Files in this item
|(no description provided)|
|Title:||Automated Analysis by Stopped-Flow Methodology|
|Author(s):||Walczak, Kenneth Michael|
|Department / Program:||Chemistry|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||Extensions to the stopped-flow analyzer have been developed that demonstrate capabilities which offer the stopped-flow method as an attractive alternative for dedicated chemical analysis. The instrumentation has been designed to expand the versatility of the stopped-flow method, exploiting its desirable characteristics while employing relatively simple and inexpensive equipment. The extensions include the addition of a microcomputer to perform control and data manipulation functions, the introduction of the storage loop to improve throughput speed and as a medium for further solution manipulations, and the inclusion of an additional reagent channel to simplify analytical methodologies. The stopped-flow analyzers are evaluated against a background relating to parameters which are important when considering dedicated automatic chemical analysis.
Microcomputer control enables the analyzers to be operated in several modes by incorporating various software packages. Investigative software eases the development stage of analytical methodology while a software package for dedicated analysis provides for virtually unattended analysis of large numbers of samples, with sample concentrations printed after being calculated from a calibration curve. The stopped-flow instrumentation and hardware has been designed throughout to maintain simplicity and to keep the total system cost relatively inexpensive.
In the stopped-flow method, the reagent and sample aliquots are delivered in precise ratios and turbulently mixed, resulting in high precisions on the order of one-tenth percent for measuring concentrations of reaction products. This inherent advantage, along with the frugal design of these analyzers results in automated systems that can be competitive with continuous flow analyzers for dedicated chemical analysis and outperforms them in many important parameters. The instrumental modifications presented enable the stopped-flow technique to maintain a high sample throughput with a wide range of chemistries that previously required a delay before measurements began on the observation cell. Examples are given that demonstrate the basic stopped-flow, with or without the addition of simple improvements, can accommodate many procedures usually done by either segmented or unsegmented continuous- flow methods.
A method for the analysis of chloride is used to show the simple adaptation of a continuous-flow method. The adaptation results in a greatly increased sample throughput with only a slightly larger reagent consumption. In addition to these advantages, the precision of the measurements is significantly improved.
A solution-storage technique is introduced to improve the sample throughput of the stopped-flow analyzer. The stopped-flow/ unsegmented storage analyzer is shown to be a valuable, yet simple, addition to stopped-flow instrumentation that improves the throughput of automated methods while retaining the measurement advantages of the regular stopped-flow analyzer. This system can accommodate equilibrium, single-point reaction-rate methods, and multi-point reaction-rate methods.
The versatility of the regular stopped-flow analyzer is increased with the addition of another reagent channel to the analyzer. An additional syringe and valve system clamped to the original system provides for the automatic addition of a third reagent, eliminating a manual step for many methods. The reaction-rate method for the determination of phosphorus is used to demonstrate the performance of this system.
The determination of nitrate using a stopped-flow analyzer equipped with a reduction column is also demonstrated. This augmentation of the stopped-flow technique shows the ability to expand the technique into manipulations previously the domain of continuous- flow analyzers. The reduction column is incorporated into an automated system for the determination of nitrate.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1981.
|Date Available in IDEALS:||2014-12-13|