Unveiling the potent effect of vitamin D: harnessing Nrf2/HO-1 signaling pathways as molecular targets to alleviate urban particulate matter-induced asthma inflammation.

BACKGROUND: Asthma is the most common allergic disease characterized by an inflammatory response in the airways. Mechanismly, urban particulate matter (PM) is the most widely air pollutant associated with increased asthma morbidity and airway inflammation. Current research found that vitamin D is an essential vitamin with anti-inflammatory, antioxidant and other medical efficacy. Inadequate or deficient vitamin D often leads to the pathogenesis and stability of asthma. NGF exacerbates airway inflammation in asthma by promoting smooth muscle cell proliferation and inducing the Th2 immune response. Activation of the Nrf2/HO-1 signaling pathway can exert a protective effect on the inflammatory response in bronchial asthma. However, the specific mechanism of this pathway in PM-involved asthmatic airway smooth muscle cells remains unclear. METHODS: Mice were sensitized and challenged with Ovalbumin (OVA) to establish an asthma model. They were then exposed to either PM, vitamin D or a combination of both, and inflammatory responses were observed. Including, acetylcholine stimulation at different concentrations measured airway hyperresponsiveness in mice. Bronchoalveolar lavage fluid (BALF) and serum were collected for TNF-α, IL-1ß, IL-6, and Nerve growth factor (NGF) analysis. Additionally, lung tissues underwent histopathological examination to observe alveolar structure and inflammatory cell infiltration. Specific ELISA kits were utilized to determine the levels of the inflammatory factors TNF-α, IL-1ß, IL-6, and Nerve growth factor (NGF). Nrf2/HO-1 signaling pathways were examined by western blot analysis. Meanwhile, we constructed a cell system with low HO-1 expression by lentiviral transfection of airway smooth muscle cells. The changes of Nrf2, HO-1, and NGF were observed after the treatment of OVA, PM, and Vit D were given. RESULTS: The in vivo results showed that vitamin D significantly alleviated pathological changes in lung tissue of PM-exposed mice models. Mechanismly, vitamin D decreased substantial inflammatory cell infiltration in lung tissue, as well as the number of inflammatory cells in BALF. Furthermore, vitamin D reduced the heightened inflammatory factors including of TNF-α, IL-1ß, IL-6, and NGF caused by PM exposure, and triggered the activity of nucleus Nrf2 and HO-1 in PM-exposed asthmatic mice. Notably, knockdown HO-1 weakens the Vitamin D- mediated inhibition to pollution toxicity in asthma. Importantly, in vitro experiments on OVA-stimulated mice airway smooth muscle cells, the results showed that OVA and PM, respectively, reduced Nrf2/HO-1 and increased NGF's expression, while vitamin D reversed the process. And in the HO-1 knockdown cell line of Lenti-si-HO-1 ASMCs, OVA and PM reduced Nrf2's expression, while HO-1 and NGF's expression were unchanged. CONCLUSIONS: The above results demastrate that vitamin D downregulated the inflammatory response and the expression of NGF by regulating the Nrf2/HO-1 signaling pathways in airway smooth muscle cells, thereby showing potent anti-inflammatory activity in asthma.

Advanced active polymer probe for near-field optics.

We report on a novel, to the best of our knowledge, active probe for scanning near-field optical microscopy (SNOM). A fluorescent nanosphere, acting as the secondary source, is grafted in an electrostatic manner at the apex of a polymer tip integrated into the extremity of an optical fiber. Thanks to the high photostability and sensitivity of the secondary source, the near-field interaction with a gold nanocube is investigated. It is shown that the spatial resolution is well defined by the size of the fluorescent nanosphere. The polarization-dependent near-field images, which are consistent with the simulation, are ascribed to the local excitation rate enhancement. Meanwhile, measurement of the distance-dependent fluorescence lifetime of the nanosphere provides strong evidence that the local density of states is modified so that extra information on nano-emitters can be extracted during near-field scanning. This advanced active probe can thus potentially broaden the range of applications to include nanoscale thermal imaging, biochemical sensors, and the manipulation of nanoparticles.

Hexafluorobutanol primary alcohol ethoxylate-based supramolecular solvent formation and their application in direct microextraction of malachite green and crystal violet from lake sediments.

A new type of hexafluorobutanol (HFB) primary alcohol ethoxylate (AEO)-based supramolecular solvent (SUPRAS) with density higher than water was prepared for the first time. HFB acted as AEO micelle-forming agent and density-regulating agent for SUPRAS formation. The prepared SUPARS was applied as extraction solvent for vortex-assisted direct microextraction of malachite green (MG) and crystal violet (CV) from lake sediment followed by high-performance liquid chromatographic determination. In the present work, SUPRASs prepared from AEO with different carbon chains as the amphiphiles and various coacervation agents were investigated. SUPARS formed from MOA-3 and HFB provided better extraction efficiency in comparison with other SUPRASs. Parameters influencing the extraction recovery of target analytes including the type and volume of AEO, volume of HFB, and vortex time were investigated and optimized. Under optimized conditions, linearity in the range of 2.0-400 µg g-1 for MG and 2.0-500 µg g-1 for CV with a correlation coefficient higher than 0.9947 was obtained. Limits of detection of 0.5 µg g-1 and relative standard deviations in the range of 0.9-5.8% were obtained. Compared to conventional extraction techniques for analysis of analytes in solid samples, the proposed method reduced sample usage and eliminated a primary extraction process by using a toxic organic solvent. The proposed method is simple, fast, and green and can be used for the analysis of target analytes in solid samples.

Extraction and isolation of diphenylheptanes and flavonoids from Alpinia officinarum Hance using supercritical fluid extraction followed by supercritical fluid chromatography.

In this paper, an off-line combination method of supercritical fluid extraction and supercritical fluid chromatography was developed for the selective extraction and isolation of diphenylheptanes and flavonoids from Alpinia officinarum Hance. The enrichment of target components was successfully achieved using supercritical fluid extraction with the following conditions (8% ethanol as co-solvent at 45°C and 30 MPa for 30 min). Taking full advantage of the complementarity of supercritical fluid chromatography stationary phases, a two-step preparative supercritical fluid chromatography strategy was constructed. The extract was firstly divided into seven fractions on a Diol column (250 × 20 mm internal diameter, 10 µm) within 8 min by gradient elution increasing from 5% to 20% modifier (methanol) at 55 ml/min and 15 MPa. Then the seven fractions were separated by using a 1-AA or a DEA column (250 × 19 mm internal diameter, 5 µm) at 50 ml/min and 13.5 MPa. This two-step strategy showed superior separation ability for structural analogs. As a result, seven compounds, including four diphenylheptanes and three flavonoids with high purity, were successfully obtained. The developed method is also helpful for the extraction and isolation of other structural analogs of traditional Chinese medicines.

Resilience, coping style, and COVID-19 stress: effects on the quality of life in frontline health care workers.

The aims of the study were to assess the contribution of resilience, coping style, and COVID-19 stress on the quality of life (QOL) in frontline health care workers (HCWs). The study was a cross-sectional surveyperformed among 309 HCWs in a tertiaryhospital during the outbreak of COVID-19 in China. Data were collected through an anonymous, self-rated questionnaire, including demographic data, a 10-item COVID-19 stress questionnaire, Generic QOL Inventory-74, Connor-Davidson Resilience Scale, and the Simplified Coping Style Questionnaire. Hierarchical regression was used to analyse the relationship between the study variables and the QOL. Among the 309 participants, resilience and active coping were positively correlated with the QOL (P<0.001), whereas, working in confirmed case wards, COVID-19 stress, and passive coping were negatively correlated with the QOL (P<0.001). Resilience and the active coping were negatively correlated with COVID-19 stress (P<0.001). Resilience, coping style,and COVID-19 stressaccounted for 32%, 13%, and 8% of the variance in predicting the Global QOL, respectively. In conclusion, working in confirmed COVID-19 case wards and COVID-19 stress impaired the QOL in HCWs. Psychological intervention to improve the resilience and coping style, and reduce COVID-19 stress are important in improving the QOL and mental health of HCWs.

Preparation of new hydrophobic deep eutectic solvents and their application in dispersive liquid-liquid microextraction of Sudan dyes from food samples.

In this work, a new generation of hydrophobic deep eutectic solvents (DESs) was prepared using eugenol (as hydrogen bond donor) and benzyltriethylammonium bromide, benzyltributylammonium bromide, benzyltriethylammonium chloride and benzyltributylammonium chloride (as hydrogen bond acceptor) in different molar ratios. These DESs were applied to vortex-assisted dispersive liquid-liquid microextraction of Sudan dyes from food samples, followed by high-performance liquid chromatographic determination. The influencing parameters, including the type of DES, amount of DES, extraction time, solution pH and salt addition, were investigated and optimized. Under the optimized conditions, a linear range of 2-1000 ng mL-1 with determination coefficients of <0.999 was obtained. Limits of detection and limits of quantification were in the range of 0.5 to 1 ng mL-1 and 2 to 3 ng mL-1, respectively. The proposed method was successfully used in the determination of Sudan dyes in chili sauce, chili powder and ketchup, and satisfactory recoveries of between 89.9 and 119.3% were obtained, with relative standard deviations in the range of 0.1-6.8%. The proposed method is simple, green and efficient, and can be applied to determine Sudan dyes in complex matrices.

IRF4 and STAT3 activities are associated with the imbalanced differentiation of T-cells in responses to inhalable particulate matters.

BACKGROUND: Particulate Matter (PM) is known to cause inflammatory responses in human. Although prior studies verified the immunogenicity of PM in cell lines and animal models, the effectors of PM exposure in the respiratory system and the regulators of the immunogenicity of PM is not fully elucidated. METHODS: To identify the potential effector of PM exposure in human respiratory system and to better understand the biology of the immunogenicity of PM, We performed gene-expression profiling of peripheral blood mononuclear cells from 171 heathy subjects in northern China to identify co-expressed gene modules associated with PM exposure. We inferred transcription factors regulating the co-expression and validated the association to T-cell differentiation in both primary T-cells and mice treated with PM. RESULTS: We report two transcription factors, IRF4 and STAT3, as regulators of the gene expression in response to PM exposure in human. We confirmed that the activation of IRF4 and STAT3 by PM is strongly associated with imbalanced differentiation of T-cells in the respiratory tracts in a time-sensitive manner in mouse. We also verified the consequential inflammatory responses of the PM exposure. Moreover, we show that the protein levels of phosphorylated IRF4 and STAT3 increase with PM exposure. CONCLUSIONS: Our study suggests the regulatory activities of IRF4 and STAT3 are associated with the Th17-mediated inflammatory responses to PM exposure in the respiratory tracts, which informs the biological background of the immunogenicity of particulate matters.

Suicidal ideation among the hypertensive individuals in Shandong, China: a path analysis.

BACKGROUND: Although massive studies have explored the risk factors of suicidal ideation (SI), the prevalence of SI and its associated factors in the hypertensive individuals are largely unknown. This study aims to investigate the factors associated with SI in the hypertensive individuals. METHODS: Three thousand nine hundred eleven hypertensive individuals in Shandong, China were included in the analysis. SI was assessed by using a question from the NCS (National Comorbidity Survey). We used binary logistic regression analysis to explore the factors associated with SI, and path analysis to test the direct and indirect relationships between associated factors and SI among hypertensive patients. RESULTS: The prevalence of SI in the hypertensive individual was19.6%. Psychological distress had the greatest direct (ß = 0.640, p-value <0.01) and total effect (ß = 0.640, p-value <0.01) on SI. Other factors including comorbidity (ß = 0.090, p-value <0.01), gender (ß = 0.088, p-value <0.01), marital status (ß = - 0.037, p-value <0.01), economic status (ß = - 0.106, p-value <0.01), residence (ß = - 0.050, p-value <0.01), alcohol use (ß = 0.011, p-value <0.01), exercise (ß = - 0.114, p-value <0.01), hospitalization (ß = 0.041, p-value <0.01) only had indirect effects on SI. Psychological distress was a mediator between SI and those variables. CONCLUSION: A significant mediation effect of psychological distress on the associations between SI and some associated factors (i.e., economic status, comorbidity) was demonstrated.

Effects of particulate matter (PM) on childhood asthma exacerbation and control in Xiamen, China.

BACKGROUND: The short-term effects of particulate matter (PM) exposure on childhood asthma exacerbation and disease control rate is not thoroughly assessed in Chinese population yet. The previous toxic effects of PM exposure are either based on long-term survey or experimental data from cell lines or mouse models, which also needs to be validated by real-world evidences. METHODS: We evaluated the short-term effects of PM exposure on asthma exacerbation in a Chinese population of 3106 pediatric outpatientsand disease control rate (DCR) in a population of 3344 children using case-crossover design. All the subjects enrolled are non-hospitalized outpatients. All data for this study were collected from the electronic health record (EHR) in the period between January 1, 2016 and June 30, 2018 in Xiamen, China. RESULTS: We found that exposure to PM2.5 and PM10 within the past two weeks was significantly associated with elevated risk of exacerbation (OR = 1.049, p < 0.001 for PM2.5and OR = 1.027, p < 0.001 for PM10). In addition, exposure to PM10 was associated with decreased DCR (OR = 0.976 for PM10, p < 0.001). CONCLUSIONS: Our results suggest that exposure to both PM10 and PM2.5 has significant short-term effects on childhood asthma exacerbation and DCR, which serves as useful epidemiological parameters for clinical management of asthma risk in the sensitive population.

Germline and somatic variations influence the somatic mutational signatures of esophageal squamous cell carcinomas in a Chinese population.

BACKGROUND: Esophageal squamous cell carcinomas (ESCC) is the fourth most lethal cancer in China. Previous studies reveal several highly conserved mutational processes in ESCC. However, it remains unclear what are the true regulators of the mutational processes. RESULTS: We analyzed the somatic mutational signatures in 302 paired whole-exome sequencing data of ESCC in a Chinese population for potential regulators of the mutational processes. We identified three conserved subtypes based on the mutational signatures with significantly different clinical outcomes. Our results show that patients of different subpopulations of Chinese differ significantly in the activity of the "NpCpG" signature (FDR = 0.00188). In addition, we report ZNF750 and CDC27, of which the somatic statuses and the genetic burdens consistently influence the activities of specific mutational signatures in ESCC: the somatic ZNF750 status is associated with the AID/APOBEC-related mutational process (FDR = 0.0637); the somatic CDC27 copy-number is associated with the "NpCpG" (FDR = 0.00615) and the AID/APOBEC-related mutational processes (FDR = 8.69 × 10- 4). The burdens of germline variants in the two genes also significantly influence the activities of the same somatic mutational signatures (FDR < 0.1). CONCLUSIONS: We report multiple factors that influence the mutational processes in ESCC including: the subpopulations of Chinese; the germline and somatic statuses of ZNF750 and CDC27 and exposure to alcohol and tobacco. Our findings based on the evidences from both germline and somatic levels reveal potential genetic regulators of the somatic mutational processes and provide insights into the biology of esophageal carcinogenesis.

Silver-Catalyzed Radical Arylphosphorylation of Unactivated Alkenes: Synthesis of 3-Phosphonoalkyl Indolines.

A silver-catalyzed phosphorylation/cyclization cascade of N-allyl anilines was developed, allowing direct access to 3-phosphonoalkyl indolines, which were previously obtainable only via tedious procedures under harsh/toxic conditions. The unactivated double bond serves as the radical acceptor, whereas H-phosphonates or -phosphine oxides act as the radical precursor. This protocol features simple operation, broad substrate scope, and great exo selectivity, and a gram-scale synthesis could be readily carried out.

Air-assisted dispersive liquid-liquid microextraction based on a new hydrophobic deep eutectic solvent for the preconcentration of benzophenone-type UV filters from aqueous samples.

Deep eutectic solvents are considered as new and green solvents that can be widely used in analytical chemistry such as microextraction. In the present work, a new dl-menthol-based hydrophobic deep eutectic solvent was synthesized and used as extraction solvents in an air-assisted dispersive liquid-liquid microextraction method for preconcentration and extraction of benzophenone-type UV filters from aqueous samples followed by high-performance liquid chromatography with diode array detection. In an experiment, the deep eutectic solvent formed by dl-menthol and decanoic acid was added to an aqueous solution containing the UV filters, and then the mixture was sucked up and injected five times by using a glass syringe, and a cloudy state was achieved. After extraction, the solution was centrifuged and the upper phase was subjected to high-performance liquid chromatography for analysis. Various parameters such as the type and volume of the deep eutectic solvent, number of pulling, and pushing cycles, solution pH and salt concentration were investigated and optimized. Under the optimum conditions, the developed method exhibited low limits of detection and limits of quantitation, good linearity, and precision. Finally, the proposed method was successfully applied to determine the benzophenone-type filters in environmental water samples with relative recoveries of 88.8-105.9%.

The Relationship Between Difficulties in Daily Living and Suicidal Ideation Among Older Adults: Results From a Population-Based Survey in Shandong.

To date, few studies have examined the association between difficulties in activities of daily living (ADL) and suicidal ideation (SI) among the seniors in China. This study aims to explore this association among older adults in China. A total of 3313 older people (60+) were included in this study, and questionnaires were administered by face-to-face interview. In total, 4.2% of the participants reported SI. The mean score of ADL among older adults with SI (21.06 ± 10.92) was much higher than that in those without SI (16.13 ± 5.60). Multivariate analyses showed that some specific domains of ADL including using transport, medical care, and household activities were associated with SI even after we controlled the psychological conditions. An association was observed between difficulties in daily living and SI among older adults in China. Psychological interventions should be taken to prevent potential risk of suicide targeting the seniors with certain disabilities.

Does Hukou origin affect establishment of health records in migrant inflow communities? A nation-wide empirical study in China.

BACKGROUND: With the implementation of Chinese economic reform and rapid urbanization, policies and values surrounding migration have changed and given rise to unprecedented population mobility. This study is designed to examine the effect of Hukou origin on establishment of health records among internal migrants in China. METHODS: The data used for this study are from the 2015 National Internal Migrant Population Dynamic Monitoring Survey, covering 112,782 migrants nationwide. For continuous variables, the p value is calculated using Student t test; for categorical variables, the p value is calculated using chi-square test. Binary logistic regression with an enter method is employed to assess the association of establishment of health records with origin residence. RESULTS: About 35.1% of the migrant population has established health records in their inflow communities, with 37.4% established among those of urban origin and 34.8% established among those of rural origin. The establishment of health records is significantly higher among migrants of urban origin than among migrants of rural origin (OR = 1.057; 1.017-1.098). Our results also show that among populations of both rural and urban origin, inter-province migrants, along with migrants who are employers, have no plans for long-term residence, have no insurance, and have more family income less likely to establish health records. CONCLUSIONS: This study demonstrates that residence is associated with establishment of health records among the migrant population in China. Targeted policies should be made to improve the establishment of health records among migrants of both rural and urban origins.

Gender difference in utilization willingness of institutional care among the single seniors: evidence from rural Shandong, China.

BACKGROUND: Institutional care has become an urgent issue in rural China. Rural single seniors, compared with their counterparts, have lower income and are more vulnerable. Gender is also a significant factor determining long-term institutional care. This study is designed to examine the gender difference towards utilization willingness of institutional care among rural single seniors. METHODS: A total of 505 rural single seniors were included in the analysis. Binary logistic regression model was used to examine the gender difference towards utilization willingness for institutional care, and also to identify the determinants of the utilization willingness for institutional care among rural single male and female seniors. RESULTS: Our study found that about 5.7% rural single seniors had willingness for institutional care in Shandong, China. Single females were found to be less willing for institutional care than single males in rural areas (OR = 0.19; 95 CI 0.06-0.57). It's also found that psychological stress was associated with institutionalization willingness in both single males (P = 0.045) and single females (P = 0.013) in rural China. The rural single seniors who lived alone were found to be more willing for institutional care both in males (P = 0.032) and females (P = 0.002) compared with those who lived with children or others. CONCLUSIONS: This study found that there was a gender difference towards utilization willingness for institutional care among single seniors in rural China. Factors including psychological stress and living arrangements were determinants of institutionalization willingness both in single males and females. Targeted policies should be made for rural single seniors of different gender.

Rural-urban difference in the use of annual physical examination among seniors in Shandong, China: a cross-sectional study.

BACKGROUND: Regular physical examination contributes to early detection and timely treatment, which is helpful in promoting healthy behaviors and preventing diseases. The objective of this study is to compare the annual physical examination (APE) use between rural and urban elderly in China. METHODS: A total of 3,922 participants (60+) were randomly selected from three urban districts and three rural counties in Shandong Province, China, and were interviewed using a standardized questionnaire. We performed unadjusted and adjusted logistic regression models to examine the difference in the utilization of APE between rural and urban elderly. Two adjusted logistic regression models were employed to identify the factors associated with APE use in rural and urban seniors respectively. RESULTS: The utilization rates of APE in rural and urban elderly are 37.4% and 76.2% respectively. Factors including education level, exercise, watching TV, and number of non-communicable chronic conditions, are associated with APE use both in rural and urban elderly. Hospitalization, self-reported economic status, and health insurance are found to be significant (p < 0.05) predictors for APE use in rural elderly. Elderly covered by Urban Resident Basic Medical Insurance (URBMI) (p < 0.05, OR = 1.874) are more likely to use APE in urban areas. CONCLUSIONS: There is a big difference in APE utilization between rural and urban elderly. Interventions targeting identified at-risk subgroups, especially for those rural elderly, are essential to reduce such a gap. To improve health literacy might be helpful to increase the utilization rate of APE among the elderly.

Encoded error calibration for a coded aperture spectrometer based on deconvolution.

The principle of a 2D coded aperture spectrometer is described in this paper. The crosstalk of adjacent rows, which is caused by the optical system's point-spread function and the nonuniform illumination of the apertures, is the main source of the system decoded errors. Through the analysis of the effect of the crosstalk and nonuniform illumination on the decoded spectrum, the encoding matrix is modified. Based on the new encoding equation, an algorithm using Gold's deconvolution method is proposed to remove the crosstalk of adjacent rows. In the end, we evaluate the effect of this method through a series of contrast experiments.

Relationship between the presence of meaning in life and sleep quality: A moderated chain-mediation model.

Sleep is a vital component of health; however, sleep issues are particularly prominent among college students. Identifying protective factors for sleep among college students is of paramount importance. To investigate the mechanisms behind the association between the presence of meaning in life (PML) and sleep quality, we conducted two questionnaire surveys (separated by an interval of 6 months) with 5660 college students to collect longitudinal data. The results show that PML predicted sleep quality and that this relationship was influenced by the mediating effect of depression and the chain mediating effect of coping style and depression; further, the search for meaning in life played a moderating role in the chain mediation model. This study offers new theoretical perspectives on the protective factors of sleep quality and provides empirical insights useful for improving sleep health among college students.

Whole-genome shotgun sequencing unravels the influence of environmental microbial co-infections on the treatment efficacy for severe pediatric infectious diseases.

Background: The microbiome plays a pivotal role in mediating immune deviation during the development of early-life viral infections. Recurrent infections in children are considered a risk factor for disease development. This study delves into the metagenomics of the microbiome in children suffering from severe infections, seeking to identify potential sources of these infections. Aims: The aim of this study was to identify the specific microorganisms and factors that significantly influence the treatment duration in patients suffering from severe infections. We sought to understand how these microbial communities and other variables may affect the treatment duration and the use of antibiotics of these patients with severe infections. Method: Whole-genome shotgun sequencing was conducted on samples collected from children aged 0-14 years with severe infections, admitted to the Pediatrics Department of Xiamen First Hospital. The Kraken2 algorithm was used for taxonomic identification from sequence reads, and linear mixed models were employed to identify significant microorganisms influencing treatment duration. Colwellia, Cryptococcus, and Citrobacter were found to significantly correlate with the duration of clinical treatment. Further analysis using propensity score matching (PSM) and rank-sum test identified clinical indicators significantly associated with the presence of these microorganisms. Results: Using a linear mixed model after removed the outliers, we identified that the abundance of Colwellia, Cryptococcus, and Citrobacter significantly influences the treatment duration. The presence of these microorganisms is associated with a longer treatment duration for patients. Furthermore, these microorganisms were found to impact various clinical measures. Notably, an increase in hospitalization durations and medication costs was observed in patients with these microorganisms. In patients with Colwellia, Cryptococcus, and Citrobacter, we discover significant differences in platelets levels. We also find that in patients with Cryptococcus, white blood cells, hemoglobin, and neutrophils levels are lower. Conclusion: These findings suggest that Colwellia, Cryptococcus, and Citrobacter, particularly Cryptococcus, could potentially contribute to the severity of infections observed in this cohort, possibly as co-infections. These microorganisms warrant further investigation into their pathogenic roles and mechanisms of action, as their presence in combination with disease-causing organisms may have a synergistic effect on disease severity. Understanding the interplay between these microorganisms and pathogenic agents could provide valuable insights into the complex nature of severe pediatric infections and guide the development of targeted therapeutic strategies.

An improved subtraction model applied in supercritical fluid chromatography to characterise polar stationary phases.

Herein, an improved subtraction model was proposed to characterise the polar stationary phases in supercritical fluid chromatography (SFC). Fifteen stationary phases were selected, including two types of aromatic columns, Waters Torus and Viridis series columns, as well as silica and amino columns. Ethylbenzene and Torus 1-AA were defined as the reference solute and column, respectively. Identifying the interaction with the maximum contribution to retention in SFC separation and using it as the initial term is a key step in modelling. The dipole, or induced dipole interaction (θ'P), replaced the hydrophobic interaction (η'H) as the starting term. The improved model was expressed as logα=η'H+ß'A+α'B+κ'C+θ'P+ε'E+σ'S, where the term ε'E indicated that anion exchange interaction was intentionally supplemented. A 7-step modelling process, including bidirectional fitting and residual analysis, was proposed. The obtained column parameters had reasonable physical significance, with the adjusted determination coefficient (R2adj) greater than 0.999 and the standard error (SE) less than 0.029. Methodological validation was further performed using the other four columns and 12 solutes that were not involved in the modelling. The result revealed good predictions of solutes' retention, as demonstrated by R2adj from 0.9923 to 0.9979 and SE from 0.0636 to 0.1088. This study indicated the feasibility of using the improved subtraction model to characterise polar stationary phases in SFC, with the most crucial being the determination of an initial term, followed by the addition of a new descriptor and the selection of an appropriate reference column. The study expanded the application scope of the subtraction model in SFC, which will help gain an in-depth understanding of the SFC separation mechanism.