The Updated Bottom Up Solution Applied to Atmospheric Pressure Photoionization and Electrospray Ionization Mass Spectrometry

摘要

The Updated Bottom Up Solution (UBUS) was recently applied to atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) of triacylglycerols (TAG). This report demonstrates that the UBUS applies equally well to atmospheric pressure photoionization (APPI) MS and to electrospray ionization (ESI) MS. Critical Ratio 1 (CR1), the [MH](+)/I [DAG](+) pound or [MNH4](+)/I [DAG](+) pound ratio, does not exhibit the same strongly sigmoidal shape as it does by APCI-MS. CR1 varies more widely for APPI-MS than by APCI-MS, having a maximum value of 11.8, indicating a much greater effect of unsaturation on ion ratios in APPI-MS than APCI-MS. Critical Ratio 2, the [AA](+)/[AB](+) ratio for Type II TAG or [AC](+)/([AB](+)+[BC](+)) ratio for Type III TAG, allows quantification of regioisomers of TAG, and shows good agreement for APPI-MS to regioisomer quantification determined by APCI-MS. Critical Ratio 3, the [BC](+)/[AB](+) ratio for Type III TAG, reveals new trends relating the degree of unsaturation by APPI-MS, and shows that structural assignments made by ESI-MS are in good agreement to APCI-MS data. In addition to providing valuable structural information, the Critical Ratios also constitute a reduced data set that allows APPI-MS or ESI-MS mass spectra to be reconstructed when processed through the UBUS. Quantification by APPI-MS of vitamin D in the gelcaps gave values of 42.90 +/- A 0.83 mu g, or 1716 +/- A 33 international units, in good agreement with APCI-MS.