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Published in Luis Liz-Marzán, Colloidal Synthesis of Plasmonic Nanometals, 2020
Christoph Hanske, Marta N. Sanz-Ortiz, Luis M. Liz-Marzán
Highly sensitive and, ideally, portable sensing devices offering fast and cost-effective ex situ analysis are in high demand and their fields of application include, among others, monitoring of air and water quality by detection of hazardous chemicals, drugs and explosives tests in forensics, pregnancy tests, glucose level measurements, and tracing of biological markers in urine or blood for both early diagnosis and long-term disease monitoring. In all of these examples, the available amount of sample is usually small. For some applications, the analysis is just intended to provide a yes/no answer regarding the presence of an analyte, whereas others require quantitative determinations. A straightforward strategy in sensing applications comprises focusing on the detection of analytes that modify intrinsic, well-known features of the selected probe. Noble metal nanoparticles owe their successful implementation in a plethora of sensing applications mainly to two characteristics: sensitivity of the optical LSPR frequency to changes in the dielectric environment around the particle and plasmon coupling occurring when the particles come close to each other, which gives rise to distinct color shifts as well as strongly enhanced electromagnetic fields. As a consequence, many sensing systems have been developed for the detection of analytes that can potentially alter the size, shape, the state of aggregation of the colloidal probes, or the dielectric function of the medium.[120,121]
Fiber-Optic Sensors
Published in Banshi Dhar Gupta, Anand Mohan Shrivastav, Sruthi Prasood Usha, Optical Sensors for Biomedical Diagnostics and Environmental Monitoring, 2017
Banshi Dhar Gupta, Anand Mohan Shrivastav, Sruthi Prasood Usha
The lowest concentration of the target molecule in a solution that is detected by means of an analytical method is generally termed as the limit of detection (LOD). Although its definition and concept is simple, there is always an uncertainty in the calculation of its value depending on the technique, calibration, and the noises and errors involved in the experiment. Hence, the International Union of Pure and Applied Chemistry (IUPAC) in 1975 proposed a concept for the calculation of detection limit as, “The limit of detection, expressed as a concentration (LOD) is derived from the smallest measure that can be detected with reasonably certainly for a given analytical procedure.” This concept was again reframed by ACS Subcommittee on Environmental Analytical Chemistry in 1980 as, “Limit of detection is the lowest concentration of analyte that the detection scheme can detect reliably.” Different definitions/methods have been used for the detection limit by the researchers. These are named as the method detection limit (MDL), instrument detection limit (IDL), practical quantification limit (PQL), and limit of quantification (LOQ) (Long and Winefordner 1983).
Application of High-Performance Liquid Chromatography in Environmental Analysis
Published in Pradyot Patnaik, Handbook of Environmental Analysis, 2017
The basic components of an HPLC system are (1) a pump with a constant flow control, (2) a high-pressure injection valve, (3) a chromatographic column, (4) a detector, and (5) a strip-chart recorder or a data system for measuring peak areas and retention times. Calibration standards are prepared at various concentrations and the retention times and peak areas of the analytes are compared against the standard solutions of analytes for their identifications and quantitations.
Colloidal lead in drinking water: Formation, occurrence, and characterization
Published in Critical Reviews in Environmental Science and Technology, 2023
Javier A. Locsin, Kalli M. Hood, Evelyne Doré, Benjamin F. Trueman, Graham A. Gagnon
The most important parameters for characterizing colloids include size, shape, crystalline phase, charge, and elemental composition. Understanding the interaction between lead with organic or inorganic constituents in water requires being able to distinguish between different mechanisms such as adsorption of soluble lead or agglomeration of lead colloids. Information on the size, shape, elemental composition, and surface charge is essential for differentiating between interaction mechanisms. For environmental samples, the limit of detection should be lower than the concentration (≤ µg L−1) and cover the size range of particles in water. Since natural colloids may be present in drinking water samples, matrix sensitivity also becomes an important criterion. In addition, if the quantity and diversity of measurements needed are large, then it is important to reduce the amount of sample preparation or duration for each measurement. Therefore, the ideal analytical technique is dependent on the type of analyte, expected concentrations, sample matrix components, and the parameters to be determined. For challenging samples with complex matrixes or many analytical requirements, then a combination of complementary techniques may be used for the full characterization of colloidal suspensions.
Improving the predictive value of bioaccessibility assays and their use to provide mechanistic insights into bioavailability for toxic metals/metalloids – A research prospectus
Published in Journal of Toxicology and Environmental Health, Part B, 2021
Jennifer L. Griggs, David J. Thomas, Rebecca Fry, Karen D. Bradham
Validated bioaccessibility models have standardized procedures for assay methodology, data collection and analysis, and interpretation. Standardization ensures inter- and intra-lab reproducibility and enables comparison of data from studies based upon common protocols. The lack of standardization increases variability among studies. Inter-study variability might arise from differences among samples or variations in test procedures. Differences among samples tested in different labs might be minimized by common collection and processing of samples with a consistent chain of custody that ensures provenance and history of a tested sample be documented. Differences in test procedures may be minimized by the development of detailed operating procedures that fully describe all materials and methods and strict adherence to these protocols. Routine evaluation of test materials with certified values for analytes of interest such as Standard Reference Materials from the National Institute of Standards and Technology might be employed to track intra- and inter-lab variability.
Is the Evaluation of Thermodynamic Parameters from Distribution Ratios a Proper Approach?
Published in Solvent Extraction and Ion Exchange, 2018
Distribution ratios are numerical values that indicate the distribution of a chemical analyte in question between immiscible liquids (solvent extraction) and between solid and liquid phases (adsorption). Analytes include ions, complexes, and molecules, in effect any chemical entity of interest that one can determine by chemical analysis. The temperature dependence of distribution ratios is often treated by a van’t Hoff analysis, yielding parameters that have empirical value for interpolations, comparisons, and process control. Aside from the common objections to the van’t Hoff treatment (e.g., constancy of ΔCp), do these parameters have thermodynamic meaning in terms of ΔS0 and ΔH0 for the distribution reaction? In this letter, it is shown that the answer is affirmative in only special cases.