A sustainable and simple energy dispersive X-ray fluorescence method for sulfur determination at trace levels in biodiesel samples via formation of biodiesel spots on a suitable solid support

The aim of the present work is the development of a simple, sensitive and sustainable EDXRF method for the determination of trace amounts of sulfur in biodiesel samples. In this method, the deposition of several microliters of sample onto an organic thin layer and the analysis of the resulting adsorbed biodiesel spot by benchtop EDXRF is proposed. A careful study was performed to select the volume and the best solid support to deposit biodiesel samples, including filters made of different materials (glass fiber, Nylon, cellulose, paper) and a commercial disposable absorbent pad (UltraCarry, Rigaku). A critical issue that limits the use of most of these solid supports was the relative high blank signals that hamper the determination of sulfur at trace levels. Finally, it was found that best strategy was the deposition of 50 µL of biodiesel on the UltraCarry sample retainer. Operating conditions for EDXRF measurements were also evaluated to obtain the best instrumental sensitivity for sulfur determination (Excitation: 20 kV, no primary filter, measurement time: 300 s). Using the best analytical conditions the quantification limit of the method was 7 mg kg -1 of sulfur. This value is even better than the one reported in the ASTM D4294 method (LOQ: 16.0 mg kg -1 ) but using a sample amount 100 times smaller. The linearity was confirmed in the range of 10–100 mg kg -1 by analyzing a set of commercial biodiesel standards. Accuracy and precision of the results, evaluated by the analysis of samples prepared with the same matrix as the standards, with levels of 20, 40 and 75 mg kg -1 of sulfur, and processed as unknowns, proved acceptable (Recoveries: 94.3–110.6%, RSD: 10.8–13.6%, n = 3) for the intended purpose. Overall, the performance of the method developed is promising and it could be used to determine trace amounts of sulfur in biodiesel samples in a simple, sustainable and cost-effective way. Furthermore, since the original sample is adsorbed onto a solid support, repeat confirmatory analyses on the same specimen, if needed, can be carried out

A novel approach for adapting the standard addition method to single particle-ICP-MS for the accurate determination of NP size and number concentration in complex matrices; 35414390

This paper presents a novel approach, based on the standard addition method, for overcoming the matrix effects that often hamper the accurate characterization of nanoparticles (NPs) in complex samples via single particle inductively coupled plasma mass spectrometry (SP-ICP-MS). In this approach, calibration of the particle size is performed by two different methods: (i) by spiking a suspension of NPs standards of known size containing the analyte, or (ii) by spiking the sample with ionic standards; either way, the measured sensitivity is used in combination with the transport efficiency (TE) for sizing the NPs. Moreover, such transport efficiency can be readily obtained from the data obtained via both calibration methods mentioned above, so that the particle number concentration can also be determined. The addition of both ionic and NP standards can be performed on-line, by using a T-piece with two inlet lines of different dimensions. The smaller of the two is used for the standards, thus ensuring a constant and minimal sample dilution. As a result of the spiking of the samples, mixed histograms including the signal of the sample and that of the standards are obtained. However, the use of signal deconvolution approaches permits to extract the information, even in cases of signal populations overlapping. For proofing the concept, characterization of a 50 nm AuNPs suspension prepared in three different media (i.e., deionized water, 5% ethanol, and 2.5% tetramethyl ammonium hydroxide-TMAH) was carried out. Accurate results were obtained in all cases, in spite of the matrix effects detected in some media. Overall, the approach proposed offers flexibility, so it can be adapted to different situations, but it might be specially indicated for samples for which the matrix is not fully known and/or dilution is not possible/recommended. © 2022 The Author

Quo vadis high-resolution continuum source atomic/molecular absorption spectrometry?

After more than a decade since its commercial introduction, high-resolution continuum source atomic/molecular absorption spectrometry may be facing a mid-life crisis. Certainly, it is no longer a novel technique full of unknown potential, so it would already be time to establish the fields for which it is most suitable. This is, however, not so simple for a number of reasons. In the first place, more than a technique what we are discussing herein is a type of instrumentation with the potential to use two different techniques (atomic or molecular absorption), making it somewhat unique. Furthermore, the two techniques have not been explored equally, and more research on the mechanisms of formation of diatomic molecules is clearly needed. In the second place, new possibilities have recently appeared in the literature that need to be weighed as well. And there is the still unfulfilled, but nowadays more technically feasible than ever, promise to significantly increase the multi-elemental capabilities. This review critically examines the main research areas currently explored (namely, (i) direct analysis of solids and complex liquid materials, and (ii) determination of non-metals at trace levels via monitoring of molecular species) as well as the new venues (specifically, (i) isotopic analysis via monitoring of molecular species, and (ii) selective detection, quantification and sizing of nanoparticles) while also considering new instrumental developments, in an attempt to properly place high-resolution continuum source atomic/molecular absorption spectrometry in the field of trace element and isotopic analysis

Exploring the influence of consumer characteristics on veal credence and experience guarantee purchasing motivators

In Europe, in the last decades, public administration has encouraged extensive livestock farming systems, usually related to high quality meat and the preservation of endangered local breeds. Nevertheless, its continuity in the near future should be based on adapting it to the market requirements. This paper investigates consumers’ preferences heterogeneity towards veal attributes, as well as the linkage between a wide range of consumer traits and attributes that motivate purchasing of veal with unique characteristics. Main method of analysis included a choice experiment method. Findings showed that regional origin and health information play a stronger role than tenderness degree guarantee at the moment of choice. Moreover, regional origin is more relevant when it is linked to a local breed. Nevertheless, heterogeneous preferences have been detected. In contrast to the general trend, one-person households attach greater importance to the presence of a high degree of tenderness guarantee. Furthermore, younger consumers value more this guarantee, while expert consumers do not

Dried matrix spots and clinical elemental analysis. Current status, difficulties, and opportunities

This article examines the increasing importance of dried matrix spots (DMS), such as dried blood spots, dried urine spots, etc., in biomedical research, the challenges associated with their analysis when quantitative elemental information is aimed at, as well as the benefits deriving from the further usage of these types of samples. The article briefly reviews the historical evolution of this sampling approach in elemental clinical analysis, stressing prospective areas of applications (e.g., newborns or prosthesis control), the methodologies most recently developed to produce DMS of known volume, as well as novel strategies proposed to analyze them, often related to direct solid sampling techniques or fast lixiviation methods. Finally, the article discusses the type of information that could be obtained after isotopic analysis of DMS when targeting non-traditional stable isotopes (e.g., Cu, Fe or Zn), which can significantly help in the early diagnosis of some medical conditions (e.g. Wilson's disease)

To shift, or not to shift: Adequate selection of an internal standard in mass-shift approaches using tandem ICP-mass spectrometry (ICP-MS/MS)

The use of an internal standard to correct for potential matrix effects and instrument instability is common practice in ICP-MS. However, with the introduction of a new generation of ICP-MS instrumentation with a tandem mass spectrometry configuration (ICP-MS/MS), the use of chemical resolution in a mass-shift approach has become much more popular, suggesting that the appropriate selection of an internal standard needs revision. In this particular case, it needs to be decided whether the internal standard should also be subjected to a mass-shift or can simply be monitored on-mass ("to shift, or not to shift"). In this work, 17 elements covering a wide range of masses (24-205 amu) and ionization energies (3.89-9.39 eV) were measured via on-mass and/or mass-shift strategies, and the corresponding atomic ions and reaction product ions were monitored during various systematic experiments. For mass-shifting, an NH3/He gas mixture was used to obtain NH3-based reaction product ions (cluster formation). Product ion scanning (PIS) was used for assessing the differences in reactivity between the different analytes and for the identification of the best suited reaction product ions. It was found that the use of chemical resolution can significantly affect the short-term signal stability and that ion signals measured on-mass are not affected in the same way as those measured mass-shifted. Variations affecting the signal intensities of both atomic and reaction product ions can be attributed to the ion-molecule chemistry occurring within the collision/reaction cell and were found to be related with some degree of initial instability in the cell and differences in reactivity. The use of a sufficiently long stabilization time, however, avoids or at least mitigates such differences in the behavior between signals monitored on-mass and after mass-shifting, respectively. Furthermore, the introduction of cell disturbances, such as those generated after quickly switching between different sets of operating conditions in a multi-tune method, revealed significant differences in signal behavior between atomic and reaction product ions, potentially hampering the use of an internal standard monitored on-mass when the analysis is based on an analyte monitored after mass-shifting. However, the use of a reasonable waiting time again greatly mitigates such differences, with the duration of this stabilization time depending on the magnitude of the cell disturbances (e.g., switch between vented and pressurized mode or only between pressurized modes using different gas flow rates). In addition, also the effect of varying different instrument settings (plasma power, torch position, and gas and liquid flow rates) was evaluated, but no remarkable differences were found between signals monitored on-mass and those mass-shifted. Interestingly, a statistical evaluation of the influence of the different settings on the signal intensities of all ions monitored did not reveal the a priori important role of some properties traditionally suggested for adequate selection of analyte/internal standard pairs, such as mass number or ionization energy, as also suggested in other recent studies. © The Royal Society of Chemistry

A simple dilute-and-shoot approach for the determination of ultra-trace levels of arsenic in biological fluids via ICP-MS using CH3F/He as a reaction gas

The performance of a mixture of CH3F/He (1/9) as a reaction gas for the determination of As in biological fluids using a quadrupole ICP-MS instrument has been explored. A simple (dilute-and-shoot) interference-free method has been developed to quantify As concentrations at trace and ultra-trace levels in matrices with a high Cl content. As+ reacts with CH3F (through CH3F addition, followed by HF elimination) with high efficiency forming AsCH2 + as the primary reaction product, which can be monitored at a mass-to-charge ratio of 89, free from the Cl-based interferents (e.g., 40Ar35Cl+ and 40Ca35Cl+) that hamper the monitoring of 75As+. Matrix effects are overcome by the use of Te as an internal standard and the addition of 3% v/v ethanol to all samples and calibration standard solutions. The method presented was validated by analysing a set of reference materials (blood, serum and urine) and by assessing As recovery from a set of real blood samples. With this method, the limit of detection was calculated to be 0.8 ng L-1 As, favourably comparable to the vast majority of values reported in the literature, even with those obtained using more sophisticated sector-field instrumentation

Cu fractionation, isotopic analysis, and data processing <i>via</i> machine learning: new approaches for the diagnosis and follow up of Wilson's disease <i>via</i> ICP-MS

Information about Cu fractionation and Cu isotopic composition can be paramount when investigating Wilson's disease (WD). This information can provide a better understanding of the metabolism of Cu. Most importantly, it may provide an easy way to diagnose and to follow the evolution of WD patients. For such purposes, protocols for Cu determination and Cu isotopic analysis via inductively coupled plasma mass spectrometry were investigated in this work, both in bulk serum and in the exchangeable copper (CuEXC) fractions. The CuEXC protocol provided satisfactory recovery values. Also, no significant mass fractionation during the whole analytical procedure (CuEXC production and/or Cu isolation) was detected. Analyses were carried out in controls (healthy persons), newborns, patients with hepatic disorders, and WD patients. While the results for Cu isotopic analysis are relevant (e.g., δ65Cu values were lower for both WD patients under chelating treatment and patients with hepatic problems in comparison with those values obtained for WD patients under Zn treatments, controls, and newborns) to comprehend Cu metabolism and to follow up the disease, the parameter that can help to better discern between WD patients and the rest of the patients tested (non-WD) was found to be the REC (relative exchangeable Cu). In this study, all the WD patients showed a REC higher than 17%, while the rest showed lower values. However, since establishing a universal threshold is complicated, machine learning was investigated to produce a model that can differentiate between WD and non-WD samples with excellent results (100% accuracy, albeit for a limited sample set). Most importantly, unlike other ML approaches, our model can also provide an uncertainty metric to indicate the reliability of the prediction, overall opening new ways to diagnose WD

Living in a transient world: ICP-MS reinvented via time-resolved analysis for monitoring single events

After 40 years of development, inductively coupled plasma-mass spectrometry (ICP-MS) can hardly be considered as a novel technique anymore. ICP-MS has become the reference when it comes to multi-element bulk analysis at (ultra)trace levels, as well as to isotope ratio determination for metal(loid)s. However, over the last decade, this technique has managed to uncover an entirely new application field, providing information in a variety of contexts related to the individual analysis of single entities (e.g., nanoparticles, cells, or micro/nanoplastics), thus addressing new societal challenges. And this profound expansion of its application range becomes even more remarkable when considering that it has been made possible in an a priori simple way: by providing faster data acquisition and developing the corresponding theoretical substrate to relate the time-resolved signals thus obtained with the elemental composition of the target entities. This review presents the underlying concepts behind single event-ICP-MS, which are needed to fully understand its potential, highlighting key areas of application (e.g., single particle-ICP-MS or single cell-ICP-MS) as well as of future development (e.g., micro/nanoplastics)

Inference in supervised spectral classifiers for on-board hyperspectral imaging: An overview

Machine learning techniques are widely used for pixel-wise classification of hyperspectral images. These methods can achieve high accuracy, but most of them are computationally intensive models. This poses a problem for their implementation in low-power and embedded systems intended for on-board processing, in which energy consumption and model size are as important as accuracy. With a focus on embedded anci on-board systems (in which only the inference step is performed after an off-line training process), in this paper we provide a comprehensive overview of the inference properties of the most relevant techniques for hyperspectral image classification. For this purpose, we compare the size of the trained models and the operations required during the inference step (which are directly related to the hardware and energy requirements). Our goal is to search for appropriate trade-offs between on-board implementation (such as model size anci energy consumption) anci classification accuracy