The Technology


 


Technology Overview

The Quansor technology uses a low-cost electronic device, a quartz crystal microbalance (QCM) that is essentially a miniature scale which weighs the presence of target ions or molecules.  The crystal shown at the right is about the size of a thumbnail.  The crystal is excited electronically and made to oscillate at 10 million cycles per second (10 MHz).Tiddleywinks1

As a sample stream flows across the crystal, the targets, the ions or molecules, are attracted to the QCM by proprietary receptor chemistries that are deposited on the gold circle on the top surface of the crystal.  The weight or mass of the target on the receptor chemistry slows down the oscillations on the crystal indicating the presence of the target.  The greater the mass of target ions captured on the crystal, the greater the reduction in crystal oscillations.  This allows the sensor to quantify as well as identify specific targets.

The technology development covers four areas: (a) the sensor, (b) chemical receptors, (c) the internet data collection and reporting function and (d) peripherals in operating a continuous flow monitor.


 

QCM Sensor

The key issue is to employ a very sensitive device that is resistant to interferences.  The Quansor sensor employs a newly patented feature that removes the effects of temp fluctuations, a long-standing problem with QCM that until now has prevented its use in a continuous flow sensor.

Each sensor module will consist of (a) a piezoelectric diaphragm micropump[1], (b) a quartz crystal (c) an oscillating circuit, (d) a microprocessor, including an eeprom with calibration data and control circuitry.

The sensor will operate for months without replacement.  Most sensors can be regenerated automatically.  They will operate for months without replacement.  The cost of a replacement sensor module will be less than $100.


 

Chemical Receptors

chartThrough both UMass and UK, Quansor has an inventory of receptors for anions and cations that include heavy metals and others, either by individual species or by groups.  Included, for example, are the two principal species of arsenic, (arsenite and arsenate) and the principal species of mercury, (elemental, mercuric or methyl mercury).  There is a potential chemical receptor for any inorganic chemical.    As to organic chemicals, Quansor can potentially detect individual molecules, such as hexachlorobenzene, MTBE, TCE etc.

There are two principal receptors for inorganic chemicals:

PAH is a hydrogel coating[2] that binds to the gold surface of the crystal electrode, forming a first receptor layer.  It has been configured as an anion exchanger (shown to the right), a cation exchanger, and as a base for EDTA to detect metals and for lanthanum hydroxide to bind As(V).    A fatty acid bound to a PAH layer was effective in detecting total hydrocarbons.

A dithiol, AB9, is used as a receptor for Hg(II), Cd(II), Pb(II) and As(III)[3].  A similar receptor, B9 has been developed to bind Se(IV).

For organics, a molecular imprinted polymer (MIP) was created to detect hexachlorobenzene, displaying picogram sensitivity.

 

Data Collection, Reporting and Control Function

This area is developed and maintained by Wendell Wilson, owner of an 18-man software firm in Richmond, KY[4].  He also is lead developer of the electromechanical sensor, discussed above.

The data collection and reporting functions are operational.  A Quansor simulator is used to characterize new sensors and its data is displayed on a Quansor data website.  

Additionally, peripheral devices are or will be under software control: (a) diaphragm micropump, (b) pH meter, (c) thermistor, and (d) valves to activate in-line processes.

 

Peripherals  

Peripherals include:

(a) In-line removal of interfering chemicals.  The methods used will depend on the receptors.  For example, a feature of the covalent bonding of AB9 and Hg, Pb, Cd, and As(III) is that the AB9-M on the surface of the QCM will be impervious to aqueous cations like Na.  The As(III) is removed by passing the stream though an anion exchange column.   There are further means available to separate the cations.

(b) a Quansor-designed continuous-flow pH adjustment mechanism, together with an in-line pH meter,

(c) a configuration for progressive filtration of surface or groundwater down to 0.2 microns to prepare the sample flow for analysis

 



[1] Pump is a Bartels MP-6.
[2] Hoagland, D.A., Howie, D.W., Waldrop, A.A., “Hydrogel Coatings and Their Employment in a Quartz Crystal Microbalance Ion Sensor”, US2005/0196532 A1. 

[3] Atwood, D. A., Matlock, M. M., Howerton, B. S. (2003) “Novel Multidentate Sulfur-Containing Ligands” US No. 6,586, 600.
[4] http://www.wwbtc.com/