Analytical Chemistry

The current baseline architectures in the field of the Internet of Things (IoT) strongly recommends the use of edge computing in the design of the solution applications instead of the traditional approach which solely uses the cloud/core for analysis and data storage. This research, therefore, focuses on formulating an edge-centric IoT architecture for smartphones which are very popular electronic devices that are capable of executing complex computational tasks at the network edge. A novel smartphone IoT architecture (SMIoT) is introduced that supports data capture and preprocessing, model (i.e., machine learning models) deployment, model evaluation and model updating tasks. Moreover, a novel model evaluation and updating scheme is provided which ensures model validation in real-time. This ensures a sustainable and reliable model at the network edge that automatically adjusts to changes in the IoT data subspace. Finally, the proposed architecture is tested and evaluated using an Io...

Anabolic-androgenic steroids (AASs), a group of compounds frequently misused by athletes and, unfortunately, also by the general population, have lately attracted global attention; thus, significant demands for more precise, facile, and rapid AAS detection have arisen. The standard methods ordinarily used for AAS determination include liquid and gas chromatography coupled with mass spectrometry. However, good knowledge of steroid metabolism, pretreatment of samples (such as derivatization), and well-trained operators of the instruments are required, making this procedure expensive, complicated, and not routinely applicable. In the drive to meet current AAS detection demands, the scientific focus has shifted to developing novel, tailor-made approaches leading to time- and cost-effective, routine, and field-portable methods for AAS determination in various matrices, such as biological fluids, food supplements, meat, water, or other environmental components. Therefore, herein, we prese...

Wavelength dispersive X-ray fluorescence (WD-XRF) spectrometry has been widely used for elemental quantification of mortars and cements. In this kind of instrument, samples are usually prepared as pellets or fused beads and the whole volume of sample is measured at once. In this work, the usefulness of a dual energy dispersive X-ray fluorescence spectrometer (ED-XRF), working at two lateral resolutions (1 mm and 25 μm) for macro and microanalysis respectively, to develop quantitative methods for the elemental characterization of mortars and concretes is demonstrated. A crucial step before developing any quantitative method with this kind of spectrometers is to verify the homogeneity of the standards at these two lateral resolutions. This new ED-XRF quantitative method also demonstrated the importance of matrix effects in the accuracy of the results being necessary to use Certified Reference Materials as standards. The results obtained with the ED-XRF quantitative method were compare...

Elemental analysis of different sediment cores originating from the Cartagena–La Union mining district in Spain was carried out by means of a programmable small-spot energy-dispersive X-ray fluorescence (EDXRF) spectrometer to study the distribution of heavy metals along soil profiles. Cores were obtained from upstream sediments of a mining creek, from the lowland sedimentation plain, and from a mining landfill dump (tailings pile). A programmable two-dimensional (2D) stage and a focal spot resolution of 600 μm allow us to obtain complete core mapping. Geochemical results were verified using a more powerful wavelength-dispersion X-ray fluorescence (WDXRF) technique. The data obtained was processed in order to study the statistical correlations within the elemental compositions. The results obtained allow us to observe the differential in-depth distribution of heavy metals among the sampled zones. Dump site cores exhibit a homogeneous distribution of heavy metals, whereas the alluvia...

Model-Driven Engineering (MDE) is widely applied in the industry to develop new software functions and integrate them into the existing run-time environment of a Cyber-Physical System (CPS). The design of a software component involves designers from various viewpoints such as control theory, software engineering, safety, etc. In practice, while a designer from one discipline focuses on the core aspects of his field (for instance, a control engineer concentrates on designing a stable controller), he neglects or considers less importantly the other engineering aspects (for instance, real-time software engineering or energy efficiency). This may cause some of the functional and non-functional requirements not to be met satisfactorily. In this work, we present a co-design framework based on timing tolerance contract to address such design gaps between control and real-time software engineering. The framework consists of three steps: controller design, verified by jitter margin analysis ...

The quality control of discretely manufactured parts typically involves defect recognition activities, which are time-consuming, repetitive tasks that must be performed by highly trained and/or experienced personnel. However, in the context of the fourth industrial revolution, the pertinent goal is to automate such procedures in order to improve their accuracy and consistency, while at the same time enabling their application in near real-time. In this light, the present paper examines the applicability of popular deep neural network types, which are widely employed for object detection tasks, in recognizing surface defects of parts that are produced through a die-casting process. The data used to train the networks belong to two different datasets consisting of images that contain various types of surface defects and for two different types of parts. The first dataset is freely available and concerns pump impellers, while the second dataset has been created during the present study...

Twenty-four substances, mainly NIAS, have been tentatively identified in food contact polycarbonate through the application a new, fast, and automated analytical strategy for the investigation of unknowns in food contact materials. Most of the identified compounds were plasticizers, slip agents, antioxidants, and ultraviolet stabilizers and fragrances, and the majority of them have not been previously identified in PC food contact materials. The workflow setup includes an intelligent data acquisition applied using LC-Orbitrap Tribrid-HRMS (MS3), with an automated data processing using Compound DiscovererTM. To obtain a high confidence identification of unknown substances, a very strict criterion has been established, which comprises exact mass, isotopic profile, MS2 match, retention time, and MS3 match. To check for the safety of the migration from the food contact polycarbonate, a risk assessment was achieved using the threshold of the toxicological concern (TTC) approach. Except f...

Data-independent acquisition (DIA) based strategies have been explored in recent years for improving quantitative analysis of metabolites. However, the data analysis is challenging for DIA methods as the resulting spectra are highly multiplexed. Thus, the DIA mode requires advanced software analysis to facilitate the data deconvolution process. We proposed a pipeline for quantitative profiling of pharmaceutical drugs and serum metabolites in DIA mode after comparing the results obtained from full-scan, Data-dependent acquisition (DDA) and DIA modes. using open-access software. Pharmaceutical drugs (10) were pooled in healthy human serum and analysed by LC-ESI-QTOF-MS. MS1 full-scan and Data-dependent (MS2) results were used for identification using MS-DIAL software while deconvolution of MS1/MS2 spectra in DIA mode was achieved by using Skyline software. The results of acquisition methods for quantitative analysis validated the remarkable analytical performance of the constructed wo...

Background: A validated high performance planar chromatographic analysis for a combination medication of corticosteroids mometasone furoate and bronchodilators formoterol fumarate available as Evocort®: inhaler in market was developed. It is used for treating asthma, a reversible obstructive airways disease. Materials and Methods: The HPTLC chromatographic condition was optimised using aluminium sheets formerly coated with silica gel 60F254 as stationary phase and toluene: methyl alcohol: methanoic acid (12.5:4:0.3 v/v/v) as mobile phase. Results: Formoterol fumarate and mometasone furoate concentration was found to be directly proportional to peak area in the range of 120-720 ng/band and 3996-23976 ng/band, respectively. Results of precision studies were between 0.77-1.274 stated in %RSD and recovery studies ranged from 99101% indicating very low inter day variability and good reproducibility of the method. Fractional factor design was applied to five factors i.e. volume of mobile ...

A nonlinear MEMS multimass sensor is investigated. The MEMS design consists of an array of nonlinear microcantilevers clamped to a shuttle mass which, in turn, is attached to a linear spring and a dashpot. The microcantilevers are made of a polymeric hosting matrix reinforced by aligned carbon nanotubes (CNT) with different CNT volume fractions in each cantilever so as to suitably tune the frequency bandwidth of the device. The advantages of a single input-single output (SISO) system are here exploited for the design, actuation and detection principles as in previous literature.

The complex wave structure of annular gas–liquid flow with disturbance waves and liquid entrainment is a result of the evolution of high-frequency initial waves, appearing at the very inlet of the flow, prior to the hydrodynamic stabilization of liquid film. This stage of flow evolution is studied experimentally, using a shadow technique, and theoretically, using a linear stability analysis of the Orr–Sommerfeld equation in both phases. The present work is focused on the comparison of earlier results obtained in air–water downward flow with the new results obtained in upward flow and with more viscous liquids. The flow orientation affects the shape of the liquid film prior to stabilization; the initial film area is thicker but shorter in upward flow. Upward flow orientation also leads to a lower frequency and the increment of growth of initial waves. The viscosity effect is found to be weak if flow rates of both phases are the same. The model is mostly able to reproduce the qualitat...

The rapid growth of the Internet of Things (IoT) and its attributes of constrained devices and a distributed environment make it difficult to manage such a huge and growing network of devices on a global scale. Existing traditional access-control systems provide security and management to the IoT system. However, these mechanisms are based on central authority management, which introduces issues such as a single point of failure, low scalability, and a lack of privacy. In order to address these problems, many researchers have proposed using blockchain technology to achieve decentralized access control. However, such models are still faced with problems such as a lack of scalability and high computational complexity. In this paper, we propose a light-weight hierarchical blockchain-based multi-chaincode access control to protect the security and privacy of IoT systems. A clustering concept with BC managers enables the extended scalability of the proposed system. The architecture of th...

Biodegradable/biocompatible microspheres have been prepared from poly(lactic acid-co-glycidyl methacrylate), P(LA-co-GMA), copolymers by a phase inversion emulsification (PIE) process. As the copolymer contains unsaturated functional groups, this can be crosslinked by employing thermo-curing reaction. Effects of co-surfactant concentrations and the aqueous phase addition rate on efficiency of the particle formation are evaluated. The addition of sodium dodecyl sulfate (SDS) co-surfactant at slow rates leads to narrow size distribution and higher stability of the microspheres, due to formation of effective structures of polyvinyl alcohol (PVA) surfactant and SDS at the oil/aqueous interface. The resulting microspheres are spherical shape with rough wrinkled surface morphology and bimodal particles size distribution at 1 and 10 μm. Curable behavior of the microspheres are also investigated. The semi-crystalline particles consist of network structure with high gel content of 50%, as th...

The entrance of the outer electrode is a Coanda surface, which facilitates better gas flow into the analytical gap and around the inner electrode. The simulation suggests the potential for gas from the HESI ion source to hit the lower surface of the inner electrode orifice, an effect which may become pronounced with high gas flow rates. However, gas and ion flow continue around the inner electrode to reach the FAIMS exit, and enter into the MS. Figure 3. Evaluation of ion transmission through FAIMS in non-energized mode. Ion transmission while using FAIMS in non-energized mode ranged from 25–41% with no carrier gas applied and 15–29% when carrier gas was set to 7 L/min, compared to FAIMS not mounted.