Liquid chromatography derivatization

In liquid chromatography, derivatization for detection enhancement is frequently needed, since no universal, sensitive, and simple-to-operate detector exists (the preparation of UV-absorbing derivatives is essential to obtain the sensitivity required for samples in the nanogram range). Since most fatty acids do not absorb UV radiation (at least not in the wavelength ranges of most commercial UV monitors), detection of quantities in the 1-ng range can be difficult. Tag-... 

Frattini V, Lionetti C (1988) Histamine and histidine determination in tuna fish samples using high-performance liquid chromatography derivatization with o-phthalaldehyde and fluorescence detection or UV detection of free species. J Orromatogr A 809 241-245... 

Despite their importance, gas chromatography and liquid chromatography cannot be used to separate and analyze all types of samples. Gas chromatography, particularly when using capillary columns, provides for rapid separations with excellent resolution. Its application, however, is limited to volatile analytes or those analytes that can be made volatile by a suitable derivatization. Liquid chromatography can be used to separate a wider array of solutes however, the most commonly used detectors (UV, fluorescence, and electrochemical) do not respond as universally as the flame ionization detector commonly used in gas chromatography. 

Hydrazine in air Lab method using sampling either onto acid-coated glass-fibre filters followed by solvent desorption or into specially constructed impingers. Linal analysis by derivatization and high performance liquid chromatography 86... 

Liquid chromatography (LC) is a good alternative to GC for polar or thermolabile eompounds. While polar eompounds need to be derivatized for GC analysis, this is therefore not neeessary for LC analysis. 

Pfeffer, W. D. Yeung, E. S. Anal. Chem. 1986, 58, 2103. Lawrence, J. F. Frei, R. W. Chemical Derivatization in Liquid Chromatography, Elsevier Scientific New York, 1976. 

Detection-Qriented Derivatization Techniques in Liquid Chromatography, edited by Henk Lingeman... 

Several methods can be used for the residue analysis of anilides, especially gas chro-matography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS). GC/ECD or GC/NPD for the determination of anilides has generally been used except for the unstable metabolites of naproanilide and clomeprop, which are determined by HPLC/UV, HPLC/FL or GC/ECD after derivatization. 

More recently, liquid chromatography/mass spectrometry (LC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) have been evaluated as possible alternative methods for carfentrazone-ethyl compounds in crop matrices. The LC/MS methods allow the chemical derivatization step for the acid metabolites to be avoided, reducing the analysis time. These new methods provide excellent sensitivity and method recovery for carfentrazone-ethyl. However, the final sample extracts, after being cleaned up extensively using three SPE cartridges, still exhibited ionization suppression due to the matrix background for the acid metabolites. Acceptable method recoveries (70-120%) of carfentrazone-ethyl metabolites have not yet been obtained. 

Ethylenethiourea (ETU) is a toxic decomposition product/metabolite of alky-lenebis(dithiocarbamates). This compound could be generated during processing of treated crops at elevated temperature. Different chromatographic methods to determine the residue levels of ETU have been published. After extraction with methanol, clean-up on a Gas-Chrom S/alumina column and derivatization (alkylation) with bro-mobutane, ETU residues can be determined by GC with a flame photometric detector in the sulfur mode. Alternatively, ETU residues can also be determined by an HPLC method with UV detection at 240 nm or by liquid chromatography/mass spectrometry (LC/MS) or liquid chromatography/tandem mass spectrometry (LC/MS/MS) (molecular ion m/z 103). ... 

Several determination methods such as GC, HPLC, gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS) are used for the analysis of neonicotinoid residues. The applications of GC/MS and LC/MS are of increasing importance. The application of HPLC to the determination of neonicotinoids residues is limited, especially when metabolites (such as acetamiprid and nitenpyram) can be easily determined by GC after derivatization. 

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. 

Katayama, M., Masuda, Y., and Taniguchi, H., Determination of alcohols by high-performance liquid chromatography after pre-column derivatization with 2-(4-carboxyphenyl)-5,6-dimethylbenzimidazole,/. Chromatogr., 585,219, 1991. 

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