The PRS™-probes greatly simplify the analysis of ion-exchange resins and a complete analysis protocol is shipped with the PRS™-probes to applicable researchers. Below is a brief summary covering the salient aspects of PRS™-probe analysis. For a schematic of the general protocol go to our Protocol section.

Note: These protocols are developed for the PRS™-probes ONLY and may not be appropriate for use with other ion-exchange materials, including other types of ion-exchange membrane.

As with any analytical procedure, it is essential to ensure that there is no contamination during the analyses. A method blank, which is a ‘clean’ PRS™-probe that was regenerated at the same time as the PRS™-probes being analyzed, can be included and analyzed with each sample batch. These method blanks are used to test for possible contamination during the PRS™-probe regeneration step, which will affect the nutrient supply rates.

Method blanks will be charged as samples if a researcher wishes to have them analyzed, pricing for blank analysis is the same as a Complete, N-only or Anion analysis. It is important to treat blank samples carefully when having them analyzed. Often blanks tend to get left in the bag after all PRS probes for samples are removed. Soil in the bag, dirty fingers and other factors can lead to variability and background noise on the blanks. Also, higher supply rate values on the blanks are know to occur when PRS probes have been stored in a dry state for extended periods of time. The reason for this is that the membrane shrinks on desiccation and causes the membrane to shed. This shedding may cause some cracking and add N to the sample as the anion membranes uses quaternary ammonium as the functional group for adsorption. However, the amount being leached or lost from the membrane matrix is small relative to the N economy in the soil. Therefore, it is important to treat method blanks carefully when using them in a study. Keep them relatively clean, and store them in moist refrigerated conditions for long periods of time to keep the membrane from drying. Do not touch the membrane with your fingers especially if they are dirty. Be sure to wash all blanks with the same water used on the field samples.

After removing the PRS™-probes from soil, wash off ALL residual material with de-ionized water. Hand scrubbing the adhering soil with a scrub brush and/or toothbrush while washing is usually necessary to remove sticky clay soil or silty films. It is very important to WASH, WASH, and WASH the PRS™-probes as thoroughly as possible. Incomplete washing will result in residual soil being eluted in addition to the ion-exchange membrane. Even a minute quantity of residual soil on a PRS™-probe will significantly increase the nutrient supply rates above the true values, thereby adding unnecessary variability. Residual soil also may create a cloudy eluate, which may cause problems with the analytical equipment. If it is not possible to get the PRS™-probes completely clean in the field, then it will be necessary to RE-WASH the PRS™-probes in the lab. The accuracy and precision of the PRS™-probes ultimately depends on the diligence performed during the washing phase. Please place PRS™-probes into new sample bags, which make up one analysis sample, after they have been thoroughly washed.

Note: if soil is visible anywhere on a PRS™-probe (i.e., ion-exchange membrane, plastic casing and handle, small cracks, etc.), it is NOT clean enough!!! ABSOLUTELY ALL SOIL MUST BE WASHED OFF OF THE PRS™-PROBE PRIOR TO ELUTION. A high-pressure backpack sprayer filled with de-ionized water is an effective tool for washing the PRS™-probes out in the field and can be ordered through Western Ag Innovations.