Uncommon Fix for LC–MS Ion Suppression
LCGC North America
Metal-free columns should be considered when troubleshooting ion suppression. Chelating compounds that can form metal salt with stainless steel column housings are examined.
Most HPLC columns are made with stainless steel 316, which has surface oxides, and Fe(++), which have a high affinity for the exposed anionic oxygens present on phosphorylated compounds, and will readily interact causing adsorption and loss of sample. Additionally, these interactions can result in the formation of metal salts that can cause ion suppression when using LC–MS detection, potentially reducing analyte signal or, in extreme cases, cause no signal at all.
In this article, we show two cases of ion suppression and loss of sample due to adsorption, and recovery of signal strength by using our newly developed metal-free column housing. Our design utilizes the typical stainless-steel hardware so that we can preserve high-pressure capability, but the internal surfaces of the tubing and end fittings, as well as the inlet and outlet frits, are all coated with PEEK. This removes the largest contribution of metal surfaces within the HPLC sample flow path, significantly improving the analysis for certain compounds.
Experimental Conditions
Figures 1 and 2 show organophosphorus pesticides or herbicides, and nucleoside triphosphates, respectively. All running conditions are shown within the figures. In each case, identical conditions were used on two columns packed with the same material; one with our metal-free housing, and the other with standard stainless steel.
Result and Discussion
The most dramatic example of ion suppression can be seen in Figure 1, particularly for glyphosate. While glufosinate does show signs of signal suppression and chelating, glyphosate is completely missing on the metal column, with LC–MS detection. Both peaks showed a much-improved LC–MS signal and analyte recovery when using a metal-free vs. a metal column. Peak shape was also improved.
Figure 1: Complete ion suppression of glyphosate signal
The triphosphates in Figure 2, while not completely missing as in the case of glyphosate, did show significant evidence of ion suppression and chelating for all nucleosides tested. In all cases, peak heights were dramatically reduced, and peak shape was negatively impacted. Under identical conditions, but in metal-free housing, all peaks showed an increase in symmetry and signal strength.
Figure 2: Triphosphates on metal-free vs. metal column
Conclusion
Often when troubleshooting issues with poor peak shape, low recovery and signal suppression, contributions of interaction with the column housing can easily be overlooked. Here we show that, particularly for certain compounds, there can be considerable interaction of the analytes with metal surfaces within the column. Therefore, the use of a metal-free column should be considered when troubleshooting issues related to poor peak shape, loss of sample, and ion suppression for potentially chelating compounds, especially when peak shape cannot be improved through modification of the mobile phase. It is also worth noting that we now offer metal-free columns in 15 different stationary phases, improving the range of available separation conditions. Please visit our website for more information.
Imtakt USA
2892 NW Upshur St., Portland, OR 97210
tel. (888) 456-HPLC, (215) 665-8902. Fax: (501) 646-3497
Website: ImtaktUSA.com
Simplifying the GC Laboratory for Improved Efficiency
December 9th 2024Laboratories continually work to increase the capacity of their equipment, improve turnaround times and gain confident and detailed insights without generating additional burden on their operators. Discover how adopting the simplification strategy of Industry 4.0 with the GC 2400™ Platform can enhance GC workflows to increase efficiency, data quality, and business sustainability
How to Enable Sustainable GC Lab Operations
December 9th 2024Sustainability strategies are being integrated into a growing number of businesses and their operations. Laboratories are no exception. Although the necessity to reduce the environmental impact of laboratory operations is recognized, it cannot be disengaged from the economic viability of labs. This article shares ways in which laboratories can improve both their business and environmental sustainability and discusses how the GC 2400™ Platform is helping laboratories flourish in these areas
What Are the Key Features of a Smart and Connected GC Lab?
December 9th 2024The potential of smart technologies has evolved into a operational necessity - businesses were faced with the need for remote and automated operations bringing substantial improvements in productivity, efficiency, and operating costs.
Automated PFAS Extraction from Difficult Food and Food Packaging Samples
December 6th 2024More and more regulations regarding PFAS are being implemented with action limits that continue to decrease. Having a harmonized method to accurately determine the PFAS content in food, as well as other matrices, is important to ensuring long-term detection and regulation. The solvent extraction of PFAS from these varied sample matrices can be challenging given the susceptibility to contamination and the low levels in which these compounds are present. This poster, presented at RAFA 2024, examines the PFAS extraction several different food samples as well as food packing matrices.
Extraction of 40 PFAS Compounds from Soil and Tissue
December 6th 2024PFAS have been shown to cause health issues in humans, which means monitoring environmental solid samples, such as soil and tissue, is critical. This application note details the extraction of 40 spiked PFAS compounds from soil and tissue following EPA Method 1633. The automated extraction was less than 10 minutes per sample and yielded acceptable recoveries and RSDs without carryover in the system. The EDGE PFAS is an ideal option for laboratories that want to automate their PFAS extractions of solid samples.
