Triple Quad vs Single Quad Mass Spectrometry – What’s the Difference?

What Is a Quadrupole Mass Spectrometer?

Quadrupoles, commonly referred to as ‘quads,’ are crucial components within mass spectrometers, consisting of four cylindrical rods to which both DC and RF voltages are applied. These versatile quad rods perform a range of functions that significantly enhance the sensitivity and selectivity of analytical methods compared to other techniques.

One primary role of quads is to act as mass analyzers, isolating specific analytes or selecting sample ions based on their mass-to-charge ratio (m/z) for transmission. Additionally, they serve as efficient transmission elements, capturing ions and facilitating their cooling and transmission with minimal loss to the subsequent elements of the mass spectrometer. Moreover, quads can function as collision cells breaking ions into sub-components, enabling further analysis and identification.

The power and flexibility of these quadrupole rods are key to the improved performance of mass spectrometry in various applications. They allow for the precise isolation and manipulation of ions, leading to enhanced sensitivity and accuracy in data acquisition.

In summary, quadrupoles play a pivotal role in modern mass spectrometry, offering enhanced sensitivity, selectivity, and flexibility. Their ability to act as mass analyzers, transmission elements, and collision cells makes them indispensable tools in a wide range of scientific and analytical applications. This article will explore the differences between and single and triple quadrupole mass spectrometers, highlighting when each should be used and the advantages of using a TQ-MS over an SQ-MS.

What Is the Difference Between A Single and Triple Quadrupole Mass Spectrometer?

In a single quadrupole mass spectrometer (SQ-MS), a single quad functions as either a mass filtering quad or a mass scanning quad.

On the other hand, a triple quadrupole mass spectrometer (TQ-MS) incorporates three quads within a single instrument, offering significantly enhanced functionality and higher selectivity compared to a single quad. In this system, the first and third quads serve as mass filters, while the second quad acts as a collision cell, resulting in additional fragmentation of the target compounds.

The most commonly used mode with a single quad MS is Selected Ion Monitoring (SIM), which allows only the ion with a given m/z to pass through the quadrupole and reach the detector.

On the other hand, in a triple quad MS, Multiple Reaction Monitoring (MRM) is the prevailing mode for analysis. MRM provides improved sensitivity and specificity by monitoring predefined precursor-to-product ion transitions.

In summary, while single quad MS provides basic mass filtering or scanning capabilities, the triple quad MS excels in performance with its coordinated trio of quads and the ability to utilize MRM, making it a preferred choice for advanced and precise analytical applications.

When to Use a Single Quad vs a Triple Quad

A single quad mass spectrometer is easy to used, robust and cost-effective making it a multipurpose instrument suitable for targeted and untargeted analysis.

On the other hand, a triple quad mass spectrometer excels in achieving low limits of detection, particularly in complex matrices, making it ideal for a wide range of quantitative analyses. Operating in multiple reaction monitoring (MRM) mode, this instrument can acquire target fragment ions for the target compound, removing chemical noise and enabling precise quantification within a single run. The remarkable MRM speed has the ability to analyze hundreds of compounds in a single run without compromising quantitative performance.

The flexibility of the triple quad mass spectrometer extends its utility to food safety, pharmaceutical and forensic laboratories for target compounds screening purposes, as well as various other applications requiring high sensitivity and specificity. For instance, it is exceptionally useful in quantifying critical or low abundance compounds in complicated biological matrices, THC metabolites in oral fluid being an example.

The Advantage of Using Triple Quad Over Single Quad Mass Spectrometry

Multiple Reaction Monitoring (MRM) using triple quadrupole mass spectrometry provides several advantages over Selected Ion Monitoring (SIM) using a single quadrupole mass spectrometer. MRM with triple quadrupole MS/MS offers higher selectivity and less interference from co-eluting compounds and matrix components. This reduces the need for extensive method development, enabling faster analysis times whilst also providing lower limits of quantitation (LOQ), due to improved signal-to-noise ratios.

Moreover, the triple quadrupole mass spectrometer, SCION Instruments 8900 TQ-MS requires fewer ions per compound for confirmatory analysis, with the EU Commission Decision mandating detection of 2 MRM transitions and 4 SIM transitions, respectively. This technology offers greater sensitivity than SIM, allowing for identification of lower-level analytes especially in matrix samples. Lastly, triple quadrupole MS/MS delivers a wider linear range, improved accuracy, and reproducibility in comparison to single quadrupole SIM.

The Advantages of a SCION 8900 TQ-MS

Increased selectivity:

SCION’s  8900 Triple Quadrupole MS offers increased selectivity over the SCION  8700 SQ-MS as it uses two quadrupoles in series to isolate target mass ions. This significantly reduces background noise and increases selectivity, allowing for better identification and quantification. Detection by triple quadrupole tandem mass spectrometry (MS/MS) allows for superior selectivity through double mass filtering. In MRM mode, a unique product ion of analyte different from product ion of interface is generally detected, while in SIM mode, with unit mass resolution signals per compound can be detected. The reason is the generation of identical fragmentation ions in the ion source from the interference and analyte.

Improved sensitivity:

The SCION 8900 TQ-MS is also more sensitive than 8700 SQ-MS. With MRM mode, it can detect trace levels in samples at much lower concentrations. The signal-to-noise ratio (S/N) is higher, resulting in lower limits of quantification (LOQ). The typical difference in sensitivity observed is at least two orders of magnitude. Ability to perform analyses in Multiple Reaction Monitoring (MRM) mode: 8900 TQ-MS can perform analyses in MRM mode, which removes chemical noise and allows for quantification of multiple target compounds in a complex mixture. This technique significantly improves the precision and sensitivity of the measurement.

Linearity and reproducibility:

Generally, a wider linear range can be used for quantification if a triple quadrupole MS/MS is used due to the increased selectivity allowing for detection at lower LOQs. The upper limit of quantification of SIM and MRM is usually comparable due to the compound ionisation efficiency or detector saturation. Both 8700 SQ and 8900 TQ are equipped with an Extended Dynamic Range detector to minimise detector saturation.

Versatility:

SCION’s 8900 TQ-MS is more versatile than 8700 SQ-MS, as it can also be used for high speed compounds screening without compromising sensitivity, such as analysis 400 pesticides or drugs in a single run.

The SCION 8700 SQ-MS

If you believe the single quad mass spectrometer is better suited to your needs, we have the perfect solution for you. The SCION 8700 SQ-MS is designed for today’s fast paced analytical laboratory.

Innovative design features such as a lens-free ion path, heated ion optics and an Extended Dynamic Range (EDR) detector enable the SCION SQ to deliver accurate quantification and identification, even in complex matrices.

View the 8700 SQ GC-MS product page to find out more.

Keep In Touch

If you have any question regarding our quadrupole mass spectrometer systems, please get in touch, and a member of our team will be happy to help.

Additionally, if you wish to keep up to date with our latest news, join us on social media – LinkedIn, Facebook, Twitter – or sign up to our newsletter below.