Feasibility of atmospheric pressure desorption/ionization on silicon mass spectrometry in analysis of drugs

The feasibility of atmospheric pressure desorption/ionization on silicon mass spectrometry (AP-DIOS-MS) for drug analysis was investigated. It was observed that only compounds with relative high proton affinity are efficiently ionized under AP-DIOS conditions. The limits of detection (LODs) achieved in MS mode with midazolam, propranolol, and angiotensin II were 80 fmol, 20 pmol, and 1 pmol, respectively. In MS/MS mode the LODs for midazolam and propranolol were 10 fmol and 5 pmol, respectively. The good linearity (r(2) > 0.991), linear dynamic range of 3 orders of magnitude, and reasonable repeatability showed that the method is suitable for quantitative analysis.     

Design and fabrication of integrated solid-phase extraction-zone electrophoresis microchip

Integrated solid-phase extraction-zone electrophoresis (SPE-ZE) device has been designed and fabricated on microchip. The structures were fabricated by using multiple layers of SU-8 polymer with a novel technique that enables easy alignment and high yield of the chips. SU-8 adhesive bonding has two major advantages: it enables bonding of high aspect ratio pillars and it results in fully SU-8 microchannels with uniform electrokinetic flow properties. The SPE-ZE device has a fluidic reservoir with 15:1 high aspect ratio pillars for bead filters that act as a SPE part in the chip structure. The separation unit is a 25 mm long electrophoresis channel starting from the outlet of SPE reservoir. Argon laser-induced fluorescence (LIF) detector was used to monitor simultaneously the SPE reservoir and the detection site at the end of the electrophoresis channel. Flow characteristics and electric field distributions were simulated with Femlab software. Fluorescein was used as the analyte for detecting the operational performance of the chip. Adsorption, bead rinsing, elution and detection were tested to verify functioning of the chip design.     

Fabrication of enclosed SU-8 tips for electrospray ionization-mass spectrometry

We describe a novel electrospray tip design for MS which is fabricated completely out of SU-8 photoepoxy. A three-layer SU-8 fabrication process provides fully enclosed channels and tips. The tip shape and alignment of all SU-8 layers is done lithographically and is therefore very accurate. Fabrication process enables easy integration of additional fluidic functions on the same chip. Separation channels can be made with exactly the same process. Fluidic inlets are made in SU-8 during the fabrication process and no drilling or other postprocessing is needed. Channels have been fabricated and tested in the size range of 10 microm x 10 microm-50 microm x 200 microm. Mass spectrometric performance of the tips has been demonstrated with both pressure-driven flow and EOF. SU-8 microtips have been shown to produce stable electrospray with EOF in a timescale of tens of minutes. With pressure driven flow stable spray is maintained for hours. Taylor cone was shown to be small in volume and well defined even with the largest channel cross section. The spray was also shown to be well directed with our tip design.     

Feasibility of gas chromatography-microchip atmospheric pressure photoionization-mass spectrometry in analysis of anabolic steroids

Mass spectrometers equipped with atmospheric pressure ion sources (API-MS) have been designed to be interfaced with liquid chromatographs (LC) and have rarely been connected to gas chromatographs (GC). Recently, we introduced a heated nebulizer microchip and showed its potential to interface liquid microseparation techniques and GC with API-MS. This study demonstrates the feasibility of GC-microchip atmospheric pressure photoionization-tandem mass spectrometry (GC-μAPPI-MS/MS) in the analysis of underivatized anabolic steroids in urine. The APPI microchip provides high ionization efficiency and produces abundant protonated molecules or molecular ions with minimal fragmentation. The feasibility of GC-μAPPI-MS/MS in the analysis of six selected anabolic steroids in urine samples was studied with respect to intra-batch repeatability, linearity, linear range, and limit of detection (LOD). The method showed good sensitivity (LODs 0.2-1 ng/mL), repeatability (relative standard deviation<10%), and linearity (regression coefficient≥0.9995) and, therefore, high potential for the analysis of anabolic steroids. Quantitative performance of the method was tested with two authentic urine samples, and the results were in good agreement with those obtained with conventional GC-electron ionization-MS after derivatization.     

Lightweight lignocellulosic foams for thermal insulation

Foams are mainly composed of dispersed gas trapped in a liquid or solid phase making them lightweight and thermally insulating materials. Additionally, they are applicable for large surfaces, which makes them attractive for thermal insulation. State-of-the-art thermally insulating foams are made of synthetic polymeric materials such as polystyrene. This work focuses on generating foam from surfactants and renewable lignocellulosic materials for thermally insulating stealth material. The effect of two surfactants (sodium dodecyl sulphate (SDS) and polysorbate (T80)), two cellulosic materials (bleached pulp and nanocellulose), and lignin on the foaming and stability of foam was investigated using experimental design and response surface methodology. The volume-optimized foams determined using experimental design were further studied with optical microscopy and infrared imaging. The results of experimental design, bubble structure of foams, and observations of their thermal conductivity showed that bleached pulp foam made using SDS as surfactant produced the highest foam volume, best stability, and good thermal insulation. Lignin did not improve the foaming or thermal insulation properties of the foam, but it was found to improve the structural stability of foam and brought natural brown color to the foam. Both wet and dry lignocellulosic foams provided thermal insulation comparable to dry polystyrene foam.

Graphical abstract

     

Lab‐on‐a‐Chip Reactor Imaging with Unprecedented Chemical Resolution by Hadamard‐Encoded Remote Detection NMR

The development of microfluidic processes requires information‐rich detection methods. Here we introduce the concept of remote detection exchange NMR spectroscopy (RD‐EXSY), and show that, along with indirect spatial information extracted from time‐of‐flight data, it provides unique information about the active regions, reaction pathways, and intermediate products in a lab‐on‐a‐chip reactor. Furthermore, we demonstrate that direct spatial resolution can be added to RD‐EXSY efficiently by applying the principles of Hadamard spectroscopy.     

Microchip capillary electrophoresis–electrospray ionization–mass spectrometry of intact proteins using uncoated Ormocomp microchips

We present rapid (<5 min) and efficient intact protein analysis by mass spectrometry (MS) using fully microfabricated and monolithically integrated capillary electrophoresis–electrospray ionization (CE–ESI) microchips. The microchips are fabricated fully of commercial inorganic–organic hybrid material, Ormocomp, by UV-embossing and adhesive Ormocomp–Ormocomp bonding (CE microchannels). A sheath-flow ESI interface is monolithically integrated with the UV-embossed separation channels by cutting a rectangular emitter tip in the end with a dicing saw. As a result, electrospray was produced from the corner of chip with good reproducibility between parallel tips (stability within 3.8–9.2% RSD). Thanks to its inherent biocompatibility and stable (negative) surface charge, Ormocomp microchips enable efficient intact protein analysis with up to ∼10⁴ theoretical separation plates per meter without any chemical or physical surface modification before analysis. The same microchip setup is also feasible for rapid peptide sequencing and mass fingerprinting and shows excellent migration time repeatability from run to run for both peptides (5.6–5.9% RSD, n = 4) and intact proteins (1.3–7.5% RSD, n = 3). Thus, the Ormocomp microchips provide a versatile new tool for MS-based proteomics. Particularly, the feasibility of the Ormocomp chips for rapid analysis of intact proteins with such a simple setup is a valuable increment to the current technology.     

A microfabricated micropillar liquid chromatographic chip monolithically integrated with an electrospray ionization tip

We present the first monolithically integrated silicon/glass liquid chromatography-electrospray ionization microchip for mass spectrometry. The microchip is fabricated by bonding a silicon wafer, which has deep reactive ion etched micropillar-filled channels, together with a glass lid. Both the silicon channel and the glass lid have a through-wafer etched sharp tip that produces a stable electrospray. The microchip is also compatible with laser induced fluorescence (LIF) detection, due to the glass lid. Separation of drugs in less than 5 minutes using either SiO(2) (normal phase) or C(18) coated (reversed-phase) pillars with good sensitivity was demonstrated with mass spectrometric detection as well as separation of fluorescent compounds with LIF detection.     

Analysis of amphetamines and fentanyls by atmospheric pressure desorption/ionization on silicon mass spectrometry and matrix-assisted laser desorption/ionization mass spectrometry and its application to forensic analysis of drug seizures

The suitability of atmospheric pressure desorption/ionization on silicon mass spectrometry (AP-DIOS-MS) and matrix-assisted laser desorption ionization mass spectrometry (AP-MALDI-MS) for the identification of amphetamines and fentanyls in forensic samples was studied. With both ionization techniques, the mass spectra recorded showed abundant protonated molecules, and the background did not disturb the analysis. The use of tandem mass spectrometry (MS/MS) allowed unambiguous identification of the amphetamines and fentanyls. AP-DIOS-MS/MS and AP-MALDI-MS/MS were also successfully applied to the identification of authentic compounds from drug seizures. Common diluents and tablet materials did not disturb the analysis and compounds were unequivocally identified. The limits of detection (LODs) for amphetamines and fentanyls with AP-DIOS-MS/MS were 1-3 pmol, indicating excellent sensitivity of the method. The LODs with AP-MALDI-MS/MS were about 5-10 times higher.     

Environmental and food analysis by desorption atmospheric pressure photoionization‐mass spectrometry

Desorption atmospheric pressure photoionization‐mass spectrometry (DAPPI‐MS) is a versatile surface analysis technique for a wide range of analytes, especially for neutral and non‐polar analytes. Here, a set of analytes typically found in environmental or food samples was analyzed by DAPPI‐MS. The set included five polyaromatic hydrocarbons (PAHs), one N‐PAH, one brominated flame retardant, and nine pesticides, which were studied with three different spray solvents: acetone and toluene in positive ion mode, and anisole in negative ion mode. The analytes showed [M + H]⁺, M^+?, and [M–H]^? ions as well as fragmentation and substitution products. Detection limits for the studied compounds ranged from 30 pg to 1 ng (from 0.14 to 5.6 pmol). To demonstrate the feasibility of the use of DAPPI‐MS two authentic samples – a circuit board and orange peel – and a spiked soil sample were analyzed. Tetrabromobisphenol A, imazalil, and PAHs were observed from the three above‐mentioned samples, respectively. The method is best suited for rapid screening analysis of environmental or food samples. Copyright © 2010 John Wiley & Sons, Ltd.