Multipurpose cold injector for high resolution gas chromatography

The multipurpose cold injector described in this paper represents a solution for an universal sampling system for high resolution gas chromatography. The system is modular and is built around the Carlo Erba cold on-column injector provided with secondary cooling. An auxiliary module, easily fixable on the bottom of the on-column injector, creates a temperature programmable vaporizing chamber making the system also suitable for cold split-splitless injections or solvent venting prior to the sample transfer into the capillary. The system can be operated manually or in a fully automatic mode using the auto-sampler for cold on-column injections. The experimental data illustrate its benefits and limitations.     

Self‐Assembling Nanoparticles at Surfaces and Interfaces

Nanoparticles are the focus of much attention due to their astonishing properties and numerous possibilities for applications in nanotechnology. For realising versatile functions, assembly of nanoparticles in regular patterns on surfaces and at interfaces is required. Assembling nanoparticles generates new nanostructures, which have unforeseen collective, intrinsic physical properties. These properties can be exploited for multipurpose applications in nanoelectronics, spintronics, sensors, etc. This review surveys different techniques, currently employed and being developed, for assembling nanoparticles in to ordered nanostructures. In this endeavour, the principles and methods involved in the development of assemblies are discussed. Subsequently, different possibilities of nanoparticle‐based nanostructures, obtained in multi‐dimensions, are presented.     

The influence of the sample introduction system on signals of different tin compounds in inductively coupled plasma-based techniques

The influence of the sample introduction system on the signals obtained with different tin compounds in inductively coupled plasma (ICP) based techniques, i.e., ICP atomic emission spectrometry (ICP–AES) and ICP mass spectrometry (ICP–MS) has been studied. Signals for test solutions prepared from four different tin compounds (i.e., tin tetrachloride, monobutyltin, dibutyltin and di-tert-butyltin) in different solvents (methanol 0.8% (w/w), i-propanol 0.8% (w/w) and various acid matrices) have been measured by ICP–AES and ICP–MS. The results demonstrate a noticeable influence of the volatility of the tin compounds on their signals measured with both techniques. Thus, in agreement with the compound volatility, the highest signals are obtained for tin tetrachloride followed by di-tert-butyltin/monobutyltin and dibutyltin.The sample introduction system exerts an important effect on the amount of solution loading the plasma and, hence, on the relative signals afforded by the tin compounds in ICP–based techniques. Thus, when working with a pneumatic concentric nebulizer, the use of spray chambers affording high solvent transport efficiency to the plasma (such as cyclonic and single pass) or high spray chamber temperatures is recommended to minimize the influence of the tin chemical compound. Nevertheless, even when using the conventional pneumatic nebulizer coupled to the best spray chamber design (i.e., a single pass spray chamber), signals obtained for di-tert-butyltin/monobutyltin and dibutyltin are still around 10% and 30% lower than the corresponding signal for tin tetrachloride, respectively. When operating with a pneumatic microconcentric nebulizer coupled to a 50 °C-thermostated cinnabar spray chamber, all studied organotin compounds provided similar emission signals although about 60% lower than those obtained for tin tetrachloride. The use of an ultrasonic nebulizer coupled to a desolvation device provides the largest differences in the emission signals, among all tested systems.     

Sample validity in biological trace element and organic nutrient research studies

The complexities involved in dealing with the requirements of trace element research studies in the life sciences demand comprehensive planning of the investigations and use of a variety of techniques. It also requires a combination of biological insight and analytical awareness on the part of the investigators in order to obtain valid samples for analysis. Thus, the generation of meaningful conclusions from elemental composition studies on biological systems is a strictly multidisciplinary task, an approach that is vital for the overall success of the investigations. In addition, new initiatives are needed to produce multipurpose biological reference materials to cope with the growing demands of this multifaceted area of research. These aspects are discussed.     

Microanalysis by Laser Ablation-Inductively Coupled Plasma-Atomic Emission Spectrometry in Comparison to Spark Ablation of Certified and Found Minerals Galena, Sphalerite, and Pyrite

A double-tandem technique of inductively coupled plasma-atomic emission spectrometry (ICP-AES) involving laser ablation for the analysis of compact or briquetted minerals on one hand and spark ablation for the analysis of powders on the other is presented. The technical arrangement, the design of the optimized sample chamber, the evaluation of operating conditions, and the test of liquid-solid calibration are described. Both techniques can be used for the determination of elemental compositions of minerals providing a dynamic range from tens of mass-percent down to milligrams per kilogram. The objective of this study was to compare laser ablation (LA)-ICP-AES and spark-ICP-AES with regard to accuracy, precision, and sample turnaround time for multielement analysis of the certified minerals galena GF1, sphalerite SF1, and pyrite PS1. A systematic error of smaller than 3% in both techniques and a random error of smaller than 9 and 5%, respectively, is pointed out. The optimized methods were applied to samples of galena, sphalerite, and pyrite from four deposits each to find fingerprints by different contents of major, minor, and trace elements, which characterize the deposits.     

Comparison of a pump-around, a diffusion-driven, and a shear-driven system for the hybridization of mouse lung and testis total RNA on microarrays

In the present study, we demonstrate the benefits of a shear-driven rotating microchamber system for the enhancement of microarray hybridizations, by comparing the system with two commonly used hybridization techniques: purely diffusion-driven hybridization under coverslip and hybridization using a fully automated hybridization station, in which the sample is pumped in an oscillating manner. Starting from the same amount of DNA for the three different methods, a series of hybridization experiments using mouse lung and testis DNA is presented to demonstrate these benefits. The gain observed using the rotating microchamber is large: both in terms of analysis speed (up to tenfold increase) and in final spot intensity (up to sixfold increase). The gain is due to the combined effect of the hybridization chamber miniaturization (leading to a sample concentration increase if comparing iso-mass conditions) and the transport enhancement originating from the rotational shear-driven flow induced by the rotation of the chamber bottom wall.     

Measurements of Temperature and Electron Number Density in a dc Argon–Nitrogen Plasma Torch—Supersonic Operation

The diagnostics study on supersonic argon/nitrogen plasma jets expanded into a low-pressure test chamber is carried out by means of emission spectroscopy and enthalpy probe measurement techniques. The spatial distributions of electron density, temperatures, and associated shock structure effects in plasma jets are investigated in conjunction with their direct dependency upon the chamber pressure. The experimental results show the occurrence and the position of different zones; i.e., supersonic expansion, stationary shock waves and subsonic jet at pressures below 51 kPa. Flow fluctuations due to the oblique shock wave at 39 kPa background pressure are observed and discussed. The electron density profiles show variations along the plasma axis that coincide with the position of the shock waves. The experimental results show the transition from the moderately under-expanded to the strongly under-expanded jet structure induced by lowering of the chamber pressure.     

A broad frequency range dielectric spectrometer for colloidal suspensions: cell design, calibration, and validation

Electrode polarization complicates low-frequency measurements of the dielectric response of electrolyte solutions and colloidal suspensions. To deal with this longstanding problem, a new dielectric cell was developed along with a model based on the standard electrokinetic theory. The parallel plate cell utilizes a thin chamber that is easily filled and emptied; different chamber thicknesses are readily accommodated. The analytical form of the theoretical impedance model makes data analysis straightforward. Using standard electrolytes, the device and the theoretical model were tested over a wide range of frequencies for several electrolyte concentrations. Excellent agreement was found between the theory and the experimental data. The methodology developed to account for polarization effects exhibits a significant improvement over the conventional approaches and points up a deficiency in often-used equivalent circuit models.     

A laboratory comparison of two methods used to estimate the isotopic composition of soil delta13CO2 efflux at steady state

The stable isotopic composition of soil (13)CO(2) flux is important for monitoring soil biological and physical processes. While several methods exist to measure the isotopic composition of soil flux, we do not know how effective each method is at achieving this goal. To provide clear evidence of the accuracy of current measurement techniques we created a column filled with quartz sand through which a gas of known isotopic composition (-34.2 per thousand) and concentration (3,000 ppm) diffused for 7 h. We used a static chamber at equilibrium and a soil probe technique to test whether they could identify the isotopic signature of the known gas source. The static chamber is designed to identify the source gas isotopic composition when in equilibrium with the soil gas, and the soil probe method relies on a mixing model of samples withdrawn from three gas wells at different depths to identify the gas source. We sampled from ports installed along the side of the sand column to describe the isotopic and concentration gradient as well as to serve as a control for the soil probe. The soil probe produced similar isotopic and concentration values as the control ports, as well as Keeling intercepts. The static chamber at equilibrium did not identify the source gas but, when applied in a two end-member mixing model, did produce a similar Keeling intercept produced from the control ports. Neither of the methods was able to identify the source gas via the Keeling plot method probably because CO(2) profiles did not reach isotopic steady state. Our results showed that the static chamber at equilibrium should be used only with a Keeling plot approach and that the soil probe is able to provide estimates of uncertainty for the isotopic composition of soil gas as well as information pertinent to the soil profile.     

Fluorescence affinity sensing by using a self-contained fluid manoeuvring microfluidic chip

An application of a novel polymer microfluidic chip for sample exchange via natural capillary forces for immuno-analysis is described. The microfluidic device was designed to achieve sample replacement by capillary force only, which would therefore be suitable for point-of-care-testing. Complete and automatic replacement of the sample in the reaction chamber with another one makes the chip able to mimic affinity chromatography and immunoassay processes. The microfluidic chip was made using polymer replication techniques, which were suitable for fast and cheap fabrication. Micrometre-sized polystyrene beads were used for the functionalization of biomolecules. Dinitrophenyl (DNP) and anti-DNP antibody coordination was employed on the chip for fluorescence analysis. DNP was immobilized on the polymer beads via a pre-adsorbed dendrimer layer and the beads were placed in the reaction chamber. Fluorescein tagged anti-DNP was successfully observed by a fluorescence microscope after the completion of the entire flow sequence. A calibration curve was registered based on the anti-DNP concentration. A multiplex sensing was accomplished by adding biotin/streptavidin coordination to the system. DNP and biotin conjugated beads were placed in the reaction chamber in an ordered fashion and biospecific bindings of anti-DNP antibody and streptavidin were observed at their expected sites. A ratiometric analysis was carried out with different concentration ratios of anti-DNP/streptavidin. The microfluidic chip described in this work could be applied to various biological and chemical analyses using integrated washing steps or fluid replacement steps with minimum sample handling.     

Nitro-, Cyano-, and Methylfuroxans,and Their Bis-Derivatives: From Green Primary to Melt-Cast Explosives

In the present work, we studied in detail the thermochemistry, thermal stability, mechanical sensitivity, and detonation performance for 20 nitro-, cyano-, and methyl derivatives of 1,2,5-oxadiazole-2-oxide (furoxan), along with their bis-derivatives. For all species studied, we also determined the reliable values of the gas-phase formation enthalpies using highly accurate multilevel procedures W2-F12 and/or W1-F12 in conjunction with the atomization energy approach and isodesmic reactions with the domain-based local pair natural orbital (DLPNO) modifications of the coupled-cluster techniques. Apart from this, we proposed reliable benchmark values of the formation enthalpies of furoxan and a number of its (azo)bis-derivatives. Additionally, we reported the previously unknown crystal structure of 3-cyano-4-nitrofuroxan. Among the monocyclic compounds, 3-nitro-4-cyclopropyl and dicyano derivatives of furoxan outperformed trinitrotoluene, a benchmark melt-cast explosive, exhibited decent thermal stability (decomposition temperature >200 °C) and insensitivity to mechanical stimuli while having notable volatility and low melting points. In turn, 4,4′-azobis-dicarbamoyl furoxan is proposed as a substitute of pentaerythritol tetranitrate, a benchmark brisant high explosive. Finally, the application prospects of 3,3′-azobis-dinitro furoxan, one of the most powerful energetic materials synthesized up to date, are limited due to the tremendously high mechanical sensitivity of this compound. Overall, the investigated derivatives of furoxan comprise multipurpose green energetic materials, including primary, secondary, melt-cast, low-sensitive explosives, and an energetic liquid.     

Combined device for measuring of osmotic pressure, conductance, surface tension, and viscosity

Micro and multipurpose analytical tools are in high demand for procuring physicochemical data. Thereby conductance and specific conductance (κ), surface tension (γ) and viscosity (η) of 0.066 to 0.333 mol/kg urea and methylurea, the osmotic pressure (π) for 0.1 to 1.0 mol/kg sucrose with 0.01 mmol/kg aqueous KCl solutions simultaneously were studied with oscosurvismeter. The solutions of different compositions were taken in cells, partitioned by nitrocellulose semipermeable membrane (SPM) for osmotic pressure. Survismeter, osmometer, electrodes, metallic clamp, SPM and high potential metallic springs are key parts of the oscosurvismeter. The conductance data were in close agreement with those of Horiba Conductivity Meter DS-8 M, surface tension data with that of face automatic surface tensiometer, CBVP-Z, Kyowa Interface Science Co. Ltd., viscosity data with survismeter, Spectro Analytical Pvt Ltd. The conductance and viscosities for methylurea are higher than those of the urea with comparatively stronger hydrophobic interaction of the -CH₃ group of the methylurea. Statistical analysis of cost involved with oscosurvismeter was 99% less as compared with individual methods.     

Nanoperlite effect on thermal,rheological, surface and cellular properties of poly lactic acid/nanoperlite nanocomposites for multipurpose applications

In this study, poly lactic acid (PLA) based nanocomposites containing perlite nanoparticles were prepared by melt mixing method. Various characterization techniques were employed to evaluate the performance PLA/nanoperlite nanocomposites. The nanocomposites were characterized via FTIR to investigate the functional groups and chemical structure of the nanocomposites. Thermal properties of the nanocomposites, examined by DSC, showed that the increase of nano-perlite content in the PLA matrix reduces the crystallinity and melting temperature of the nanocomposites. The rheological studies indicated that both of storage and loss modulus are increased when the nanoperlite is added up to 5 wt%. However, the modulus is reduced in samples containing more than 5 wt% nanoparticle due to their agglomeration. The in-vitro degradation studies of the nanocomposites at elevated and normal temperatures showed hydrolytic degradation around 13–15 months. The surface behavior results implied that the water contact angle values exhibit a reducing trend when the nanoperlite content increases up to 3 wt%, which can be related to the decreased crystallinity of PLA and also to the hydrophilic nature of perlite. Moreover, the adhesion of osteoblast cells and their viability on an electrospun scaffold, made of optimized sample, showed the initial implications of potential applications of the nanocomposites in bone regeneration and biomedical applications. These multipurpose nanocomposites can also be used for packaging applications.     

A large volume, portable, real-time PCR reactor

A point-of-care, diagnostic system incorporating a portable thermal cycler and a compact fluorescent detector for real-time, polymerase chain reaction (PCR) on disposable, plastic microfluidic reactors with relatively large reaction volume (ranging from 10 μL to 100 μL) is described. To maintain temperature uniformity and a relatively fast temperature ramping rate, the system utilizes double-sided heater that features a master, thermoelectric element and a thermal waveguide connected to a second thermoelectric element. The waveguide has an aperture for optical coupling between a miniature, fluorescent reader and the PCR reaction chamber. The temperature control is accomplished with a modified, feedforward, variable structural proportional-integral-derivative controller. The temperature of the liquid in the reaction chamber tracks the set-point temperature with an accuracy of ± 0.1 °C. The transition times from one temperature to another are minimized with controllable overshoots (< 2 °C) and undershoots (< 5 °C). The disposable, single-use PCR chip can be quickly inserted into a thermal cycler/reader unit for point-of-care diagnostics applications. The large reaction chamber allows convenient pre-storing of dried, paraffin-encapsulated PCR reagents (polymerase, primers, dNTPs, dyes, and buffers) in the PCR chamber. The reagents are reconstituted "just in time" by heating during the PCR process. The system was tested with viral and bacterial nucleic acid targets.     

Column properties and flow profiles of a flat, wide column for high-pressure liquid chromatography

The design and the construction of a pressurized, flat, wide column for high-performance liquid chromatography (HPLC) are described. This apparatus, which is derived from instruments that implement over-pressured thin layer chromatography, can carry out only uni-dimensional chromatographic separations. However, it is intended to be the first step in the development of more powerful instruments that will be able to carry out two-dimensional chromatographic separations, in which case, the first separation would be a space-based separation, LC(x), taking place along one side of the bed and the second separation would be a time-based separation, LC(t), as in classical HPLC but proceeding along the flat column, not along a tube. The apparatus described consists of a pressurization chamber made of a Plexiglas block and a column chamber made of stainless steel. These two chambers are separated by a thin Mylar membrane. The column chamber is a cavity which is filled with a thick layer (ca. 1mm) of the stationary phase. Suitable solvent inlet and outlet ports are located on two opposite sides of the sorbent layer. The design allows the preparation of a homogenous sorbent layer suitable to be used as a chromatographic column, the achievement of effective seals of the stationary phase layer against the chamber edges, and the homogenous flow of the mobile phase along the chamber. The entire width of the sorbent layer area can be used to develop separations or elute samples. The reproducible performance of the apparatus is demonstrated by the chromatographic separations of different dyes. This instrument is essentially designed for testing detector arrays to be used in a two-dimensional LC(x) x LC(t) instrument. The further development of two-dimension separation chromatographs based on the apparatus described is sketched.     

Hydrophilic strips for preventing air bubble formation in a microfluidic chamber

In a microfluidic chamber, unwanted formation of air bubbles is a critical problem. Here, we present a hydrophilic strip array that prevents air bubble formation in a microfluidic chamber. The array is located on the top surface of the chamber, which has a large variation in width, and consists of a repeated arrangement of super‐ and moderately hydrophilic strips. This repeated arrangement allows a flat meniscus (i.e. liquid front) to form when various solutions consisting of a single stream or two parallel streams with different hydrophilicities move through the chamber. The flat meniscus produced by the array completely prevents the formation of bubbles. Without the array in the chamber, the meniscus shape is highly convex, and bubbles frequently form in the chamber. This hydrophilic strip array will facilitate the use of a microfluidic chamber with a large variation in width for various microfluidic applications.     

N,N-dimethylformamide: a multipurpose building block

Often used as a common solvent for chemical reations and utilized widely in industry as a reagent, N,N-dimethylformamide (DMF) has played an important role in organic synthesis for a long time. Numerous highly useful articles and reviews discussing its utilizations have been published. With a focus on the performance of DMF as a multipurpose precursor for various units in numerous reactions, this Minireview summarizes recent developments in the employment of DMF in the fields of formylation, aminocarbonylation, amination, amidation, and cyanation, as well as its reaction with arynes.     

Preparation of Ionic Liquid‐based Vilsmier Reagent from Novel Multi‐purpose Dimethyl Formamide‐like Ionic Liquid and Its Application

In continuation of research to explore the applied potential of DMF‐like ionic liquid, the ionic liquid version of N,N‐dimethyliminiumchloride (Vilsmier reagent) has been synthesized from DMF‐like ionic liquid and tested effectively for its capacity to achieve more useful organic transformations. The results show that DMF‐like ionic liquid is world's first task specific ionic liquid which has catalyzed numerous diverse type of reaction and is multipurpose in its application. Thus a new term for this DMF‐like ionic liquid has been coined that is DMF‐like "multipurpose" ionic liquid.     

Pervaporation-gas chromatography coupling for slurry samples. Determination of acetaldehyde and acetone in food

The use of pervaporation for the removal of volatile species from slurry samples, with a full automated introduction of the sample into the lower chamber of the pervaporation unit prior to their individual separation and determination by gas chromatography-flame ionisation detection, is presented for the first time. For this purpose, the upper chamber of the pervaporator is situated in the loop of an HPLC injection valve and the only requirement of the experimental setup for being used with slurries is to have adequately sized diameters for the units of the dynamic manifold assisting the donor chamber in order to avoid clogging by the suspended particles. The method developed was applied to the determination of acetaldehyde and acetone in food samples with different solids contents, such as yoghurt, Actimel and different kind of juices.