Analytical derivatizations in environmental analysis

Recent advances in gas chromatography injection port derivatization in analytical method development

Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) has been established as a good and relatively sensitive method for qualitative analysis of powders and rough surfaces. The technique is non-destructive and high quality spectra can be easily obtained without extensive sample preparation. The capacity of the method for qualitative analysis of functional groups has been demonstrated in numerous fields. The potential of DRIFTS for quantitative analysis was recognized quite early as well. However, many theoretical and practical problems do appear when the method is applied for this purpose, requiring very accurate sampling procedure. The effect on reflectance spectra of several parameters influencing sampling has been studied. Conventionally, a simplified relation derived from the phenomenological continuum theory of Kubelka-Munk is used in order to relate the concentration of a chromophore, dispersed in a sample, to the intensity of the diffusely reflected radiation. In practice however, this equation can be used only for ideal systems diluted in a non-absorbing scattering matrix and in a limited concentration range. Preparation of such idealized samples in a reproducible way is difficult. Quantitative analysis of opaque non-diluted systems such as those found in the real world is of high interest. In many fields, like for example in thin layer chromatography, stationary phase studies, environmental pollutant analysis, and industrial quality control or heterogeneous catalysis, it is desirable to quantitatively characterize samples as close as possible to their original state. In our own effort to do quantitative spectroscopy of powders, we have investigated the case of non-diluted samples. Model systems constituted of two types of silica powders (Cab-O-Sil and LiChrosorb) of very different morphology were prepared. The surface hydroxyl groups of SiO2 were exposed to a silylation reaction with an aminosilane containing a suitable chromophore. Known superficial concentrations of molecules carrying a cyano functional group were anchored by this way on the powder surface. A quantitative model of diffuse reflectance, derived from the general hyperbolic solutions of the Kubelka-Munk equations has been developed, taking into account different parameters such as the absorption of the silica substrate, finite thickness of the sample, specular reflection, as well as diffusion and absorption coefficients profiles within the depth of the scattering layer. Application of this model gives a quite good description of measured diffuse reflectance, in cases where the simple Kubelka-Munk relation fails. Use of a Mar quardt type non-linear least square adjustment method to the experimental data allows moreover the determination of other parameters of interest. A new FTIR analytical technique, based on a PVDF photo-pyroelectric film detector, has also been developed, which has enabled for the first time sequential measurement of diffuse reflectance and diffuse transmittance of the same sample without any change in the optical geometry and sample manipulation. Another multilayer discontinuum theory, more suited for particles of diameter larger than the radiation wavelength, has been developed and successfully applied to diffuse reflectance and transmittance measurements of sodium carbonate powders.

Background: Natural product databases are important in drug discovery and other research areas. Their structural contents and functional group analysis are relevant to increase their knowledge in terms of chemical diversity and chemical space coverage. BIOFACQUIM is an emerging database of natural products characterized and isolated in Mexico. Herein, we discuss the results of a first systematic functional group analysis and global diversity of an updated version of BIOFACQUIM. Methods: BIOFACQUIM was augmented through a literature search and data curation. A structural content analysis of the dataset was done. This involved a functional group analysis with a novel algorithm to identify automatically all functional groups in a molecule and an assessment of the global diversity using consensus diversity plots. To this end, BIOFACQUIM was compared to two major and large databases: ChEMBL 25, and a herein assembled collection of natural products with 169,839 unique compounds. Results: The structural content analysis showed that 16.1% of compounds, 11.3% of scaffolds, and 6.3% of functional groups present in the current version of BIOFACQUIM have not been reported in the other large reference datasets. It also gave a diversity increase in terms of scaffolds and molecular fingerprints regarding the previous version of the dataset, as well as a higher similarity to the assembled collection of natural products than to ChEMBL 25, in terms of diversity and frequent functional groups. Conclusions: A total of 148 natural products were added to BIOFACQUIM, which meant a diversity increase in terms of scaffolds and fingerprints. Regardless of its relatively small size, there are a significant number of compounds, scaffolds, and functional groups that are not present in the reference datasets, showing that curated databases of natural products, such as BIOFACQUIM, can serve as a starting point to increase the biologically relevant chemical space.

Evaluation of an automatic sample preparer in the development and validation of an analytical method for vial wall sorptive extraction

20 - Solid-phase analytical derivatizations

One of the target goals of present environmental analysis is shortening of the time required for the overall analysis due to the fact that a large number of samples require be analysed everyday. Because sample preparation is the most time consuming step of the analytical process, the primary goal should be to expedite this analytical step. In this sense, high temperature-high pressure of the extractant or solvent, and energy sources such as microwaves or ultrasounds can be used to accelerate sample preparation. Due to the enormous variability of samples in the environmental field (and dependence on the type of analyte, matrix, subsequent individual separation technique, if required, and detection) selection of the most suitable auxiliary energy for this step is not usually clear. In the present review, a description of the choices available for expediting sample preparation and their main applications in the environmental field is presented.

Chapter 13 - Green extraction approaches utilizing graphene and graphene oxide derivatives in environmental analysis

Applications of Isotope Ratio Mass Spectrometry in Sports Drug Testing Accounting for Isotope Fractionation in Analysis of Biological Samples.

Methodological studies have a strong position in soil biology; many of us are method “freaks” willing to spend the best part of our lives developing new methods, or finding reasons to discard old ones. This preference is not entirely unjustifiable; soil is a non-transparent material in more than one sense, effectively hindering a direct observation of organisms and processes. Thus, our observations are very indirect (compared to other natural sciences); there is always a “method” (or several) involved which provides us with more or less biased and fragmentary impressions of the biological reality of interest. Progress in this field will be enhanced by creative inventions of new and partly complementary approaches. For each method invented, tested, and discarded, small pieces of facts about the life of soil microbes are provided. For more than two decades, soil ecologists have analysed nucleic acids in soils for various purposes (Trevors and Van Elsas 1995; Wellington et al. 2003). The tools have developed rapidly, allowing analyses of community composition, phylogenetic and functional groups, specific species/strains and functional genes (Nannipieri et al. 2003). Most work has been done on DNA, but more recent developments include RNA, which provides information about the active part of the microbial community (Moran et al. 1993; Felske and Akkermans 1998; Duineveld et al. 2001) and gene expression (Burgmann et al. 2003). Prior to any such analyses, the soil material must be removed; the nucleic acids or themicrobial cells must be extracted from the soil particles and humic substances whichwill otherwise obscure almost any observation. The number of protocols invented is daunting, reviewed several times over the last two decades (Trevors 1992; Saano et al. 1995; Torsvik et al. 1995; Van Elsas and Smalla 1995; Stapleton et al. 1998; Roose-Amsaleg et al. 2001; Gabor et al. 2003; Robe et al. 2003). Figure 3.1 illustrates the essential steps taken indifferent protocols to

Characterization of unirradiated and irradiated LMFBR fuels by analytical chemistry methods will continue, and additional methods will be modified and mechanized for hot cell application. Macro- and microexaminations will be made on fuel and cladding using the shielded electron microprobe, emission spectrograph, radiochemistry, gamma scanner, mass spectrometers, and other analytical facilities. New capabilities will be developed in gamma scanning, analyses to assess spatial distributions of fuel and fission products, mass spectrometric measurements of burnup and fission gas constituents and other chemical analyses. Microstructural analyses of unirradiated and irradiated materials will continue using optical and electron microscopy and autoradiographic and x-ray techniques. Analytical quality assurance standards tasks are designed to assure the quality of the chemical characterizations necessary to evaluate reactor components relative to specifications. Tasks include: (1) the preparation and distribution of calibration materials and quality control samples for use in quality assurance surveillance programs, (2) the development of and the guidance in the use of quality assurance programs for sampling and analysis, (3) the development of improved methods of analysis, and (4) the preparation of continuously updated analytical method manuals. Reliable analytical methods development for the measurement of burnup, oxygen-to-metal (O/M) ratio, and various gases in irradiated fuels is described.

Elemental and Functional Group Analysis

Advanced sampling, sample preparation and combination of methods applicable in analysis of compounds in aged and deacidified papers. A minireview

This paper deals with a quantitative gas chromatographic analysis of the product evolved by the pyrolytic reaction between carboxylic acid and sulfur vapor. About 10 mg of carboxylic acid was mixed with 2–3 g sulfur and made to react at 1000–1100°C for 10min. The gaseous product was taken in a gas sampler and subjected to gas chromatography. Carbon dioxide was produced from the carboxyl group, carbon disulfide from carbon, hydrogen sulfide from hydrogen and nitrogen molecule from nitrogen. The peak area ratios of carbon disulfide and hydrogen sulfide to carbon dioxide were found in the gas chromatogram with glycine as a standard substance, and the other carboxylic acids were analyzed on the basis of the relation between the peak area ratio and the chemical composition of glycine. Aliphatic and aromatic carboxylic acids gave satisfactory resuls by this method, but not pyridine carboxylic acid. Weighing a definite amount of sample is not needed in this method. Information concerning the chemical composition as well as the functional group of a carboxylic acid can be obtained.

Background:Over the past few decades, environmental pollution has appeared to be one of the most crucial global problems. The widespread intensification of numerous hazardous pollutants in the environment need the modern researchers to develop viable, reproducible and cost-effective determination tools for the reliable environmental analysis. The beneficial, as well as perilous, biological compounds are receiving growing interest due to their variable composition which produces advantageous and toxic impacts on human and the environment. Several conventional analytical methods have been established for the pharmaceutical and environmental analysis. However, certain drawbacks limited their practices in the modern rapidly growing era of science and technology. The development of electrochemical sensors has emerged as more beneficial and promising tool as against other traditional analytical approaches, in terms of simplicity, cost-effectiveness, sensitivity, stability and reliability. Nonetheless, the over potential and low anodic/cathodic current response are both considered as bottlenecks for the determination of electroactive entities exploiting electrochemical sensors. Interestingly, these problems can be easily resolved by modifying the electrodes with a variety of conductive materials, especially nanostructures.Objective:This review covers different electrochemical methods, reported in the literature, for the environmental and pharmaceutical analysis through simple and cost-effective nanostructures-based sensors. The electrochemical techniques with different modes and the modification of electrodes with highly conductive and prolific polymeric and nanostructured materials used for the determination of different environmental and pharmaceutical samples are the main prominence of this review. Various kinds of nanomaterials, e.g. metal, metal oxide and their composites, have been synthesized for the fabrication of sensitive electrodes.Conclusion:Nanostructures played a pivotal role in the modification of electrodes, which substantially enhanced the capability and sensitivity of electrochemical sensors. The proper modification of electrodes has materialized the swift detection of electroactive compounds at very low limits and offered the feasible determination procedure without any kind of signal fluctuation and over potential. In crux, due to their enhanced surface area and excellent catalytic properties, nanomaterials recently appeared as the most promising candidates in the field of electrode modification and significantly impacted the detection protocols for various environmental pollutants, viz. pesticides, metal ions and drugs.

In this article, after reviewing the different mathematical methods used in quantification by IR, the main advantages and drawbacks and applications with or without previous sample treatment are presented. The bases of the use of quantitative IR in food analysis such as lipids (measurement of unsaturation degrees and lipids determination), carbohydrates, and proteins (secondary structures and quantitative analysis); original examples of the use of IR spectroscopy combined with enzymes; and modern applications in the clinical field are presented in detail, followed by examples of Fourier transform infrared (FTIR) analysis coupled with other analytical methods in different fields such as pharmaceuticals, petroleum, paints, and other industrial products and in the fields of health, environment, and trace compounds analysis in order to think about the limitations and perspectives of IR spectroscopy for quantitative analysis. It appears that the most significant developments in the field of quantitative analysis will probably come through the progress in chemometrics and instrumentation. More recently, approaches combining infrared spectroscopy and deep learning (DL) have shown great potential.