Detection after derivatization

The HPLC methods mainly use UV detectors, but one uses ampero-metric (18) and one uses fluorescent detection (25), Fluorescent detection after derivatization with fluorescamine is the method most commonly used for detection on TLC plates, Vilim (24) used TLC to... 

Lawrence JF, Iverson F. 1975. Analysis of the diazinon metabolites G 27550 and GS 31144 by gas liquid chromatography with nitrogen-specific detection after derivatization. J Chromatogr 103 341-347. 

A direct spectrometric method for screening nalidixic acid in chicken tissues (189, 190) has been reported. This method was based on fluorometric detection after derivatization of the analyte with sulfuric acid. The major drawback of this method is tliat it cannot differentiate among the various quinolones, it is less sensitive than the screening tests usually employed for regulatory purposes, and it is complicated by the necessity for derivatization. 

ELSD = evaporative light-scattering detector. b An alternative is detection after derivatization. 

J. M. Moore, A. C. Allen, and D. A. Cooper, Determination of manufacturing impurities in heroin by capillary gas chromatography with electron capture detection after derivatization with hep-tafluorobutyric anhydride, Anal. Chem., 56 642 (1984). 

The method consists of the complete hydrolysis of a protein or peptide to release its component amino acids. These may be separated by reverse phase high performance liquid chromatography (HPLC), and quantified with fluorometric detection after derivatization with o-phthaldehyde (Larsen and West, 1981). The method serves to determine both the amino acid composition and the total quantity of protein present in the sample. 

Thin layer chromatography (TLC) was used for quick comparison of the various samples (Silicagel-GF254, toluene-ethylacetate (93 7), hexane-ethylacetate (95 5), dichloromethane-ethylacetate-acetone (95 3 2), chloroform-methanol (90 10), UV (365 nm) and normal light detection after derivatization). 

Determination of oxidized amino acids in urine is usually performed by isotope dilution gas chromatography-mass spectrometry (L9). DOPA is estimated by HPLC separation of acid protein hydrolysates with fluorescence detection (excitation 280 nm, emission at 320 nm) (A15). Other methods are based on borate-hydrochloric acid difference spectroscopy (this method suffers interference from tyrosine and tryptophan) (W2), derivatization of DOPA with nitrite and subsequent coulometric determination (W3), and fluorometric detection after derivatization with ethylenediamine (A15). 3-Hydroxylysine is quantitated by HPLC with 9-fluorenylmethyl chloroformate precolumn derivatization (M25) of amino acids obtained by gas-phase hydrolysis of proteins (F21). Other general methods to detect amino acid damage are mass spectometry methods applied to protein hydrolysates, such as tandem mass spectrometry (F6). 

Analysis of the enantiomeric ratios of several p-blocking drugs (l-aryloxy-3-isopropylamino-2-propanol derivatives) is carried out by HPLC with UV or fluorescence detection after derivatization with (R)-NEI or (i )-(+)-l-(l-phenyl)ethyl isocyanate (in a reversed-phase system), or (S)-NEI (on silica gel) only the amine function of the drugs reacts with the NEI the hydroxy group does not. Similar schemes for HPLC determination of enantiomeric purity of tetrahydrofolate derivatives and of fluoxetine are also reported. 

Reversed-phase HPLC with fluorescence detection, after derivatization of plasma thiols with ammonium 7-fluorobenzo-2-oxa-l,3-diazole-4-sulphonate (SBD-F), is the most widely used method to determine total plasma amino thiols (cysteine, cysteinylglycine, and homocysteine). The time required for sample preparation (thiolic reduction, deproteinization, and precolumn derivatization g with SBD-F) and for thiol derivatives separation is nearly 2 h per sample. =... 

High sensitivities in the pmol range are also possible in amino acid analysis by using fluorescence detection after derivatization with o-phthalaldehyde. 

High selectivities are also obtained by combining ion-exclusion chromatography with photometric detection after derivatization of the column effluent with suitable reagents. As a typical example, Fig. 4-6 shows the chromatogram of a 20-ppm silicate standard obtained by derivatization with sodium molybdate in acid solution and subsequent photometric detection at 410 nm. Orthophosphate may also be detected under these conditions. Because of its different acid strength it elutes prior to silicate, so that this method is very selective for the determination of both anions. 

Fig. 6-22. Analysis of nitrite, thiosulfate, and iodide upon application of fluorescence detection after derivatization with cerium(IV). — Separator column Vydac 302 IC eluent 0.001 mol/L KHP + 0.01 mol/L Na2S04 pH 5.5 with Na2B407 flow rate 1 mL/min detection fluorescence after reaction with cerium(IV) injection volume 100 pL solute concentrations 0.5 ppm nitrite, 1.1 ppm thiosulfate, and 1.5 ppm iodide (taken from [37]).

Figure 67 shows, as an example, the purity test of cimetidine on 10x10 cm or 5 x 5 cm HPTLC plates. The amount applied to the 10 x 10 cm plate was reduced to half the amount prescribed in the DAB, and the amount applied to the 5x5 cm plate was V4 of this. Whereas the limiting concentrations on the larger plate are just detectable after derivatization with iodine, a zone can be seen only on lane 2 of the smaller plate. 

In this interlaboratory test, the analysis was carried out using all appropriate techniques. Figure 13-7 shows the chromatogram of Sample A in non-acetylated (I) and acetylated (II) form. The amphetamine could only be detected after derivatization with acetic anhydride. In the acetylated sample, levallorphane and its metabolites were found. The presence of levallorphane can lead to a positive opiate test by the immunological method. 

Similar to Si, P as orthophosphate may be detected after derivatization with Sb(III) and Mo(VI) of the ternary heteropoly acid which is adsorbed onto the DME (detection limit being 5x10 mol 1 ). Phosphorus determination, like nitrite and nitrate determinations, is of importance for the evaluation of natural, waste, and potable water quality. 

Alpmann, A., Morlock, G. (2009) Rapid and cost-effective determination of acrylamide in coffee by planar chromatography and fluorescence detection after derivatization with dansulflnic acid. Journal ofAOAC International, 92, 725-729. 

Bell [526] analyzed transition metals together with magnesium and calcium utilizing ion pair chromatography on a chemically bonded reversed-phase column, which can be combined with both nonsuppressed conductivity detection and photometric detection after derivatization with PAR. Because Bell used predominantly ashed fermentation samples, his chromatograms are free of interferences. Simultaneous separations of alkali and alkaline-earth metals in methanotropic bacterial cultures and other media on surface-sulfonated... 

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