Frequently Asked Questions

Topics: General / Technical / Logistical / Ordering / Past Research

What is the benefit of using PRS™-probes compared with simply buying raw ion-exchange membrane?

The PRS™-probes are much simpler to use in situ than raw ion-exchange membrane. Not only are the PRS™-probes easier to insert and remove with minimal disturbance, but it is also easier to guarantee proper contact between the ion-exchange membrane and soil. The PRS™-probes are easily labeled, therefore, facilitating the tracking of samples among different treatment plots, with less chance of sample mix-up. The plastic casing of the PRS™-probe also makes it easier to clean the ion-exchange membrane, thereby, reducing the potential for residual soil contamination during elution.

There are numerous industrial suppliers of raw ion-exchange membrane; however, these wholesalers are NOT suppliers for soil science-related applications. Instead, they provide material primarily for industrial applications ranging from water purification to separating various antibiotics from fermentation broths. As a result, there is no technical support provided, let alone soil science-related expertise with which to properly apply the ion-exchange technology to your research and/or satisfy your trouble-shooting concerns. Ultimately, you will be left with developing your own protocols or following those from the literature, which may not be appropriate for your particular situation.

Notwithstanding the obvious logistical advantages of using PRS™-probes compared to raw membrane, there is the added benefit of readily available qualified technical support via a toll-free technical support line (1-877-978-1777) or e-mail. Depending on your familiarity with the ion-exchange technology, this may be the most important advantage of using PRS™-probes. A typical consultation with a Western Ag Innovations R&D Coordinator, prior to leasing PRS™-probes, consists of discussing the necessary logistics (i.e., experimental design, number of PRS™-probes required per samples, placement, length of burial, analysis protocols, etc.) involved when using the PRS™-probes. Every year Western Ag Innovations has an exhibitor booth at the Annual ASA/CSSA/SSSA Meetings where we showcase the latest research using the PRS™-probes.

Western Ag Innovations also has extensive analytical capabilities (i.e., colourimetry, ICP, HPLC, and GC-Mass Spec) for analyzing the PRS™-probe eluate for a wide range of nutrients and ionic species. Western Ag Innovations prides itself on customer support; therefore, regardless of the lease agreement selected, contact one of our R&D Coordinators with any questions, concerns, or comments.

Are all ion-exchange membranes similar?

NO, all ion-exchange membranes are not created equal. Homogeneous-type ion-exchange membrane is far superior to the more common older heterogeneous-type ion-exchange membrane. Unlike homogeneous membrane, heterogeneous membrane has an irregular distribution of ionic groups and is susceptible to loss of ion-exchange capacity due to shedding, surface abrasion, or tearing. This is true especially after continuous wetting/drying cycles. Depending on the soil type and burial conditions, with each successive use, the ion-exchange capacity of heterogeneous-type membrane changes, thereby adding unnecessary variability to your data. Conversely with homogeneous-type membrane, mechanically shaking homogeneous-type membrane with sand and gravel for seven successive 24-hour periods has no effect on maximum ion-exchange capacity. Even tears are of little concern with homogeneous-type membrane, because the edges of torn membrane are capable of adsorbing ions.

In addition, heterogeneous membrane may be prone to nutrient carry-over effects because of its thicker, sandwiched backbone makeup. For example, in high NO₃^- supplying soils, there probably will be extensive NO₃^- diffusion into the interlayer of the heterogeneous membrane. In order to ensure that all of the NO₃^- is desorbed prior to the next burial, a second elution step should be performed along with using a stronger acid (i.e., 2N HCl). Otherwise, residual NO₃^- carried over into subsequent measurements will confound the results and affect comparisons among treatments.