Microchip Analytical System for Inexpensive, Real-Time Aerosol Chemical Speciation

Atmospheric aerosols, also known as particulate matter (PM), play important roles in weather, climate and human health. Aerosol number, size and chemistry can all exhibit high degrees of spatial and temporal variability, thereby increasing the need for highly time-resolved analyses obtained over extensive time periods (weeks to years). Instrumentation for monitoring the physical characteristics of aerosols, such as total number, size distribution, mass and albedo, are well developed and robust enough for deployment in routine-monitoring networks. However, many of these physical parameters are governed by the chemistry of the particles. Aerosol chemistry plays a critical role in human health, climatic impacts and source apportionment, further increasing demand for improved aerosol chemistry instrumentation in settings ranging from research to industrial process monitoring. Unfortunately, instrumentation for monitoring aerosol chemistry is not as mature as that of aerosol physics, particularly when real-time monitoring and affordability are important. MicroChemica, LLC, a technology-driven environmental-monitoring instrumentation company, is poised to provide a $20,000 system to address this market need. This system would provide real-time chemical speciation of aerosols with ~1 min time resolution, sub-µL sample volumes, detection limits below 0.1 µg m-3, the ability to monitor multiple species simultaneously, low consumable consumption (mLs/day), unattended operation for weeks, the ability to interface with existing steam-based aerosol collectors, and a consumables cost of ~$2,000/yr. MicroChemica anticipates a market of ~100 units/yr within 5 years as existing aerosol researchers migrate to using this technology. However, adoption by programs such as the lnteragency Monitoring of Protected Visual Environments (IMPROVE) would greatly increase market size.

In this project, to meet the need for improved real-time aerosol chemistry monitoring instrumentation, MicroChemica proposes to create a continuous-flow microchip electrophoresis (MCE) device for coupling to steam-based aerosol collectors because it is faster, cheaper and less complex than existing chemical speciation tools while providing equivalent and even better performance than traditional methods. For chemical speciation, MCE would replace ion chromatography (IC) at the steam-collector output. The MCE system would permit onsite, quantitative speciation of dominant inorganic ions in aerosols with 1-min temporal resolution. This temporal resolution is about 10 times faster than typical IC configurations. MicroChemica anticipates the final commercial cost of the system to be $20,000, which is 2-4 times lower than most IC systems with starting costs of more than $40,000. Operational costs also will be lower, with individual microchips having lifetimes of thousands of runs at a cost of ~$100 per microchip while consuming only milliliters of buffer per week. In contrast, typical IC columns cost $1,000-$2,000 and require liters of high-purity solutions for long-term analyses. MCE requires fundamentally less-complex instrumentation than IC, as only two high-voltage sources are needed to drive the system; IC requires a high-pressure pump, peristaltic pumps, and often a suppressor system. While IC requires a stationary phase that can foul with time, MCE uses open capillaries with no stationary phase. Preliminary results by MicroChemica’s collaborators at Colorado State University show sub-minute, fully resolved separations of aerosol-relevant analytes using MCE with detection limits equating to ~0.05 µg m-3 for inorganic aerosol species. Importantly, long lifetimes for both the basic instrumentation and the microchips have been demonstrated in field trials with related technologies under development for different industries with continuous runs exceeding 3 months.

Initially, the primary consumer for the proposed technology would be research laboratories that measure particulate matter composition. Most of these laboratories would be in universities and government agencies. The faster chemistry speciation would permit higher-resolution aircraft studies to be performed, and the lower cost and smaller footprint would encourage a larger number of fieldable instruments to be owned, both of which are motivations for these laboratoriess to pursue this technology. However, MicroChemica anticipates that the lower cost of the chemistry speciation could increase the size of the market, particularly in the area of widespread, routine monitoring by government and state agencies. The end goal is a product with a price point and ease-of-use that would make it amenable for routine-monitoring applications. One example is the IMPROVE network in the United States, which currently has 222 locations. A similar number of sites are also present in the European Union. Asian countries are also expanding aerosol-monitoring capabilities as well, with China being the largest potential client.

Overall, the benefits of developing and commercializing this technology stem from increased widespread monitoring of aerosol chemistry due to the less prohibitive cost compared to existing technology, improved spatial resolution in mobile monitoring units such as aircraft, and increased use of real-time aerosol chemical speciation technology. Potential benefits could include improved source attribution and aerosol modeling, higher resolution chemical information for evaluating ambient aerosols, and increased availability of real-time aerosol composition information.

There are numerous potential commercial partners for the proposed technology that fall into the categories of general analytical instrumentation companies as well as specialized aerosol monitoring companies. Because of the growing market for aerosol analysis, traditional analytical instrumentation suppliers like Metrohm have begun marketing equipment for aerosol analysis, including coupled Particle- Into-Liquid Sampler (PILS) and Monitor for Aerosols & Gasses in Ambient Air (MARGA) units, both with IC detection. Mr. Dekleva and Dr. Henry have previous engagements with Metrohm that will be pursued during platform development. Many commercial partners have been identified. Based on preliminary feedback and voice of customer research, MicroChemica anticipates strong market pull for this product.

The market for aerosol analysis equipment is hard to individually quantify, as it is part of the larger environmental analysis market. This latter market is currently estimated at $6 billion (according to Frost & Sullivan) with an annual growth rate of 5-6 percent. The aerosol analysis market segment represents a fraction of this total, but is growing at a faster than average rate because of the recognition in the last 2 decades of the importance of aerosol chemistry in dictating human and environmental health. MicroChemica’s potential buyers in this market include customers from academia, government research and regulatory facilities, and industrial entities. Industrial applications range from routine monitoring in remediation settings to industrial hygiene. Success of this technology could also lead to an expansion into environmental routine monitoring, such as the IMPROVE sites, and industrial applications, such as occupational monitoring at mines, which would also increase market size. Finally, this instrumentation will act as a platform technology that will be useful in many areas of environmental analysis, particularly water quality monitoring, with simple modifications to the interface.