Phase Components Research Articles

Determination of phase components of impedance in the environments over hydrocarbon accumulation

Abstract The article presents a novel method for hydrocarbon accumulation exploration based on determining the phase components of impedance in environments over hydrocarbons. Experimental studies were conducted at the Rechitsa hydrocarbon field and Osipovichi underground gas storage. The phase characteristics of surface impedance of hydrocarbon accumulation were measured using amplitude-frequency-modulated signals. The results show that determining two components of surface impedance in this mode significantly improves the accuracy of hydrocarbon boundary determination. The developed method can be implemented at frequencies of 0.1-2 GHz, using modulation frequencies of 10-100 MHz, amplitude modulation coefficients of 0.1-1.0, and frequency modulation indices of 20-95. The findings of this research can be applied in electrical exploration for prospecting hydrocarbon accumulation.

Implementation of task-based language teaching in a Spanish language program: Instructors’ and students’ perceptions

Most research on task-based language teaching (TBLT) has focused on specific factors that play a role in task-based performance and learning, whereas considerably fewer studies have paid attention to how TBLT curricula have been developed and delivered in second language (L2) teaching contexts. However, it has been argued that the latter type of evaluative inquiry is crucial in order to advance the educational significance of the approach. While more evaluation studies have been published in recent years, few of them adopt a multi-methodological, longitudinal and cyclical perspective. The current study examines the planning and implementation of task-based instruction in a university-level Spanish as a foreign language program over a five-year period, with a particular emphasis on instructors’ and students’ perceptions about the approach. Data sources consisted of notes from meetings with instructors, classroom observations, students’ perceptions collected through journals, focus groups and questionnaires, and instructors’ perceptions collected through a questionnaire. The qualitative and quantitative analysis of these data revealed critical aspects of the planning phase, positive and challenging components of the approach, modifications made in response to participants’ perceptions, as well as a gradual increase regarding the level of acceptance of task-based instruction throughout the implementation. Implications for the implementation and evaluation of TBLT in other second language educational contexts are discussed.

Microstructure and mechanical properties of cellular (Ti,M)(C,N)-based cermets fabricated by pre-granulation and subsequent vacuum sintering

Cellular (Ti,M)(C,N)-based cermets were fabricated through pre-granulation followed by vacuum sintering. In this study, (Ti,Mo)(C,N) and (Ti,W,Ta)(C,N) solid solutions were utilized as hard phase components in agglomerates. The effects of the (Ti,M)(C,N) powders on the microstructure and mechanical properties of cellular cermets were studied. Cermet A, incorporating (Ti,Mo)(C,N) in the agglomerates, exhibited a cellular microstructure with double-layered agglomerates distributed in the matrix. By contrast, cermet B, which included (Ti,W,Ta)(C,N) in the agglomerates, exhibited a notable contrast between the agglomerates containing irregular elongated grains and the matrix. The mechanical properties of the cellular cermets were analyzed comprehensively in conjunction with the fractal dimension. Compared with cermet A, cermet B exhibited more transgranular fractures within the matrix, with dimples and tearing ridges visible in the agglomerates. Additionally, increased crack deflection, bridging, and bifurcation were observed near the interface, considerably impeding crack propagation. Overall, cermet A with significantly refined grains demonstrated higher hardness and TRS. The fracture morphology and crack propagation in cermet B were more complex and layered, resulting in the enhanced fracture toughness.

Lactate-mediated mixotrophic co-cultivation of Clostridium drakei and recombinant Acetobacterium woodii for autotrophic production of volatile fatty acids

BackgroundAcetogens, a diverse group of anaerobic autotrophic bacteria, are promising whole-cell biocatalysts that fix CO2 during their growth. However, because of energetic constraints, acetogens exhibit slow growth and the product spectrum is often limited to acetate. Enabling acetogens to form more valuable products such as volatile fatty acids during autotrophic growth is imperative for cementing their place in the future carbon neutral industry. Co-cultivation of strains with different capabilities has the potential to ease the limiting energetic constraints. The lactate-mediated co-culture of an Acetobacterium woodii mutant strain, capable of lactate production, with the Clostridium drakei SL1 type strain can produce butyrate and hexanoate. In this study, the preceding co-culture is characterized by comparison of monocultures and different co-culture approaches.ResultsC. drakei grew with H2 + CO2 as main carbon and energy source and thrived when further supplemented with D-lactate. Gas phase components and lactate were consumed in a mixotrophic manner with acetate and butyrate as main products and slight accumulation of hexanoate. Formate was periodically produced and eventually consumed by C. drakei. A lactate-mediated co-culture of the A. woodii [PbgaL_ldhD_NFP] strain, engineered for autotrophic lactate production, and C. drakei produced up to 4 ± 1.7 mM hexanoate and 18.5 ± 5.8 mM butyrate, quadrupling and doubling the respective titers compared to a non-lactate-mediated co-culture. Further co-cultivation experiments revealed the possible advantage of sequential co-culture over concurrent approaches, where both strains are inoculated simultaneously. Scanning electron microscopy of the strains revealed cell-to-cell contact between the co-culture partners. Finally, a combined pathway of A. woodii [PbgaL_ldhD_NFP] and C. drakei for chain-elongation with positive ATP yield is proposed.ConclusionLactate was proven to be a well-suited intermediate to combine the high gas uptake capabilities of A. woodii with the chain-elongation potential of C. drakei. The cell-to-cell contact observed here remains to be further characterized in its nature but hints towards diffusive processes being involved in the co-culture. Furthermore, the metabolic pathways involved are still speculatory for C. drakei and do not fully explain the consumption of formate while H2 + CO2 is available. This study exemplifies the potential of combining metabolically engineered and native bacterial strains in a synthetic co-culture.

Experimental study on flow boiling heat transfer characteristics of zeotropic mixture R1233zd(E)/R1234yf in horizontal tube

This paper experimentally investigated the flow boiling heat transfer characteristics of zeotropic mixture R1233zd(E)/R1234yf with different mass fractions (80/20, 70/30, 60/40) within an 8 mm inner diameter horizontal tube. An analysis of the impact of different experimental conditions on the flow boiling heat transfer coefficient (HTC) was conducted under different vapor quality 0–1, mass fractions 80/20, 70/30, 60/40, mass velocity 196.97–328.28 kg m−2 s−1, heat flux 35.95–48.93 kW/m−2(−|−), and saturation temperature 40–60 °C. Results indicated that the variety in the density of vapor phase components and concentration gradients within the mixture under diverse conditions exhibited a notable influence on the HTC. Using the experimental data, the accuracy of several widely used correlations for estimating the flow boiling HTC of mixture is evaluated. Considering the impact of property variations on convective boiling during flow boiling, a new correlation is proposed. The new correlation yields a higher prediction accuracy compared to other correlations, demonstrating its effectiveness in predicting the HTC of this mixture working fluid.

Enhancing Sustainable Analytical Chemistry in Liquid Chromatography: Guideline for Transferring Classical High-Performance Liquid Chromatography and Ultra-High-Pressure Liquid Chromatography Methods into Greener, Bluer, and Whiter Methods.

This review is dedicated to sustainable practices in liquid chromatography. HPLC and UHPLC methods contribute significantly to routine analytical techniques. Therefore, the transfer of classical liquid chromatographic methods into sustainable ones is of utmost importance in moving toward sustainable development goals. Among other principles to render a liquid chromatographic method green, the substitution of the organic solvent component in the mobile phase with a greener one received great attention. This review concentrates on choosing the best alternative green organic solvent to replace the classical solvent in the mobile phase for easy, rapid transfer to a more sustainable normal phase or reversed-phase liquid chromatography. The main focus of this review will be on describing the transfer of non-green to green and white chromatographic methods in an effort to elevate sustainability best practices in analytical chemistry. The greenness properties and greenness ranking, in addition to the chromatographic suitability of seventeen organic solvents for liquid chromatography, are mentioned to have a clear insight into the issue of rapidly choosing the appropriate solvent to transfer a classical HPLC or UHPLC method into a more sustainable one. A simple guide is proposed for making the liquid chromatographic method more sustainable.

Analysis of stability and internal flow mechanisms in spiral annular flow with different swirlers

Spiral annular flow within ducts is widely utilized in modern industry, with the swirler serving as a critical component in generating such flow patterns. The structure of the swirler significantly influences the generation and stability of the spiral annular flow. This study selected four different swirler structures with outstanding performance from previous research and analyzed their characteristics through visual image processing combined with numerical simulations. By analyzing the amplitude information of the wave fluctuations in the annular swirling flow liquid film under different operating conditions using probability density functions, it was found that the swirler A(Flat-vane swirler) and swirler B(Flat-vane swirler with hub) produced smaller fluctuations in the annular swirling flow liquid film, indicating better stability compared to the swirler C(Arc-vane swirler) and swirler D(Spiral-vane swirler), which exhibited poor performance. Combining the numerical simulation results with the analysis of the internal mechanism of the swirlers, it was discovered that within the swirler A and swirler B, the fluid between the swirler vanes experienced a larger pressure gradient, resulting in phenomena such as “jump” and “pull” under this pressure gradient. This, in turn, contributed to the generation of greater tangential velocity and radial pressure gradient after the fluid exited the swirler. Due to the influence of the swirler structure, the swirler A and swirler B did not completely separate the fluid region into four independent spaces. Instead, in the central connection area of the rear section of the swirler, the gas phase components aggregated earlier, greatly promoting the downstream generation of spiral annular flow. This study analyzed the two-phase flow process and mechanism inside the swirler, filling a gap in previous research and providing important references for the optimization and selection of swirlers.

A dual domain multi-exposure image fusion network based on spatial-frequency integration

Multi-exposure image fusion aims to generate a single high-dynamic image by integrating images with different exposures. Existing deep learning-based multi-exposure image fusion methods primarily focus on spatial domain fusion, neglecting the global modeling ability of the frequency domain. To effectively leverage the global illumination modeling ability of the frequency domain, we propose a novelty perspective on multi-exposure image fusion via the Spatial-Frequency Integration Framework, named MEF-SFI. Initially, we revisit the properties of the Fourier transform on the 2D image, and verify the feasibility of multi-exposure image fusion in the frequency domain where the amplitude and phase component is able to guide the integration of the illumination information. Subsequently, we present the deep Fourier-based multi-exposure image fusion framework, which consists of a spatial path and frequency path for local and global modeling separately. Specifically, we introduce a Spatial-Frequency Fusion Module to facilitate efficient interaction between dual domains and capture complementary information from input images with different exposures. Finally, we combine a dual domain loss function to ensure the retention of complementary information in both the spatial and frequency domains. Extensive experiments on the PQA-MEF dataset demonstrate that our method achieves visual-appealing fusion results against state-of-the-art multi-exposure image fusion approaches. Our code is available at https://github.com/SSyangguang/MEF-freq.

Hydrophilic interaction chromatographic evaluation of zwitterionic polymer grafted silica gel via multiple binding sites.

A novel zwitterionic polymer grafted silica stationary phase, Sil-PZIC, was prepared by bonding poly(ethylene maleic anhydride) molecules on the surface of silica via multiple binding sites, followed by ammonolysis of maleic anhydride through a nucleophilic substitution reaction with ethylenediamine. The stationary phase was characterized by solid-state 13C nuclear magnetic resonance, zeta potential, and elemental analysis and the results show the successful encapsulation of zwitterionic polymer on the surface of silica. The chromatographic performance of Sil-PZIC was investigated by using nucleosides and nucleic bases as test analytes The variation of retention and separation performance of these model compounds were investigated by varying the chromatographic conditions such as the components of mobile phase, salt concentration, and pH. The results show that the retention of the Sil-PZIC phase was dominated by a hydrophilic partitioning mechanism accompanied by secondary interactions such as electrostatic and hydrogen bonding. In addition, saccharides and Amadori compounds were also well separated on the Sil-PZIC, indicating that the Sil-PZIC column has potential application for separation of the polar compound.

Existence of optimal virtual element weights for mmWave FMCW MIMO radar based heart rate estimation

AbstractMeasuring heart rate is a critical component of assessing cardiac health and detecting potential heart diseases at an early stage. Various sensors, including electrocardiogram and photoplethysmograph, are commonly employed for this purpose. However, these conventional methods necessitate direct contact with the patient's skin which may be impractical or uncomfortable in situations involving patients with skin diseases or burn injuries. To address these limitations, a concerted effort has been to develop non‐contact methods leveraging frequency‐modulated continuous‐wave multiple‐input multiple‐output radar systems. Recent studies have illustrated the sensitivity of the phase component of received signals to micro‐motion, presenting a promising avenue for effective heart rate estimation. However, existing literature predominantly focuses on single‐antenna setups, overlooking the potential benefits offered by multiple‐input multiple‐output systems, which provide diverse channels with varying precision levels. This correspondence introduces a novel phase extraction model grounded in the argument of the analytic signal derived from both in‐phase and quadrature channels. Furthermore, leveraging the normal equation, we establish the feasibility of optimizing weights assigned to individual virtual antennas to achieve a robust approximation of ground truth data.

Evading the strength and toughness trade-off dilemma in Lu2Si2O7 environmental barrier coatings via micro-nano reinforcement

Lu2Si2O7 nanostructured environmental barrier coating was prepared using as–synthetic Lu2Si2O7 feedstock via atmospheric plasma spraying. The structure and mechanical performances of Lu2Si2O7 coatings were characterized in detail. Results indicate that nanostructured Lu2Si2O7 coating exhibits a bi-modal microstructure, lamella structure and unmelted particles. The phase components of nanostructured Lu2Si2O7 coatings consist of β-Lu2Si2O7 and a small number of X2-Lu2SiO5. Furthermore, the nanohardness and elastic modulus of Lu2Si2O7 coatings have the characterization of bi-modal properties via Weibull analysis, i.e., the large Weibull modulus and the small Weibull modulus represent molten lamella structure and unmelted particles, respectively. Meanwhile, the fracture toughness of nanostructured Lu2Si2O7 coatings is superior to conventional Lu2Si2O7 coatings, and the adhesion strength of Lu2Si2O7 coatings is about 22.6 MPa by pull-extend test. Results of research are helpful for the design and preparation of advanced thermal spray coating.

Sandplay Therapy and Active Imagination: What Are the Similarities and Differences? Reflections about Jung's Writings on Active Imagination.

Jung stated that active imagination is a fundamental component of the second phase of an analysis that can continue even outside the analytic setting. Since it can be conveyed through various expressive techniques, such as writing, drawing, and painting, it is possible to argue that all forms of psychotherapy based on art (e.g., poetry, dance, and theater) originate from Jung's contribution about active imagination. This paper focuses on Sandplay Therapy as one of the forms of expression rooted in active imagination. Apart from some critical differences between the two analytic processes (e.g., active imagination is usually prompted in the last phase of the analysis, while Sandplay Therapy might be used since the first sessions), there are several convergences. Among the principal analogies, consciousness lends its expressive means to the unconscious, which decides what to depict. Also, the resulting image is determined from both the consciousness and the unconscious and is related to the person's conscious situation. Finally, I suggest that Sandplay Therapy-aside from contributing to the subsequent development of active imagination itself (as suggested by Dr. Carducci)-might also be used to practice active imagination in a "facilitated" and protected setting. It would help let the unconscious come up while creating the image in the sandtray, and it fosters the confrontation between the unconscious and the consciousness through the contemplation of the image in the sandtray.

Multi-scale entropy assessment of magnetoencephalography signals in schizophrenia

Schizophrenia is a severe disruption in cognition and emotion, affecting fundamental human functions. In this study, we applied Multi-Scale Entropy analysis to resting-state Magnetoencephalography data from 54 schizophrenia patients and 98 healthy controls. This method quantifies the temporal complexity of the signal across different time scales using the concept of sample entropy. Results show significantly higher sample entropy in schizophrenia patients, primarily in central, parietal, and occipital lobes, peaking at time scales equivalent to frequencies between 15 and 24 Hz. To disentangle the contributions of the amplitude and phase components, we applied the same analysis to a phase-shuffled surrogate signal. The analysis revealed that most differences originate from the amplitude component in the δ, α, and β power bands. While the phase component had a smaller magnitude, closer examination reveals clear spatial patterns and significant differences across specific brain regions. We assessed the potential of multi-scale entropy as a schizophrenia biomarker by comparing its classification performance to conventional spectral analysis and a cognitive task (the n-back paradigm). The discriminative power of multi-scale entropy and spectral features was similar, with a slight advantage for multi-scale entropy features. The results of the n-back test were slightly below those obtained from multi-scale entropy and spectral features.

Monoclonal whole IgG impairs both fibrin and thrombin formation: hemostasis and surface plasmon resonance studies.

Monoclonal gammopathies frequently associate with hemostatic alterations. Thrombotic events occur with high incidence particularly upon treatment, while in rarer cases hemorrhagic diathesis can be observed. Thepathology of these tendencies could be caused by thrombocytopenia or hyperviscosity burden of circulating monoclonal antibodies. Studies also suggest interference ofmonoclonal antibodies with primary hemostasis. We isolated monoclonal whole IgG paraproteins from two myeloma patients to observe their effect on thrombin formation and fibrin polymerization. Monoclonal whole IgG was prepared from sera of two newly diagnosed untreated multiple myeloma patients and control normal plasma samples. Fibrin formation was measured using thrombin time and dilute prothrombin time tests and thrombin formation was detected with a fluorimetric thrombin generation assay. In addition, molecular interactions were investigated by surface plasmon resonance (SPR). Thrombin time was prolonged upon addition of monoclonal IgG even at 30 g/L by 12 %, increasing up to 36 % at 60 g/L concentration. Dilute prothrombin time was prolonged by 20 % even at 30 g/L. Thrombin generation assay indicated an impairment in thrombin formation at the presence of monoclonal IgG compared to polyclonal at equivalent concentration. By an SPR assay we determined that both clonality IgG preparations interacted with fibrinogen, however interaction with human thrombin was only detected with monoclonal immunoglobulins (KD=1.03×10-7 M). Here we provide evidence that isolated monoclonal whole IgG from myeloma patients can impair both fibrin and thrombin formation and we demonstrate by SPR assay that it interacts with components of the final phase of the coagulation system.

Effects of slag on mechanical and microstructural properties of iron-rich phosphoaluminate cement subjected to high temperature oil well environment

Iron-rich phosphoaluminate cement (shortened as PAC) exhibits excellent high temperature resistance characteristic, enabling it to withstand the ultrahigh temperatures required for the in situ combustion (ISC) of heavy oil. The addition of slag could influence its high temperature resistance by altering its hydration products. Hence the thickening time, physical properties, phase components and microstructure of PAC with slag that were subjected to different high temperature environment (315, 550 and 800 °C) were investigated deeply in this paper. The experimental analysis results revealed that PAC had better high temperature resistance than CAC with and without slag. The addition of slag improved effectively the high temperature resistance of PAC. The influencing mechanism of slag were as follows. C2ASH8 formed at 50 °C inhibited the conversion of C(A,P)H10 to C3AH6. C2AS3H, C3AS2H2 and C3(Fe,Al)S3 formed at 315 °C alleviated the rapid release of the compound water. The phase Ca5(PO4)3OH and C2AS was stable in the range of 550–800 °C. In addition, the capillary pore structure of PAC was optimized. Therefore, PAC with slag had the potential to be used for high temperature oil well cementing.

PH-switchable hydrophobic deep eutectic solvents for sustainable recycling extraction of high oily waste

The accumulation of oily waste increases annually with the growth in crude oil demand. Its toxicity and high heating value present both opportunities and challenges for treatment technologies. In recent years, the emergence of hydrophobic deep eutectic solvents (HDES) has promoted advancements in low-toxicity extraction processes. Leveraging the advantages of HDES and addressing the challenges posed by real oily sawdust (with a 67.9 % oil content), this study presents a novel green HDES solvent composed of ethyl maltol and fatty acids, accompanied by a corresponding extraction process. At a low temperature of 60 °C, the process achieved impressive results: an oil extraction efficiency close to 86.3 %, a dehydration rate exceeding 92.2 %, and a heavy metal removal rate ranging from 15 % to 75 %. In the exploration of solvents recycling, pH-switching facilitated the deprotonation and protonation of phenol-fatty acid HDES, promoting effective recovery of the oil phase. Even after 5 cycles, the oil extraction rate could still be maintained above 75 %. It is worth noting that the regenerated HDES exhibited greater selectivity for extracting light oil after multiple uses. The total ratio of saturated and aromatic hydrocarbons reached approximately 81.7 %, significantly enhancing the value of the recovered oil. Integrating systematic characterization with the extraction performance, as well as the variation in recovered oil phase components, highlighted the multifaceted effects of introducing ethyl maltol. Specifically, this effect is demonstrated in its ability to enhance the oil phase’s solubility by regulating the intermolecular spacing of HDES, and to impede the dissolution of heavy oil into its gaps by optimizing the local zone through the formation of complexes with HDES and heavy metals.

Fabrication and Stability Improvement of Monoglyceride Oleogel/Polyglycerol Polyricinoleate-Stabilized W/O High Internal Phase Pickering Emulsions.

To decrease the lipid content in water-in-oil (W/O) emulsions, high internal phase Pickering W/O emulsions (HIPPE) were fabricated using magnetic stirring using a combination of monoglyceride (MAG) oleogel and polyglycerol polyacrylate oleate (PGPR) as stabilizers. Effects of MAGs (glyceryl monostearate-GMS, glycerol monolaurate-GML and glycerol monocaprylate-GMC) and internal phase components on the formation and properties of HIPPEs were investigated. The results showed that milky-white stabilized W/O HIPPE with up to 85 wt% aqueous phase content was successfully prepared, and the droplet interfaces presented a network of MAG crystals, independent of the MAG type. All HIPPEs exhibited great stability under freeze-thaw cycles but were less plastic. Meanwhile, GML-oleogel-based HIPPEs had larger particle size and were less thermal stable than GMS and GMC-based HIPPEs. Compared to guar gum, the internal phase components of sodium chloride and sucrose were more effective in reducing the particle size of HIPPEs, improving their stability and plasticity, and stabilizing them during 100-day storage. HIPPEs presented great spreadability, ductility and plasticity after whipping treatment. This knowledge provides a new perspective on the use of oleogels as co-stabilizers for the formation of W/O HIPPEs, which can be used as a potential substitute for creams.

Influence of the Isothermal Transformation Temperature on the Structure and Properties of Low-Carbon Steel

Purpose. The study is aimed at evaluating the effect of the isothermal transformation temperature on the structure and properties of low-carbon steel. Methodology. The material for the study was a 3 mm diameter wire made of mild steel with the following chemical composition: 0.21% C, 0.47% Mn, 1.2% Si, 0.1% Cr, 0.03% S, 0.012% P. The 0.3 m long wire samples were subjected to austenitizing at 920 °C for 8...9 min, after which they were held isothermally for 11 min at temperatures of 650...200 °C, followed by cooling in air. The strength, plastic properties, and strain hardening coefficient were determined from the analysis of tensile curves. Findings. It was found that a decrease in the temperature of isothermal transformation, starting from 450...400 °C, increases the amount of Widmannstätten ferrite due to the disappearance of polyhedral ferrite grains. At the same time, the number of areas with locally located dispersed cementite particles similar to pearlite colonies increases, and bainite crystals appear. Against the background of a sharp decrease in the strain hardening coefficient in the range of 450...400 °C, the ability of the bainite phase to undergo plastic deformation should be considered one of the reasons for the delay in density reduction. Originality. The effect of steel hardening with a decrease in the pearlite transformation temperature is based on the grinding of ferrite grains, an increase in the amount of Widmannstätten ferrite, and the dispersion of pearlite colonies. The strengthening effect of steel with a bainite structure is based on an increase in the degree of supersaturation of the solid solution with carbon atoms and dispersion hardening by particles of the carbide phase. Practical value. The optimal structural state of steel intended for the manufacture of such critical elements as a support beam, railroad car bogie, etc. is a mixture of phase components with different dispersion and morphology, and their quantitative ratio is determined by the operating conditions of a particular product.

Organization of the Reserve Pool of Synaptic Vesicles in Nerve Terminals Lacking Protein Liquid Phase Components

Organization of the Reserve Pool of Synaptic Vesicles in Nerve Terminals Lacking Protein Liquid Phase Components

Sustainable analytical method for determination of bioactive compounds in solid oral formulations (capsules and tablets) containing green tea (Camellia sinensis) marketed in Brazil

This study presents the development of a sustainable analytical method using high-performance liquid chromatography (HPLC) for determination and quantification of bioactive compounds in Herbal Dietary Supplements (HDS) solid oral formulations containing green tea (Camellia sinensis). Four compounds [gallic acid, (+)-catechin, caffeine and caffeic acid] were determined in fifteen HDS samples (capsules and tablets) containing green tea marketed in Brazil. After optimizing the extraction process using factorial planning and response surface analysis, it was possible to develop the method. Methanol and acetic acid (0.25%) were components of the mobile phase, showing it as a more sustainable alternative to the use of acetonitrile. The samples evaluated demonstrated a lack of standardization in the concentrations (in mg g−1) of the chemical markers studied gallic acid (<LOD to 1.39), (+)-catechin (<LOD to 13.8), caffeine (<LOQ to 22) and caffeic acid (<LOD to 1.7). This concern has driven significant scientific research on the topic. The chromatographic method proved to be effective, sensitive and robust for qualification and quantification of the 4 chemical markers studied. This study found variations in the levels of chemical markers in HDS containing green tea sold in Brazil. Therefore, it can contribute to the regulation and quality control of these solid oral products (capsules and tablets) containing this plant.