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  5. Real Time Chemical Process Measurements Using a GC/SAW System

In the sphere of pharmaceutical chemistry, process chemistry revolves around the development and optimization of a synthetic scheme and manufactures compounds for the drug development phase. Chemical engineers also sketch large-scale processes to convert raw materials, chemicals, living cells, energy and microorganisms into utilitarian structures and products. And as this optimal chemical processing depends largely upon timely and precise measurements of the chemical processes, the need of a fully automated instrument becomes vital to speciate and quantify process chemistry in real time.

Though many types of GC instruments for field screening are out in the market, there is no instrument versatile enough to analyze a wide range of organic compounds. GC technology alone acts as an inadequate tool for many applications. But California-based EST Inc.’s zNose® is a unique technology with substantially functional features that differs it from others in the market. This electronic nose, unlike others, uses a GC system equipped with an SAW detector for process measurement applications.

The Surface Acoustic Wave (SAW) gas chromatography sensor is the advanced form of chromatography for process measurements. The SAW detector is the first and only known integrating detector for GC systems which requires no high voltages or radioactive ionization sources. It is capable of processing millisecond duration peaks and is a true solid state chip technology with high accuracy at low cost.

To test the accuracy, speed and precision of zNose®, its GC/SAW system was subjected to various measurements in the laboratory and field conditions. Following are the results of two such measurements:


Methyl isocyanate (also called methyl carbonyl amine, MIC.) that acts as an intermediate chemical in the production of carbamate pesticides and herbicides was measured using zNose®. The standard deviation from a series of replicate measurements of MIC at relatively high concentration levels (1000 ppm) displayed the accuracy and precision of the GC/SAW for process control.

As MIC is very toxic and inhalation can damage it, there is a need to monitor ambient air concentrations for safety. OSHA limits are 20 ppbv in air or 0.05 mg/m3. Thus, replicate measurements at 0-50 ppbv levels were also carried out. A typical series of replicate chromatograms and standard deviations gave an explanative view of MIC.


As Biochemical processes frequently involve growth and maintenance of a healthy colony of bacteria for industrial and pharmaceutical products broadly, there is a need to observe the viability, health, and production of chemicals by bacteria in real time. zNose® using its GC/SAW technology observed the chemistry of headspace vapors from a liquid containing e. Coli bacteria. The real-time chemical analysis provided information on nutrient levels as well as the number of colonies forming units present. The GC/SAW system also provided a method of quantifying the bacterial population in real time.

Hence, these test results show that it is possible to speciate and quantify a wide range of chemicals in near real time (within 1 minute). Moreover, zNose® represents a significant advancement in fast chromatographic methods with the ability to accurately measure, a wide range of compounds without sacrificing precision or accuracy. Therefore, advanced technology like zNose® turns out to be notable and efficient for the chemical engineers, scientists, chemists and pharmaceutical industry.


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