Complexation of Be(II) Ion with 1-(2,4-Dihydroxy-1-phenylazo)-8-hydroxy-3,6-naphthalenedisulfonate as the Chemical Basis of the Selective Detection of Ultratrace Be by Reversed-Phase High-Performance Liquid Chromatography

Abstract

The complexation reactions of beryllium(II) ion with 1-(2,4-dihydroxy-1-phenylazo)-8-hydroxy-3,6-naphthalenedisulfonate (H-resorcinol) are studied. The acid dissociation constants of H-resorcinol, H(3)L(2-), at 293 K and I = 0.10 [K(OH, NO(3))] are pK(a)((1)) = 5.67, pK(a)((2)) = 8.57, and pK(a)((3)) > 13. The formation constant at 293 K and I = 0.10 [(K,H)NO(3)] is estimated to be log[{[Be(HL)(2-)][H(+)](2)}/{[Be][H(3)L(2-)]}] = -4.58, and pK(a)' = 6.39 for [Be(HL)](2-), which give the basis for the optimization of the precolumn chelation reactions and the masking system with EDTA. The kinetic data for ligand substitution reactions with sulfosalicylate ion are also reported to demonstrate the remarkable inertness of the Be chelate, which is suitable for HPLC separation. Reported is an accurate method for determining traces of Be(II) ion at nanomolar levels with photometric detection coupled with ion-pair reversed-phase HPLC. The chelate, [Be(II)L](3-), is efficiently separated on an Asahipak ODP-50 column using tetrabutylammonium bromide as an ion-pairing agent in a methanol (35 wt %)-water eluent. Only Al and Fe give peaks under the conditions used. The large molar absorptivity of the H-resorcinol chelate, 3.99 × 10(4) M(-1) cm(-1) at 500 nm, and the short retention time with excellent peak resolution ensure the ultralow detection limit (3σ blank) down to 7.2 ppt (0.8 nM) with no preconcentration procedures. The excellent toughness toward the matrix influence was demonstrated using the model solution for an air-dust sample. The HPLC separation, coupled with the EDTA masking procedure, enables one to detect Be(II) ion at 20 nM in the presence of metals at the natural abundance levels in air samples, such as Al, Fe, Ca, Mg, Zn, and Pb at 240, 140, 300, 66, 16, and 6.2 μM, respectively, in the final solution.

Determination of Cobalt in Natural Water as a 2-(5-Bromo-2-pyridylazo)-5-[N-propyl-N-(3-sulfopropyl)amino]phenol Chelate by On-Line Preconcentration HPLC with Column-Switching Technique

“…The other chelates dissociated in the column because of a lack of 5-Br-PAPS in the eluent. 27 The detected chelates and the elution order in Fig. 2 were similar to the ones of 5-Br-PADAP chelates.…”

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“…Previously, we have reported the simple and cost-effective method for determination of ultratrace Be(II) ion: reversed-phase high-performance liquid chromatography (RP-HPLC) with photometric detection using 1-(2,4-dihydroxy-1-phenylazo)-8-hydroxy-3,6-naphthalene disulfonate (H-resorcinol) as a precolumn chelation reagent. 21 An alternative approach to the sensitive detection of ultratrace Be with simplicity and cost-effectiveness is solution spectrofluorimetry. However, the existing fluorimetric methods do not seem to allow the requisite conditions for environmental analysis, detectability for the pg cm 23 range with compatibility to matrix toughness.…”

Determination of Carbetamide in Water by Micro Liquid-Liquid Extraction Followed by HPLC

“…Other methods to overcome these difficulties have also been used, such as noise/signal ratio (S/N = 2 or S/N = 3), with the DL defined as that amount required to give a signal 2 or 3 times the background noise (11)(12)(13). In previous papers, we have been using criteria according to IUPAC recommendations applying it to transient techniques, such as Gas Chromatography (GC) (14), High Performance Capillary Electrophoresis (HPCE) (15), and Differential Pulse Voltammetry (DPV) (16).…”