Automated pipette

Microlab AT automated pipetter diluter/distributor for microplates Hamilton Bonaduz AG PO Box 26 CH-7402 Bonaduz Switzerland... 

At the end of the selected number of sample analysis cycles, one analysis of the standard is performed. The system then either terminates work or repeats the entire sequence at the discretion of the operator. The interval between analyses is under program control and may vary from 2 min to 1 hr. A provision for making standard additions under program control has also been made, but as of this writing the automated pipette has not been installed, and standard additions were made with a handheld micropipette. Details of the programmer system and wiring diagrams are available upon request. 

A Unal example of direct bioanalysis was recently published by Dethy et al. and involves the appUcation of infusion nanoelectrospray (nano-ESI) from a silicon chip [110]. In this example, supernatant obtained from protein precipitation was directly infused with an automated pipette-tip delivery system. Individual, conductive pipette tips that contain sample were sequentially introduced to the backplane of a silicon chip for analysis. The front plane of the chip that consisted of 100 individual nano-ESI nozzles, was positioned near the API orifice of a TQMS for direct serial analysis. Quantitation of verapamil and its metaboUte norverapamil occurred in human plasma over a range of 5-1000 ng/mL. It is possible to achieve analysis times of less than 1 minute per sample with this technology. An important advantage, demonstrated by this work, is the unique abiUty to avoid system carryover with this device [110]. 

Most of the research and development for droplet-based Lab-on-a-Chip technology has focused on methods of manipulating the droplets that also enable steps of sample preparation to be performed before the bio-/chemical analysis. There are, however, examples of droplet-based analysis systems for high-throughput biochemical analysis that use automated pipette-based or other dispensing systems which are completed... 

Sanq>ling With Capillaries. Earlier it was pointed out that with the aid of a constriction pipette a sample can be measured accurately. A similar effect can be obtained by allows ing the serum to enter a capillary open at both ends. The serum will reach the opposite end of the capillary if it is held at an angle and then stoppered, and if the capillary has been carefully calibrated an accurate volume can be measured out. Such capillaries are now available commercially, and have been in use in automated equipment in the authors laboratory for at least 10 years. It is now possible to take the capillary and empty its contents into a container for analysis, or into a stream for the purpose of determining any of the materials which can be determined with the autoanalyzer. Figure 33 shows an instrument which is used for this purpose (58). 

Directed evolution relies on the analysis of large numbers of clones to enable the discovery of rare variants with unproved function. In order to analyze these large libraries, methods of screening or selection have been developed, many of which use specialized equipment or automation. These range from the use of multichannel pipettes, all the way up to robotics, depending on the level of investment [59]. Specialized robotic systems are available to perform tasks such as colony picking, cell culture, protein purification, and cell-based assays. 

Syringe-barrel cartridges, disk-holders, plastic pipette-tips, well plates vacuum manifolds for semiautomatic batch processing fully automated autosamplers, xyz liquid handlers and robot-controlled work stations. 

These authors reported greatly improved sample transfer without pipette failure due to plugging caused by thrombin clot formation when a LEAP HTS PAL autosampler was used for liquid transfer automation. 

Suspensions can be introduced in a variety of ways. Some examples are to manually use syringes or pipettes, pour from a fared beaker, or automate delivery using calibrated pipettes. Each method has its own set of limitations, although automated methods may show less variability. Mixing of the suspension sample will generate air bubbles therefore, the mixing time of suspension samples must be strictly uniform to reduce erroneous or biased results. 

Information on particle size may be obtained from the sedimentation of particles in dilute suspensions. The use of pipette techniques can be rather tedious and care is required to ensure that measurements are sufficiently precise. Instruments such as X-ray or photo-sedimentometers serve to automate this method in a non-intrusive manner. The attenuation of a narrow collimated beam of radiation passing horizontally through a sample of suspension is related to the mass of solid material in the path of the beam. This attenuation can be monitored at a fixed height in the suspension, or can be monitored as the beam is raised at a known rate. This latter procedure serves to reduce the time required to obtain sufficient data from which the particle size distribution may be calculated. This technique is limited to the analysis of particles whose settling behaviour follows Stokes law, as discussed in Section 3.3.4, and to conditions where any diffusive motion of particles is negligible. 

A comparison of automated pipetting with manual pipetting, by Weltz [16]. demonstrates a difference of approximately one order of magnitude 0.4% RSD for automatic sample introduction versus 3.2% RSD for manual sample introduction. To achieve optimum results for trace elements in biological materials, the use of dedicated automated samplers is recommended. The Hquid-handhng capabihties of a pipetter/diluter workstation have been evaluated at Ortho Pharmaceutical (Haller et al. [17]). Four different volumes of each of three solvents were dispensed 20 times. Actual volumes... 

For higher throughput applications, injection-molded plastic microtiter plates have served as the formats of choice for automated assay development. Thermoplastics such as polystyrene, polycarbonate, and polypropylene are used for a variety of purposes including storage and assay plates, lids, pipette tips, and Eppendorf PCR tubes. Polystyrene plates are used for cell culture and ELISAs. Polycarbonate reagent bottles are popular, while polypropylene storage plates and PCR tubes are standards. 

Optional automated hand held pipette Light microscope... 

When large sample volumes need to be analyzed, automation of the sample preparation should be considered by using pipette robots and a 96-well plate format as opposed to single vials. 

The type of pipette used for addition or transferring of solvents is another issue of importance. Automated micro- or macropipettes in the volume range of... 

Preparation of the reaction solutions in the deep wells (2.2 mL) of microtiter plates (96-format) is automated by using a pipette robot. Pipette scripts (Gemini software) are used for robotically filling the wells with buffer and substrate solutions (see Section 9.3.1.1). To activate all the modules of the robot, Facts software is used. The pipette robot consists of a workstation with spaces for 12 microtiter plates, a robot arm for transport, a carrousel for storing the reaction plates, and a 96-fold pipette module (Figure 9.3). 

Some techniques are known to provide higher variability than others. The choice of an appropriate method at the outset can improve precision. For example, a volume of less than 20 mL can be measured more accurately and precisely with a syringe than with a pipette. Large volumes are amenable to precise handling but result in dilution that lowers sensitivity. The goal should be to choose a combination of sample preparation and analytical instrumentation that reduces both the number of sample preparative steps and the RSD. Automated techniques with less manual handling tend to have higher precision. 

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