MOSS ® Automated Liquid Handling and Weighing Platform

Automated Assay Plate Preparation System for Compound Management


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The MOSS performs computer-guided compound weighing and subsequent liquid dilution to achieve target concentrations; designed for preparation of plates from compound libraries. It is an ideal tool to work in conjunction with a pharmaceutical compound library for both front-end (sample loading into the library) and back-end (plate replication for assay plates) processes.


The Moss is now available with argon flooding. Even a trace of water in DMSO greatly decreases compound solubility and integrity, therefore to minimize the risk of compound precipitation the entire dissolution step and sample distribution can be performed under argon. With this new technology it is not necessary to flood the entire system with argon within a specialized enclosure thus keeping cost, space requirements and weight to a minimum. The system also features a new tilting mechanism to allow complete retrieval of sample material. The system is capable of dissolving and distributing 384 samples to up 6 destination racks in approximately 90 minutes with parallel processing.

MOSS is now available on our new workbench with two arms. Due to technological development MOSS is a much faster system than its predecessor. The system is equipped with up to eight probes and a 350° rotating gripper. The platform is made of stainless steel.

With MOSS, the Modular Sample Preparation System, ZINSSER ANALYTIC has bridged the gap between huge library stores of hundreds of thousands of library compounds, and High Throughput Screening laboratories. It ergonomically combines modern weighing technology and sophisticated software to automate assay and storage plate preparation. The compact design, its high throughput, reliability and its easy integration into existing laboratory infrastructures has made it the system of choice for high throughput testing laboratories.

Weighing-in of Compounds

As many of the library compounds cannot be weighed automatically (unknown physical properties, crystals, jellies, oils, static charged powders etc.) computer assisted manual weighing has been developed for MOSS. Up to 3 Sartorius Genius balances are normally linked to a MOSS system (number of balances is unlimited). The Genius balance combines outstanding weighing comfort and high precision. The doors open automatically, it provides ionized air to cope with electrostatic charge, and tares very quickly. The tedious work of manually weighing compounds is relieved by special software MossWEIGH, which helps the operator at the balance to weigh the compounds as fast as possible.

The MossWEIGH software guides the operator through the weighing process. The screen shows the grid of the dissolving rack as an array rack. This grid can be freely configured (i. e. from 1 x 1 to 8 to 12 positions). By reading the barcode of the compound bottle, the molecular weight, the minimum weight (or target weight, which has to be filled into to the dissolution vial), and additional information about the compound (internal code, chemical description etc.) appears on the screen. A progress bar helps the operator to speed up the weighing procedure. When the target weight is reached (or within the preset tolerances target weight + x%), it will be automatically accepted and all data is stored in the database. The operator can proceed with the next compound until the whole rack has been completed.

Dissolving the compounds in DMSO or other suitable solvents

The compound rack sits tightly on the built-in vortexer. As an option sonication can be implemented either by a pick-up probe or an ultrasonic bath. After barcode identification of the dissolving tubes or vials an individually calculated volume of solvent(s), in relation to the final concentration, the registered weight, and molecular weight of each sample is (are) delivered by the 8 independently spacing probes into the vials. A stock solution with an equal concentration (i. e. 10µM or 100µM) of each compound is prepared. After that MOSS automatically starts the vortexing for thorough and reliable dissolution. The vortex time and speed are software controlled. An optional "High Flow"-6-way valve can provide up to six different solvents .The tubes are stored in special vortexing racks. Not only do these racks allow the samples to be thoroughly mixed by vortexing, they also can be flooded with argon to help preserve sample integrity. After liquid handling actions are performed, the robot will automatically put a lid on the vortexer box and the box will be flooded with argon and kept is a sealed environment. Two of these vortexers are shown here, the one on the left already has the lid in place from the robot.

Sample distribution of the dissolved compounds

The dissolved compounds can be distributed into any format of final plates or racks (384-, 96-, 48-well microplates or tube racks with any number of rows and columns). Efficient washing of the probes avoids cross contamination. To exclude any potential cross contamination, all pipetting steps for the mother- or assay plate preparation can be carried out with disposable tips (optional). Two tip sizes, 250 µl and 1.1 ml, are available. Simultaneously working with 8 independently spacing pipetting probes is extremely fast. It copes with any kind of rack configuration (even & uneven numbers of rows and columns).

WinMOSS Software

The WinMOSS software is specially designed for the application of sample preparation in the compound library environment. MOSS keeps its own database. The compound data will be downloaded from any compound database such as ORACLE®, ISIS® etc. When the mother or assay plates are finished the actual data (plate number, compound position, compound number etc.) will be uploaded to the main database. The screen shows the user the layout of the workbench with all racks in position. Color changes in the wells or vials indicate the current liquid handling steps. The software provides a complete audit trail of the process. Each step is flagged with the actual time of its completion. In case of an interruption (power failure) the system can be restarted without loss of sample.

System Configuration

2 arm liquid handling platform
Arm 1:
8-channel pipetting system
8 high precision delivery pumps (0.50ml /sec) with ultra low dead volume and high speed
8 solvent resistant probes with independent flexible spacing (min 8mm, max 340mm distance tip to tip)
Arm 2:
Integrated handler pay load max. 3.0kg
Motor controlled gripper rotates up to 350°
Tip wash station
Capacitive level detection on each tip
Custom made vortex rack
Source rack for dissolution vials made to customer specification
3 Plate adapters for 5 96-well plates each
Active wash station for 8 probes
Integrated heavy-duty vortexer, self indexing, software controlled (up to 800 rpm)
2-D barcode reader for plates, vials, tubes and micro tubes (Micronics, Matrix)
1 Sartorius Genius 5-digit automatic balance with N.I.C.E. "Integrated Neutralization by Ionic Charge Elimination"-system
1 Handheld barcode reader


Disposable tips 250 µl or 1.1 ml tip
Rack for disposable tips
High-Flow precision pumps
1,5ml / sec.
High-Chem precision syringe pumps
for 100, 250, 500µl, 1, 2.5, 5 ml syringes
for piercing of micro tubes
Micro-tube gripper tool
to transport and read barcodes on micro tubes
Movable plate stacker
for 10 shallow- or 3 deepwell plates
Argon chamber chamber
to flood the destination rack area with argon (or nitrogen).

Technical data

Power: 85 to 264 V AC, 50-60 Hertz, 350 Watts
Overall dimensions:
with micropumps
1000 x 730 x 550 mm (WxDxH)
(H=870 mm when all needles are lifted)
1500 x 730 x 550 mm (WxDxH) optional
2000 x 730 x 550 mm (WxDxH) optional
with syringe pumps
1000 x 790 x 550 mm (WxDxH)
1500 x 790 x 550 mm (WxDxH) optional
2000 x 790 x 550 mm (WxDxH) optional
160 Kg