A method was developed for inorganic arsenic speciation analysis of water samples by a microsample injection system coupled with inductively coupled plasma mass spectrometry (MIS-ICP-MS) following a validated dispersive liquid–liquid microextraction (DLLME). Prior to DLLME speciation analysis, a simple robust microsample injection system was successfully adapted to ICP-MS. A sampling volume of 90 µL provided almost the same signals as the signals obtained by means of a conventional continuous nebulization sampling system for the ICP-MS instrument. After DLLME, the final solution was injected into nebulizer of ICP-MS using the microsample injection system. Under the optimized conditions, the analyte from only 5.0 mL water sample was concentrated by a factor of 48 with detection limits reaching 0.0031 µg L⁻¹ for arsenic. The calibration curve had a linear range of 0.0084–0.0800 µg L⁻¹ (r ²= 0.999). The relative standard deviations (RSD, n = 6) were <4%. The proposed method was applied to the speciation of inorganic arsenic in various water samples with satisfactory results. The determination of arsenite and total As in river, pond, tap and bottled water samples was acheived by the standard addition method. The recoveries for spiked As(III) and As(V) from understudied water samples were in the range of 95–108%.

A magnetic solid-phase microextraction (SPME) procedure was optimized using Fe₃O₄ nanoparticles (NPs) to preconcentrate and determine cobalt and copper in real samples using microsample injection system-flame atomic absorption spectrometry (MIS-FAAS). Recoveries over 95% for Co(II) and 80% for Cu(II) from 90 mL of sample buffered to pH 4.0 were obtained using 50 mg Fe₃O₄ NPs as the adsorbent and 0.5 mL of 0.5 mol L⁻¹ HNO₃ as the eluent. The extraction time was 10 min. The preconcentration factors for Co(II) and Cu(II) were 180. The detection limits for Co(II) and Cu(II) were 1.2 and 0.9 µg L⁻¹, respectively. The relative uncertainties and relative standard deviations were lower than 5.3% and 2.4%, respectively. The developed method was verified by analyzing TMDW-500 drinking water, NIST 1573a Tomato leaves, and NCS DC 78302 Tibet soil as standard reference materials. The spiking experiments provided recoveries exceeding 95%. The method was applied to determine cobalt and copper in water, soil, tea infusion, and vegetable samples.

A glassy carbon electrode, modified with gold nanoparticles/over-oxidized poly-eriochrome black T film, was fabricated for sensitive determination of As(III) by stripping voltammetry in an acidic medium. The electrode surface properties were characterized by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). The electrode demonstrated a good response towards As(III), with a detection of 0.077 μM and good linearity in the range of 0.1 to 10 μM (R2 = 0.9977). For the determination of As(III), the fabricated electrode was placed in different mineral water samples, acidified with 0.75 M HCl solution, spiked with various concentrations of As(III). Spiked recoveries for mineral water samples were obtained in the range of 100.3%-105.0%. The relative standard deviations were lower than 4.0%.

Nanostructured ZnNiBi-NO₃-Layered Double Hydroxides (LDHs) was synthesised, followed by the simple co-precipitation method using Zn(NO₃)₂.6 H₂O, Ni(NO₃)₂.6 H₂O and Bi(NO₃)₃ as the precursors. Synthesised LDHs was characterised by various techniques such as infrared (IR) spectroscopy, x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray (EDX) and thermal gravimetric analysis (TGA). ZnNiBi-NO₃ LDHs were applied as efficient adsorbents for speciation analysis and preconcentration/separation of Cr(VI)/Cr(III) ions in aqueous samples prior to their trace determinations by microsample injection system-coupled flame atomic absorption spectrometry (MIS-FAAS). ZnNiBi-NO₃ LDHs worked well for speciation and preconcentration/separation of Cr(VI)/Cr(III) ions at an optimum of pH 3.0 and adsorbent dosage of 400 mg. LOD and LOQ of Cr(VI) ions were calculated to be 0.03 and 0.10 μg L⁻¹, respectively with a preconcentration factor of 400. The total saturation capacity of ZnNiBi-NO₃ LDHs for Cr(VI) ions was investigated and found to be 46.0 mg g⁻¹. The mthod was reproduced with RSD ≤1.4% of five replicates. The accuracy of method was evaluated by analysing 10–100 μg L⁻¹ Cr(VI) ions standard solutions, and Cr(VI) ions were recovered ≥96.9% with RSD ≤2.4%. The developed method worked well on wastewater samples.