PFAS Delay column

Per- and Polyfluoroalkyl Substances (PFAS) is a general term for organofluorine compounds. It is known to be low in degradability and persist in the environment for a long time. Their toxicity and environmental pollution have attracted global attention and research continues. The solid-phase extraction-LC/MS/MS method has been used for the analysis of PFAS in drinking-water under EPA Methods 537.1 and 533. Because some countries and regions have low targets, it can be difficult to achieve stable, sensitive and accurate measurements that meet the required levels. Care must be taken to minimise the effects of blanks eluting from fluorinated resins such as PTFE, which are commonly used as components in LC systems. A known countermeasure, is to delay the elution time of the blank peak by connecting a Delay column packed with a C18 material before the autosampler, and to shift the retention time from the peak derived from the sample. However, it is difficult to sufficiently increase the difference between the two retention times with a conventional C18 column. Due to the relationship between the rise in pressure and the gradient delay time, column sizes are limited. Therefore, in order to obtain a stable PFAS analysis, we have developed a new Delay column. Our Delay column is packed with high-purity activated carbon beads. To speed up solid phase extraction, you can also scale down the amount of sample water, the size of the SPE cartridge and the amount of the elution solvent.

Methods

The Delay column is packed with high-purity spherical activated carbon in LC column hardware. The analysis column is a InertSustain C18-HP 150 mm x 2.1 mm, 3 μm (GL Sciences, Inc.). The standard sample was prepared by diluting a PFAS 21 Mixture Standard and adding it to the sample water, 13 mixtures of MPFAC-C-ES were added as an external standard. Solid phase extraction was used. The SPE column is a InertSep MA-2 250 mg (GL Sciences, Inc.) packed with a methacrylate polymer with a weak anion exchange group (Diethyl amine) was introduced.

Results

By using our Delay Column for PFAS, packed with high-purity activated carbon, it is confirmed that the peak to be analysed and the blank peak were sufficiently separated. In the concentration, using our SPE column, InertSep MA-2, all of the PFAS 21 components from C4 to C18 were eluted with 5 mL of 0.1% ammonia methanol. As a result of the recovery test and the extracted tap water samples, linearity was 0.99 or more in the range of 1 - 20 ng/L, and repeatability at 5 ng/L was 16% or less.