Comparing nitric acid treatment and microwave digestion for efficiency of metal extraction from bioprocess samples.

Metal ions may act as enzyme cofactors and influence the kinetics of biochemical reactions that may also influence the biological production of therapeutic proteins and quality attributes such as glycosylation. Because sample preparation is a significant step in the reliable analysis of metals, we compared two sample preparation procedures for metal analysis of bioreactor culture media samples by ICP-MS: (i) samples were diluted in 2 % nitric acid (treatment with nitric acid, TNA); and (ii) samples were mixed with equal volume of 5 % nitric acid and closed vessel digestion was performed in a microwave (closed vessel digestion, CVD). In the comparison of extraction efficiencies between TNA and CVD procedures, CVD showed better extraction for Ca and Cu among bulk metals (∼30 %) and for Ni among the trace metals (∼65 %) for the bioreactor broth supernatant samples. For the cell pellet samples, the CVD procedure was found to be better for extraction of Fe (∼65 % more) among bulk metals, Zn (∼20 % more) among minor metals and Co (∼60 % more) and Ni (∼45 % more) among trace metals. Differences between the two procedures were less than 10 % and TNA was better for all other metals quantified from both supernatant samples and cell pellet samples. The current study helps bring more clarity to the methodology on comprehensive metal analysis to monitor and maintain trace metal content for biologics production.

Rapid sulfuric acid-dimethylamine nucleation enhanced by nitric acid in polluted regions.

Recent research [Wang et al., Nature 581, 184-189 (2020)] indicates nitric acid (NA) can participate in sulfuric acid (SA)-ammonia (NH3) nucleation in the clean and cold upper free troposphere, whereas NA exhibits no obvious effects at the boundary layer with relatively high temperatures. Herein, considering that an SA-dimethylamine (DMA) nucleation mechanism was detected in megacities [Yao et al., Science 361, 278-281 (2018)], the roles of NA in SA-DMA nucleation are investigated. Different from SA-NH3 nucleation, we found that NA can enhance SA-DMA-based particle formation rates in the polluted atmospheric boundary layer, such as Beijing in winter, with the enhancement up to 80-fold. Moreover, we found that NA can promote the number concentrations of nucleation clusters (up to 27-fold) and contribute 76% of cluster formation pathways at 280 K. The enhancements on particle formation by NA are critical for particulate pollution in the polluted boundary layer with relatively high NA and DMA concentrations.

Effect of Various Surface Treatments of Zirconia on its Adhesive Properties to Dentin: An In Vitro Study.

AIM: To assess the effectiveness of various surface treatments and adhesives on the bond strength of zirconia-based ceramic to dentin. MATERIALS AND METHODS: Eighty samples of zirconia were subjected to the four-surface treatment protocols (sandblasting, 48% hydrofluoric acid (HF), 48% hydrofluoric acid + 70% nitric acid (HNO3) and no treatment (control) following which the samples from each group were subdivided into two subgroups (n = 10) based on the resin cement employed for cementation (RelyX U200 and G-Cem Linkforce). The bonded specimens were subjected to shear stress to measure the bond strength using Universal testing machine. To test the difference in bond strength among the eight study groups, the Kruskal-Wallis ANOVA test was applied and for comparison between cements in each group, Mann-Whitney U test was applied. RESULTS: The highest bond strength values were observed for 48% HF group cemented with G-Cem Linkforce resin cement (16.220 ± 1.574) and lowest for control group-RelyX (4.954 ± 0.972). G-Cem cement showed higher bond strength than RelyX for all surface treatments except 48% HF + 70% nitric acid. CONCLUSION: It can be inferred that 48% HF can etch zirconia and generate a porous structure that proves to be beneficial for bonding. CLINICAL SIGNIFICANCE: The increasing demand for esthetics has led to the replacement of metal-ceramic materials with zirconia-based ceramics. However, the chemical inertness of zirconia to various conventional surface treating agents has continuously challenged researchers to discover a new surface treatment protocol that could enhance the bond strength of zirconia. How to cite this article: Yenamandra MS, Joseph A, Singh P, et al. Effect of Various Surface Treatments of Zirconia on its Adhesive Properties to Dentin: An In Vitro Study. J Contemp Dent Pract 2024;25(3):226-230.

Rapid cycling of reactive nitrogen in the marine boundary layer.

Nitrogen oxides are essential for the formation of secondary atmospheric aerosols and of atmospheric oxidants such as ozone and the hydroxyl radical, which controls the self-cleansing capacity of the atmosphere. Nitric acid, a major oxidation product of nitrogen oxides, has traditionally been considered to be a permanent sink of nitrogen oxides. However, model studies predict higher ratios of nitric acid to nitrogen oxides in the troposphere than are observed. A 'renoxification' process that recycles nitric acid into nitrogen oxides has been proposed to reconcile observations with model studies, but the mechanisms responsible for this process remain uncertain. Here we present data from an aircraft measurement campaign over the North Atlantic Ocean and find evidence for rapid recycling of nitric acid to nitrous acid and nitrogen oxides in the clean marine boundary layer via particulate nitrate photolysis. Laboratory experiments further demonstrate the photolysis of particulate nitrate collected on filters at a rate more than two orders of magnitude greater than that of gaseous nitric acid, with nitrous acid as the main product. Box model calculations based on the Master Chemical Mechanism suggest that particulate nitrate photolysis mainly sustains the observed levels of nitrous acid and nitrogen oxides at midday under typical marine boundary layer conditions. Given that oceans account for more than 70 per cent of Earth's surface, we propose that particulate nitrate photolysis could be a substantial tropospheric nitrogen oxide source. Recycling of nitrogen oxides in remote oceanic regions with minimal direct nitrogen oxide emissions could increase the formation of tropospheric oxidants and secondary atmospheric aerosols on a global scale.

Multielement Determination in Turmeric (Curcuma longa L.) Using Different Digestion Methods.

The antioxidant, anti-inflammatory and antiseptic properties of turmeric (Curcuma longa L.) derive from its rich nutritional composition making it interesting for medicinal uses, besides being used as spice in cooking. To complete the picture on the composition of turmeric, not only the organic compounds need to be known, but also the elemental composition covering essential and potentially toxic elements. The samples were digested in a microwave assisted digestion system using different reagent mixtures. The best digestion mixture was semi-concentrated nitric acid combined with hydrogen peroxide. After optimization of the sample preparation method, the contents of Ag, Al, As, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, K, Li, Mg, Mn, Mo, Na, Ni, Pb, Rb, Se, Sr, Te, Tl, V and Zn in curcuma were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES), as well as by inductively coupled plasma mass spectrometry (ICP-MS). Even if the general composition found is in line with the scarce data in literature, clear differences can be seen between the analyzed samples, considering provenience, production procedures, and harvesting year as potential influencing factors. Whereas all samples contained less As and Pb than regulated by WHO, one limit exceeding was found for Cd.

In vitro targeting and selective killing of mcf-7 and colo320dm cells by 5-fluorouracil anchored to carboxylated SWCNTs and MWCNTs.

The intention of the present work was to synthesize the f-MWCNT and f-SWCNT terminated with proper functional group, loading of 5-Flurouracil and to perform cytotoxic activity. Functionalization of MWCNTs and SWCNTs was achieved through the acid treatment (H2SO4 + HNO3). 5-flurouracil was loaded into the prepared functionalized CNTs, thereafter; in vitro drug loading capacity and % drug release were calculated. Also the prepared f-CNTs, 5-flurouracil loaded CNTs were distinguished by using SEM, TGA, DSC, X-ray diffraction, Raman and FTIR spectroscopy. MCF-7 and COLO320DM cells were treated with selected concentrations of 5-FU loaded f-MWCNTs and f-SWCNTs to estimate the cytotoxic activity. It was observed that 5-FU loaded f-SWCNTs showed good activity against selected cell lines than others. Moreover, apoptosis percentage was reported to be 84.46 ± 4.3515 and 92.78 ± 2.6549 for 5-FU loaded f-SWCNTs against MCF-7 and COLO320DM cells respectively. It is evident from the results that the prepared drug loaded CNTs have comparable antitumor activity in cancer cell lines.

Characteristics of Raw and Acid-Activated Bentonite and Its Application for Improving Electrical Conductivity of Tap Water.

This study aimed to investigate the characteristics of acid-activated bentonite by focusing on its capability of improving the quality of tap water used during wire electrical discharge machining. Raw bentonite (RB) was activated using sulfuric acid, nitric acid, and phosphoric acid solutions with concentrations of 1, 5, and 10 mol/L, respectively. Scanning electron microscopy images, specific surface area, pore volume, cation exchange capacity, X-ray diffraction patterns, and binding energy of RB and acid-activated bentonites were also evaluated. The specific surface area and pore volume of acid-activated bentonites exceeded those of RB. Conversely, the cation exchange capacity of acid-activated bentonites exhibited an opposite trend. The electrical conductivity of tap water was decreased significantly due to bentonite activated with sulfuric acid, nitric acid, and phosphoric acid solution (removal percentage of approximately 31-39%), as compared to that due to RB. Therefore, the relationship between electrical conductivity and the removed concentration of anion/cation ions was evaluated; the correlation coefficient was -0.950 for the experimental condition in this study. Additionally, the amount of magnesium, calcium, potassium, and sodium ions were decreased after the treatment. These results indicated that acid-activated bentonite can be produced from RB via acid activation and that it can be used to decrease electrical conductivity of tap water.

Synthesis of 2,4,6-Trinitrotoluene (TNT) Using Flow Chemistry.

This paper describes the nitration of 2,4-dinitrotoluene (DNT) and its conversion to 2,4,6-trinitrotoluene (TNT) at a gram scale with the use of a fully automated flow chemistry system. The conversion of DNT to TNT traditionally requires the use of highly hazardous reagents like fuming sulfuric acid (oleum), fuming nitric acid (90-100%), and elevated temperatures. Flow chemistry offers advantages compared to conventional syntheses including a high degree of safety and simpler multistep automation. The configuration and development of this automated process based on a commercially available flow chemistry system is described. A high conversion rate (>99%) was achieved. Unlike established synthetic methods, ordinary nitrating mixture (65% HNO3/98% H2SO4) and shorter reaction times (10-30 min) were applied. The viability of flow nitration as a means of safe and continuous synthesis of TNT was investigated. The method was optimized using an experimental design approach, and the resulting process is safer, faster, and more efficient than previously reported TNT synthesis procedures. We compared the flow chemistry and batch approaches, including a provisional cost calculation for laboratory-scale production (a thorough economic analysis is, however, beyond the scope of this article). The method is considered fit for purpose for the safe production of high-purity explosives standards at a gram scale, which are used to verify that the performance of explosive trace detection equipment complies with EU regulatory requirements.

Increasing importance of deposition of reduced nitrogen in the United States.

Rapid development of agriculture and fossil fuel combustion greatly increased US reactive nitrogen emissions to the atmosphere in the second half of the 20th century, resulting in excess nitrogen deposition to natural ecosystems. Recent efforts to lower nitrogen oxides emissions have substantially decreased nitrate wet deposition. Levels of wet ammonium deposition, by contrast, have increased in many regions. Together these changes have altered the balance between oxidized and reduced nitrogen deposition. Across most of the United States, wet deposition has transitioned from being nitrate-dominated in the 1980s to ammonium-dominated in recent years. Ammonia has historically not been routinely measured because there are no specific regulatory requirements for its measurement. Recent expansion in ammonia observations, however, along with ongoing measurements of nitric acid and fine particle ammonium and nitrate, permit new insight into the balance of oxidized and reduced nitrogen in the total (wet + dry) US nitrogen deposition budget. Observations from 37 sites reveal that reduced nitrogen contributes, on average, ∼65% of the total inorganic nitrogen deposition budget. Dry deposition of ammonia plays an especially key role in nitrogen deposition, contributing from 19% to 65% in different regions. Future progress toward reducing US nitrogen deposition will be increasingly difficult without a reduction in ammonia emissions.

Preparation of nitric acid modified powder activated carbon to remove trace amount of Ni(II) in aqueous solution.

The present study investigated the preparation of nitric acid modified powder activated carbon (MPAC) and its adsorption of trace amounts of Ni(II) from aqueous solution. Results showed that raw powder activated carbon modified with 15% nitric acid (MPAC-15%) had the most developed pore structure and the highest adsorption efficiency for Ni(II) in aqueous solution. For MPAC-15%, the pore width was dominated by micropores with pore width about 1 nm and the total amount of chemical functional groups of MPAC-15% was 0.6630 mmol/g. Ni(II) adsorption tests indicated that the highest adsorption efficiency of MPAC-15% was 98%. The adsorption saturation time of MPAC-15% was about 120 min and the pH-dependent adsorption test showed that neutral conditions (6.5 < pH < 7.5) were suitable for Ni(II) adsorption. The adsorption kinetic analysis revealed that the pseudo-second order adsorption model fitted the adsorption process significantly. Thus, Ni(II) adsorption by MPAC-15% was dominated not only by physical adsorption via highly developed micropores but also by chemical adsorption between Ni(II) and surface functional groups. Adsorption isotherm analysis illustrated the Langmuir model was favorable for the adsorption of Ni(II), with R2 = 0.9874.

An optimised spectrophotometric assay for convenient and accurate quantitation of intracellular iron from iron oxide nanoparticles.

We report the development and optimisation of an assay for quantitating iron from iron oxide nanoparticles in biological matrices by using ferene-s, a chromogenic compound. The method is accurate, reliable and can be performed with basic equipment common to many laboratories making it convenient and inexpensive. The assay we have developed is suited for quantitation of iron in cell culture studies with iron oxide nanoparticles, which tend to manifest low levels of iron. The assay was validated with standard reference materials and with inductively coupled plasma-mass spectrometry (ICP-MS) to accurately measure iron concentrations ∼1 × 10-6 g in about 1 × 106 cells (∼1 × 10-12 g Fe per cell). The assay requires preparation and use of a working solution to which samples can be directly added without further processing. After overnight incubation, the absorbance can be measured with a standard UV/Vis spectrophotometer to provide iron concentration. Alternatively, for expedited processing, samples can be digested with concentrated nitric acid before addition to the working solution. Optimization studies demonstrated significant deviations accompany variable digestion times, highlighting the importance to ensure complete iron ion liberation from the nanoparticle or sample matrix to avoid underestimating iron concentration. When performed correctly, this method yields reliable iron ion concentration measurements to ∼2 × 10-6 M (1 × 10-7 g/ml sample).

Improvement of the Homogeneous Fenton Reaction for Degradation of Methylene Blue and Acid Orange II.

In this study, the degradation of methylene blue (MB) and acid orange II (ORII) by the Fenton reaction was improved by using HCl and HNO3. In addition, the effects of pH, temperature, concentration of Fenton's reagent, and adjustment reagent of solution pH on the decoloration were evaluated. The results showed that the optimal pH for decoloration of MB and ORII was 2.5 and that the decoloration of MB and ORII increased with higher temperature and concentration of Fenton's reagent. Moreover, the decoloration in the Fenton-reaction process with HCl and HNO3 was greater than the decoloration with H2SO4 by approximately 4.3-5.6 and 1.7-5.6 times for MB and 3.2-3.6 and 4.6-7.2 times for ORII compared to with H2SO4. These results indicated that Fenton-reaction with HCl and HNO3 could be useful for the degradation technology of dyes compared to generally Fenton-reactions.

Optimization of HNO3 leaching of copper from old AMD Athlon processors using response surface methodology.

The present study investigates the optimization of HNO3 leaching of Cu from old AMD Athlon processors under the effect of nitric acid concentration (%), temperature (°C) and ultrasonic power (W). The optimization study is carried out using response surface methodology with central composite rotatable design (CCRD). The ANOVA study concludes that the second degree polynomial model is fitted well to the fifteen experimental runs based on p-value (0.003), R2 (0.97) and Adj-R2 (0.914). The study shows that the temperature is the most significant process variable to the leaching concentration of Cu followed by nitric acid concentration. However, ultrasound power shows no significant impact on the leaching concentration. The optimum conditions were found to be 20% nitric acid concentration, 48.89 °C temperature and 5.52 W ultrasound power for attaining maximum concentration of 97.916 mg/l for Cu leaching in solution.

Nitric acid-anionic surfactant modified activated carbon to enhance cadmium(II) removal from wastewater: preparation conditions and physicochemical properties.

The authors used a nitric acid (HNO3)-sodium dodecyl benzene sulfonate (SDBS) method to modify a lignite-based activated carbon. These modified carbons were appraised for their removal of Cd(II) from aqueous solutions. Response surface methodology was employed to optimize the preparation factors including nitric acid concentration CN, temperature T and SDBS concentration CS. Statistical analysis indicated that the interaction of CN and CS incurred the most effect on the maximum cadmium adsorption capacity (Qm). The optimal Qm appeared at CN = 3.29 mol/L, T = 76 °C and CS=30,700 mg/L. The optimal protocol achieved 44.21 mg/g Qm for Cd(II) which was about 7 times larger than for this pristine lignite activated carbon (LAC) (6.78 mg/g). The physical-chemical properties of the modified activated carbons following each synthesis step were characterized relative to their surface area, oxygen functionality, and external surface charge. It was confirmed that the developed surface area, functional groups and negative charges were mainly responsible for the higher adsorption capacity for the LAC that have been more favorably tailored by this HNO3-SDBS protocol.

Effects of pH and coexisting chemicals on photolysis of perfluorooctane sulfonate using an excited xenon dimer lamp.

Vacuum ultraviolet (VUV) photolysis at the wavelength of 172 nm in a sulfate solution was introduced as a more efficient process for perfluorooctane sulfonate (PFOS) degradation than ultraviolet (UV) photolysis at 254 nm. The effects of pH and coexisting chemicals on VUV photolysis under the coexistence of 100 mM sulfate were investigated. VUV irradiation successfully degraded PFOS, and the degradation rate was 5.5 times higher than by UV photolysis. Direct VUV photolysis was inferred to mainly contribute to PFOS degradation. PFOS degradation by VUV irradiation was enhanced at pH less than 2 due to sulfate radicals generated via VUV photolysis of sulfate ions. Consequently, VUV photolysis was superior to UV photolysis for PFOS removal on both the removal rate and energy efficiency. However, the inorganic chemicals phosphoric acid and nitric acid strongly inhibited PFOS degradation, probably by masking PFOS from VUV rays by their VUV absorption. Accordingly, PFOS separation from inorganic materials such as phosphate and nitrate will be recommended for the application of VUV techniques for PFOS removal. In this research, organic solvent abstraction was inferred to be one of candidates for PFOS separation.

Phosphorus in recycling fertilizers - analytical challenges.

The importance of secondary raw materials for phosphorus (P) fertilizer production is expected to increase in the future due to resource depletion, supply risks, and heavy metal contamination of fossil phosphate resources. Municipal wastewater is a promising source for P recovery. In Germany for instance, it contains almost 50% of the total amount of P that is currently applied as mineral fertilizer. Several procedures have been developed to recover and re-use P resulting in a growing number of recycling fertilizers that are currently not regulated in terms of fertilizer efficiency. We tested various materials and matrices for their total P content, solubility of P in neutral ammonium citrate (Pnac) and water, and performed robustness tests to check if existing analytical methods are suitable for those new materials. Digestion with inverse aqua regia was best suited to determine the total P content. Pnac sample preparation and analyses were feasible for all matrices. However, we found significant time and temperature dependencies, especially for materials containing organic matter. Furthermore, several materials didn't reach equilibrium during the extractions. Thus, strict compliance of the test conditions is strongly recommended to achieve comparable results.

Heterogeneous Chemistry of Lipopolysaccharides with Gas-Phase Nitric Acid: Reactive Sites and Reaction Pathways.

Recent studies have shown that sea spray aerosol (SSA) has a size-dependent, complex composition consisting of biomolecules and biologically derived organic compounds in addition to salts. This additional chemical complexity most likely influences the heterogeneous reactivity of SSA, as these other components will have different reactive sites and reaction pathways. In this study, we focus on the reactivity of a class of particles derived from some of the biological components of sea spray aerosol including lipopolysaccharides (LPS) that undergo heterogeneous chemistry within the reactive sites of the biological molecule. Examples of these reactions and the relevant reactive sites are proposed as follows: R-COONa(s) + HNO3(g) → NaNO3 + R-COOH and R-HPO4Na(s) + HNO3(g) → NaNO3 + R-H2PO4. These reactions may be a heterogeneous pathway not only for sea spray aerosol but also for a variety of other types of atmospheric aerosol as well.

Heterogeneous Reactions of Limonene on Mineral Dust: Impacts of Adsorbed Water and Nitric Acid.

Biogenic volatile organic compounds (BVOCs), including the monoterpene limonene, are a major source of secondary organic aerosol (SOA). While gas-phase oxidation initiates the dominant pathway for BVOC conversion to SOA, recent studies have demonstrated that biogenic hydrocarbons can also directly react with acidic droplets. To investigate whether mineral dust may facilitate similar reactive uptake of biogenic hydrocarbons, we studied the heterogeneous reaction of limonene with mineral substrates using condensed-phase infrared spectroscopy and identified the formation of irreversibly adsorbed organic products. For kaolinite, Arizona Test Dust, and silica at 30% relative humidity, GC-MS identified limonene-1,2-diol as the dominant product with total organic surface concentrations on the order of (3-5) × 1018 molecules m-2. Experiments with 18O-labeled water support a mechanism initiated by oxidation of limonene by surface redox sites forming limonene oxide followed by water addition to the epoxide to form limonenediol. Limonene uptake on α-alumina, γ-alumina, and montmorillonite formed additional products in high yield, including carveol, carvone, limonene oxide, and α-terpineol. To model tropospheric processing of mineral aerosol, we also exposed each mineral substrate to gaseous nitric acid prior to limonene uptake and identified similar surface adsorbed products that were formed at rates 2 to 5 times faster than without nitrate coatings. The initial rate of reaction was linearly dependent on gaseous limonene concentration between 5 × 1012 and 5 × 1014 molecules cm-3 (0.22-20.5 ppm) consistent with an Eley-Rideal-type mechanism in which gaseous limonene reacts directly with reactive surface sites. Increasing relative humidity decreased the amount of surface adsorbed products indicating competitive adsorption of surface adsorbed water. Using a laminar flow tube reactor we measured the uptake coefficient for limonene on kaolinite at 25% RH to range from γ = 5.1 × 10-6 to 9.7 × 10-7. After adjusting for reactive surface areas, we estimate uptake coefficients for limonene on HNO3-processed mineral aerosol on the order of (1-6) × 10-6. Although this heterogeneous reaction will not impact the atmospheric lifetime of gaseous limonene, it does provide a new pathway for mineral aerosol to acquire secondary organic matter from biogenic hydrocarbons, which in turn will alter the physical properties of mineral dust.

Synthesis of high surface area carbon adsorbents prepared from pine sawdust-Onopordum acanthium L. for nonsteroidal anti-inflammatory drugs adsorption.

Chemically activated carbon materials prepared from pine sawdust-Onopordum acanthium L. were studied for the removal of diclofenac and naproxen from aqueous solution. Several carbons, using different proportions of precursors were obtained (carbon C1 to carbon C5) and the chemical modification by liquid acid and basic treatments of C1 were carried out. The textural properties of the carbons, evaluated by N2 adsorption-desorption isotherms, revealed that the treatments with nitric acid and potassium hydroxide dramatically reduced the specific surface area and the pore volume of the carbon samples. The surface chemistry characterization, made by thermal programmed decomposition studies, determination of isoelectric point and Boehm's titration, showed the major presence of lactone and phenol groups on the activated carbons surface, being higher the content when the acidic strength of the carbon increased. Diclofenac and naproxen kinetic data onto C1 carbon followed pseudo-second order model. The adsorption equilibrium isotherms of C1 and the modified carbons were well described by both Sips and GAB isotherm equations. The highest adsorption capacity was found for naproxen onto C1 activated carbon, 325 mg g(-1), since the liquid acid and basic functionalization of the carbon led to a severe decreasing in the adsorption removal of the target compounds.

Safe Synthesis of Alkylhydroxy and Alkylamino Nitramines.

Three different protocols for the syntheses of hydroxyalkylnitramines are presented and compared. Safety issues regarding the synthesis of nitramines are also discussed.