Enhancing Organochlorine Pesticide Extraction: A Comparative Study of NanoPak-C All Carbon and Graphitized Carbon Black

Our previous blog discusses the differences between NanoPak-C All Carbon microbeads and other graphitic carbon media, focusing on their manufacturing processes, composition, and structure.

Figure 1. Structural depiction of some common organochlorinated pesticides (OCPs).

The differences in chemical composition and physical structure significantly influence how analytes interact with the stationary phase, which is essential for effective separation. This, in turn, impacts the recovery of analytes during solid-phase extraction (SPE) procedures. Our recently published white paper highlights this point.

In the white paper, we compare the recovery rates of 15 organochlorine pesticides (OCPs) (Figure 1) using NanoPak-C solid-phase extraction (SPE) with those obtained from commercially available GCB SPE media. For the SPE procedures, we utilize very small quantities of environmental samples, specifically 100 mg of soil and 200 µL of river water.

We found that we could detect all 15 pesticides in soil and river water samples using gas chromatography-mass spectrometry (GC-MS) with extraction columns filled with All Carbon microbeads. The average amount recovered ranged from 1 to 90 parts per million (ppm) (µg/kg). However, after using different extraction columns made of GCB, we could find only two out of the fifteen pesticides in the soil samples and none in the water samples.

Our results do not prove that our NanoPak-C All Carbon media are better than graphitized carbon blacks (GCBs). The method we optimized may not work well for GCBs. However, we suggest that the differences in how well the All-Carbon microbeads and the graphitized carbon microbeads recover the analyte come from the way the analyte interacts with the stationary phase.

And the way they interact depends on their chemical composition and structural differences (Figure 2). Carbon

Figure 2. Comparison of structure and composition of NanoPak-C All Carbon media and graphitic carbon black (GCB).

microbeads are small, round structures made of porous carbon. They have a network of sp² carbon bonds, which originate from natural graphite, and sp³ carbon bonds, which are formed with the help of a crosslinker. On the other hand, GCBs are solid carbon materials. They are created by heating carbon-rich materials at extremely high temperatures (2000-3000°C). This process makes them highly ordered and crystalline, similar to graphite. GCBs have an irregular shape and are usually larger than 40 micrometers.

This study builds on a previous one that aimed to create a reliable onsite method for solid-phase extraction (SPE) for small environmental samples. The goal of that study was to simplify the preparation of SPE samples directly at the location where they were collected, rather than sending them to a laboratory.

Routine solid-phase extractions (SPEs) require large sample sizes, necessitating the use of more materials, including organic solvents and specialized labware. Also, moving samples to testing labs can lead to contamination, degradation, or loss of important substances. These issues can lead to testing errors and increase costs. To avoid these problems, conducting on-site sample extraction could be helpful. Techniques such as solid-phase microextraction (SPME) are often employed for this purpose. However, there aren’t many SPE methods available to extract organochlorine pesticides (OCPs) from small environmental samples, such as a few milligrams of soil or a few milliliters of water.

Download our white paper here.

Contact us to discuss how we can support your SPE or liquid chromatography analysis. Please email us at inquiry@millennialscientific.com, call us at 855-388-2800, or fill out our online form.