Robotic liquid handlers

Automation using a robotic liquid handling system eliminated most of the tedious steps encountered with traditional manual extraction procedures. Automated 96-well SPE and LLE techniques using robotic liquid handlers have been successfully implemented to support high-throughput bioanalysis.5... 

Enrichment of high affinity candidates is usually achieved in 8 to 15 rounds of SELEX. Each rotmd takes approximately 2 days to perform. The process has been automated using robotic liquid handlers both for DNA (SomaLogic) and RNA aptamers (Cox, 2002). Next, the sequenced aptamer is prepared in bulk by conventional DNA synthesis chemistry and purified, then the aptamer arrayed onto a solid support. Thus, an aptamer is ready for application within 2 to 3 mo. Because the sequence is known, preparation of additional aptamer is easily accomplished using conventional oligonucleotide chemical synthesis. 

The aliquots of the solution-state chemical synthesis samples were directly injected into a standard HPLC-NMR probe by using a robotic liquid handler. The NMR software was used to automatically find and suppress the intense NMR signals from any non-deuterated solvents used, typically using the WET sequence [5]. Unlike the characterisation of impurities in organic compounds (see the next section) or drug metabolites (see the appropriate chapter in this volume) where the proportions of the analytes can be very different, combinatorial chemistry samples tend to be all of similar quantity and this simplifies the analysis in that it is not usually necessary to worry overly about carry-over of material from sample to sample, nor it is necessary to readjust the NMR spectrometer receiver gain after every sample, thus saving considerable machine time. 

Managing a large number of individual reactions can be cumbersome. Reactions are often automated with a robotic liquid handler to minimize the tedium. The liquid handler does exactly what its name implies it dispenses solutions of reagents into racks of wells. Multiple racks are placed on the deck of the liquid handler. Some racks hold wells for reactions, and other racks hold solvents or solutions of reagents. The positions of all the reaction wells and solutions are programmed into a computer. The computer then directs a robotic arm. The robotic arm is suspended over the deck where it takes up and dispenses solvents and reagents as needed. 

Which robotic liquid handlers can dispense live cells ... 

Protein preeipitation was automated into a 96-well plate format by means of a robotic liquid handler by Watt et al. [22]. Plasma samples (50 pi) were transferred from a 96-rack of tubes to a 96-well plate by means of a single-dispense tool. Acetonitrile (200 pi) was added to the wells by means of an 8-ohannel tool. The plate was removed, heat sealed, vortex-mixed for 20 s, and eentrifuged (2000g for 15 min). Using the 8 ehannel tool, the supernatant was transferred to a elean plate, to which first 50 pi of a 25 mmol/1 ammonium formate buffer solution was added. The plate is then removed, heat-sealed, vortex-mixed, and transferred to the autosampler for LC-MS analysis. The proeedure takes 2 hr per plate. A fourfold improvement in sample throughput on the LC-MS instrument was achieved, compared to previous manual protein precipitation procedures. 

In order to study plasma protein binding of drag candidates, a 96-well plate ultrafiltration device was used in combination with fast LC-MS [99]. All liquid handling was done using a robotic liquid handler. After preparation, the plates were centrifuged at 3000g for 45 min. 

Protein precipitation was automated into a 96-well plate format by means a robotic liquid handler by Watt et al. [101]. The procedure is described in more detail in Ch. 1.5.1. It enabled a 4-fold improvement in sample throughput on the LC-MS instrument, compared to previous manual protein precipitation procedures. The method was applied as a generic sample pretreatment method in combination with a generic LC-MS method to a variety of drug candidates [102]. 

Zweigenbaum et al. [104] developed a method to analyse 1152 urine samples for 5 benzodiazepines and an ANIS within 12 hr. LLE in 96-well plate format using a Tomtec Quadra robotic liquid handler was performed prior to LC on a 15x2 1-mm-ID Ci8 column (3 pm) with 33% acetonitrile in water as mobile phase at 1 ml/min, which is about threefold the optimum flow-rate. ESl-MS was performed in SRM mode. Due to speed limitations of the autosampler used, four autosamplers had to be used in parallel to perform analyte injection. The overall cycle time between injection was 37 s. 

In order to increase throughput, the traditional shake-flask methodology has been transferred onto 96-well plate technology and the sample preparation is carried out using a robotic liquid handler. After equilibration of the solute in... 

For small samples (<1 mL) and small channel volumes, the liquid delivery precision of peristaltic pumps is not adequate and membrane extraction equipment based on syringe pumps connected to robotic liquid handlers can be applied. A typical example is shown in Figure 13.8c. Here, a robotic needle connected to a syringe pump submits reagent to adjust the pH of samples in the vials, picks up an aliquot, and passes it through the donor channel of a small membrane unit (channel volume around 10 pL). The entire extract collected in the... 

Figure 7.16. Schematic illustration of the automated flow-through setup for multiple-sample NMR analysis using a robotic liquid handler, which is controlled by a PC computer and able to communieate with the NMR spectrometer.

One distinctive advantage for SLE over the more traditional LLE is its ease of automation and parallel processing. Diatomaceous earth can be packed into a 96-deep-well filter plate.The plate is frozen to prevent leaking during the transfer.The eluent was directly collected to a 96-well microtiter plate. With the help of robotic liquid handlers, the SLE process can be automated with a throughput of four plates per hour. Since the aqueous phase is immobilized on the cartridge, any water-immiscible organic solvent can... 

The Tom tec Quadra 96 liquid handler can be replaced with another robotic liquid handler with 96-, 12-, or 8-channels. Each aspiration step by the Quadra 96 is generally proceeded by 50 iiL of air gap to aid in complete and accurate dispensing. 

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