Separation and spectrophotometric determination of very low levels of Cr(VI) in water samples by novel pyridine-functionalized mesoporous silica

A modified SBA-15 mesoporous silica was developed, as an adsorbent, for the removal of Cr(VI) ions from natural-water samples. The effects of experimental parameters, including pH of solution, sample and eluent flow rate, the eluent composition, the eluent volume, and the effect of coexisting ions on the separation and determination of Cr(VI), were investigated. It was shown that Cr(VI) was selectively adsorbed from aqueous solution at pH 3, but Cr(III) could be adsorbed from solution at alkaline pH range. The retained Cr(VI) was eluted with 0.5?mol?L^?1 KCl solution in 0.1?mol?L^?1 Na₂CO₃ subsequently. Under the optimum conditions, the modified mesoporous silica (py-SBA-15) with a high pore diameter exhibited an adsorption capacity of 136?mg?g^?1 and a lower limit of detection than 2.3?µg?L^?1 by using diphenylcarbazide as a chromophorous reagent for the determination of Cr(VI) ions. A preconcentration factor as high as 200 was calculated for Cr(VI). The loaded py-SBA-15 can be reactivated with recovery of more than 98.5% over at least eight cycles. The relative standard deviation (RSD) for Cr(VI) ion recovery was less than 1.8%. Validation of the outlined method was performed by analysing a certified reference material (BCR 544). The proposed method was applied to determine Cr(VI) value in natural and waste water samples successfully.     

Comparative Study of Chromium Biosorption by Mesorhizobium amorphae Strain CCNWGS0123 in Single and Binary Mixtures

The appearance of chromium in the aqueous effluent is a major concern for the modern industry. In this work, Mesorhizobium amorphae strain CCNWGS0123 was investigated as a biosorbent to remove chromium from aqueous solutions. The optimum pH for Cr(III) and Cr(VI) biosorption were 4 and 2, respectively. This isolate showed an experimental maximum Cr(III) adsorption capacity of 53.52 mg?L^?1, while the result was 47.67 mg?L^?1 for Cr(VI), with an initial 100 mg?L^?1 Cr ions and 1.0 g?L^?1 biomass. In terms of time equilibrium, Cr(III) ion was more readily adsorbed than Cr(VI) by this isolate. The biosorption data of both ions fit the Langmuir isotherm better than that of Freundlich model. Meanwhile, this organism exhibited a good capability to release Cr ions, with desorption efficiency of 70 % for Cr(III) and 76 % for Cr(VI). Fourier transform infrared spectroscopy analysis showed that –OH, –COO, –NH, amide I, and C=O were involved in Cr(III) and Cr(VI) binding. The biosorbent was further characterized by scanning electron microscopy and energy-dispersive X-ray spectrometry, which indicated an accumulation of chromium on the cellular level. In the binary mixtures, the removal ratio of total Cr and Cr(III) increased from pH?2 to 4. The highest removal ratio of the total Cr was observed in the 25/25 mg?L^?1 mixture at pH?4. In addition, the removal efficiency of Cr(VI) was closely influenced by Cr(III) in the mixture, decreasing to 23.57 mg?g^?1 in the 100/100 mg?L^?1 mixture system, due to the competition of Cr(III). The potential usage of the chromium-resistant rhizobium for the remediation of chromium-contaminated effluents has been demonstrated based on the above results.     

Heavy Metal Resistances and Chromium Removal of a Novel Cr(VI)-Reducing Pseudomonad Strain Isolated from Circulating Cooling Water of Iron and Steel Plant

Three bacterial isolates, GT2, GT3, and GT7, were isolated from the sludge and water of a circulating cooling system of iron and steel plant by screening on Cr(VI)-containing plates. Three isolates were characterized as the members of the genus Pseudomonas on the basis of phenotypic characteristics and 16S rRNA sequence analysis. All isolates were capable of resisting multiple antibiotics and heavy metals. GT7 was most resistant to Cr(VI), with a minimum inhibitory concentration (MIC) of 6.5 mmol L^?1. GT7 displayed varied rates of Cr(VI) reduction in M2 broth, which was dependent on pH, initial Cr(VI) concentration, and inoculating dose. Total chromium analysis revealed that GT7 could remove a part of chromium from the media, and the maximum rate of chromium removal was up to 40.8 %. The Cr(VI) reductase activity of GT7 was mainly associated with the soluble fraction of cell-free extracts and reached optimum at pH 6.0～8.0. The reductase activity was apparently enhanced by external electron donors and Cu(II), whereas it was seriously inhibited by Hg(II), Cd(II), and Zn(II). The reductase showed a K _m of 74 μmol L^?1 of Cr(VI) and a V _max of 0.86 μmol of Cr(VI) min^?1 mg^?1 of protein. The results suggested that GT7 could be a promising candidate for in situ bioremediation of Cr(VI).     

Determination of cadmium, chromium and copper in high salt samples by LA-ICP-OES after electrodeposition—preliminary study

A novel method is presented for determination of heavy metal ions in a high-saline matrix. It is based on the electrodeposition of the ions and subsequent laser ablation coupled to inductively coupled plasma optical emission spectrometry (LA-ICP-OES). Three arrangements for electrodeposition were worked out, two of them with stationary working electrodes. Materials for use in the working electrodes, and conditions for electrodeposition of Cd, Cr and Cu (pH, deposition current, time of electrolysis) were studied. Nickel was found to be the best electrode material. The metals accumulate on the surface of electrode and were then evaporated/ablated with a Nd:YAG laser focused into the ICP-OES spectrometer. The detection limits are 0.13 mg?L^?1 for Cd, 0.15 mg?L^?1 for Cu, and 1.9 mg?L^?1 for Cr in case of a stationary bottom working electrode, and 0.25 mg?L^?1 for Cd, 0.05 mg?L^?1 for Cu, 0.8 mg?L^?1 for Cr when using a rotating electrode. The relative standard deviation is in range from 3.8 to 10.3%. Waste water was analyzed in this way by the standard addition method.     

Preconcentration of total chromium on Dowex 50W-X8 resin loaded with 2-amino-benzenethiol

Application of Dowex 50W-X8 loaded with 2-amino-benzenethiol for preconcentration of total chromium (Cr(VI) and Cr(III)) in water samples and subsequent determination by inductively coupled plasma-atomic emission spectrometry was studied. The reagent 2-amino-benzenethiol loaded onto the resin effectively reduced Cr(VI) to Cr(III) and total chromium (both Cr(VI) and Cr(III)) formed chelate complex with the reagent in the Cr(III) valence state. Experimental parameters such as preconcentration time, solution flow rates, pH, and concentration of the eluent were optimized. The method has been applied for the determination of total chromium in seawater samples in the range of 0.1–200?µg?L^?1. A detection limit of 0.3?µg?L^?1 was achieved, and the relative standard deviation was about 5%.     

Application of stripping voltammetry method for the analysis of available copper,zinc and manganese contents in soil samples

Determination of copper (Cu), zinc (Zn) and manganese (Mn) micronutrients in soil samples have been studied for an efficient fertiliser application. Plant-available micronutrients of soils were extracted with DTPA extraction procedure, then differential pulse stripping voltammetry (DPSV) and square wave stripping voltammetry (SWSV) methods were performed with inexpensive and disposable pencil graphite electrode for determination of Cu(II), Zn(II) and Mn(II). Parameters such as deposition potential, deposition time, pH and concentration of the supporting electrolyte were optimised for these ions. Under optimised conditions, the limits of detection were found as 0.01 mg L^?1 for Cu(II) and 0.02 mg L^?1 for Zn(II) and 0.25 mg L^?1 for Mn(II). Relative standard deviation (%RSD) was 6.80, 8.86 and 3.29 for Cu(II), Zn(II) and Mn(II), respectively. The experimental study was conducted using a flame atomic absorption spectroscopy. The described stripping voltammetry methods were successfully applied for the determination of Mn(II), Cu(II) and Zn(II) in soil samples.     

Determination of seven trace elements in natural waters by neutron activation analysis after preconcentration with 1-(2-pyridylazo)-2-naphthol

A procedure is described for the preconcentration of Cd(I), Co(II), Cr(III), Cu(II), Mn(II), U(VI) and Zn(II) from 800 ml of water and sea-water samples by coprecipitation with 1-(2-pyridylazo)-2-naphthol (PAN) prior to neutron activation. Chromium is reduced to Cr(III) by hydroxylammonium chloride at pH 4 before the preconcentration step. Coprecipitation of 30 mg of PAN was most effective at pH 9 with final recoveries of 76–91% for six elements and 50% for uranium. The scheme is based on double irradiation of the same samples. Short (10 min) irradiation followed by γ-spectrometry counting for 10 min gives data for Cd (^111mCd), Co, Cu, Mn and U (²³⁹U). A second 16-h irradiation permits determination of zinc and uranium (²³⁹Np) after a waiting time of 6 h, cadmium (¹¹⁵Cd) after 24 h and chromium after a waiting period of 2 weeks followed by counting for 30 min. Detection limits are 0.04 ng g^?1 for Co, 0.8 ng g^?1 for Cd, 0.3 ng g^?1 for Cu, 0.2 ng g^?1 for Cr, 0.006 ng g^?1 for Mn, 0.006 ng g^?1 for U and 0.3 ng g^?1 for Zn. A further decrease of the detection limit for chromium to 0.05 ng g^?1 can be achieved by separation of interfering nuclides and scintillation counting of ⁵¹Cr with a NaI(Tl) well-type detector.     

Determination of trace amounts of chromium (VI) by flow injection analysis with chemiluminescence detection

A new sensitive chemiluminescence (CL) method combined with continuous flow injection analysis is described for the determination of Cr(VI). Strong CL signals were generated by Cr(VI)-catalysed oxidation of gallic acid in the presence of potassium permanganate and hydrogen peroxide. Effects of reagent concentrations, temperature, pH, flow rates, mixing coil length and mixing flow sequences on the chemiluminescence intensity were studied. Under the optimised experimental conditions, the relationship between the logarithm of concentration (log?C) of Cr(VI) and the logarithm of intensity (log?I) is linear over the range of 2?×?10^?11 – 5?×?10^?4?mol?L^?1, with the detection limit (3σ) of 4?×?10^?12?mol?L^?1. Relative standard deviation of ten measurements of 1?×?10^?9?mol?L^?1 Cr(VI) is 1.7%. This flow injection analysis (FIA) system proved to be able to analyse up to 40 samples h^?1. Effects of various interferences possibly present in the water samples were investigated. Most cations and anions, as well as organic compounds, did not interfere with the determination of Cr(VI) in water samples. The experimental results obtained for chromium in reference materials were also in good agreement with the certified values.     

Spectrophotometric determination of Chromium(VI) using cyclam as a reagent

A simple, rapid, sensitive, and inexpensive method for spectrophotometric determination of chromium(VI), based on the absorbance of its complex with 1,4,8,11-tetraazacyclotetradecane (cyclam) is presented. The complex showed a molar absorbtivity of 1.5?×?10⁴?L?mol^?1?cm^?1 at 379?nm. Under optimum experimental conditions, a pH of 4.5 and 1.960?×?10³?mg?L^?1 cyclam were selected, and all measurements were performed 10?min after mixing. Major cations and anions did not show any interference; Beer's law was applicable in the concentration range 0.2–20?mg?L^?1 with a detection limit of 0.001?mg?L^?1. The standard deviation in the determination is ±0.5?mg?L^?1 for a 15.0?mg?L^?1 solution (n?=?7). The described method provides a simple and reliable means for determination of Cr(VI) in real samples.     

Separation of chromium (VI) using complexation and its determination with GFAAS

In acidic medium and in the presence of chloride ions 2-[2-(4-methoxy-phenylamino)-vinyl]-1,3,3-trimethyl-3H-indolium chloride forms complex with Cr(VI). The optimum conditions (pH, concentration of Cl^- and the complex forming reagent) of the separation and extraction of Cr(VI) into toluene using this basic dye as a complexing reagent have been determined and the possible interferences of Ca, Mg, Na, K, Cr(III), Ni, Pb, Hg, Mn, Al, Cu have been studied. An electrothermal atomic absorption spectrometer (GFAAS) was used for the determination of Cr(VI). The detection limit of the method for Cr(VI) found to be 0.15 μg dm^− 3 and RSD for spiked drinking water was better than 3%.     

Chemically modified silica gel for selective solid-phase extraction and preconcentration of heavy metal ions

This paper describes our research on the synthesis of the sorbent with chemically bonded ketoimine groups, and, furthermore, using this sorbent in the SPE technique to extract and preconcentrate trace amounts of metal ions in water samples. Surface characteristics of the sorbent were determined by elemental analysis, NMR spectra for the solid phases (²⁹Si CP MAS NMR), and analysis of pore size distribution of the sorbent and nitrogen adsorption-desorption. The newly proposed sorbent with ketoimine groups was applied for the extraction and preconcentration of trace amounts of Cu (II), Cr (III) and Zn (II) ions from the water from a lake, post-industrial water and purified water unburdened back to the lake. The determination of the transition-metal ions was performed on an emission spectroscope with inductively coupled plasma ICP-OES. For the batch method, the optimum pH range for Cu (II) and Cr (III) extraction was equal to 5, and Zn(II)–to 8. All the metal ions can be desorbed from SPE columns with 10?mL of 0.5?mol?HNO₃. The detection limits of the method were found to be 0.7?µg?L^?1 for Cu (II), 0.08?µg?L^?1 for Cr (III), and 0.2?µg?L^?1 for Zn (II), respectively.     

Evaluation of Manganese(II) and Manganese(VII) Speciation in Water Samples by Ion Pair High-performance Liquid Chromatography-inductively Coupled Plasma Mass Spectrometry

The speciation of Mn(II) and Mn(VII) is reported by ion pair chromatography. To optimize the separation, sample pH, ion pair reagent, Mn(II) complexing agent, and composition of mobile phase were characterized. The separation of Mn(II) and Mn(VII) was performed using ethylenediamine tetraacetic acid to complex Mn(II), tetrabutylammonium hydroxide as an ion pair reagent, and a C8 column. The separation of the manganese species was demonstrated by high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC ICP-MS). The conversion of Mn(VII) to Mn(II) occurred during the separation and influenced the quantification; hence, the factors affecting this process including the storage time, manganese species ratio, and sample matrix composition were evaluated and suitable calibration was demonstrated. The method was validated by characterization of the selectivity, specificity, linearity, limits of detection and quantification, repeatability, and intermediate precision. The detection limit for Mn(II) was 0.22 µg?L^?1, while for Mn(VII), the value was 1.55 µg?L^?1.     

Selective back-extraction and preconcentration of zinc(II) from metal-1,3,5-triketone extracts prior to its determination by flame atomic absorption spectrometry

A simple back-extraction method was developed for the separation and preconcentration of trace levels of zinc from different matrices. Ethyl-2-(4-methoxybenzoyl)-3-(4-methoxyphenyl)-3-oxopropanoylcarbamate (EMPC) was used as a new complexing agent for the extraction of zinc(II) from the aqueous sample phase to the methyl isobutyl ketone (MIBK) phase as Zn(EMPC)₂ complexes. The Zn(II) can be selectively stripped with 1?mL of 0.5?mol?L^?1 HCl from Mⁿ⁺(EMPC)_n complexes [Ag(I), Al(III), Cd(II), Cr(III), Cu(II), Fe(II), Fe(III), Mn(II), Ni(II), Pb(II) and Pd(II)] which dissolved in MIBK phase. Some experimental parameters, which are important for the whole extraction process, including pH, sample volume, shaking time, amount of the EMPC reagent, amount of MIBK, ionic strength, and type of back-extractant were investigated. The recovery for Zn(II) was greater than 95%. The detection limit of the method was found to be 0.2?µg?L ^{? 1} and the relative standard deviation as 6.4%. The concentrations of Zn(II) in the certified reference materials (LGC6019 river water and NIST-1547 peach leaves) by the presented method were in good agreement with the certified values. The proposed method was succesfully applied to the determination of zinc in some natural waters, rice, hair, soil, and tea samples.     

Determination of trace chromium(VI) by an inhibition-based enzyme biosensor incorporating an electropolymerized aniline membrane and ferrocene as electron transfer mediator

A novel inhibition-based glucose oxidase (GOx) biosensor for environmental chromium(VI) detection is described. An electropolymerized aniline membrane has been prepared on a platinum electrode containing ferrocene as electron transfer mediator, on which GOx is cross-linked by glutaraldehyde. The mechanism of the redox reaction on the electrode and the performance of the sensor are studied. The sensor's response to glucose decreases when it is inhibited by chromium(VI), with a lower detection limit of 0.49?µg?L^?1, and the linear response range is divided into two parts, one of which is 0.49–95.73?µg?L^?1 and the other is 95.73?µg^?1 to8.05?mg?L^?1. The enzyme membrane is shown to be completely reactivated after inhibition, retaining 90% activity over more than forty days. Interference to chromium(VI) determination from lead(II), copper(II), cadmium(II), chromium(III), cobalt(II), tin(II) and nickel(II) is found to be minimal, while high concentrations of mercury(II) and silver(I) may interfere with the determination of trace chromium(VI). The sensor has been used for chromium(VI) determination in soil samples with good results.     

Speciation analysis of chromium in water samples using nanometer zirconium dioxide and direct ultrasonic slurry sampling with electrothermal atomic absorption spectrometry

A new analytical procedure for the determination of chromium Cr(III) and Cr(VI) species in different water samples was developed. The method involves solid-phase extraction (SPE), direct ultrasonic slurry sampling (DUSSS), and subsequent electrothermal atomic absorption spectrometry (ETAAS). The nanometer-sized zirconium dioxide (ZrO₂) was used as the sorbent material. The optimal conditions for the proposed solid phase extraction were: 50 mg ZrO₂, 20 min extraction time, pH 2.5 for Cr(VI) and pH 8.0 for Cr(III) and for the ETAAS measurement: 1500°C pyrolysis and 2300°C atomisation temperatures, 1.5 g L^?1 Mg(NO₃)₂ as matrix modifier. The samples were sonicated directly in the autosampler cup, using an ultrasonic probe at 20% power setting for 10 seconds prior to injection into the graphite tube with ?vov platform. In this way, all drawbacks due to the elution procedure were eliminated. The limit of detection and limit of quantification for Cr(III) obtained under optimised conditions were 0.48 μg L^?1, and 1.61 μg L^?1, respectively, and for Cr(VI) 0.27 μg L^?1 and 0.90 μg L^?1. The pre-concentration factors attained for both the species were 25. The effects of alkaline, alkaline earth and some metal ions and some anions were also examined. The relative standard deviation estimated from six replicate measurements at a concentration of 0.4 μg L^?1 for both Cr(III) and Cr(VI) with a pre-concentration factor of 25 was 2.96% and 4.06%, respectively. The accuracy of the method was confirmed by analysis of the standard reference material SRM 1643e “Trace Elements in Water?. The proposed technique is simple, sensitive, environmentally friendly, and the risk of contamination is low. Hence, it was successfully applied to spiked synthetic and real water samples with recoveries ranging from 91.3% to 109.2%     

Solid phase extraction of hexavalent chromium by Mannich base polymer wrapped flower-like layered double hydroxide

In the present work, synthesis of polymer wrapped flower-like MgAl layered double hydroxide was done through condensation of 1,4 phenylenediamine and resorcinol by p-formaldehyde. The nanocomposite was characterised with X-ray diffraction analysis, fourier transform infrared spectroscopy, thermogravimetric analysis and field emission scanning electron microscopy techniques and employed for effective adsorption of Cr(VI) from aqueous solution prior to flame atomic absorption spectrometer determination. Optimum level of effective parameters (pH, reaction time and adsorbent dosage) and their interaction was determined by response surface methodology. To investigate applicability of method for trace heavy metal adsorption, the method was employed for preconcentration of Cr(VI) in water samples. At the optimum conditions, pH = 4.5, shaking time of 15 min and adsorbent dosage of 20 mg, analytical performance of the method was evaluated and results showed that calibration curve is linear in the concentration range of 2–100 μg L^?1. Moreover, limit of detection was 0.22 µg L^?1 and relative standard deviation of six replicate experiments at initial concentration of 0.1 mg L^?1 was 3.3%. Isotherm study showed that Freundlich model can better describe adsorption behaviour as well as the sorbent showed the adsorption capacity of 62.5 mg g^?1. Moreover, thermodynamic study revealed that chromate adsorption was spontaneous and followed the endothermic path. Regeneration of sorbent was performed using 1.0 mol L^?1 of NaOH solution. The sorbent was employed for Cr(VI) determination from food additives and seawater samples.     

Synthesis of Mesoporous Lanthanum Phosphate and Its Use as a Novel Sorbent

Mesoporous lanthanum phosphate was synthesized by supramolecular self-assembly of cetyltrimethylammo-nium bromide and lanthanum nitrate following digestion in phosphoric acid.TGA-DTA,XRD and SEM were em-ployed to study the uncalcined and calcined materials.Sorption behavior of Cr(Ⅲ),Mn(Ⅱ),Fe(Ⅲ),Co(Ⅱ),Ni(Ⅱ),Cu(Ⅱ),Zn(Ⅱ),Cd(Ⅱ),Ba(Ⅱ),Hg(Ⅱ)and Pb(Ⅱ)cations was studied on such materials in water,3 mol·L~(-1)ammonia,0.01 mol.L~(-1)potassium ferrocyanide and 0.01 mol·L~(-1)potassium ferricyanide solutions.     

Solid phase extraction and diffusive gradients in thin films techniques for determination of total and labile concentrations of Cd(II), Cu(II), Ni(II) and Pb(II) in Black Sea water

Total dissolved and labile concentrations of Cd(II), Cu(II), Ni(II) and Pb(II) were determined at six locations of the Bourgas Gulf of the Bulgarian Black Sea coast. Solid phase extraction procedure based on monodisperse, submicrometer silica spheres modified with 3-aminopropyltrimethoxysilane followed by the electrothermal atomic absorption spectrometry (ETAAS) was developed and applied to quantify the total dissolved metal concentrations in sea water. Quantitative sorption of Cd, Cu, Ni and Pb was achieved in the pH range 7.5–8, for 30?min, adsorbed elements were easily eluted with 2?mL 2?mol?L^?1 HNO₃. Since the optimal pH for quantitative sorption coincides with typical pH of Black Sea water (7.9–8.2), on-site pre-concentration of the analytes without any additional treatment was possible. Detection limits achieved for total dissolved metal quantification were: Cd 0.002?µg?L^?1, Cu 0.005?µg?L^?1, Ni 0.03?µg?L^?1, Pb 0.02?µg?L^?1 and relative standard deviations varied from 5–13% for all studied elements (for typical Cd, Cu, Ni and Pb concentrations in Black Sea water). Open pore diffusive gradients in thin films (DGT) technique was employed for in-situ sampling and pre-concentration of the sea water and in combination with ETAAS was used to determine the proportion of dynamic (mobile and kinetically labile) species of Cd(II), Cu(II), Ni(II) and Pb(II) in the sea water. Obtained results showed strong complexation for Cu and Pb with sea water dissolved organic matter. The ratios between DGT-labile and total dissolved concentrations found for Cu(II) and Pb(II) were in the range 0.2–0.4. For Cd and Ni, these ratios varied from 0.6 to 0.8, suggesting higher degree of free and kinetically labile species of these metals in sea water.     

Preconcentration and Determination of Chromium Species Using Octadecyl Silica Membrane Disks and Flame Atomic Absorption Spectrometry

A novel and selective method for the fast determination of trace amounts of chromium species in water samples has been developed. The procedure is based on the selective formation of chromium diethyldithiocarbamate complexes at different pH in the presence of Mn(II) as an enhancement agent of chromium signals followed by elution with organic eluents and determination by atomic flame absorption spectrometry. The maximum capacity of the employed disks was found to be (396±3) µg and (376±2) µg for Cr(III) and Cr(VI), respectively. The detection limit of the proposed method is 49 and 43 ng·L^?1 for Cr(III) and Cr(VI), respectively. The proposed method was successfully applied for determination of chromium species Cr(III) and Cr(VI) in different water samples.     

Novel Imprinted Polymer for the Preconcentration of Cadmium with Determination by Inductively Coupled Plasma Mass Spectrometry

A novel Cd(II)-imprinted polymer was prepared with chemical immobilization using N-methacryloyl-L-Histidine as a vinylated chelating agent for online solid-phase extraction of Cd(II) for determination by inductively coupled plasma mass spectrometry. The Cd(II)–monomer complex was synthesized and copolymerized through bulk polymerization method in the presence of ethyleneglycoldimethacrylate cross-linker. The resulting polymer was leached with 1.0?mol?L^?1 HNO₃ to generate the cavities in the polymer for Cd(II) ions. The experimental conditions, including load pH, solution flow rate, and eluent concentration for effective sorption of Cd(II), were optimized using a minicolumn of the imprinted polymer. A volume of 5.0?mL sample 5?µg?L^?1 Cd(II) solution at pH 6.5 was loaded on the column at 2.0?mL?min^?1 using a sequential injection system followed by elution with 1.0?mL of 0.75?mol?L^?1 HNO₃. The relative selectivity coefficients of the imprinted polymer for Cd(II) were 38.5, 3.5, 3.0, 2.5, and 6.0 in the presence of Cu(II), Ni(II), Zn(II), Co(II), and Pb(II), respectively. Computational calculations revealed that the selectivity of the imprinted polymer was mediated by the stability of Cd(II)–N-methacryloyl-L-Histidine complex which was more stable than commonly used monomers including 4-vinyl pyridine, methacrylic acid, and vinylimidazole. The detection limit and relative standard deviation were 0.004?µg?L^?1 and 3.2%, respectively. The method was validated by the analysis of seawater certified reference material (CASS-4) and successfully used for the determination of Cd(II) in coastal seawater and estuarine water.