Fabrication of Micron Level Particles of Amoxicillin by Rapid Expansion of Supercritical Solution

In this study, the rapid expansion of supercritical solution (RESS) process was used to precipitate fine solid particles of amoxiccilin where supercritical carbon dioxide was used as a solvent. The process has been done by changing the RESS parameters, including extraction pressure (150–210 bar), extraction temperature (313–333 K), nozzle length (2–15 mm), effective nozzle diameter (450–1700 µm), and spraying distance (1–10 cm), to investigate the effect of these parameters on the size and morphology of the precipitated amoxicillin particles. The characterization (size and morphology) of the particles was examined using scanning electron microscopy (SEM). Based on the different experimental conditions, the mean particle size of the fabricated particles were between 1.08 and 5.72 µm, while the intact particles of amoxicillin were about 41.46 µm. Also, no regular changes in the morphology of the processed particles were observed.     

Contact Angle Measurement for Dispersed Microspheres Using Scanning Confocal Microscopy

Abstract

Scanning confocal microscopy was used for contact angle measurement of individual microspheres. The measurements were carried out by using different laser‐scanned layers of the particle floating on the air–water interface. The ratio of the diameter for the cross‐section of the protruded area of the particle at the air–water interface to the actual diameter of the particle is used for contact angle measurements. Two systems, i.e., glass and polystyrene microspheres with diameters of 3–10 and 6 µm, respectively, with water were used for this investigation (this size range of particles are most relevant to inhalation applications). Using the developed methodology, contact angles of 27° and 41° were measured (with water) for glass and polystyrene particles, respectively. The theoretical error in contact angle measurement for the developed methodology is determined to be generally about 1° with a maximum of 3° for contact angle of particles ranging from 2 to 24 µm in size; the experimental error was 4–6°. The contact angles of glass and polystyrene particles were compared to those obtained from pendant drop method and confirmed.     

Micronization of Iron Oxide Particles Using Gas Antisolvent Process

Iron oxide particles were micronized by supercritical carbon dioxide (CO₂) as an antisolvent in a batch gas antisolvent (GAS) process. In the present study, the feasibility of GAS process to micronize the iron oxide particles using dimethyl sulfoxide (DMSO) as a solvent was investigated. In this direction, particle size and morphology changes were investigated with changing solution pressure (80–150 bar), temperature (308.15–328.15 K), and concentration (1.5–6 g/l). Based on the different experimental conditions, the particle size of the original iron oxide was decreased in the range of 17.25 to 4.23 µm, which shows a the success of the GAS process to reduce the particle size of the intact iron oxide particles. Simultaneously, morphology changes were observed starting from the irregular morphology for synthesized particles to more regular shapes that included fused and spherical-fused particles.     

Characterization of size‐segregated aerosols using ToF‐SIMS imaging and depth profiling

Size‐segregated particles were collected with a ten‐stage micro‐orifice uniform deposit impactor from a busy walkway in a downtown area of Hong Kong. The surface chemical compositions of aerosol samples from each stage were analyzed using time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) operated in the static mode. The ToF‐SIMS spectra of particles from stage 2 (5.6–10 µm), stage 6 (0.56–1 µm), and stage 10 (0.056–0.1 µm) were compared, and the positive ion spectra from stage 2 to stage 10 were analyzed with principal component analysis (PCA). Both spectral analysis and PCA results show that the coarse‐mode particles were associated with inorganic ions, while the fine particles were associated with organic ions. PCA results further show that the particle surface compositions were size dependent. Particles from the same mode exhibited more similar surface features. Particles from stage 2 (5.6–10 µm), stage 6 (0.56–1 µm), and stage 10 (0.056–0.1 µm) were further selected as representatives of the three modes, and the chemical compositions of these modes of particles were examined using ToF‐SIMS imaging and depth profiling. The results reveal a non‐uniform chemical distribution from the outer to the inner layer of the particles. The coarse‐mode particles were shown to contain inorganic salts beneath the organics surface. The accumulation‐mode particles contained sulfate, nitrate, ammonium salts, and silicate in the regions below a thick surface layer of organic species. The nucleation‐mode particles consisted mainly of soot particles with a surface coated with sulfate, hydrocarbons, and, possibly, fullerenic carbon. The study demonstrated the capability of ToF‐SIMS depth profiling and imaging in characterizing both the surface and the region beneath the surface of aerosol particles. It also revealed the complex heterogeneity of chemical composition in size and depth distributions of atmospheric particles. Copyright © 2014 John Wiley & Sons, Ltd.     

The Development and Validation of a Liquid Chromatography–Tandem Mass Spectrometry Procedure for the Determination of Dioctyldiethylenetriamine Acetate Residues in Soil,Green and Cured Tobacco Leaves Using a Modified QuEChERS Approach

A liquid chromatography with electrospray ionization tandem mass spectrometry method was developed and validated for the determination of dioctyldiethylenetriamine acetate in soil and tobacco. The separation was performed on a Restek Ultra AQ C₁₈ column (2.1?×?100 mm i.d., particle size 3 µm) at 40 °C with a gradient elution. Methanol and trifluoroacetic acid (0.1%) were used as mobile phase, and the flow rate was set at 0.3 mL min^?1. A modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was used for sample extraction and cleanup pretreatment. The recovery was tested in the real samples and calculated to be 86.3–97.4%, the relative standard deviations were 1.1–11.9%. The limits of detection and quantitation were 3.3–16.7 and 10–50 µg kg^?1, respectively. The method was demonstrated to be reliable for the routine monitoring of dioctyldiethylenetriamine acetate in tobacco samples.     

Study on the Plugging Ability of Polymer Gel Particle for the Profile Control in Reservoir

Polymer gel particle is a widely used deep profile control agent to plug the water breakthrough channel in reservoir. However, there is still no theoretical model to describe its plugging ability available when it is applicated. Based on the Hertz contact theory and force analysis, the plugging model of polymer gel particle is established at the view of pore throat, and the parameters in the model are achieved by the pore throat experiments. The plugging model is verified by the core experiments. The results show that the plugging strength of polymer gel particle keeps rise with the increasing of the ratio between particle diameter and pore throat size, and then it will stay at a stable value because of the limitation of material strength. The material strength is 0.32 MPa and the particle will be broken when the size ratio is over 3. The plugging strength of the polymer gel particles with the diameters of 30–40 µm and 60–80 µm is 0.12 and 0.31 MPa in the cores with the permeability of 2989.6 × 10^?3 and 3014.7 × 10^?3 µm², respectively, which is consistent perfectly with the theoretical calculation. The plugging model of polymer gel particle is verified to be correct and can be applied to the profile control in reservoir.     

Preparation and characterization of 2,4–D butyl ester capsule suspension for mitigation of its drift risk

A novel capsule suspension (CS) formulation was prepared by in situ polymerization of melamine formaldehyde (MF) resin which was the first time to be used to encapsulate 2,4–D butyl ester. The prepared 2,4–D butyl ester capsule suspensions were studied by ultraviolet spectrophotometer (UV), laser particle size analyzer, Optical microscopy (OM), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Results showed that the encapsulation efficiency reached 93.23%, and the mean particle size (D₅₀) could be reduced to 13.80 µm by adding 4% Tween80. OM and SEM images illustrated that the core-shell structure related largely to the stability of emulsion. The spherical microcapsules possessed with rougher outer surface and the shell was about 1.5-2.0 µm thick with good methanol tolerance. Then, the formation of pre-polymer, shell material and microcapsules were revealed by FT-IR. Finally, experiments showed that the 2,4–D butyl ester CS exhibited a sustained releasing behavior in water, which could reach to 14 days.     

Ionic-Liquid-Based Infrared-Assisted Extraction (IL-IRAE) Coupled with HPLC–MS: a Green and Convenient Tool for Determination of TCMs

Infrared radiation, one form of electromagnetic wave, has potential value due to its heating effect, but has become a matter of grave concern in recent years. We describe herein ionic-liquid-based infrared-assisted extraction (IL-IRAE) coupled with high-performance liquid chromatography (HPLC)–mass spectrometry (MS) as a green and convenient method for simultaneous determination of three alkaloids in Lycoris radiata, a traditional Chinese medicine (TCM). Extraction parameters including the type and concentration of IL, extraction solvent, liquid/solid ratio, extraction time, and irradiation power were optimized via orthogonal design and analysis of variance (ANOVA). Chromatography–mass spectrometry was performed in positive ion mode on a TSK gel C₁₈ column (150 mm × 4.6 mm id, 5-µm particle size) with less than 5-min separation. Evaluation of the method showed good results with analytical recovery ranging from 100.66 to 103.90 %. The extraction efficiency of IL-IRAE was proved to be increased by 25 % compared with conventional heat reflux extraction (HRE), ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE) methods under the operational parameters investigated in the study, indicating that the developed IL-IRAE method is environmentally friendly, simple, low cost, and efficient, offering great promise for quick determination of active compounds in TCMs and natural plants.     

Recovery improvement of coarse particles by stage addition of reagents in industrial copper flotation circuit

Obtaining high recovery in coarse particle size fractions has been always under investigation in recent years. In the present study, stage addition of chemical reagents is used to improve copper grade and recovery of coarse size fractions (i.e., >100 µm) at industrial rougher flotation cells. Due to the poor efficiency of primary grinding circuit, coarse particles were detected as predominate size fraction in rougher flotation feed. Sampling results from rougher tailings showed that 58% of precious copper minerals were distributed to size fraction of ?105 + 297 µm. Stage addition of collectors including sodium isopropyl xanthate (Z11), dithiophosphate and mercaptobenzthiazole (Nascol-451), and xanthate-flomin (C-4132) and frothers as methyl isobutyl carbonyl (MIBC) and Aerofroth 65 (A65) were implemented to avoid losing of coarse valuable particles in rougher tailings. Three different patterns were given for stage additions as 75-25-0, 75-0-25, and 75-13-12. The results indicated that copper grade of tailings declined relatively 56% using optimized stage addition of reagents at the head of rougher banks (i.e., 75-13-12). In addition, copper recovery of rougher cells improved around 2%. Size by size analysis of copper recovery for the rougher cells revealed the significant effect of the stage addition of chemical reagents on recovery improvement of coarse particles.     

Particle Production in Reflection and Transmission Mode Laser Ablation: Implications for Laserspray Ionization

Particles were ablated from laser desorption and inlet ionization matrix thin films with a UV laser in reflection and transmission geometries. Particle size distributions were measured with a combined scanning mobility particle sizer (SMPS) and aerodynamic particle sizer (APS) system that measured particles in the size range from 10 nm to 20 μm. The matrixes investigated were 2,5-dihydroxybenzoic acid (DHB), α-cyano-4-hydroxycinnamic acid (CHCA), sinapic acid (SA), 2,5-dihydroxy-acetophenone (DHAP), and 2-nitrophloroglucinol (NPG). Nanoparticles with average diameters between 20 and 120 nm were observed in both transmission and reflection geometry. The particle mass distribution was significantly different in reflection and transmission geometry. In reflection geometry, approximately equal mass was distributed between particles in the 20 to 450 nm range of diameters and particles in the 450 nm to 1.5 μm diameter range. In transmission mode, the particle mass distribution was dominated by large particles in the 2 to 20 μm diameter range. Ablation of inlet ionization matrices DHAP and NPG produced particles that were 3 to 4 times smaller compared with the other matrices. The results are consistent with ion formation by nanoparticle melting and breakup or melting and breakup of the large particles through contact with heated inlet surfaces.

Evaluation of the Analytical Potentialities of a Composite Electrode Modified with Molecularly Imprinted Polymers

Abstract

The preparation of a methacrylate polymer molecularly imprinted (MIP) with paracetamol (APAP) was performed. After extraction of the APAP template molecule, the MIPs were incorporated into a graphite–polyurethane (GPU) matrix, and the resulting composites were used to prepare modified electrodes intended to be used in APAP determination. The best results were found using a 2.5% MIP in the GPU electrode and a 500-µm MIP particle size. This electrode was used in the determination of APAP in pharmaceutical formulations, reaching a 6.7 × 10^?8 mol L^?1 limit of detection. The 2.5% MIP-GPU-modified electrode showed better sensitivity than the nonimprinted methacrylate GPU-modified electrodes. Interference of phenacetin in the APAP response decreased remarkably when the proposed electrode was used.     

Preparation and Chromatographic Features of Fibrous Core–Shell HPLC Packing Material

In this study, fibrous core–shell silica particles were successfully synthesized via a one-step oil–water biphase stratification coating strategy. The core–shell silica particles were composed of 3-µm non-pore silica cores and thin shells (50–100 nm), which have radial-like direct channels and a large pore size (19.89 nm). The fibrous core–shell silica particles were further modified by n-octadecyltrichlorosilane and used as stationary-phase media in high-performance liquid chromatography (HPLC). The chromatographic properties of the particles were systematically studied in small-molecule and protein separation processes. The results showed that the back pressure was as low as 8.5 MPa under the 1.0-mL min^?1 flow velocity. Furthermore, fibrous core–shell silica particles with an 80-nm shell were used for separating seven small molecules within 10 min and six proteins within 6 min. This work demonstrates that the fibrous core–shell silica particles could be used as an HPLC stationary phase with good performance and low back pressure, and that they have great potential for application to HPLC separation in the future.     

Optimization of large-scale chromatography for biotechnological applications

An economic evaluation of a chromatographic separation is discussed. The effects of particle size, cycle time, solvent, and column costs are analyzed. With small particles (<20 µm), the cost of the packing can be as much as 99% of the total cost of the process, whereas with large particles (>60 µm), resin costs are less than half of the total. A strong optimum is found between 20–40 µm for maximum productivity, using both Gaussian models and the mass transfer model of Lapidus and Amundson to generate peaks. A new compilation of resin costs, column costs, and pump costs is given.

     

Source apportionment of atmospheric carbonaceous particulate matter based on the radiocarbon

A method was established to quantitatively estimate sources of atmospheric carbonaceous matter, using a combination of radiocarbon technology, linear regression of organic carbon (OC) -K⁺ and elemental carbon (EC) tracer method. Fractional contributions of fossil fuels, biomass burning, biogenic secondary organic carbon (BSOC) and soil dust to the atmospheric size-resolved carbonaceous matters in Shanghai suburb were estimated using this new method. The fossil carbon contributed most of the OC in particles smaller than 0.49 μm, and its fraction decreased with the increase of particle size. Biomass burning contributed 17–28 % to the OC. The BSOC contributed comparable proportions to the OC in particles smaller than 3.0 μm with the biomass burning, but larger in the particles lager than 3.0 μm. The soil dust contributed least fraction to the OC of each size with a proportion of 2–13 %. The biomass burning and fossil sources shared comparable fraction of the EC in all size range.     

Sustainable stabilization of oil in water emulsions by cellulose nanocrystals synthesized from deep eutectic solvents

There is an urgent global need to develop novel types of environmentally safe dispersing chemicals from renewable resources in order to reduce the environmental impact of oil spills. For this goal, cellulose, the most abundant natural polymeric source, is a promising green, nontoxic alternative that could replace the current synthetic surfactants. In this study, cellulose nanocrystals (CNC) synthesized using a deep eutectic solvent (DES) and two commercially available cellulose nanocrystals were used as marine diesel oil–water Pickering emulsion stabilizers. In particular, oil in water (o/w) emulsion formation and stability of emulsified oil during storing were addressed using a laser diffraction particle size analyzer, image analysis, and oil emulsion volume examination. The particle size of the o/w reference without CNCs after dispersing was over 50 µm and coalescence occurred only a few minutes after the emulsifying mixing procedure. All three investigated CNCs were effective stabilizers for the o/w system (oil droplets size under 10 µm) by preventing the oil droplet coalescence over time (6 weeks) and resulting in a stable creaming layer. The CNCs prepared using green DES systems boasted performance comparable to that of commercial CNCs, and they showed effectiveness at 0.1% dispersant dosage.     

Microstructure evolution in Stöber-type silica nanoparticles and their in vitro apatite deposition

Prepared via Stöber-type sol–gel routes were three types of silica particles of <1 μm in size: pure silica, Ca-involving silica, and chitosan/alginate-coated silica with a polymershell-silica core structure. Calcium ions were impregnated in the organic layers of the polymer-coated silica particle. The sol–gel procedure was applied to tetraethoxysilane dissolved in an ethanol/water mixture, while Ca–silica was derived from CaCl₂-containing ethanol/water solutions. Scanning and transmission electron micrograph analyses indicated that those silica particles consisted of ~10 nm primary particles, the Ca–silica particles (~500 nm) were larger than the Ca-free ones (~200 nm) and that their size increased with the Ca concentration in the precursor solutions. From ¹H- and ²⁹Si- magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra and ²⁹Si cross-polarization NMR spectra, the mechanism of primary particle agglomeration and degradation of the secondary particles in saline were discussed in terms of the content of H₂O molecules and >Si–OH as well as hydrogen bonding interactions among them. In addition, the Ca–silica and core-shell silica deposited apatite in Kokubo’s simulated body fluid. Thus, the present Ca–silica and polymer-coated silica particles were suggested to be applicable to injectable bone fillers for bone generation.     

Modified reverse microemulsion synthesis for iron oxide/silica core–shell colloidal particles

Iron oxide/silica core–shell colloidal particles were prepared by basic reverse microemulsion (RM) method and two modified RM methods. By basic RM method, maximum particle size obtained was mere 40 nm. For building photonic crystals working in the visible range, the colloidal particles must be larger than 100 nm. Thus two modified RM methods were used. By alcohol modified RM method, short chain alcohols were used as co-surfactant. The particle size rose to near 100 nm, but the core–shell structure was comparatively poor. By emulsifier pair modified RM method, the particle size leapt to over 200 nm and a narrow growth window was found favorable to enhance the stability and rigidity of the surfactants layers. The core–shell mechanism was also discussed and a new four-step mechanism was proposed.     

Determination of Carbamate and Benzoylurea Insecticides in Peach Juice Drink by Floated Organic Drop Microextraction–High Performance Liquid Chromatography

Abstract

Floated organic drop microextraction (FDME)–high performance liquid chromatography (HPLC) has been developed for extraction and determination of carbamate and benzoylurea insecticide residues from peach juice drink samples. The components were separated by a Diamonsil C18 instrument (5 µm, 250 mm × 4.6 mm i.d.). The mobile phase was a mixture of acetonitrile, methanol, and water (the ratio of volume was 18:70:12). Factors relevant to the extraction efficiency were studied and optimized. The methodology exhibited good linearity between 0.01 and 10.0 µg/mL with a correlation coefficiency of 0.9999. The average recovery of pesticides ranged from 88.49% to 101.86%. The relative standard deviations (RSDs) (n = 6) were 1.99–3.47%.     

Low temperature pyrolysis of carboxymethylcellulose

Unlike the common high temperature pyrolysis of carboxymethylcellulose (CMC) targeting activated carbon, this study investigates the pyrolytic behaviour of plain CMC at low temperatures ranging between 260 and 300 °C. Preliminary experiments were conducted using differential scanning calorimetry to define the temperature range necessary for the process. Low-temperature pyrolysis was then simulated using thermogravimetric analysis under inert atmosphere. Investigations reveal that a minimum holding temperature of 260 °C is required for an isothermal process, at which pyrolysis is terminated after around 26 min. Increasing exposure temperature reduces pyrolysis time. Within the range of the investigated sample and CMC particle size, no significant effects could be measured regarding the decomposition behaviour. The resulting char was further analysed using X-ray diffraction and Fourier transform infrared spectroscopy. Visual inspection was conducted using scanning electron microscopy. Upon pyrolysis, originally longitudinally shaped CMC was found to be converted into spherical particles of functionalised amorphous carbon with an average particle size of 41 µm.     

Poly(PEGDMA‐MAA) copolymeric micro and nanoparticles for oral insulin delivery

Poly(ethylene glycol) dimethacrylate (PEGDMA) and methacrylic acid (MAA) based micro and nanoparticles were prepared and evaluated as a carrier for oral delivery of insulin. PEGDMA was synthesized by esterification reaction of the PEG4000 with MAA in the presence of an acid catalyst. Particles of different size were prepared by emulsion polymerization reaction using different concentration of sodium lauryl sulphate (SLS) as an emulsifying agent. Synthesized copolymeric particle were characterized by attenuated total reflectance‐Fourier transform infrared spectroscopy (ATR‐FTIR), scanning electron microscopy, and acid value. The mean particle diameter of the polymeric micro and nanoparticles at various physiologically relevant pH values was measured using dynamic light scattering. Insulin loading efficiency of the particles was found to be directly proportional to the particle size and inversely proportional to the acid value of the particles. In vitro insulin release studies from various insulin loaded particles were performed by simulating the gastrointestinal tract conditions using HPLC. At pH 2.5, the release of insulin from polymeric particles was observed in the range of 5–8% while a significant higher release (20–35%) was observed at pH 7.4 during first 15 min of in vitro release. Largest size copolymeric particles of 8.3 µm also showed the highest efficiency to reduce the blood glucose level in diabetic rabbits. Copyright © 2010 John Wiley & Sons, Ltd.