News from LabRulezLCMS Library - Week 29, 2025

Our Library never stops expanding. What are the most recent contributions to LabRulezLCMS Library in the week of 14th July 2025? Check out new documents from the field of liquid phase, especially HPLC and LC/MS techniques!

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This week we bring you posters by Agilent Technologies / ASMS, Shimadzu / ASMS, Thermo Fisher Scientific / ASMS and Waters Corporation / ASMS!

1. Agilent Technologies / ASMS: Faster Than the Speed of Life: A Rapid Screening Method for Select PFAS Compounds in Serum by RapidFire-MS

• Poster
• Full PDF for download

Per- and polyfluoroalkyl substances (PFAS) are a broad class of compounds with a high degree of fluorination used in a variety of industries and consumer products over the past seventy years. Because of their widespread use, as well as their persistence and poorly understood effects on the human body, laboratories have started to monitor their presence in biological fluids, including serum. Biological samples are commonly prepared with protein precipitation. Additional cleanup steps such as solid phase extraction (SPE) with either C18 or weak anion exchange (WAX) sorbent can be used for increased sensitivity and cleanup. Alternatively, a pass-through cleanup using Captiva EMR-Lipid removes proteins and phospholipids through filtration, which significantly reduces sample complexity.

Experimental

Purchased serum was aliquoted into two sets of samples, one for protein precipitation (ppt) only and one for a protein precipitation plus Captiva EMR-Lipid based cleanup. For each preparation, 100 µL serum was aliquoted into a tube and spiked with 25 native and extracted isotopically labeled (EIS) compounds (EPA 533 list). The samples were vortexed for 1 minute and then crashed with 1% formic acid in cold ACN. They were vortexed for 3 minutes and then spun for 10 minutes to complete the crash. Samples undergoing the Captiva-EMR Lipid cleanup were then loaded onto a pre-rinsed cartridge and allowed to filter through (Figure 1). All samples were then spiked with the additional non-extracted isotopically labelled (NIS) compounds, vortexed, and transferred to a plate for analysis.

The RF/TQ system consisted of a RapidFire 400 front end with a 6495D triple quadrupole mass spectrometer for detection. Samples were introduced into the mass spectrometer using a RapidFire cartridge for additional cleanup, and the total cycle time was about 12.5 seconds, with analytes detected in negative polarity. Specific method conditions are detailed in Tables 1 (RF) and 2 (MS).

Results and Discussion

Early Development Work 

Feasibility studies for detection of PFAS compounds in serum using the RapidFire started by looking for PFAS background in the instrument and in all steps of the workflow. Early testing demonstrated no detectable background from any stage of the process.

RapidFire method development tested a variety of cartridges for optimal binding of the PFAS compounds, as well as determining the best state times and solvent conditions. For the preliminary work, the C18 cartridge appeared to have the best results, while the optimized elution solvent was 5 mM ammonium acetate in methanol.

Early experiments were performed to understand the effects of dilution and sample prep on the overall sensitivity of the method. When only a protein precipitation preparation was employed, dilution had a significant positive effect on analyte sensitivity, as shown in Figure 2. However, when the sample prep routine utilized protein precipitation in combination with a Captiva EMR-Lipid cleanup, additional dilution was not necessary and in fact decreased overall sensitivity, as shown in Figure 3. This is attributed to the removal of extraneous matrix using the Captiva EMR-Lipid device, which has a unique selectivity for unbranched alkane chains, capturing phospholipids while allowing PFAS compounds to pass through the sorbent bed unretained.

Custom Cartridge Work 

This preliminary work was done using the C18 cartridge, but the cartridge had poor retention of the short-chain PFAS compounds (C5 and below). To address this issue, a cartridge was custom-packed with mixed mode material that included C18 and anion exchange resins. Further testing and method optimization for this specific packing material yielded better results across the board, but especially for the short-chain PFAS compounds. Sensitivity for most analytes was at or below 0.1 ppb, as summarized in Table 3, with a calibration range of 0.01- 10 ppb tested for all analytes.

Conclusions

• LOQs for most PFAS analytes of interest in serum were 0.1 ppb or below
• Samples were injected every 12 seconds, allowing for high throughput analysis
• Custom mixed mode cartridge had best overall performance 
• There was no background PFAS contribution from the RapidFire system

2. Shimadzu / ASMS: Benchtop Matrix Assisted Laser Desorption Ionization Mass Spectrometry of PFAS for preliminary screening of environmental samples

• Poster
• Full PDF for download

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants which negatively impact human health and the environment. 
High concentrations of PFAS in test samples can cause contamination of sensitive LC-MS/MS instruments requiring extensive decontamination procedures, resulting in significant downtime and costly delays in sample processing. 

We present the development of a simple, cost-effective method for the rapid screening of PFAS samples using an entry-level linear benchtop MALDI-TOF mass spectrometer to identify samples containing high levels before they enter the analytical workflow.

Methods

PFOA and PFOS standards were purchased from Merck, UK. Stock solutions (1 ppm prepared in acetonitrile) were diluted in water to the required concentrations. 

Samples were tested with a variety of MALDI matrices (CHCA, DHB, DHAP, DAN, NRM and TMGN), with norharmane (NRM) and 1,8-bis(tetramethylguanidino)-naphthalene (TMGN) identified for further investigation. Diluted samples were mixed with NRM (1 mg/mL) or TMGN (5 mg/mL) in 70:30 Acetonitrile:Water. Blank samples of UHP water were prepared to ensure no contamination was present. 1 µL of the mixture was spotted onto a FlexiMassSR48 slide and the samples were analysed using a MALDI-8030 MALDI-TOF mass spectrometer (Shimadzu). Analysis conditions are shown in Fig 1. Peaks at m/z 314.2 and m/z 499.2 were monitored for PFOA and PFOS, respectively. 13C8PFOS (m/z 507) was used as an internal standard for PFOS samples with a final sample concentration of 6.25 ng/mL (see Fig. 2). MALDI-MSI was used to assess spot homogeneity and limits of detection were established.

Subsequently, PFHxA and PFBS standards were purchased from Merck, UK and analysed using the same method

Conclusion

• We have shown, in principle, that it is possible to use MALDITOF mass spectrometry to implement a simple pre-screening method for aqueous samples to prevent widespread contamination in a PFAS monitoring laboratory. Using just a 200 µL sample and minimal preparation, a full slide of samples can be acquired in less than 15 minutes 
• Spot imaging during method development highlighted the differences in homogeneity of PFOS and PFOA spots suggesting that multiple internal standards would be necessary to pursue semi-quantitative analysis. 
• Whole slide imaging can provide quick results for multiple samples across a range of PFAS concentrations in a single run with easy visual identification of potentially problematic samples. 
• As a linear MALDI-TOF method, these results do not confirm the presence of PFAS but may be used as an indicative result to modify further testing protocols. Confirmatory LC-MS/MS analysis is required to determine the presence and concentration of any PFAS.

3. Thermo Fisher Scientific / ASMS: Enhanced resolution with multi-pass mode on the Orbitrap Astral Zoom mass spectrometer 

• Poster
• Full PDF for download

The introduction of Thermo Scientific TMT 32-plex, with reporter ions clustered into quadruplets spaced by 3 mDa, demands a resolving power of approximately 90 k at low m/z, which challenges state-of-the-art time-of-flight mass analyzers. The Thermo Scientific Orbitrap Astral mass spectrometer [1] typically achieves around 60 k resolution at m/z = 138, falling to 50 k under high space charge influence. 

Here we present an enhanced resolution multi-pass method implemented in the new Thermo Scientific Orbitrap Astral Zoom mass spectrometer [2], significantly improving the resolving power at low m/z enabling TMT 32-plex on the Thermo Scientific Astral analyzer. The ions are repeatedly guided through a switchable prism deflector to extend the ion path while the principal aberrations are compensated, thereby more than doubling the resolution.

The Orbitrap Astral Zoom Mass Spectrometer

The Orbitrap Astral Zoom mass spectrometer incorporates a range of novel technologies for higher speed, sensitivity, dynamic range and resolving power. A faster ion filter and quadrupole switching in combination with improved ion transfer times in the ion-routing multipole (IRM) and ion processor allow DIA methods (Thermo Scientific Pierce FlexMix calibration solution, 2 Th isolation window, 350-980 m/z range, Thermo Scientific Orbitrap MS and Astral MS/MS) with scan rates faster than 270 Hz (DDA methods > 180 Hz). A duty cycle of up to 80 % at 270 Hz is made possible by a new accumulation stage in the bent trap (linear to 106 ions) which increases the effective ion injection into the IRM by up to 40 % (additional ~0.75 ms on top of 2 ms IT in a DIA method). Furthermore, an additional mode of the high-dynamic range detector of the Astral analyzer for low-input sample applications like single-cell proteomics boosts the single ion detection efficiency by about 10 % and thereby the sensitivity. In combination with a new peak deconvolution algorithm for enhanced spectral processing, this increases the depth of analysis. In addition, modified IRM hardware allows for faster stepped collision energy experiments for deeper spectral coverage (2 CE: 80 Hz (OT Astral), 180 Hz (Orbitrap Astral Zoom MS), 3 CE: 60 Hz, 150 Hz). A modified AGC filling in the Orbitrap by a new enhanced dynamic range mode (EDR) provides additional spectral complexity and sensitivity. Here, multiplexed ion injections with different accumulation times are used for different mass ranges taking the variation in signal intensity into account. In addition, the Astral analyzer incorporates a new multi-pass mode which enhances the resolving power for small masses by more than a factor of two, enabling TMT 32-plex measurement in the Astral analyzer.

Conclusions 

The TMT HR Mode advances the capabilities of the Astral analyzer. Fast electronic switching of the relay prism opens an ion trap and guides the ions after three times their normal flight distance to the detector. This greatly boosts the resolving power, especially for small m/z ratios, thereby enabling baseline-resolved quadruplets of reporter ions in a TMT 32-plex sample. First results show a peak resolution well above 100 k while maintaining high mass accuracy and shot-to-shot stability. The TMT HR Mode is utilized within a novel acquisition scheme delivering greater throughput for protein identification and quantitation for multiplexing up to 32 samples. Achieving a throughput of over 440 samples per day, the proteome coverage included 4,299 quantified protein groups and 22,146 peptides.

4. Waters Corporation / ASMS: Assessing the Impact of Part-per-Billion Mass Accuracy Upon Forensic Toxicology Data-Independent Analysis Screening 

• Poster
• Full PDF for download

This poster presents a forensic toxicology screening approach using ultra-high mass accuracy to improve specificity and efficiency in the analysis of complex biological matrices, such as urine. The need for rapid, accurate, and cost-effective screening is critical in forensic laboratories. The study evaluates the impact of parts-per-billion (ppb) mass accuracy using the Waters Xevo MRT Mass Spectrometer compared to previous DIA methods.

The method involved analyzing a commercial standard and ten anonymized urine samples, diluted and analyzed via the ACQUITY UPLC I-Class FTN PLUS System coupled with the Xevo MRT MS. Data acquisition was performed in MSE mode (data-independent acquisition) under positive electrospray ionization (ESI+) using a 15-minute gradient. Data were processed in waters_connect software, leveraging a comprehensive spectral library with over 2000 compounds.

Results demonstrated a root mean square (RMS) mass error of just 571 ppb for precursor ions, with 94% of compounds detected within 1 ppm, and 96% of fragment ions within the same tolerance. A key example illustrated how reducing fragment ion tolerance from 2 mDa to 0.2 mDa eliminated a false positive (Anabasine), correctly identifying Nicotine as the true analyte, showing how ppb-level accuracy increases identification confidence and minimizes misidentifications.

The study concludes that ppb mass accuracy significantly reduces false positives, lowers review workloads, and facilitates independent analysis by less experienced personnel. Additionally, it supports cost savings by minimizing the need for confirmatory testing, potentially reducing both financial and environmental burdens in forensic laboratories.