Evaporation Of Volatile Solvent Research Articles

The impact of time and storage conditions on samples containing OC pepper sprays on the quantitative ratios of capsaicinoids

Pepper sprays of the OC type constitute the majority of self-defense sprays available on the market. The active ingredient in these preparations is pepper extract: Oleoresin Capsicum, which contains capsaicinoids - natural compounds with irritant properties. Preparations from OC pepper sprays can be distinguished based on differences in the quantitative ratios of four main capsaicinoids: capsaicin, dihydrocapsaicin, nordihydrocapsaicin, and nonivamide. This raises the question whether information on the quantitative ratios of capsaicinoids can also provide answers to questions regarding comparisons of traces of OC preparations, such as whether traces revealed on the clothing of the victim could originate from an OC spray secured from the suspect, or whether traces on the clothing of the suspect and the victim could come from the same pepper spray. Such comparisons would be viable only if the capsaicinoid profile remained unchanged during evidence storage and as a result of solvent extraction from the tested material. The aim of the presented research was to determine if this is indeed the case. Model aging experiments were conducted to examine whether the capsaicinoid profile in traces of OC preparations changed over time and whether solvent extraction affected this profile. Samples of five different OC preparations were applied to cotton swabs, which, after the evaporation of volatile solvents, were placed in three types of packaging with varying levels of tightness and transparency (tight amber vials, polyethylene bags, paper envelopes). These prepared samples underwent solvent extraction with methanol and analysis using gas chromatography – mass spectrometry, after 28, 84, 147, 196, 252, and 301 days from preparation. The likelihood ratio (LR) was applied as a statistical tool to investigate the data obtained. The LR model was computed using the three variables based on the relative content of nordihydrocapsaicin, nonivamide, and dihydrocapsaicin. The cotton swabs used in the experiments served as a model for both the swabs used by the police for securing liquid evidence and the cotton clothing of individuals sprayed with OC pepper sprays. The findings of the conducted studies suggest that the quantitative relationships of capsaicinoids indeed change over time, both in preparations stored in original containers and in traces of these preparations present on clothing. For traces of OC preparations secured on swabs or present on clothing, these changes are more significant the longer the sample is stored and the less airtight the packaging used.

Tumbleweed-like aggregation-induced-emission microrobots: Swarming for ultra-tracing of hydrazine

Hydrazine (N2H4) poses severe health risks even in trace amounts due to the highly carcinogenic and teratogenic degeneration while it is frequently used in industrial products. However, current techniques are difficult to perform in-situ detection of N2H4 within confined sophisticated reactors or slim apparatus. Bioinspired by natural plant tumbleweed, we have demonstrated that swarming aggregation-induced emission microrobots (AIE-bots), which have a tumbleweed-like macroporous structure, are capable of performing motile-targeting detection of N2H4 leakage or accumulation. In this protocol, the AIE-bots are assembled from emulsion droplets containing AIEgens and hydrophobic Fe3O4 nanoparticles evenly distributed in CHCl3 and n-hexane through phase separation during the evaporation of volatile solvents. Upon the application of a precessing B(t), the AIE-bots can wobble in swarms and adaptively navigate through narrow channels without adjusting B(t). Additionally, they can efficiently ascend steep slopes with angles up to 45° due to the lightweight and coarse surface. While moving, the swarming AIE-bots can in-situ perceive the N2H4 concentration surrounding with an LOD of 3.81 ppb via fluorescence enhancement based on the Schiff base reaction. This work provides a microrobot detecting unknown toxin leakage or accumulation in hard-to-reach microenvironments, and will inspire the development of fluorescent micro-/nanorobots for intelligent motile sensing.

Highly ordered water droplet arrays on a volatile solvent surface

The condensation of water vapor on cold surfaces is termed as breath figures. It is fascinating that the highly ordered breath figure arrays can be formed by simple evaporation of a volatile polymer solution. It has been speculated that the ordered breath figure arrays originate from ordered water droplet arrays induced by the evaporation of volatile solvents. However, it is unknown what the real formation process of ordered water droplet arrays on volatile surfaces of pure solvents is. Herein, we report the real-time observation of the growth process of water droplets on the volatile surface of the pure solvent of carbon disulfide by using an optical microscope. We observed the highly ordered water droplet arrays on the volatile surface. We found six distinct stages during the evaporation process. The growth mechanism of water droplets obeys individual growth before coalescing. In addition, a few defects of large water droplets, vacancies and irregular boundaries were observed. The rapid movement of water droplets indicated the strong convective current in the solvent, promoting the rearrangement of water droplets to form more ordered arrays. The highly ordered water droplet arrays only need a moist environment, which is very convenient for ordered structures. Our findings not only provide direct evidence for ordered water droplet arrays but also quantitatively clarify their dynamic process, which helps to understand the mechanism of ordered breath figure arrays.

Designing and optimization of an electrochemical substitute for the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) cell viability assay

For the first time ever, this paper reports the development of an easily operated and cost-effective electrochemical assay to be used as an appropriate substitute for the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) cell viability assay. The proposed assay is based on the electrochemical reaction of Saccharomyces cerevisiae (S. cerevisiae) with toxic materials, and it overcomes most of the limitations of MTT such as evaporation of volatile solvents, cytotoxic effects of MTT reagents, high cost, and sensitivity to light. The novel electrochemical assay can be used to detect diazinon in the range of 10−6 g mL−1 to 10−2 g mL−1 with the detection limit of 1.5 × 10−7 g mL−1.

Fabrication of Multicompartment Particles via Sequential Micromolding Method

본 연구는 순차적인 마이크로 몰딩 방법을 이용한 고분자 다중 분획 입자 제조 방법에 관한 것이다. 다중 분획 입자는 poly(dimethylsiloxane)(PDMS) 마이크로 몰드 내로 단량체 혼합물의 주입, 휘발성 용매의 증발, 광중합으로 이루어지는 일련의 과정을 통해 제조한다. 이때, 단량체 혼합물에 포함된 휘발성 용매의 농도에 따라, 다중 분획입자를 구성하는 각 구획의 부피분율을 제어하는 것이 가능하다. 또한 단량체 혼합물의 농도 및 다중 분획 입자 제조공정의 반복횟수에 따라, 단일 입자, 이중 입자, 삼중 입자를 선택적으로 제조가 가능함을 보여준다. 제조한 각각의 다중 분획 입자에 형광염료를 함입하여 특정한 정보를 인코딩한 바코드 입자로써의 활용 가능성을 증명한다. 본 연구에서 제안하는 다중 분획 입자를 제조하기 위한 순차적인 마이크로 몰딩 방법은 쉽고, 빠르며, 고가의 장비를 필요로 하지 않는 장점을 가지며, 제조된 다중 분획 입자는 약물 저장 및 전달 소재, 바이오 센서, 그리고 선택적인 흡착-탈착을 유도할 수 있는 고감도 기능성 재료로서 응용이 가능할 것으로 기대한다.

Solvent resistant nanofiltration membrane based on polybenzimidazole

Polybenzimidazole (PBI) membranes with different morphology were prepared via traditional phase inversion method and applied in solvent resistant nanofiltration (SRNF) application. The morphology of the membranes was tuned via changing polymer concentration and adding volatile solvent in cast solutions. The morphology of the membranes was studied in detail by scanning electronic microscopy (SEM). The membranes show less macrovoids sublayer and denser skin layer with increasing polymer concentration in cast solution. The evaporation of volatile solvent is beneficial to forming a thicker skin layer. In this paper, PBI based membranes were also applied in the filtration of organic solvents, where dyes with different charge and size were selected to study the role of charge in solvent filtrations. The membranes showed more than 95% retention on positive charged MB (MW=160) in alcohol based medium, which is very promising for SRNF application.

Quantitative chromatographic analysis under changes in the composition of samples in the course of sample preparation: A modification of the double internal standard method

A well-known method of quantitative chromatographic analysis—the double internal standard method—is modified. This modification consists in the use of two analyte homologs (preceding and following ones) as standard substances. This approach can be used to compensate for considerable losses of both test components and standard substances in the course of various sample preparation procedures. The advantages of this method are illustrated using liquid extraction, vapor-phase analysis, distillation of volatile components with volatile solvents (preconcentration in a condensate), and evaporation of volatile solvents (preconcentration in a distillation residue) as examples. The method proposed maintains a high precision of determinations (the relative error (c specified − c found)/c specified is 1–6%).

Chromatographic quantitation at losses of analyte during sample preparation: Application of the modified method of double internal standard

Known methods of quantitative chromatographic analysis (calibration, external standard, internal standard and standard addition) require the application of sample preparation techniques without significant losses of analytes. If this condition cannot be satisfied, the compensation of these losses should be provided. The modification of known method of quantitative chromatographic analysis (double internal standard), implying the addition of two homologues (previous and following) of target analytes as internal standards into initial samples is considered. This approach permits us to compensate significant losses both analytes and standards at all stages of sample preparation. The advantages of this method are demonstrated on the examples of liquid–liquid extraction, head space analysis (HSA), distillation of volatile compounds with volatile solvents (concentration in condensates) and evaporation of volatile solvents (concentrating in the residues of solvents). In all cases the application of two homologues as internal standards provides accurate results (the typical relative errors are within 1–6%) at the values of a factor of composition distortion of initial samples ( K′, the definition is suggested) from 0.2 up to 4. These results are in accordance with general relationships between variations in any physicochemical properties of organic compounds within homologous series. The single found exception was the evaporation of volatile solvents (the open phase transition process) when to get the results with relative errors not more then +10% requires the minimal changes in the composition of initial samples ( K′ values should not be more then approximately 1.5).

Flow-through microdispenser for interfacing μ-HPLC to Raman and mid-IR spectroscopic detection

A flow-through microdispenser has been coupled to a micro HPLC separation system and used as a solvent elimination interface for Fourier transform infrared (FTIR) and Raman spectroscopic detection of the separated compounds. Using the microdispenser picoliter sized droplets can be generated and deposited on an appropriate target placed on a computerized x, y-stage. Evaporation of volatile solvent and buffer is rapid and allows analysis of the obtained dry deposits by various techniques. Due to the destruction free character of Raman and FTIR spectroscopy they can be applied sequentially to interrogate the same deposit. In the reported application five phenolic acids typically present in wine have been separated on a C-18 column technique using a mixture of water, methanol and acetic acid as mobile phase. For spectrum acquisition infrared and Raman microscopes have been used. The spectra recorded from the dried deposits of the separated compounds agreed well with the reference spectra of corresponding components.

Dermatopharmacology of ciclopirox nail lacquer topical solution 8% in the treatment of onychomycosis

Ciclopirox is a synthetic hydroxypyridone antifungal agent. In contrast to the azoles, glucuronidation is the main metabolic pathway of ciclopirox; therefore interactions with drugs metabolized via the cytochrome P450 system are unlikely. Ciclopirox is also distinct from the common systemic agents, which interfere with sterol biosynthesis. In fact, ciclopirox chelates trivalent cations (such as Fe3+), inhibits metal-dependent enzymes that are responsible for degradation of toxic metabolites in the fungal cells, and targets diverse metabolic (eg, respiratory) and energy producing processes in microbial cells. Ciclopirox is a broad spectrum antimicrobial with activity against all the usual dermatophytes as well as yeast and nondermatophyte molds. It has demonstrated activity against gram positive and negative bacteria, including resistant strains of Staphylococcus aureus. Ciclopirox exhibits fungal inhibitory activity (minimum inhibitory concentration < 4 μg/mL for dermatophytes) as well as fungicidal activity; to date resistance to the drug has not been identified. Ciclopirox has been formulated in a nail lacquer delivery system. After evaporation of volatile solvents in the lacquer, the concentration of ciclopirox in the remaining lacquer film reaches approximately 35%, providing a high concentration gradient for penetration into the nail. Radiolabel data demonstrate penetration into infected nails after only 1 application of the lacquer. Ciclopirox nail lacquer is a topical product that provides an active fungicidal agent in a delivery system capable of promoting nail penetration. With repeated applications, the antifungal agent is homogeneously distributed through all layers of the toenail achieving concentrations of ciclopirox in excess of inhibitory and fungicidal concentrations for most pathogens. Although ciclopirox readily penetrates nails, very low levels of ciclopirox are recoverable systemically, even after chronic use. Ciclopirox nail lacquer 8% is a topical product that provides an active fungicidal agent in a delivery system capable of penetrating nails. (J Am Acad Dermatol 2000;43:S57-69.)

Using filament stretching rheometry to predict strand formation and "processability" in adhesives and other non-Newtonian fluids

The spinning of polymeric fibers, the processing of numerous foodstuffs and the peel and tack characteristics of adhesives are all associated with the formation, stability and, ultimately, the longevity of thin fluid `strands'. This tendency to form strands is usually described in terms of the tackiness of the fluid or by heuristic concepts such as `stringiness' (Lakrout et al. J Adhesion 1999). The dynamics of such processes are complicated due to spatially and temporally non-homogeneous growth of extensional stresses, the action of capillary forces and the evaporation of volatile solvents. We describe the development and application of a simple instrument referred to as a microfilament rheometer (MFR) that can be used to readily differentiate between the dynamical response of different pressure-sensitive adhesive fluid formulations. The device relies on a quantitative observation of the rate of extensional thinning or `necking' of a thin viscous or viscoelastic fluid filament in which the solvent is free to evaporate across the free surface. This high-resolution measurement of the radial profile provides a direct indication of the ultimate time to break up of the fluid filament. This critical time is a sensitive function of the rheological properties of the fluid and the mass transfer characteristics of the solvent, and can be conveniently reported in terms of a new dimensionless quantity we refer to as a processability parameter P. We demonstrate the usefulness of this technique by presenting our results in the form of a case study in which we measure the visco-elasto-capillary thinning of slender liquid filaments for a number of different commercial polymer/solvent formulations and relate this to the reported processing performance of the materials. We also compare the MFR observations with the prediction of a simple 1D theory derived from the governing equations that model the capillary thinning of an adhesive filament.

Coating uniformity and device applicability of spin coated sol-gel PZT films

Important coating characteristics are discussed with an emphasis on understanding their impact on device reliability. The sources of thickness variations in relationship to the processing conditions imposed during spin coating and subsequent firing are described. In particular, evaporation of volatile solvents during spinning can cause thickness striations and vacuum-chuck marks. In addition, the crystallized microstructure may not be completely uniform, depending on the uniformity of substrate nucleation locations. These variations will impact the electrical reliability of the PZT devices which are made from these films. Thinner regions will have higher capacitance, but will be more susceptible to electrical degradation over time. Also, the scale of size uniformity in the microstructure can impact attempts to make smaller devices.

Rheology of microsphere formation and refinement

Two important steps in the fabrication of microsphere laser fusion targets have been analyzed by simple mathematical modeling. Volatile-containing droplets emerging from a nozzle with imposed oscillation first undergo a spontaneous blowing process, driven by the evaporation of volatile solvent which pushes the polymeric shell outward. These hollow particles then enter a refinement zone, where a centering process takes place to eliminate eccentricity between the shell internal and external surfaces. The confined vapor partially permeates to the surroundings, allowing shrinkage of the microspheres in this zone to the desired final dimensions and sphericity. Biaxial extensional flow dominates the rheology of micropshere expansion, whereas detailed dynamics of radial flow results in improved concentricity and sphericity. The effects of viscoelasticity on the rate and stress associated with microsphere expansion have been studied using the Newtonian and Maxwell constitutive equations. Simple analytic results to describe microsphere refinement have been obtained for conditions representative of the centering process where Newtonian behavior prevails as the fluid flow is relatively weak.

Evaporation of volatile solvent from saline multi-component droplets carried in a stream of air

We present a theoretical and experimental study on the evaporation of drops of radii 1–8 μm carried through a wind tunnel in a turbulent stream of air at 5 m/sec. Saline solutions are made of mixtures of two electrolytes, NaCl and CaCl 2, in different concentration ratios. It has been demonstrated previously (El Golli et al., 1974) that the lifetime of saline droplets depends on the solvent activity in the solution. Measurements of static vapour pressure of solutions of electrolyte mixtures have been made up to salt saturation and the results of these measurements have been used to determine the lifetime of droplets in different conditions of humidity and temperature. The theory described previously (valid for one electrolyte only) has been extented to solutions of mixed electrolytes. The experimental results have confirmed the validity of the proposed theoretical model.