An ambient ionization technique for mass spectrometry, desorption atmospheric pressure photoionization (DAPPI), is presented, and its application to the rapid analysis of compounds of various polarities on surfaces is demonstrated. The DAPPI technique relies on a heated nebulizer microchip delivering a heated jet of vaporized solvent, e.g., toluene, and a photoionization lamp emitting 10-eV photons. The solvent jet is directed toward sample spots on a surface, causing the desorption of analytes from the surface. The photons emitted by the lamp ionize the analytes, which are then directed into the mass spectrometer. The limits of detection obtained with DAPPI were in the range of 56-670 fmol. Also, the direct analysis of pharmaceuticals from a tablet surface was successfully demonstrated. A comparison of the performance of DAPPI with that of the popular desorption electrospray ionization method was done with four standard compounds. DAPPI was shown to be equally or more sensitive especially in the case of less polar analytes.

A microfluidic nebulizer chip for mass spectrometry is presented. It is an all-glass device which consists of fusion bonded Pyrex wafers with embedded flow channels and a nozzle at the chip edge. A platinum heater is located on the wafer backside. Fabrication of the chip is detailed, especially glass deep etching, wafer bonding, and metal patterning. Various process combinations of bonding and metallization have been considered (anodic bonding vs. fusion bonding; heater inside/outside channel; metallization before/after bonding; platinum lift-off vs. etching). The chip vaporizes the liquid sample (0.1-10 microL min(-1)) and mixes it with a nebulizer gas (ca. 100 sccm N2). Operating temperatures can go up to 500 degrees C ensuring efficient vaporization. Thermal insulation of the glass ensures low temperatures at the far end of the chip, enabling easy interconnections.

The factors influencing desorption and ionization in newly developed desorption atmospheric pressure photoionization-mass spectrometry (DAPPI-MS) were studied. Redirecting the DAPPI spray was observed to further improve the versatility of the technique: for dilute samples, parallel spray with increased analyte signal was found to be the best suited, while for more concentrated samples, the orthogonal spray with less risk for contamination is recommended. The suitability of various spray solvents and sampling surface materials was tested for a variety of analytes with different polarities and molecular weights. As in atmospheric pressure photoionization, the analytes formed [M + H](+), [M - H](-), M(+*), M(-*), [M - H + O](-), or [M - 2H + 2O](-) ions depending on the analyte, spray solvent, and ionization mode. In positive ion mode, anisole and toluene as spray solvents promoted the formation of M(+*) ions and were therefore best suited for the analysis of nonpolar compounds (anthracene, benzo[a]pyrene, and tetracyclone). Acetone and hexane were optimal spray solvents for polar compounds (MDMA, testosterone, and verapamil) since they produced intensive [M + H](+) ion peaks of the analytes. In negative ion mode, the type of spray solvent affected the signal intensity, but not the ion composition. M(-*) ions were formed from 1,4-dinitrobenzene, and [M - H + O](-) and [M - 2H + 2O](-) ions from 1,4-naphthoquinone, whereas acidic compounds (naphthoic acid and paracetamol) formed [M - H](-) ions. The tested sampling surfaces included various materials with different thermal conductivities. The materials with low thermal conductivity, i.e., polymers like poly(methyl methacrylate) and poly(tetrafluoroethylene) (Teflon) were found to be the best, since they enable localized heating of the sampling surface, which was found to be essential for efficient analyte desorption. Nevertheless, the sampling surface material did not affect the ionization mechanisms.

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This work reveals the material impacts on long-term cell survival and adhesion on 3D printed surfaces manufactured by stereolithography.

The feasibility of desorption atmospheric pressure photoionization (DAPPI) in the direct analysis of illicit drugs was demonstrated by the analysis of confiscated drug samples of various forms such as tablets, blotter paper, and plant resin and bloom. 3,4-Methylenedioxymethamphetamine (MDMA), amphetamine, phenazepam, and buprenorphine were detected from the analyzed tablets, lysergic acid diethylamide (LSD) and bromobenzodifuranylisopropylamine (bromo-Dragonfly, ABDF) from blotter paper, and Delta(9)-tetrahydrocannabinol (THC) and cannabinol from Cannabis Sativa bloom and resin. The amphetamines, phenazepam and ABDF showed protonated molecules independent of the solvent used, whereas buprenorphine, LSD and the cannabinoids showed molecular ions with toluene and protonated molecules with acetone as the solvent.

We present a microfabricated nebulizer chip for combining atmospheric pressure photoionization-mass spectrometry (APPI-MS) with gas chromatography (GC) or capillary liquid chromatography (capLC). The chip consists of a silicon plate and a glass plate or two glass plates. The chip includes a sample inlet channel, auxiliary gas and dopant inlet, vaporizer channel, nozzle, and platinum heater. The sample eluted from the capLC or GC is mixed with auxiliary gas and dopant (toluene) in the heated vaporizer. The chip forms a confined jet of the sample vapor, which is photoionized as it exits the chip. The analytical performance of GC- and capLC-microchip APPI-MS was evaluated with some polycyclic aromatic hydrocarbons, amphetamines, and steroids. The GC-muAPPI-MS method provides high sensitivity down to 0.8 fmol, repeatability (RSD = 7.5-14%), and linearity (r = 0.9952-0.9987). The capLC-muAPPI-MS method shows high sensitivity down to 1 fmol, good repeatability (RSD = 3.6-8.1%), and linearity (r = 0.9989-0.9992).

The first miniaturised 3D printed polypropylene reactor with an integrated nanoelectrospray ionisation capillary and a stir bar for mass spectrometric online reaction monitoring.