Small laboratory computer networks

The rational approach to laboratory automation in a changing research environment involves a network of computers. This permits program preparation and data manipulation/storage/plotting/printing to take place on the CPU most appropriate to the task. It also allows the application programs to run on satellite processors with minimum configuration and maximum data throughput capabilities. The hardware implementation is described, as well as a brief introduction to the software facilities available under RT-11/REMOTE and FORTH, the two language systems used at Virginia Polytechnic Institute to implement the net.     

Computer systems for analytical chemistry

Microcomputers are becoming integral parts of all analytical instrumentation and 'personal computers' are invading the laboratory. The analytical chemist is confronted with the question of how to computerize his work and what to request from a computer system. This article attempts to provide some guidelines.     

Sample preparation for high-performance liquid chromatography in the clinical laboratory

Techniques for the preparation of clinical specimens for high-performance liquid chromatography are described. Liquid samples containing high enough concentrations of analytes may be injected directly or after centrifugation. Proteins may be removed by precipitation with organic, anionic or cationic precipitants or by ultrafiltration. Compounds having large partition coefficients may be extracted with an organic solvent. Extraction may also be performed following derivatization, ion-suppression, ion-pairing, salt addition or complex formation. Solid phase extraction may be off-line using disposable cartridges or on-line with an Advanced Automated Sample Processor. The advantages and disadvantages of each method and the trends in sample preparation techniques are discussed.     

Computer system for a small analytical research laboratory

A solution to three problems concerning computer use in our laboratory is described. The problems are: replacement of obsolete computer equipment, consolidation of data processing programs, and unification of the format of kinetic data from different sources. The solution involves use of a central super microcomputer with personal computers used primarily for data acquisition and temporary storage.     

A high-performance multilane microdevice system designed for the DNA forensics laboratory

We report preliminary testing of "GeneTrack", an instrument designed for the specific application of multiplexed short tandem repeat (STR) DNA analysis. The system supports a glass microdevice with 16 lanes of 20 cm effective length and double-T cross injectors. A high-speed galvanometer-scanned four-color detector was specially designed to accommodate the high elution rates on the microdevice. All aspects of the system were carefully matched to practical crime lab requirements for rapid reproducible analysis of crime-scene DNA evidence in conjunction with the United States DNA database (CODIS). Statistically significant studies demonstrate that an absolute, three-sigma, peak accuracy of 0.4-0.9 base pair (bp) can be achieved for the CODIS 13-locus multiplex, utilizing a single channel per sample. Only 0.5 microL of PCR product is needed per lane, a significant reduction in the consumption of costly chemicals in comparison to commercial capillary machines. The instrument is also designed to address problems in temperature-dependent decalibration and environmental sensitivity, which are weaknesses of the commercial capillary machines for the forensics application.     

Computer aided optimization in high-performance liquid chromatography

In reversed-phase liquid chromatography the composition of the mobile phase is the key to a successful separation. Lengthy and uncertain trial and error techniques can be replaced by more efficient computer-guided approaches to find the optimum composition.     

ISO compliant laboratory quality systems and incident monitoring improve the implementation of laboratory information systems

Quality systems can provide a means of measuring the rate of occurrence of defined incidents and non-conformities. We have studied the application of laboratory quality systems to monitoring the implementation of laboratory information systems (LIS) in two similar size tertiary hospital pathology laboratories in Australia. At one site, one department implemented a quality system accredited to ISO 9001–1987 and ISO 9001–1994 while the rest of the organisation did not have a formal quality system; this site implemented the Cerner PathNet LIS. At the other site, the organisation was in the process of implementing ISO/IEC Guide 25–1990 and ISO/IEC 17025–1999; this site implemented the PJACC AUSLAB LIS. The rate of quality system incidents and non-conformities was used to track the progress of implementation of the LIS. We found that different quality systems appeared equally useful in monitoring the rate of occurrence of incidents. However, the presence of a formal quality system greatly improved the proportion of incidents that could be investigated and resolved at root cause level. Incident monitoring, as part of a formal quality system, proved to be a useful tool in monitoring and managing the implementation of these LIS. Received: 4 August 2001 Accepted: 21 March 2002     

NMR of tracer molecules in networks

Liquid NMR techniques were used to elucidate the molecular organization and dynamics of poly[tetra(ethylene glycol)dimethacrylate] and poly[tetra(ethylene glycol)diacrylate] as a function of cure. The change in line width of the monomer was used to determine the extent of cure and indicate the mobility in the polymer matrix. Line widths of different parts of the monomer peaks broadened at different extents of cure. Non-reacting tracer molecules (dimethylsulphoxide, methyl acetate, decalin, cyclohexane and dodecane) were also introduced into the curing system at low concentrations and their line widths observed. It was found that they broadened at differing rates and persisted well into the later stages of the cure when the monomer peaks had broadened into the baseline. In typical cures the monomer peaks broadened simply but, in atypical cases, the line shapes showed that there were two monomer domains one constrained and the other unconstrained. All tracers became constrained with increasing cure, except dodecane. The line shape of pure monomer was also followed as a function of temperature and found to broaden in similar fashion to the monomer during a typical cure.     

Practical techniques for feedback and control of laboratory automation systems

Summary Sample preparation has been the weak link in chemical analysis. The preparation step has been time-consuming, expensive, and a major source of errors. Laboratory robotics has become a popular alternative to preparing samples manually. Many users are getting better analytical results — faster, safer, and at less cost than before. The industry recognizes the importance of reducing human exposure to a wide range of chemicals and biologically active materials, while isolating sensitive procedures from human contamination. Automated sample preparation systems normally run unattended. While increasing productivity, unattended operation creates situations that must be accommodated if the system is to run reliably. The modern robotic system uses both feedback and feedforward techniques to assure reliable operation. Feedforward is used to confirm that the operation is possible. The heart of feedforward control is the system image. The system image consists of a set of data variables for every possible container, or tube, position in the system. The usual variables are container volume and capped status. Tube tare and net weights can also be tracked. As the containers move and volumes change, the stored image is kept updated. In the example of removing a tube from a rack, the computer program can compare the intended operation with a stored record, or image, of the system before the action starts. In this example, it would confirm that the robot's hand is empty and that there is a tube in the target location. Feedback is used to confirm that an operation was performed as expected. Feedback control relies mostly on robotic tactile sensing and position sensing switches in associated mechanisms. It is important for the laboratory robot to be able to sense the force with which it is pushing in all of its axes, not just the grip. For example, after the robot has removed a test tube from a rack, the force exerted by the gripper mechanism can be used to confirm that there is a tube in the fingers and that the operation was successful. Additionally, laboratory balances are used to gravimetrically confirm transfers. Weight confirmation is important with other automated preparation steps such as membrane filtration, solid-phase extraction, and evaporation where the final sample amount may be in question.     

NMR chromatography using microemulsion systems

NMR spectroscopy is an excellent tool for structural analysis of pure compounds. However, for mixtures, it performs poorly because of overlapping signals. Diffusion ordered NMR spectroscopy (DOSY) can be used to separate the spectra of compounds with widely differing molecular weights, but the separation is usually insufficient. NMR "chromatographic" methods have been developed to increase the diffusion separation but these usually introduced solids into the NMR sample that reduce resolution. Using nanostructured dispersed media, such as microemulsions, eliminates the need for suspensions of solids and brings NMR chromatography into the mainstream of NMR analytical techniques. DOSY was used in this study to resolve spectra of mixtures with no increase in line-width as compared to regular solutions. Components of a mixture are differentially dissolved into the separate phases of the microemulsions. Several examples of previously reported microemulsions and those specifically developed for this purpose were used here. These include a fully dilutable microemulsion, a fluorinated microemulsion, and a fully deuterated microemulsion. Log(diffusion) difference enhancements of up to 1.7 orders of magnitude were observed for compounds that have similar diffusion rates in conventional solvents. Examples of commercial pharmaceutical drugs were also analyzed via this new technique, and the spectra of up to six components were resolved from one sample.     

Optimization of chromatographic systems for the high-performance thin-layer chromatography of flavonoids

Summary To characterize the retention and selectivity of separations of 23 flavonoids (aglycones and glycosides) relationships betweenR _F and modifier concentration were determined for silica and diol adsorbents (with mixtures of ethyl acetate and methanol as mobile phases), for cyanopropyl silica (with mixtures of ethyl acetate and dichloromethane as mobile phases), for aminopropyl silica (with mixtures of ethyl acetate, methanol and water as mobile phases) and for octadecyl silica (with mixtures of methanol and water as mobile phases). Owing to large polarity differences between aglycones and glycosides, these groups of compounds cannot be separated other than by use of reversed-phase systems, for which the selectivity is lower. It follows from correlation plots ofR _F1 againstR _F2 that for some pairs of adsorbents (e. g. silica and diol) selectivity differences are small; for others the points in the plot are widely dispersed, indicating selectivity differences. The chemometric database obtained can be used to choose optimum chromatographic systems for the separation of given sets of flavonoids and for planning gradient elution programs for separation of flavonoid aglycones and glycosides in a single TLC experiment.     

Shapeable carbon fiber networks with hierarchical porous structure for high-performance Zn-I2 batteries

Aqueous rechargeable zinc-iodine batteries(ZIBs)emerging as a promising energy storage alternative have attracted con-siderable attention.However,ZIBs still suf...     

Reversed-phase systems for the separation of pentapeptides by high-performance liquid chromatography

Summary Reversed-phase systems using octyl modified silica as such and as a support for dynamically coated ion-exchangers, were investigated for their ability to separate pentapeptides. Normal reversed-phase adsorption with C-8 bonded silica in combination with citrate bufferpropanol-1 mixtures were found useful for the separation of a number of pentapeptides. The separation of pentapeptides differing widely in retention can be speeded up by applying an organic modifier and/or sodium citrate gradient. A solvent generated cation-exchange system with sodium dodecylsulfate as surfactant showed a high selectivity for the pentapeptides under investigation and is better for analytical purposes than the normal reversed-phase adsorption systems investigated. With respect to the detection of pentapeptides with fluorescamine, the use of dry pyridine as a basic buffer and as diluent for the fluorescamine was also investigated. Compared to the commonly used diluent acetone, pyridine is better when using acidic eluents of moderate buffer strength. At pH>6 no significant differences in sensitivity between acetone and pyridine could be noticed.     

Computer simulations of two-dimensional trifunctional bimodal networks

Transformation of mean chain dimensions in a bimodal Gaussian network is analyzed by generating a two-dimensional trifunctional network using Monte Carlo technique and deforming it, subject to the balance of mean forces at each junction. Instantaneous fluctuations in chain dimensions are not considered in the simulations. The problem is, therefore, equivalent to the analysis of a two-dimensional deterministic system of two sets, short and long, of linear springs, joined at trifunctional junctions. The molecular deformation of network chains, the distribution of orientation of chain vectors and the reduced stresses are studied as a function of extension ratio and network topology.     

Computer models for electrical conductivity of multicomponent solid-state systems

Models for the computer simulation of electrical conductivity of polycrystalline materials and mixtures are proposed. The effect of model parameters on the concentration behavior of conductivity is considered. The correspondence between the model parameters and the characteristics of physical objects is established, thus making it possible to analyze the spatial relations in solid-state systems.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1868–1873, November, 1993.