May 4, 20214 min read

Portable SPR for On-Site Testing of Environmental Contaminants

Updated: Oct 1, 2021

Introduction

Traditional methods for testing environmental contaminants are commonly done in centralized lab facilities, which require the collection, transportation, storage, and preparation of samples. These steps require time, and will certainly delay any proactive actions necessary to safeguard the environment and health of those who are directly impacted by the presence of environmental contaminants, for instance, residents whose main water source comes from water wells at risk of contamination. Having access to a mobile test platform is even more so important if the testing site is not easily accessible with regular transport from any centralized lab facility. In this case, having continuous, real-time monitoring can be a valuable asset in remote areas. This blog highlights the deployment of P4SPR™ to monitor RDX (1,3,5-trinitroperhydro-1,3,5-triazine) in groundwater near downgradient wells [1]. This research was conducted by Prof. Jean-François Masson’s research group at Université de Montréal.

Background

RDX (Figure 1) is an energetic material left on the ground following military exercises. It is not well retained in soil so it is often transported to ground and surface water by rainfall or snow melt. To ensure that the ground water is safe to use by the local population, the water must be tested, which is often done by HPLC-UV analysis, a method approved by the Environmental Protection Agency (EPA) known as EPA method 8330b [1]. This method relies on a large laboratory instrument which is normally located in a centralized lab facility. Thus, the samples must be carefully transported and stored before being prepared for analysis. In addition, pre-concentration and/or extraction, such as solid-phase extraction, might be required, which in turn lengthens the sample preparation time.

Normally, small molecules such as RDX would be difficult to detect with a SPR instrument due to its small size. However, a SPR setup based on a molecularly-imprinted polymer (MIP), bisaniline, with crosslinked gold nanoparticles was found to bind to RDX with high affinity [2]. Moreover, the use of MIP is ideal for field-deployed instrument as it is simple and less susceptible to environmental degradation, as opposed to using antibodies as binding receptors [3,4], for instance.

Figure 1. Structure of RDX (1,3,5-trinitroperhydro-1,3,5-triazine).

Highlights of Using P4SPR™ in the Field

The P4SPR and other equipment was brought to remote well sites via a sled (Lab-on-a-sled) or a SUV (Lab-in-a-Jeep) during both Canadian winter (Figure 2) and summer time (-20ᵒC and 30ᵒC) (Figure 3). The device was set up on a table or a mat with minimal overhead shelter such as tent to protect it from snow or rain. The device was powered by a laptop via a USB cable, and the laptop battery was backed-up by a generator.
It generally took 60-90 min from arrival on site to completion of SPR measurements. Experimental steps include:

1. Flushing and sampling well

2. Setting up equipment and instrument

3. Equilibration of P4SPR with water and uncontaminated water

4. Measuring sample

5. Recalibrating sensor

Since SPR sensing is sensitive to temperature, a calibration was performed on the P4SPR for RDX samples at different temperatures.
Continuous monitoring was also mimicked in the laboratory. Relative SPR signals were observed for each increasing RDX concentration for one day, which showed the potential of the P4SPR being used for continuous monitoring.
A comparison study was done between P4SPR (samples being analyzed onsite and in the lab) and the HPLC EPA method 8330b. The results obtained onsite and in the lab was accurate within 27%. The results agreed well with the samples that were analyzed using the EPA method.
The P4SPR was able to detect RDX concentrations in groundwater near the EPA threshold concentration of 2 ppb.

Figure 2. Photos of the P4SPR being deployed on the field in winter. Top: P4SPR and other equipment being pulled on a sled; Bottom: P4SPR being set up inside a tent.

Figure 3. Photos of the P4SPR being deployed on the field in summer. Top: The P4SPR was set up at the back of a Jeep. Bottom: Close-up of experimental setup inside the Jeep.

Conclusions

The P4SPR™ was deployed at a military training site to sample ground water for the detection of RDX using a MIP-coated sensor chip. Summer and winter conditions were tested on the instrument with success, with the setups being simple and experiments being fast to complete. The results obtained onsite and in the lab correlated well to samples analyzed by the HPLC EPA method 8330b. The authors also demonstrated the potential of the P4SPR to be used for onsite continuous monitoring. The use of a portable SPR instrument has the advantage of faster result turnaround time than the standard EPA method due to the lack of need to transport and store the samples, as well as eliminating some sample preparation steps.

More information

Please read the research paper to find out more experimental details and results.

The Affinité Advantage

Affinité Instruments’ P4SPR™ is a very user-friendly instrument that is equipped with a gold sensing chip can be tailored to accommodate all types of surface chemistries. In addition, samples do not need much sample preparation and can be directly injected into the instrument. The P4SPR™, compared to a traditional immunoassay such as ELISA, provides fast, real-time affinity and/or kinetic data.

Simplicity - Fast training, fast results

Versatility - Pharmaceutical, biosensing, assay development applications

Economy - Affordable, accessible

We help life science labs and biotech companies to do rapid assay development and characterization. Feel free to reach out to us about the expertise we offer at info@affiniteinstruments.com