Overcoming the Contamination of Polychlorinated Biphenyls in Water with Automated Solid Phase Extraction

Polychlorinated Biphenyls, or PCBs, are a global contamination problem. These chemicals are highly stable and, therefore they last for a long time in the environment. This means that PCBs are likely to bioaccumulate across the food chain, and therefore, a considerable amount of research and regulations have been devoted to their analysis.

Several environmental testing laboratories perform studies to determine PCBs in aqueous samples. Conventional methodologies usually involve manual separatory funnel or continuous liquid-liquid extraction (CLLE) of water samples using dichloromethane.

The resultant extract is dried using exclusively synthesized anhydrous sodium sulfate, then concentrated via an evaporation step, solvent exchanged to hexane, and finally examined using traditional split or splitless GC-ECD. Such techniques use huge quantities of solvents, are labor-intensive, and need contaminate-free glassware.

Environmental testing laboratories have faced demands to boost sample throughput, achieve reproducible outcomes, reduce sample turnaround times, and offer lower detection limits. In response to this, Horizon Technology has designed an automated solid phase extraction (SPE) instrument called the SPE-DEX^® 4790.

The SPE-DEX^® 4790 units available from Horizon Technology are programmable, multipurpose automated SPE systems that can directly process aqueous samples from their original containers. Once each SPE-DEX^® 4790 unit is started, it sequentially supplies all the required solvents to precondition the sorbent material inside the SPE disk, passes the water sample via the disk, and, following a preset air-dry time, isolates the retained analytes from the disk into a collection vessel by using the needed quantities of solvents.

Moreover, the SPE-DEX^® 4790 is capable of handling a broad range of initial volumes of water samples, and through this technology, users can regularly extract using anything from 40 mL to 8 L water samples.

The objective of this analysis was to design a rapid and stringent sample extraction and cleanup method to determine PCB congeners in aqueous samples as low as ng/L (PPT). The technique should also be able to extract Aroclor PCBs and finish all extractions with minimum consumption of organic solvents.

Northeast Analytical (NEA) has volunteered to assist Horizon Technology in its goal. NEA employs an altered congener-specific analysis that uses a GC/ECD fitted with a DB-1 capillary column. Such a technique uses a mixed Aroclor standard (Aroclor 1232/1248/1262 in 25:18:18 ratio) for calibration based on the Green Bay Mass Balance technique.

The Horizon Technology SPE-DEX^® 4790 and Envision^® Controller. Image Credit: Biotage

Instrumentation

• TurboVap LV
• JT Baker: Bakerbond Speedisk™ DVB (50 mm)
• Horizon Technology
  • SPE-DEX^® 4790
  • Envision^® Controller
• J&W Company, DB-1 ms, 30 m x 0.25 mm ID
• Aroclor 1242 Stock Standard at 990 μg/mL in hexane
• GC with ECD
• Mixed Aroclor Stock Standard at 62.7 μg/mL
  • Contains Aroclor 1232:1248:1262 in the ratio of 12:18:18
  • Aroclor 1232 concentration: 25.7 μg/mL
  • Aroclor 1248 concentration: 18.6 μg/mL
  • Aroclor 1262 concentration: 18.4 μg/mL
• Internal Standard at 202 μg/mL
  • octachloronaphthalene (OCN)
• Surrogate Stock at 100 μg/mL in hexane
  • 2,2′,3,3′,4,4′,5,6,6′-nonachlorobiphenyl

Method summary

To extract PCBs from a water matrix, the process was designed based on EPA-approved solid phase extraction (SPE) technique, called SW846 3535, which uses 1 L of sample and below 50 mL of solvents, methylene chloride, and methanol.

1. The SPE-DEX^® 4790 units are purged.
2. One-liter bottles are filled with DI (18 megaohms) water.
3. The samples are acidified using 1:1 sulfuric acid, and mixed thoroughly until the pH is 2.
4. A new DVB disk of diameter 50 mm is then installed onto the SPE-DEX^® 4790 extractor platforms.
5. The required compounds are spiked long with surrogates into the samples.
6. A piece of foil is then placed over the mouths of the sample bottles and screwed on the cap adapters.
7. The sample bottles are inverted and installed on the extractor units.
8. A 40 mL collection vessel is installed onto the extractors.
9. The extractors unit is started using the technique represented in Table 1, programmed into the Envision^® Controller.
10. After around 20 minutes, the resulting extract (must have two layers, hexane and acetone/water) is collected.
11. The top layer (hexane) is then transferred to a clean 60 mL VOA vial.
12. The water/acetone mixture is washed thrice with hexane (around 5 mL), and hexane is then added to the extract in the 60 mL vial.
13. The extract is concentrated using a TurboVap LV and brought to a final volume of 5 mL.
14. Sample cleanups of sulfuric acid, florisil, and mercuric precipitation are performed.
15. The extract is examined using GC/ECD.

Table 1. Extraction Method. Source: Biotage

Results

NEA employs two GC/ECD methods to analyze PCB Congeners on a regular basis. Such techniques are both congener-specific determinations, which use a high-resolution fused silica capillary chromatographic column. The two analytical techniques have been applied to samples extracted using the Horizon Technology SPEDEX^® 4790.

The first technique is based on the Green Bay Mass Balance Study analytical method. This approach will effectively isolate 116 or more peaks denoting 209 PCB congeners from the mixed Aroclor standard (Aroclor 1232/1248/1262 in 25:18:18 ratio) employed for calibration.

A major component of this technique is the significance placed on the chromatographic separation that should be achieved for this congener specific method. This enables an almost complete profile of environmentally occurring PCBs.

The second technique is a modified SW846-8082 Comprehensive Quantitative Congener Specific (CQCS) method developed for PCB analysis, which establishes all 209 PCB congeners.

The 209 congeners are quantified using 146 chromatographic peaks through a mathematical deconvolution for those that co-elute at the time of GC analysis. PCB congeners that occur at trace levels (that is, <0.05 weight percentage) or not detected in Aroclor formulations (around 62 congeners) can be reported by this technique.

This technique has been developed to quantitate the total amount of PCBs present in samples resulting from Aroclor type distributions as well as degraded, weathered, or non-Aroclor-like distributions.

Visual determination of Aroclor patterns can be achieved in certain cases through chromatographic comparison of samples with reference standards. This method provides a total amount of PCBs present in the sample.

It must also be mentioned that in the case of environmental samples that typically contain Aroclor-based PCB contamination, non-Aroclor congeners, which co-elute with Aroclor congeners, are assumed as absent.

Table 2 shows the outcomes of this testing, illustrating the method detection limits (MDL) and also the reporting limits (RL) for two varied initial sample volumes. The outcomes demonstrate that this technique is capable of achieving low MDLs of 9.34 ppt for 1 L samples and 1.06 ppt for 8 L samples.

Table 2. MDL and RL Values for PCB Congeners. Source: Biotage

*Cells with bold values indicate supplemental congeners not included in summations.

Conclusions

In this article, a total of 112 chromatographic peaks were identified, comprising 209 PCB congeners in different ratios. This enables a virtually complete profile of environmentally occurring PCBs and demonstrates that the Horizon Technology SPE-DEX^® 4790 automated unit is the best choice while conducting this kind of analysis.

SPE is similar to the more conventional techniques of continuous liquid-liquid extraction (CLLE) and separatory funnel shaking. But the automated SPEDEX^® 4790 method decreases the time required for a batch of samples by as much as 50% of its conventional counterparts.

Additionally, the quantity of solvent used and the number of technicians are decreased significantly. All these factors imply that a laboratory can achieve considerable savings while using the SPE-DEX^® 4790.

About Biotage

Biotage offers solutions, knowledge, and experience in the areas of analytical chemistry, medicinal chemistry, peptide synthesis, separation and purification. Customers include pharmaceutical, clinical and biotech companies, companies within the food industry and leading academic and government institutes. The company is headquartered in Uppsala and has offices in the US, UK, China, S. Korea, India, and Japan. Biotage has approx. 460 employees and had sales of 1,101 MSEK in 2019. Biotage is listed on the NASDAQ Stockholm.

Aim

Biotage is a global Life Science company that develops innovative and effective solutions for separation within organic and analytical chemistry, as well as for industrial applications. We help shape the sustainable science of tomorrow and our future society for the benefit of humankind. Our mission is to help our customers to make the world more sustainable, healthier, and cleaner.

Customers

The company has a strong customer base of industry and academic partners, which include the world’s top 20 pharmaceutical companies and prestigious academic and government institutes such as the US National Institutes of Health, the US Centers for Disease Control and Prevention and the Karolinska Institute in Sweden.

Biotage products are used by public authorities, academic institutions, contract research and contract manufacturing organizations, as well as the pharmaceutical and food industries. The Biotage products rationalize the workflow of customers and reduce their impact on the environment, for example by using a lower volume of solvents. Customers use Biotage products e.g. in their development of new medicines and to analyze samples from hospital patients, in forensic laboratories, or for the analysis of environmental and food samples. Biotage also offers products to remove undesired substances from, for example, pharmaceuticals during the manufacturing process.

Locations

Headquartered in Uppsala, Sweden, Biotage AB also has facilities in Lund, Sweden; Charlotte, NC, USA; San Jose, CA, USA; Salem, NH, USA; Cardiff, UK; Bundang, S. Korea; New Dehli, India; Tokyo and Osaka, Japan; and Shanghai, China.

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