[36] High-sensitivity sequencing with a gas-phase sequenator

Author(s):  
Michael W. Hunkapiller ◽  
Rodney M. Hewick ◽  
William J. Dreyer ◽  
Leroy E. Hood
Keyword(s):  
Author(s):  
André Ahrens ◽  
Stefan Zimmermann

AbstractIon mobility spectrometers can detect gaseous compounds at atmospheric pressure in the range of parts per trillion within a second. Due to their fast response times, high sensitivity, and limited instrumental effort, they are used in a variety of applications, especially as mobile or hand-held devices. However, most real-life samples are gas mixtures, which can pose a challenge for IMS with atmospheric pressure chemical ionization mainly due to competing gas-phase ionization processes. Therefore, we present a miniaturized drift tube IMS coupled to a compact gas chromatograph for pre-separation, built of seven bundled standard GC columns (Rtx-Volatiles, Restek GmbH) with 250 μm ID and 1.07 m in length. Such pre-separation significantly reduces chemical cross sensitivities caused by competing gas-phase ionization processes and adds orthogonality. Our miniaturized GC-IMS system is characterized with alcohols, halocarbons, and ketones as model substances, reaching detection limits down to 70 pptv with IMS averaging times of just 125 ms. It separates test mixtures of ketones and halocarbons within 180 s and 50 s, respectively. The IMS has a short drift length of 40.6 mm and reaches a high resolving power of RP = 68.


1997 ◽  
Vol 62 (12) ◽  
pp. 1832-1842 ◽  
Author(s):  
Hans P. Rebo ◽  
De Chen ◽  
Marit S. A. Brownrigg ◽  
Kjell Moljord ◽  
Anders Holmen

A novel microbalance technique has been used to study diffusion and adsorption in a commercial HZSM-5 zeolite. This new technique uses an inertial microbalance TEOM (Tapered Element Oscillating Microbalance) to measure mass changes in the zeolite bed. Time resolution as short as 0.1 s, a flow-through design where all the probe molecules see the zeolite bed and high sensitivity allowing zeolite loadings down to a few milligrams are the three most important properties of the TEOM. The probe molecules studied were o-xylene, p-xylene and toluene which were introduced at 303, 373 or 473 K and at partial pressures in the range of 0.2-10 kPa. The inverse characteristic uptakes (D/L2), corrected (D0/L2) and steady-state (Dss/L2) diffusion times are reported. The thermodynamic correction used for D0/L2 calculations almost eliminated the concentration dependence of the diffusivities. The Dss/L2 values were found to be rather unaffected by both temperature (373-473 K) and concentration, suggesting a certain degree of unification for diffusivities. o-Xylene uptake rates in the TEOM were found to be significantly higher than in a gravimetric microbalance under identical conditions, probably as a result of additional mass transfer resistance other than intracrystalline diffusion caused by poor contact between the gas phase and the zeolite in a conventional gravimetric microbalance.


1997 ◽  
Vol 502 ◽  
Author(s):  
A. N. Goyette ◽  
J. E. Lawler ◽  
L. W. Anderson ◽  
D. M. Gruen ◽  
T. G. Mccauley ◽  
...  

ABSTRACTWe have measured the steady state concentration of gas phase C2 in Ar/H2/CH4 and Ar/H2/C60 microwave plasmas used for the deposition of nanocrystalline diamond films. High sensitivity white light absorption spectroscopy is used to monitor the C2 density using the d 3 Π ← a3Π (0,0) vibrational band of C2 as chamber pressure, microwave power, substrate temperature and feed gas mixtures are varied in both chemistries. Understanding how these parameters influence the C2 density in the plasma volume provides insight into discharge mechanisms relevant to the deposition of nanocrystalline diamond.


2006 ◽  
Vol 329 (1-3) ◽  
pp. 222-229 ◽  
Author(s):  
Hubert Gnaser ◽  
Robin Golser

1997 ◽  
Vol 51 (2) ◽  
pp. 265-276 ◽  
Author(s):  
G. Tejeda ◽  
J. M. Fernández-Sánchez ◽  
S. Montero

The transformation of an old Raman double monochromator into a dual spectrometer capable of working either as the original instrument or as a very high sensitivity scanning single monochromator with multichannel charge-coupled device (CCD) array detection is described. The merits and limitations of this instrument, particularly suited for medium/low resolution (0.3 to 2 cm−1) Raman spectroscopy in the gas phase, are discussed. Example spectra of O2, N2, CO2, H2O, and CCl4 are shown.


2004 ◽  
Vol 82 (6) ◽  
pp. 873-879 ◽  
Author(s):  
Michael Jakubinek ◽  
Zhaoguo Tong ◽  
Sergei Manzhos ◽  
Hans-Peter Loock

Cavity ring-down (CRD) spectrometers used for analytical applications frequently have design requirements different from spectrometers used for gas-phase spectroscopic applications. A formalism that allows for maximization of the relative sensitivity by adapting the cavity length and absorption path through the sample is presented. These experimental configurations may not reduce the detection limit but do allow for a high sensitivity of the ring-down time measurement in the concentration range of interest. The formalism is applied to two common CRDS experimental configurations and to a fiber-loop ring-down experiment.Key words: cavity ring-down (CRD), absorption, detector, fiber-loop, sensitivity, detection limit.


2020 ◽  
Author(s):  
Claudio Codella ◽  
Cecilia Ceccarelli ◽  
Chin-Fei Lee ◽  
Marta De Simone ◽  
Eleonora Bianchi ◽  
...  

<p>The role of the pre-solar chemistry in the chemical composition of Solar System bodies is far to be understood. Did they inherit at least part of their composition from the earliest stages of star formation? During each step of the process leading to the formation of a Sun-like star and its planetary system, the molecular complexity increases from simple species up to interstellar Complex Organic Molecules (iCOMs, O-, N-, S-bearing species whit at least 6 atoms). In turn, iCOMs can be considered as bricks that can be used to assemble pre-biotic molecules. In this context, the study of the molecular complexity of Class 0 objects, where protostars are still deeply embedded in their parental core and still accreting their mass, is mandatory. As a matter of fact, protostellar radiation heats the surrounding medium creating the so-called hot-corinos, i.e. the regions of about 100 au with temperatures of at least 100 K, hot enough to (i) evaporate dust mantles, and (ii) trigger a warm gas phase-chemistry. As a consequence, the iCOMs abundances bloom, dramatically enriching the gas phase. The chemistry of the protostellar environments represents the first stage, and it needs to be compared with those of more evolved phase including relics of our pristine Solar System, such as comets.</p><p><span>The investigation of star-forming regions has enormously benefited from the recent advent of the IRAM-NOEMA and ALMA (sub-) mm-interferometers, which allowed the observers to reach Solar System scales. It is of paramount importance to combine high-sensitivity spectral surveys to collect large numbers of lines for each iCOM (for reliable identifications and to analyse excitation conditions) as well as to image their spatial distribution to investigate their association with different ingredients of the Sun-like star formation recipe (e.g. warm envelopes and cavities opened from hot jets, accretion disks, disk winds). The overall goal is to analyse the protostellar disk, i.e. the region where a Solar System will form billions of years later. The imaging of these regions with molecules simpler than iCOMs, such as CO or CS is indeed paradoxically hampered by their high abundances and consequently high line opacities which do not allow the observers to disentangle all the emitting components at these small scales.</span></p><p>In this respect, we will report recent results of a prototypical object such as IRAS4A, showing how complementing images obtained in the cm-spectral regime are to mimimise iCOMs emission hampering due to dust opacity. Finally, we will focus on the protostellar disk HH212, observed with a spatial resolution down to about 10 au. A large number of iCOMs, such as CH<sub>3</sub>OH, CH<sub>3</sub>CHO, HCOOCH<sub>3</sub>, CH<sub>3</sub>CH<sub>2</sub>OH, NH<sub>2</sub>CHO, have been imaged: their emission is clearly associated with the upper and lower rings in the outer part of the disk imaged using continuum emission. Indeed, the geometry of these features has led this source to be called a “space hamburger” in the popular press. We will discuss the possible explanations: (i) the disk has a vertically extended gaseous atmosphere (the “methanol buns”) and no gaseous methanol on the disk midplane (the “dusty meat”); (ii) the optically-thick disk midplane obscures iCOMs’ emission. The answer is essential to understand the gas composition in the equatorial plane, where planets will form.</p>


1995 ◽  
Vol 10 (5) ◽  
pp. 1108-1114 ◽  
Author(s):  
K.L. Menningen ◽  
C.J. Erickson ◽  
M.A. Childs ◽  
L.W. Anderson ◽  
J.E. Lawler

The gas phase densities of CH3 and CH and the hydrogen dissociation fraction are measured in a hot filament diamond deposition system for each of several different hydrocarbon input gases. The crystal growth rate and the appearance of the diamond grown from the different input gases are also examined. A comparison of the measurements indicates that the nature of the input hydrocarbon is relatively unimportant because fast gas phase reactions completely scramble the identities of the input carbon atoms. The addition of oxygen greatly alters the gas phase densities and other experimental factors such as the filament surface condition. Small concentrations of atomic impurities in the gas phase are also detected using high sensitivity absorption spectroscopy.


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