Straw-based biochar mediated potassium availability and increased growth and yield of cotton (Gossypium hirsutum L.)

Potassium (K) being the major limiting factor affecting cotton yield and quality has received massive research attention and the effects of various K fertilization techniques/organic amendments have been studied extensively. However, it is not clear whether the straw based, high pH biochar affects K availability, lint yield and quality of the cotton crop in alkaline calcareous soils. In the present study, we carried out a field experiment on a moderate to strongly calcareous silt loam soil to demonstrate the effect of straw-based biochar and potassium application levels on the growth, seed cotton yield and the lint quality. The experimental treatments comprised of two factors, A) biochar types i) Control no biochar, ii) Rice husk biochar (RHB), iii) Wheat straw biochar (WSB), and iv) Rice straw biochar (RSB), factor B) potassium application levels (i) control, no K fertilizer application, ii) K at 15 kg ha⁻¹, and iii) K at 30 kg ha⁻¹ (4 × 3 × 3, n = 36). Results showed that overall cotton growth and yield was significantly improved with increasing rates of potassium application. Three biochar sources affected seed cotton yield and quality with varying effects. For instance, the RSB increased plant height (11.71% to 22.47%), number of bolls per plant (0.74% to 13.75%), average boll weight (35.44% to 36.22%), the seed cotton yield was increased by 14.48% over the control when rice straw biochar was applied in combination with potassium at 30 kg ha⁻¹. However, the ginning out turn (%) was declined with potassium application in combination with all three-biochar compared to control (no biochar addition). The WSB increased staple length and micronaire by 4.32% and 24.50% without potassium application. The potential effects of straw based biochar and potassium application on seed cotton yield and quality deserve further studies to identify the most suitable biochar as per soil chemical properties.     

Quality variations of poultry litter biochar generated at different pyrolysis temperatures

Producing biochar and biofuels from poultry litter (PL) through slow pyrolysis is a farm-based, value-added approach to recycle the organic waste. Experiments were conducted to examine the effect of pyrolysis temperature on the quality PL biochar and to identify the optimal pyrolysis temperature for converting PL to agricultural-use biochar. As peak pyrolysis temperature increased incrementally from 300 to 600 °C, biochar yield, total N content, organic carbon (OC) content, and cation exchange capacity (CEC) decreased while pH, ash content, OC stability, and BET surface area increased. The generated biochars showed yields 45.7–60.1% of feed mass, OC 325–380 g kg⁻¹, pH 9.5–11.5, BET surface area 2.0–3.2 m² g⁻¹, and CEC 21.6–36.3 cmol_c kg⁻¹. The maximal transformation of feed OC into biochar recalcitrant OC occurred at 500 °C, yet 81.2% of the feed N was lost in volatiles at this temperature. To produce agricultural-use PL biochar, 300 °C should be selected in pyrolysis; for carbon sequestration and other environmental applications, 500 °C is recommended.     

Rapid residue analysis of four triazolopyrimidine herbicides in soil, water, and wheat by ultra-performance liquid chromatography coupled to tandem mass spectrometry

A sensitive and effective method for simultaneous determination of triazolopyrimidine sulfonamide herbicide residues in soil, water, and wheat was developed using ultra-performance liquid chromatography coupled with tandem mass spectrometry. The four herbicides (pyroxsulam, flumetsulam, metosulam, and diclosulam) were cleaned up with an off-line C18 SPE cartridge and detected by tandem mass spectrometry using an electrospray ionization source in positive mode (ESI+). The determination of the target compounds was achieved in <2.0 min. The limits of detection were below 1 μg kg⁻¹, while the limits of quantification did not exceed 3 μg kg⁻¹ in different matrices. Quantitation was determined from calibration curves of standards containing 0.05–100 μg L⁻¹ with r ² > 0.997. Recovery studies were conducted at three spiked levels (0.2, 1, and 5 μg kg⁻¹ for water; 5, 10, and 100 μg kg⁻¹ for soil and wheat). The overall average recoveries for this method in water, soil, wheat plants, and seeds at three levels ranged from 75.4% to 106.0%, with relative standard deviations in the range of 2.1–12.5% (n = 5) for all analytes.     

Biochar coupled with contrasting nitrogen sources mediated changes in carbon and nitrogen pools,microbial and enzymatic activity in paddy soil

There is limited information on changes cause by nitrogen (N) fertilizers and biochar (BC) application in soil carbon and nitrogen availability, leaching and microbial activity at different growth stages in rice. This is first comprehensive study conducted in early and late seasons during 2019 to evaluate efficiency of various traditional N fertilizers (i) Urea (ii) Ammonium nitrate and (iii) Ammonium sulfate (315 kg N ha⁻¹) with or without biochar (30 t ha⁻¹). Results illustrated that all N fertilizers sources applied with biochar significantly increased soil organic carbon (SOC) content by an average 48.44% and 50.63%, soil total nitrogen (Nt) by 4.56% and 4.94%, reduction in total nitrogen leaching by 42.63% and 76.16%, while dissolved organic carbon leaching (DOC) augmented by 39.87% and 38.38% than non-applied treatments in early and late season, respectively. Additionally, soil microbial biomass C and N progressively increased with growth stages and was found higher than non-applied treatments in both seasons. Furthermore, combined application of N fertilizers and biochar, facilitated soil N transformation and the net concentration of NH₄⁺–N and NO₃⁻–N was relatively higher than non-charred treatments. Similarly, in both early and late seasons, urease enzyme activity increased by an average 13.52% and 13.55%, β-glucosidase by 15.99% and 19.27% however, catalase activity decreased by 14.58% and 12.38%, correspondingly. Moreover, no significant difference (p < 0.05) was recorded among N fertilizers sources in both seasons.     

Copper removal from aqueous solution using biochar: Effect of chemical activation

The main aim of this study was to test the efficiency of biochar for Cu removal from synthetic and soil solutions, respectively.The biochar was produced from brewers draff via pyrolysis. Additionally, the prepared biochar was also activated using 2 M KOH to enhance its sorption efficiency to remove Cu from both solutions. Two different aqueous solutions were prepared for these experiments: (i) a synthetic using Cu-nitrate salt with 0.01 M NaNO₃ and (ii) soil solution obtained from a Cu-contaminated soil using 0.01 M CaCl₂ leaching procedure. Batch sorption and column experiments were used to evaluate the efficiency of both biochar (BC) and activated biochar (BC_act) to remove Cu from the solutions.Results showed that both biochar samples are pure amorphous carbon and the Cu sorption is thus mainly a result of physical sorption on the biochar surface. Next, chemical activation, using 2 M KOH, significantly increased the total volume of all pores in biochar (from 0.01 ± 0.002 to 8.74 ± 0.18 mL g⁻¹). On the other hand, the BET surface area was similar for both sorbents (BC = 9.80 ± 0.62 m² g⁻¹ and BC_act = 11.6 ± 0.4 m² g⁻¹). Results also demonstrate enhanced sorption efficiency of the BC_act (10.3 mg g⁻¹) in comparison with the BC (8.77 mg g⁻¹). Additionally, enhanced Cu removal during column retention test was observed for the BC_act in both synthetic and soil solutions, respectively.In summary, the results showed that biochar prepared from brewers draff was able to remove Cu from both aqueous solutions.     

Homogeneous liquid-liquid extraction combined with gas chromatography-electron capture detector for the determination of three pesticide residues in soils

In this study, a new method was developed for analyzing malathion, cypermethrin and lambda-cyhalothrin from soil samples by using homogeneous liquid–liquid extraction (HLLE) and gas chromatography with electron capture detector (GC–ECD). Acetone was used as extraction solvent for the extraction of target pesticides from soil samples. When the extraction process was finished, the target analytes in the extraction solvent were rapidly transferred from the acetone extract to carbon tetrachloride, using HLLE. Under the optimum conditions, linearity was obtained in the range of 0.05–40 μg kg⁻¹ for malathion, 0.04–10 μg kg⁻¹ for lambda-cyhalothrin and 0.05–50 μg kg⁻¹ for cypermethrin, respectively. Coefficients of correlation (r²) ranged from 0.9993 to 0.9998. The repeatability was carried out by spiking soil samples at concentration levels of 2.5 μg kg⁻¹ for lambda-cyhalothrin, and 10 μg kg⁻¹ for malathion and cypermethrin, respectively. The relative standard deviations (RSDs) varied between 2.3 and 9.6% (n = 3). The limits of detection (LODs), based on signal-to-noise ratio (S/N) of 3, varied between 0.01 and 0.04 μg kg⁻¹. The relative recoveries of three pesticides from soil A1, A2 and A3 at spiking levels of 2.5, 5 and 10 μg kg⁻¹ were in the range of 82.20–91.60%, 88.90–110.5% and 77.10–98.50%, respectively. In conclusion, the proposed method can be successfully applied for the determination of target pesticide residues in real soil samples.     

Residual levels and dietary risk assessment of bifenthrin and dinotefuran and its major metabolites in open wheat field conditions

To evaluate the residual levels of bifenthrin and dinotefuran, a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) and high-performance liquid chromatography–tandem mass spectrometry method for simultaneous detection of bifenthrin and dinotefuran and its major metabolites in wheat was developed and validated. Dietary risk assessments were further performed based on the relevant residual data from 12 wheat fields, toxicology data and dietary patterns. In wheat grain and straw, the recoveries of all analytes ranged from 77 to 102% with the relative standard deviation <9.7% and the limit of quantitation 0.05 mg kg⁻¹. The highest terminal residue of bifenthrin in wheat grain was 0.069 mg kg⁻¹ and dinotefuran was 0.34 mg kg⁻¹. Residual concentrations of bifenthrin and dinotefuran decreased to <0.05 and 0.15 mg kg⁻¹ at 21 days (pre-harvest interval), respectively. The chronic risk quotient ranged from 6.4 to 62.7% and the acute risk quotient varied from 0.38 to 17.73%. The chronic and acute dietary risks caused by the terminal residues of the two insecticides were negligible for Chinese populations. The recommended pre-harvest interval was proposed to ensure safe wheat consumption. These data could provide a scientific reference to establish the Chinese maximum residue limit of dinotefuran in wheat.     

Modified QuEChERS method for phenolic compounds determination in mustard greens (Brassica juncea) using UHPLC-MS/MS

A modified QuEChERS method (Quick, Easy, Cheap, Effective, Rugged, and Safe) for the determination of fifteen phenolic compounds in mustard greens (Brassica juncea) using ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) analysis was developed. The QuEChERS partitioning step and dispersive solid phase extraction (d-SPE) clean-up sorbents were investigated, aimed at phenolic compound extraction and pigment removal, respectively. QuEChERS acetate version combined with 25 mg of diatomaceous earth (DE) and 5.0 mg of graphitized carbon black (GCB) provided the best conditions for sample preparation of the target compounds. Under the optimized conditions, all phenolic compounds showed good linearity (r ≥ 0.99) over the concentration range of 0.1 to 8000 μg kg⁻¹, and the quantification limits were in the range of 0.06–230 μg kg⁻¹. The spectrophotometric analysis showed that the clean-up step promoted a significant removal of chlorophyll, which is the major pigment present in the sample. Furthermore, antioxidant activity analysis was also carried out after the clean-up step and, together with chromatographic data, showed that no significant retention of the phenolic compounds occurs in the clean-up step. Two mustard greens varieties – Southern Giant Curled (SGC) and Florida Broadleaf (FB) - were analyzed with the proposed method. Seven phenolic compounds (4-hydroxybenzoic, p-coumaric, ferulic and sinapic acids, naringenin, apigenin and kaempferol) were found in both varieties, the greatest abundance being for sinapic acid (1261.5 ± 23 μg kg⁻¹ in SGC and 1235.5 ± 26 μg kg⁻¹ in FB) and ferulic acid (2861 ± 24 μg kg⁻¹ in SGC and 3204.5 ± 45 μg kg⁻¹ in FB).     

Miniaturized liquid–liquid extraction coupled with ultra-performance liquid chromatography/tandem mass spectrometry for determination of topramezone in soil,corn, wheat,and water

A rapid and simple miniaturized liquid–liquid extraction method has been developed for the determination of topramezone in soil, corn, wheat, and water samples using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-electrospray ionization (ESI)/MS/MS). The established method for the extraction and purification procedure was based on liquid–liquid partitioning into an aqueous solution at a low pH (pH ≈ 2.5), followed by back-partitioning into water at pH > 9. Two precursor, product ion transitions for topramezone were measured and evaluated to provide the maximum degree of confidence in the results. Under negative ESI conditions, quantitation was achieved by monitoring the fragment at m/z = 334 and the qualitative fragment at m/z = 318, whereas also collecting the corresponding parent ion at m/z = 362. Chromatographic separation was achieved using gradient elution with a mobile phase consisting of methanol and a 0.01% aqueous ammonium hydroxide solution. Recovery studies for soil, corn, wheat, and water were conducted at four different topramezone concentrations (5 or 10, 50, 100, and 1,000 μg kg⁻¹); the overall average recoveries ranged from 79.9% to 98.4% with intra-day relative standard deviations (RSD) of 3.1~8.7% and inter-day RSD of 4.3~7.5%. Quantitative results were determined from calibration curves of topramezone standards containing 1–500 μg L⁻¹ with an R ² ≥ 0.9994. Method sensitivities expressed as limits of quantitation were typically 6, 8, 9, and 1 μg kg⁻¹ in soil, corn, wheat, and water, respectively. The results of the method validation confirmed that this proposed method was convenient and reliable for the determination of topramezone residues in soil, corn, wheat, and water.     

Fire hazard and heat of combustion of sunflower seed hull pellets

This study is concerned with the investigation of the impact of heat flux on the fire hazard and the effective heat of combustion of sunflower seed hull pellets. Pellets produced by pressing common sunflower seed hulls (Helianthus annuus L.) were investigated. The samples were dried on water content of 0 mass% at a temperature of 103 ± 2 °C. The fire hazard and the heat of combustion have been determined via the cone calorimeter and by the testing procedure per ISO 5660-1:2015 at three heat fluxes (25, 35 and 50 kW m⁻²). The peak heat release rate increases with the increasing of the heat flux from 446 (at a heat flux of 25 kW m⁻²) to 601 kW m⁻² (at a heat flux of 50 kW m⁻²). The carbon monoxide yield lies in the interval from 82.50 (at a heat flux of 25 kW m⁻²) to 154.15 g kg⁻¹ (at a heat flux of 50 kW m⁻²). The effective heat of combustion decreases with the increasing of the heat flux from 15.84 (at a heat flux of 25 kW m⁻²) to 14.58 MJ kg⁻¹ (at a heat flux of 50 kW m⁻²).

     

Ozone enhanced production of potentially useful exopolymers from the cyanobacterium Nostoc muscorum

Extracellular polysaccharides (EPS) from Nostoc muscorum, a heterocystous, filamentous cyanobacterium isolated from a jhumland (shifting cultivation) soil of Assam, North-East India, was physico-chemically characterized to find out its potential applications and to improve its production with some stress source like ozone. Using Response Surface Methodology (RSM), EPS production was improved. Accordingly, with magnesium sulfate (MgSO_4·7H₂O) at 62 mg L⁻¹, Sodium Chloride (NaCl) at 58 mg L⁻¹ and 56 mg L⁻¹ di-potassium hydrogen phosphate (K₂HPO₄), a yield of 126.73 μg mL⁻¹ of EPS in 12 days was obtained which was four-fold higher than un-optimised control. An important finding of this study is that EPS production could be further enhanced by over 50% with a mild stress by a strong oxidizing agent ozone (O₃). Physico-chemical properties of this Ozone induced EPS was evaluated and found identical to uninduced EPS. EPS was composed of the hexoses- Glucose (14.80%), Galactose (18.01%) and Mannose (12.64%), the pentoses- Arabinose (17.86%) and Xylose (11.66%), the deoxyhexose- Fucose (12.53%) and Rhamnose (12.50%). Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) analysis revealed the presence of the functional groups uronic acid and traces of sulfate group. The Zeta potential analysis revealed that the emulsions were stabilized electrosterically rather than by pure electrostatic repulsion and steric stabilization. EPS at 1% in hydrocarbons and vegetable oils was observed to be an excellent emulsifier (99%), with reasonable stability. Rheological study revealed that the EPS (1%) was a non- Newtonian weak gel, useful for emulsification activity. Unlike petroleum-based emulsifiers now in use, bio-based EPS are renewable, economical and eco-friendly. The physico-chemical characteristics suggest their utility in a wide variety of other applications including bioremediation, manufacture of paints, shear reduction in oil drilling etc.     

Simultaneous extraction of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in agricultural soils by pressurized liquid extraction and determination by gas chromatography coupled to tandem mass spectrometry

A simple and rapid method based on pressurized liquid extraction has been validated for the simultaneous extraction of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) from agricultural soil samples. Effective extraction was carried out in less than 17 min for all the studied compounds, and good recoveries were obtained for PAHs and PCBs, ranging from 70% to 112%, when blank samples were spiked at 2.5 μg kg⁻¹, except for naphthalene with recoveries close to 40%. The separation and determination were performed by gas chromatography coupled to tandem mass spectrometry using a triple quadrupole mass analyzer. The target compounds were detected by electron impact with selected reaction monitoring, and mass spectrometric conditions were optimized in order to increase selectivity and sensitivity. The developed method was validated, and matrix-matched calibration was used for quantification purposes. Repeatability and interday precision ranged from 0.9% to 16.8% and from 1.6% to 22.3%, respectively. Limits of quantification ranged from 0.07 to 2.50 μg kg⁻¹. The proposed method was applied to the analysis of agricultural soil samples collected from Almeria (Spain), and PAHs and PCBs were detected in some samples at concentrations ranging from 0.1 to 210 μg kg⁻¹.     

O3 and SO2 sensing concept on extended surface of B12N12 nanocages modified by Nickel decoration: A comprehensive DFT study

Adsorption of SO₂ and O₃ molecules on pristine boron nitride (B₁₂N₁₂) and Ni-decorated B₁₂N₁₂ nano-cages has been systemically investigated through density functional theory (DFT) methods. Adsorption energies (thermodynamics), bond distances, charge analysis, dipole moments, orbital analysis and density of states are calculated by van der Waals DFT method (MPW1PW91) functional. The adsorption energies of O₃ and SO₂ on pristine B₁₂N₁₂ are about −143.8 and −14.0 kJ mol⁻¹, respectively. The interaction energies of O₃ and SO₂ with pristine B₁₂N₁₂ are indicative of chemisorption and physisorption, respectively. Ni-decorated B₁₂N₁₂ (Ni@BN) enhances adsorption of both O₃ and SO₂ species. The interaction energies for adsorption of SO₂ are about −166 and −277 kJ mol⁻¹ whereas the corresponding energies for O₃ are −362 and −396 kJ mol⁻¹ for configuration A and B, respectively. These observations show that functionalized B₁₂N₁₂ are highly sensitive toward SO₂ and O₃ molecules.     

Production of char from vacuum pyrolysis of South-African sugar cane bagasse and its characterization as activated carbon and biochar

The potential of vacuum pyrolysis to convert sugar cane bagasse into char materials for wastewater treatment and soil amendment is the focus of this research paper. Vacuum pyrolysis produces both bio-oil and char in similar quantities. Vacuum pyrolysis has the potential to produce high quality chars for wastewater treatment and soil amendment directly during the conversion process, with no further upgrading required. In the present study, chars with the required porous structure was obtained directly from the vacuum pyrolysis process, making it very efficient as adsorbent both in terms of methylene blue (MB) adsorption with a N₂-BET surface area of 418 m² g⁻¹. Further steam activation of the chars benefited the development of meso- and macroporosity, although this upgrading step was not essential to achieve the required performance of char as an MB adsorbent. The development of large pores during the vacuum pyrolysis favored physisorption of MB, rather than chemisorption. The chemical nature of the vacuum pyrolysis char resulted in a slightly acidic surface (pH 6.56). The biochar from vacuum pyrolysis can be considered as a highly beneficial soil amendment, as it would enhance soil nutrient and water holding capacity, due to its high cation exchange capacity (122 cmol_c kg⁻¹) and high surface area. It is also a good source of beneficial plant macro- and micronutrients and contains negligible levels of toxic elements.     

Analysis of the role of various biochar in the remediation of heavy metals in contaminated water and its kinetics study

Biochar prepared from agricultural wastes has gained great attention as a cost-effective treatment for metal-contaminated water. In this study, the effectiveness of corn cob and sugarcane bagasse-derived biochar for metals (Pb, Ni, and Cu) removal from an aqueous medium was examined following their physical, chemical, and structural characterization. Batch sorption experiments were carried out by employing the Langmuir and Freundlich equations. The results indicated that separation factor (R_L) values lay in the range of 0 and 1 representing the productive adsorption. The optimum dosage for metal adsorption can be recommended as 30 g L^?1. The optimum adsorption conditions were found at 6.5 and 5.5 pH, 1.5 g adsorbent dose, and at 180 min equilibrium time, for both corn cob and sugarcane bagasse biochars. At pH 6.5, adsorption capacities of Pb, Ni, and Cu were found maximum i.e., 11.34, 15.71, and 11.96 mg kg^?1 for corn cob and 8.96, 15.46, and 12 mg kg^?1, for sugarcane bagasse biochars, respectively. The metal adsorption kinetics was analyzed via four different types of the pseudo-second-order kinetic model. Moreover, the corn cob biochar showed a more pronounced activity in the removal of metals compared to sugarcane bagasse biochar. Hence, it was concluded that corncob and sugarcane bagasse-derived biochars could be utilized as economical bio-adsorbents for the heavy metals removal from wastewater.     

Assessment of annual effective dose from natural radioactivity intake through wheat grain produced in Faisalabad,Pakistan

Wheat is staple food of the people of Pakistan. Phosphate fertilizers, used to increase the yield of wheat, enhance the natural radioactivity in the agricultural fields from where radionuclides are transferred to wheat grain. A study was, therefore, carried out to investigate the uptake of radioactivity by wheat grain and to determine radiation doses received by human beings from the intake of foodstuffs made of wheat grain. Wheat was grown in a highly fertilized agricultural research farm at the Nuclear Institute of Agriculture and Biology (NIAB), Faisalabad, Pakistan. The activity concentration of ⁴⁰K, ²²⁶Ra and ²³²Th was measured in soil, single superphosphate (SSP) fertilizer, and wheat grain using an HPGe-based gamma-ray spectrometer. Soil to wheat grain transfer factors determined for ⁴⁰K, ²²⁶Ra and ²³²Th were 0.118 ± 0.021, 0.022 ± 0.004 and 0.036 ± 0.007, respectively, and the annual effective dose received by an adult person from the intake of wheat products was estimated to be 217 μSv.     

In situ polymerization and reduction to fabricate gold nanoparticle‐incorporated polyaniline as supercapacitor electrode materials

Nanocomposites of gold nanoparticles and polyaniline are synthesized by using HAuCl₄ and ammonium peroxydisulfate as the co‐oxidant involving in situ polymerization of aniline and in situ reduction of HAuCl₄. Through these in situ methods, the synthesized Au nanoparticles of ca. 20 nm embedded tightly and dispersed uniformly in polyaniline backbone. With the Au content in composite increasing from 4.20 to 24.72 wt.%, the specific capacitance of the materials first increased from 334 to 392 F g⁻¹ and then decreased to 298 F g⁻¹. Based on the real content of PANI in composite material, the highest specific capacitance is calculated to be 485 F g⁻¹ at the Au amount of 19.15 wt.%, which remains 55.6% after 5000 cycles at the current density of 2 A g⁻¹. Finally, the asymmetric supercapacitor of AuNP/PANI||AC and the symmetric supercapacitor of AuNP/PANI||AuNP/PANI are assembled. The asymmetric supercapacitor device shows a better electrochemical performance, which delivers the maximum energy density of 7.71 Wh kg⁻¹ with power density of 125 W kg⁻¹ and maximum power density of 2500 W kg⁻¹ with the energy density of 5.35 Wh kg⁻¹.     

Determination of fluoroquinolone residues in poultry muscle in Portugal

A total of 98 poultry samples, including chicken and turkey muscle, were analysed, using a sensitive and reliable analytical method based on liquid chromatography (LC) with spectrofluorimetric detection, for simultaneous determination of four fluoroquinolone (FQ) antibiotics, namely enrofloxacin (ENRO), ciprofloxacin (CIPRO), norfloxacin (NOR), and sarafloxacin (SARA). The method involved extraction with 0.15 mol L⁻¹ HCl and clean-up by solid-phase extraction using Oasis HLB cartridges. Chromatographic separation was carried out on a C₁₈ TSK gel column, in isocratic mode, with 0.025 mol L⁻¹ H₃PO₄ solution, adjusted to pH 3.0 with tetrabutylammonium hydroxide-methanol (78:22) as mobile phase. Good linearity over the investigated concentration range was observed, with mean values of correlation coefficients higher than 0.9989 for all the analytes studied. The limits of quantification (LOQ), expressed as the lowest fortification level with acceptable precision were 15 μg kg⁻¹ for ENRO, CIPRO, and NOR, and 30 μg kg⁻¹ for SARA; these values are in compliance with requirements for monitoring of maximum residues levels (MRLs). Overall recoveries from spiked samples ranged from 80% to 92% with relative standard deviations (RSD) lower than 6.1%. Of the chicken and turkey samples analysed, 44.2% and 37.8%, respectively, were contaminated. The levels found in the analysed poultry samples, collected from markets of Oporto and Coimbra, located in the north and central zones of Portugal, respectively, were lower than 114.2 and 87.6 μg kg⁻¹ in chicken and turkey muscle samples, respectively. One positive chicken sample was contaminated with ENRO at levels higher than the MRL.     

Central role of TiO2 anatase grain boundaries on resistivity of CaCu3Ti4O12-based materials probed by Raman spectroscopy

This study focuses on characterization and control of grain boundaries to enhance the properties of CaCu₃Ti₄O₁₂ (CCTO) ceramics capacitors for industrial applications. A novel factor deals with TiO₂ anatase revealed by Raman scattering in grain boundaries, found as a dominant parameter of largest sample resistivity, consistent with higher grain boundary resistivity and higher breakdown voltage. Four selected samples of CCTO-based compositions showing very different properties in terms of permittivity ranging from 1000 to 684 000 measured at 1 kHz, capacitance of grain boundaries ranging from 8 10⁻¹⁰ to 4.5 10⁻⁷ F cm⁻¹, grain boundary resistivity ranging from 193 to 30,000,000 Ω cm and sample resistivity extending from 450 to 10¹¹ Ω cm. The relationship between permittivity weighted by grain size and capacitance of grain boundaries confirms the internal barrier layer capacitance model over 5 orders of magnitude.     

Viscometric studies on saccharides in aqueous magnesium chloride solutions at T = (288.15 to 318.15) K

The viscosity B-coefficients of mono-, di-, tri-saccharides and the derivatives (methyl glycosides) in m_B = (0.5, 1.0, 2.0, and 3.0) mol · kg⁻¹ aqueous solutions of magnesium chloride have been determined from viscosity data using the Jones–Dole equation at T = (288.15, 298.15, 308.15, and 318.15) K. The viscosity B-coefficients of transfer (Δ_tB), the temperature derivatives of B-coefficients (dB/dT), pair and triplet viscometric interaction coefficients (η_AB, η_ABB) have been determined. The viscosity B-coefficients data of systems studied in water have been reported earlier. The results have been interpreted in light of the solute–solute and solute–solvent interactions occurring in these systems. The comparison of results has been made with those reported in the presence of potassium chloride, ammonium sulphate, and sodium sulphate.