Phosphorus-selective detector, HPLC

Detectors such as laser fluorometry, FT-IR, mass spectrometer and flame-based detectors can be used to obtain desired selectivity and resolution. A phosphorus-selective detector for HPLC can provide ultrahlgh resolution. In the phosphorus-selective chromatogram, the analyte peak is well resolved from neighboring peaks and the slgnal-to-nolse ratio Is also much higher than for the RI detector (13). 

Where the target analyte contains heteroatoms such as nitrogen, phosphorus and sulfur, atom-selective detectors can provide an ideal detection method. A number of examples appear in the literature of the use of a detector called a thermal energy analyser (TEA) for the measurement of A-nitroso compounds [14-17] and aromatic nitro compounds [18]. This has also been used as an HPLC detector [19, 20], and a modified TEA has been reported to be useful for analysis of amines and other nitrogen-containing compounds [17]. Unfortunately, this technique appears not to have gained in popularity, since no reports have appeared in the literature for over two decades. 

Organochlorine pesticides and OPPs have been determined mainly using GC, because of the stability and volatility that most of them show under chromatographic conditions and, particularly, the availability of element-selective detectors that display high selectivity for OCPs (electron-capture detector, ECD), and OPPs (flame photometric detector, FPD, and nitrogen phosphorus detector, NPD). Mass spectrometry-based detection is also more popular in GC than in HPLC (1,2,12,16). 

Traditionally, gas chromatography (GC) was the preferred approach for the analysis of pollutants in water, due to the high sensitivity and selectivity achieved, thanks to its selective detectors such as the nitrogen-phosphorus (NPD), the flame photometric detector (FPD), and electron-capture detector (ECD), and to the ease of coupling to mass spectrometry (MS). However, high-performance liquid chromatography (HPLC or LC) is the most powerful approach for the determination of polar, nonvolatile, and thermolabile compounds (i.e., those which are not GC amenable). 

As mentioned in the Section 1, physico-chemical methodology for quantitative analysis of plant hormone focuses primarily on GC-SIM, although HPLC with selective fluorescence detection continues to be used for lAA analysis in some laboratories. Procedures, such as the 2-methylindolo-a-pyrone assay for lAA analysis [82], are now rarely utilised. With the exception of ethylene quantification [2] there is little use of non-MS-based GC detection techniques, despite the fact that selective analysis at the picogram level is achieved for ABA with an electron capture detector [83], and lAA and cytokinins with a nitrogen phosphorus detector [84,85]. The reason for the demise of these GC procedures is that the detectors are destructive and this precludes the reliable recovery of labelled internal standards for radioassay and isotopic dilution analysis. The usual compromise was to take two aliquots of the purified samples, one for GC analysis and the other for the determination of radioactivity. The accuracy of this approach is dependent upon the questionable assumption that the radioactivity in the purified sample is associated exclusively with the compound under study. In an attempt to circumvent this problem, a double standard isotope dilution procedure was devised for the quantitative analysis of lAA in which one internal standard was used to correct for losses during sample preparation and a second for GC quantification [86]. This procedure was used in several... 

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