Accurate mass measurements and ultrahigh-resolution: evaluation of different mass spectrometers for daily routine analysis of small molecules in negative electrospray ionization mode

Six mass spectrometers based on different mass analyzer technologies, such as time-of-flight (TOF), hybrid quadrupole-TOF (Q-TOF), orbitrap, Fourier transform ion cyclotron resonance (FT-ICR), and triple quadrupole (QqQ), installed at independent laboratories have been tested during a single day of work for the analysis of small molecules in negative electrospray ionization (ESI) mode. The uncertainty in the mass measurements obtained from each mass spectrometer has been determined by taking the precision and accuracy of replicate measurements into account. The present study is focused on calibration processes (before, after, and during the mass measurement), the resolving power of the mass spectrometers, and the data processing for obtaining elemental formulae. The mass range between m/z 100 and 600 has been evaluated with a mix of four standards. This mass range includes small molecules usually detected in food and environmental samples. Negative ESI has been tested as there is almost no data on accurate mass (AM) measurements in this mode. Moreover, it has been used because it is the ESI mode for analysis of many compounds, such as pharmaceutical, herbicides, and fluorinated compounds. Natural organic matter has been used to demonstrate the significance of ultrahigh-resolution in complex mixtures. Sub-millidalton accuracy and precision have been obtained with Q-TOF, FT-ICR, and orbitrap achieving equivalent results. Poorer accuracy and precision have been obtained with the QqQ used: 11 mDa root-mean-square error and 6–11 mDa standard deviation. Some advice and requirements for daily AM routine analysis are also discussed here.     

Biparametric Potentiometric Analytical Microsystem Based on the Green Tape Technology

The construction and evaluation of a Low Temperature Co‐fired Ceramics (LTCC)‐based microsystem prototype as a possible on‐site microanalyzer to monitor the presence of two ions in water simultaneously is presented. The approach has been assayed to detect nitrate and chloride ions as model analytes by means of integrating in the same single substrate an ion selective polymeric membrane to nitrate and two screen‐printed Ag/AgCl electrodes. One supplies the chloride ion concentration and the other is to complete the potentiometric detection system as the reference electrode. The results obtained by the full characterization of the microanalyzer prove the relevance of the proposal and the possibility to be transferred to real‐world samples and environmental monitoring.     

Regioselectivity in intermolecular Pauson-Khand reactions of dissymmetric fluorinated alkynes

Stoichiometric and catalytic intermolecular Pauson-Khand reactions (PKRs) of dissymmetric fluorinated alkynes were performed, affording regioselectively α-fluorinated cyclopentenones. Ethyl 4,4,4-trifluorobutynoate was an excellent substrate; its reaction with norbornadiene gave the corresponding PKR adduct in good yield and complete regioselectivity. Conjugate addition of nitroalkanes or cyanide to this adduct is stereospecific and entails concomitant loss of a trifluoromethyl group. This reaction can be exploited to prepare cyclopentenones featuring quaternary centers.     

Immunochemical determination of oxytetracycline in fish: Comparison between enzymatic and time-resolved fluorometric assays

An indirect competitive enzyme-linked immunosorbent assay (ELISA) with photometric detection of horseradish peroxidase (HRP) activity, was developed in plate to detect oxytetracycline (OTC) in Gilthead sea bream (Sparus aurata) samples. The results were compared to those obtained by time-resolved fluoroimmunoassay (TR-FIA) using a secondary antibody with coproporphyrin of platinum (II) (PtCP) as marker. The limits of detection obtained in fish extract were 16 and 0.08 μg kg⁻¹ for photometric and fluorometric detections, respectively; therefore, they were suitable for fish quality control according to the maximum residue level established by the European Union.An extraction procedure using methanol:water 70:30 (v/v) + 1 mL EDTA 0.1 M, and different clean-up procedures based on solid-phase extraction (C₁₈, polymeric reversed phase, SCX, Si) was assayed. The matrix effects were overcome by means of an average tetracycline-free fish extract calibration curve used for quantification.The OTC optimized ELISA can also be applied to determine tetracycline and chlortetracycline residues with good results. Thus, the developed immunoassay could be considered as a generic assay for the most used tetracyclines in aquaculture antibiotic treatments.In order to confirm the utility of the developed immunoassay as a semi-quantitative methodology, fish samples obtained from different supermarkets were analyzed. Results correlate well with those obtained with a reference HPLC method.     

Diagnostic method based on the analysis of the vibration and acoustic emission energy for emergency diesel generators in nuclear plants

Ensuring the availability and reliability of the Emergency Diesel Generators (EDGs) in nuclear power plants is a critical aspect to guarantee the plant safe shutdown in case of an emergency scenario. An effective engine diagnosis method is essential to fulfill that goal. For that purpose, this paper presents a fast and automatic engine diagnosis method based on a single parameter: the vibration/AE signals energy. The method is based on the comparison of the vibration and AE energy with reference values to determine whether the engine condition is faulty. The method was applied in a test engine, and proved to work satisfactorily. Therefore, it was used to diagnose the EDGs in a nuclear power plant, where regular rigorous inspections are effected periodically. An injector fault was detected thanks to the diagnosis method.     

Thawing as a critical pre-analytical step in the lipidomic profiling of plasma samples: New standardized protocol

Lipid profiling is a promising tool for the discovery and subsequent identification of biomarkers associated with various diseases. However, data quality is quite dependent on the pre-analytical methods employed. To date, potential confounding factors that may affect lipid metabolite levels after the thawing of plasma for biomarker exploration studies have not been thoroughly evaluated. In this study, by means of experimental design methodology, we performed the first in-depth examination of the ways in which thawing conditions affect lipid metabolite levels. After the optimization stage, we concluded that temperature, sample volume and the thawing method were the determining factors that had to be exhaustively controlled in the thawing process to ensure the quality of biomarker discovery. Best thawing conditions were found to be: 4 °C, with 0.25 mL of human plasma and ultrasound (US) thawing. The new US proposed thawing method was quicker than the other methods we studied, allowed more features to be identified and increased the signal of the lipids. In view of its speed, efficiency and detectability, the US thawing method appears to be a simple, economical method for the thawing of plasma samples, which could easily be applied in clinical laboratories before lipid profiling studies.