**6. Integrated analytical systems**

Instead of using only platinum as metallic resistance, deposition of various metals was reported: chromium/gold film (Cr/Au) or titanium/platinum (Ti/Pt). Intimate contact between the heater and the column allows extremely high heating rates (1500°C/s) [44]. Depending on the thickness and size of the chip, a heating power consumption can be as low as 4 W/m. In gas chromatography, separations are performed by temperature programming starting from lower to upper. For continuous monitoring or on-site analysis, GC system should be cooled to the initial state to start a new cycle. Peltier coolers are widely used in miniaturized GC. Also, the column can be set at sub-ambient temperature to retain volatile compounds, for example. This is an advantage compared to conventional GC systems which require liquid

After separating the compounds, a detector is used to monitor the outlet stream from the column. Detection in analytical microsystems is a subject of paramount importance. Indeed, detection has been one of the main challenges for analytical microsystems, since very sensitive techniques are needed as a consequence of the ultrasmall sample volumes used in micron-

The flame ionization detector (FID) is the most popular and widely used detector for the analysis of trace levels of organic compounds. Its success is based on outstanding properties, such as a very low minimum detectable limit, a high sensitivity, and a broad linear measurement range. Kuper's team works on miniaturized planar FID since 2000 where the oxygen-

At the opposite of FID, thermal conductivity detector (TCD) is a nondestructive system. It measures the difference in thermal conductivity between pure carrier gas and the carrier gas

**Figure 14.** Left: Photography of a micro-FID on a PCB adapted from [47], right: A suspended micro-TCD, adapted

hydrogen flame burns inside a glass-silicon chip (**Figure 14**) [45].

carbon dioxide or nitrogen.

162 MEMS Sensors - Design and Application

**5. Detectors**

sized environments.

from [48].

The development of MEMS gas chromatographic components is in progress at several laboratories and universities. Some characteristics of miniaturized GCs are listed in **Table 2**.

At this stage, microfabrication is an attractive option for the development of greatly improved instruments, and many investigations have been reported. However, there are no portable devices able to work anywhere, making accurate, automatic, and continuous analyses of gas samples.


**Table 2.** Comparison of some portable GC systems.

C2V Company released its first commercial micro-GC product (model C2V-200) in 2010. The platform, based on cartridges, allows hybrid integration of components such as sensors and valves to be assembled together with reduced dead volume. Integrated microchip technology combined with narrow bore capillary GC columns results in a higher performance for lower costs. The C2V-200 micro-GC is designed for ease of use, reduced maintenance, and low gas consumption. Exchangeable column cartridges, with integrated heating zones, can be easily installed (up to 4) with a different column and detection method. This modular setup allows the ability to monitor a wider spectrum of gas components in the same timeframe of 10 to 60 seconds [50].

**Author details**

**References**

Imadeddine Azzouz1,2\* and Khaldoun Bachari1

**168**(Supplement C):1398-1401

Systems. 2010;**19**(4):973-981

Systems. 2012;**21**(3):730-738

2008;**27**(4):327-343

\*Address all correspondence to: imadeddine.azzouz@esiee.fr

1 Research Center in Analytical Chemistry and Physics (CRAPC), Algiers, Algeria

[1] Brown PR. Advances in Chromatography. New York: CRC press; 1993. 296 p

con wafer. IEEE Transactions on Electron Devices. 1979;**26**(12):1880-1886

tenax-TA films. Procedia Engineering. 2010;**5**(Supplement C):1152-1155

pole array and Paul ion trap. Mass spectrometers. 2003

'99 1999 International; 1999 6-8 July 1999

**1422**(Supplement C):299-309

[2] Terry SC, Jerman JH, Angell JB. A gas chromatographic air analyzer fabricated on a sili-

MEMS Devices for Miniaturized Gas Chromatography http://dx.doi.org/10.5772/intechopen.74020 165

[3] Wang J, Nuñovero N, Lin Z, Nidetz R, Buggaveeti S, Zhan C, et al. A wearable MEMS gas chromatograph for multi-vapor determinations. Procedia Engineering. 2016;

[4] Alfeeli B, Hogg D, Agah M. Solid-phase microextraction using silica fibers coated with

[5] Nachef K, Bourouina T, Marty F, Danaie K, Bourlon B, Donzier E. Microvalves for naturalgas analysis with poly ether ether ketone membranes. Journal of Microelectromechanical

[6] Nachef K, Marty F, Donzier E, Bourlon B, Danaie K, Bourouina T. Micro gas chromatography sample injector for the analysis of natural gas. Journal of Microelectromechanical

[7] Holland PM, Chutjian A, Darrach MR, Orient OJ. Miniaturized GC/MS instrumentation for in situ measurements: micro gas chromatography coupled with miniature quadru-

[8] Voiculescu I, Zaghloul M, Narasimhan N. Microfabricated chemical preconcentrators for gas-phase microanalytical detection systems. TrAC Trends in Analytical Chemistry.

[9] Frye-Mason GC, Manginell RP, Heller EJ, Matzke CM, Casalnuovo SA, Hietala VM, et al., editors. Microfabricated gas phase chemical analysis systems. Microprocesses and Nanotechnology Conference, 1999 Digest of Papers Microprocesses and Nanotechnology

[10] Lahlou H, Vilanova X, Correig X. Gas phase micro-preconcentrators for benzene monitoring: A review. Sensors and Actuators B: Chemical. 2013;**176**(Supplement C):198-210 [11] Bryant-Genevier J, Zellers ET. Toward a microfabricated preconcentrator-focuser for a wearable micro-scale gas chromatograph. Journal of Chromatography A. 2015;

2 ESYCOM/ESIEE Paris, University of Paris-Est, Noisy-le-Grand, France

#### **7. Conclusion**

The concept of micro-gas chromatographs demonstrates the potential of mobile devices in various fields related to analytical chemistry such as oil and gas, air analyses, defense, food processing industry, etc. New instrument designs and component manufacturing methods are coming on line that will result in the development of a new generation of high-performance, moveable, and miniaturized instruments for high-performance gas chromatography (HP-GC). The use of microelectromechanical system technologies for the manufacturing of microfabricated gas chromatographic components results in very small, autonomous, and low-cost instruments. Completely autonomous GC instruments require no daily maintenance and can be placed in remote locations for long-term service. This requires battery operation, wireless communications, and freedom from tanks of compressed gases. To this end, work is in progress to develop a high-performance micro-GC that will have acceptable volume. To achieve complete autonomy, vacuum outlet GC should be used with ambient air as carrier gas. In addition, remote battery charging with radiofrequency transmission will be feasible. The use of ambient air as a carrier gas poses several challenges. First, some stationary phases rapidly decompose in air. Poly(ethylene glycol) is a good example. In addition, particulate material and water vapor may need to be removed. Sensor array detection also is needed because these devices can be microfabricated with very low dead volumes; they require no support gases for their operation, and they can be fabricated with a variety of selectivities, which can be used for vapor recognition and for the deconvolution of overlapping peaks. This can reduce the resolution requirements for the column. Sensors and detectors usually have lower sensitivity than detectors incorporated in laboratory gas chromatographic instruments. Low detector sensitivity, coupled with the very low concentrations often associated with air monitoring, requires the use of a preconcentrator for sample enrichment prior to separation and detection. More energy is then needed to heat the preconcentrator to release the adsorbed sample. It seems that one way to solve these problems is a future integration of the instrument on a single chip, focusing each device to one field of application instead to make universal apparatus emulating conventional gas chromatographs.

#### **Conflict of interest**

The authors declare no conflict of interest.
