Reproducibility automated methods

Liquid-liquid extraction is by far the most popular separation method for the cleanup and preconcentration of samples because it is simple, reproducible, and versatile. There are several ways to achieve these objectives, from the original discontinuous ( batch ) and nonautomatic techniques to continuous separation techniques incorporated with automated methods of analysis. The methodologies can be classified into two general types ... 

Equivalency. This test compares the results of the automated procedure with the results of the validated manual method. If accuracy of the automated procedure has been proven, it may not be necessary to perform the equivalency study. However, if the manual method does not exist, then accuracy and reproducibility data should be used to assess the suitability of the automated method. The recommended testing for content uniformity, assays, degradation and impurity methods and dissolution methods are listed in Table 5.4. 

The validation of an automated content uniformity method and an automated dissolution method based on a validated manual method can adopt a similar approach where the equivalency data can support the requirements of the other studies involved. When validating an automated method that is not based on a validated manual method, only the repeatability and reproducibility can be combined to reduce the amount of analysis to be done since the equivalency study will not be executed. 

The routine measurement of estrone and estradiol by immunoassay techniques has also given rise to the familiar problems of poor sensitivity, cross-reactivity, and poor intermethod reproducibility. Most automated methods cannot measure these steroids in sera of children and men. Development of LC-MS/MS methods has also proven challenging as most investigators have found that estrone and estradiol are poor ionizers and the desired sensitivity has not been achieved. The Mayo group [60] published the LC-MS/MS quantification of estradiol and estrone using dan-syl chloride derivatives (described above) and 2H5 estradiol and 2H4 estrone internal standards. 

A method for the automated analysis of volatile flavor compounds in foods is described. Volatile compounds are removed from the sample and concentrated via the dynamic headspace technique, with subsequent separation and detection by capillary column gas chromatography. With this method, detection limits of low ppb levels are obtainable with good reproducibility. This method has experienced rapid growth in recent years, and is now in routine use in a number of laboratories. 

Automated methods frequently exhibit remarkable performance not only in terms of sample throughput and cost, but in relation to the quality of results, especially in relation to repeatability and reproducibility. Several systems are currently available that enable simple automation of manual gestures these include automatic titra-tors, pH-meters with a circulating cell, etc., and involve approaches that are not fundamentally different to the corresponding manual method. These techniques are not, however, described in this chapter, nor are gas and liquid chromatography and capillary electrophoresis, automated techniques, that may be present but are not routinely used in oenological laboratories. 

This chapter has provided a brief review of approaches relevant to the comprehensive determination of subcellular location. These methods are automated, reproducible and more sensitive than visual examination, and their utility has already been demonstrated in pilot projects. However, much work remains to be done, especially to develop automated methods for synthesizing diverse sources information on subcellular location into accurate models of the distribution of all proteins within all cell types. 

Finally, the automated method should give as good if not better recoveries and precision than the original manual method. Commonly, the automated methods are not as rapid as the manual method. This is because of the serial nature of the automated workstations, whereas manual methods are typically done by vacuum box, which is a batch method. The automated method is superior to manual methods in the area of precision because any repetitive steps of the method are reproducibly delivered and the robot will not make the errors prone to humans. 

Similar to all of the other methods described thus far, SPME affords a certain view of the volatile composition of a food. This view is determined by factors common to headspace techniques as well as the unique affects contributed by the adsorption process. To use the method effectively, one has to be very familiar with the factors that influence volatile recovery. These factors have been discussed in detail in the literature (references cited above). If the method provides an isolate that has the component(s) one wishes to measure and it is adequately reproducible, the method is quite attractive. There are no solvents for contamination it is simple, automated, moderately sensitive and rapid. 

Principles and Characteristics Dynamic headspace sampling (DHS) is a solvent-free, highly reproducible, automated extraction procedure of volatiles from almost any matrix for quantitative and qualitative determinations, which extends the headspace method and uses concentrator technology to achieve highly sensitive detection limits. Table 2.46 summarises the characteristics of concentrator technology using thermal desorption methods. 

Bioreactors have significant clinical potential as they can be used as a method to create automated, standardized, and reproducible culture methods. However, due to incomplete understanding of the role and importance of both biochemical and biomechanical clues, tissue growth in bioreactors has not yet... 

Automated methods for preparation, adhesive application, and bond assembly give the best reproducibility and best control of durability however, such automation is frequently not possible. Manufacturers recommendations in data sheets and on containers should always be followed and particular attention paid to storage conditions, mixing procedures, adhesive or sealant application, and joint assembly. 

The application of FIA and biosensors in environmental analysis is attractive because enzyme biosensors operate on the principle of inhibition. The process is economical because only small quantities of substrate are required and because the incubation, reaction and reactivation times can be controlled. The process can therefore yield high reproducibility. This method has been used to measure insecticide levels in sea water [269], Finally, FIA is particularly suitable for the construction of automated systems. 

An alternative to TBP distillation is simulated distillation by gas chromatography. As described by Green, Schmauch, and Worman [Anal. Chem., 36, 1512 (1965)] and Worman and Green [Anal. Chem., 37, 1620 (1965)], the method is equivalent to a 100-theoretical-plate TBP distillation, is veiy rapid, reproducible, and easily automated, requires only a small microliter sample, and can better... 

Although SFE and SFC share several common features, including the use of a superaitical fluid as the solvent and similar instrumentation, their goals are quite distinct. While SFE is used mainly for the sample preparation step (extraction), SFC is employed to isolate (chr-omatography) individual compounds present in complex samples (11 -15). Both techniques can be used in two different approaches off-line, in which the analytes and the solvent are either vented after analysis (SFC) or collected (SFE), or on-line coupled with a second technique, thus providing a multidimensional approach. Off-line methods are slow and susceptible to solute losses and contamination the on-line coupled system makes possible a deaease in the detection limits, with an improvement in quantification, while the use of valves for automation results in faster and more reproducible analyses (16). The off-line... 

However, many of these tools, while enabling markedly faster and more detailed analysis than paper-based methods, still mimic static, one-by-one paperlike reports with no real-time auditing capability. Moreover, these COTS do not have integrated data analysis and automated data screening capabilities and are not optimized for systematic analyses. Furthermore, the ad hoc analyses that these COTS produce lack interactive, automatic auditing reproducible functions. Thus these tools are often used to produce the same dense, unwieldy paper tables of counts and percentages that were created manually before personal computers became ubiquitous. 

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