Arsonic acids detection

Arsonic acids are easily detected on paper electrophoresis and chromatography by the fact that they bind Fe3+ tightly. Hence, they show up in the test of Wade and Morgan (130) for phosphates, in which the paper is sprayed with a solution of FeCl3 (1%) and sulfosalicylic acid (1%). Phosphonates and arsonates show up like phosphates as white spots on a purple background, because they remove the Fe3+ from its purple complex with the acid. For following column effluent, a test with a similar principle may be used. The sample is mixed with a buffered, acidic solution of Fe3+ and azide, and the absorbance at 450 nm is diminished by phosphates and phosphonates (52) we have since used this method successfully with arsonates. 

HPLC units have been interfaced with a wide range of detection techniques (e.g. spectrophotometry, fluorimetry, refractive index measurement, voltammetry and conductance) but most of them only provide elution rate information. As with other forms of chromatography, for component identification, the retention parameters have to be compared with the behaviour of known chemical species. For organo-metallic species element-specific detectors (such as spectrometers which measure atomic absorption, atomic emission and atomic fluorescence) have proved quite useful. The state-of-the-art HPLC detection system is an inductively coupled plasma/MS unit. HPLC applications (in speciation studies) include determination of metal alkyls and aryls in oils, separation of soluble species of higher molecular weight, and separation of As111, Asv, mono-, di- and trimethyl arsonic acids. There are also procedures for separating mixtures of oxyanions of N, S or P. 

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