Wear metals determination in lubricating oils by reversed-phase dispersive liquid-liquid microextraction and microwave induced plasma optical emission spectrometry

A periodic study of the engine oil can allow to anticipate possible breakdowns that the vehicle could have. Due to the complexity of the matrix of this type of samples, a sample treatment prior to analysis is necessary. Analytical chemistry is constantly searching for simpler, more sensitive and environmentally friendly methods. The reverse phase dispersive liquid-liquid microextraction fulfills all the characteristics for the analysis in this type of sample by microwave plasma atomic emission spectrometry (MIP OES). In this work, the extractant solvent used for the microextraction procedure is a diluted acid solution (i.e., 3 M HCl), which is a less-hazardous solvent, in comparison with other solvent used in microextraction procedures. Besides, it is perfectly compatible with MIP OES. The main experimental factors affecting the extraction of Cr, Cu, Mn, Mo, and Ni (i.e., amount of sample, extractant type, acid concentration, extractant volume, extractant time, and centrifugation time and speed) are optimized using a multivariate analysis consisting in two steps: a Plackett-Burman design followed by a circumscribed central composite design. Under optimum conditions (i.e., amount of sample: 5.9 g; extractant volume: 60 µL; extractant type: HCl; acid concentration: 3 M; extraction time: 3 min; centrifugation time: 3 min; centrifugation speed: 2000 rpm), the proposed analytical method is validated and employed to analyze different samples (i.e., used and unused engine oils). Two calibration methods have been evaluated since matrix effects have been observed in the used engine oil sample. These effects have been eliminated using standard addition calibration obtaining RSD and recovery values in the range of 4-12 % and 94-106 % respectively, for samples spiked with 1 µg g-1 of Cr, Cu, Mn, Mo and Ni. Finally, the greenness of this method has been assessed by the Eco-Scale metrics.The authors would like to thank the Spanish Ministry of Science and Innovation (PID2021-126155OB-I00), the Regional Government of Valencia (Spain) (CIPROM/2021/062), and University of Alicante (UAIND21-03C) for the financial support. 15% of this study is financed by the European Union-NextGenerationEU, through the National Recovery and Resilience Plan of the Republic of Bulgaria, project number BG-RRP-2.004-0001-C01. This article is based upon work from the Sample Preparation Study Group and Network, supported by the Division of Analytical Chemistry of the European Chemical Society. Finally, the authors would also like to thank Agilent Technologies Inc. for the loan of the MIP OES spectrometer and Ingeniatrics for the OneNeb® Series 2 provided. This work is part of the PhD. Degree of C. S

Elemental speciation by capillary electrophoresis with inductively coupled plasma spectrometry: A new approach by flow focusing® nebulization

A novel system for Capillary Electrophoresis (CE) and Inductively Coupled Plasma (ICP) sample introduction that incorporates a dedicated Flow-Focusing® based nebulizer as aerosol generation unit is presented, aiming to provide high signal sensitivity and low detection limits for element speciation at short analysis times. To prove its viability, the system prototype constructed has been coupled to an inductively coupled plasma - optical emission spectrometer (ICP-OES) and an inductively coupled plasma - mass spectrometer (ICP-MS) for Cr(III) and Cr(VI) speciation. Separation - nebulization system and operation parameters (i.e., capillary length, nebulizer geometry, carrier flow, carrier ionic strength, separation potential and sample injection volume) have been considered and studied, and the analytical figures of merit obtained for model samples in ICP-MS are presented. The results obtained show that the developed instrumental system permits Cr speciation in less than two minutes with detection limits of 0.1, 0.2 and 0.03 μg/L for Cr(III), Cr(VI) and total Cr, respectively.The authors are grateful to the Spanish Government (project CTQ2008-06730-C02-01), the Valencian Government (project ACOMP/2010/047), the NSF of Bulgaria (project DO 02-07 GAMMA) and the European Commission (EC FP7 24588 BioSupport project) for the financial support

Modified MSIS chamber as novel gas-liquid separator coupled with photochemical vapor generation of trace mercury with MP-AES detection

New hyphenation of continuous flow photochemical vapor generator (PVG) to modified multimode sample introduction system (MSIS) used as gas-liquid separator and microwave plasma atomic emission spectrometry (MP-AES) was proposed for analysis of trace mercury. The widened MSIS bottom inlet contributes to the increase of the Hg0 mass transfer in the gas-liquid separator allowing the mercury determination by MP-AES. After optimizing the PVG reactor conditions and MP-AES instrument parameters a limit of detection (LOD) of 0.25 ppb was obtained for Hg2+. The applicability of the PVG-MSIS-MP-AES method was subsequently demonstrated for trace mercury analysis in two soil CRMs - ERM-CC135a (Contaminated Brickworks soil) and CRM005 (Sewage Amended soil).This study is financed by the European Union-NextGenerationEU, through the National Recovery and Resilience Plan of the Republic of Bulgaria, project № BG-RRP-2.004-0001-C01

Ionic liquids used as a green approach in headspace single drop microextraction and GCMS determination of organotin compounds

Gas chromatography with MS detection was applied for simultaneous determination of six of the most toxic organotin compounds (OTs): monobutyltin, dibutyltin, tributyltin, monophenyltin, diphenyltin, triphenyltin. Headspace single drop microextraction (HS-SDME) in Ionic liquids (ILs) was proposed as Green alternative to the traditional one. Three different ILs ([C8MIM][PF6]; [C6MIM][PF6]) and [C4MIM][PF6]) were evaluated as a collector phase. The first one was found as the most appropriate for a group microextraction of the tested OTs. Analytes were evaporated from the IL microdrop by means of thermal desorption. ILs possess some advantages as an extraction phase in comparison with traditionally used organic solvents. They are more stable during the analytical process and are considered as environmentally friendly compounds. Moreover HS-SDME procedure was performed in a single drop of only 5μl IL. The time needed for the extraction was proved to be only 20 min. Therefore the proposed method could be related to the Green chemistry methods.The current study has been financially supported by: NSF of Bulgaria (Project DO 02-70 (GAMA)); EC 7FP Project 245588 (BioSupport); MICINN of Spain (Project CTQ2008-06730-C02-01) and Regional Government of Valencia (Project ACOMP2010/047). LG thanks Erasmus program and Ministry of Education for her fellowship. IPR also thanks “Caja de Ahorros del Mediterraneo (CAM)” for his Ph.D fellowship

MSIS-МP-АЕS determination of As and Sb in complex matrices by magnetic nanoparticles-assisted hydride generation

The advantages of the microwave plasma atomic emission spectrometry (MP-AES) for hydride generation (HG) by means of modified Multi Mode Sample Introduction System (MSIS®) have been revealed for analysis of As and Sb in complex real samples. Two main outcomes have been achieved: (i) reliable analysis and higher tolerability to less diluted matrices and (ii) a multifold reduction in the methodological limits of detection (MLOD). For the first time in real samples analysis the HG is assisted by silica-coated magnetic nanoparticles (MNPs) (∼2 mg mL−1 MnFe2O4@SiO2) added to the hydrogenation reagent stream (1.5% NaBH4). This innovative approach provides smooth hydrides generation from problematic matrices, better gas–liquid separation and steady gas transport from the MSIS chamber. The effect is due to the elimination of NaBH4 delivery interruptions, the foam suppression in the reactor and levelling the carbon amount carried to the MP. The used inert MNPs could be collected from the drain with a permanent magnet and appear to be recyclable and reusable without memory effect or efficiency loss. The achieved benefits are demonstrated in the determination of As and Sb in three types of complex matrices: industrial electrolyte with high dissolved solids content, human urine prone to intensive foam creation, and sparkling mineral water releasing CO2.The work was supported by NSF of Bulgaria, Project DN19/9 2017–2021 (INISA)

Atmospheric pollution assessment with mosses in Western Rhodopes, Bulgaria

The moss analysis technique was applied to monitor 10 heavy metals and toxic elements deposition. Our study was the first attempt to assess spatial patterns in a border mountain region (area 8732 km2) with a low population density and high proportion of protected territories. The obtained results did not correlate to the results from areas with low air pollution and could be linked to the impact of old and open mines

Serum selenium concentration in patients with autoimmune thyroid disease

Abstract Introduction: Selenium (Se) is one of the environmental factors with an essential role in the pathogenesis of autoimmune thyroid disease (ATD). Scarce data is available for the selenium status of the Bulgarian population especially for patients with thyroid disorders. Aim: To compare the serum selenium (s-Se) concentrations in patients with ATD and healthy controls from Bulgarian population. Materials and methods: The s-Se concentrations were measured in 105 patients newly diagnosed or untreated for the previous 6 months with ATD (mean age 44±13 years). The patients were divided into three groups: euthyroid autoimmune thyroiditis (AIT) (n=31), hypothyroid AIT (n=33), and hyperthyroid patients with AIT or Graves’ disease (GD) (n=41). The results were compared to s-Se concentrations in 40 age- and sex-matched healthy controls. Determination of s-Se was carried out by inductively coupled plasma mass spectrometry (ICP-MS) after microwave-assisted acid mineralization of the serum samples. Results: The s-Se concentrations in patients with hyperthyroidism were significantly lower than those in the control group (hyperthyroidism: 69±15.0 µg/L vs. controls: 84±13 µg/L, p<0.001). There was no significant difference in the s-Se concentrations between euthyroid and hypothyroid participants with AIT and healthy controls. The s-Se concentrations in our control individuals were within the range of 53-137 µg/L, reported in literature data on mean serum and plasma levels of European healthy adults. Conclusions: The mean s-Se concentrations observed in all groups were below or close to the cutoff value of 80 µg/L, considered optimal for the activity of the Se-dependent antioxidant systems

Practical Examples on Traceability, Measurement Uncertainty and Validation in Chemistry, volume 1

Case studies on traceability, measurement uncertainty and validation for measurements of gold in gold alloys, calcium in serum, radium in water, polar pesticides in food ammonium in water are presented in this report. Additionally, the idea and structure of the TrainMiC examples, which complement the TrainMiC theoretical presentations, are described in detail to give a complete overview of the TrainMiC teaching material.JRC.DG.D.4-Isotope measurement