SELF TEST 6.2

Matrix material must absorb at the laser wavelength that is used.

Selection of matrix material depends on the analysed sample (lipide, resin, saccharide, etc.).

Basic matrix material mixed with the basic sample is more suitable for the analysis in positive ion mode, and acidic matrix material mixed with the sample that possesses acidic compounds is more suitable for negative ion mode.

Solvent(s) used for the sample and matrix material do not have to be compatible with each other.

With direct MS it is possibility to use smaller sample amounts compared to sample size needed for LC-MS or GC-MS analysis.

Sample preparation for direct MS analysis has more steps than usual LC-MS or GC-MS sample preparation.

The selection of solvents suitable for direct MS analysis is bigger than for LC-MS and GC-MS analysis.

For direct MS analysis the sample must always be derivatised.

For direct MS analysis the sample components must be ionised.

For MALDI-MS analysis it is necessary that the sample is fully dissolved. 

For MALDI-MS analysis the sample must be co-crystallised with a suitable matrix material.

With ESI-MS hazy sample solution can be analysed. 

With APCI-MS it is not possible to analyse samples without derivatisation. 

With ESI-MS only dissolved samples can be analysed. 

Identification of compounds from EI-MS spectra is easy because the obtained mass spectra are simple and contain mainly information about molecular ions. 

Identification of compounds from ESI-MS spectra is complicated due to high fragmentation. 

The sample does not require any sample preparation when direct temperature EI-MS is used as analysis method.

The varnish sample must be mixed with a matrix solution and co-crystallised with the matrix before EI-MS analysis.

The varnish sample must be fully dissolved and derivatised before analysis with EI-MS coupled to a gas chromatograph.

The amount of varnish sample needed for EI-MS analysis must at least be 1 mg.

The dye must be extracted from the fibre with a suitable solvent and the solution must be filtered (or centrifuged) for analysis with ESI-MS.

The dyed textile fibre can be directly analysed with ESI-MS, no sample preparation is needed for analysis. 

The dyed fibre must be soaked with matrix material solution and co-crystallised with the matrix for ESI-MS analysis.

Preferably more polar compounds in red dye are ionised.

The interpretation of the mass spectrum of dye is based on the retention times of the most intensive chromatographic peaks of the compounds, their m/z values and isotope patterns.