The development of fieldable laser-induced breakdown spectrometer: No limits on the horizon

In this review, new trends in the development of fieldable instrumentation based on laser-induced breakdown spectroscopy (LIBS) and its recent applications is presented. Depending on the LIBS configuration we will distinguish between portable, remote and stand-off instruments. Moreover, the development of portable systems gives greater flexibility and also increases the range of LIBS applications. In general, portable instruments are employed in close-contact applications like immovable artworks, contaminated soils and environmental diagnostic, while remote and stand-off instruments are normally used in analytical applications at distances where access to the sample is difficult or hazardous. Although remote and stand-off instruments are both used for chemical analysis at distances, the instrumental configurations are completely different. In remote analysis, an optical fiber is employed to deliver the laser energy a certain distance. This approach has been usually restricted to industrial applications, bulk analysis in water, geological measurements and chemical analysis on nuclear stations. In the case of stand-off applications, the laser beam and the returning plasma light are transmitted in an open-path configuration. In this article we also discuss the instrumental requirements in the design of remote and stand-off instruments.     

Application of liquid chromatography/quadrupole time-of-flight mass spectrometry (LC-QqTOF-MS) in the environmental analysis

This paper gives an overview of the potentials of liquid chromatography-hybrid quadrupole time-of-flight mass spectrometry (LC-QqTOF) in the environmental analysis. Examples of applications of QqTOF instruments for target analysis of pharmaceuticals and pesticides are presented and discussed, as well as applications aimed on the identification of unknown compounds present in environmental waters or on the elucidation of structures of biodegradation and photodegradation products. Specific issues such as uncertainty of mass measurement and quantitative performances are discussed in details.     

Applications of solid-phase microextraction in food analysis

Food analysis is important for the evaluation of the nutritional value and quality of fresh and processed products, and for monitoring food additives and other toxic contaminants. Sample preparation, such as extraction, concentration and isolation of analytes, greatly influences the reliable and accurate analysis of food. Solid-phase microextraction (SPME) is a new sample preparation technique using a fused-silica fiber that is coated on the outside with an appropriate stationary phase. Analyte in the sample is directly extracted to the fiber coating. The SPME technique can be used routinely in combination with gas chromatography (GC), GC–mass spectrometry (GC–MS), high-performance liquid chromatography (HPLC) or LC–MS. Furthermore, another SPME technique known as in-tube SPME has also been developed for combination with LC or LC–MS using an open tubular fused-silica capillary column as an SPME device instead of SPME fiber. These methods using SPME techniques save preparation time, solvent purchase and disposal costs, and can improve the detection limits. This review summarizes the SPME techniques for coupling with various analytical instruments and the applications of these techniques to food analysis.     

Human exhaled air analytics: biomarkers of diseases

Over the last few years, breath analysis for the routine monitoring of metabolic disorders has attracted a considerable amount of scientific interest, especially since breath sampling is a non-invasive technique, totally painless and agreeable to patients. The investigation of human breath samples with various analytical methods has shown a correlation between the concentration patterns of volatile organic compounds (VOCs) and the occurrence of certain diseases. It has been demonstrated that modern analytical instruments allow the determination of many compounds found in human breath both in normal and anomalous concentrations. The composition of exhaled breath in patients with, for example, lung cancer, inflammatory lung disease, hepatic or renal dysfunction and diabetes contains valuable information. Furthermore, the detection and quantification of oxidative stress, and its monitoring during surgery based on composition of exhaled breath, have made considerable progress. This paper gives an overview of the analytical techniques used for sample collection, preconcentration and analysis of human breath composition. The diagnostic potential of different disease-marking substances in human breath for a selection of diseases and the clinical applications of breath analysis are discussed.     

Flow analysis based on a pulsed flow of solution: theory, instrumentation and applications

The increased demands placed on solution propulsion by programmed flow systems, such as sequential injection analysis, lab-on-value technology, bead injection and multi-commutation, has highlighted the inability of many conventional pumps to generate a smooth, consistent flow. A number of researchers have examined ways to overcome the inadvertent, uncontrolled pulsation caused by the mechanical aciton of peristaltic pumps. In contrast, we have developed instruments that exploit the characteristics of a reproducible pulsed flow of solution. In this paper, we discuss our instrumental approaches and some applications that have benefited from the use of a reproducible pulsed flow rather than the traditional linear flow approach. To place our approach in the context of the continuously developing field of flow analysis, an overview of other programmed flow systems is also presented.     

Diazoacetonitrile (N2CHCN): A Long Forgotten but Valuable Reagent for Organic Synthesis

Diazoacetonitrile (N₂CHCN) is a small reactive diazoalkane. It has been synthesized for the first time already in 1898 by Theodor Curtius, however, did not gain much recognition in organic synthesis until recently. Only in 2015, after introduction of in situ and flow protocols for the safe generation of diazoacetonitrile, it started gaining popularity. In this minireview, the synthetic properties and applications of this valuable reagent are discussed.     

New aspects of thermal analysis,Part I. Resolution of DSC and means for its optimization

The definitions of the temperature resolution, the so-called resolution of DSC instruments given in literature are discussed. A new definition of the resolution for DSC instruments is presented and outlined. The main characteristic introduced in this new definition is a minimum between two caloric events as a prerequisite of an existing resolution. Possible candidates of test substances have been evaluated. The oligomer n-hexatriacontane is revealing an interesting phenomenon, namely a lambda transition which is in the peak temperature only 2 K lower than the melting temperature of 76°C. The substance was selected as an ideal test substance for the quantification of the resolution of DSC instruments. The lambda transition is a second order process which may reach under certain conditions the saturation of the occurring molecular dislocation within 0.2 K, and after saturation the heat flow rate drops sharply down. Investigations concerning the main characteristics of n-hexatriacontane in respect to the temperatures of transition (lambda transition and melting), to the involved enthalpies, and to the resolution factors were performed as functions of the sample mass and the heating rate. The importance of relevant evaluation procedures increasing the resolution factors of DSC curves are discussed and these procedures are integrated into the testing of the resolution. The necessity for widening the experimental scope from instruments to evaluation procedures is forced by the existence of instruments with built-in signal treatments based on electronic devices and software procedures. A comparison with literature data is outlined for all of the mentioned characteristic values of n-hexatriacontane. This revised version was published online in August 2006 with corrections to the Cover Date.     

Operation of an academic open access mass spectrometry facility with particular reference to the analysis of synthetic compounds

Open access mass spectrometry now provides the opportunity to move this spectroscopic method to the beginning of the analytical chain, a place formerly the exclusive province of NMR and TLC. To date this transition has been occurring in industrial settings but there has been less change in the academic environment. This paper provides one blueprint for setting up such a facility, primarily in support of organic synthesis but also for the use of biological scientists. The open access format used at UCI utilizes four instruments: an ESI-TOFMS system used in the flow injection mode, two GC/MS systems (one in EI and one in CI) and a MALDI-TOFMS system. The first three instruments have autosamplers and open access software whereas the MALDI system has a fully automated plate handling interface. This level of automation allows access to the instruments by a user community of more than 100 users, day or night. The decisions made in setting up these instruments were based on a 'keep it simple' philosophy, given the fact that the primary type of data of interest is the molecular mass of the analyte and that data are required for a very wide range of structures.     

On-chip fluorescence-activated particle counting and sorting system

A fluorescence-activated particle counting and sorting system is developed for lab-on-a-chip applications. This system integrates the microfluidic chip, fluorescence excitation and detection, electronic power switch control, and optical visualization. The automatic sorting function is achieved by electrokinetic flow switching, which is triggered by a pre-set fluorescent threshold. A direct current electric pulse is generated to dispense the fluorescent particles to the collection reservoir. A user-friendly software interface is developed for automatic real-time counting, sorting and visualization. The design of the disposable microfluidic chip is simple and easy for integration. This system represents a promising prototype for development of affordable and portable flow cytometric instruments.     

Nanostructured substrates for portable and miniature SPR biosensors

Surface plasmon resonance (SPR) biosensing has matured into a valuable analytical technique for measurements related to biomolecules, environmental contaminants, and the food industry. Contemporary SPR instruments are mainly suitable for laboratory-based measurements. However, several point-of-measurement applications would benefit from simple, small, portable and inexpensive sensors to assess the health condition of a patient, potential environmental contamination, or food safety issues. This Trend article explores nanostructured substrates for improving the sensitivity of classical SPR instruments and nanoparticle (NP)-based colorimetric substrates that may provide a solution to the development of point-of-measurement SPR techniques. Novel nanomaterials and methodology capable of enhancing the sensitivity of classical SPR sensors are destined to improve the limits of detection of miniature SPR instruments to the level required for most applications. In a different approach, paper or substrate-based SPR assays based on NPs, are a highly promising topic of research that may facilitate the widespread use of a novel class of miniature and portable SPR instruments.     

Modern MALDI time‐of‐flight mass spectrometry

This paper focuses on development of time‐of‐flight (TOF) mass spectrometry in response to the invention of matrix‐assisted laser desorption/ionization (MALDI). Before this breakthrough ionization technique for nonvolatile molecules, TOF was generally considered as a useful tool for exotic studies of ion properties but was not widely applied to analytical problems. Improved TOF instruments and software that allow the full potential power of MALDI to be applied to difficult biological applications are described. A theoretical approach to the design and optimization of MALDI‐TOF instruments for particular applications is presented. Experimental data are provided that are in excellent agreement with theoretical predictions of resolving power and mass accuracy. Data on sensitivity and dynamic range using kilohertz laser rates are also summarized. These results indicate that combinations of high‐performance MALDI‐TOF and TOF‐TOF with off‐line high‐capacity separations may ultimately provide throughput and dynamic range several orders of magnitude greater than those currently available with electrospray LC‐MS and MS‐MS. Copyright © 2009 John Wiley & Sons, Ltd.     

Preliminary Study on the Use of Water-in-Oil Microemulsion Eluents in HPLC

This paper describes the use of water-in-oil (W/O) microemulsion eluents to achieve unique normal phase HPLC separations. The effects of varying the oil type, co-surfactant, surfactant, use of mixed surfactant and water concentration upon the chromatographic performance was assessed. Other parameters such as temperature and flow rate were also investigated. An optimised set of W/O microemulsion HPLC (MELC) operating conditions was then applied to the separation of a range of acids, bases and neutral compounds. The more water soluble compounds were more highly retained. W/O MELC was found to be especially suitable for determination of water insoluble compounds. The drug content in bumetanide tablets was determined by W/O MELC with good linearity and accuracy. The solubilising ability of the W/O microemulsion reduced sample preparation (precipitation and extraction) requirements compared to conventional HPLC. The results obtained compared well with those obtained by a validated reverse phase HPLC method. It is recommended that W/O MELC should be considered for routine applications, especially for the analysis of water insoluble compounds in complex sample matrices. Further research is recommended to more definitely assess the operating parameters of W/O MELC and to determine other applications.     

A microwave plasma cavity assembly for atomic emission spectrometry

Although inductively coupled plasmas (ICPs) are widely used for multielement analysis microwave induced plasma (MIP) offers a great potential for a variety of applications. Modifications to incorporate MIP into commercial ICP direct reading spectrometer systems have been developed. A direct reading échelle spectrometer is described which opens new possibilities for the successful construction of commercial MIP-AES systems with the potential to run all of the typical methods worked out for earlier ICP-AES applications. Use of flow injection techniques and automation to couple with in situ concentration will likely offer a further improvement in the analytical performance of this system. Due to the capabilities demonstrated by this spectrometer it appears that hybrid instruments will be increasingly important for future developments in optical spectrometry. This is particularly true for very demanding areas such as atomic emission spectrometry. The system could be readily commercialized.     

Biological technologies for the treatment of atmospheric pollutants

Most industrial activities emit atmospheric pollutants nowadays. Many of these activities are performed in stationary hotspots such as chemical industry facilities, wastewater and solid waste treatment plants. Other important stationary sources of gas pollutants include facilities for mining, intensive livestock farming and rendering. Volatile organic compounds (VOCs), odours and greenhouse gases are released from the above-mentioned sources, leading to issues related to global warming, health disorders and complaints to public administrations due to odour annoyance. When the release of atmospheric pollutants cannot be prevented, the sort of pollutants, their concentration and the flow rate of the waste gas emission must be characterised in order to select the most cost-effective treatment technology. Over the last decades, the use of biological technologies for the treatment of atmospheric pollutants has gradually increased due to their proven robustness, high cost-effectiveness and low environmental impact. The fundamentals of the most commonly implemented biological technologies in industrial applications (biofiltration, biotrickling filtration, bioscrubbing and activated sludge diffusion) are described in this work. The latest findings in the field of biological technologies for air pollution control are also presented and discussed.     

Comparative study between a commercial and a homemade capillary electrophoresis instrument for the simultaneous determination of aminated compounds by induced fluorescence detection

The performance of two capillary electrophoresis (CE) instruments, one commercial and one homemade device, were compared for the determination of derivatised aminated compounds with fluorescein isothiocyanate (FITC). The commercial CE system first uses an argon ion laser as excitation source; the homemade CE device uses an inexpensive blue-light-emitting diode (LED) as the light source and a charge-coupled device (CCD) as the detection system. After fine optimisation of several separation parameters in both devices, a co-electroosmotic flow CE methodology was achieved in coated capillary tubing with 0.001% hexadimetrine bromide (HDB), and 50 mmol L⁻¹ sodium borate at pH 9.3 with 20% 2-propanol for the determination of several amines and aminoacids. Analytical performances, applicability in beer samples and other aspects such as cost or potential for miniaturization have been compared for both devices.     

Standardization of near infrared spectra measured on multi-instrument

Calibration model transfer is essential for practical applications of near infrared (NIR) spectroscopy because the measurements of the spectra may be performed on different instruments and the difference between the instruments must be corrected. An approach for calibration transfer based on alternating trilinear decomposition (ATLD) algorithm is proposed in this work. From the three-way spectral matrix measured on different instruments, the relative intensity of concentration, spectrum and instrument is obtained using trilinear decomposition. Because the relative intensity of instrument is a reflection of the spectral difference between instruments, the spectra measured on different instruments can be standardized by a correction of the coefficients in the relative intensity. Two NIR datasets of corn and tobacco leaf samples measured with three instruments are used to test the performance of the method. The results show that, for both the datasets, the spectra measured on one instrument can be correctly predicted using the partial least squares (PLS) models built with the spectra measured on the other instruments.     

A microwave plasma cavity assembly for atomic emission spectrometry

Although inductively coupled plasmas (ICPs) are widely used for multielement analysis microwave induced plasma (MIP) offers a great potential for a variety of applications. Modifications to incorporate MIP into commercial ICP direct reading spectrometer systems have been developed. A direct reading échelle spectrometer is described which opens new possibilities for the successful construction of commercial MIP-AES systems with the potential to run all of the typical methods worked out for earlier ICP-AES applications. Use of flow injection techniques and automation to couple with in situ concentration will likely offer a further improvement in the analytical performance of this system. Due to the capabilities demonstrated by this spectrometer it appears that hybrid instruments will be increasingly important for future developments in optical spectrometry. This is particularly true for very demanding areas such as atomic emission spectrometry. The system could be readily commercialized.     

Enthalpies of dilution of electrolyte solutions by flow microcalorimetry

The enthalpies of dilution of NaCl, Me₄NBr, andn-Bu₄NBr were measured in water at 25°C with a new flow microcalorimeter. The data were analyzed with a polynomial equation, and the derived relative apparent molal enthalpies _L are in good agreement with literature values. Provided care is taken that mixing is complete, flow calorimeters are as reliable and much less time-consuming than cell-type instruments for enthalpies of dilution measurements.     

Synthesis of analogues of ochratoxin A

Four analogues of ochratoxin A (OTA) differing for the aminoacidic moiety were synthesised using ochratoxin α (OTα) as the starting material. The condensation reaction between protected amino acids and OTα, carried out in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC???HCl) and N-hydroxybenzotriazole (HOBt) as coupling agents, followed by deprotection and PTLC purification afforded OTA alanine, leucine, serine and tryptophane analogues in satisfactory yields (33-47%, based on OTα).