Technical FAQs

Build up of deposits and contamination can interfere with MS performance leading to loss in performance and sensitivity. Regular cleaning of the ion source as per manufacturer recommended guidelines is highly recommended. However cleaning beyond the source should only be carried out by trained engineers.

We recommend regular PMs to keep systems running in optimum condition. We offer these as a stand alone visit or part of a more comprehensive contract, details can be found on our service contracts and preventive maintenance pages

Providion recommend that the instrument calibration and resolution optimisation should be performed every 6 months especially if the instrument is being used frequently. If there isn’t the ability in-house for someone to perform this optimisation then Providion can provide training to up-skill the end user. We also offer a PM as a stand alone visit or part of a more comprehensive contract, more details can be found on our service contracts and preventive maintenance pages.

First it is best to understand the differences in the techniques. ESI ionisation occurs in the mobile phase with the addition of either a basic or acidic modifier to promote ionisation (commonly forming either M+H or M-H ions)
APCI ionisation occurs at the corona needle via a cascade reaction involving gas-phase ion-molecule reactions.
ESI ionisation is the most senstivive technique wrt to SN for polar analytes whereas APCI is the most sensitive for non-polar analytes.
APCI can be a useful technique for overcoming matrix effects (competitive ionisation) and sometimes where high LC flow rates are required can achieve improved linearity over ESI.

For Electrospray MS in the positive mode, it is typical to detect (M+H)+ and relevant fragment ions, whilst with the negative ion mode, (M-H)+ molecular ions are normally observed. It is also common to observe clusters and other adduct ions as well. Molecules tend to cluster when run by electrospray, particularly if the sample concentration is high. Larger molecules that readily take on multiple charges, such as proteins and oligonucleotides, commonly appears as multiple groups of ions with increasing charge

Please check for any leaks in and around the pump and make sure the oil is still at a suitable level, depending on what type of pump you can normally check this by looking through the oil sight glass, the level of oil should be more than half but not full. (70% is ideal)

If maintenance on the pump been carried out recently, please check all connections making sure centering rings and clamps are sealed correctly.

At Providion we provide a full 12 month warranty on backing pumps to ensure you don’t suffer any downtime between services. Please contact us for further details or to see the pumps we offer please go to our online store.

Start in Pos Ion mode and use compound such as PPG’s to monitor MI scans across the range of masses that reflect the region you typically work within. Aquire run for 2 minutes then switch to Neg Ion mode and run for 1 minute. Switch back to Pos Ion and run for 3 minutes. If the system is charging the MI trace will drop over the 3 minutes. 5-10% drop is generally acceptable, but 15-20% or more will require attention.

This test should be performed for both scanning quadrupoles in both Pos and Neg mode. Depending upon the results seen, it can be determined which region of the MS Ion Optics requires cleaning. For help with this test, or interpretation of results and required action, please complete our tech support form for an Engineer to get in touch.

Depending on the noise level, we would usually recommend shutting down the MS immediately to avoid catastrophic failure of the pump. We can arrange for an exchange pump at a fraction of the cost of a new pump only if the pump has not suffered catastrophic failure or rotor damage. Please see our on-line store to check prices of the pumps we stock, or complete our contact form to request a quote for an Engineer to install the required pump.