Technology Overview

Paradigm Sensors Technology

Paradigm Sensors uses a specific form of spectroscopy, Impedance spectroscopy (IS), that supports very simple and rugged sensors capable of providing a high degree of information about fluid composition and functionality and because it is possible to use IS in field instruments and in-situ sensors.

Theory of the Use of Impedance Spectroscopy

Impedance spectroscopy (IS) is an analysis technology generally analogous to infra-red spectroscopy.  For IS, an electrical current is passed through a sample and the voltage developed is measured (or, conversely, voltage is applied and current flow is measured).  As with other forms of spectroscopy, this is done over a range of frequencies, with the frequency response of the material providing information on sample composition and functionality.

The Use of  IS in Materials Characterization involves the use of AC impedance measurements to characterize the electrical properties of materials systems provides an alternate means of measuring composition, as well as critical physio-chemical attributes. This methodology (see Figure 1) has been successfully applied to a variety of fluids, including multiple parameter determinations for biodiesel fuel.

IS as a materials characterization methodology.

Figure 1. IS Characterizes Changes in Materials Properties.

Why Impedance Spectroscopy?

Impedance spectroscopy (IS), an analysis technology, has two major advantages over IR for biodiesel FCM field instruments. First, since IS relies on voltage and current measurements vs. optical measurements, very simple, rugged, and inexpensive sensing electrodes can be used. While it is true that electrode shape and materials are critical to effective IS measurements, materials can be quite inexpensive and forms easily manufactured in high volumes.  Second, IS allows the observation of types and rates of chemical reactions occurring at the fuel/electrode interface, reactions which are indicative of changes in key fluid constituents.

Additionally, IS  technology is analogous to FTIR and GC and allows proprietary data mining using algorithms to establish correlation curves between key IS parameters and biodiesel composition and functions.   Thus, the i-SPEC® can put the information previously available only from lab testing in the palm of your hand.

Correlation of IS Data to ASTM Physio-Chemical Parameter Values

The acquisition of electrical impedance data over approximately five decades of AC frequency (employing a proprietary measurement probe configuration) was performed on a substantial population of samples over a defined temperature range (10 – 45° C). The samples included a variety of B100 fluids from multiple feedstocks, as well as a range of blends from 2-99% derived from commercially available petroleum diesel fuels.  Multivariate regression analysis was utilized to develop temperature compensated correlations between IS derived variables and 1)Blend concentration ; 2) Total Glycerin concentration; 3) Methanol Concentration; and 4) Acid Number.

The reference methods * which were correlated to IS measurements are as follows:

Blend Concentration (2-99%)
Mid Infrared Spectroscopy (ASTM D7371)

Total Glycerin (0.03 - 0.7 %)
Gas Chromatography (ASTM D6584)
- SafTest

Methanol (pass/fail)
Gas Chromotography (EN 14110)
- Mid infrared Spectroscopy

Acid Number (pass/fail)
Titration (ASTM D664)
- SafTest

* ASTM D6751

Applications of IS Technology

Paradigm Sensors technologists have extensive background in the application of IS sensing and analysis technologies. Fluid condition monitoring applications pursued by the team to-date include:

  • Measurement of deterioration, contamination, and additive depletion in auto and truck engine lubricants,
  • Corrosion protection of auto and truck engine coolants,
  • Depletion and regeneration of aqueous resin beds (water softeners),
  • Deterioration of electronic solder paste,
  • Printability of electronic printing inks.
  • Biodiesel/diesel blend percent
  • Total Glycerin in biodiesel
  • Other contaminants in Biodiesel

Paradigm Sensors’  i-SPEC® Q-100

Paradigm Sensors’ i-SPEC ® Q 100, a biodiesel handheld analyzer, incorporates proprietary IS sensing technology, which has demonstrated excellent correlation to traditional reference methods.  In minutes, the  i-SPEC® can simultaneously measure the following in B90-B100 fuels:

  • percent blend of biodiesel
  • total glycerin content
  • methanol content
  • acid number 

The i-SPEC® can also determine the following in blended biodiesel :

  • Blend percentage ( 0-100%)
  • Original total glycerin in the B100 used for the biodiesel blends of 6% to 99%

These results are quantitative for blend percent within 1 and for total glycerin to 0.05%. No interpretations are necessary, nor are subjective observations used to evaluate results.

Petro Industry News article, “Biodiesel Analysis Utilizing AC Small-Signal Impedance Spectroscopy.”  Click to download PDF


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