Other Analytes

Octaethylporphyrin and etioporphyrin as well as their Ni and VO complexes were separated on a Cjg column (A = 386-401 nm) using a 94/6 - 100/0 (at 22min hold 2min) (1/1 methanol/acetonitrile)/water gradient [451]. Excellent separation and peak shapes were achieved. Linear ranges of 30-8000 ng/mL were reported. 

Coproporhyrin isomers I and III were isolated from urine and feces and separated on a 29°C Cg column (A=406nm or A = 405nm, ex 620nm, em). A 46-min 100/0 - 35/65 (at 30min)- -10/90 (at 46min) (90/10 water [1 M ammonium acetate buffer at pH 5.5]/acetonitrile)/methanol gradient baseline resolved the analytes. A ramp to 100% methanol was run after the gradient to elute others materials extracted from the sample [452]. Levels of 40-2000 pmol/24 h (urine) and 70-2200 nmol/g (feces) were reported. 

Porphyria associated with a rat model of Wilson s disease included six porphyrins (uro-, hepta-, hexa-, penta-, copro-, and mesoporphyrin). Baseline resolution and excellent peak shapes were generated on a 35°C Cjg column (A = 395 nm, ex 620 nm, em) using an 85/15 (hold 5 min) - -0/100 (at 15 min hold 5 min) water (0.1 M sodium phosphate at pH 3.5)/methanol gradient [453]. For urine extracts, standards of lO-lOOOnM with detection limits of 2nM were reported. 

Five iodoamino acids (3-iodotyrosine [MIT], 3,5-diiodotyrosine [DIT], T3, T4and 3,3, 5 -triiodothyronine [rT3]) were separated on a C,g column (ICP/MS) using a 

10/90 methanol/water mobile phase to quantitate MIT and DIT and a 50/50 methanol/water mobile phase to quantitate MIT/DIT, Tj, T4 and 1T3 [455]. Detection limits, based on iodine equivalents, were reported as 100pg. Linear response was recorded over four orders of magnitude of concentration. Excellent resolution was obtained and total elution was completed in 15 min. 

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The above expressions are empirical approaches, with m and D. as parameters, for including an anliamionic correction in the RRKM rate constant. The utility of these equations is that they provide an analytic fomi for the anliamionic correction. Clearly, other analytic fomis are possible and may be more appropriate. For example, classical sums of states for Fl-C-C, F1-C=C, and F1-C=C hydrocarbon fragments with Morse stretching and bend-stretch coupling anhamionicity [M ] are fit accurately by the exponential... 

Analytical chemists converse using terminology that conveys specific meaning to other analytical chemists. To discuss and learn analytical chemistry you must first understand its language. You are probably already familiar with some analytical terms, such as "accuracy and "precision, but you may not have placed them in their appropriate analytical context. Other terms, such as "analyte and "matrix, may be less familiar. This chapter introduces many important terms routinely used by analytical chemists. Becoming comfortable with these terms will make the material in the chapters that follow easier to read and understand. 

Although many quantitative applications of acid-base titrimetry have been replaced by other analytical methods, there are several important applications that continue to be listed as standard methods. In this section we review the general application of acid-base titrimetry to the analysis of inorganic and organic compounds, with an emphasis on selected applications in environmental and clinical analysis. First, however, we discuss the selection and standardization of acidic and basic titrants. 

Clinical Applications Perhaps the area in which ion-selective electrodes receive the widest use is in clinical analysis, where their selectivity for the analyte in a complex matrix provides a significant advantage over many other analytical methods. The most common analytes are electrolytes, such as Na+, K+, Ca +, H+, and Ch, and dissolved gases, such as CO2. For extracellular fluids, such as blood and urine, the analysis can be made in vitro with conventional electrodes, provided that sufficient sample is available. Some clinical analyzers place a series of ion-selective electrodes in a flow... 

Environmental Applications Although ion-selective electrodes find use in environmental analysis, their application is not as widespread as in clinical analysis. Standard methods have been developed for the analysis of CN , F , NH3, and in water and wastewater. Except for F , however, other analytical methods are considered superior. By incorporating the ion-selective electrode into a flow cell, the continuous monitoring of wastewater streams and other flow systems is possible. Such applications are limited, however, by the electrode s response to the analyte s activity, rather than its concentration. Considerable interest has been shown in the development of biosensors for the field screening and monitoring of environmental samples for a number of priority pollutants. 

In comparison with most other analytical techniques, radiochemical methods are usually more expensive and require more time to complete an analysis. Radiochemical methods also are subject to significant safety concerns due to the analyst s potential exposure to high-energy radiation and the need to safely dispose of radioactive waste. 

Quantitative analytical methods using FIA have been developed for cationic, anionic, and molecular pollutants in wastewater, fresh waters, groundwaters, and marine waters, several examples of which were described in the previous section. Table 13.2 provides a partial listing of other analytes that have been determined using FIA, many of which are modifications of conventional standard spectropho-tometric and potentiometric methods. An additional advantage of FIA for environmental analysis is its ability to provide for the continuous, in situ monitoring of pollutants in the field. ... 

Chemical kinetic methods are particularly useful for reactions that are too slow for a convenient analysis by other analytical methods. In addition, chemical kinetic methods are often easily adapted to an automated analysis. For reactions with fast kinetics, automation allows hundreds (or more) of samples to be analyzed per hour. Another important application of chemical kinetic... 

J)Other analytical methods which include, among many, a thermometric method (104), a high frequency titration (105), and a colored indicator method (106). 

Other analytical techniques ate also available for the determination of maleic anhydride sample purity. For example, maleic anhydride content can be determined by reacting it with a known excess of aniline [62-53-3] in an alcohol mixture (170). The solution is then titrated with an acid to determine the amount of unconsumed aniline. This number is then used to calculate the amount of maleic anhydride reacted and thus its concentration. Another method of a similar type has also been reported (171). 

Measurement of Analytes Biochemical reactions used in the measurement of selected analytes are commercially available as prepackaged kits of reagents. Measurement of the reactions given plus many other analytes can be made (10,11). 

Biosensors (qv) and DNA probes ate relatively new to the field of diagnostic reagents. Additionally, a neat-infrared (nit) monitoring method (see Infrared TECHNOLOGY AND RAMAN SPECTROSCOPY), a teagenfless, noninvasive system, is under investigation. However, prospects for a nit detection method for glucose and other analytes ate uncertain. 

A definitive method for stmctural deterrnination is x-ray crystallography. Extensive x-ray crystal stmcture deterrninations have been done on a wide variety of steroids and these have been collected and Hsted (270). In addition, other analytical methods for steroid quantification or stmcture determination include, mass spectrometry (271), polarography, fluorimetry, radioimmunoassay (264), and various chromatographic techniques (272). 

Infrared Spectroscopy (ir). Infrared curves are used to identify the chemical functionality of waxes. Petroleum waxes with only hydrocarbon functionality show slight differences based on crystallinity, while vegetable and insect waxes contain hydrocarbons, carboxyflc acids, alcohols, and esters. The ir curves are typically used in combination with other analytical methods such as dsc or gc/gpc to characterize waxes. 

The Wealth of Information from Single-Crystal Determinations. The amount of information that is determined from a crystal stmcture experiment is much greater and more precise than for any other analytical tool for stmctural chemistry or stmctural molecular biology. Indeed, almost all of the stmctural information that has been deterrnined for these two fields has been derived from x-ray single crystal diffraction experiments. 

In a general way, the identification of asbestos fibers can be performed through morphological examination, together with specific analytical methods to obtain the mineral composition and/or stmcture. Morphological characterization in itself usually does not constitute a reHable identification criteria (1). Hence, microscopic examination methods and other analytical approaches are usually combined. 

Optimization lefeis to the step in the analytical process (Fig. 2) where some sort of treatment is performed on samples to generate taw data which can be in the form of voltages, currents, or other analytical signals. These data have yet to be caUbrated in terms of chemical concentrations. 

The emitted P particles excite the organic molecules which, in returning to normal energy levels, emit light pulses that are detected by a photomultiplier tube, amplified, and electronically counted. Liquid scintillation counting is by far the most widely used technique in tritium tracer studies and has superseded most other analytical techniques for general use (70). 

The use of agarose as an electrophoretic method is widespread (32—35). An example of its use is in the evaluation and typing of DNA both in forensics (see Forensic chemistry) and to study heritable diseases (36). Agarose electrophoresis is combined with other analytical tools such as Southern blotting, polymerase chain reaction, and fluorescence. The advantages of agarose electrophoresis are that it requires no additives or cross-linkers for polymerization, it is not hazardous, low concentration gels are relatively sturdy, it is inexpensive, and it can be combined with many other analytical methods. 

The other analytical methods necessary to control the typical specification given in Table 5 are, for the most part, common quality-control procedures. When a chemical analysis for purity is desired, acetylation or phthalation procedures are commonly employed. In these cases, the alcohol reacts with a measured volume of either acetic or phthalic anhydride in pyridine solution. The loss in titratable acidity in the anhydride solution is a direct measure of the hydroxyl groups reacting in the sample. These procedures are generally free from interference by other functional groups, but both are affected adversely by the presence of excessive water, as this depletes the anhydride reagent strength to a level below that necessary to ensure complete reaction with the alcohol. Both procedures can be adapted to a semimicro- or even microscale deterrnination. 

Analytical Solutions Solution of the population balance is not trivial. Analytical solutions are available for only a limited number of special cases, of which some of examples of practical importance are summarized in Table 20-59. For other analytical solutions, see general references on population balances given above. 

Recent advances in accelerator technology have reduced the cost and size of an RBS instrument to equal to or less than many other analytical instruments, and the development of dedicated RBS systems has resulted in increasing application of the technique, especially in industry, to areas of materials science, chemistry, geology, and biology, and also in the realm of particle physics. However, due to its historical segregation into physics rather than analytical chemistry, RBS still is not as readily available as some other techniques and is often overlooked as an analytical tool. 

The analytical techniques covered in this chapter are typically used to measure trace-level elemental or molecular contaminants or dopants on surfaces, in thin films or bulk materials, or at interfaces. Several are also capable of providing quantitative measurements of major and minor components, though other analytical techniques, such as XRF, RBS, and EPMA, are more commonly used because of their better accuracy and reproducibility. Eight of the analytical techniques covered in this chapter use mass spectrometry to detect the trace-level components, while the ninth uses optical emission. All the techniques are destructive, involving the removal of some material from the sample, but many different methods are employed to remove material and introduce it into the analyzer. 

A major advantage of static SIMS over many other analytical methods is that usually no sample preparation is required. A solid sample is loaded directly into the instrument with the condition that it be compatible with an ultrahigh vacuum (10" —10 torr) environment. Other than this, the only constraint is one of sample size, which naturally varies from system to system. Most SIMS instruments can handle samples up to 1-2 inches in diameter. 

LIMS analytical applications may be classifted as elemental or molecular survey analyses. The former can be further subdivided into surface or bulk analyses, while molecular analyses are generally applicable only to surface contamination. In the following descriptions of applications, a comparison with other analytical techniques is presented, along with a discussion of their relative merits. 

An especially significant application of NRA is the measurement of quantified hydrogen depth profiles, which is difficult using all but a few other analytical techniques. Hydrogen concentrations can be measured to a few tens or hundreds of parts per million (ppm) and with depth resolutions on the order of 10 nm. 

NRA is an effective technique for measuring depth profiles of light elements in solids. Its sensitivity and isotope-selective character make it ideal for isotopic tracer experiments. NRA is also capable of profiling hydrogen, which can be characterized by only a few other analytical techniques. Future prospects include further application of the technique in a wider range of fields, three-dimensional mapping with microbeams, and development of an easily accessible and comprehensive compilation of reaction cross sections. 

For those suppliers not conforming to Ford, General Motors, and Daimler Ghrylser requirements, other analytical methods and acceptance criteria may be used if approved by the customer. If you lack any documented methods, the MSA Reference Manual is recommended. 

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