High-sensitivity determination of available cobalt in soil using laser-induced breakdown spectroscopy assisted with laser-induced fluorescence.

Conventional laser-induced breakdown spectroscopy could not conduct high-sensitivity determination of available cobalt due to spectral interference and weak spectral intensity. To improve the poor detection sensitivity of available cobalt in soil, available cobalt was extracted from soil and prepared. Laser-induced breakdown spectroscopy assisted with laser-induced fluorescence was introduced to excite and detect the cobalt element. The results showed that coefficients of the calibration curve for the available cobalt element could reach 0.9991, and the limits of detection could reach 0.005 mg/kg in soil under optimized conditions, which were all much better than conventional LIBS and reach the international minimum detection standards. This work provides a possible approach for detecting available trace elements in soil.

The distribution of high-quality internal standard lines and their selection method based on the Q-value in portable laser-induced breakdown spectroscopy.

Internal standard lines play a crucial role in the univariate quantitative analysis in portable laser-induced breakdown spectroscopy (LIBS) technology. To overcome the uncertainty of the conventional internal standard method, the distribution principles of high-quality internal standard lines were studied and revealed at the macro and micro levels, and an automatic internal standard line selection method based on the Q-value was proposed. Using this method, in the quantitative analysis of Si in low-alloy steel samples, the average relative error of cross-validation (ARECV), root mean squared error of cross-validation (RMSECV), and the limit of detection (LoD) were decreased significantly from 27.42%, 0.041 wt%, and 1060 µg g-1 to 18.65%, 0.026 wt%, and 680 µg g-1, respectively. The quantitative analysis results of Cr, Cu and Ni showed that it has excellent generalization ability. The results indicate that this method can screen out the optimal internal standard lines efficiently and accurately, which provides a new approach to improve the performance of univariate quantitative analysis in portable LIBS.

Determination of fluorine content in rocks using laser-induced breakdown spectroscopy assisted with radical synthesis.

In the atmosphere, fluorine element in rocks is hard to detect using fluorine atomic emission spectrum in laser-induced breakdown spectroscopy. In this study, a novel radical synthesis method based on laser ablation was proposed, by which strontium-fluorine (SrF) radical spectrum was collected to quantify fluorine element in rocks instead of fluorine atom spectrum. A pure strontium carbonate was placed orthogonally to the sample, and ablated by an additional laser to provide sufficient strontium atoms for promoting SrF radical formation. The fluorine content in rocks was sensitively and accurately determined by SrF radical emission signal. The coefficient of determination, average relative standard deviation, root mean square error, limit of detection, and limit of qualification were 0.996, 4.68%, 0.0068 wt%, 6.36 µg g-1, and 21.2 µg g-1, respectively. This work proved that this novel method provides a new way to promote radical synthesis and has considerable potential for detecting fluorine in rocks in geological exploration.

Sensitive analysis of fluorine and chlorine elements in water solution using laser-induced breakdown spectroscopy assisted with molecular synthesis.

Fluorine and chlorine are key elements to affecting water quality, but they are hard to be determined by conventional laser-induced breakdown spectroscopy (LIBS). To achieve high sensitivity detection of them, the CaF and CaCl molecules were synthesized by combining calcium in calcite and F and Cl in sample. The temporal characteristics of CaF and CaCl molecular emissions were investigated. It shows that molecular emission of CaF and CaCl has a longer lifetime and high spectral intensity than that of their atomic emissions. Such unique feature of molecular emission inspired us to use it for high sensitivity analysis of Cl and F elements in water. The results show that these two elements can be sensitively and accurately detected using LIBS assisted with molecular emission. The limits of detections (LoDs) were 0.38 mg/L and 1.03 mg/L for F and Cl elements, respectively, and the limit of quantitation (LoQ) was 3.404 mg/L to 20.569 mg/L for fluorine elements and 9.986 mg/L to 39.757 mg/L for fluorine. These detection limits can meet the World Health Organization's detection requirements for F and Cl elements in water. The results show that LIBS assisted with molecular synthesis has a huge potential in water quality monitoring.

Coupling of thermophilic biofilm-based systems and ozonation for enhanced organics removal from high-temperature pulping wastewater: Performance, microbial communities, and pollutant transformations.

This study focused on the establishment of thermophilic biofilm-based systems (TBSs) coupled with ozonation for treatment of high-temperature pulping wastewater. The effects of the inoculum, sludge growth mode, and temperature were investigated. These factors played roles in the organics removal performance and microbial communities of pulping wastewater treatment systems. At 50 °C, the TBS inoculated with optimal inoculum achieved 59.12% and 37.96% reductions in COD and chromaticity, which were superior to the reductions achieved by other systems. In this TBS, thermophilic lignocellulolytic microorganisms (Chloroflexus, Meiothermus, norank_f_Caldilineaceae, and Roseiflexus) and carbohydrate-fermenting bacteria (norank_f_Anaerolineaceae) were predominant. Their relative abundances were 25.55% and 10.42%, respectively. For enhanced removal of COD and chromaticity, an integrated system consisting of a primary TBS, ozonation, and a secondary TBS was proposed. The total COD and chromaticity removal efficiencies increased to 90.48% and 87.89%, respectively. BOD5/COD increased from 0.20 to 0.40, and shifts of lignin-like and humic acid-like substances were observed during ozonation with the primary TBS effluent.

Sulfur determination in laser-induced breakdown spectroscopy combined with resonance Raman scattering.

Sulfur is an essential element in industry, but it is difficult to be detected by laser-induced breakdown spectroscopy (LIBS). In this work, the disulfide radical Raman scattering was observed in sulfur plasma by combining LIBS with resonance Raman scattering (LIBS-RRS). Sulfur has been ablated by a focused laser beam to generate plasma, in which some sulfur atoms were combined to form disulfide radicals. The disulfide radical resonance Raman was excited by a 306.4 nm wavelength laser and observed at 710 and 1420 cm-1 Raman shift. Using different contents of sulfur mixed with alumina (Al2O3) powder, both LIBS and LIBS-RRS calibrations were obtained at the same ablation laser energy. The calibration curve of sulfur atomic emission S I 921.28 nm was set up, and the linear coefficient (R2) was 0.285 and the detection limit (LoD) was 13.092 wt %. While the R2 was 0.966 and LoD was 0.118 wt % for S2 710 cm-1 in LIBS-RRS. The results indicate that disulfide radical Raman scattering by LIBS-RRS is promising for the determination of sulfur content and the diagnosis of molecular evolution in plasma.

Lead of detection in rhododendron leaves using laser-induced breakdown spectroscopy assisted by laser-induced fluorescence.

Laser-induced breakdown spectroscopy assisted by laser-induced fluorescence (LIBS-LIF) was applied to determine lead (Pb) in rhododendron leaves. Rhododendron leaves are essential types of herbal materials. Rapid detection of lead in rhododendron leaves is urgent for drug monitoring. In this paper, the powder method and solid-liquid-solid transformation (SLST) method were employed as sample preparation. The results showed that the signal of the Pb I 405.78 nm line was substantially enhanced. For samples A, B and C, the LoD values of 0.054 mg/kg, 0.059 mg/kg, 0.062 mg/kg were achieved with R2 values of 0.997, 0.996, 0.997 via the SLST approach, whose sensitivity and accuracy was slightly higher compared to the powder method. The RMSECV values of both methods were minimal, ranging from 0.538 to 2.117 mg/kg. Lead content detected by LIBS-LIF in the three samples was between 1.5 and 2.8 mg/kg. The results of lead were validated by inductively coupled plasma optical emission spectrometry (ICP-OES). This research provided us with new technology for the rapid and accurate determination of Pb element in rhododendron leaves.

An ionic liquid-functionalized amphiphilic Janus material as a Pickering interfacial catalyst for asymmetric sulfoxidation in water.

Ionic liquid-functionalized amphiphilic Janus chiral salen TiIV catalysts were prepared by partial hydrophobic modification of silica with a chiral salen TiIV complex through an imidazolium ionic liquid (IL) linker. By optimizing their hydrophobic/hydrophilic balance, the IL-functionalized JNP materials exhibited excellent interfacial activity, significantly accelerating asymmetric sulfoxidation in water through the formation of stable Pickering emulsions. Moreover, catalyst recovery was readily achieved using centrifugation.

Determination of chlorine with radical emission using laser-induced breakdown spectroscopy coupled with partial least square regression.

Chlorine is a crucial element which may cause the corrosion of reinforced concrete. However, the strongest chlorine atom/ion emission lines are in the UV region and the ground state atom is hard to excite by conventional single-pulsed laser-induced breakdown spectroscopy (SP-LIBS). Radical emission is a feasible alternative to atom/ion emission when detecting chlorine concentration. Here, Cl atomic emission and calcium chloride (CaCl) radicals were detected in SP-LIBS, the calibrations of both emissions were compared. To further improve the accuracy, partial least square regression (PLSR) was adopted to establish the calibrations. The results showed that CaCl radical signal is stronger than Cl atomic signal with low energy SP-LIBS in open air, achieving a LoD (limit of detection) of 0.0404 wt%. Meanwhile, CaCl calibration had a better accuracy with coefficient of determination (R2) and root mean square error of cross validation (RMSECV) of 0.9930 and 0.2016 wt% with the help of PLSR. In conclusion, this work provided a potential approach for Chlorine determination in industry.

Titanium(iv)-folded single-chain polymeric nanoparticles as artificial metalloenzyme for asymmetric sulfoxidation in water.

Intrachain TiIV-oxazoline complexation together with hydrophobic interaction triggered the self-folding of an oxazoline-containing single polymeric chain in water. The formed TiIV-folded single-chain polymeric nanoparticles (SCPNs) acted as metalloenzyme-mimetic catalysts in asymmetric sulfoxidation in water owing to their organized, compartmentalized structure, effective site isolation, and also secondary coordination sphere provided by a copolymer backbone. In addition, they also could be facilely recovered for reuse by simple thermo-controlled separation.