lc ms selection: which mass analyser answers your question, where hplc ms and hplc ms/ms sit as the coupled technique, and what lc-ms services, an hplc analysis service, a mass spectrometry service, mass spectrometry services, mass spectrometry companies, a mass spectrometry lab and a mass spectrometry analysis service should quote against when you outsource instead

Choosing the analyser, or the provider

1. Targeted quantitation wants a triple quadrupole. For measuring known compounds at low concentrations in complex matrices, a triple quadrupole monitoring specific transitions gives the sensitivity and the dynamic range, and it is the workhorse of quantitative bioanalysis and residue testing.
2. Discovery wants high resolution. Identifying unknowns needs accurate mass and fragmentation, which means a time-of-flight or orbital trap analyser. These also quantify, less well at the very bottom of the range, and they generate far more data that somebody has to handle.
3. Ionisation follows the analyte. Electrospray suits polar and ionisable compounds; atmospheric pressure chemical ionisation suits less polar ones. Some analytes ionise poorly in both and need derivatisation. This is decided by chemistry rather than by instrument brand.
4. Matrix effects are the real difficulty. Co-eluting matrix components suppress or enhance ionisation, which moves results without any obvious sign. Stable isotope labelled internal standards are the proper defence, and a method without one in a complex matrix should be treated with caution.
5. Scoping an outsourced method. Give the provider the analyte, the matrix, the concentration range and the required limit, and ask what internal standard is used, what validation has been performed in that matrix, and what the certificate reports. A quote without those is not comparable with another.

The real cost of owning one

The instrument is the smaller part. Service contracts on mass spectrometers are substantial, solvents and standards recur, and the instrument needs an experienced operator to produce data anyone should rely on. Laboratories that buy one without the person get a very expensive instrument producing plausible numbers.

For occasional work, an accredited service laboratory is almost always cheaper and better than ownership. Ownership makes sense when the workload is continuous and the method is yours.

Records and validation

Where results are reported, complete laboratory records covering the method, the calibration, the quality controls and any reprocessing are required, and the data system's audit trail is part of that. Reprocessing without a recorded reason is the thing that draws attention.

Method validation in the actual matrix, not in solvent, is what makes a quantitative result defensible. Ask which matrix a provider validated in before accepting a quote.

Common questions

Which mass analyser do I need?

A triple quadrupole for targeted quantitation of known compounds at low levels; a high resolution analyser for identifying unknowns. They are different instruments for different questions and each does the other's job poorly.

What are matrix effects?

Suppression or enhancement of ionisation by co-eluting sample components, which shifts results without any obvious sign. Stable isotope labelled internal standards are the proper defence in complex matrices.

Should I buy an LC-MS or outsource?

Outsource occasional work: the instrument is the smaller cost beside service, consumables and an experienced operator. Ownership makes sense when the workload is continuous and the method is yours.

What should an LC-MS quote specify?

The analyte, matrix, concentration range and required limit, the internal standard used, the validation performed in that matrix, and what the certificate reports. Without those, two quotes are not comparable.

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