High-performance liquid chromatography HPLC , with infrared spectroscopy

We will first describe briefly the main experimental techniques coupled with electrochemical methods Infrared Reflectance Spectroscopy (IRS), Electrochemical Quartz Crystal Microbalance (EQCM), Differential Electrochemical Mass Spectrometry (DEMS), Chemical Radiotracers and High Performance Liquid Chromatography (HPLC). 

Chemical analysis of hazardous substances in air, water, soil, sediment, or solid waste can best be performed by instrumental techniques involving gas chromatography (GC), high-performance liquid chromatography (HPLC), GC/mass spectrometry (MS), Fourier transform infrared spectroscopy (FTIR), and atomic absorption spectrophotometry (AA) (for the metals). GC techniques using a flame ionization detector (FID) or electron-capture detector (BCD) are widely used. Other detectors can be used for specific analyses. However, for unknown substances, identification by GC is extremely difficult. The number of pollutants listed by the U.S. Environmental Protection Agency (EPA) are only in the hundreds — in comparison with the thousands of harmful... 

The method of diffuse transmittance (DT) is based on measurement of the radiation component 7dt (Fig. 1.22) that passes diffusely through an inhomogeneous layer. This method was first applied to the IR spectroscopic analysis of thin films on samples in powder form by Tolstoy in 1985 [116, 117], who obtained DT spectra of water adsorbed onto silica gel. When used in conjunction with a FTIR spectrometer, the method is called diffiise-transmittance infrared Fourier transform spectroscopy (DTIFTS). DTIFTS is the most recently developed IR spectroscopic methods for studying powder surfaces and has already found application in high-performance liquid chromatography (HPLC) and thin-layer chromatography (TLC) [118, 119]. Of increasing popularity are DTIFTS measurements of powders that use an IR microscope to collect radiation [112, 119] (Section 4.3). 

Since the oxidation of methanol to CO includes six electrons, the reaction process must involve several steps with several products or intermediates. The results from mass spectral measurements, high performance liquid chromatography (HPLC), and gas chromatography (GC) absorbance have showed that H O, HCOOH, HCOOCH, and CO were all produced during the oxidation of methanol on Pt in acid solutions. These species were formed initially but eventually became CO [92], In addition, some other adsorbed species such as (CHO)ads or (COOH)ads were identified by infrared reflectance spectroscopy or Fourier transform infrared reflectance spectroscopy. The detailed reaction mechanism of methanol oxidation on a Pt electrode is shown in Figure 1.20 [94]. 

In most respects, the standard approach taken to analyze the fatty acids of functional foods is similar to that for conventional foods. The steps are to extract the total lipids or fatty acids, convert the fatty acids to a suitable derivative (often to fatty acid methyl esters (FAME)), and analyze the derivatized fatty acids by a suitable chromatographic technique, usually GC with flame ionization detection (FID), Other chromatographic techniques, including gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC), may be required. Nonchromatographic techniques such as infrared (IR) spectroscopy may be used in some simations, perhaps because of the speed of analysis. 

In the case of heterogeneous polymers the experimental methods need to be refined. In order to analyze those polymers it is necessary to determine a set of functions / (M), which describe the distribution for each kind of heterogeneity i This could be the mass distributions of the blocks in a diblock copolymer. The standard SEC methods fail here and one needs to refine the method, e.g., by performing liquid chromatography at the critical point of adsorption [59] or combine SEC with methods, which are, for instance, sensitive to the chemical structure, e.g., high-pressure liquid chromatography (HPLC), infrared (IR), or nuclear magnetic resonance spectroscopy (NMR) [57],... 

Instmmental methods of analysis provide information about the specific composition and purity of the amines. Qualitative information about the identity of the product (functional groups present) and quantitative analysis (amount of various components such as nitrile, amide, acid, and determination of unsaturation) can be obtained by infrared analysis. Gas chromatography (gc), with a liquid phase of either Apiezon grease or Carbowax, and high performance Hquid chromatography (hplc), using silica columns and solvent systems such as isooctane, methyl tert-huty ether, tetrahydrofiiran, and methanol, are used for quantitative analysis of fatty amine mixtures. Nuclear magnetic resonance spectroscopy (nmr), both proton ( H) and carbon-13 ( C), which can be used for qualitative and quantitative analysis, is an important method used to analyze fatty amines (8,81). 

Initially, simple methods such as ultraviolet-visible (UV-Vis), fluorescence or infrared (IR) spectroscopy were proposed in order to estimate the total amount of antioxidants in various food samples. However, coupled methods such as gas chromatography-mass spectrometry (GC-MS), high performance liquid chromatography with ultraviolet-visible (HPLC-UV-Vis) or nuclear magnetic resonance detector (HPLC-NMR) and liquid chromatography-mass spectrometry (LC-MS) are employed more to quantify individual tocols or carotens from various corn-based food samples. In this chapter all these methods of analysis will be briefly described. 

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