Dual Inlet System Research Articles

Mass Spectrometric Methods for Determination of [13C]Leucine Enrichment in Human Muscle Protein

Two modified GC-based isotope ratio MS (IRMS) techniques, for measurement of [13C]leucine enrichment in muscle protein, were compared with a conventional dual inlet technique. Of these three, two involved HPLC purification of leucine and liberation of carbon dioxide (CO2) using the ninhydrin reaction. In the conventional technique the CO2was introduced into the MS by a dual inlet system following cryogenic concentration. In the second method (ninhydrin/GC/IRMS) the CO2was purified by on-line GC. In the third technique, GC/combustion/IRMS, derivatized amino acids are separated by GC and analyzed after combustion. A primed continuous infusion ofL-[1-13C]leucine was given intravenously to human subjects and needle quadriceps muscle biopsies were taken to measure [13C]leucine enrichment in muscle protein. All three methods demonstrated excellent correlation (r> 0.999). Differences in the measurement of [13C]leucine enrichment in muscle protein were <6%. The ninhydrin techniques require microgram quantities of leucine, with the conventional technique requiring twice the amount as the ninhydrin/GC/IRMS method. The GC/combustion/IRMS technique requires only nanogram quantities of leucine with similar precision enabling measurement of synthesis rates of individual proteins from biopsy samples. We have measured the isotopic enrichment of myosin heavy chain and mixed muscle protein in human subjects using the GC/combustion/IRMS technique.

Multipurpose Electrochemical Mass Spectrometry: A New Powerful Extension of Differential Electrochemical Mass Spectrometry

In previously reported setups for differential electrochemical mass spectrometry (DEMS), the mass spectrometer was usable only for this application. The present publication describes a novel setup which overcomes this limitation using a dual inlet system. One inlet is connected to a vacuum recipient at which the electrochemical cell is attached when operating in the DEMS mode. The other one consists of a capillary inlet which can be used for various mass spectrometry applications. Without the necessity of shutting down the vacuum system, it is possible to switch modes by just opening and closing two valves. The present publication describes the connection to a thermogravimetric analyzer (TGA) via the capillary inlet. Using this setup, it is possible to detect thermal decomposition products as a function of temperature in addition to the determination of the weight loss. Additionally, the characteristic response time of the multipurpose electrochemical mass spectrometry (MPEMS) operating in the DEMS mode has been substantially improved compared to previous setups (20 to 50 ms in comparison to 200 to 500 ms). Thus, higher scan rates than the typical are now practical. Using sputtered electrodes, scan rates as high as can be applied. As indicated by the features described above, MPEMS is a versatile instrument with a wide range of applications not only in electrochemistry, but also in general analytical chemistry.

Refinement and evaluation of an automated mass spectrometer for nitrogen isotope analysis by the Rittenberg technique

An apparatus designed to automatically perform hypobromite oxidations of ammonium salt samples for nitrogen isotope analyses with a mass spectrometer was modified to improve performance and reduce analysis time. As modified, reference N2 is admitted to the mass spectrometer between samples from a dedicated inlet manifold, for calibration at the same pressure as that of the preceding sample. Analyses can be performed on samples containing 10 μg to 1 mg of N (or more), at a rate of up to 350 samples/day. When operated with a double-collector mass spectrometer, the standard deviation at the natural abundance level (10 analyses, 50-150 μg N) was <0.0001 atom % 15N. Very little memory was observed when natural abundance samples (0.366 atom % 15N) were analysed. following samples containing 40 atom % 15N. Analyses in the range, 0.2 to 1 atom % 15N (50-150 μg N), were in good agreement with manual Rittenberg analyses (1 mg N) using a dual-inlet system, and precision was comparable. For enrichments of 2 to 20 atom % 15N, automated analyses were slightly lower than manual analyses, which was attributed to outgassing of N2 from the plastic microplate used to contain samples.

A new integrated system for simultaneous TG-DTA-MASS spectrometry

A new integrated TG-DTA-MS system is described based upon a simultaneous TG-DTA unit coupled to a 200 amu range microprocessor controlled quadrupole mass spectrometer. An inert sampling facility and bakeable dual inlet system allow runs to be performed in a wide range of atmospheres, at temperatures up to 1500°C.

An automatic inlet system with pneumatic changeover valves for isotope ratio mass spectrometer

The system described incorporates two pneumatically operated changeover valves, of a new design, with electrically heated capillaries in the dual-inlet system, which reduce the instrumental effects of this system to a negligible level. The changeover valves show many advantages such as high accuracy of closure, fast establishment of steady conditions after switching, simple construction and automatic control. Information on installation of stainless steel capillaries is also included.

BEACH HAVEN AND LITTLE EGG INLETS, A CASE STUDY

A comprehensive investigation of coastal processes active within and in the vicinity of Beach Haven and Little Egg Inlets was completed as part of the Coastal Processes Investigation for the proposed Atlantic Generating Station. The suspected complex nature of this dual natural inlet system was documented and a process-response model is presented to relate the more significant physical forcing functions to observed morphologic and hydraulic changes. A rising sea level, a net littoral drift from the north and the sediment scouring power of the flow in the two main channels serving the tidal basins are the principal factors related to the geographic and hydraulic stability of the system. The results of the study can be used to evaluate the potential impact, if any, of the proposed Atlantic Generating Station on the adjacent coastal environment.

A 30 cm radius 90° sector double collecting mass spectrometer with a capacitor integrating detector for high precision isotopic analysis of carbon dioxide

The long term performance of a 30.48 cm radius 90° sector double collecting mass spectrometer using a novel automatic capacitor integrating detector for high precision isotopic analysis of carbon dioxide is described. The incorporation of a new design of changeover valve in the dual inlet system and other aspects of the design of the mass spectrometer have resulted in the reduction of all the instrumental corrections applicable to measured isotopic differences between sample and standard gases to a negligible level. Isotopic differences in the ratio of ratios ▪ can be determined routinely with a reproducibility (expressed as the 1σ standard deviation about the mean value obtained by replicate analysis) of better than ±0.002%. The efficiency of the ion source is about 5×10 −4 ions molecule −1. The leak correction has averaged 0.004±0.016‰ for the 46/(44+45) ratio and −0.025±0.008‰ for the 45/44 ratio. The sums of all the other instrumental corrections (background, valve mixing, and abundance sensitivity) are 1.00038 for δ46/(44+45) values and 1.00078 for δ45/44 values. These values compare favourably with published sums of correction factors which average about 1.03. The capacitor integrating detector has the advantages that the ion beam intensities are objectively averaged, it runs the mass spectrometer automatically once set up, and provides a digital output.