Atomic Spectroscopy in Food AnalysisUpdate based on the original article by Scott A. Baker and Nancy J. Miller‐Ihli,Encyclopedia of Analytical Chemistry, © 2000, John Wiley & Sons, Ltd

Abstract

There are several reasons that can explain why food analysis is a topic of strong interest for a large number of institutes around the world. Consumer demands have increased toward healthier and safer food products produced in environment‐friendly conditions. Food manufacturers and food distribution companies have to improve their quality control (QC) of raw materials, manufacturing processes, and end‐products to provide safe, healthy, and high‐quality products at reasonable price. Evaluation of element (e.g. essential and toxic) contents is an important part of nutrition and health claims made on foods. The methods best suited to meet this task are atomic spectroscopic methods such as atomic absorption, atomic emission, and elemental mass spectrometry (MS). Methods commonly used in the generation of food composition data include flame atomic absorption spectrometry (FAAS), graphite furnace atomic absorption spectrometry (GFAAS), inductively coupled plasma atomic emission spectrometry (ICP/AES), and inductively coupled plasma mass spectrometry (ICP/MS). FAAS and ICP/AES offer similar detection limits (DLs) (ng mL −1 levels), whereas GFAAS and ICP/MS can provide sub‐ng mL −1 detection capability. The choice of a method often depends on detection capability, but ease of use, speed of analysis, and cost must also be considered. ICP/AES, ICP/MS, and more recently GF/AAS offer the advantage of providing simultaneous multielement measurements, making them well suited for the analysis of large numbers of elements in food samples. If one or a few elements are to be determined, less expensive atomic absorption spectrometry (AAS) methods might be more suitable. The most critical stage in the development of analytical methods is sample preparation. Samples can be prepared using numerous procedures, but the most useful for a wide range of analytes and sample matrices are based on wet ashing of the sample. In addition to total element determinations, speciation measurements are important to determine the exact chemical form of the element that is present in the sample. As important properties, such as the bioavailability of an element, are dependent on its chemical form (speciation), the development of reliable methods for identification and quantification of trace element species is critical. The most practical difficulty encountered in speciation is to preserve the integrity of the sample and the species of interest during sampling, storage, and sample preparation. Hyphenated techniques, such as the coupling of chromatographic separation and atomic spectroscopic detection, have proven useful for elemental speciation measurements.

Permeation properties and hydrothermal stability of allylhydridopolycarbosilane (AHPCS)-derived silicon carbide (SiC) membranes

“…Therefore, H 2 of lower molecular weight diffuses faster than He of larger molecular weight. 24 If the membrane pores are extremely small, comparable to the molecular size of the gas, then the permeation mechanism of gases is determined by molecular sieving, resulting in higher permeance for He than H 2 , since the kinetic diameters of He and H 2 are 0.26 and 0.289 nm, respectively. The highest H 2 permeance was obtained by firing the AHPCS membrane at 500–600 °C, and firing at 700 °C or higher temperature induces the shrinking of the pores, which increased friction of the permeation of gas molecules and caused the increase of the activation energy and the decrease of H 2 permeance.…”

“…Transport through this type of membrane is complex, since it includes both diffusion in the gas phase and diffusion of the adsorbed phase on the surface of the pores (surface diffusion). 24,30 Therefore, the temperature dependence of permeance of He, N 2 and H 2 O was evaluated in binary mixtures of H 2 O/N 2 and H 2 O/He at 200–400 °C.…”

Recent progress in microfiltration polypropylene membrane fabrication by stretching method

“…The separation performances of a polymer membrane are determined by its intrinsic properties such as polymer crystallinity, hydrophobicity/hydrophilicity, generated charge, surface roughness, as well as porous structure across the membrane [13][14][15][16]. According to their average pore diameter, membranes can be classified into four classes: (1) conventional filtration (10-100 µm), microfiltration (0.1-10 µm), ultrafiltration (1-100 nm) and reverse osmosis (~0.1 nm) [17,18]. Most commercialized PP membranes are classified as microfiltration (MF) membrane.…”

Molecular Dynamics Simulation on the Separation of Ethanol/Water in the New 6FDA/mODMS Membranes

“…In this procedure, a Metropolis algorithm was used to decide on sorbate insertion and deletion as well as the acceptance or rejection of configurational moves (rotation and translation of the sorbate molecules) [15] . The dual-mode sorption model was illustrated to study the penetrant sorption behaviors from lower to higher pressure in this work, as the following equations [16][17][18] described:…”