Optimization of chemical and instrumental parameters in hydride generation laser-induced breakdown spectrometry for the determination of arsenic, antimony, lead and germanium in aqueous samples

Highly sensitive analysis of trace germanium derived from the efficient electrosynthesis and spectral introduction of GeH4 on foam electrode

BACKGROUND

The electrochemical hydride generation technology, which uses electrolysis instead of chemical reagents to generate reducing species to achieve gaseous transformation and sample introduction of the tested elements, has received widespread attention in the field of atomic spectroscopy due to its simple, economical, and green characteristics. However, limited by the effective area of the electrode, the introduction efficiency and spectral signal of most elements (e.g., germanium) in practical applications are lower than traditional chemical hydride generation.

RESULTS

In this paper, an efficient electrochemical hydride generation (EHG) method based on metal foam electrode for μg L-1 level germanium was constructed. Systematic electrochemical and spectral tests showed that the low charge transfer resistance and the high electrochemical activity of nickel-based foam electrodes jointly promoted the efficient electroreduction of Ge(IV). Besides, the porous network structure of the metal foam material improves the contact probability of reactants while reducing the gas-evolution effect caused by bubble accumulation. Interestingly, adequate reaction sites are crucial for the conversion of germanium, but large foam electrodes are not always compatible with analytical performance. After coupling atomic fluorescence spectroscopy, this new electrolysis method has been proven to be suitable for efficient conversion and quantitative detection of Ge over a wide concentration range (5-150 μg L-1).

SIGNIFICANCE

Our proposal to improve the electrosynthesis efficiency of germanane (GeH4) by using metal foam electrode is extremely effective for the detection of trace or ultra-trace germanium. The exploration of electrode material, structure, and especially effective area will also provide ideas for the establishment of highly sensitive analysis methods in the future.

Simultaneous Determination of As, Bi, Sb, Se, Te, Hg, Pb and Sn by Small-Sized Electrothermal Vaporization Capacitively Coupled Plasma Microtorch Optical Emission Spectrometry Using Direct Liquid Microsampling

The simultaneous determination of chemical vapor-generating elements involving derivatization is difficult even by inductively coupled plasma optical emission spectrometry or mass spectrometry. This study proposes a new direct liquid microsampling method for the simultaneous determination of As, Bi, Se, Te, Hg, Pb, and Sn, using a fully miniaturized set-up based on electrothermal vaporization capacitively coupled plasma microtorch optical emission spectrometry. The method is cost-effective, free from non-spectral interference, and easy to run by avoiding derivatization. The method involves the vaporization of analytes from the 10 µL sample and recording of episodic spectra generated in low-power (15 W) and low-Ar consumption (150 mL min⁻¹) plasma microtorch interfaced with low-resolution microspectrometers. Selective vaporization at 1300 °C ensured the avoidance of non-spectral effects and allowed the use of external calibration. Several spectral lines for each element even in the range 180–210 nm could be selected. Generally, this spectral range is examined with large-scale instrumentation. Even in the absence of derivatization, the obtained detection limits were low (0.02–0.75 mg kg⁻¹) and allowed analysis of environmental samples, such as cave and river sediments. The recovery was in the range of 86–116%, and the accuracy was better than 10%. The method is of general interest and could be implemented on any miniaturized or classical laboratory spectrometric instrumentation.

Determination of antimony in soil using laser-induced breakdown spectroscopy assisted with laser-induced fluorescence

Antimony (Sb) in soil is attracting attention in the research community due to its potential toxicity and carcinogenicity. Traditional methods of detecting Sb lack the ability of rapid and nondigestion analysis, which hinders their development and application. Moreover, it is still a challenge for laser-induced breakdown spectroscopy (LIBS) to detect Sb in soil due to the weak intensities and intense interference of spectral lines. Here, LIBS, assisted with laser-induced fluorescence (LIBS-LIF), was used to selectively enhance the Sb's characteristic spectral lines under optimal parameters. The quantitative analysis performance was notably improved with a determination coefficient (R²) of 0.991, the limit of detection of 0.221 μg/g, and root mean square error of cross validation of 3.592 μg/g. These results demonstrate that LIBS-LIF has the potential to realize the rapid and accurate analysis of Sb in soil.

Arsenic speciation analysis in environmental water, sediment and soil samples by magnetic ionic liquid-based air-assisted liquid–liquid microextraction

This highly efficient separation method combines the advantages of magnetic ionic liquid (MIL) and air-assisted liquid–liquid microextraction (AALLME) for the first time.

Development and validation of a laser-induced breakdown spectroscopic method for ultra-trace determination of Cu, Mn, Cd and Pb metals in aqueous droplets after drying

The present study reports a fast and accurate methodology for laser-induced breakdown spectroscopic, LIBS, analysis of aqueous samples for environmental monitoring purposes. This methodology has two important attributes: one is the use of a 300nm oxide coated silicon wafer substrate (Si+SiO2) for the first time for manual injection of 0.5 microliter aqueous metal solutions, and two is the use of high energy laser pulses focused outside the minimum focus position of a plano convex lens at which relatively large laser beam spot covers the entire droplet area for plasma formation. Optimization of instrumental LIBS parameters like detector delay time, gate width and laser energy has been performed to maximize atomic emission signal of target analytes; Cu, Mn, Cd and Pb. Under the optimal conditions, calibration curves were constructed and enhancements in the LIBS emission signal were obtained compared to the results of similar studies given in the literature. The analytical capability of the LIBS technique in liquid analysis has been improved. Absolute detection limits of 1.3pg Cu, 3.3pg Mn, 79pg Cd and 48pg Pb in 0.5 microliter volume of droplets were obtained from single shot analysis of five sequential droplets. The applicability of the proposed methodology to real water samples was tested on the Certified Reference Material, Trace Metals in Drinking Water, CRM-TMDW and on ICP multi-element standard samples. The accuracy of the method was found at a level of minimum 92% with relative standard deviations of at most 20%. Results suggest that 300nm oxide coated silicon wafer has an excellent potential to be used as a substrate for direct analysis of contaminants in water supplies by LIBS and further research, development and engineering will increase the performance and applicability of the methodology.