Zirconium(IV)-porphyrins as novel ionophores for fluoride-selective polymeric membrane electrodes

The feasibility of using Zr(IV)-porphyrins as novel ionophores for preparing anion-selective polymeric membrane electrodes is examined. Electrodes constructed using o-nitrophenyl octyl ether plasticized poly(vinyl chloride) membranes containing Zr(IV)-octaethylporphyrin (OEP) dichloride (Zr(IV)[OEP]Cl₂) or Zr(IV)-tetraphenylporphyrin (TPP) dichloride (Zr(IV)[TPP]Cl₂) were found to exhibit enhanced potentiometric selectivity toward fluoride compared to electrodes based on a typical anion-exchanger (e.g. tridodecylmethylammonium chloride). At pH 5.5, the electrodes displayed the following selectivity sequences: ClO₄⁻ > SCN⁻ > I⁻ > F⁻ > NO₃⁻ > Br⁻ > NO₂⁻ > Cl⁻ and F⁻ > ClO₄⁻ > SCN⁻ > I⁻ > NO₂⁻ > NO₃⁻ > Br⁻ > Cl⁻ for membranes doped with Zr(IV)[OEP]Cl₂) and Zr(IV)[TPP]Cl₂, respectively. Both ionophores are shown to operate via a charged carrier mechanism, with 10 mol% of lipophilic tetraphenylborate derivative in the membrane phase required to achieve optimal selectivity. Electrodes prepared with both metalloporphyrin species display super-Nernstian response toward fluoride with slopes typically greater than −100 mV per decade. It is shown, via UV-VIS spectroscopy of the membrane phase, that this behavior occurs due to spontaneous formation of hydroxide ion bridged porphyrin dimers in the membrane in the presence of the lipophilic anionic additive. The dimers are easily converted to monomeric species upon increasing the concentration of fluoride in the sample solution. Decreasing the pH of sample buffer background solution (from pH 5.5 to pH 3) decreases the lower detection limit (DL) of the electrode response toward fluoride (by two-order of magnitude) and improves the electrodes’ selectivity.     

Polymeric membrane electrodes with enhanced fluoride selectivity using Zr(IV)-porphyrins functioning as neutral carriers

Poly(vinyl chloride) polymeric membranes plasticized with o-NPOE (o-nitrophenyl octyl ether) or DOS (dibutyl sebacate) and containing Zr(IV)-octaethyl(OEP)- or Zr(IV)-tetraphenylporphyrins (TPP) along with lipophilic cationic additives (tridodecylmethylammonium chloride; TDMACl) are examined potentiometrically and optically with respect to their response toward fluoride. It is shown that these zirconium porphyrins can function as neutral anion carriers within the organic membranes of the electrodes. Spectrophotometric measurements of thin polymeric films indicate that the presence of lipophilic cationic sites in the form of TDMA⁺ and use of lower dielectric constant plasticizer (DOS) prevents formation of metalloporphyrin dimers in the organic polymer phase, which have been observed previously in polymeric membranes formulated with the same Zr(IV) porphyrins but with lipophilic anion site additives. By preventing dimer formation, rapid and Nernstian potentiometric response of the corresponding membrane electrodes toward fluoride ion is observed. Indeed, electrodes prepared with PVC/DOS membranes containing Zr(IV)-OEP and 15 mol% of TDMACl (relative to the ionophore) exhibit fast (t₉₅<15 s) and reversible response toward fluoride. The slope of calibration plots are near-Nernstian (−59.9 mV per decade). Such electrodes display the following selectivity pattern: ClO₄⁻>SCN⁻>F⁻>NO₃⁻>Br⁻>Cl⁻, which differs significantly from the classical Hofmeister series, with greatly enhanced potentiometric selectivity toward fluoride. The data presented herein, coupled with results from a previous study, confirm that Zr(IV) porphyrins can serve as either charged or neutral type anion carriers with respect to their enhanced interactions with fluoride when used as ionophores to prepare liquid-polymeric membrane electrodes, and that the nature of membrane additives and plasticizer dictates the response mechanism at play for given membrane formulations.     

Fluoride-selective sensors based on polyurethane membranes doped with Zr(IV)-porphyrins

The feasibility of using Tecoflex polyurethane as a polymeric matrix for fluoride-selective membranes doped with Zr(IV)-octaethyl-(OEP) or Zr(IV)-tetraphenylporphyrins (TPP) is examined. Membranes containing cationic or anionic additives were prepared, with ionophore working according to neutral or charged carrier mechanism, respectively. Results are compared to those found previously using conventional poly(vinyl chloride) (PVC) as the membrane matrix. It was found that this polymer does not affect significantly the properties of these porphyrins, compared to poly(vinyl chloride) matrix. A dimer-monomer equilibrium determined recently to occur for Zr(IV)-porphyrins in PVC/o-NPOE membranes containing lipophilic anionic additives is also observed to occur (via UV-vis spectrophotometry) in the PU matrix. However, the equilibrium constants for dimer-monomer reactions appear to be lower in PU membranes compared to PVC films, as determined from the degree of super-Nernstian responses towards fluoride as well as the anion concentration ranges required to break the dimer as determined spectroscopically. Due to reduced dimerization of Zr(IV)[OEP]Cl₂ it was possible to obtain electrodes with PU/o-NPOE/KTFPB membranes exhibiting only slightly super-Nernstian (−64.6 mV/dec) response towards fluoride and response time (t₉₅ < 120 s) faster than observed for PVC-based membranes. Good working parameters were also obtained for this metalloporphyrin in PU membrane that forces neutral carrier mechanism (PU/DOS/TDMACl): F⁻ calibration slope −58.3 mV/dec and response time t₉₅ < 12 s. Tested membranes were subsequently applied for construction of miniaturized silicon-based sensors. Better fluoride selectivity was observed for sensors with Zr(IV)[OEP]Cl₂/PU/o-NPOE/KTFPB membranes (: ClO₄⁻ 0.7; Br⁻ −1.9; NO₃⁻ −1.9; Cl⁻ −3.1), compared to Zr(IV)[OEP]Cl₂/PU/DOS/TDMACl matrix (: ClO₄⁻ −0.8; Br⁻ −1.3; NO₃⁻ −1.5; Cl⁻ −2.1). However, latter composition was chosen to be better for flow measurement mode, as dimer formation can be totally prevented within this membrane. Sensors with Zr(IV)[OEP]Cl₂/PU/DOS/TDMACl maintained their characteristics at least for 2 months.     

Rapid and Sensitive Spectrophotometric Determination of Hafuium(IV) With 2-(5-Bromo-2-Pyridylazo)-5-Diethylaminophenol

Abstract

Hafnium(IV) reacts with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in the pH range 3.3–11.0 to yield a sparingly soluble red-coloured chelate that can be dissolved with Triton X-100. Effect of initial pH of metal ion and order of addition of reagents was studied in detail. The 1:3 complex adheres to Beer's law over the concentration range 0.02–1.12 μg/ml of Hf(IV), has a molar absorptivity 1.33x10⁵ 1 mol^?1cm^?1, Sandell sensitivity 1.3 ng cm^?2, formation constant (log K) 11.94 and the method had a relative standard deviation of ± 1.5%. Effect of 60 diverse ions on the determination of hafnium(IV) was studied. This fairly selective method is the most sensitive so far reported for the spectrophotometric determination of hafnium(IV).     

A chelating resin containing 1-(2-thiazolylazo)-2-naphthol as the functional group; synthesis and sorption behavior for trace metal ions

A new polystyrene-divinylbenzene resin containing 1-(2-thiazolylazo)-2-naphthol (TAN) functional group was synthesized and its sorption behavior for 19 metal ions including Zr(IV), Hf(IV) and U(VI) was investigated by batch and column experiments. The chelating resin showed a high sorption affinity for Zr(IV) and Hf(IV) at pH 2. Some parameters affecting the sorption of the metal ions are detailed. The breakthrough and overall capacities were measured under optimized conditions. The overall capacities of Zr(IV) and Hf(IV) that were higher than those of the other metal ions were 0.92 and 0.87 mmol/g, respectively. The elution order of metal ions at pH 4 was evaluated as: Zr(IV)>Hf(IV)>Th(IV)>V(V)>Nb(V)>Cu(II)>U(VI)>Ta(V)>Mo(VI)>Cr(III)>Sn(IV)>W(VI). Quantitative recovery of most metal ions except Zr(IV) was achieved using 2 M HNO₃. Desorption and recovery of Zr(IV) was successfully performed with 2 M HClO₄ and 2 M HCl.     

Separation and simultaneous determination of niobium and tantalum in steel by reversed-phase high-performance liquid chromatography using 2-(2-pyridylazo)-5-diethylamino phenol as a pre-column derivatizing reagent

A method for the simultaneous determination of Nb and Ta in steel and alloy by reversed-phase high-performance liquid chromatography (RP-HPLC) was proposed. 2-(5-Bromo-2-pyridylazo)-5-diethylamino phenol (5-Br-PADAP) was used as a pre-column chelating agent to form a ternary complex with Nb(V) and Ta(V) and tartaric acid. The ternary complexes of Nb(V) and Ta(V) were eluted within 8 min on a C₁₈ column with a mobile phase of methanol-water (55:45, v/v) containing 10 mmol l⁻¹ acetate buffer (pH3.5) and determined with spectrophotometric detection at 598 nm. The detection limits for Nb(V) and Ta(V) were 0.60 and 0.72 μg l⁻¹, respectively, when the ratio of signal-to-noise is 3. The proposed method was used to analyze Nb and Ta in cast iron, alloy and stainless steel.     

Determination of indomethacin in urine using molecule imprinting-chemiluminescence method

A soluble Mn (IV)-formaldehyde-indomethacin chemiluminescence system was found. Using a synthesized indomethacin MIP as recognition material and soluble Mn (IV)-formaldehyde-indomethacin as detection system, a new molecule imprinted-chemiluminesence method of determination of indomethacin was established. The response range of this method was between 1.0 × 10⁻⁷ and 1.0 × 10⁻⁵ g/mL with a linear correlation coefficient of 0.994. The detection limit was 4 × 10⁻⁸ g/mL. The relative standard deviation for 5.0 × 10⁻⁷ g/mL of indomethacin solution was 3.1% (n = 7).     

Polymeric membrane electrodes with improved fluoride selectivity and lifetime based on Zr(IV)- and Al(III)-tetraphenylporphyrin derivatives

Novel aluminum(III)- and zirconium(IV)-tetraphenylporhyrin (TPP) derivatives are examined as fluoride-selective ionophores for preparing polymer membrane-based ion-selective electrodes (ISEs). The influence of t-butyl- or dichloro-phenyl ring substituents as well as the nature of the metal ion center (Al(III) versus Zr(IV)) on the anion complexation constants of TPP derivative ionophores are reported. The anion binding stability constants of the ionophores are characterized by the so-called “sandwich membrane” method. All of the metalloporphyrins examined form their strongest anion complexes with fluoride. The influence of plasticizer as well as the type of lipophilic ionic site additive and their amounts in the sensing membrane are discussed. It is shown that membrane electrodes formulated with the metalloporphyrin derivatives and appropriate anionic or cationic additives exhibit enhanced potentiometric response toward fluoride over all other anions tested. Since selectivity toward fluoride is enhanced in the presence of both anionic and cationic additives, the metalloporphyrins can function as either charged or neutral carriers within the organic membrane phase. In contrast to previously reported fluoride-selective polymeric membrane electrodes based on metalloporphyrins, nernstian or near-nernstian (−51.2 to −60.1 mV decade⁻¹) as well as rapid (t < 80 s) and fully reversible potentiometric fluoride responses are observed. Moreover, use of aluminum(III)-t-butyltetraphenylporphyrin as the ionophore provides fluoride sensors with prolonged (7 months) functional lifetime.     

Chemiluminescence determination of barbituric acid using Ru(phen)(3)(2+)-Ce(IV) system

A chemiluminescence (CL) method for the determination of barbituric acid (BA) was proposed, which is based on the enhancement of BA to the CL intensity of Tris-(1,10-phenanthroline)ruthenium(II) (Ru(phen)₃²⁺)-cerium(IV) (Ce(IV)) system. The concentration of BA is proportional to the CL intensity in the range of 5.0×10⁻³-2.0 μg ml⁻¹. The detection limit is 6.9×10⁻⁴ μg ml⁻¹. The relative standard deviation (R.S.D.) of determining 11 samples containing 0.20 μg ml⁻¹ BA is 3.2%. This CL method has been successfully applied to the determination of BA in the synthetic samples. The mechanism of CL reaction was studied.     

Reactions of the metallocene dichlorides [M(Cp)2Cl2] (M = Zr, Hf) and [Ti(MeCp)2Cl2] with the pyridine-2,6-dicarboxylate(−2) ligand: Synthesis, spectroscopic characterization and X-ray structures of the products

The reactivity pattern of the 16-electron species [M(Cp)₂Cl₂] (M = Zr, Hf; Cp⁻ = η⁵-C₅H₅⁻) and [Ti(MeCp)₂Cl₂] (MeCp⁻ = η⁵-C₅H₄CH₃⁻) towards the dipicolinate(−2) (dipic²⁻) ligand under mild (ambient temperature) and convenient (aerobic reactions, aqueous media) conditions have been investigated. The syntheses, molecular structures and spectroscopic (IR, ¹H NMR) characterization are reported for the 18-electron products [Zr(Cp)₂(dipic)] (1), [Hf(Cp)₂(dipic)] (2) and [Ti(MeCp)₂(dipic)] (3). The dipic²⁻ ion behaves as N,O,O′-chelating ligand in the three complexes, while the centroids of the Cp⁻ (1, 2) and MeCp⁻ (3) rings formally occupy the fourth and fifth coordination sites about the central metal. The two identical/very similar bite angles of only ∼70° make the dipic²⁻ ligand particularly suited to form stable metallocene derivatives with 5-coordinate geometry. IR and ¹H NMR data are discussed in terms of the known structures and the tridentate chelating mode of the dipic²⁻ ligand.     

Spectrophotometic Determination Of Tin In Steels With2-(5-Nltro-2-Pyridylazo)-5-[N-n-Propyl-N-(3-Sulfopropyl)Amino]phenol

ABSTRACT

A highly sensitive azo dye, 2-(5-nitro-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol (Nitro-PAPS), is used as a colorimetric reagent for the determination of tin(IV) content. Nitro-PAPS reacts with tin(IV) to form a water-soluble complex in 1.0 M acetic acid. Full color development is attained within 5 minutes, and maintains constant absorbance for at least 24 hours. The apparent molar absorptivity is 7.7 x 10⁴ dm³ mol^?1 cm^?1 at a maximum wavelength of 580 ran. Beer's law is obeyed for tin(IV) in the range of 0-1.2 μg ml^?1. The proposed method is successfully applied to the determination of trace amounts of tin in steels.     

Pre-column chelation liquid chromatographic separation and determination of trace V,Cu, Co,Pd, Fe and Ni

Conditions for the separation by reversed-phase liquid chromatography (LC) of V(V), Cu(II), Co(III), Pd(II), Fe(III) and Ni(II) chelates with 2-(5-bromopyridylazo)-5-diethylaminophenol (5-Br-PADAP) were studied. Six species of metal chelates were separated successfully with methanol-acetonitrile-water (72:12:16, v/v/v) containing 0.13 M NaCl and 0.29 mM cetyltrimethylammonium bromide (pH 5.0) as the mobile phase on a Nucleosil C₁₈ (5 μm) column (250 × 4 mm i.d.).The conditions of the determination of these metal chelates are discussed. A simple and rapid method for the determination of trace amounts of V(V), Cu(II), Co(III), Pd(II) and Ni(II) simultaneously by reversed-phase LC has been developed. The detection limits are 5 × 10^?12, 1 × 10^?10, 3 × 10^?11, 5.3 × 10^?9 and 2 × 10^?10 g, respectively. The method is applied to the determination of these metals in natural waters and mineral samples.     

Electrochemical Behavior of Novel Bis(β-diketonate)phthalocyanine Complexes of Zr(IV) and Hf(IV)

We have used cyclic voltammetry to study the electrochemical properties of novel bis(-diketonate)phthalocyanine complexes of Zr(IV) and Hf(IV) in dichloromethane. We found three waves for the studied complexes that can be attributed to one-electron processes MPc(L)^0/1– ₂, MPc(L)^1+/0 ₂ and MPc(L)^2+/1+ ₂. We have shown that the electrochemical behavior of the complexes depends on the nature of the substituents in axial ligands and does not depend on the nature of the metals. We have analyzed the stability of the one-electron oxidation products of the complexes relative to disproportionation.     

Reversed-phase liquid chromatographic determination of uranium based on its ternary complex with fluoride and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol. New chromatographic probe for the detection of fluoride on C18 stationary phase surface

Optimum conditions for the reversed-phase liquid chromatographic separation of uranium as U(VI)-F(-)-(5-Br-PADAP) [5-Br-PADAP is 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol] ternary complex on the end-capped C18 column were evaluated. The developed sensitive, selective and versatile method allows to determine uranium in the wide concentration range 0.2-120.0 mug ml(-1) (detection limit, DL, is 0.15 mug ml(-1) for 20 mul loop). Solvent mixture, acetonitrile+water (65+35, v/v) containing fluoride in concentration 3x10(-3) mol l(-1) (pH 5.5) was used as eluent. Double action of fluoride present in eluent - as stabilising agent of the ternary system and modifier of the stationary phase was evaluated. In order to prove appearance of the modifying effect of fluoride on the stationary phase the new chromatographic probe - system Zr(IV)-(5-Br-PADAP)/Zr(IV)-F(-)-(5-Br-PADAP) was introduced as a tool for the detection of F(-) presence on the surface.     

Simultaneous determination of Zr(IV) and Hf(IV) by CE using precolumn complexation with a [PW(11)O(39)](7-) ligand

A CE method was developed for the simultaneous determination of Zr(IV) and Hf(IV) at trace levels. A lacunary Keggin-type [PW(11)O(39)](7-) ligand reacted quantitatively with a mixture of trace amounts of Zr(IV) and Hf(IV) to form the so-called ternary Keggin-type anions [P(Zr(IV)W(11))O(40)](5-) and [P(Hf(IV)W(11))O(40)](5-) in 0.010 M monochloroacetate buffer (pH 2.2). Since both ternary anions possessed different electrophoretic mobilities and high molar absorptivities in the UV region, Zr(IV) and Hf(IV) were determined simultaneously with direct UV detection at 258 nm. Each peak height was linearly dependent on the concentration of Zr(IV) or Hf(IV) in the range of 5.0x10(-7)-1.0x10(-5) M; a detection limit of 2x10(-7) M was achieved. The utility of the proposed CE method was demonstrated for the simultaneous determination of Zr(IV) and Hf(IV) in natural water samples with satisfactory results.     

Chemometric optimization of a SIA promethazine hydrochloride assay method

A sequential injection analysis (SIA) method for the assay of promethazine hydrochloride, based on its oxidation by acidified cerium(IV), was optimized. Three chemometric approaches were applied: (i) factorial design (3³ applied to surface plot and 2³ applied to effect factor) for screening the potential interacting variables, (ii) univariant for optimizing insignificantly interacting variables and (iii) simplex for optimizing potentially interacting variables. The optimum experimental conditions were 30 μl of 0.38 mol/l sulphuric acid, 30 μl of 3.99 × 10^− 3 mol/l cerium(IV), 20 μl of promethazine hydrochloride and 20 μl/s flow rate. The detection limit was 7.032 × 10^− 5 mol/l and the calibration curve was linear up to 1.563 mol/l with a correlation coefficient 0.9998, accuracy range of 89.0-101.5%, relative standard deviation 1.1% (n = 10) and sample frequency at least 20 samples/h. The method was applied to tablet form and validated with the British Pharmacopoeia method. The developed SIA method is fully automated, reproducible, sensitive, rapid and reagent-saving, and therefore suitable for routine control in tablets form.     

Xylenol Orange,Zirconium(IV) and Fluoride Color Reaction in Mixed Micelles of N-Hexadecylpyridinium Chloride and Brij 35, and Its Analytical Application1

Abstract

The color reaction between Xylenol orange (XO), zirconium (IV) and fluoride ions in the presence of various surfactants alone or in combination was studied at various pH. The XO -zirconium)IV)-fluoride ion ternary complex in mixed micellar media containing a low concentration of N-hexadecylpyridinium chloride (HPC) as a cationic surfactant and large amounts of (poly{oxyethylene)dodecyl ether (Brij 35) as a nonionic surfactant at weakly acidic media was found to be the most stable, and showed a remarkable bathochromic shift and clear contrast against a reagent blank. The maximum absorbance was at 600 nm in the mixed micellar media at pH 3.5, and the apparent molar absorptivities at 600 nm were 7.0 × 10⁴ 1 mol^?1 cm^?1 for zirconium(IV) and 1.4 × 10⁴ 1 mol^?1 cm^?1 for fluoride ion. The calibration curves covered the ranges of 0.5 ～ 20.0 μg/10 ml zirconium! IV) and 0 ～ 20.0 μg/10 ml fluoride ion with the Sandell sensitivities being 0.0013 μg/cm² for zirconium(IV) and 0.0016 μg/cm² for fluoride ion.     

Sulfonylcalix[4]arenetetrasulfonate as pre-column chelating reagent for selective determination of aluminum(III), iron(III), and titanium(IV) by ion-pair reversed-phase high-performance liquid chromatography with spectrophotometric detection

Sulfonylcalix[4]arenetetrasulfonate (SO₂CAS) has been examined as a pre-column chelating reagent for ultratrace determination of metal ions by ion-pair reversed-phase high-performance liquid chromatography with spectrophotometric detection. Metal ions were converted into the SO₂CAS chelates in an acetic buffer solution (pH 4.7). The chelates were injected onto a n-octadecylsilanized silica-type Chromolith™ Performance RP-18e column and were eluted using a methanol (50 wt.%)-water eluent (pH 5.6) containing tetra-n-butylammonium bromide (7.0 mmol kg⁻¹), acetate buffer (5.0 mmol kg⁻¹), and disodium ethylendiamine-N,N,N′,N′-tetraacetate (0.10 mmol kg⁻¹). Under the conditions used, Al(III), Fe(III), and Ti(IV) were selectively detected among 21 kinds of metal ions [Al(III), Ba(II), Be(II), Ca(II), Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Ga(III), Hf(IV), In(III), Mg(II), Mn(II), Mo(VI), Ni(II), Pb(II), Ti(IV), V(V), Zn(II), and Zr(IV)]. The detection limits on a 3σ blank basis were 8.8 nmol dm⁻³ (0.24 ng cm⁻³) for Al(III), 7.6 nmol dm⁻³ (0.42 ng cm⁻³) for Fe(III), and 17 nmol dm⁻³ (0.80 ng cm⁻³) for Ti(IV). The practical applicability of the proposed method was checked using river and tap water samples.     

Voltammetric determination of hafnium with calconcarboxylic acid

The interaction of Hf(IV) with calconcarboxylic acid (1-(2-hydroxy-4-sulfo-1-naphtylazo)-3-naphtolic acid) was investigated by cyclic voltammetry varying various factors (pH, ionic strength, contents of ethanol and scan rate). Optimal conditions of Hf(IV) determination in the presence of calconcarboxylic acid were found: acetic buffer solution pH 2.6, scan rate 0.5 Vs⁻¹. The detection limit of Hf(IV) concentration was 2.46 × 10⁻⁷ mol L⁻¹. The influence of foreign ions on the Hf(IV) determination was studied. It was established that some metals like cadmium, nickel, zinc, copper and titanium could be determined with Hf(IV) simultaneously. The method of voltammetric determination of hafnium was tested on model solutions and used in the determination of Hf(IV) in terbium-base alloy.     

Visual and surface plasmon resonance sensor for zirconium based on zirconium-induced aggregation of adenosine triphosphate-stabilized gold nanoparticles

Owing to its high affinity with phosphate, Zr(IV) can induce the aggregation of adenosine 5′-triphosphate (ATP)-stabilized AuNPs, leading to the change of surface plasmon resonance (SPR) absorption spectra and color of ATP-stabilized AuNP solutions. Based on these phenomena, visual and SPR sensors for Zr(IV) have been developed for the first time. The A_660 nm/A_518 nm values of ATP-stabilized AuNPs in SPR absorption spectra increase linearly with the concentrations of Zr(IV) from 0.5 μM to 100 μM (r = 0.9971) with a detection limit of 95 nM. A visual Zr(IV) detection is achieved with a detection limit of 30 μM. The sensor shows excellent selectivity against other metal ions, such as Cu²⁺, Fe³⁺, Cd²⁺, and Pb²⁺. The recoveries for the detection of 5 μM, 10 μM, 25 μM and 75 μM Zr(IV) in lake water samples are 96.0%, 97.0%, 95.6% and 102.4%, respectively. The recoveries of the proposed SPR method are comparable with those of ICP-OES method.