FLIIMP - a community software for the processing, calibration, and reporting of liquid water isotope measurements on cavity-ring down spectrometers.

Precise and accurate measurements of the stable isotope composition from precipitation, land ice, runoff, and oceans provide critical information on Earth's water cycle. The analysis, post-processing, and calibration of raw analytical signals from laser spectrometers during sample analysis involves a number of critical procedures to counteract instrumental drift, inter-sample memory effects, and the quantification of total uncertainty. We present a new software tool for the post-processing and calibration named FLIIMP (FARLAB Liquid Water Isotope Measurement Processor). FLIIMP facilitates sample processing by (1) a graphical user interface that guides the user along the processing steps from corrections for memory effects, drift, and mixing ratio to calibration, and (2) allows to monitor long-term measurement system behaviour, currently for Picarro-brand water isotope analysers. Final data files are accompanied by a detailed calibration report. Being an open-source software for the major operating systems, users can adapt FLIIMP to their laboratory environment, and the community can contribute the software development. •FLIIMP facilitates post-processing, calibration and reporting for stable water isotope liquid sample analysis.•The stepwise, interactive graphical user interface reduces possibility of errors and shortens processing time.•Open source software enables future development of FLIIMP by the user community.

Fiber-Based SERS-Fluidic Polymeric Platforms for Improved Optical Analysis of Liquids.

Downsizing surface-enhanced Raman spectroscopy (SERS) within microfluidic devices has opened interesting perspectives for the development of low-cost and portable (bio)sensors for the optical analysis of liquid samples. Despite the research efforts, SERS-fluidic devices still rely either on the use of expensive bulky set-ups or on polymeric devices giving spurious background signals fabricated via expensive manufacturing processes. Here, polymeric platforms integrating fluidics and optics were fabricated with versatile designs allowing easy coupling with fiber-based Raman systems. For the first time, anti-fouling photocurable perfluoropolyether (PFPE) was explored for high-throughput SERS-integrating chip fabrication via replica molding of negative stamps obtained through standard and advanced fabrication processes. The PFPE devices comprised networks of channels for fluid handling and for optical fiber housing with multiple orientations. Embedded microfeatures were used to control the relative positioning of the fibers, thus guaranteeing the highest signal delivering and collection. The feasibility of PFPE devices as fiber-based SERS fluidic platforms was demonstrated through the straightforward acquisition of Raman-SERS spectra of a mixture of gold nanoparticles as SERS substrates with rhodamine 6G (Rh6G) at decreasing concentrations. In the presence of high-performing gold nanostars, the Rh6G signal was detectable at dilutions down to the nanomolar level even without tight focusing and working at low laser power-a key aspect for analyte detection in real-world biomedical and environmental applications.

SARS-CoV-2 and other pathogens could be determined in liquid samples from soils.

In the current COVID-19 pandemic, SARS-CoV-2 has been quantified in wastewater in various countries, and wastewater based epidemiology has been proposed as a potential early warning tool for new outbreaks. However, even taking into account that poorly treated wastewater and sewage sludge may be spread on soils, there is no published paper dealing with the quantification of the virus in soil-related liquid samples, as could be runoff, leachates, or soil solution. To fill this gap, the authors of this piece propose reflections on the development of a methodological approach for the quantification of SARS-CoV-2 (and eventually other pathogens) in soil-related liquid samples.

Evaluation of Thin Film Microextraction for trace elemental analysis of liquid samples using LIBS detection.

An analytical methodology based in the combination of Thin Film Microextraction with Laser-induced Breakdown Spectroscopy (TFME-LIBS) was investigated, for the first time, for detection of Cu, Cr, Ni and Pb in aqueous solutions. In this methodology, the analytes were extracted in a thin film of adsorbent material deposited on a solid support, which was introduced in the sample to analyse. After extraction, the analytes retained in the adsorbent were analysed by LIBS. In order to obtain adsorbent films useful for the microextraction step, two different experimental procedures for film generation, denoted as Drop Casting Deposition and Mould Deposition, were evaluated. In both cases, graphene oxide was used as adsorbent material. The mould deposition procedure was found to produce more homogeneous graphene oxide layers, leading to more uniform distribution of the adsorbed analytes on the graphene oxide surface. Experimental parameters affecting the TFME procedure, such as the adsorbent amount and extraction time, were studied. Under optimum microextraction conditions, the analytical figures of merit of the proposed TFME-LIBS method were evaluated, leading to limits of detection ranging from 41 µg kg-1 and 52 µg kg-1. Method trueness, evaluated from the analysis of a real sample of bottle water, led to recovery values about 70%, indicating the existence of strong matrix effects probably due to the presence of major cations in the bottle water. After 50% dilution of the sample with deionized water, recoveries values improved to 100%-108%.

A calcium alginate sponge with embedded gold nanoparticles as a flexible SERS substrate for direct analysis of pollutant dyes.

A surface-enhanced Raman scattering (SERS) substrate with good flexibility and high water absorbing capacity is reported. It consists of a calcium alginate sponge incorporating gold nanoparticles. These are in close contact with the sponge without the need for amino or sulfhydryl modification. The substrate is capable of detecting the dyes crystal violet (CV) and malachite green (MG) in water directly and rapidly by immersing it into the liquid sample. Preconcentration and separation are not required. The dyes absorbed on the sponge can be detected without drying and thus the whole analytical process can be completed within 3 min. The results show that the lowest detectable concentrations are 0.1 and 0.25 µg⋅L-1 for CV and MG, respectively. This is lower than the minimum required performance limits set by the European Commission and the US EPA. Moreover, MG and CV can be simultaneously detected in liquid samples due to their different SERS bands (at 1216 and 1534 cm-1, respectively). It should be noted that the molecular structures of MG and CV are very similar. Therefore, the method has a large potential for determination of several analytes simultaneously even in complex sample metrics. Graphical abstract Schematic presentation of the fabrication of a sodium alginate sponge loaded with gold nanoparticles. Gold nanoparticles together with gel-like alginate were freeze-dried to form the sponge. The sponge was cross-linked by CaCl2 solution and then it was freeze-dried again.

Dispersive micro solid-phase extraction (DµSPE) with graphene oxide as adsorbent for sensitive elemental analysis of aqueous samples by laser induced breakdown spectroscopy (LIBS).

In this work, the combination of dispersive micro solid-phase extraction (DµSPE) with laser-induced breakdown spectroscopy (LIBS) was evaluated for simultaneous preconcentration and detection of Zn, Cd, Mn, Ni, Cr and Pb in aqueous samples. Two adsorbent materials were tested in the microextraction step, namely graphene oxide and activated carbon. In both cases, the microextraction process consisted in the dispersion of a small quantity of adsorbent in the sample solution containing the analytes. However, while the use of activated carbon required a previous chelation of the metals, this step was avoided with the use of graphene oxide. After extraction, the analytes retained in the adsorbents were analysed by LIBS. Several experimental factors affecting the extraction of the metals (adsorbent amount, pH and extraction time) were optimized by means of the traditional univariate approach. Under optimum microextraction conditions, the analytical features of the proposed DµSPE-LIBS methods were assessed, leading to limits of detection below 100 µg kg-1 and 50 µg kg-1 with the use of activated carbon and graphene oxide, respectively, as adsorbents in the DµSPE process. Trueness evaluation of the most sensitive procedure was carried out by spike and recovery experiments in a real sample of tap water, leading to recovery values in the range 98-110%.

Dispersive liquid-liquid microextraction for metals enrichment: a useful strategy for improving sensitivity of laser-induced breakdown spectroscopy in liquid samples analysis.

A rapid and efficient Dispersive Liquid-Liquid Microextraction (DLLME) followed by Laser-Induced Breakdown Spectroscopy detection (LIBS) was evaluated for simultaneous determination of Cr, Cu, Mn, Ni and Zn in water samples. Metals in the samples were extracted with tetrachloromethane as pyrrolidinedithiocarbamate (APDC) complexes, using vortex agitation to achieve dispersion of the extractant solvent. Several DLLME experimental factors affecting extraction efficiency were optimized with a multivariate approach. Under optimum DLLME conditions, DLLME-LIBS method was found to be of about 4.0-5.5 times more sensitive than LIBS, achieving limits of detection of about 3.7-5.6 times lower. To assess accuracy of the proposed DLLME-LIBS procedure, a certified reference material of estuarine water was analyzed.

An in-needle extraction technique in determination of organic compounds released from dental tissue conditioners incubated in artificial saliva.

The use of an in-needle technique for direct isolation of analytes from real liquid samples is a new proposal. The in-needle technique has been relatively seldom used for direct sampling of liquid matrix through the needle. In this work the in-needle technique has been applied for the determination of compounds evolved to artificial saliva from dental prosthetic materials. It has been shown that results from the experiment with in-needle device were at least comparable with those obtained with using well known solid phase extraction (SPE). It is worth to mention that in-needle extraction offers some advantages: lower consumption of solvent, shorter step-preparation time and reduced costs. The compounds released from prosthetic materials may affect the stability of tissue conditioners and limit their long-term use in the oral cavity. Examined soft dental materials have been found to be stable as minor amount of various species have been emitted from them. Results of the stability tests of soft dental materials with the use of in-needle device on sample preparation step enable their quick evaluation and estimations of their quality.

Optimization of the in-needle extraction device for the direct flow of the liquid sample through the sorbent layer.

In-needle extraction was applied for preparation of aqueous samples. This technique was used for direct isolation of analytes from liquid samples which was achieved by forcing the flow of the sample through the sorbent layer: silica or polymer (styrene/divinylbenzene). Specially designed needle was packed with three different sorbents on which the analytes (phenol, p-benzoquinone, 4-chlorophenol, thymol and caffeine) were retained. Acceptable sampling conditions for direct analysis of liquid sample were selected. Experimental data collected from the series of liquid samples analysis made with use of in-needle device showed that the effectiveness of the system depends on various parameters such as breakthrough volume and the sorption capacity, effect of sampling flow rate, solvent effect on elution step, required volume of solvent for elution step. The optimal sampling flow rate was in range of 0.5-2 mL/min, the minimum volume of solvent was at 400 µL level.

In situ ionic-liquid-dispersive liquid-liquid microextraction of Sudan dyes from liquid samples.

In situ ionic-liquid-dispersive liquid-liquid microextraction was introduced for extracting Sudan dyes from different liquid samples followed by detection using ultrafast liquid chromatography. The extraction and metathesis reaction can be performed simultaneously, the extraction time was shortened notably and higher enrichment factors can be obtained compared with traditional dispersive liquid-liquid microextraction. When the extraction was coupled with ultrafast liquid chromatography, a green, convenient, cheap, and efficient method for the determination of Sudan dyes was developed. The effects of various experimental factors, including type of extraction solvent, amount of 1-hexyl-3-methylimidazolium chloride, ratio of ammonium hexafluorophosphate to 1-hexyl-3-methylimidazolium chloride, pH value, salt concentration in sample solution, extraction time and centrifugation time were investigated and optimized for the extraction of four kinds of Sudan dyes. The limits of detection for Sudan I, II, III, and IV were 0.324, 0.299, 0.390, and 0.655 ng/mL, respectively. Recoveries obtained by analyzing the seven spiked samples were between 65.95 and 112.82%. The consumption of organic solvent (120 µL acetonitrile per sample) was very low, so it could be considered as a green analytical method.