescent derivative of ivermectin in an LC-fluorescence system (17). 

Detection in liquid chromatography is mostly performed by fluorescence and/or ultraviolet absorption. In a few instances, electrochemical detection has also been employed (357, 368). For compounds that exhibit inherent intense fluorescence such as albendazole and metabolites (319, 320, 338, 355), closantel (344), and thiabendazole and metabolites (378), fluorometric detection is the preferred detection mode since it allows higher sensitivity. Compounds that do not fluoresce such as eprinomectin, moxidectin, and ivermectin, are usually converted to fluorescent derivatives prior to their injection into the liquid chromatographic analytical column. The derivatization procedure commonly applied for this group of compounds includes reaction with trifluoroacetic anhydride in presence of A-methylimidazole as a base catalyst in acetonitrile (346, 347, 351, 352, 366, 369, 372-374). The formation of the fluorophore is achieved in 30 s at 25 C and results in a very stable derivative of ivermectin and moxidectin (353) but a relatively unstable derivative of eprinomectin (365). However, the derivatized extracts are not pure enough, so that their injection dramatically shortens the life of the liquid chromatographic column unless a silica solid-phase extraction cleanup is finally applied. 

In contrast to the solid-phase extraction approach, only nonpolar Cig derivatized silica has been used as the sorbent in matrix solid-phase dispersion technique. Tliis technique, which simplifies the overall methodology and removes most of die interfering compounds from animal-derived foods, has been successfully applied in the determination of nicarbazin residues in meat (66) and chicken tissues (412). 

Following extraction/cleanup, quinoxaline-2-carboxylic acid can be detected by electron capture, or mass spectrometric techniques, after gas chromatographic separation on capillary or conventional columns. A prerequisite of quin-oxaline-2-carboxylic acid analysis by gas chromatography is the derivatization of the molecule by means of esterification. Esterification has been accomplished with methanol (419, 420, 422), ethanol (421), or propanol (423) under sulfuric acid catalysis. Further purification of the alkyl ester derivative with solid-phase extraction on a silica gel column (422), thin-layer chromatography on silica gel plate (420), or liquid chromatography on Hypersil-ODS, 3 m, column (423), has been reported. 

Solid-phase extraction columns offer a rough cleanup of the crude extract, which might nevertheless not be sufficient for some detection systems such as mass spectrometry. Some authors have proposed a combination of solid-phase extraction and liquid chromatography columns for extract cleanup (440). Other methods appeal to liquid chromatography on Cig columns with automated fraction collection. Fractions containing the analyte of interest were evaporated to dryness, yielding a residue that in most cases was suitable for gas chromatographic detection after suitable derivatization (445, 437). 

Starting with a description of the analytical challenge in Chapter 19, the third part, which is devoted to analytical attitudes, proceeds with a detailed description in Chapter 20 of modern sample preparation procedures including solid-phase extraction, matrix solid-phase dispersion, use of restricted-access media, supercritical fluid extraction, and immunoaffinity cleanup. Flexible derivatization techniques including fluorescence, ultraviolet-visible, enzymatic, and photochemical derivatization procedures are presented in Chapter 21. 

P Edder, A Cominoli, C Corvi. Determination of streptomycin residues in food by solid-phase extraction and liquid chromatography with post-column derivatization and fluorimetric detection. J Chromatogr A 830 345-351, 1999. 

A method for the determination of 15 BAs in different foodstuffs, namely, Swiss cheese, salami, milk, beer, and wine, was developed by Petridis and Steinhart it is based on an automated precolumn derivatization of BAs [after acidification with TCA and solid-phase extraction (SPE) on Amberlite resin] with OPA/ME and separation on a Spherisorb ODS-2 column with gradient elution (ACN-MeOH-phosphate buffer) and fluorescence detection (71). 

The method commonly proposed is based on cation-exchange extraction followed by derivatization of the fraction of interest with OPA (46,55,98,99,114,124-126) (when isolating BAs in wines). Solid-phase extraction has been performed with several stationary phases based on anionic (113) or cationic (37,39) exchangers or octadecylsilane groups (38), as well as a combination of both (51). 

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). 

Field J. A., T.M. Field, T. Poiger, and W. Giger. 1994. Determination of secondary alkane sulfonates in sewage wastewaters by solid-phase extraction and injection-port derivatization gas chromatography/mass spectrometry. Environ. Sci. Technol. 28, 496-503. 

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