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