Industrial applications of activable tracers

The use of activable tracers for industrial applications proved to be a favorable alternative to the use of radiotracers in a number of cases. Difficulties belonging to the procedure to obtain the permit for handling radioactive materials by public health authorities are avoided: delay in time and details of the processes involved open to the public. Economic advantages of activable tracers are low cost of activable tracers and absence of labor costs for radiological control. Three examples are given: a mixing process, material losses by a stack and wear measurements.     

Determination of polar organic compounds in atmospheric aerosols by gas chromatography with ion trap tandem mass spectrometry

A gas chromatography with ion trap mass spectrometry method has been developed and validated for the analysis of 27 polar organic compounds in atmospheric aerosols. The target analytes were low‐molecular‐weight carboxylic acids and methoxyphenols, as relevant markers of source emissions and photochemical processes of organic aerosols. The operative parameters were optimized in order to achieve the best sensitivity and selectivity for the analysis. In comparison with the previous gas chromatography with mass spectrometry procedure based on single ion monitoring detection, the tandem mass spectrometry technique increased the analytical sensitivity by reducing detection limits for standard solutions from 1–2.6 to 0.1–0.4 ng/μL ranges (concentrations in the injected solution). In addition, it enhanced selectivity by reducing matrix interferences and chemical noise in the chromatogram. The applicability of the developed method in air quality monitoring campaigns was effectively checked by analyzing environmental samples collected in the Po Valley (Northern Italy) in different seasons. The obtained results indicate that the ion trap mass spectrometer may be an ideal alternative to high‐resolution mass spectrometers for the user‐friendly and cost‐effective determination of a wide range of molecular tracers in airborne particulate matter.     

Determination of technetium-99 in environmental material with rhenium as a yield monitor

The ability of the close analogue element rhenium to act as a satisfactory non-isotopic yield monitor for the analysis of⁹⁹Tc in environmental materials is explored and its performance critically evaluated in a new radioanalytical method designed specifically for use with rhenium as both carrier and yield monitor. The advantages and limitations of rhenium for this purpose are compared with isotopic tracers such as^99mTc,^97mTc and^95mTc. When employed in a well designed analytical scheme, rhenium, which has received only limited consideration in the past, is shown to be a cheap, reliable alternative to isotopic tracers.     

The applicability of radiotracers for the investigation of the distillation of hydrocarbons

The use of radioactive tracers provide valuable methods for the investigation of distillation processes and have been applied to determine the characteristics of material streams, the dynamics of flowing phases and the compositions in various parts of the distillation equipment. A method is proposed for testing individual radiotracers employed for the investigation of the distillation of hydrocarbons. The method consists in laboratory-scale distillation of a tracer together with a multicomponent hydrocarbon mixture, namely a gasoline fraction. The purification efficiency, distillation characteristics, and effective radiochemical purity of several tracers (reactor activated bromobenzene and synthesized C₃H₇ ⁸²Br, C₄H₉ ⁸²Br, C₅H₁₁ ⁸²Br) have been investigated. The distillation characteristics of bromohydrocarbons labelled with⁸²Br and selected hydrocarbons tagged with¹⁴C (benzene and cumene) have been compared. The radiotracers investigated were employed for the determination of the hydrodynamic parameters of hydrocarbon distillation in laboratory packed columns and a commercial distillation tower.     

An Integrated Approach toward NanoBRET Tracers for Analysis of GPCR Ligand Engagement

Gaining insight into the pharmacology of ligand engagement with G-protein coupled receptors (GPCRs) under biologically relevant conditions is vital to both drug discovery and basic research. NanoLuc-based bioluminescence resonance energy transfer (NanoBRET) monitoring competitive binding between fluorescent tracers and unmodified test compounds has emerged as a robust and sensitive method to quantify ligand engagement with specific GPCRs genetically fused to NanoLuc luciferase or the luminogenic HiBiT peptide. However, development of fluorescent tracers is often challenging and remains the principal bottleneck for this approach. One way to alleviate the burden of developing a specific tracer for each receptor is using promiscuous tracers, which is made possible by the intrinsic specificity of BRET. Here, we devised an integrated tracer discovery workflow that couples machine learning-guided in silico screening for scaffolds displaying promiscuous binding to GPCRs with a blend of synthetic strategies to rapidly generate multiple tracer candidates. Subsequently, these candidates were evaluated for binding in a NanoBRET ligand-engagement screen across a library of HiBiT-tagged GPCRs. Employing this workflow, we generated several promiscuous fluorescent tracers that can effectively engage multiple GPCRs, demonstrating the efficiency of this approach. We believe that this workflow has the potential to accelerate discovery of NanoBRET fluorescent tracers for GPCRs and other target classes.     

Separation of no-carrier-added <Superscript>107,109</Superscript>Cd from proton induced silver target: classical chemistry still relevant

The classical chemistry like precipitation technique is relevant even in modern days trans-disciplinary research from the view point of green chemistry. A definite demand of no-carrier-added (nca) cadmium tracers, namely, ^107,109Cd, has been realized for diverse applications. Development of efficient separation technique is therefore important to address the purity of the tracers for various applications. No-carrier-added ^107,109Cd radionuclides were produced by bombarding natural silver target matrix with 13 MeV protons, which gave ~15 MBq/μA h yield for nca ¹⁰⁷Cd. The nca cadmium radionuclides were separated from the natural silver target matrix by precipitating Ag as AgCl. The developed method is an example wherein green chemistry is used in trans-disciplinary research. The method is also simple, fast, cost effective and environmentally benign.     

Ultrasensitive electrical biosensing of proteins and DNA: carbon-nanotube derived amplification of the recognition and transduction events

A new strategy for dramatically amplifying enzyme-linked electrical detection of proteins and DNA using carbon nanotubes (CNTs) for carrying numerous enzyme tracers and accumulating the enzymatically liberated product on CNT-modified transducer is described. Such a CNT-derived double-step amplification pathway (of both the recognition and transduction events) allows the detection of DNA and proteins down to 1.3 and 160 zmol, respectively, in 25-50 muL samples and indicates great promise for PCR-free DNA analysis. The new protocol is illustrated for monitoring sandwich hybridization and antibody-antigen interactions in connection with alkaline-phosphatase tracers. The DNA-linking of CNTs and particles holds promise also for assembling hybrid nanostructures relevant to molecular electronic devices.     

Computing reliable energetics for conjugate addition reactions

The performance of various density functionals along with second-order perturbation treatments has been tested for a set of conjugate addition reactions relevant to stereoselective organocatalysis. It is shown that B3LYP predictions seriously underestimate the reaction energies, whereas two newly designed functionals (M05-2X and M06-2X) and the SCS-MP2 method provide very accurate data. These new methods represent promising alternative approaches in future mechanistic studies.     

Determination of the herbicide metribuzin and its major conversion products in soil by micellar electrokinetic chromatography

In this paper, a multiresidue method for the analysis in soils of metribuzin (M) and its major conversion products, deaminometribuzin (DA), diketometribuzin (DK) and deaminodiketometribuzin (DADK) is developed. Considering the neutral and charged nature of the molecules, micellar electrokinetic chromatography (MEKC) is a very efficient method for the separation of these compounds, providing high efficiency and short analysis times. Different electrophoretic parameters were studied to optimize the separation, such as the buffer pH and concentration, sodium dodecyl sulphate (SDS) concentration, injection conditions and applied voltage. Excellent separation of the studied compounds was achieved within about 7 min. Soil samples were previously extracted using methanol in an ultrasonic bath and then a SPE procedure was applied to pre-concentrate the analytes by passage through a LiChrolut EN sorbent column. Detection limits at the low microgkg(-1) level were obtained. The proposed method has been satisfactorily applied in soil samples showing recoveries ranging from 86.7% to 104.2% and represents a valuable alternative to high-performance liquid chromatography (HPLC).     

The measurement of molecular diversity: A three-dimensional approach

Summary This paper describes a method for selecting a small, highly diverse subset from a large pool of molecules. The method has been employed in the design of combinatorial synthetic libraries for use in high-throughput screening for pharmaceutical lead generation. It computes diversity in terms of the main factors relevant to ligand-protein binding, namely the three-dimensional arrangement of steric bulk and of polar functionalities and molecular entropy. The method was used to select a set of 20 carboxylates suitable for use as side-chain precursors in a polyamine-based library. The method depends on estimates of various physical-chemical parameters involved in ligand-protein binding; experiments examined the sensitivity of the method to these parameters. This paper compares the diversity of randomly and rationally selected side-chain sets; the results suggest that careful design of synthetic combinatorial libraries may increase their effectiveness several-fold.     

Applied gas chromatography coupled to isotope ratio mass spectrometry.

Compound-specific isotope analysis (CSIA) by isotope ratio mass spectrometry (IRMS) following on-line combustion (C) of compounds separated by gas chromatography (GC) is a relatively young analytical method. Due to its ability to measure isotope distribution at natural abundance level with great accuracy and high precision, GC-C-IRMS has increasingly become the method of choice in authenticity control of foodstuffs and determination of origin in archaeology, geochemistry, and environmental chemistry. In combination with stable isotope labelled compounds, GC-C-IRMS is also used more and more in biochemical and biomedical application as it offers a reliable and risk-free alternative to the use of radioactive tracers. The literature on these topics is reviewed from the advent of commercial GC-C-IRMS systems in 1990 up to the beginning of 1998. Demands on sample preparation and quality of GC separation for GC-C-IRMS are discussed also.     

Nanoparticle-based electrochemical DNA detection

Nanoscale architectures of DNA-linked particle networks are attractive for electrical detection of DNA hybridization. This article reviews a variety of new nanoparticle/polynucleotide assemblies for advanced electrical detection of DNA sequences. Recent activity has led to innovative and powerful nanoparticle-based electrochemical DNA hybridization assays based on a variety of detection schemes. Such protocols rely on the use of colloidal gold tags, semiconductor quantum dot tracers, polymeric carrier (amplification) beads, or magnetic (separation) beads. Particularly useful have been protocols based on capturing of metal nanoparticle tracers followed by dissolution and anodic-stripping voltammetric measurement of the metal tag. Remarkable sensitivity is achieved by coupling particle-based amplification units and various amplification processes. The use of nanoparticle tracers for designing multi-target electrochemical coding protocols will also be documented.     

Simultaneous determination of trace amounts of sulphur hexafluoride and cyclic perfluorocarbons in reservoir samples by gas chromatography

Summary Both sulphur hexafluoride and a group of compounds among the perfluorinated cyclic hydrocarbons: perfluorodimethyl cyclobutane, perfluoromethyl cyclopentane, perfluoromethyl cyclohexane and the 1,2- and 1,3-isomers of perfluordimethyl cyclohexane are well known to be good gas tracers, in various applications. Unfortunately different methods have been used for the analysis of SF₆ and the perfluorocarbons. Therefore, in many cases, the analytical costs may have hindered the use of both SF₆ and the perfluorocarbons in the same tracer experiments. The analytical method described in this paper enables the determination of both types of gas tracer in one single run. The new method has already replaced two former methods and was used to run the gas tracer analysis routinely, proving the reliability of the method.     

Correction of the data generated by mass spectrometry analyses of biological tissues: application to food authentication

The objective of the work was to assess the relevance for the authentication of food of a novel chemometric method developed to correct mass spectrometry (MS) data from instrumental drifts, namely, the comprehensive combinatory standard correction (CCSC). Applied to gas chromatography (GC)-MS data, the method consists in analyzing a liquid sample with a mixture of n internal standards and in using the best combination of standards to correct the MS signal provided by each compound. The paper focuses on the authentication of the type of feeding in farm animals based on the composition in volatile constituents of their adipose tissues. The first step of the work enabled on one hand to ensure the feasibility of the conversion of the adipose tissue sample into a liquid phase required for the use of the CCSC method and on the other hand, to determine the key parameters of the extraction of the volatile fraction from this liquid phase by dynamic headspace. The second step showed the relevance of the CCSC pre-processing of the MS fingerprints generated by dynamic headspace-MS analysis of lamb tissues, for the discrimination of animals fed exclusively with pasture (n=8) or concentrate (n=8). When compared with filtering of raw data, internal normalization and correction by a single standard, the CCSC method increased by 17.1-, 3.3- and 1.3-fold, respectively, the number of mass fragments which discriminated the type of feeding. The final step confirmed the advantage of the CCSC pre-processing of dynamic headspace-gas chromatography-MS data for revealing molecular tracers of the type of feeding those number (n=72) was greater when compared to the number of tracers obtained with raw data (n=42), internal normalization (n=63) and correction by a single standard (n=57). The relevance of the information gained by using the CCSC method is discussed.     

Chemiluminescence immunoassays

Over the last 25 years, radioimmunoassays have developed into highly sophisticated analytical systems capable of offering exquisite sensitivity and specificity. The expansion of the scope of their application from human health care to other areas such as food and water analysis is in part due to the move away from the use of radioactive tracers. Chemiluminescent molecules perhaps provide the most logical non-radioactive alternative.     

Evaluation of lanthanum and praseodymium chelates of DTPA,CDTA, EDTA,and NTA as groundwater tracers

The chemical stability of various chelates of La and Pr, as they were carried by water through a large soil column, were evaluated. The purpose of this work was to identify potential radioactive or neutron activatable groundwater tracers. This work established that of the chelates tested, Pr-DTPA followed by La-DTPA were the most stable and thus suitable for testing as groundwater tracers.     

Ion-exchange separation of uranium,thorium and plutonium isotopes from environmental samples

Radioisotopes of uranium, thorium and plutonium in water, soil and fertilizer samples, have been chemically separated and determined by alpha-spectrometry method. Radiochemical procedure involving ion-exchange, enabled to determine these isotopes in very low concentrations (under 50 Bq/g).²³²U,²²⁹Th and²³⁸Pu were used as a tracers for radiochemical yield recoveries (up to 90%). Thin layer sources have been obtained by electrodeposition.     

Optimization of a flow injection analysis system for tartaric acid determination in wines

The objective of this work is the development and optimization of a method for tartaric acid analysis in wines that does not require any sample pre-treatment and with adequate accuracy. A flow injection analysis manifold with three channels, using a dialysis unit to eliminate sample matrix interferences and to accomplish on-line dilution, is proposed for the spectrophotometrical determination of tartaric acid in wines making use of its reaction with vanadate. The proposed method is fast, accurate, simple, economic and does not require any sample pre-treatment. Preliminary studies using factorial designs were performed to determine which operational parameters should be included in the optimization stage. The optimization was performed using a modified simplex algorithm with a response function that included sensitivity, deviation from linearity at low concentrations and residence time, used as an inverse measure of sampling rate. The most relevant analytical parameters of the method are presented, including a comparison between the results provided by the proposed method and by an alternative procedure in the analysis of a set of wine samples from Portugal, with tartaric acid values in the range 0.5–4 g l⁻¹.     

Cancer detection using nanoparticle-based sensors

This tutorial review surveys the latest achievements in the use of nanoparticles to detect cancer biomarkers and cancer cells with a focus on optical and electrochemical techniques. Nanoparticle based cancer diagnostics are becoming an increasingly relevant alternative to traditional techniques. Although some drawbacks exist in relation to the obtained sensitivity the use of nanoparticle-based sensors in biomarker detection or cancer cell detection offers some advantages in comparison to conventional methods. The developed techniques can be interesting and relevant for their use in point-of-care of cancer diagnostics. The methods can be of low cost and in addition easy to be incorporated into user-friendly sensing platforms.