# Development of an original compact multigas detection system based on MEMS components

Florence Ricoul, Jean-Francois Beche, Mahfod Benessalah, Stéphane Caplet, Murielle Jurdit, Emilie Lefrancois, Alexandre Teulle, Jean-Baptiste Tissot

► To cite this version:

Florence Ricoul, Jean-Francois Beche, Mahfod Benessalah, Stéphane Caplet, Murielle Jurdit, et al. Development of an original compact multigas detection system based on MEMS components. Journal of Micromechanics and Microengineering, 2025, 35 (11), pp.115008. 10.1088/1361-6439/ae1e88. cea-05396462

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Distributed under a Creative Commons Attribution 4.0 International License
# Development of an original compact multigas detection system based on MEMS components

Florence Ricoul*, Jean-François Beche, Mahfod Benessalah, Stéphane Caplet, Murielle Jurdit, Emilie Lefrancois, Alexandre Teulle and Jean-Baptiste Tissot

University Grenoble Alpes, CEA, LETI, F-38000 Grenoble, France

E-mail: florence.ricoul@cea.fr

Received 28 August 2025, revised 4 November 2025

Accepted for publication 12 November 2025

Published 21 November 2025

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CrossMark

## Abstract

An original compact multigas detection system based on micro electro mechanical systems components is presented. A micro preconcentrator, a micro separation column and a micro-thermal conductivity detector are coupled to each other using a novel micro-machined fluidic circuit board, simplifying the fabrication and assembly of these components with significant savings in manufacturing time, footprint and robustness of the overall system. The performances of the system are illustrated with the analysis of several typical volatile organic compounds mixtures.

Supplementary material for this article is available online

Keywords: gas chromatography, microfluidics, MEMS, micro-preconcentrator, micro-TCD

## 1. Introduction

The rapid on-site detection of complex gas mixtures is a challenge in many fields, including safety, healthcare, environmental monitoring, and industrial process control. Portable gas chromatography (GC) systems could address these needs. Continuous research efforts over the past decades have aimed to develop such systems, making them increasingly compact, energy-efficient, sensitive, and selective, particularly through the advancement of silicon micromachined components such

as injectors/preconcentrators, separation columns, and detectors. If multiple examples of systems illustrate the improvements obtained as reviewed by Lussac et al [1] or Crucello et al [2], there are still limitations in terms of integration (see Regmi and Agah [3]).

In particular, the integration of silicon-based microcolumns should enable the development of compact, energy-efficient systems. One of the challenges encountered is the fluidic interfacing of the microcolumns with the rest of the system [4]. On the one hand, it is essential to maintain minimal dead volumes, and on the other, strong thermal constraints associated with different materials (silicon, glass, etc) must be managed. Various interfacing techniques have been developed, but the most common remains the use of fused silica capillaries ([5, 6] or [7]). However, this approach has certain limitations: in general, it does not allow for operation at high temperatures, with few exception using multiple adhesives (see work of Li et al in [8]) or reversible assemblies with ferrules [9]. Indeed, in both last cases, column heating is achieved using an

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Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

<footnote>* Author to whom any correspondence should be addressed.</footnote>
<table><caption>**Table 1.** Comparison of main different integration strategies for the interconnection of MEMS components for complete miniaturized GC systems (N/R = not reported; MOX = metal-oxide semiconductor; µCR = micro chemiresistors; PID = photoionization detector).</caption><thead><tr><th># references</th><th>Interconnection strategy</th><th>Serviceability</th><th>Transfer line heating</th><th>Heaviest or most surface-adhering compound tested (vapor pressure @ 25 °C)</th><th>μPC T<sub>max</sub> (°C)</th><th>μGC T<sub>max</sub> (°C)</th><th>Detector</th></tr></thead><tbody><tr><td>Zampolli et al [11]</td><td>Several stainless steel modules</td><td>Good</td><td>No</td><td>m-xylene (1.1 kPa)</td><td>100</td><td>N/R</td><td>MOX detector array</td></tr><tr><td>Garg et al [5]</td><td>Glued capillaries</td><td>μGC and μTCD not independent</td><td>No (just minimized length)</td><td>p-xylene (1.1 kPa)</td><td>200</td><td>60</td><td>μTCD embedded in μGC</td></tr><tr><td>Qin and Gianchandani [15]</td><td>Glued separated μfabricated connectors</td><td>Poor</td><td>No</td><td>Hexane (20.4 kPa)</td><td>250</td><td>50</td><td>Capacitive detectors</td></tr><tr><td>Wang et al [6]</td><td>Glued capillaries + press-tight unions</td><td>Poor</td><td>Yes (required for Pv &lt;0.59 kPa compounds)</td><td>Dodecane (0.027 kPa)</td><td>225</td><td>150</td><td>μCR array</td></tr><tr><td>Wang et al [7]</td><td>Glued capillaries + press-tight unions</td><td>Poor</td><td>No</td><td>Dodecane (0.027 kPa)</td><td>225</td><td>125</td><td>μCR array</td></tr><tr><td>Zampolli et al [12]</td><td>Silicon FCB</td><td>Good</td><td>Possible but no data</td><td>Hexane (20.4 kPa)</td><td>350</td><td>200</td><td>μTCD/PID</td></tr><tr><td>Li et al [16]</td><td>Glued capillaries + press-tight unions</td><td>Poor</td><td>No</td><td>Undecane (0.055 kPa)</td><td>N/R (stainless steel tube)</td><td>145</td><td>Miniaturized PID</td></tr><tr><td>Liao et al [13]</td><td>Monolithic integration (but dies glued with epoxy adhesive)</td><td>Poor (μPC, μGC or detectors not independent)</td><td>No (just minimized length)</td><td>DMMP (0.13 kPa), DEMP (0.037 kPa), octanol (0.011 kPa) (but asymmetric peaks)</td><td>180</td><td>70</td><td>Capacitive detectors + μPID</td></tr><tr><td>This work</td><td>Aluminum FCB</td><td>Good</td><td>Yes (FCB)</td><td>Methyl salicylate (0.0046 kPa)</td><td>300</td><td>200</td><td>μTCD</td></tr></tbody></table>

external oven from a commercial GC system; in portable systems, the challenge lies in managing the heating of the transfer lines, especially when there is stationary phase on one part. Alternative solutions have been proposed. For example, Ghosh et al in [10] suggested the use of Kevlar clamps. Zampolli et al [11] developed stainless steel modules for each component of the analytical system, which are then interconnected. Another approach, introduced in 2020 [12], involves using a single silicon-based fluidic circuit board (FCB) to achieve interconnection. A highly but rather complex monolithic integration of micro electro mechanical systems (MEMS) components has also been proposed by Liao et al [13].

Besides, TCD is a detector frequently used in GC due to its universal detection capability, wide dynamic range,

and minimal footprint. Currently, sensitivities of the order of ppm are achievable thanks to miniaturization (see [3]). While monolithic integration of the detector with the separation column has been proposed ([5, 14]), the connection to the rest of the system relies on capillaries bonded to the chip.

Table 1 summarizes the main integration strategies proposed to date for interconnecting MEMS components in fully miniaturized GC systems, highlighting their characteristics in terms of serviceability and transfer-line thermal management. It is important to note that few studies have addressed the analysis of low-volatility and/or sticky compounds, and therefore had to manage the heating of transfer lines between the different components. In this work, we propose a novel approach for the reversible interconnection of
three silicon-based components—namely, a micro preconcentrator (μPC), a micro gas chromatography column (μGC), and a micro thermal conductivity detector (μTCD)—to develop a compact prototype for multi-gas analysis. These components are integrated via a single micro-machined FCB, streamlining the assembly process while improving system flexibility, robustness and cost-effectiveness while allowing easy heating of the transfer lines, that is required for low-volatility and/or sticky compounds. The performance of the system is evaluated through the analysis of various volatile organic compounds (VOCs).

## 2. Materials & methods

### 2.1. Sample preparation and GC reference system

Gas samples were prepared in 1 l Tedlar® bags (Supelco, 24633): for the BTEX compounds (benzene, toluene, ethylbenzene and o-xylene), a gas cylinder supplied by air Products was used to fill the bags with an already prepared mixture containing each compound at a concentration of 0.5 ppm, balanced in 5.0-grade nitrogen (99.999% purity); nitrogen was chosen to ensure good molecular stability during storage; however the presence of oxygen in future potential real samples will have no effect on the system's response to the analysis of target molecules: to verify this, toluene samples were prepared at 23 ppm by introducing 0.1 µl of pure product (purchased from Sigma-Aldrich, with a purity >99%) into pre-filled Tedlar bags containing either nitrogen or synthetic air (5.0-grade nitrogen with 20.9 ± 1% oxygen). Similarly, to test the influence of humidity, a toluene sample at 23 ppm was prepared in nitrogen with an additional 40% relative humidity, by adding 9.2 µl of water into the 1 l Tedlar bag.

For the other compounds (methyl salicylate (MS), (+)-alpha-pinene, R-(+)-limonene), pure products were purchased from Sigma-Aldrich with high purity >99%; a volumetric dilution in ethyl acetate to 1:100 is performed and 1 µl of the diluted solution is introduced through the septum into 5.0 nitrogen pre-filled bags; calculated concentration is 1.9 ppm for MS and 1.5 ppm for (+) alpha-pinene and R-limonene.

An Agilent 7890B GC system equipped with a split/splitless injector (7693A) and a FID (Flame Ionization Detector) was used for reference measurements (temperature 300 °C, airflow 400 ml min⁻¹, hydrogen flow 30 ml min⁻¹, no makeup gas).

### 2.2. MEMS components fabrication and functionalization

The μPC, μGC and μTCD dies have been mass-manufactured from silicon and glass 200 mm wafers using MEMS technologies (photolithography, deep reactive ion etching, etc) as described previously [17, 18], with the main difference being that their fluidic inlet/outlet through holes are drilled in the cover (0.5 mm diameter for μPC, 0.4 mm for μGC, 0.2 mm for μTCD). For the μPC and the μGC, glass cover wafer has through holes drilled before being anodically bonded to

the silicon wafer with etched cavities. Platinum temperature probe and heating resistance are deposited on the back side of the silicon wafer. More precisely, after dicing, as shown in figure 1, the μPC is 21 × 7.6 mm² with a 12 μl intern cavity. The cavity is filled with Tenax TA (80–100 mesh) powder (Supelco, 21009-U) adsorbent by applying vacuum to one inlet with a dedicated manifold (cf figure S1). The μPC serves as both a concentrator and an injector. During sampling, the targeted analytes are trapped onto the adsorbent, and then during desorption, thanks to the rapid heating of the chip, the analytes are transferred to the separation column as a narrow plug. The longer the sampling time, the greater the concentration factor obtained, with the limitation of the breakthrough volume (maximum volume possible before the analyte begins to exit the μPC) which varies for each analyte depending on its affinity with the adsorbent [19].

For the μGC die, a 2 m long, 80 μm large, 80 μm deep circular-spiral channel is etched in the silicon part (21 × 21 mm²) using the same MEMS technologies as for the μPC. This layout is one of the three most popular configurations tested by researchers, which represent a compromise between a small chip footprint and sufficient sampling capacity [3]. Platinum temperature probe and heating resistance on the back side enable temperature-programmed separations. The stationary phase (silicon OV-1 from Ohio Valley Specialty) is deposited after die dicing, following the static method as described in [20], with a 10 mg ml⁻¹ solution in a 50:50 pentane/dichloromethane volumetric mixture, a syringe pump and a dedicated manifold (cf figure S2). The solvent is evaporated for 2 h under vacuum and then a 2 h treatment at 120 °C is applied under helium flow. Assuming that all the stationary phase introduced into the channels is deposited uniformly, a theoretical average phase thickness of 228 nm is calculated. It is important to note that with this approach the stationary phase is deposited only inside the die, lowering the constraints on the heating of the transfer lines between the column and the other elements of the system. Prior to the integration of the die, the efficiency of the microcolumn has been characterized at 40 °C using a pentane-octane mixture and the commercial GC system at different flow rates. A minimal height equivalent of a theoretical plate (HETP) of 1.5 mm (~666 plates m⁻¹) was measured with a retention factor of 5.4 for octane. The efficiency of the μGC could certainly be improved for example by decreasing the initial concentration of the stationary phase but at the expense of the retention factor. The robustness of the stationary phase was verified by re-measuring the HETP and octane retention factor after approximately 80 cycles under a 35 °C–65 °C profile: an increase of only 2% in HETP and a decrease of less than 4% in the retention factor are measured. The choice of the non-polar stationary phase was made to allow the separation of the targeted VOC molecules, which are also non-polar. In each case, the column thermal gradient was optimized to obtain satisfactory peak resolution while minimizing the analysis time.

Finally, for the μTCD die, as described previously in [21] or [22], in a bottom silicon wafer, four SiN membranes
<figure><img src="image_4.png" /><figcaption>**Figure 1.** Photographs of the different MEMS components: left, the μPC with a 12 μl cavity filled with Tenax TA visible on the front side and heating resistance and temperature probes on the back side; middle, the μGC with a 2 m long circular-spiral channel on the front side and heating resistance and temperature probes on the back side; right, the μTCD bonded on a PCB with four 0.2 mm fluidic inlets.</figcaption></figure>

(90 × 640 μm²) coated with Pt wires are microfabricated so as to be suspended: two above a reference channel and two above an analysis channel (200 × 200 μm² cross-section) and electrically connected in a Wheatstone bridge configuration. The Pt wires ensure both the heating of the membranes and the measurement of their temperature. The fluidic inlet/outlet through holes are drilled in a silicon top wafer which is then sealed to the wafer having the channels and membranes. Once diced, the die, 6.9 × 9.6 mm², is glued to a dedicated printed circuit board (PCB) and the electrical pads are wired bonded with gold wires to the corresponding pads on the PCB. Applied bias is 6 V. When an analyte passes through the analysis channel there is a variation in the temperature of the heated membranes due to the difference in thermal conductivity which results in an imbalance of resistances with the reference channel which is detected.

## 2.3. System architecture and FCB conception and fabrication

A new concept for the fluidic connection of the different MEMS components necessary for the GC based multigas detection system was used. The three components (the μPC, the μGC and the μTCD) of the system are connected to each other using a single FCB with significant space requirements savings and system robustness improvements. The FCB is made by micro-machining in an aluminum block, with 0.5 or 1 mm drillings, simplifying its production, in term of manufacturing price or cost compared to what has been previously proposed in the literature [12]. First, the components are connected to the FCB on its front side using silicone (hardness shore A = 71) or FPM (hardness shore A = 78) O-rings from Grenoble Alpes Elastomères, ensuring gas tightness while maintaining their thermal insulation. For both types of O-rings no physical or chemical degradation was observed after dozens of thermal cycles even though the specified maximum operating temperature is 220 °C or 200 °C respectively. On the back side, capillaries (Molex, Polymicro Technologies TSP100170, ID 100 μm, OD 170 μm) are directly glued (with epoxy adhesive) to the FCB and protected by a 3D-printed housing, enabling the fluidic connections between the different components, similar to routing an electrical printed circuit, while

<figure><img src="image_5.png" /><figcaption>**Figure 2.** Schematic of the multigas detection system.</figcaption></figure>

controlling dead volumes. This design eliminates the tedious step of gluing capillaries to each component, simplifying assembly and components exchange. In terms of dead volumes this solution proved to be better than completely machining the channels in the aluminum block and adding a cover with seals or inserting commercial connectors (such as EU.1 from VICI Valco Instruments) into the block. As a result, the system gains greater versatility, allowing for easy and rapid modifications to its overall architecture. Leak tests were performed regularly using a he leak detector (LD 239 GL Sciences): even after several dozens of analyses, and thus thermal cycles, no leak was detected either at the O-rings level nor at the epoxy adhesives level.

Figure 2 shows the block diagram of the system including the FCB. The μPC not only increases the sensitivity of the system but also plays the role of an injector. During sampling, thanks to the actuation of the pump and valves, the analytes are trapped and concentrated in the μPC; a purge of the μPC with the carrier gas is performed for 1 min with any non-adsorbed interferents evacuated through the sample inlet; during analysis, the analytes are rapidly desorbed from the μPC thanks to the quick heating of the chip and transferred in backflush mode to the μGC and the detector by the helium flow. The μTCD is a universal detector, and has the advantage of not requiring additional gas like H₂ and having very small foot print. Cleverly, in
<figure><img src="image_6.png" /><figcaption>**Figure 3.** Photographs of the compact multigas detection system: left: the 3 MEMS components (μPC, μGC and μTCD) in place in the front side of the FCB; right: back side with the fluidic interconnection with glued capillaries directly on the aluminum block.</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>**Figure 4.** Photograph of inserted heating element and of the fan for the FCB temperature regulation.</figcaption></figure>

our configuration, only one carrier gas line is necessary for the μTCD: the gas flow leaving the μPC after the desorption of the analytes is first introduced in the reference line of the μTCD before being connected to the μGC for the analytes separation and finally to the analysis line of the μTCD for the detection. Figure 3 shows a photography of the FCB with the components fluidically connected and with the PCBs for the electrical connections. Electrical contacts for the μPC and μGC are obtained by POGO pins mounted on PCBs.

If heating of the fluidic connections between the components is required to prevent cold spots, a heating resistor (36 W, from Electrowatt) is integrated inside the housing along with a dedicated support and a small fan to accelerate cooling (figure 4).

As shown in figure 2, two micro solenoid valves (one 2-way, one 3-way, X-812LF and X-512LF from Parker) and one micro pump (SP-100EC-DU from Schwarzer Precision) are used to complete the fluidic circuit. Sampling flow rate was measured at 190 ml min⁻¹. In this work, the carrier gas used is helium, supplied by the injection system of the commercial GC used as a reference, but it would also be possible to use gas cartridges or air pumped by a second micropump to enable field measurements with a completely portable and autonomous system (cf figure S5 and discussion in part 3.1).

A dedicated control electronics allows μTCD signal acquisition, valves and micropump operation for the sampling and

μPC, μGC and FCB heating. The system communicates with a laptop computer by USB using a Labview-based user interface.

Figure S3 provides a schematic illustration of the different phases of the analysis over time, showing the successive activation and deactivation of the various system components, whereas tables S1 and S2 provide a quantitative power budget of the system: obviously the main power consumption is due the FCB heating: an improvement in the FCB design (mass reduction) will be necessary to improve the system's autonomy in the field with the use of batteries. However, even now, with a correctly sized battery, the current system could be used for several analysis cycles.

# 3. Results & discussion

## 3.1. BTEX mixture separation

The first tests of our system were carried out on a typical mixture of indoor pollutants, a BTEX mixture, at 0.5 ppm each. The analytes were sampled for 30 s through the μPC. For the desorption phase, the inlet pressure of helium was set to 30 psi which corresponds to a flow rate of 0.218 ml min⁻¹. Desorption of the analytes on Tenax was performed by heating the μPC at 220 °C during 10 s. A gradient from 35 °C to 60 °C with a 0.23 °C s⁻¹ (14 °C min⁻¹) ramp was applied to the μGC, 50 s after the beginning of the μPC desorption.

The figure 5 (up) shows the chromatograms obtained on the μTCD for the BTEX mixture analysis after subtraction of the baseline. Temperature monitoring of the μPC and μGC is showed on the bottom (no temperature regulation of the FCB was applied in this case which was at room temperature (24 °C)). Thanks to the rapid heating of the μPC (over 50 °C s⁻¹) and controlled dead volumes, a sharp injection peak for the analytes is obtained which is a necessary condition to obtain resolved chromatograms: the figure 5 shows that four fairly fine peaks are obtained in the case of the BTEX sample with good resolution in just over 2 min (resolution factors Rₛ are 3.3 and 1.9 for benzene/toluene and ethyl-benzene/o-xylene pairs respectively). Table 2 summarizes FWHM and Rₛ for these representative analyte pairs extracted from figure 5.
<figure><img src="image_8.png" /><figcaption>**Figure 5.** Analysis with 30 s sampling of a BTEX mixture containing 0.5 ppm of each compound in dry nitrogen and of ambient air (RH ~ 40%; CO₂ ~ 440 ppm). Up: temperature monitoring of µPC and µGC components during the analysis; below: chromatograms after baseline subtraction obtained for the BTEX mixture (blue) and for the ambient air (orange) including the µGC thermal gradient.</figcaption></figure>

<table><caption>**Table 2.** Retention time (T<sub>r</sub>), peak width (FWHM), and resolution for each component of the BTEX mixture analyzed in figure 5.</caption><thead><tr><td>Compound</td><td>T<sub>r</sub> (s)</td><td>FWHM (s)</td><td>R<sub>s</sub></td></tr></thead><tbody><tr><td>Benzene</td><td>23.1</td><td>3.9</td><td></td></tr><tr><td>Toluene</td><td>51.5</td><td>5.7</td><td>(B/T) 3.3</td></tr><tr><td>Ethyl-benzene</td><td>103.2</td><td>6.8</td><td></td></tr><tr><td>o-xylene</td><td>124.4</td><td>6.3</td><td>(E/X) 1.9</td></tr></tbody></table>
<figure><img src="image_9.png" /><figcaption>**Figure 6.** Superposition of the chromatograms obtained with the μTCD (after baseline subtraction) and with the FID placed downstream of the system, for the analysis of the BTEX 0.5 ppm mixture under the same conditions as in figure 5.</figcaption></figure>

<table><caption>**Table 3.** RSD of retention time and peak area for the analysis of BTEX mixture at 0.5 ppm, with 30 s sampling time (n = 3).</caption><thead><tr><th></th><th>Benzene</th><th>Toluene</th><th>Ethyl-benzene</th><th>o-xylene</th></tr></thead><tbody><tr><td>RSD on the retention time measured with μTCD</td><td>2%</td><td>3%</td><td>2%</td><td>2%</td></tr><tr><td>RSD on the peak area measured with μTCD</td><td>6%</td><td>1%</td><td>3%</td><td>1%</td></tr><tr><td>RSD on the retention time measured with FID</td><td>2%</td><td>3%</td><td>2%</td><td>2%</td></tr><tr><td>RSD on the peak area measured with FID</td><td>2%</td><td>4%</td><td>3%</td><td>5%</td></tr></tbody></table>

The importance of dead volumes control is also illustrated in the figure S4 where the chromatograms obtained with the current version of the FCB and with a first attempt of the FCB using commercial screw connectors (Vici EU.5) instead of epoxy glued capillaries are compared: the peak width for toluene goes from 0.11 to 0.23 min.

Even with passive cooling, the μPC chip cools down quickly (in less than 60 s), allowing for rapid successive analyses.

The results shown on the same figure 5 for the analysis of ambient air immediately following the BTEX mixture analysis confirms that desorption on the μPC is complete in a single run under the selected parameters, with no evidence of system contamination.

The signal obtained with the FID reference detector placed downstream of the system is superimposed on the figure 6 and confirms the passage of analytes through the system without loss or degradation. The resolution of the last two peaks is just

lower, which can be attributed to the addition of extra connections up to the FID.

As shown in table 3, the relative standard deviation (RSD) calculated on the μTCD signal or the FID signal for three consecutive analyses are below 3% for the four molecules for the retention times and below 6% for the peak areas. This demonstrates that sampling with the μPC is repeatable as well as the detection with the μTCD. Moreover, the linear variation of the signal as a function of sampling time was verified, as illustrated in the figure 7.

Finally, for this sampling time of 30 s, by considering the peak height divided by the baseline noise (3σ) measured in a flat area (0.002 mV), the limit of detection (LOD) is calculated of the order of 16 ppb. The limit of quantification (LOQ) (peak height divided by 10 time the noise) is calculated of the order of 52 ppb.

It is important to note that these values depend on the sampling time (LOD is improved by a factor two when
<figure><img src="image_10.png" /><figcaption>**Figure 7.** Variation of the peak area with sampling time for the analysis of the 0.5 ppm BTEX mixture (dotted lines are the linear fit for data, with R² > 0.99).</figcaption></figure>

<figure><img src="image_11.png" /><figcaption>**Figure 8.** Chromatograms obtained after baseline subtraction for the analysis of toluene prepared at 23 ppm in a Tedlar bag balanced either with dry nitrogen, dry synthetic air or nitrogen with 40% RH and sampled during 10 s (other experimental conditions (µPC and µGC thermal gradients) are the same as for figure 5).</figcaption></figure>

sampling time is doubled). This LOD may also depend on the
carrier gas used (that can impact detector sensitivity or sep-
aration column efficiency [23]) and the way it is implemen-
ted (fluidic noise): see for example figure S5, with chromato-
grams of the same sample obtained either with helium as car-
rier gas or with pumped air; in this case switching from he to
air reduces peak height and increases noise, yielding an overall
S/N decrease (~7–8×; see SI).

Finally, as illustrated in figure 8 with the example of tolu-
ene, it was verified that the presence of humidity or oxygen in
the samples as it will be the case in future real samples, does
not affect the µTCD signal. Indeed, neither water nor oxygen
are retained on the µPC adsorbent used or on the µGC station-
ary phase, and any potential traces are quantitatively purged
before the µPC chip is heated, or elute within the dead volume

of the separation column. The signal measured in figure 5 for
the ambient air sampled in the laboratory already indicated the
absence of interfering peaks.

3.2. Heavier VOCs separation

The analysis of a mixture of (+)-alpha-pinene and R-(+)-
limonene, ubiquitous and biogenic VOCs with boiling point
over 150 °C (cf table S1), prepared at 1.5 ppm each as
described in the experimental part, was then tested. The
sampling time was 5 s. The heating parameters of the µPC
and of the µGC were optimized to obtain a complete desorp-
tion of the analytes (verified by the analysis of a 2nd desorp-
tion without detection of the analytes) and the fastest possible
separation while maintaining good resolution (FCB thermal
<figure><img src="image_12.png" /><figcaption>**Figure 9.** Analysis of a mixture of (+)-α-pinene and R-(+)-limonene prepared in dry nitrogen at 1.5 ppm sampled during 5 s: up, temperature monitoring of µPC and µGC components during the analysis; below, chromatogram obtained after baseline subtraction including the µGC thermal gradient.</figcaption></figure>

regulation has not yet been necessary for the analysis of these molecules). The µPC desorption was performed at 250 °C during 20 s and a gradient from 40 °C to 100 °C with a 26 °C min⁻¹ ramp was applied to the µGC, 40 s after the beginning of the µPC desorption. Figure 9 shows the chromatograms obtained (after baseline subtraction) with the µTCD and demonstrates the possibility to detect these molecules with the system.

Finally, the analysis of even less volatile molecules was studied, in particular MS, an another biogenic VOC and also a Chemical Warfare Agent simulant, with boiling point over 200 °C (cf table S1). The sample was prepared at 1.9 ppm as described in the experimental part and was sampled during 60 s. The µPC desorption was performed at 250 °C during 20 s and a gradient from 90 °C to 180 °C with a 68 °C min⁻¹ ramp

was applied to the µGC, 30 s after the beginning of the µPC desorption.

As shown in the figure 10, in this case, FCB thermal regulation appeared necessary: a minimum temperature of 70 °C had to be imposed to be able to detect the MS with the µTCD. Heating of the FCB is activated after the sampling, so that the trapping of analytes on the Tenax remains effective, and before the µPC desorption and the analytes injection towards the µGC and µTCD. FCB temperature setpoint is reached in 8 min. Noteworthy, the MS is never detected on the FID, which is consistent because there is no heating provided for the connection between the µTCD and the FID detector.

By considering the MS peak height divided by the baseline noise (3σ) measured in a flat area (0.005 mV), a LOD of the order of 44 ppb and a LOQ of the order of 147 ppb are estimated for 30 s sampling.
<figure><img src="image_13.png" /><figcaption>**Figure 10.** Analysis with 60 s sampling of methyl salicylate sample at 1.9 ppm in dry nitrogen; up: temperature monitoring of µPC, µGC and FCB components with the FCB heated at 70 °C; below: chromatograms obtained after baseline subtraction with or without FCB heating, including the µGC thermal gradient.</figcaption></figure>

**4. Conclusions**

We have demonstrated the feasibility of interconnecting the various MEMS components of a GC-based analytical system for gas mixture analysis using a single micro machined FCB. This approach enables the development of a compact, flexible, and robust core system for which components can be easily assembled and exchanged. The analysis of several representative gas mixtures, with boiling points up to 220 °C, has been successfully demonstrated. Indeed, thanks to the possibility of heating the FCB easily and quickly, it is possible to carry out the analysis of relatively heavy molecules, which constitutes a real advantage and is a requirement for many real applications.

Future work with further integration of pumps and valves as well as control electronics is required to optimize the overall footprint of the complete system. In addition, improving the performance of µGC columns will lead to an improvement in both resolution and sensitivity. Finally, the FCB design could be further refined to optimize the power consumption required for interconnection heating.

**Data availability statement**

The data that support the findings of this study are available upon reasonable request from the corresponding author.
Supplementary data available at https://doi.org/10.1088/
1361-6439/ae1e88/data1.

Acknowledgment

The authors thank N. Verplanck and A. Keiser for their help in
the conception of the first version of the FCB.

This work has been sponsored by the French joint-
ministerial CBRN-E R&D Program.

Conflict of interest

The authors declare that they have no conflict of interest.

Author contributions

Florence Ricoul ID 0000-0003-3359-9497

Conceptualization (lead), Funding acquisition (lead),
Investigation (lead), Methodology (lead), Project
administration (lead), Supervision (lead), Validation (lead),
Visualization (lead), Writing – original draft (lead), Writing –
review & editing (lead)

Jean-Francois Beche

Conceptualization (supporting), Investigation (supporting),
Methodology (supporting), Resources (supporting),
Supervision (supporting), Writing – original
draft (supporting), Writing – review & editing (supporting)

Mahfod Benessalah

Investigation (supporting), Resources (supporting), Writing – original draft (supporting), Writing – review & editing (supporting)

Stéphane Caplet

Conceptualization (supporting), Investigation (supporting), Methodology (supporting), Supervision (supporting), Writing – original draft (supporting), Writing – review & editing (supporting)

Murielle Jurdit ID 0009-0007-0458-679X

Conceptualization (supporting), Funding
acquisition (supporting), Investigation (supporting),
Resources (supporting), Validation (supporting), Writing –
original draft (supporting), Writing – review &
editing (supporting)

Emilie Lefrancois ID 0000-0002-8959-7848

Investigation (supporting), Resources (supporting),
Software (lead), Writing – original draft (supporting),
Writing – review & editing (supporting)

Alexandre Teulle ID 0000-0001-6510-8731

Conceptualization (supporting), Investigation (supporting),
Resources (supporting), Writing – original draft (supporting),
Writing – review & editing (supporting)

Jean-Baptiste Tissot

Investigation (supporting), Resources (supporting),
Supervision (supporting), Writing – original
draft (supporting), Writing – review & editing (supporting)

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