Instrumentation software

A measurement system consists of the operations (i.e. the measurement tasks and the environment in which they are carried out), procedures (i.e. how the tasks are performed), devices (i.e. gages, instruments, software, etc. used to make the measurements), and the personnel used to assign a quantity to the characteristics being measured. 

At the end of the 2D experiment, we will have acquired a set of N FIDs composed of quadrature data points, with N /2 points from channel A and points from channel B, acquired with sequential (alternate) sampling. How the data are processed is critical for a successful outcome. The data processing involves (a) dc (direct current) correction (performed automatically by the instrument software), (b) apodization (window multiplication) of the <2 time-domain data, (c) Fourier transformation and phase correction, (d) window multiplication of the t domain data and phase correction (unless it is a magnitude or a power-mode spectrum, in which case phase correction is not required), (e) complex Fourier transformation in Fu (f) coaddition of real and imaginary data (if phase-sensitive representation is required) to give a magnitude (M) or a power-mode (P) spectrum. Additional steps may be tilting, symmetrization, and calculation of projections. A schematic representation of the steps involved is presented in Fig. 3.5. 

The amount of tebuconazole residue (R) is calculated by applying the response factor (RF) to a standard (std) calibration curve. Calculations are performed using the instrument software using the following equation ... 

The successful use of VIRS methods as research tools requires more than anything a published framework that will provide standards for the collection and interpretation of data, and accessible data libraries that can give examples for comparison and contrast. The spectral libraries used for mineral identification are in part public-domain, but much information remains tied to the instrument software and cannot readily be distributed. Differences in the formats used for spectral files in different libraries complicate their use in standard software and impedes information exchange. 

Thanks to Texas Instruments Software/Sterling Software for permission to use the video case study in the book the authors originally developed this example for IT software. 

Other applications of the model 8700 system include fore-flushing and back-flushing of the pre-column, either separately or in combination with heart cutting, all carried out with complete automation by the standard instrument software. 

Dynamic mechanical testers apply a small sinusoidal stress or strain to a small sample of the polymer to be examined and measure resonant frequency and damping versus temperature and forced frequency. Instrument software computes dynamic storage modulus (G ), dynamic loss modulus (G") and tan delta or damping factor. Measurements over a wide range of frequency and temperature provide a fingerprint of the polymer with sensitivity highly superior to DSC. 

The system has a wide range of apphcations and the approach offers many attractions, especially for ICP-AES and ICP-MS. However, to realize the full potential of the system, instrumental software must be provided to integrate these methods into the complete analytical system. 

Other multivariate methods have been applied to ICP spectra for quantitative measurements. As examples, they include multicomponent spectral fitting (which is incorporated in several commercial instrument software) [81] matrix projection, which avoids measurement of background species [94,95] generalised standard additions [96] and Bayesian analysis [97]. 

Figure B3.5.8 Obtaining the corrected near-UV CD spectrum for hen egg white lysozyme. The protein and baseline spectra were collected using a 10-mm cylindrical cell and 0.5 mg/ml protein in 0.067 M phosphate buffer, pH 6.0. Instrument settings were 1-nm bandwidth, 0.2-nm step size, scan speed 2 nm/min, time constant 8 sec (scan speed x time constant = 0.27 nm). Protein solution and buffer were scanned once each. The spectra were smoothed, a sample of the fit being shown in the inset. Reproducibility of the instrument and of the state of the cell are demonstrated by the coincidence of the ellipticity above 300 nm. The corrected spectrum was obtained by subtraction, using the instrument software.

Depending on the level of noise, spectra and baselines can be smoothed using the instrument software. Smoothed and raw spectra should be compared directly by overlaying them on the computer screen in order to avoid the distortion that can arise from overen-thusiastic smoothing. 

Subtract the baseline from the sample spectrum using the instrument software (Fig. B3.6.1). 

Determine the value of the fluorescence intensity at the wavelength of maximum intensity (/max at Xmax) using, where available, the instrument software. 

Fluorescence microspectrophotometry typically provides chemical information in three modes spectral characterization, constituent mapping in specimens, and kinetic measurements of enzyme systems or photobleaching. All three approaches assist in defining chemical composition and properties in situ and one or all may be incorporated into modem instruments. Software control of monochrometers allows precise analysis of absoiption and/or fluorescence emission characteristics in foods, and routine detailed spectral analysis of large numbers of food elements (e.g., cells, fibers, fat droplets, protein bodies, crystals, etc.) is accomplished easily. The limit to the number of applications is really only that which is imposed by the imagination - there are quite incredible numbers of reagents which are capable of selective fluorescence tagging of food components, and their application is as diverse as the variety of problems in the research laboratory. 

Inject successively and in duplicate 0.1 jx samples of each of the mixtures into the column and record the chromatographic traces. Determine the areas under the peaks by both of the following procedures and compare the results with those given by the instrument software, if fitted. 

The injector system is often of the loop type. Here the main solvent delivery tube to the column top is by-passed in a loop, which may be isolated and depressurised, and injected with sample via a septum. After injection the liquid in the loop is released into the main solvent flow. The loop volume is of comparable capacity to the injection volume. Most instruments are designed for autosampling in the case of multiple analyses, the operation being controlled by the instrument software. 

Standard instrument software Software driven by non-user-programmable firmware, which is configurable (GAMP). 

To reduce the detrimental effects of spectral interferences on element quantitation, laboratories select the spectral lines that are least affected by the background, and use the background compensation and interelement correction routines as part of the analytical procedure. The instrument software uses equations to compensate for overlapping spectral lines the effectiveness of these equations in eliminating spectral interferences must be confirmed at the time of sample analysis. That is why laboratories analyze a daily interelement correction standard (a mixture of all elements at a concentration of 100mg/l) to verify that the overlapping lines do not cause the detection of elements at concentrations above the MDLs. 

There are several sources of information that can aid in identifying potential spectral overlaps. Instrument manufacturers typically include spectral overlap information in the instrument software. An atlas of elemental ion spectra as well as many of the molecular ions is available in a very convenient software package, MS Interview, that was published in Spectrochimica Acta Electronica and is available in the Program Library at http //www.elsevier.nl 80/inca/homepage/saa/ sab (download file 47/1621/92 for the Apple Macintosh version, file 48/1063/93 for the PC version). This program also allows users to add additional ions to the spectra] database. 

Mathematical correction procedures can be used to remove the contribution of a spectral overlap from a measured signal. However, if the signal due to the spectral overlap is much larger than the analyte signal, the signal-to-noise ratio of the corrected signal may be poor. Furthermore, it may not be easy to predict and account for quantitatively all of the potential sources of spectral overlap, particularly those due to polyatomic ions. For isobaric overlaps (Table 3.2), for which the relative isotopic abundances are predictable, mathematical corrections are straightforward. Instrument software often has built-in correction equations for this case. 

ICP-MS can provide semiquantitative analysis for about 70 elements by using element response functions built into the instrument software and calibration of only a few elements [205,206]. Most elements are more than 90% ionized in the ICP (with the exception of elements with ionization potentials greater than about 8 eV). Ion transmission efficiency is a smooth function of mass. The natural isotopic abundances of the elements are well known. Therefore, it is possible to predict the relative sensitivities of the elements and any isobaric overlaps. 

The instrument software is set to offer eight predefined analytical methods. All common operational parameters for these methods are presented in Annex 1. The eight analytical methods are as follows ... 

The products of combinatorial chemistry, namely, drug leads, instrumentation software for library data analysis, affinity ligands, etc., are all valuable and useful, because they are geared toward specific applications. For example, entire libraries have value as starting points for drug-lead screening purposes, and leads themselves are very valuable if they show desired effects in screening assays. 

A second-order regression curve (V, = ao + ci Xi + a2Xf) is in most cases sufficient to deal with curvilinear regression curves. The concentration of the analyte in the sample can be back-calculated from the response. Nowadays, most instrument software packages include the use of different types of regression models and the concentration of the samples is automatically back-calculated. 

---