Volumetric Flask Filling

Eye-Lab

EYE-LAB is an automatic system for precision volume filling of class A/AS/KB/USP volumetric flasks.
This instrument is the result of a Steroglass patent, and there is nothing else like it on the market.

It is designed to automatize and to make as accurate and reproducible as possible the preparation of standard solutions at given concentrations and titers, eliminating any risk of error by the operator.

Filling a volumetric flask up to the mark with a solution may appear to be a very simple operation for a chemist; however, one seldom considers the possible consequences that some common procedural errors may have on experimental analytic data. It is easy to make mistakes, such as those due to parallax error – the most common – or overfilling (above the calibrated mark), the use of nonstandard flasks (not class A), the risk of contaminating solutions with wash bottles and pipettes that have not been properly cleaned. One bad habit of many lab technicians – and not just those who are inexperienced – is that of disregarding the temperature when filling with liquids in solution.

Volumetric flasks are calibrated at 20°C, and therefore the total quantitative reproducibility of volumes is guaranteed only when the solvent being introduced is at this exact temperature. Otherwise, even with temperatures differing by an apparently negligible amount, experimental error can greatly affect the quality of the analytic data, especially at temperatures greater than room temperature.

The results of a recent statistical survey conducted by Steroglass at a large number of analysis laboratories all over Italy show that 80% of experimental data errors stem from the improper initial preparation of the sample.

The EYE-LAB works with the assistance of an optical sensor, a real “eye” that substitutes the human eye.

OPERATION:

The optical sensor, which is placed along the walls of the dispensing chamber, slides on a movable track, each time adjusting the height of its “eye” to that of the volumetric flask to be filled to the mark. The flask is secured to the base of the chamber with an automatic centering device, similar to the type used by opticians.
The sensor’s “eye” sees the images of the calibration mark and the meniscus in an enlarged form, thus avoiding any parallax error.

The filling is done using a special nozzle in PEEK (connected to the solvent storage container), which has a central opening as well as three small outer holes, from which the solvent can be sprayed in a “shower” for cleaning the neck of the flask. The solution is dispensed rapidly up to the neck of the volumetric or Erlenmeyer flask; filling then proceeds slowly as it nears the calibration mark, stopping when the mark is reached.

Eye-Lab can be made to operate without any specific methodological setting, or optimizing times and procedures. In the latter case, a number of functions are available:

- calibration of the pump to class A volumetric flasks;
- cleaning of the neck of the volumetric flask during filling;
- calculation of the dead volume (volume of solution already present in the flask, introduced to “rinse” it or to dissolve the various components): this function makes it possible to optimize the filling time; selection of the solvent type (for dark solvents, the optical sensor must measure the level of the liquid instead of its meniscus);
- filling speed;
- flask counter: for filling a series of flasks;
- “custom flask,” for special flask types (up to 5 different types of nonstandard flasks can be memorized) ;
- choice of methods: the operator can enter in the instrument’s memory up to 30 different filling methods (e.g. for viscous liquids, hydrophobic surfactants and frothers, etc.).

Eye-Lab can also work as a precision dispenser (by setting the volume of solvent to be dispensed) and, consequently, as a volumetric flask calibration instrument.

THERMOSTATTING

The 10-liter container for storing the solvent to be dispensed can be thermostatted at 20°C or at any other temperature.

It is made from chemically inert materials, such as borosilicate glass, PTFE, or PEEK, according to the type of solvent used in the preparation of solutions.
It has a quick-release flange, central GL threaded cap with double inlet and outlet connector, and a glass suction tube for connection to the Eye-Lab pump.
A high-efficiency glass (or PTFE or PEEK) coil is inserted into the container and remains immersed in the stored liquid.
By circulating coolant through the coil (cooled by a Cryochiller or an ordinary external circulation cryostat), it is brought to the controlled constant temperature of 20°C, ready to be dispensed into the volumetric flask, guaranteeing the greatest possible volumetric filling precision. The container also has a Teflon tap so that it can be used occasionally for drawing off volumes of water for general laboratory use.

The PUMP - SPEEDEX

The pump is a dual reciprocating piston type (similar to those in HPLC systems, but operating at very low pressures) and is self-priming.
It has a maximum flow of 1,5 liters/min., optimizing the filling of 2-liter capacity volumetric flasks, and a minimum flow of 25 ml/min., for the smallest volumetric flasks. This means that for small volumes the system must be capable of dispensing solvent amounts as small as 40 microliters; the precision of the absolute volume dispensed is guaranteed by the stepper motor installed in the pump: each step corresponds to an aliquot of 40 microliters.
The internal parts in contact with the liquid are chemically inert. The pump is contained in a rectangular housing, above which the 10-liter storage container can be set, completed by a small working surface in washable material. However, if lab space is limited, the pump can be placed beneath instrument, which has a sealed bottom.

FUTURE PROSPECTS

A number of additions to the standard Eye-Lab setup are already being designed. In order to meet the needs of high-production laboratories, a sample tunnel is to be added at the back of the instrument, connected with the inside of the dispensing chamber: in this way it will be possible to fill automatically a series of several volumetric flasks.
In addition, the Eye-Lab pump is designed to act also as a stand-alone dispensing device, to be added to the range of Steroglass instruments now available on the market.