Sample transfer system

Irradiations for conventional INAA, PNAA, and RNAA are usually performed using a pneumatic sample transfer system (rabbit system) normally available in the reactor. In some cases, a hydraulic system is employed. For ENAA, samples can be irradiated in specially built pneumatic sites fitted with thermal neutron shields (e g., Cd, B, Gd). The samples may also be wrapped in one of these shields and placed in a conventional rabbit system. 

A sample recycling pneumatic rabbit system must be made available for CESIAA. It is essential that the recycling system be installed as close as possible to the reactor so that the sample transfer time is minimal. Consideration must be given to the type and level of radiation in the surrounding areas so that the gamma ray spectrum of a sample is not influenced by the background radiation. 

The sizes of the vials that can be used for INAA depend on the sizes of the rabbits. The rabbit size is dependent on the installed rabbit system. Large sample irradiations are usually done outside the immediate vicinity of the reactor core, and their sizes will vary depending on the reactor type. 

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A system has been constructed which allows combined studies of reaction kinetics and catalyst surface properties. Key elements of the system are a computer-controlled pilot plant with a plug flow reactor coupled In series to a minireactor which Is connected, via a high vacuum sample transfer system, to a surface analysis Instrument equipped with XFS, AES, SAM, and SIMS. When Interesting kinetic data are observed, the reaction Is stopped and the test sample Is transferred from the mlnlreactor to the surface analysis chamber. Unique features and problem areas of this new approach will be discussed. The power of the system will be Illustrated with a study of surface chemical changes of a Cu0/Zn0/Al203 catalyst during activation and methanol synthesis. Metallic Cu was Identified by XFS as the only Cu surface site during methanol synthesis. 

Sample Introduction and Transfer System. The sample Introduction and sample transfer system is a lengthened version of the PHI Model 15-720B Introduction system which consists of a polymer bellows-covered heating and cooling probe, a transferable sample holder, an eight-port dual-axis cross, and the mlnlreactor Interface port and transfer probe (Figure 2). There Is also a transfer vessel port with the necessary transfer probe for Introduction of air sensitive samples. They are not part of the reactor/surface analysis system. The dual cross and attached hardware are supported by the probe drive mechanism which floats on a block driven vertically and transversely by two micrometers. These micrometers plus the probe drive mechanism allow X-Y-2... 

Figure 2. Sample Introduction and sample transfer system. (Reproduced with permission from Ref. 7. Copyright 1984, Academic Press.)...

The corrosion of stainless steel in 0.1 mol-1 NaCl solutions at open circuit potential was studied in detail by Bruesch et al. [106] using XPS in combination with a controlled sample transfer system [38]. It was verified by XPS analysis that the passivating film contains chromium oxide. The position and the height of the Cr concentration maximum depends critically on the bulk chromium content of the steel. Significant variations in the electrode passivation properties were observed at a Cr concentration of 12%, while the film behaviour was found to be rather independent of the other components like Mo, Ni, Cu. From the fact that the film structures and... 

Another approach is to perform ex situ reactions and insert the sample into a high vacuum system without exposure to ambient conditions. Incorporating N2 glove boxes or reactor systems with X-ray photoelectron spectroscopy (XPS) sample handling can also provide information that is closer to operational conditions. In a similar manner ex situ reactions and sample handling are starting to be apphed to electron microscopy studies. Commercially available sample transfer systems will accelerate the application of this methodology. 

Hydride/vapour generation techniques provide extremely good sensitivity. When coupled to continuous flow methodologies for use in routine analysis, simple and reliable analytical techniques are provided. TTie extension of chemistries and sample transfer systems to provide analytical protocols to cope with a wider range of elemental analyses should be pursued in the search for lower detection levels. While multi-element techniques offer very low levels of detection, the use of specific single element analytical instruments with detection capabihties similar to those described above may be the best route for routine laboratories with high sample throughput. 

UHV surface preparation and analysis chamber, a variable pressure STM chamber, and a load lock and sample transfer system. Fig. 11 shows a schematic of the system. 

The majority of the applications of 14 MeV neutron activation analysis involve the use of short-lived indicator radionuclides. Therefore, it is essential that the sample be returned quickly to the counting station following irradiation. Pneumatic sample transfer systems employing compressed nitrogen, or a vacuum are most commonly used 34-35>. An inexpensive system may be constructed from ordinary low density polyethylene tubing 18>. Irradiation, delay and counting times are ordinarily controlled by means of preset timing circuits. Completely automated control and transfer systems are available commercially. 

Time variations in the intensity of the flux during irradiation. This is an important consideration only when a single sample transfer system is used. Gas-filled BF3 neutron counter tubes are often used to monitor the neutron flux in order to normalize the data when the sample and the standard are not irradiated simultaneously. Gain shifts and dead-time effects associated with the use of neutron monitoring detectors also contribute to the errors associated with a single sample transfer system. 

Inaccurate calibration of relative counting efficiencies. In the use of a dual sample transfer system where both sample and standard are counted simultaneously with different counters it is important that the relative efficiencies of the two counting systems be accurately determined and that these efficiencies do not vary with time. These errors may be partly compensated for by irradiating the same sample and standard several times and alternately reversing the sample and standard counting positions. 

In the irradiation of Tc with thermal neutrons, the short-lived (15.8 s) Tc isotope is produced and can be detected by either gamma spectrometry or a low-background beta counter. Analysis can be performed only with a last sample transfer system. Both pre- and... 

The pneumatic sample transfer system within OSL/RRP is connected to the operator s automatic sampling and sample transfer systems. Inspection sampling jugs are fed into the... 

S. S. Ismail A New Automated Sample Transfer System for Instrumental Neutron Activation Analysis , Journal of Automated Methods and Management in Chemistry, Volume 2010 (2010), Article ID 389374, 8 pages... 

Electrophoretic mobilities were measured with a Zeta Meter (ZM 77) apparatus fitted with an automatic sample transfer system. Samples of about 5... 

In principle, the sample transfer from the Supercritical state is relatively easily adaptable to other systems, due to the high volatility of the fluid at atmospheric pressure, particularly for carbon dioxide which is the most frequently used fluid. 

Another application of SFC-GC was for the isolation of chrysene, a poly aromatic hydrocarbon, from a complex liquid hydrocarbon industrial sample (24). A 5 p.m octadecyl column (200 cm X 4.6 mm i.d.) was used for the preseparation, followed by GC analysis on an SE-54 column (25 m X 0.2 mm i.d., 0.33 p.m film thickness). The direct analysis of whole samples transferred from the supercritical fluid chromatograph and selective and multi-heart-cutting of a particular region as it elutes from the SFC system was demonstrated. The heart-cutting technique allows the possibility of separating a trace component from a complex mixture (Figure 12.21). 

NC samples were irradiated for 3 min and TNT and HMX for 1 min at a 14 MeV neutron flux of approx 108n/cmasec, Simultaneous counting was performed by means of a matched dual 7.6x7.6cm flat Nal crystal detector assembly in conjunction with a Kaman Nuclear programmed timer system for automatic sample transfer, A one-min count time was usually sufficient to exceed 10 counts. The signal from each de-... 

Ion extraction. The aspirated or laser ablated sample is transported from the sample introduction system into the center of the torch by a 1 1/min flow of Ar carrier gas where it is immediately dissociated and ionized by energy transfer with the hot -6000 K temperature of the surrounding Ar plasma. Ionization efficiencies are >95% for U and Th (Jarvis et al., 1992). For laser ablation sampling, helium may be employed as the carrier... 

Sample preparation, injection, calibration, and data collection, must be automated for process analysis. Methods used for flow injection analysis (FLA) are also useful for reliable sampling for process LC systems.1 Dynamic dilution is a technique that is used extensively in FIA.13 In this technique, sample from a loop or slot of a valve is diluted as it is transferred to a HPLC injection valve for analysis. As the diluted sample plug passes through the HPLC valve it is switched and the sample is injected onto the HPLC column for separation. The sample transfer time typically is determined with a refractive index detector and valve switching, which can be controlled by an integrator or computer. The transfer time is very reproducible. Calibration is typically done by external standardization using normalization by response factor. Internal standardization has also been used. To detect upsets or for process optimization, absolute numbers are not always needed. An alternative to... 

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