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This work aims to modify zein, a corn protein, to be a biocompatible adsorbent for the removal of As(V) from water. This adsorbent was prepared by the incorporation of iron(III) chloride into 50% (w/v) of zein in ethanol and water (70:30 (v/v)) and dropping into cold water (5 °C) to form adsorbent beads. In the batch operation, various parameters, i.e., pH of solution, iron loading concentration, competing ions and adsorption time, were studied. Under the optimum conditions, the As(V) adsorption appeared to follow the Langmuir isotherm model with the maximum adsorption capacity of 1.95 mg/g.

Due to similar properties in the electroanalysis of tin (Sn(II)) and lead (Pb(II)), the voltammograms of tin and lead overlap and it is difficult to simultaneously determine these two metals. Herein, we develop a simple fabricated sensor based on a bismuth nanoparticle-modified screen-printed graphene electrode (BiNP/SPGE) on a paper-based analytical device (PAD) for the simultaneous determination of Sn(II) and Pb(II) and combine it with a portable potentiostat. To overcome crossing interference, the use of hexadecyltrimethylammonium bromide (CTAB) can provide improved separation and enhanced sensitivity for Sn(II) and Pb(II) detection in oxalic acid as a supporting electrolyte while using square-wave anodic stripping voltammetry. Under optimal conditions, the linear range of both metals was determined to be 10–250 ng mL−1, and the calculated limit of detection (3SD/slope) was 0.26 ng mL−1 and 0.44 ng mL−1 for Sn(II) and Pb(II), respectively. This sensor was also applied to simultaneously determine Sn(II) and Pb(II) in canned food samples. The results obtained from the portable potentiostat were similar to the results obtained by a standard method. Therefore, the proposed device can be further improved for the realization of a rapid on-site detector for Sn(II) and Pb(II) detection in real samples.

The removal of anti-inflammatory drugs ibuprofen, diclofenac, and naproxen from aqueous solutions was investigated by a novel adsorbent which was prepared by the assembly of polymeric chitosan onto waste tire crumb rubber. The modified adsorbent demonstrated a capacity of 70.0, 17.7 and 2.3 mg/g for ibuprofen, diclofenac and naproxen, respectively. Various parameters affecting the removal efficiency of these drugs were optimized. pH 6 is optimal for the simultaneous removal of all three drugs. The adsorption of each of these anti-inflammatory drugs was found to follow the Freundlich isotherm model. In all, the chitosan-modified rubber has been demonstrated as an effective and economical adsorbent for removal of these compounds from water.

A novel colorimetric assay based on silver nanoplates (AgNPls) for detecting nickel ions (Ni(2+)) has been developed. Glutathione (GSH) and l-cysteine (Cys) were used to modify the AgNPls surface, exhibiting extremely high selectivity towards Ni(2+) over other metal ions under specific conditions. Upon addition of Ni(2+) to the modified AgNPls solution, a distinctive color change can be clearly observed by naked eyes as a result of the aggregation of AgNPls induced by the binding between Ni(2+) and the modified ligands. To verify a complete self-assembly of the GSH and Cys onto AgNPls surface, the modified AgNPls were characterized using Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-vis) and transmission electron microscopy (TEM), respectively. Moreover, various parameters affecting the Ni(2+) quantification including the modifier ratio, pH, reaction time, and interferences were investigated. With UV-vis spectrophotometric measurement under optimal conditions, a quantitative linearity was established in the range of 10-150 ppb (R(2)=0.9971) with the detection limit of 7.02 ppb or 120 nM (S/N=3). In addition, the developed sensor was applied to the determination of Ni(2+) in waste samples from a jewelry factory and a car manufacturer with satisfactory results. Overall, this alternative approach presents a simple, rapid, sensitive and selective detection of Ni(2+).

A spraying method with lacquer was developed for the fabrication of paper-based devices. A patterned iron mask was initially placed on a filter paper and held tightly attached by a magnetic plate placed on the opposite side. After that, acrylic lacquer was sprayed on the filter paper to create a hydrophobic area while the hydrophilic area was protected with the iron mask. The optimal conditions for the fabrication of this device were studied including lacquer type and particle retention efficiency of filter paper. Gloss spray lacquer and filter paper No. 4 were chosen as optimal lacquer type and particle retention efficiency of filter paper, respectively. To evaluate its efficiency, the paper-based devices were used to determine nickel using electrochemical detection. Cu-enhancer solution was employed to increase sensitivity of nickel determination with the optimal concentration of 4.5 ppm. Under the optimal conditions, linear range was observed in the range of 1-50 ppm with a coefficient of determination of 0.9971. The limit of detection (LOD) and the limit of quantitation (LOQ) were found to be 0.5 and 1.97 ppm, respectively. Moreover, these paper-based devices coupled with electrochemical detection were applied to determine nickel in waste water of a jewelry factory and compared to those obtained with inductively coupled plasma optical emission spectrometry (ICP-OES). The results indicated that there were no significant variations between this proposed method (4.15±0.043 ppm) and the ICP-OES method (4.06±0.013 ppm). Therefore, this spraying method was found to be an excellent alternative for the fabrication of paper-based devices due to its ease of use, affordability and simplicity.

Polystyrene-divinylbenzene resin (PS-DVB) was functionalized with a benzothiazole group. PS-DVB with amino group was initially prepared by nitration and reduction reactions and subsequently treated with ethyl 2-benzothiazolylacetate (BA) to obtain the chelating resin with an amide linkage (BA-PS-DVB). Meanwhile, the amino-PS-DVB was diazotized and coupled with BA to obtain the chelating resin with an azo linkage (azo-BA-PS-DVB). The resins were characterized by elemental analysis and infrared spectroscopy and evaluated for their extraction of Cd(II), Cu(II) and Pb(II) ions in water before their determinations by flame atomic absorption spectrometry (FAAS). Extraction conditions were optimized for batch method such as the pH of the solution, the extraction time and the adsorption isotherm. The optimum pH for the extraction of Cd(II), Cu(II) and Pb(II) are 8.0, 7.0 and 6.0, respectively, while the equilibrium time of all ions was reached within 10–20 min. The adsorption behavior of all the metal ions followed the Langmuir adsorption isotherm. In the column method, the optimum flow rates of metal sorption onto BA-PS-DVB and azo-BA-PS-DVB columns were 2.5 and 4.0 mL min− 1. Metal ions sorbed onto columns were eluted by 0.5 to 2.0 M HNO3. The preconcentration factors of Cd(II) and Cu(II) on azo-BA-PS-DVB and Cu(II) on BA-PS-DVB were 50, 50, and 20, respectively. The present column method gave acceptable validation results: 71.2 and 74.0% recovery for Cd(II) and Cu(II) and an overall relative standard deviation (R.S.D) less than 10% (n = 15). The proposed method was applicable for determining Cu(II) in drinking water.

The electrochemical analysis of tetracyclines was investigated using nickel-implanted boron-doped diamond thin film electrode (Ni-DIA) by cyclic voltammetry and high performance liquid chromatographic with amperometry. Cyclic voltammetry was used to study the electrochemical oxidation of tetracyclines. Comparison experiments were carried out utilizing as-deposited BDD and glassy carbon electrodes. Ni-DIA electrode provided well-resolved oxidative irreversible cyclic voltammograms and the highest current signals among the electrode studied. High performance liquid chromatography (HPLC) with amperometric detection was also studied. The chromatography was performed using a commercially available Inertsil C18 column, with the mobile phase being: 80% phosphate buffer (pH 2.5)–20% acetonitrile and detected at 1.55 V. The methods were validated over the concentration range 0.05–100 ppm with the overall average recoveries from 83.3 to 102.5% and R.S.D. of less than 10%. The proposed method was further applied to analyse shrimp samples.

A general method for identifying the origin of a particular polyatomic ion is described. Based on a postulated dissociation reaction, measured ion signal ratios (e.g. Ar 2 + /Ar + ) are combined with mass bias corrections and estimates of the density of the neutral product (usually Ar, O or H atoms) to determine a gas kinetic temperature T gas . The temperature can also be measured by the reduction in pressure when the ICP is sampled (compared to room temperature argon), or by other means. Dissociation energies and spectroscopic constants for the ions are necessary. For the particular instrument used, some of the findings of this study are: (a) ArO + and ArN + can be either dissociated (if the plasma potential is high) or created (if the plasma potential is low) by collisions between the sampler and skimmer; (b) the strongly-bound oxide ions O 2 + and MO + for the rare earths are observed at levels consistent with T gas ∼5300 K in a ‘hot’ plasma, but ClO + is formed in excess; and (c) the abundances of most other polyatomic ions like H 2 O + and ArH + correspond to higher densities than would be expected in the ICP itself.

The torch wall is cooled largely by air passing through a cooling jacket added to the outside of a Fassel torch. The plasma is viewed axially through a cooled cone interface centered on the axial channel. The outer argon gas flow can be reduced to 7 l min −1 with no compromise in performance or torch lifetime. The plasma exhibits the same ‘robustness index’ and interference effects from Na as the conventional, high-flow ICP supplied with the particular spectrometer used. Detection limits (DL) for lines at ∼200 nm are poorer by approximately a factor of two, while those for lines at ∼400 nm are actually better than values typically seen for the same lines by axial viewing of a conventional, high-flow ICP.

A low-flow torch specifically designed for inductively coupled plasma mass spectrometry (ICP-MS) was developed and evaluated. The outside of the torch is cooled externally by pressurized air flowing at ∼70 l min−1 through a fourth tube sealed onto the usual ‘outer’ tube of a standard minitorch. This external air flow merely cools the outer tube of the torch and does not enter the plasma. Although plasmas can be sustained at operating power as low as 400 W with a 2 l min−1 outer Ar flow, somewhat higher power and flows are advisable. A stable and analytically useful plasma can be obtained at 850 W with an outer Ar flow rate of only 4 l min−1. Under optimum operating conditions, the externally air-cooled plasma produces comparable sensitivities, M2+/M+ signal ratios, matrix effects and other analytical figures of merit as those produced by a conventional torch while using much less argon. MO+/M+ signal ratios are slightly higher with the externally cooled torch.