Cr In Samples Research Articles

Esoteric CO adsorption by CuCl-NiCl2 embedded microporous MIL-101 (Cr)

A microporous MIL-101 (Cr) material with considerably high surface area of 3084 m2 g−1 and high total volume of 2.04 cm3 g−1 was used to host CuCl and NiCl2 species. Cu (II) was completely reduced to Cu (I) in the MIL-101 (Cr), while maintaining the Ni (II) in the host structures in order to effect the π-complexation between CO and the CuCl-NiCl2 MIL-101 (Cr) sample for improved CO adsorption. Ni (II) species were found to promote the reduction of Cu (II) and inhibit the agglomeration of copper crystals into large-size crystals, which enhanced the CO adsorption. The CuCl-NiCl2 MIL-101 (Cr) was capable of reaching a maximum CO adsorption of ca. ∼3.22 mmol g−1 and IAST-predicted CO/N2 selectivity of ca. ∼405. The sample was also regenerable for an extended period of time by a mere pressure swing without a post-treatment, making it a promising candidate for an industrial scale CO separation, enrichment and purification at ambient conditions.

Heavy Metals Analysis and Health Risk Assessment of Three Fish Species, Surface Water and Sediment Samples in Ogbaru Axis of River Niger, Anambra State, Nigeria

Human activities on environmental resources have negatively affected floras and faunas in maintaining fair balance. In this research study, selected heavy metals (Al, As, Cd, Cr, Cu, Fe, Hg, Pb, Ni, Zn) concentration in three fish species (Clarias gariepinus, Heterotis niloticus and Anguilla labiate), surface water and sediment samples in Ogbaru axis of River Niger, Anambra State, Nigeria. We evaluated the samples using atomic absorption spectrophotometer (AAS). The result of heavy metal analysis in fish samples showed that in decreasing order in Clarias garipinus in increasing order of Cu >Fe > Ni > Hg > Pb > Zn > As > Cd > Al > Cr, while Heterotis niloticus followed the order Cu > Zn > Fe > Ni > Pb > Cd > Al > As > Hg > Cr, and Anguilla labiate followed the pattern of Cu > Fe > Zn > Ni > Pb > Cd > Cr > As > Hg > Al. For surface water, As, Cd, Cr, Cu, Fe, Hg and Pb showed high concentration for the raining season compared to dry season, as Al, Ni and Zn were dominant during dry season, while sediment samples of Cr, Cu, Ni and Pb concentration in raining season were higher than dry season and vice versa for other As, Cd, Fe, Hg, Zn. Correlation matrices showed positive value showing that heavy metals were from a similar source with migration route and vice versa for negative correlation. Health and exposure risk assessment was conducted for carcinogenic and non-carcinogenic exposure in adults and children, where the cumulative cancer risk was within USEPA regulatory standard and cumulative hazard index were above 1 for adults (2.02) and children (4.93), implying that children are at risk of having adverse health issues compared to adults. Therefore, there is a need for regulatory advocacy and special care to mitigate anthropogenic release and safeguard the environment.

Concentrations and health risk assessment of industrial heavy metals pollution in groundwater in Ogun state, Nigeria

Wastes from industrial activities had great impact on water quality thereby limiting water usability for domestic purposes. Effluents discharge from industries, usually consist of undesirable concentrations of dissolved chemicals that percolate into the groundwater, thus constitute health risk to the populace. The present study assessed the distribution of heavy metals in groundwater and their health implications. Water samples were collected from hand-dug wells and boreholes in the Ota and Sagamu Industrial areas of Ogun state, Nigeria during the rainy and dry seasons. A total of 96 samples (48 samples per season) were collected and subjected to metals analysis (lead (Pb), cadmium (Cd), chromium (Cr), Nickel (Ni), Iron (Fe), Zinc (Zn), Copper (Cu), and Manganese (Mn) using standard methods. Descriptive and inferential statistics were used to analyze the data. The mean concentration of heavy metal in groundwater samples (both seasons) for Pb, Cd, Ni, Cr, Mn, Fe, Zn and Cu were 0.459, 0.006, 0.084, 0.016, 0.100, 0.709, 0.036, and 0.117 mg/L respectively at the Ota sampling location, while at Sagamu, the mean values of respective metals were 0.450, 0.012, 0.082, 0.016, 0.165, 0.663, 0.031, and 0.146 mg/L. The order of presence of the metals in groundwater was in the order Pb > Fe > Ni > Cr > Cd > Cu > Mn > Zn. The total hazard index (HI) of the metals in the groundwater samples showed a high risk across the different age groups. HI value (HI>1.0) demonstrates in general unfavorable non-cancer-causing impacts, in which the infants were at most serious risk. The cumulative Cancer Risk in the study areas shows a medium-extremely high risk for the analyzed metals. The calculated health risk index indicates major adverse effects on human health.

Influence of Cr and Fe doping on the structure, magnetic and optical properties of nano CuCo2O4

Nano CuCo2-xMxO4 (x = 0, 0.1, 0.2, M = Cr or Fe) samples were synthesized by hydrothermal method. Synchrotron x-ray diffraction data obtained for the samples were subjected to phase analysis and manifested a single-phase cubic spinel structure for Cr-doped samples, while for Fe-doped samples two phases were identified. Cation distribution and cell parameter (a) were obtained from Rietveld X-ray diffraction analysis. FTIR analysis affirmed the formation of the cubic spinel and the cation distribution obtained. The nano nature of the samples and the particle morphology were examined by high-resolution transmission electron microscope (HRTEM) with selected area electron diffraction (SAED). UV-diffuse reflectance revealed that all samples have two optical energy gaps. For all Fe doped samples, the optical band gaps decreased, while for Cr-content x = 0.1 the bandgaps increased then reduced for x = 0.2. Doped samples exhibited a blue or red shift depending on the kind and amount of the dopant ions. The PL intensity and the emitted colors depended on the kind and amount of the dopant ions. Magnetic measurements disclosed the paramagnetic nature of CuCo2O4, while a weak ferromagnetic is revealed for CuCo2-xCrxO4 and a ferromagnetic nature for CuCo2-xFexO4. Lowering the bandgap upon doping could make better mobility of lattice oxygen and enhancing the catalyst reducibility. Thus, the Cr and Fe-doped samples are expected to have better catalytic activity than the pristine one.

Local and Systemic Effects of Immune Checkpoint Blockade on Relapsed Myeloid Malignancies Following Allogeneic Hematopoietic Stem Cell Transplantation

Local and Systemic Effects of Immune Checkpoint Blockade on Relapsed Myeloid Malignancies Following Allogeneic Hematopoietic Stem Cell Transplantation

Analysis of Hedonic Test and Total Microbial Plate Numbers on Fish Siomay in Sorong City West Papua

One of the Indonesian snacks that can be found in all regions is fish siomay. fish siomay in the city of Sorong, there have been no reports on both the level of community preference and food security. The purpose of this study was to determine the level of community preference and the total number of microbial plate numbers snacks on fish siomay in the city of Sorong, West Papua. The method used in this research is descriptive method and experimental method. The results showed that for the hedonic test had a varying degree of preference for each sample, while the total number of plates did not exceed the maximum limit, then for the correlation of the two tests showed there was a relationship. The hedonic test results from the five samples show the best level of preference is the BS sample, and the EH sample, then the AQ sample, and the DS sample and the lowest preference level is the CR sample. While the sample of fish siomay scattered in the city of Sorong was suitable for consumption.

Effect of light quality and tissue origin on phenolic compound accumulation and antioxidant activity in Camellia japonica calli

In Camellia japonica callus culture, the effects of light quality on the accumulation of phenolic compounds were examined. To this end, the calli were cultured under three monochrome [white (W), red (R), and blue (B)] and two mixed [red/blue (RB) and red/green/blue (RGB)] light sources. After 4 weeks of culture, fresh and dry callus weights were determined, and phenolic content was analyzed using high-performance liquid chromatography. We also examined the effects of RGB light on calli derived from four origins (leaf: CL; root: CR; petal: CP; and ovary: CO). Total phenolic and flavonoid content and DPPH radical scavenging activity were highest in calli exposed to RB and RGB. Catechin was detected only in calli exposed to mixed light (RB and RGB). Interestingly, red pigmentation development in CL and CR calli after 2 weeks of culture and organogenic calli in CR and CP samples was observed. Furthermore, expression of the phenylalanine ammonia lyase and chalcone synthase genes was found to be higher in the CR line than in other lines, and total phenolic and flavonoid content was also higher in the CR and CP lines. The findings of the present study revealed that the accumulation of phenolics and flavonoids in callus tissue varies depending on light quality, which stimulates cell division, and may thus affect the proliferation and organogenesis of C. japonica callus. We also established that the effects of light on red pigment expression and the accumulation of bioactive compounds are dependent on the tissue origin of callus material.

Potential ecological and health risk assessment of different kiwifruit orchards in Qianjiang district, Chongqing city, China.

Heavy metal (HM) pollution in orchards is becoming serious in many countries, and some fruit HMs exceed the safety limits. In this study, contents of 8 HMs (Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn) in 5 kiwifruit orchard soils and the tissues (roots, twigs, leaves, fruits) of 4 kiwifruit varieties collected from Qianjiang district, Chongqing city, China, were determined. Seven HMs could meet priority protection class I, except for Cd with slightly poor environmental quality, including 4% and 53% of the samples belonging to the strict control class III and safe utilization class II, respectively. The potential ecological risk index (235.30) indicated that the HMs in the orchard soil were of medium potential ecological risk. The HMs' migration from rock to soil was very obvious. Kiwifruit was easy to accumulate Cu from soil and it had high Zn and Ni translocations to above-ground parts from roots. Compared with other tissues, HMs' concentrations in fruits were the lowest. From the perspective of human health, about 8.3% and 0.83% of the fruit samples for Cr and Cu exceeded the national maximum permissible levels, respectively; fortunately, the health risk index (HRI) values for all the fruit samples were within the safe limits.

Development and properties of dental Ti–Zr binary alloys

In this study, two medium Zr-containing Ti-based alloys with commercially pure titanium as control were systematically investigated to assess their potential biomedical application. After samples subjected to TMP and CR, it was found that the Zr addition significantly affected the microstructure, phase constitutions, mechanical properties and cytocompatibility. The microstructural results showed that increasing Zr concentrations resulted in more refined grains. Furthermore, Zr changed the phase constitution: CR Ti–20Zr was formed by the single α-phase while CR Ti–30Zr alloy was formed by the coexistence of α and deformation-induced FCC phases. The P-type FCC phase was dominant and more prone to occur than the B-type one. The mechanical tests demonstrated that the increasing Zr content led to a simultaneous increase in micro-hardness, strength and plasticity of CR samples due to the combined effects of solution strengthening, work hardening and the FCC phase. The SEM fractography indicated that the brittle fracture of CR Ti–20Zr due to deformation twins and ductile fracture of CR Ti–30Zr because of FCC phase. Furthermore, Ti–Zr alloys presented comparable cytocompatibility to the CP-Ti control based on cell viability, proliferation and intracellular O2− content of MSCs. Specifically, alkaline phosphatase activity in BMSCs were significantly higher for grain refined CR Ti–30Zr. Considering all these results, CR Ti–30Zr alloy exhibited the optimal comprehensive performance to be potential dental materials.

Recrystallization, grain growth and austenite formation in cold rolled steels during intercritical annealing

In this study, the effect of cold rolling on the recrystallization, grain growth of ferrite and the austenite formation in 0.14C–1.98Mn steel is studied extensively with different intercritical annealing times and temperatures.The starting sample is a 2,8mm thick ferritic, pearlitic sheet. Samples are cold rolled to either 1,12mm, 1,56mm or 1,92mm thicknesses. In order to see the changes in the microstructure below and within the intercritical temperatures, samples are annealed for 5min and 10min at different annealing temperatures and then quenched in water. Finally, the as-received sheet samples are annealed at the same temperatures for either 5 or 10min in order to be able to compare the microstructural and mechanical property differences between cold rolled and not rolled samples.It is found that medium cold reduced (45%CR) samples have the lowest tensile properties at the middle-intercritical annealing range due to faster recrystallization and grain growth of ferrite. The effect of recrystallization and recovery is most pronounced at the onset of the Ae1 temperatures for all the samples. Due to higher recrystallization temperature, reduction of yield and tensile strength of 30% CR samples at low temperatures is the lowest. At high intercritical temperatures, the effect of cold rolling is lost due to very fast austenite formation. Additionally, the effect of cold rolling on the recrystallization and austenite fraction is observed in detail. FESEM study of the samples showed that austenite nuclei prefer the primary ferrite grain boundaries either adjacent to ferrite or pearlite.

Biodegradable Zn–3Cu and Zn–3Cu–0.2Ti alloys with ultrahigh ductility and antibacterial ability for orthopedic applications

Zinc (Zn) and its alloys have been proposed as biodegradable implant materials due to their unique combination of biodegradability, biocompatibility, and biofunctionality. However, the insufficient mechanical properties of pure Zn greatly limit its clinical application. Here, we report on the microstructure, mechanical properties, friction and wear behavior, corrosion and degradation properties, hemocompatibility, and cytocompatibility of Zn–3Cu and Zn–3Cu–0.2Ti alloys under three different conditions of as-cast (AC), hot-rolling (HR), and hot-rolling plus cold-rolling (HR + CR). The HR + CR Zn–3Cu–0.2Ti exhibited the best set of comprehensive properties among all the alloy samples, with yield strength of 211.0 MPa, ultimate strength of 271.1 MPa, and elongation of 72.1 %. Immersion tests of the Zn–3Cu and Zn–3Cu–0.2Ti alloys in Hanks’ solution for 3 months indicated that the AC samples showed the lowest degradation rate, followed by the HR samples, and then the HR + CR samples, while the HR + CR Zn–3Cu exhibited the highest degradation rate of 23.9 μm/a. Friction and wear testing of the Zn–3Cu and Zn–3Cu–0.2Ti alloys in Hanks’ solution indicated that the AC samples showed the highest wear resistance, followed by the HR samples, and then the HR + CR samples, while the AC Zn–3Cu–0.2Ti showed the highest wear resistance. The diluted extracts of HR + CR Zn–3Cu and Zn–3Cu–0.2Ti at a concentration of ≤25 % exhibited non-cytotoxicity. Furthermore, both the HR + CR Zn–3Cu and Zn–3Cu–0.2Ti exhibited effective antibacterial properties against S. aureus.

Effects of Cr addition and cold deformation on the mechanical properties of a FeNi bainitic steel

ABSTRACT The effects of Cr addition and cold deformation in increasing strength and altering the austempered structure of a FeNi steel is discussed. Cr content in the steel was varied from 2 to 3 wt% whilst cold deformation was undertaken on the material at either, 10% or 50%. The cold deformed steel was then subjected to austempering treatment at 400 °C for 30 min to obtain bainite structure in the samples. Post-austempering scanning electron microscopy (SEM) images of the FeNi-Cr samples showed the formation of lower bainite (LB) and martensite/retained austenite (M/RA) in the microstructure, whilst, in the FeNi sample showed the presence of ferrite in addition to LB and M/RA. The hardness and strength of the austempered FeNi-Cr samples increased significantly with increasing Cr content. Hardness and strength values of up to 46 HRC (from ⋘<20 HRC in FeNi) and above 1400 MPa (from ~800 MPa in FeNi), respectively, were obtained in 50% cold-deformed austempered FeNi-3 wt% Cr sample. However, the elongation decreased with increasing Cr content from 22% in the FeNi to 17% in the FeNi-3 wt% Cr sample. These findings suggest that while strength and hardness increase in cold-deformed austempered FeNi with increasing Cr content, the ductility decreases.

Evaluation of Some Minerals Content of Drinking and River Water in Iraq by AAS Method

The experiment was conducted during 2018 to evaluate to the presence of certain elements (Lead, Copper, Chromium, Zinc, Nickel, Cadmium, Arsine and mercury) in Tab and Bottled water in addition to riverbed and cliff water. The obtained data were compared with the corresponding international and national guideline values. The concentration of Tap and Bottled water samples for Cr and As were higher than the permitted concentration established by FAO/WHO scoring (0.0623, 0.3120)and (0.0680, 0.448) respectively. Whilst Zn, Ni, Pb, Hg, Cd, and Cu were lower than the permitted concentration established by FAO/WHO for both samples Tab and Bottled water which scored (0.0608, 0.0550, 0.0075, 0.00589, 0.0013 and nil) and (0.0420, 0.0152, 0.0105, 0.00581, 0.0003 and nil) respectively. Thus, the concentrations of As in both River bed and cliff water samples were higher than the permitted concentration established by the Iraqi (C.O.S.Q.C) Central Organization for Standardization and Quality Control which scored (0.754 and 0.245) respectively. Regarding the rest of the element which Seem to be lower than the permitted concentration established by Central Organization for Standardization and Quality Control in Iraq for Riverbed and cliff.

Reduction per pass effect on texture traits and mechanical anisotropy of Mg–Al–Zn–Mn–Ca alloy subjected to unidirectional and cross rolling

In this work, the effect of thermomechanical processing schedules on microstructure, texture and mechanical anisotropy of Mg-1.64Al-0.84Zn-0.38Mn-0.49Ca (AZMX1100, wt.%) alloy was investigated. Two hot rolling regimes: unidirectional and cross rolling (UR and CR, respectively), followed by subsequent annealing, were systematically studied using different reductions per pass (r. p. p.) from 10 to 30%. The findings showed that the CR samples developed more recrystallized grains and fine twins compared to the UR ones. At a low r. p. p. of 10%, the CR sample exhibited a close circular ring texture. With increasing the r. p. p., an elliptical ring texture along the rolling direction (RD) was observed. For the UR samples, the degree of transverse direction (TD)-split texture component was ascending as the r. p. p. increased. After annealing, the CR annealed samples inherited and expanded texture traits of the as-rolled samples. The UR samples after annealing showed stronger TD-oriented texture components and weakened RD-oriented components. The texture of the UR annealed samples gave rise to a continuous worsening of mechanical anisotropy as the r. p. p. increased. On the contrary, with the r. p. p. of 10%, the CR annealed sample emerged with near isotropic mechanical properties due to the symmetric texture. At the higher r. p. p., the mechanical anisotropy of the CR annealed samples was slightly deteriorated.

Direct time-domain determination of electron-phonon coupling strengths in chromium

We report the results of an ultrafast, direct structural measurement of optically pumped phonons in a Cr thin film using ultrashort x-ray pulses from a free-electron laser. In addition to measuring and confirming the known long-wavelength dispersion relation of Cr along a particular acoustic branch, we are able to determine the relative phase of the phonons as they are generated. The Cr sample exhibits two generation mechanisms for the phonons: the releasing of a preexisting charge density wave at higher frequencies, and the creation of an acoustic strain pulse via laser heating that dominates at lower frequencies. For the latter mechanism, we are able to measure the frequency dependence of the time required to generate the phonons. To explain the observed magnitude and slope of the delays, we perform first-principles simulations in the framework of density functional perturbation theory and ab initio molecular dynamics to fit anharmonic phonon models. These results show that the wave-vector dependence of the electron-phonon coupling is the driving mechanism behind the delay times: Phase-space limitation leads to higher times near the zone center. The absolute magnitudes of the delay times measured are found to be much shorter than the equilibrium electron-phonon coupling times we compute, indicating that the coupling strength is greatly enhanced when the electronic system is out of equilibrium with the lattice, as has been seen in bismuth and other systems.

Importance of Preanalytical Factors in Measuring Cr and Co Levels in Human Whole Blood: Contamination Control, Proper Sample Collection and Long-Term Storage Stability.

A number of errors with potentially significant consequences may be introduced at various points in the analytical process, which result in skewed, erroneous analytical results. Precautionary procedures such as contamination control, following established sample collection protocols, and having a complete understanding of the long-term stability of the elements of interest can minimize or eliminate these errors. Contamination control is critical in the quantification of Cr and Co in human whole blood. Cr and Co levels in most biological samples are low, but these elements occur naturally in the environment and are often found in commercial and consumer products, which increases the risk of contamination. In this paper, we demonstrated that lot screening process in which we pre-screen a sub-set of manufactured lots used in collecting, analyzing and storing blood samples is a critical step in controlling Cr and Co contamination. Stainless steel needles are often utilized in blood collection but are considered as a potential source of introducing metal contamination to the patient sample. We conducted two studies to determine if there is a possibility of Cr or Co leaching into the human whole blood from the needles during blood collection. We analyzed blood collected from 100 donors and blood collected in vitro in the laboratory from designated vessel containing spiked blood with higher levels of Cr and Co. Two blood tubes were consecutively collected through one needle. In both studies, Cr and Co concentration levels in the two consecutively collected tubes were compared. Based on the results from donor and in vitro blood collection studies, we concluded that there was no Cr and Co leaching from the limited sets of stainless steel needles used in these studies. Furthermore, we demonstrated that Cr and Co human whole blood samples are stable for 1 year stored at temperatures of -70, -20 and 4°C and 6 months at room temperature.

Urban Atmospheric Environment Quality Assessment by Naturally Growing Bryophytes in Central China.

Bryophytes are popular biomonitoring plants for atmospheric environments. The objectives of this study were to examine the characteristics of bryophyte communities, determine a suitable monitor species, and assess urban atmospheric environment quality by the joint use of bryophyte features and chemical properties in a large city in China. A pleurocarpous feather moss Haplocladium angustifolium was recognized as a good biomonitor of atmospheric deposition in central China by investigating bryophyte communities and habitat environment in various ecological function regions of the urban areas in Wuhan. The concentrations of trace elements, including As, Cd, Co, Cr, Cu, Mn, Ni, V, Pb, and Zn, in moss and soil samples from 25 sampling sites were analyzed by inductively coupled plasma mass spectrometry. The concentrations of Cd and Zn in Haplocladium angustifolium collected from the entire study area were much higher than those in substrate soil. Cd was at the highest ecological risk level among the 10 elements, which contributed 34.5% to the potential ecological risk index (RI). An RI value of 392.8 indicated that urban atmospheric quality in Wuhan was in a considerable potential ecological risk. The index of atmospheric purity, regarding species richness, cover, and frequency of bryophytes, was spatially and negatively correlated with RI, also demonstrated the atmospheric quality. Effective measures should be considered to alleviate certain airborne trace element contamination and protect the environment and human health in this metropolis.

P0619POINT OF CARE CREATININE FOR EARLY DIAGNOSIS OF COMMUNITY ACQUIRED ACUTE KIDNEY INJURY IN NIGERIA. TECHNOLOGY EVALUATION AND DESIGN OF QUALITY IMPROVEMENT PROJECT

Abstract Background and Aims Acute Kidney Injury (AKI) in low- and middle-income countries is mostly a community-acquired potentially reversible syndrome and has high morbidity and mortality. Due to limited laboratory infrastructure diagnosis of AKI is often delayed until life threatening complications have developed and dialysis treatment is largely unavailable. Decisions for hospital referral from primary health care centers and triage decisions for hospital admission are not based on laboratory results in Port Harcourt Nigeria. To address the need for early diagnosis and treatment of AKI we established a collaboration between the Renal Unit of the University of Port Harcourt Teaching Hospital, Primary Health Care Board Rivers State and the Renal Department of Salford Royal NHS Foundation Trust, aiming at the evaluation of the use of point of care (POC) Creatinine (Cr) for early detection and management of community acquired AKI. Method The first stage of the project evaluated the accuracy of POC Cr technology. Following informed consent patients underwent concurrent measurement of Cr using the central laboratory (Lab) assay (Jaffe) from a venous sample and a point of care Cr measurement using a capillary sample (fingerstick) with the NOVA Stasensor Xpress Cr analyser. Pearson Correlation and Bland-Altman plots were used to assess correlation and agreement between the two methods. During the second stage, the results were discussed at a focused AKI workshop and guidance for the use of POC Cr was developed. Results During the first phase 96 concurrent POC Cr capillary and venous Lab Cr samples were analysed. Mean age was 49±14 years and 66 subjects were females. POC Cr values were 127±122 umol/l and Lab Cr values were 100 ±85 umol/L, mean positive bias of 27.2±47.94 umol/L. Overall, correlation between POC Cr and Lab Cr was very good, with Pearson correlation r=0.956) Figure 1A. All 4 out of 96 values that were outside the limits of agreement (set at mean ±2 standard deviations) were for Lab Cr values &amp;gt;200 umol/L. A Bland-Altman Plot is presented for paired samples with Lab Cr values &amp;lt;200 umol/L (Figure 1B).

Selective determination of Cr(Ⅵ) and non-chromatographic speciation analysis of inorganic chromium by chemical vapor generation-inductively coupled plasma mass spectrometry

A novel and sensitive method for the selective determination of Cr(VI) and non-chromatographic speciation of Cr(VI) and Cr(III) was developed based on chemical vapor generation (CVG) in KBH4-acid system for sample introduction into an inductively coupled plasma mass spectrometer (ICP-MS) for detection. The CVG of Cr(VI), rather than Cr(III), was found to be remarkably enhanced in the presence of sodium diethylaminodithioformate (DDTC). After the oxidation of Cr(III) to Cr(VI) by KMnO4, the quantitation of Cr(III) could be obtained based on the difference between the concentration of total chromium and that of Cr(VI). Parameters affecting the CVG reaction and determination of Cr(VI) were evaluated in detail, including the concentrations of DDTC, hydrochloric acid and KBH4, the sample flow rate, as well as the length of reaction and transferring tubing. Under optimal conditions, the CVG efficiency and the limit of detection (LOD) of Cr(VI) were found to be 28% and 0.2 ng mL−1, respectively. The relative standard deviations for seven replicate measurements of 20 ng mL−1 of Cr(Ⅵ) was 1.8%. Furthermore, with excess DDTC (100 μg mL−1) added to the test solutions, possible interferences from Cu2+ (up to 400 ng mL−1) could be eliminated. The proposed method was thus successfully applied to the determination of Cr(VI) in three real water samples and one certified reference water sample, as well as two simulated water samples of Cr(VI) and Cr(III), all with satisfactory results. The possible reasons were discussed for the varied degrees of enhancement between Cr(III) and Cr(VI).

Dielectric, magnetic and humidity properties of Mg–Zn–Cr ferrites

Abstract In this study, Cr3+ substituted Mg0.75Zn0.25CrxFe2-xO4 (x = 0, 0.1, 0.3) (Mg–Zn–Cr) ferrites have been synthesized using chemical co-precipitation method. The crystal structure and phase formation of Mg–Zn–Cr ferrites have been analyzed by X-Ray diffraction (XRD) method. The crystal size (from 15.37 nm to 10.84 nm) and lattice constant (from 8.405 A to 8.384 A) of the crystallized in cubic crystal structure Mg–Zn–Cr samples decreased with Cr3+ contribution. The change in lattice strain determined by Williamson-Hall (W–H) graphs. Morphological and elemental analysis were investigated using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy. The variations in temperature-dependent dielectric properties of samples between 290 K and 700 K were examined in the range from 20 Hz to 10 MHz. Curie temperature, where maximum dielectric constant is observed, shifted low temperatures with increasing Cr3+ contribution. This peak shift indicates that the materials have a relaxor ferroelectric character in accordance with the literature. Impedance analysis of Mg–Zn–Cr ferrites were investigated using Nyquist curves and relaxation process confirms Cole-Cole model. The magnetic properties of the samples in the range of ±5 kOe at 300 K were examined with the help of the Vibrating Sample Magnetometer (VSM). The M − H hysteresis loops of all samples showed the characteristic properties of soft magnetic materials. Finally, the effect of relative humidity (%RH) on the impedance of samples for different frequency values was investigated.