Problem: The use of laboratory automation increases productivity and precision, making it attractive for use in the pharmaceutical industry. However, in order to ensure that the automated equipment operates at optimal output, manual input is frequently required. For example, users need to continually monitor the supply and waste levels of solvents in analytical instruments, such as those used for UPLC/MS and HPLC/ MS. This can prove problematic as waste vessels are often located in fume cupboards or below benches, which makes it difficult to quickly and easily determine the solvent quantity remaining. In addition, as supply bottles are often kept closely together in drip trays, it is hard to accurately monitor the solvent levels, particularly in the bottles located at the back of the tray or in bottles made of dark glass. However, failure to effectively regulate the solvent levels could lead to the burnout of columns and unwanted downtime, even if there is only a small amount of solvent within the supply vessels. There is also the possibility of potentially dangerous leakage and blockages if too much solvent is contained within the waste vessels.

Analytical instrumentation can be set to estimate solvent usage. However, this is dependent on users accurately setting the starting levels and resetting the system each time a bottle is changed. Devices such as weighing cells and dip tubes can also measure solvent levels, although these are not ideal. For example, weighing cells need taring after every bottle change and it is not practical to fit six weigh cells in an HPLC/UPLC/MS drip tray due to their size. Dip tubes are useful, but could cause contamination, so require careful cleaning to remove any solvent or bacterial growth. In addition, they need to be resistant to the solvent to ensure they do not cause a reaction, which could also lead to contamination.

Solution: In order to automatically monitor solvent levels during laboratory automation processes, a non-contact sensor would provide the ideal solution to eliminate the risk of contamination, as well as the size and calibration constraints associated with currently-used devices. One example, the aequus from TTP Labtech, simply requires a single preliminary calibration to configure it for use with a given vessel and solvent. aequus’ interface control unit contains 12 sensor inputs and can be used as a bench-mounted device or clipped to the rear of a solvent drip tray. The sensors attach to the vessels using an adjustable Velcro strap or a stainless steel spring clip, making them easy to move and fit onto round or square vessels. Using capacitance-based technology, the sensors work with a wide variety of non-conductive vessels, accurately compensating for vessel material (including glass and plastic) and wall thickness. Utilizing the dielectric property of the solvent, the sensors reliably measure the level of the liquid in the vessel with a resolution of better than 0.5mm. The touch screen display provides local feedback and a display of the current levels in all monitored vessels, including an independent, configurable warning alarm to alert the users if any vessels are running too low, are empty, or are getting full. aequus also incorporates a data logging and graphing facility for detecting leaks or keeping track of those solvents that are only used slowly, or that deteriorate over time. The remote monitoring offered via the software interface allows aequus to be controlled by automation systems or incorporated into inventory systems for solvent procurement and disposal.

By providing an automated non-contact sensor, TTP Labtech’s aequus delivers accurate fluid monitoring without the need for manual input, increasing efficiency and reducing hands-on time

For more information, please visit http://www.ttplabtech.com/aequus/index.html

TTP Labtech’s aequus for automatic monitoring of solvent levels in analytical instrumentation