Analytical technique

Techniques used for specified object Remarks and selected references 

Mercury UV-Spectroscopy (Mariner 10) He, Ar in atmosphere (exosphere). Stem 1999b. 

Venus Mass spectrometry, gas chromatography (Pioneer Venus, Venera 11-14) Atmospheric analyses. Hoffman et al. 1980a,b Donahue and Pollack 1983 Moroz 1983. 

Moon Ion- and neutral mass spectrometry UV spectroscopy Mass spectrometry, laboratory (Apollo Luna samples, lunar meteorites) He and Ar in lunar exosphere on ground, Ar/ °Ar. Stem 1999b. Upper limit for Kr, Xe from orbit. Feldman and Morrison 1991. Ar-Ar ages, exposure ages, solar wind etc. Turner 1970 Culler et al. 2000 Wieler 1998. 

Mars Mass spectrometry (Viking) EUV spectroscopy Mass spectrometry, laboratory (Martian meteorites) Atmosphere. Nier and McElroy 1977 Owenetal. 1977. He in atmosphere. Krasnopolsky et al. 1994. Martian atmosphere, cmst, mantle. Bogard et al. 1984 Becker and Pepin 1984 Swindle 2002b. 

Analytical techniques that utilise biopolymers, ie, natural macromolecules such as proteias, nucleic acids, and polysaccharides that compose living substances, represent a rapidly expanding field. The number of appHcations is large and thus uses hereia are limited to chiral chromatography, immunology, and biosensors. 

Some physical properties of the four most common cyclodexttins are Hsted in Table 1 (3). Other important properties are (/) cyclodexttins are nonreducing (2) glucose is the only product of acid hydrolysis (J) molecular weights are always integral numbers of 162.1, the value for glucose (4) cyclodexttins are nontoxic and (5) they do not appreciably absorb ultraviolet (uv) or visible light. 

Kirk-Othmer Encyclopedia of Chemical Technology (4th Edition) 

Several procedures are used to control the ratios of cyclodextrins produced. One is addition of a substance to the reaction mixture that can gready affect the formation of one specific cyclodextrin over another. For example, in the presence of 1-decanol and 1-nonanol, a-cyclodextrin is produced almost exclusively whereas hexane or toluene promote the production of P-cyclodextrin. Conversely both cyclodextrins are produced simultaneously in the presence of 1-heptanol (2,4). 

Immobilization. The abiUty of cyclodextrins to form inclusion complexes selectively with a wide variety of guest molecules or ions is well known (1,2) (see INCLUSION COMPOUNDS). Cyclodextrins immobilized on appropriate supports are used in high performance Hquid chromatography (hplc) to separate optical isomers. Immobilization of cyclodextrin on a soHd support offers several advantages over use as a mobile-phase modifier. For example, as a mobile-phase additive, P-cyclodextrin has a relatively low solubiUty. The cost of y- or a-cyclodextrin is high. Furthermore, when employed in thin-layer chromatography (tic) and hplc, cyclodextrin mobile phases usually produce relatively poor efficiencies. 

We discuss here techniques used by us for the analysis of PCP and lindane by gas chromatography with mass spectrometric detection. A GC-17A gas 

Oven Temp.fC) Oven Equil.Time(inin) Injector Temp.fC) Interface Temp.fC) Sampling Time(min) 50.0  

Column Pressure(kPa) B5.4 Column Flow inl/niin] 1.2 Linear Velocity 135.9 

Component Masses used Sampling rate (s) Gain 

In the quantitative determination of lindane and PCP from the matrix blood, the sample preparation process is an essential step for ensuring that the results will be of good quality. In this process, interfering substances contained in the matrix are removed, and the substances to be determined are converted into a chemical form that enables them to be measured by GCZMS. 

The analytical techniques have been divided into three groups the first group contains those techniques that are used to characterise the surface of fillers by understanding their reactivity with probe molecules. These are FMC and inverse gas chromatography (IGC) and are discussed in Section 3.4. 

The second group of techniques are the spectroscopic techniques that provide elemental and chemical analysis. These are diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), XPS, and SIMS. XPS and SIMS probe the first few nanometres of the surface whereas DRIFTS probes an order of magnitude deeper. These techniques are discussed in Section 3.5. 

The third group of techniques [wide angle X-ray diffraction (WAXS) and differential scanning calorimetry (DSC)] are those that are able to examine formation of structural order within adsorbed layers of surface treatments on filler surfaces. These are discussed in Section 3.6. 

Many analytical techniques have been used to study deoxy- and oxymyoglobin and hemoglobin and their model compounds. A summary of these techniques, adapted 

Extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) methods yield information on the number, type, and radial distance of ligand donor atoms bonded to the metal.43 XANES may yield geometric information as well. 

X-ray single-crystal diffraction yields precise three-dimensional structure, bond distances, and angles for small molecules with the same information 

Electron paramagnetic resonance (EPR) yields the location of unpaired electron density from hyperfine splitting by metals or atoms with nuclear spin.21 The S = 0 Fe(III)—O 2 state of oxy-Mb or Hb would be indicated by the absence of an EPR signal, although other results such as the IR or resonance Raman absorption of the O2 moiety would be needed for positive confirmation. 

Nuclear magnetic resonance may yield identification of histidine by deuterium exchange (N-H versus N-D) at or near the metal, especially if paramagnetic.252 The resonances are moved away from the 0-10 ppm region as a result of a paramagnetic center in proximity. 

Methods of detection and assay of stable isotopes depend upon the differences in their physical properties. The four most important techniques are mass spectrometry, nuclear magnetic resonance spectrometry, optical emission spectroscopy, and infrared spectroscopy. 

Mass spectrometry is the most versatile and widely used technique and is capable of great sensitivity. It can be employed for a whole range of isotope analyses. The analysis of simple gases using the isotope mass spectrometer is of particular importance in clinical applications and will be treated in some detail. The pharmacologist is frequently concerned with complex mixtures and it is in this area that the organic mass spectrometer linked to the gas chromatograph has assumed an important role. 

The nuclear magnetic resonance spectrum gives very specific structural information that enables the position of labelled nuclei in a molecule to be defined. The technique has been especially important in studies of biosynthesis. Rapid 

Optical emission spectroscopy is more limited in its application but has nevertheless established an important role. It has found particular use for the measurement of nitrogen-15 levels in agricultural studies. Its limitations arise from the necessity to convert the sample to nitrogen gas for measurement. 

In certain cases, infrared spectra give useful and important information on isotope labelling although the method is not of widespread or general importance. Activation analysis and the use of Raman scattering have also been employed for isotope ratio measurements. 

Diamond is often found in combination with other carbon allotropes and it is necessary to clearly identify each material by determining its structure, atomic vibration, and electron state. This is accomplished by the following techniques. 

Diffraction Techniques. Diffraction techniques can readily reveal the crystalline structure of bulk diamond or graphite. However, in many cases, a material may be a complex mixture of diamond, graphite, and amorphous constituents on a size scale that makes them difficult to resolve even with electron microscopy and selected area diffraction (SAD). Consequently, the results of these diffraction techniques have to be interpr ed cautiously. 

In addition, electron diffraction patterns of polycrystalline diamond are similar to those of basal-plane oriented polycrystalline graphite and, when analyzing mixtures of the two, it may be difficuitto separate one pattern from the other. Unfortunately, mixed graphite-carbon-diamond aggregates eire common in natural and synthetic materials. 

Raman Spectroscopy. Fortunately an alternate solution to identification is offered by Raman spectroscopy. This laser-optical technique can determine with great accuracy the bonding states of the carbon atoms (sp for graphite or sp for diamond) by displaying their vibrationcil properties.f l The Raman spectra is the result of the inelastic scattering of optical photons by lattice vibration phonons. 

As shown in Fig. 11.1, the presence of diamond and/or graphite bonding is unambiguous and clear. Single-crystal diamond is identified by a single sharp Raman peak at 1332 cm (wave numbers), often referred to as the D-band, and graphite by a broader peak near 1570 cm (the G-band) and several second-order features. 

The inspection system s ability to identify, measure, and analyze defect data after assembly is also critical. Inspecfion of BGA solder joint integrity is important but cannot be effectively achieved by visual inspecfion because of hidden solder joints. For these types of packages, in addition to process control during manufacturing, nondestructive techniques such as x-ray are needed to determine the integrity of an attachment 

Merits of the visual and x-ray nondestructive techniques are compared in Table 1. This table summarizes various general solder joint defects 

Inspecfion of fine internal structures of microelectronics assemblies, the alignment of hidden interconnects, bridges, and voids in BGA assemblies, can be carried out using real time X-ray techniques. However, internal package delami-nafion cannot be detected by x-ray and other tools such as C-mode scanning acoustic microscopy (C-SAM) are needed. 

Use of nondestructive techniques is limited to research study for characterization of failure mechanisms, or when investigating root cause of a field failure. Destructive techniques commonly include cross-sectioning combined with optical inspecfion, and SEM and EDX. Chemical etching solutions are used to reveal features of solder alloy microstructures and interface in-termetalUc formation. Mechanical destructive tests such as lead pull test for leaded packages and dye-and-pry for area packages are also performed to determine quality and damage levels. 

For characterizafion of failure mechanism by metallography, samples are prepared by cross-sectioning, mounting in polymer, polishing to a smooth cut surface, and chemical etching to reveal nucrostructures. Prior to cross-sectioning. 

Before describing numerical methods, the technique of using analytical or pseudo-analytical solutions will be discussed. Strictly speaking, a problem has an analytical solution if a mathematical equation can fully describe the phenomena examined. This is usually reserved for simple geometries, with simple conditions and properties. However, by applying specific assumptions and limiting the scope of the problem to be solved, analytical techniques can be applied to more realistic situations. In 

Flow 2000(TM) Suite of CAE Tools for Extrusion, Compuplast International 

Modifying the screw design, material or operating conditions can result in a completely different solid bed profile as shown in Fig. 12.1(b) [4]. In this case, the simulation predicts that the solid bed width reduces much slower and that melting is not completed until the very end of the screw. This is clearly a less desirable condition than the one shown in Fig. 12.1(a) because there is the potentiai for some materiai not to melt and mix properly before leaving the extruder. An extreme case of this can result if the reduction in the solid bed is slower than the compression rate of the screw. In this case, the volume of the channel is reducing faster than the voiume of the solid bed. This forces the solid bed to expand, accelerate, or break-up. Premature solid bed break-up can lead to extrudate surging and a poorly mixed material. 

The method of applying analytical techniques for the simulation of the extrusion process is currently the most common to design an extrusion system. When the fine details of flow and how it influences the quality of the extrusion process are of interest, more detailed numerical techniques are typically preferred. 

Specificity is the most important requirement in gas analysis. Techniques dependent on the physical properties of the gas molecules, such as thermal conductivity, density, viscosity, and sound velocity, generally have insufficient specificity to differentiate a single gas in a mixture of gases, and therefore must incorporate in the procedure some type of preliminary separation. Vapor phase fractionation (gas chromatography) is an example of a popular analytical technique based upon a physical property (thermal conductivity) of the gas that requires preliminary separation of the gases by means of special columns (molecular sieve, silica gel, etc.). 

The mass spectrometer is theoretically capable of analyzing any gas in a mixture of gases with a speed, specificity, sensitivity, and accuracy that cannot be matched by other known means of analysis. However, the initial cost of the instrument and accessory equipment has thus far precluded its widespread use. Fowler and Hugh Jones described a mass spectrometer specifically for respiratory physiological studies. Extensive use has been made of this instrument (W6-W8). 

If neither speed of analysis nor continuous analysis is required, the volumetric or manometric techniques may be employed. The volumetric method of gas analysis is based on the selective chemical absorption of components of the gas mixture, first CO2 and then O2. The change in volume, at constant 

In the same year that Clark modified the oxygen electrode. Stow et al. 

Naturally occurring and synthetic radioactive and nonradioactive isotopes of the atmospheric gases have been employed for studies on various circulatory and respiratory problems as well as their interrelationship. Probably the most conunonly employed isotope for studying ventilation-perfusion relationships is krypton-85 xenon-133 and oxygen-15 also have been used. Oxygen-15, like the other radioactive gases, can aid in localizing 

In atomic absorption spectroscopy (AAS) the technique using calibration curves and the standard addition method are both equally suitable for the quantitative determinations of elements. 

Theoretically, the absorbance must be proportional to concentrations, however, deviations from linearity usually take place. Therefore, it is necessary to prepare an empirical calibration curve (ECC). For this, the standard solutions of the element(s) to be determined are employed to plot the ECC from which the contents in the test solutions may be measured conveniently. 

The standard addition method is widely employed in AAS. In this case, two more aliquots of the sample are transferred to volumetric flasks. The first, is diluted to volume, and the absorbance of the solution is measured. The second, receives a known quantity of analyte, whose absorbance is also measured after dilution to the same volume. Likewise, data for other standard additions may also be obtained. 

If a plot between absorbance and concentration reveals a linear relationship, which may be accomplished by several stepwise standard additions, the following expressions hold good, namely  

When a number of stepwise additions are performed, AT can be plotted against Cx. Thus, the resulting straight line may be extrapolated to Ax = 0. By substituting this value in Eq. (c) we may have at the intercept  

Try this short test. If you score more than 80% you can use the chapter as a revision of your knowledge. If you score less than 80 % you probably need to work through the text and test yourself again at the end using the same test If you still score less than 80 % then come back to the chapter after a few days and read 

1 What property of an atom or ion does mass spectroscopy use in 

What property of a compound does infrared spectroscopy use 

What is the advantage of electron microscopes over conventional 

Chemistry An Introduction for Medical and Health Sciences, A. Jones 2005 John Wiley Sons, Ltd 

RHEED Reflection high-energy electron diffraction 

XPS-EELS Electron energy loss spectroscopy based on XPS spectra 

XTEM Cross-sectional transmission electron microscopy 

The most widely available technique for identifying mainly polymer, but also additives in plastics, is Fourier Transform Infrared (FTIR) spectroscopy. Samples are exposed to infrared light (4000-400 wavelengths per centimetre or cm ) causing chemical bonds to vibrate at specific frequencies, corresponding to particular energies. In the last 5 years, an accessory for FTIR has been developed, which enables non-destructive examination of surfaces and so is ideal for analysis of plastics in museum collections. Attenuated Total Reflection-FTIR (ATR-FTIR) requires samples to be placed on a diamond crystal with a diameter of 2 mm through which the infrared beam is reflected 

orhnmic snbstances (Briichert 1998 Senesi and Miano 1994 Rashid 1985) reqnires a modification of the scheme in Fignre 4.21. Other than in inorganic geochemical analysis, where modern instrumentation allows the simnltaneous determination of a wide range of element concentrations, 

The isotope-exchange technique is essentially different. The isotope-incorporation method can lead to valuable deductions about reaction mechanisms and reaction intermediates, but much more direct information of this kind is provided by isotope-exchange studies. In these, a labeled substance is introduced into a reacting mixture and from the extent to which the isotope undergoes exchange, conclusions can be drawn about the nature of the reaction intermediates, and hence about the overall mechanism. 

The kinetic-isotope method is distinctly different from the tracer method. Here we make use of the fact that isotopic substitution leads to changes in rate constants which in some cases can be satisfactorily correlated with the reaction mechanism. 

The measurement of the rate for a particular system can thus lead to conclusions about the nature of the slow step in the reaction—for example, about whether or not a hydrogen atom is being transferred. 

The importance of the isotope-dilution technique is that it can be used for the quantitative determination of substances present in such small amounts that other methods are difficult to apply. For example, if a protein is hydrolyzed, some of the amino acids are present in very small proportions. In the isotope-dilution technique, we add to such a mixture a pure radioactively-Iabeled sample of the same compound, and isolate a sample of the substance in pure form regardless of yield. We then measure the specific radioactivity of the product, and from the specific activity of the added material we calculate the amount of unlabeled compound originally present. The method of calculation is best explained by means of an example. 

A protein was hydrolyzed and it was desired to determine the amount of arginine present. A 5.1 mg sample of tC-labeled arginine giving 2608 counts per minute (corrected for background) was added to the hydrolysis mixture, and then 12.5 mg of arginine was isolated in pure form. The resulting count was 1032 counts per minute (corrected). Calculate the amount of arginine present in the hydrolysate. 

Chemical analysis like gas chromatography coupled to mass spectrometry (GC-MS) carried out in the lab on the basis of samples collected on adsorbent cartridges does not allow monitoring the odour fluctuation in real time. 

Alternatively, hand-held specific field detectors allow direct measurement and continuous operation. Particular volatiles, such as hydrogen sulphide, ammonia or total reduced sulphur (TRS), can be continuously recorded and a sudden signal rise can be considered as a sign of the odour emergence for a given source. 

However, it is true only if the particular volatiles are correlated to the concentration of the odour of interest. Measuring odours with too specific gas detectors is only suited for emissions with well known gaseous compositions. Moreover, for industrial sites characterised by various gas releases, different types of emission can generate the same signal. 

Highly purified Gal-jS-CD can be obtained by using preparative HPLC. Column of the preparative HPLC is the reversed-phase C18 column. Branched-y3-CD (retention time 9.798 min) comes earlier than /3-CD (retention time 11.808 min). In order to obtain high purity products, collection begins after the peak comes out, and ends after the peak completely disappears. After preparative HPLC, pure Gal-jS-CD powder can be obtained by freeze-drying the purified Gal-jS-CD solution. 

When the output of the numerical analysis is requested in terms of floor response spectra, maximum relative displacements, relative velocities, absolute accelerations and maximum stresses during an earthquake, linear dynamic analysis (e.g. direct time integration, modal analysis, frequency integration and response spectrum) is generally adequate for most models. Alternatively, non-hnear dynamic analysis should be used where appropriate or necessary (e.g. structural hft-off, non-linear load dependent support, properties of foundation materials in soil-structure interaction problems or interactions between solid parts). 

The trade-off between linear and non-linear solutions is governed by the conditions in each individual case the latter usually require better defined input parameters, where these introduce uncertainties. The decision should therefore be informed by conducting parametric studies. 

Simplified methods, such as the equivalent static, should be restricted to use for assessment purposes. 

In the response spectrum method, the maximum response of each mode should be calculated by direct use of the design response spectrum. The maximum response in each principal direction should be determined by an appropriate combination of the modal maxima, such as the square root of the sum of the squares of each modal response, or by the complete quadratic combination procedure. For closely spaced modal frequencies, a conservative procedure should be applied by taking the sum of the absolute values of each closely spaced modal and rigid response. The missing mass as a function of the modelling detail, cut-off frequencies and modal participation factors used in the analysis should also be carefully assessed and documented. 

Responses due to input acceleration in the three different directions should be combined by taking the square root of the sum of the squares of individual responses. In some States, horizontal input motion is defined as the resultant in one of the two reference horizontal orthogonal directions and is combined with the vertical motion to determine the worst case response. 

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In this section we will discuss only the analytical techniques that are in very general usage without presenting the older chemical methods. 

Finally it is likely that attention will be focused on emissions of polynuclear aromatics (PNA) in diesel fuels. Currently the analytical techniques for these materials in exhaust systems are not very accurate and will need appreciable improvement. In conventional diesel fuels, emissions of PNA thought to be carcinogenic do not exceed however, a few micrograms per km, that is a car will have to be driven for several years and cover at least 100,000 km to emit one gram of benzopyrene for example These already very low levels can be divided by four if deeply hydrotreated diesel fuels are used. 

Chemists frequently work with measurements that are very large or very small. A mole, for example, contains 602,213,670,000,000,000,000,000 particles, and some analytical techniques can detect as little as 0.000000000000001 g of a compound. For simplicity, we express these measurements using scientific notation thus, a mole contains 6.0221367 X 10 particles, and the stated mass is 1 X 10 g. Sometimes it is preferable to express measurements without the exponential term, replacing it with a prefix. A mass of 1 X 10 g is the same as 1 femtogram. Table 2.3 lists other common prefixes. 

Measurements are made using appropriate equipment or instruments. The array of equipment and instrumentation used in analytical chemistry is impressive, ranging from the simple and inexpensive, to the complex and costly. With two exceptions, we will postpone the discussion of equipment and instrumentation to those chapters where they are used. The instrumentation used to measure mass and much of the equipment used to measure volume are important to all analytical techniques and are therefore discussed in this section. 

There is an obvious order to these four facets of analytical methodology. Ideally, a protocol uses a previously validated procedure. Before developing and validating a procedure, a method of analysis must be selected. This requires, in turn, an initial screening of available techniques to determine those that have the potential for monitoring the analyte. We begin by considering a useful way to classify analytical techniques. 

A second class of analytical techniques are those that respond to the relative amount of analyte thus... 

Second, the majority of analytical techniques, particularly those used for a quantitative analysis, require that the analyte be in solution. Solid samples, or at least the analytes in a solid sample, must be brought into solution. 

Atomic absorption, along with atomic emission, was first used by Guystav Kirch-hoff and Robert Bunsen in 1859 and 1860, as a means for the qualitative identification of atoms. Although atomic emission continued to develop as an analytical technique, progress in atomic absorption languished for almost a century. Modern atomic absorption spectroscopy was introduced in 1955 as a result of the independent work of A. Walsh and C. T. J. Alkemade. Commercial instruments were in place by the early 1960s, and the importance of atomic absorption as an analytical technique was soon evident. 

Slavin, W. A Gomparison of Atomic Spectroscopic Analytical Techniques, Spectroscopy 1991, 6, 16-21. 

The potentiometric determination of an analyte s concentration is one of the most common quantitative analytical techniques. Perhaps the most frequently employed, routine quantitative measurement is the potentiometric determination of a solution s pH, a technique considered in more detail in the following discussion. Other areas in which potentiometric applications are important include clinical chemistry, environmental chemistry, and potentiometric titrations. Before considering these applications, however, we must first examine more closely the relationship between cell potential and the analyte s concentration, as well as methods for standardizing potentiometric measurements. 

In potentiometry, the potential of an electrochemical cell under static conditions is used to determine an analyte s concentration. As seen in the preceding section, potentiometry is an important and frequently used quantitative method of analysis. Dynamic electrochemical methods, such as coulometry, voltammetry, and amper-ometry, in which current passes through the electrochemical cell, also are important analytical techniques. In this section we consider coulometric methods of analysis. Voltammetry and amperometry are covered in Section 1 ID. 

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. 

An analytical technique in which samples are injected into a carrier stream of reagents, or in which the sample merges with other streams carrying reagents before passing through a detector. 

Gas chromatography/ma.ss spectrometry (GC/MS) is an analytical technique combining the advantages of a GC instrument with those of a mass spectrometer. 

Because a GC and an MS both operate in the gas phase, it is a simple matter to connect the two so that separated components of a mixture are passed sequentially from the GC into the MS, where their mass spectra are obtained. This combined GC/MS is a very powerful analytical technique, the two instruments complementing each other perfectly. 

LC operates in the liquid phase, while MS is a gas-phase method, so it is not a simple matter to connect the two. An interface is needed to pass separated components of a mixture from the LC to the MS. With an effective interface, LC/MS becomes a very powerful analytical technique. 

Emission spectroscopy is a very useful analytical technique in determining the elemental composition of a sample. The emission may be produced in an electrical arc or spark but, since the mid-1960s, an inductively coupled plasma has increasingly been used. 

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