Overview

M8250SIM analyzes samples for 1,4-dioxane specifically, but at a much lower concentration than regular 8260.

There is a separate SOP for this method that you need to read before you perform this analysis. You also need to run IDOC (4 LCS) before analyzing samples.

Setting Up

Because SIM is such a sensitive method, we set up the GC/MS to selectively scan for specific ion abundances. As a result, trying to analyze BFB using the same settings as the QC/samples would yield no peaks. To solve this, we have a standard scan method used specifically for tune checks before starting the sequence for the day. This scan method shares the same name as the method name but with an A appended to it.

Ex: SIM method for analyzing QC/samples is named VOF5J06. The scan method for analyzing BFB is named VOF5J06A.

It’s very important that we don’t overwrite the scan method if we need to make adjustments to the ICAL. This isn’t usually an issue, but it’s something to keep an eye out for nonetheless.

QC Prep

We have specific stock standards we use to prepare 1,4-dioxaneSIM standards. They’re in a plastic rectangle box labeled SIM alongside the standards for TCPSIM. Check the standard logbook for instructions on how to prep.

To spike 1,4-dioxane (water):

• 25mL DI water
• 5.0uL 1,4-diox IS/SS
• 5.0uL 1,4-diox (1°)
• 5.0uL 1,4-diox (2°)

To spike 1,4-dioxane (soil):

• 15mL DI water in 5.0g NaHSO4 (if samples are preserved in SoBi)
• 15mL DI water (if samples are frozen)
• 4.0uL 1,4-diox IS/SS
• 4.0uL 1,4-diox (1°)
• 4.0uL 1,4-diox (2°)

For SIM, the percent recovery for target analytes needs to be within 20% of expected value. Higher can be tolerated, but analytes cannot be lower than 20%.

Running samples

Sometimes, a sample will have heavy matrix interference so integrations aren’t picking up correctly. Make sure you check the peaks for all compounds to see if they’re being improperly integrated or completely missing. If you’re not sure whether a sample needs to be run at a dilution, ask Diem.

For soil samples, sometimes the samples have extreme matrix. Ask Diem when you see anything that looks strange.

ICAL

Use a previous 1,4-dioxane ICAL as reference for spiking. You don’t need to use SmartWater when running M8260SIM ICAL so I just use the sink water.

Unlike 8260, we only run eight levels for ICAL. This means we finish running the ICAL sooner, but it also means we have less wiggle room when processing the ICAL. Check the ICAL carefully when it’s done. If you fail to run MDL for a quarter, you need to run LOD/LOQ in every run for that method (this happens most often with 1,4-dioxane soil).