How an Automated Sample Prep Workstation Works
Problem: With unrelenting need for accurate sample analysis at lower and lower detection limits, there is pressure on modern laboratories for sample prep instruments that can provide automated, accurate reagent additions to previously prepared liquid samples or for preparing several aliquots of these samples with multiple dilution factors. The catch-all phrase that identifies these devices is “liquid handling systems” and they perform absolutely essential tasks that have a direct and large effect on the ultimate measurement accuracy of both inorganic and organic sample analysis.
Among the instrument types currently popular in laboratories are pipettes with or without syringe pump locomotion, and autosamplers with syringe pump attachments. Both of these, although finessed and refined over time, suffer from many key disadvantages. Pipette systems, for one, are essentially manual devices that need a human operator to accomplish the task. These are available in a variety of sophistications and can independently pick up a specified volume of the sample from a sample tube and the diluent from a separate source and deliver the two into a fresh tube as a diluted sample, albeit all with help from human hands.
Autosampler systems with accessory syringe pump attachments also have their own unique issues. The units in this category surveyed were made of painted sheet metal, which, at the ppt level detection limits sought by lab analysts, do pose ambient metal contamination. Further, while these systems are able to accurately deliver specific volumes of liquid directly into the sample tubes, they are not able to pick up measured sample aliquots from originating sample tubes and accurately dilute them before depositing into new tubes. Lastly, the software packages that drive these systems are cumbersome and rigid, being able to perform very limited and regimented operations.
Questron’s QPrep Automated Workstation.Solution: The first area of improvement for a welldesigned, automated, computer driven liquid handling system is its construction. It could be constructed from inert materials, at least in the environs of the work area where sample tubes are located. To further improve on the ambient conditions, the system could be placed in an enclosure with properly engineered air flow path through HEPA filters, providing clean room conditions where risk of sample contamination from surroundings is minimized.
Secondly, careful attention must be paid to the liquid locomotion mechanism that permits reagent dispensing and dilutions. It must be designed so that sample aliquots can be picked up, diluting solutions deposited, and, most importantly, the aptly diluted aliquots transferred to new sample tubes. All this must happen under the watchful ability of a well-designed and integrated software package with which the user can easily configure the system building-blocks, and subsequently run tasks using batchoriented operation files.
Questron’s QPrep Automated Workstation is one example of a versatile liquid handling system that easily conforms to reagent dispensing and dilution oriented operations. As the needs require, the entire chassis is made from plastic welded, inert material sheets that are machined to required shapes. Aside for some unavoidable metal parts, such as motors, electronics boards and wiring interconnections, the entire hardware is inert. Furthermore, great care is taken to cover all exposed metal parts with plastic cladding, and no metallic components are present in the system work area. For applications requiring ultimate clean room air conditions, the entire unit can be placed in a Questron-supplied HEPA filtered enclosure.
QPrep reagent and sample transfers are made under the precise delivery of a custom-designed syringe pump assembly, being able to obtain day-to-day working accuracy of 0.03 ml. The carefully integrated design of system software ensures easily-created batch files that can perform reagent dispensing into sample tubes or aspirating specified volume of sample aliquots, diluting them, and delivering the contents into fresh tubes. A two-stage wash station that is designed to provide fast probe cleanings is also part of the package.
Lastly, the system is designed from the ground up to work with various standard or custom sample tube racks. One can even combine multiple rack types by virtue of custom-made rack positioning plates that accommodate the exact rack requirements of the user.
For more information, please visit www.QTECHCORP.com or call 905-363-1223, x 112