Soil analysis labs often process hundreds of soil samples per day, performing various physical, chemical, and biological tests. The motivation for soil chemical analysis varies from maximizing yields and profits at the local level to maintaining food security at a more global scale. Soil sample results enable farms to identify and replenish the specific nutrients needed by a given area of land. Therefore, data generated from soil quality assessment methods need to be accurate and reliable.

Strategies to simplify soil testing steps can relieve pressure on analysts and support data quality in high-volume laboratories, improving lab efficiency and throughput.

Soil testing standards

Soil chemical analyses provide information on nutrient levels that direct investment and use of fertilizer. These soil tests might also reveal contamination from local industrial activity or disposal.

Following soil testing standards, protocols, and guidelines from national and international organizations helps soil analysts maintain high data quality. These organizations include the US Environmental Protection Agency (EPA) and the Food and Agriculture Organization of the UN.

Bottlenecks in soil testing methods

Two key methods for trace metal analysis in soil samples are flame atomic absorption (FLAA, EPA method 7000B) and inductively coupled plasma atomic emission spectroscopy (ICP-AES, EPA method 6010D). The preparative steps for both of these soil testing methods are time-consuming.

FLAA enables analysis of multiple elements simultaneously, which can save some time as compared to ICP-AES. However, the inherent heterogeneity of soil demands time-consuming grinding, acid digestion, and filtration (EPA method 3050B) to generate homogenous liquid samples.

When testing hundreds of soil samples per day, the risk of contamination during these preparative steps is high. Trace elements might transfer from gloves and other samples to the immediate sample or apparatus. In some cases, the filter paper is itself acid digested to maximize the recovery of certain trace elements, such as lead and nitrogen. Rushing these preparative steps increases the risk of inconsistent and inaccurate results.

Simplifying methods for assessing soil quality

There are alternative soil testing techniques, such as X-ray fluorescence spectroscopy (XRF), which require fewer preparative steps. However, comparisons indicate that XRF cannot match the sensitivity of ICP-AES, making the latter the preferred method.

To simplify the workflow, analysts can target the filtration step of soil sample preparation. Although filtration itself plays a small part in the overall method of soil testing, during peak periods, analysts are likely to hand-fold hundreds of circles of filter paper each day. A simple switch to pre-folded filters in place of flat circles or sheets negates the need for manual folding, saving significant time in sample preparation.

In addition to improving overall lab efficiency, reduced paper handling reduces the risk of cross contamination. The multiple benefits of this single modification in soil testing technique can lead to improved data quality and throughput.

Do pre-folded papers comply with soil testing standards?

In addition to quantitative ashless grades, Whatman laboratory filtration products offer a range of ready-to-use, pre-folded filter papers made of the same high-quality materials that comply with soil testing standards and protocols.

Try our Whatman Filter Selector App to find out if you are using the most appropriate filtration solution for your samples. To discuss any challenges you are facing, please contact Cytiva's Scientific Support.

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