Automatic identity control

Vibrational spectroscopy is best suited for the identification and subsequent quantification of compounds in connection with quality control. A simple but very impressive method of automatic identity control has been described by Weitkamp and Wortig (1977) (see Sec. 5.1.6, 3). 

Automatic identity control by computer assisted IR spectroscopy... 

Figure 5.1-15 Algorithm for the comparison of higher-order spectra for automatic identity control...

The determining of sorting limits of steel parts after thermal processing in order to eliminate these, which indicate exceeded allowed content of residual austenite, requires elements of identical shape and dimensions, as the studied parts, and with known content of residual austenite. Such elements serve to define the sorting thresold, during manual control as well as automatic... 

N Mechanism. This is the mechanism currently in use. It utilizes two solenoids for the actuation of two selectors. The selectors can be manually actuated independently for maximum flexibility. However, in typical operation of the system, an event-end or method-end pulse is sent to the contact closures from the control unit, the pulse actuates both solenoids concurrently, and both selectors are automatically actuated at the same time. When the selectors are actuated, a pair of extraction vessels is selected for the next extraction. Both of these extraction vessels are subjected to the same extraction conditions. Identical or different samples can be analyzed as mem-... 

It consists of a rail-mounted carriage, which carries rows of sample beakers past three stations where each sample receives an aliquot of extractant (usually water), is thoroughly stirred, and has an electrode or electrodes lowered into it. The electrical output from the electrode(s) is passed through an amplifier to a flatbed recorder. Control of the sequence of operations is completely automatic, involving a system of three interlocking motor-driven cam timers, thereby ensuring that each sample receives identical treatment. 

Many modern scanners have a computer-controlled motor-driven monochromator that allovre automatic recording of in situ absorption and fluorescence excitation spectra. These spectra can aid compound identification by comparison with stored standard spectra, test for identity by superimposition of spectra from different zones on a plate, and check zone purity by superimposition of spectra from different areas of a single zone. The spectral maximum determined from the in situ spectrum is usually the optimal wavelength for scanning standard and sample areas for quantitative analysis. 

In the former case, an internal lock is established at the deuterium frequency of the solvent by adjusting the frequency of the lock transmitter until it matches that frequency. The operator typically observes a decreasing number of interference-pattern sine waves as the lock transmitter frequency approaches that of the deuterium nuclei in the solvent. A null appears when the two frequencies are identical the operator then turns the lock control to On. On most modem spectrometers, autolocking procedures are also available that search for the deuterium resonance and automatically lock the spectrometer when the signal is found. 

This fiber-optic dissolution technology represents a considerable breakthrough for the quality control laboratory. It is as accurate and precise as conventional dissolution test measurements and is easy to set up. By combining four tests (dissolution, identity, assay, and content uniformity), which commonly demand 3-4 days of analyst time, the technique requires about half a day of analyst time, and data acquisition is secure, automatic, and archiv-... 

In many cases, the identity of the analyte will be known nonetheless, it is highly desirable that this be confirmed to avoid the possibility that an interfering compound fortuitously has, for example, the same GC or HPLC retention time as that of the desired analyte. Indeed, many protocols that are now advocated use mass spectrometric systems so that this control is automatically incorporated. Samples may be spiked with internal standards to simplify calculation and eliminate small errors in pipetting and injection, or surrogate standards may be employed where, for example, incomplete extraction of the analyte is unavoidable. When MS is used as the detection system, analytes labeled with suitable isotopes have been widely used for PAHs, fully deuterated standards, and for PCBs and agrochemicals, Relabeled compounds. For partially labeled standards of analytes, care must be exercised in their choice if it is intended to analyze for metabolites of a substrate in which the label may have been lost. 

The obvious advantage of the automated thermobalance system over existing instruments is the ability to determine the mass-loss curves of eight successive samples. Operation of the instrument is completely automatic, and once the cycle is begun the instrument does not require the attention of the operator until the eighth sample curve is completed. The instrument should find use for the routine TG examination of a large number of samples, each to be studied under identical thermal conditions. Because the system is completely automated, data reduction or control by a small digital computer could easily be accomplished (see Chapter 14.)... 

GC-MS is a reliable technique for planar PCBs quantitation because of its improved selectivity, particularly given the availability of C-labeled PCB standards. Using isotope dilution, each individual sample (i.e., unknown samples, calibration standards, quality controls, and blanks) is enriched with stable isotope-labeled analogs of analytes of interest, usually C-labeled for PCBs and pesticides. Chemically, the analytes and labeled analogues behave identically however, they can be distinguished based on their mass differences, thus allowing a complete and automatic recovery correction for each analyte in individual sample. These analyses are typically more accurate, selective, and sensitive than GC-ECD analyses to obtain the sensitivity needed, the mass spectrometers must be operated in the selected ion monitoring (SIM) mode. 

We discuss in this chapter analysers that arc highly automated, such as flow injection and discrete analyzers. In addition, laboratory robotic systems that are becoming more and more commonplace for sample handling and preparation arc also described. The latest advances in automation involve the development of microlluidic systems, which are sometimes called lab-on-a-chip or micro total analysis systems. These recent developnienis are also described here. It is important to note that the same principles of automatic analysis discussed here also apply to process control systems, which analyze the current state of a process and then use feedback to alter experimental variables in such a way that the current state and the desired state are nearly identical,... 

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