A novel approach for sensitivity enhancement in atmospheric pressure chemical ionisation liquid chromatography/mass spectrometry of chlorophylls

Abstract

Differences in the ionisation efficiency of chlorophylls and their phaeophytin counterparts result in lower sensitivity for atmospheric pressure chemical ionisation mass spectrometric detection of the former. Improvement in the sensitivity of detection of chlorophyll of around an order of magnitude at a concentration of 1 x 10(-6)mol L(-1) has been achieved using post-column addition of methanoic acid during analysis by liquid chromatography/mass spectrometry (LC/MS). The method gives linear response and is a simple strategy to improve sensitivity both for LC/MS and LC/MS/MS without loss of information relating to the precise nature of the tetrapyrrole distributions. Detection levels achieved exceed those obtained by absorbance detection.

Observation of phenyl-fused porphyrinoids during the ESI mass spectrometric analysis of meso-pentafluorophenyl-substituted porphyrin and corrole

“…Electrospray ionization (ESI) mass spectrometry (MS) is becoming a popular technique for the analyses of porphyrins [25][26][27][28][29][30][31][32][33][34][35].…”

Mass Spectrometry of Chlorophylls from Phototrophic Prokaryotes

“…Many species are unable to use sulphide but can metabolise simple organic molecules for sources of reducing power [50]. Under APCI conditions, bacteriochlorophyll a, analysed as the bacteriophaeophytin due to post-column addition of acid [26] gives rise to a protonated molecule at m/z 889 [47]. Isolation of the ion at m/z 889 in the ion trap gives rise to a prominent ion at m/z 611 in MS 2 [46,47,59], corresponding to the loss of the phytyl chain, consistent with phytyl-esterified chlorins and bacteriochlorins.…”

The impact of different intensities of green light on the bacteriochlorophyll homologue composition of the chlorobiaceae Prosthecochloris aestuarii and Chlorobium phaeobacteroides

“…In those studies, structural assignment of the bacteriochlorophyll homologues was not possible using HPLC combined with UV/visible spectrometry: the in vitro absorption spectra of the different forms are very similar because the substituents are not conjugated to the chromophore. In this study we combined HPLC with both PDA detection (HPLC-PDA) and tandem mass spectrometry (LC-MS/MS) following recently developed procedures (Airs & Keely, 2000Airs et al, 2001a). This method has provided unambiguous information of the molecular mass of bacteriochlorophyll homologues, although unfortunately we were not able to distinguish between the two possible combinations of alkyl substituents at positions C-8 and C-12; e.g.…”

“…During LC-MS analysis, the chlorophylls were demetallated on-line as they eluted from the HPLC column prior to entering the mass spectrometer. The demetallation was achieved by the addition of a small amount of methanoic acid to the solvent flow (Airs & Keely, 2000). As a result of the on-line demetallation, the mass spectra were dominated by the protonated molecules (MH + ) of the corresponding bacteriophaeophytins.…”

“…ND, Not determined. *All bacteriochlorophylls appear as the corresponding phaeophytins due to post-column demetallation prior to sequential scanning (Airs & Keely, 2000). DObtained by resonance excitation during LC-MS analysis.…”