Carbon nanotubes (CNTs) promise to advance a number of real-world technologies. Of these applications, they are particularly attractive for uses in chemical sensors for environmental and health monitoring. However, chemical sensors based on CNTs are often lacking in selectivity, and the elucidation of their sensing mechanisms remains challenging. This review is a comprehensive description of the parameters that give rise to the sensing capabilities of CNT-based sensors and the application of CNT-based devices in chemical sensing. This review begins with the discussion of the sensing mechanisms in CNT-based devices, the chemical methods of CNT functionalization, architectures of sensors, performance parameters, and theoretical models used to describe CNT sensors. It then discusses the expansive applications of CNT-based sensors to multiple areas including environmental monitoring, food and agriculture applications, biological sensors, and national security. The discussion of each analyte focuses on the strategies used to impart selectivity and the molecular interactions between the selector and the analyte. Finally, the review concludes with a brief outlook over future developments in the field of chemical sensors and their prospects for commercialization.

Carbon Nanotube Chemical Sensors

The terms recovery and apparent recovery are recommended to avoid confusion caused by the use of the term recovery to cover two distinct situations. These situations deal with: (a) the yield of a preconcentration or extraction stage of an analytical process (where recovery is recommended) and (b) the quantity observed value/reference value, obtained using an analytical procedure that involves a calibration graph (where apparent recovery is recommended).

Use of the term "recovery" and "apparent recovery" in analytical procedures (IUPAC Recommendations 2002)

Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) is an extraction and clean-up technique originally developed for recovering pesticide residues from fruits and vegetables. Since its introduction, and until December 2013, about 700 papers have been published using the QuEChERS technique, according to a literature overview carried out using SciFinder, Elsevier SciVerse, and Google search engines. Most of these papers were dedicated to pesticide multiresidue analysis in food matrices, and this topic has been thoroughly reviewed over recent years. The QuEChERS approach is now rapidly developing beyond its original field of application to analytes other than pesticides, and matrices other than food, such as biological fluids and non-edible plants, including Chinese medicinal plants. Recently, the QuEChERS concept has spread to environmental applications by analyzing not only pesticides but also other compounds of environmental concern in soil, sediments, and water. To the best of our knowledge, QuEChERS environmental applications have not been reviewed so far; therefore, in this contribution, after a general discussion on the evolution and changes of the original QuEChERS method, a critical survey of the literature regarding environmental applications of conventional and modified QuEChERS methodology is provided. The overall recoveries obtained with QuEChERS and other extraction approaches (e.g., accelerated solvent extraction, ultrasonic solvent extraction, liquid/solid extraction, and soxhlet extraction) were compared, providing evidence for QuEChERS higher recoveries for various classes of compounds, such as biopesticides, chloroalkanes, phenols, and perfluoroalkyl substances. The role of physicochemical properties of soil (i.e., clay and organic carbon content, as well as cation exchange capacity) and target analytes (i.e., log KOW, water solubility, and vapor pressure) were also evaluated in order to interpret recovery and matrix effect data.

QuEChERS sample preparation for the determination of pesticides and other organic residues in environmental matrices: a critical review

Practical guidelines for reporting results in single- and multi-component analytical calibration: A tutorial

On the calibration of sensor arrays for pattern recognition using the minimal number of experiments

Guidelines for calibration in analytical chemistry

Use of the terms "recovery" and "apparent recovery" in analytical procedures

The term "dimensionality" has been used by the analytical chemistry community with several meanings. On different occasions, analysts speak about "two-dimensional" analytical methods, for example, 2D nuclear magnetic resonance spectroscopy, 2D thin-layer chromatography, "two-dimensional" or "three-dimensional" analytical information [1], "two-dimensional" or "three-dimensional" images in surface analytical chemistry, and of "m-dimensional" analytical data [2] obtained, for example, as a result of multicomponent analyses. These examples show that the use of the term "dimensionality" is at times contradictory. This confused position does not promote the unequivocal application of the term "dimensionality" in analytical chemistry. The aim of this document is to provide a concept for the use of the term "dimensionality" as it is related to analytical information.

Friedrich Schiller

Papers

Guidelines for calibration in analytical chemistry

Use of the terms "recovery" and "apparent recovery" in analytical procedures

Concepts and applications of the term "dimensionality" in analytical chemistry