Readiness for practice in undergraduate nursing students during the COVID-19 pandemic: a cross-sectional study.

Background: The Coronavirus disease 2019 (COVID-19) pandemic negatively impacted nursing students' opportunity to gain experience through clinical placement, potentially threatening their readiness for practice and their clinical competence. The aim of this study was to explore whether and to what extent the third-year undergraduate nursing students perceived that their readiness for practice was impacted by changes to clinical placement and classroom learning implemented in response to the COVID-19 pandemic. Study design: Cross-sectional study. Methods: The study was conducted in a university of North-western Italy that provides nursing education across five sites. All sites stopped in-person classroom learning at the beginning of March 2020, but each site was free to decide whether to continue in-person clinical placement based on the local epidemiological situation. All 228 third-year nursing students who completed their degree by June 2020 were invited to participate. Data were collected via online questionnaire, which included the question "What impact do you think that COVID-19 safety measures employed by your nursing programme had on your readiness for practice?" Answers were given on a 5-point Likert scale (none, minimal, moderate, major, and severe). Explanatory variables were collected at the individual, nursing programme, and university site levels. Results: A total of 126 (response rate 55.3%) nursing students completed the questionnaire. Overall, 84 (66.7%) perceived that COVID-19 safety measures had a moderate to severe impact on their readiness for practice. These students often had lower grade point averages (p=0.037) and received no clinical placement during the pandemic (72.6% vs 90.5% of students who reported no or minimal impact, p=0.022). Average duration of third-year clinical placement was also lower among these students, though it was not statistically significant. No differences emerged at the university site level. Conclusions: Despite important advances in technology-based educational activities, clinical placement remains the best educational strategy to allow nursing students to feel prepared to work effectively during a pandemic.

Taste and Smell Disorders in COVID-19 Patients at a Local Healthcare Trust in Northern Italy: a Cross-Sectional Study.

Background: In Italy, since the beginning of the COVID-19 pandemic, patients testing positive for SARS-CoV-2 through nasopharyngeal swab have reported taste and smell alterations. As these symptoms are quite uncommon in other respiratory infections, their specificity and prevalence are useful features for the differential diagnosis of COVID-19. The objective was to describe taste and smell alterations in patients diagnosed with SARS-CoV-2 infection and to define the onset of those disorders during the clinical course of the disease. Study design: Cross-sectional study. Methods: This study was conducted on adult patients testing positive for SARS-CoV-2 infection through nasopharyngeal swab at a Local Healthcare Trust in Northern Italy between April 27th and May 27th, 2020. In order to investigate the clinical course, the onset of the first symptoms, smell and/or taste alterations, a phone-based questionnaire was administered during the programming of the second nasopharyngeal swab. Results: We recruited 168 patients; the mean age was 52 years old, and 94 (56.0%) were female. Among the 135 symptomatic patients, 87 (64.4%) reported taste and smell alterations. Patients with a mild clinical course showed the highest prevalence for taste and smell disorders (76.6%), which were also associated with a more benign clinical course of the disease (P = 0.0166). Furthermore, in 33 (37.9%) of these patients, changes in smell and taste perception appeared before the acute phase of the disease. Among the 14 patients with a severe clinical course of SARS-CoV-2 infection, 8 reported a variation of taste and smell perception before the hospitalization, with a median of 4 days (IQR 2-7). Conclusions: Smell and taste disorders can be listed among the first symptoms of SARS-CoV-2 infection and may anticipate the acute phase of the disease. Noteworthy, they seem to be associated with a more benign clinical course.

Could the human papillomavirus recombinant vaccine be a new valid approach in the management of ano-genital warts?

Abstract: In line with previous case-reports, the study conducted by Hoom Choi ascertained the effectiveness of the HPV vaccine as a promising approach in the therapeutic management of ano-genital warts. The uncertain length of time and the varying effectiveness of traditional treatments encourage a reduction in the use of them and the development of a therapeutic use of HPV-vaccination. While the efficacy, safety profile and effects of the HPV vaccination in preventing ano-genital warts is well-know, therapeutic HPV vaccination has not been evaluated in a Randomized Prospective Trial, to date, and has not received a formal approval and an off-label indication for the treatment of those lesions. For these reasons, RCTs or cohort studies are warranted.

Environmental asbestos exposure and clustering of malignant mesothelioma in community: a spatial analysis in a population-based case-control study.

BACKGROUND: Neighborhood exposure to asbestos increases the risk of developing malignant mesothelioma (MM) in residents who live near asbestos mines and asbestos product plants. The area of Casale Monferrato (Northwest Italy) was impacted by several sources of asbestos environmental pollution, due to the presence of the largest Italian asbestos cement (AC) plant. In the present study, we examined the spatial variation of MM risk in an area with high levels of asbestos pollution and secondly, and we explored the pattern of clustering. METHODS: A population-based case-control study conducted between 2001 and 2006 included 200 cases and 348 controls. Demographic and occupational data along with residential information were recorded. Bivariate Kernel density estimation was used to map spatial variation in disease risk while an adjusted logistic model was applied to estimate the impact of residential distance from the AC plant. Kulldorf test and Cuzick Edward test were then performed. RESULTS: One hundred ninety-six cases and 322 controls were included in the analyses. The contour plot of the cases to controls ratio showed a well-defined peak of MM incidence near the AC factory, and the risk decreased monotonically in all directions when large bandwidths were used. However, considering narrower smoothing parameters, several peaks of increased risk were reported. A constant trend of decreasing OR with increasing distance was observed, with estimates of 10.9 (95% CI 5.32-22.38) and 10.48 (95%CI 4.54-24.2) for 0-5 km and 5-10 km, respectively (reference > 15 km). Finally, a significant (p < 0.0001) excess of cases near the pollution source was identified and cases are spatially clustered relative to the controls until 13 nearest neighbors. CONCLUSIONS: In this study, we found an increasing pattern of mesothelioma risk in the area around a big AC factory and we detected secondary clusters of cases due to local exposure points, possibly associated to the use of asbestos materials.

Rendimiento del ASAS Health Index en pacientes con Espondiloartritis de la vida real / Performance of ASAS Health Index in real life spondyloarthritis patients

Introducción: El cuestionario "Assessment of Spondyloarthritis International Society Health Index" (ASAS-HI) fue desarrollado para medir de manera global la funcionalidad y el estado de salud en pacientes con espondiloartritis (EspA). Se han propuesto puntos de corte para determinar diferentes estados de salud que fueron poco evaluados en pacientes de la vida real. Objetivos: Describir el estado de salud medido por ASAS-HI en pacientes argentinos con EspA axial (EspAax) y periférica (EspAp) en la práctica diaria y evaluar los factores asociados al pobre estado de salud. Materiales y métodos: Estudio de corte transversal, analítico y multicéntrico. Se incluyeron consecutivamente pacientes con EspAax y EspAp según criterios ASAS, de 15 centros argentinos. Análisis estadístico: Se realizó estadística descriptiva, análisis bivariado y multivariado (regresión logística múltiple) para evaluar los factores asociados al pobre estado de salud (ASAS-HI ≥12). Para analizar la validez de constructo de la herramienta se realizó correlación de Spearman entre el ASAS-HI y otros parámetros de evaluación de la enfermedad. Resultados: Se incluyeron 274 pacientes con EspA, con una edad media de 49 (±14) años y una duración mediana de la enfermedad de 62 meses (p25-75: 24-135), 155 (56,6%) de los pacientes eran de sexo masculino, 129 pacientes (47%) con EspAax y 145 (52,9%) EspAp. Según el ASAS-HI 119 pacientes (43,4%) presentaban buen estado de salud, 117 (42,7%) tenían estado de salud moderado y 38 (13.9%) pobre estado de salud. En los pacientes con EspAp el valor de ASAS-HI mediano fue de 7 (p25-75: 3-10). El ASAS-HI correlacionó positivamente con: DAS28: rho: 0.5 (p<0.001) y HAQ: rho: 0.54 (p<0.001). La variable asociada de manera independiente con pobre estado de salud fue el DAS28 (OR: 1.9, IC95% 1.1-3.4, p: 0.029). En los pacientes con EspAax el valor de ASAS-HI mediano fue de 6 (p25-75: 2.75-10). El ASAS-HI mostró correlación con: BASDAI: rho: 0.7 (p<0.001), ASDAS-ERS: rho: 0.7 (p<0,001), ASQoL: rho: 0.8 (p<0.001), BASFI rho: 0.75 (p<0.001). La variable que se asoció de manera independiente a pobre estado de salud fue el ASDAS-ERS (OR 6.6, IC95% 2-22, p 0.002). Conclusión: Un pobre estado de salud se asoció independientemente a mayor actividad de la enfermedad en pacientes con EspAax y EspAp. El ASAS-HI correlacionó con otros parámetros de la enfermedad, lo que refuerza la validez de constructo de esta nueva herramienta.

Introduction: The "Assessment of Spondyloarthritis International Society Health Index" (ASAS-HI) questionnaire was developed to globally measure function and health status in patients with spondyloarthritis (SpA). Cut-off points have been proposed to determine different health states that were poorly evaluated in real-life patients. Objectives: To describe the health status measured by ASAS-HI in Argentine patients with axial SpA (AxSpA) and peripheral SpA (SpAp) in daily practice and to evaluate the factors associated with poor health. Materials and methods: Cross-sectional, analytical and multicenter study. Patients with SpAax and SpAp were consecutively included according to ASAS criteria, from 15 Argentine centers. Statistical analysis: Descriptive statistics, bivariate and multivariate analysis (multiple logistic regression) were performed to evaluate the factors associated with poor health status (ASAS-HI ≥12). To analyze the construct validity of the tool, Spearman correlation was performed between the ASAS-HI and other disease evaluation parameters. Results: 274 patients with SpA were included, with a mean age of 49 (± 14) years and a median duration of the disease of 62 months (p25-75: 24-135), 155 (56.6%) were male, 129 patients (47%) with AxSpA and 145 (52.9%) SpAp. According to the ASAS-HI, 119 patients (43.4%) had good health, 117 (42.7%) had moderate health and 38 (13.9%) had poor health. In patients with SpAp, the mean ASAS-HI value was 7 (p25-75: 3-10). The ASAS-HI positively correlated with: DAS28: rho: 0.5 (p <0.001) and HAQ: rho: 0.54 (p <0.001). The variable independently associated with poor health status was DAS28 (OR: 1.9, 95% CI 1.1-3.4, p: 0.029). In patients with AxSpA, the mean ASAS-HI value was 6 (p25-75: 2.75-10). The ASAS-HI showed correlation with: BASDAI: rho: 0.7 (p <0.001), ASDAS-ERS: rho: 0.7 (p <0.001), ASQoL: rho: 0.8 (p <0.001), BASFI rho: 0.75 (p <0.001). The variable that was independently associated with poor health was the ASDAS-ERS (OR 6.6, 95% CI 2-22, p 0.002). Conclusion: Poor health status was independently associated with higher disease activity in patients with AxSpA and SpAp. The ASAS-HI correlated with other parameters of the disease, which reinforces the construct validity of this new tool.

Tubulin binding potentially clears up Bortezomib and Carfilzomib differential neurotoxic effect.

Proteasome inhibitors (PIs) represent the gold standard in the treatment of multiple myeloma. Among PIs, Bortezomib (BTZ) is frequently used as first line therapy, but peripheral neuropathy (PN), occurring approximately in 50% of patients, impairs their life, representing a dose-limiting toxicity. Carfilzomib (CFZ), a second-generation PI, induces a significantly less severe PN. We investigated possible BTZ and CFZ off-targets able to explain their different neurotoxicity profiles. In order to identify the possible PIs off-targets we used the SPILLO-PBSS software that performs a structure-based in silico screening on a proteome-wide scale. Among the top-ranked off-targets of BTZ identified by SPILLO-PBSS we focused on tubulin which, by contrast, did not turn out to be an off-target of CFZ. We tested the hypothesis that the direct interaction between BTZ and microtubules would inhibit the tubulin alfa GTPase activity, thus reducing the microtubule catastrophe and consequently furthering the microtubules polymerization. This hypothesis was validated in a cell-free model, since BTZ (but not CFZ) reduces the concentration of the free phosphate released during GTP hydrolysis. Moreover, NMR binding studies clearly demonstrated that BTZ, unlike CFZ, is able to interact with both tubulin dimers and polymerized form. Our data suggest that different BTZ and CFZ neurotoxicity profiles are independent from their proteasome inhibition, as demonstrated in adult mice dorsal root ganglia primary sensory neurons, and, first, we demonstrate, in a cell free model, that BTZ is able to directly bind and perturb microtubules.

Men and women affected by Sars-CoV-2 pneumonia: same CT features but different outcome.

AIM: To compare the computed tomography (CT) features of Sars-CoV-2 pneumonia between the two sexes and among different age groups. MATERIALS AND METHODS: Consecutive patients (n=331) who presented to the emergency department and underwent chest CT and reverse transcription polymerase chain reaction (RT-PCR) with a time interval <7 days, which were subsequently found to be consistent with Sars-CoV-2 infection, were enrolled retrospectively. Two experienced radiologists evaluated the images in consensus, recording the number of pulmonary lobes with ground-glass opacities and with consolidation. A CT score was subsequently calculated based on the percentage involvement of each lobe. Clinical symptoms, comorbidities, and level of required hospitalisation were noted. In-hospital mortality was recorded and analysed via the Kaplan-Meier estimator. RESULTS: Males and females had the same age distribution. No statistically significant difference was found in the analysed CT features and in the CT score (p=0.31) between the sexes. More females were affected by two or more comorbidities (17.1% versus 7.5%, p=0.024), all comorbidities except diabetes were more prevalent in females. Women had a higher probability to be discharged home and a lower probability to be admitted to the intensive care unit (ICU; p=0.008), in-hospital mortality was inferior (13.5% versus 22%). CONCLUSION: Despite more comorbidities, women had lower hospital admission and mortality, which was independent of CT findings between both sexes.

Headache in immigrant patients: similarities and differences with Italian population.

Headache is one of the most common neurological diseases. It is well known that there are differences in the perception and in the management of pain in various populations. Immigrants represent a growing portion between neurology outpatients. We analyzed the epidemiological characteristic of headache in immigrants come to our attention, in comparison with Italians. Data collected included age at immigration, age of onset of headache, headache's type (HIS criteria), and psychiatric comorbidities. There were not substantial differences in the incidence of headache subtypes: migraine was the most frequent diagnosis in both groups, followed by tension-type headache. The incidence of depression was similar, while anxiety was significantly less frequent in immigrants. Studies on neurological diseases in immigrants are few. The data available seem to show no differences in the incidence, but rather in treatment. Our study confirms the evenness of two populations, local and foreign, afferent in a Headache Unit, according to the single similar study, except for anxiety, maybe related to language difficulties or cultural background.

Prevalence of Polysubstance Abuse and Dual Diagnosis in Patients Admitted to Alcohol Rehabilitation Units for Alcohol-Related Problems in Italy: Changes in 15 Years.

AIMS: Alcohol abuse has long been known as a disease with social and economic burden to society. Given the complex nature of alcohol treatment, it is worthwhile to examine the change over time of patients admitted to residential alcohol abuse rehabilitation units. METHODS: The data were collected from two Italian projects on alcoholics performed in the mid-1990s (ASSALT) and in 2009 (CORRAL), respectively. Categorical variables were considered in terms of absolute and relative frequencies. Comparisons of relative frequencies between groups were assessed by means of Fisher's exact test. Mixed logistic regression models were fitted to CORRAL data to identify the predictors of the probability of being a polysubstance abuser or having a dual diagnosis. The association estimates were reported as adjusted odds ratios and relative 95% confidence intervals. RESULTS: Compared to the mid-1990s, in 2009 patients were older (P= 0.0003), with a higher level of education (P= 0.0204), with fewer comorbidities (liver disease except cirrhosis, P < 0.0001; polyneuropathy, P= 0.0001), more frequently polysubstance abusers (P < 0.0001), affected by dual diagnosis (P < 0.0001). In 2009, the probability of being a polysubstance abuser was higher in younger and in patients with dual psychiatric diagnosis. Female gender and polysubstance abuse were positively associated to the probability of being affected by dual psychiatric diagnosis. CONCLUSIONS: The increment of patients admitted to residential programs for alcohol dependence with polysubstance abuse and/or dual psychiatric diagnoses suggests the need to pay more attention to both psychological/psychiatric interventions and internal medicine/physical rehabilitation. SHORT SUMMARY: The results of this study suggest that further research is needed to identify the best treatment strategy that is safe and effective for the new population of alcoholics.

NMR analysis of budding yeast metabolomics: a rapid method for sample preparation.

Here we propose the optimization of a rapid and reproducible protocol for intracellular metabolite extraction from yeast cells and their metabolic profiling by (1)H-NMR spectroscopy. The protocol reliability has been validated through comparison between the metabolome of cells in different phases of growth or with different genetic backgrounds.

From cancer metabolism to new biomarkers and drug targets.

Great interest is presently given to the analysis of metabolic changes that take place specifically in cancer cells. In this review we summarize the alterations in glycolysis, glutamine utilization, fatty acid synthesis and mitochondrial function that have been reported to occur in cancer cells and in human tumors. We then propose considering cancer as a system-level disease and argue how two hallmarks of cancer, enhanced cell proliferation and evasion from apoptosis, may be evaluated as system-level properties, and how this perspective is going to modify drug discovery. Given the relevance of the analysis of metabolism both for studies on the molecular basis of cancer cell phenotype and for clinical applications, the more relevant technologies for this purpose, from metabolome and metabolic flux analysis in cells by Nuclear Magnetic Resonance and Mass Spectrometry technologies to positron emission tomography on patients, are analyzed. The perspectives offered by specific changes in metabolism for a new drug discovery strategy for cancer are discussed and a survey of the industrial activity already going on in the field is reported.

New targets for antibacterial design: Kdo biosynthesis and LPS machinery transport to the cell surface.

Lipopolysaccharide (LPS), which constitutes the lipid portion of the outer leaflet of Gram-negative bacteria, is essential for growth. It is also responsible for the variety of biological effects associated with Gram-negative sepsis. Recent advances have elucidated the exact chemical structure of this highly complex macromolecule and much of the enzymology involved in its biosynthesis. Enzymes involved in LPS biogenesis are optimal targets for the development of novel therapeutics since they are sufficiently conserved among diverse, clinically-relevant bacteria and no analogue counterpart is present in humans. During the last thirty years a number of inhibitors of LPS biosynthesis have been developed: some of these compounds have antibacterial properties, while others show excellent in vitro activity and are undergoing further investigation. The main focus of this review will be the biology of LPS in bacteria summarizing the knowledge about structure and enzymatic catalysis, as well as chemical efforts towards the synthesis of inhibitors of the key enzymes involved in the biosynthesis of Kdo, toward the minimal conserve structure Kdo(2)-LipA. In addition, very recent advances in deciphering the molecular mechanisms of LPS transport to the cell surface, as a new target to develop novel antibacterials, will be reported. Future directions and perspectives will also be outlined.

Beta amyloid aggregation inhibitors: small molecules as candidate drugs for therapy of Alzheimer's disease.

The progressive production and subsequent accumulation of ß-amyloid (Aß), a proteolytic fragment of the membrane-associated amyloid precursor protein (APP), plays a central role in Alzheimer's Disease (AD). Aß is released in a soluble form that may be responsible for cognitive dysfunction in the early stages of the disease, then progressively forms oligomeric, multimeric and fibrillar aggregates, triggering neurodegeneration. Eventually, the aggregation and accumulation of Aß culminates with the formation of extracellular plaques, one of the morphological hallmarks of the disease, detectable post-mortem in AD brains. In this review we report the known structural features of amyloid peptides and fibrils, and we give an overview of all small molecules that have been found to interact with Aß aggregation. Deeper knowledge of the mechanism leading to amyloid fibrils along with their molecular structure and the molecular interactions responsible for activity of small molecules could supply useful information for the design of new AD therapeutic agents.

Hybrid aniline/silica xerogel cation adsorption and thermodynamics of interaction.

Aniline groups chemically immobilized on silica through the sol-gel process were employed to extract divalent nickel and manganese from aqueous solutions at room temperature. The maximum adsorption capacity of the xerogel was studied from adsorption isotherms using a batch technique. The isotherms obtained were adjusted following the Langmuir equation. The xerogel adsorbent appears to have better affinity for nickel than manganese. From calorimetric titration, thermodynamic data on cation/nitrogen basic atom interaction in the solid/liquid interface were determined. The enthalpic values, -0.46 +/- 0.02 and -.029 +/- 0.02 kJ mol(-1) for nickel and manganese, respectively, are in agreement with the low availability of the basic nitrogen atom on the aniline group and also the possible steric hindrance of the phenyl group bonded to nitrogen. However, thermodynamics indicated the existence of favorable conditions for such cation-nitrogen interactions.

Toxic effect caused on microflora of soil by pesticide picloram application.

The toxic effect of the herbicide picloram on the microbial population of a typical Brazilian red Latosol soil was studied in a series of microcalorimetric experiments. The activity of the soil was stimulated by the addition of 6.0 mg of glucose and 6.0 mg of ammonium sulfate, under 34.8% controlled moisture, to a 1.50 mg soil sample, at 298.15 +/- 0.02 K. The net thermal effect due to the addition of the picloram to the soil was determined by interpreting the power-time curves, which were recorded on the microcalorimeter. The total thermal effect evolved by the microorganisms was affected by the increasing doses of herbicide, and varied from 0 to 10.00 micrograms g-1. An increase in picloram exposure caused a decrease of the original thermal effect, reaching a null value above 20.89 micrograms of herbicide per gram of soil. The decreases of the thermal effect evolved by microorganisms and the increase of the lag phase period are associated with the death of the microbial population. The effects caused by picloram application in this typical Brazilian soil resulted in a strong effect on the soil microbial communities.

The effect of the herbicide diuron on soil microbial activity.

The inhibitory effect of the herbicide diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] on microbial activity in red Latosol soil was followed using microcalorimetry. The activity of the micro-organisms in 1.50 g of soil sample was stimulated by addition of 6.0 mg of glucose and 6.0 mg of ammonium sulfate under 35% controlled humidity at 298.15 (+/- 0.02) K. This activity was determined by power-time curves that were recorded for increasing amounts of diuron, varying from zero to 333.33 micrograms g-1 soil. An increase in the amount of diuron in soil caused a decrease of the original thermal effect, to reach a null value above 333.33 micrograms g-1 of herbicide. The power-time curve showed that the lag-phase period and peak time increased with added herbicide. The decrease of the thermal effect evolved by micro-organisms and the increase of the lag-phase period are associated with the death of microbial populations caused by diuron, which strongly affects soil microbial communities.

Application of calorimetry to microbial biodegradation studies of agrochemicals in oxisols.

Calorimetry was used to monitor the inhibitory effect caused by the bipyridynium diquaternary salts paraquat, diquat, and phosphamidon on microbial activity in a Red Latosol soil (Oxisol). The thermal effect was recorded on samples composed of 1.50 g of soil, 6.0 mg of glucose, 6.0 mg of ammonium sulfate, and different masses of an inhibitor ranging from zero to 8.00 mg, under a controlled moisture content of 35%. Thermal effects of each pollutant on the degradation curves of glucose in the soil were compared. Increasing amounts of the inhibitor caused a decrease in the thermal effect from -2234 to -1987 kJ mol(-1) for paraquat, -1670 to -1306 kJ mol(-1) for diquat, and -2239 to -589 kJ mol(-1) for phosphamidon. The last xenobiotic agent caused a significant inhibitory effect on the microbial activity of the soil. The results of relative efficiency, eta = deltaH/deltaH', referring to the enthalpic value with (deltaH) and without (deltaH') agrochemical in the soil, exhibited a significant correlation. From this correlation obtained for the ranges 2.00 to 8.00, 1.30 to 8.00, and 1.20 to 5.80 mg of the agrochemicals paraquat, diquat, and phosphamidon, respectively, the following eta values were calculated: 0.993 to 0.894, 0.668 to 0.522, and 0.896 to 0.236, respectively, during the degradation of glucose in the soil. The largest relative efficiency for paraquat implies that this agrochemical can be metabolized by microbial activity.

Development of new urea-functionalized silica stationary phases. Characterization and chromatographic performance.

New urea-functionalized silica stationary phases were prepared by a single-step surface modification through reaction of LiChrosorb Si100 (5 microm particle size) with a homologous series of alkoxysilanes, synthesized in our laboratory, with the general formula (CH3CH2O)3Si(CH2)3NHC(O)NH(CH2)nCH3, where n=4, 6 and 11. The modified silicas were characterized by elemental analysis of carbon and nitrogen, solid-state 29Si- and 13C-cross polarization magic angle spinning nuclear magnetic resonance and nitrogen adsorption isotherms at 77 K. Chromatographic evaluation of the three urea-functionalized silicas in 150x3.9 mm I.D. HPLC columns was carried out by the separation of a test mixture composed of uracil, acetophenone, benzene, toluene and naphthalene, using acetonitrile-water as mobile phase. These new stationary phases, with embedded polar urea groups, are very promising when compared with amide phases prepared by the conventional two-step modification process. A single-step reaction process silica modification is better for obtaining a well-characterized and homogeneous modified surface.

Adsorption and preconcentration of 2,4-dichlorophenoxyacetic acid on a chemically modified silica gel surface.

The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), chemically anchored to a silica gel surface, was used to adsorb and preconcentrate the same herbicide from aqueous solutions at room temperature. From a series of adsorption isotherms adjusted to a modified Langmuir equation, the maximum number of moles adsorbed was calculated as 4.67 x 10(-5) mol g(-1), with the highest retention capacity at pH 5. This modified silica gel was used in a column for preconcentrating trace levels of 2,4-D. The preconcentrated herbicide can be directly eluted with methanol with a recovery efficiency higher than 97%. The concentration factor was 8.33.

Ethyleneimine Anchored on Thiol-Modified Silica Gel Surface-Adsorption of Divalent Cations and Calorimetric Data.

Activated silica gel was previously modified by the silylant agent 3-mercaptopropyltrimethoxysilane. The organofunctionalized silica gel containing pendant groups ended with the -SH functions reacted with the three-member cyclic ethyleneimine molecules to yield the new ligand attaching sulfur and nitrogen basic centers available to complex cations. This final anchored surface adsorbs MX(2) (M=Co(2+), Ni(2+), Cu(2+), and X=Cl(-), NO(3)(-)) at 298+/-1 K. A considerable increase in adsorption capacity was observed for nitrate counteranions. This process of extraction was followed by the batch method and the order of the maximum capacities found was Ni(2+)>Cu(2+)>Co(2+) for both series of salts. The pendant immobilized groups-cation interaction processes showed exothermic enthalpies. Those values are more pronounced for chlorides, with the largest values obtained for cobalt. The calculated DeltaG values are in agreement with the spontaneity of the proposed reactions and the complexation is entropically favored. Copyright 2000 Academic Press.