Atmospheric pressure laser ionization (APLI) (Constapel et al. in Rapid Commun Mass Spectrom 19:326-336, 2005; Schiewek et al. in Anal Chem 79:4135-4140, 2007; Schmitz and Benter (2007) J Chromatography Library 72:89-114) is an ultra-sensitive and selective ionization method for the determination of polycyclic aromatic compounds. The selectivity is an advantage but also a disadvantage. To overcome the limitation of APLI to aromatic compounds, we have already reported some derivatization strategies for common organic functional groups (Schiewek et al. in Angew Chem Int Ed 47:9989-9992, 2008). Here, we describe the synthesis of new APLI ionization labels and their use in new derivatization strategies. These new labels widen the range of APLI-(TOF)MS analysis to non-aromatic compounds with the most common functional groups such as amines, alcohols and carboxylic acids to gas chromatography (GC) and lower the limits of detection (LOD) down to concentrations as small as pmol/L and attomole on column.

The outstanding selectivity and sensitivity of the atmospheric pressure laser ionization (APLI), which is a two-photon ionization process, in combination with a mass spectrometric detection, is demonstrated for the analysis of DNA adducts. Preparative HPLC with a HILIC-phase and a fraction sampler was used to separate the polar 4-hydroxy-1-(3-pyridyl)-butanone (HPB) and 4-hydroxy-1-(3-pyridyl)-butanol (Diol), which will be formed after acid hydrolysis of the POB- and PHB-DNA adducts. The adducts eluted in the fractions to be analyzed were collected, concentrated to dryness and dissolved in dichloromethane. Then 4-(dimethylamino)pyridine as a base, N,N′-dicyclohexylcarbodiimide as an activator and anthracene-9-yl-methoxyacetic acid as an ionization marker, in analogy to a fluorescence marker, were added, and after several hours at 35 °C the sample was injected into an HPLC-APLI-TOF(MS). With this novel method, only aromatic compounds are ionizable; because the ionization marker of the DNA adducts carries an aromatic group, this allows ionization by the two-photon process. For the first time we have used a new strategy to analyse DNA adducts by HPLC-APLI-TOF(MS) after derivatization with an ionization marker. To demonstrate the utilizability of this method, we analyzed POB and PHB adducts, which are formed by metabolic activation pathways from 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N′-nitrosonornicotine (NNN). In summary, we have demonstrated that the derivatization strategy significantly increases the analytical applicability of APLI-MS and shows new methods for the important DNA adduct analysis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4661. doi:10.1158/1538-7445.AM2011-4661