Perform Data Treatment for Chlorinated Paraffins in 10 Seconds?

Editor’s Note: Dr. Thomas Stegemann, GC, GC-MS Application Specialist, Germany, contributed to this article.

If Chlorinated Paraffins (CPs) are a challenge in your lab, you know how time-consuming obtaining reliable data is.

Why is it so complex?

It all starts with the actual legislation on the determination of CPs in either drinking water, surface water, groundwater, sediment or wastewater. There are actually different types of legislation to consider. The first is directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000, which established a framework for community action in the field of water policy. This has been incorporated into local legislation:

• ISO 12010:2019 Water quality — Determination of short-chain polychlorinated alkanes (SCCP) in water — Method using gas chromatography-mass spectrometry (GC-MS) and negative-ion chemical ionization (NCI)
• ISO 12010:2019; DIN EN ISO 12010:2019

Common to all of those is a very complex calibration where the concentration is described by a resulting area of the calibration. The approach is a multiple linear regression based on the formula and figure in Figure 1.

CPs are complex mixtures of polychlorinated n-alkanes. The chlorination degree of CPs can vary between 30 and 70 wt%. CPs are subdivided according to their carbon chain length into short-chain CPs (SCCPs, C_10–13), medium-chain CPs (MCCPs, C_14–17) and long-chain CPs (LCCPs, C_>17). Depending on chain length and chlorine content, CPs are colorless or yellowish liquids or solids. [1]

In recent decades, the environmental presence and ecological risks of CPs, an emerging class of organic halogen compounds, have received increasing attention worldwide.

Short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) constitute the important CPs of considerable concern.[2]

Production of CPs for industrial use started in the 1930s,with global production in 2000 being about 2 million tons.Currently, over 200 CP formulations are used in a wide range of industrial applications, such as flame retardants and plasticizers, as additives in metalworking fluids, in sealants, paints, adhesives, textiles, leather fat and coatings.

Short-chain CPs are classified as persistent and their physical properties imply a high potential for bioaccumulation. SCCPs are classified as toxic to aquatic organisms, and carcinogenic to rats and mice.

Therefore, it was concluded that SCCPs have PBT and vPvB properties, and they were added to the Candidate List of substances of very high concern for authorization under REACH Regulation. [1]

Because of the enormous number of positional isomers that characterize their mixtures, the analysis of this class of pollutants is very difficult to perform. Beside this, the lack of certified reference materials poses a problem for the assessment of the quality assurance/quality control of any analytical procedure.

The scientific community does not currently agree on any analytical reference method, although the monitoring of short-chain chlorinated paraffins has already started in order to comply with the Water Framework Directive of the European Union, which addresses water quality.

This method is for the quantitative determination of the sum of short-chain polychlorinated n-alkanes. These are also referred to as short-chain polychlorinated kerosenes (SCCPs) and have carbon chain lengths from n-C10 to n-C13, inclusive, in mixtures with chlorine mass fractions (“contents”) between 50 percent and 67 percent, comprising approximately 6,000 of the approximately 8,000 congeners.

This method is applicable to the determination of the sum of SCCPs in unfiltered surface water, groundwater, drinking water, and wastewater by gas chromatography-mass spectrometry with electron capture after negative chemical ionization (GC-ECNI-MS).

Depending on the performance of the GC-ECNI-MS, the concentration range of the method is from 0.1 μg/l or below 10 μg/l. Depending on the wastewater matrix, the lowest detectable concentration is estimated to be > 0.1 μg/l.

The sum of SCCPs analyzed in this way includes the variety of SCCPs with different chlorine content and C-number distribution patterns found in technical mixtures as well as in the environment.

The main sample preparation starts with Liquid-Liquid-Extraction. This can be done manually fora low number of samples, or can be fully automated and integrated into a workflow using a RSH SMART robotic system. Here is a look at this process:

• Add 10 ml of the extracting agent n-heptane to the bottle containing the sample and internal standard and shake or stir thoroughly for about two hours to perform the extraction directly in the sample bottle.
• Wait until the two phases separate, and then use the separator to collect the organic extract in a separate test tube.
• Transfer the solvent from the test tube to the concentrating device or concentrate it carefully (at a temperature of 40°C) to about 1 ml using a gentle stream of nitrogen.
• Weigh the empty bottle and cap to the nearest gram. The volume of extracted water and the concentration of the internal standard in the water must be calculated.

In some cases, depending on the matrix (wastewater), there are additional cleanup steps necessary, such as Gel Permeation Chromatography (GPC).

Fig.2 shows a self-explaining chromatogram of SCCPs. There is no specific separation of single peaks. The congeners elute as “humps.”

The mass spectrometry behind it is the following, explained in the DIN and EN method.

In ECNI mass spectrometry of SCCP, the degree of fragmentation is relatively low compared to techniques such as electron impact ionization and positive chemical ionization.

In ECNI-MS, the predominant m/z values are [M-Cl]-, [M-HCl]- and [M+Cl]-.

No molecular ion was detected; the major ions and their associated chlorine isotopes are m/z = 345 [M-Cl]-, m/z = 344 [M-HCl]-, and m/z 415 [M+Cl]- along with lesser amounts of m/z 309 [M-Cl-HCl]- or [M-HCl-Cl]-, m/z 308 [M-HCl-HCl]-, and m/z 272 [M-HCl-HCl-HCl]-.

After confirming these fragmentation mechanisms in the ECNI-MS used, there are different m/z used for the specific groups of CPs.

Perform the measurement in single ion mode with four selected mass fragments i.e., m/z 375, m/z 411, m/z 423 and m/z 449. The peak areas of the two masses, m/z 375 and m/z 423, are used in the multiple linear regression to calculate the sum of SCCP. The peak areas of m/z 411 and m/z 449 are used for additional identification. This specific selection was made using data analysis to capture the sum of SCCPs from a wide variety of SCCP mixtures found in the environment.

Figure 2: Chromatogram of SCCPs.

What would be the “holy grail” and how can you accomplish this?

Today you need to move data for quantitation into another external program. That process generates issues with:

• Data security
• File track
• Additional time (manual process)
• Report-out is more complicated, additional step à automation?

Holy grail: One stop S/W solution that reports into an internal data system in a fully automated sequence.

And now the question is, how do we get there?

The Thermo Scientific™ Trace 1610 GC, in combination with the new Thermo Scientific ISQ 7610, is the GC-MS system of choice to generate the CP data in NCI mode. Since the matrix can be dirty even after special cleanup (in the case of sediment or wastewater samples), the ISQ 7610 offers a very nice feature. The ion source can be changed without evaporating the system. This technology is called Vacuum Probe Interlock (VPI) and the picture in Fig. 3 shows the new mass spec. The time saving for the ion source maintenance is reduced by 98 percent and you can remove the source and measure again after 10 minutes. As a comparison, on a “normal” system it will take between three and four hours to shut down the vacuum and replace your ion source.

Figure 3: New Trace 1610 GC and ISQ 7610 with VPI option.

Analytical parameters

GC-MS parameters

It can be this easy: Use Chromeleon CDS with plug-in, stay in the same S/W platform, and within 10 seconds the quantification is performed and results are ready to export. Results can be exported into the local LIMS system for data reporting and/or into Microsoft Excel for control. The process is fully automated and the results are the same in either Microsoft Excel or Chromeleon™ Chromatography Data System (CDS).

Figure 6: Comparison of results Microsoft Excel and Chromeleon CDS.

With innovative solutions we reach the holy grail in the analysis of CPs. It is that easy and takes only 10 seconds!

You don`t believe it can be done in 10 seconds? Watch this video and you will be impressed how easy your life will be.

Watch the video in English.