An online solid phase extraction method for the determination of ultratrace level phosphate in water with a high performance liquid chromatograph

Abstract

Phosphorous monitoring is important for eutrophication control in aquatic ecosystems, but ultratrace level concentrations may not be detected by conventional analytical methods. A method for measuring ultratrace level phosphate by online solid-phase extraction combined with HPLC was developed. A short column (50 mm) packed with octadecylsilane (ODS) was used for extraction of phosphoantimonylmolybdenum blue and dodecyltrimethylammonium hydrophobic ion-pair complexes. The ion-pair complexes entrapped on the ODS column were eluted with CH 3 CN/H 2 O (35/65; flow rate, 1.0 ml min-1) and monitored by an ultraviolet/visible spectrophotometer (=872 nm). Phosphate concentration was determined from the peak area of the ion pair. The limit of detection for orthophosphate was 0.15 μg PO 4 l-1 and the dynamic range was 0.15-100 μg PO 4 l-1. Although our method was susceptible to silicate interference, it could be corrected by a proposed interference correction equation.

Colorimetric determination of trace orthophosphate in water by using C18-functionalized silica coated magnetite

“…Type and concentration of eluent should be optimized so it can effectively elute the PMB–CTAB complex from Fe 3 O 4 @SiO 2 @C 18 . Polar organic solvents have been shown to be effective for eluting 10 , 15 the ion pair complex of phosphomolybdic acid and a cationic surfactant in an aqueous medium. Hence, ethanol was chosen for this work because of its compatible polarity, cost, availability and environment friendliness.…”

“…Even though the techniques offer low limits of detection and high enhancement factor however, the procedures are not simple and handling the liquid extractant require certain skills. Another approach that not only improve the sensitivity but also simplifies the procedures is to exploit solid-phase extraction (SPE) with different types of solid sorbent 10 – 15 . Those solid sorbent particles can be classified into two groups: non-magnetic and magnetic.…”

“…Non-magnetic particles with C 18 –functionalized surfaces have been employed in both off-line and on-line extraction for o -PO 4 3− determination in aqueous samples 10 , 15 . First the o -PO 4 3− was converted to phosphomolybdenum blue complex (PMB) and followed by formation of a neutral ion pair complex with cationic surfactants such as cetyltrimethylammonium bromide (CTAB) 10 and dodecyltrimethylammonium bromide (DTAB) 15 . Then the neutral ion pair complex (PMB-CTAB or PMB-DTAB) was adsorbed onto the C 18 particles via hydrophobic interaction before the adsorbed C 18 particles were collected.…”

A membrane extraction method for trace level phosphate analysis

“…12 It is well known that PAMB and phosphomolybdate are anionic species that form ion pairs with organic cations such as a cationic dyes and quaternary ammonium ions. 6 The ion pair can be also trapped effectively on a membrane lter by suction ltration. The packing materials were silica gel or polyvinyl chloride (PVC) particles coated with quaternary ammonium ions.…”

“…1 The biological uptake of phosphate depletes its concentrations in surface waters to nano-molar levels. 2,3 In oligotrophic lakes, mountain streams and open oceans, the phosphate concentration is oen at trace levels, [4][5][6] which is below the limit of detection (LOD) of standard methods for measuring the phosphate concentration (10 mg P L À1 ; 7 ). The investigations of phosphate behavior in natural water systems and the development of phosphate removal technologies in wastewater treatment processes require a simple detection technology for trace level phosphate.…”