Quantitative Analysis Capability

Analysis performed using laboratory instruments can provide good quantitative results, because the laboratory environment is well controlled and calibration curves can be obtained with standard samples. Field instruments have to operate under harsh environmental conditions where temperature and humidity level can vary widely. Establishing standard calibration curves for an anergency situation is not practical. Field detectors can only be precalibrated in the laboratory for field applications, based on the assumption that the detector will perform the same or similarly under field conditions. Whether this assumption is valid depends on the relative ability of the detector to perform under field environmental conditions and stability of the detector after cahbration. Many factors could affect the validity of this assumption. Environmental conditions such as humidity, dust, temperature, and potential interfering substances could affect quantitative or qualitative results. 

Fortunately, in many situations precise quantitative analysis is not required. It is more important to know qualitatively and semiquantitatively whether the concentration of targeted chemicals surpasses certain levels. Therefore, semiquantitative analysis and qualitative analysis could satisfy such requirements. A semiquantitative detection result would indicate the approximate concentration range instead of an actual concentration level. Quahtative types of detectors only indicate whether taigeted chemicals are detected at above-LOD levels, and do not display approximate concentrations. 

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FPDs such as MINICAM use the intensity of signals generated by sulfur or phosphorous to determine target chemical concentration in the sample. They are widely used in laboratories for determining concentrations of CWAs in samples and have demonstrated excellent quantitative analysis capability. For field applications, responses are presented in a semiquantitative manner for simplicity. As an example, the AP2C detector uses five light bars to indicate detected concentration levels. 

Paianco S., Alises a., Cunat J., Baena j. and Laserna J. J. (2003) Development of a portable laser-induced plasma spectrometer with fully-automated operation and quantitative analysis capabilities, J. Anal. At. Spectrom. 18 933-938. 

Details are given of a thermal analysis technique, referred to as micro thermal analysis, which combines the high resolution positioning of scanning probe microscopy with some of the quantitative analysis capabilities of conventional thermal analysis. The application of this technique in characterising the thermal properties of interfaces in aluminium/epoxy resin adhesive joints and in glass fibre-reinforced epoxy resin composites is described. 7 refs. 

The search for Turing patterns led to the introduction of several new types of chemical reactor for studying reaction-diffusion events in feedback systems. Coupled with huge advances in imaging and data analysis capabilities, it is now possible to make detailed quantitative measurements on complex spatiotemporal behaviour. A few of the reactor configurations of interest will be mentioned here. 

The quantitative imaging capability of the NMP is one of the major strengtiis of the teclmique. The advanced state of the databases available for PIXE [21, 22 and 23] allows also for the analysis of layered samples as, for example, in studying non-destmctively the elemental composition of fluid inclusions in geological samples. 

It would appear that measurement of the integrated absorption coefficient should furnish an ideal method of quantitative analysis. In practice, however, the absolute measurement of the absorption coefficients of atomic spectral lines is extremely difficult. The natural line width of an atomic spectral line is about 10 5 nm, but owing to the influence of Doppler and pressure effects, the line is broadened to about 0.002 nm at flame temperatures of2000-3000 K. To measure the absorption coefficient of a line thus broadened would require a spectrometer with a resolving power of 500000. This difficulty was overcome by Walsh,41 who used a source of sharp emission lines with a much smaller half width than the absorption line, and the radiation frequency of which is centred on the absorption frequency. In this way, the absorption coefficient at the centre of the line, Kmax, may be measured. If the profile of the absorption line is assumed to be due only to Doppler broadening, then there is a relationship between Kmax and N0. Thus the only requirement of the spectrometer is that it shall be capable of isolating the required resonance line from all other lines emitted by the source. 

HPLC is a very powerful technique for qualitative and quantitative analysis. In the support of process development, HPLC plays an important role in monitoring a reaction, since each reaction component can be quantitated. In this role, the HPLC method must be fast, rugged, and specific, capable of separating all reactants, products, and byproducts. Development of appropriate analytical methods is often a rate-limiting step in process development. 

Generally SFE has proved a greater success than SFC. However, the need for successful automation is a significant restriction in many routine applications. SFE has been promoted as the ideal technique for sample preparation for chromatography. Meanwhile it is clear that this is far too optimistic [77,292]. As shown in Section 3.4.2.7, SFE does not guarantee quantitative analysis. Before any technique can be fully accepted, it should be capable of generating reproducible results. This is clearly not the case in SFE. Also, sample sizes of (on-line) SFE tend to be much smaller than in other methods, such as MAE or ASE (Table 3.4), which raises the risk of nonrepresentative sampling. There is a need for SFE to be carried out on reference materials of known composition determined by an alternative technique. 

Table 8.62 shows the main characteristics of ICP-MS, which is widely used in routine analytical applications. The ICP ion source has several unique advantages the samples are introduced at atmospheric pressure the degree of ionisation is relatively uniform for all elements and singly charged ions are the principal ion product. Theoretically, 54 elements can be ionised in an ICP with an efficiency of 90 % or more. Even some elements that do not show ionic emission lines should be ionised with reasonable efficiency (namely, As, 52 % and P, 33%) [381]. This is one of the advantages of ICP-MS over ICP-AES. Other features of ICP-MS that make it more attractive than ICP-AES are much lower detection limits ability to provide isotopic ratio information and to offer isotope dilution capabilities for quantitative analysis and clean and simple spectra. The... 

Si(Li) spectroscopy, with the capability of simultaneous quantitative analysis of 72 elements ranging from sodium through to uranium in solid, liquid, thin film and aerosol filter samples. The penetrating power of protons allows sampling of depths of several tens of microns, and the beam itself may be focussed, rastered or varied in energy. The use of a proton beam as an excitation source offers several advantages over other X-ray techniques, for example there is a higher rate of data accumulation across the entire spectrum which allows for faster analysis. 

In recent years, several groups have proposed the use of Laser Induced Breakdown Spectroscopy as a technique capable of giving information on the pigment compositions with minimal damage of the artwork. However, until the development of quantitative methods for accurate elemental analysis, the LIBS technique was hardly competitive with other methods for quantitative analysis of the samples. 

CE instrumentation is quite simple (see Chapter 3). A core instrument utilizes a high-voltage power supply (capable of voltages in excess of 30,000 V), capillaries (approximately 25—lOOpm I.D.), buffers to complete the circuit (e.g., citrate, phosphate, or acetate), and a detector (e.g., UV-visible). CE provides simplicity of method development, reliability, speed, and versatility. It is a valuable technique because it can separate compounds that have traditionally been difficult to handle by HPLC. Furthermore, it can be automated for quantitative analysis. CE can play an important role in process analytical technology (PAT). For example, an on-line CE system can completely automate the sampling, sample preparation, and analysis of proteins or other species that can be separated by CE. 

Another recent innovation is the QTrap mass spectrometer. The QTrap MS system combines the capabilities of a triple quadrupole mass spectrometer and a linear ion trap mass spectrometer into one MS system. Initially, the QTrap MS was used primarily as a tool for metabolite identification studies [34, 35, 38]. As reported by Li et al. [138], the QTrap MS can also be used as an excellent system for the quantitative analysis of discovery PK samples. The advantage of the QTrap MS system for quantitative analysis is that it can be used to look for plasma metabolites of the NCE and provide an easy way to monitor them while providing the quantitative data on the NCE. 

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