Tekmar Talk Blog

This is the forth in our Troubleshooting series for VOC Analysis. 

• Part one is linked here, VOC Analysis Troubleshooting Part 1: How to Begin Troubleshooting
• Part two is linked here, Troubleshooting Part 2: No or low analyte response and carryover
• Part three is linked here: Elusion Issues and Moisture Control

Troubleshooting linearity and reproducibility issues in your systems can be difficult. Problems with linearity and reproducibility can make calibrating your systems frustrating, and if internal standards are varying, it can cause all other target compound to look unstable.

This is the third in our Troubleshooting series for VOC Analysis. 

• Part one is linked here, VOC Analysis Troubleshooting Part 1: How to Begin Troubleshooting
• Part two is linked here, Troubleshooting Part 2: No or low analyte response and carryover

Part three will discuss elusion issues and moisture control for VOC analysis.

A typical analysis schedule for the Fusion TOC analyzer starts with a cleaning procedure. The cleaning procedure confirms cleanliness of the system and will ensure low instrument background. Also, tracking cleaning procedure results from day to day will give an indication if any contamination issues may be occurring. It is imperative to have low background and no contamination to achieve superior low-level TOC results.

The Fusion Total Organic Carbon (TOC) analyzer is equipped with TOC Teklink, a fully optimized graphical user interface.

This blog will demonstrate how Teklink helps to achieve the maximum analytical range for analysis.

To allow for quick startup, predetermined methodology has been set up for various sample types. For example, there are preset methods for analyzing pharmaceutical water, drinking water, and wastewater.

This is the second in our Troubleshooting series for VOC Analysis. 

Part one is linked here, VOC Analysis Troubleshooting Part 1: How to Begin Troubleshooting

Part 2 will discuss No, or Low, Analyte Response and Carryover.

Troubleshooting your instruments can be a frustrating process, but I hope this series eases some of that pain and helps you through it. If you’re dealing with no or low response from your analytes, you first need to know if the analytes are even getting to the Gas Chromatograph and Mass Spectrometer (GC-MS). Following the advice in part one of this series, start with a direct injection into the GC of the same standards you use on your Purge and Trap (P&T), to confirm normal operation of the GC-MS. If you see poor chromatography and resolution or reduced response, you should change your inlet liner and clip the column.

A carefully designed and faithfully executed preventative maintenance program is the best method for maintaining your scientific instruments. Keeping up with daily, weekly, monthly, and even quarterly maintenance tasks will help maintain the performance of the unit and decrease downtime. Maintenance checklists can be found in the manual to your Teledyne Tekmar instrument. The manual can also be an immense help with troubleshooting, because it has tips and instrument flow diagrams.

Preventive maintenance for analytical instrumentation should be scheduled and performed proactively. It is something that should not be put on the back burner. Establishing and adhering to a preventive maintenance schedule is beneficial in many ways:

• Reduces the risk of instrument failure
• Decreases unexpected downtime
• Increases laboratory productivity
• Extends instrumentation lifetime
• Saves money

Water vapor entering the gas chromatograph (GC) inlet, column, and, ultimately, the mass spectrometer (MS) can minimize the sensitivity of our early eluting compounds, including our gases. It can also cause poor peak shape, compounds to co-elude, and shift in retention time, even in compounds outside of the water peak. So, once the water is introduced into our system, it starts to wreak havoc on all our compounds. Some say water doesn’t affect column phase or lifespan, but some have seen an effect, especially if you’re running a lot of samples; water can shorten the column life of your GC column and can cause vacuum issues if you’re using a MS system, which could lead to shorter filament lifetime and having to clean the source more often.

Throughout this blog series, we’ve discussed ways to minimize the amount of water vapor introduced to the GC-MS, using Teledyne Tekmar’s moisture control fitting and application control. We can continue to control moisture not only through this hardware designed for the Purge and Trap, but also through method parameters we can adjust and using smart method parameters on the GC.

The last two Purge and Trap (P&T) settings we will discuss in this blog series might be the most important for moisture control in this volatile organic compound (VOC) analysis: desorb and bake settings.

We can adjust our desorb time to help reduce the amount of moisture we put onto the gas chromatograph (GC) and mass spectrometer (MS). A longer desorb time will remove more of compounds from the analytical trap and send them to the GC, but this includes water, leading to a longer water peak in the total ion chromatogram. If the desorb time is shortened, less of that analyte material is transferred to the GC, but we will have a much shorter water peak, giving the compound peaks better shape and resolution. This gives us an opportunity for method optimization with the desorb settings both in time and temperature.

Total Organic Carbon (TOC) plays a vital role in today’s laboratory. There are two main types of TOC systems in today’s market: UV-Persulfate oxidation, and high temperature combustion oxidation. While these two systems have some areas of overlap, they offer different solutions for the laboratory. 

Read more to learn about the differences between these two systems.