Sample carriers

Fig. 4.10. Fluorescence signal from small particles or thin films deposited on a silicon substrate used as sample carrier. The intensity was calculated for particles, thin films, or sections ofdiffe-rent thickness but equal mass of analyte, and plotted against the glancing angle f. A Mo-Ka beam was assumed for excitation. Particles or films more than 100 nm thick show double intensity below the critical angle of0.1° [4.21].

Prange et al. [809,810] carried out multielement determinations of the stated dissolved heavy metals in Baltic seawater by total reflection X-ray fluorescence (TXRF) spectrometry. The metals were separated by chelation adsorption of the metal complexes on lipophilised silica-gel carrier and subsequent elution of the chelates by a chloroform/methanol mixture. Trace element loss or contamination could be controlled because of the relatively simple sample preparation. Aliquots of the eluate were then dispersed in highly polished quartz sample carriers and evaporated to thin films for spectrometric measurements. Recoveries (see Table 5.10), detection limits, and reproducibilities of the method for several metals were satisfactory. 

Samples dissolved in organic solvents usually ignite in the discharge which may produce erratic emission. It is more prominent in the rotating-disc type sample carriers. 

The open-split interface dilutes eluted analytes with additional makeup gas and then splits the mixture into two fractions. An inert, fused-silica restrictor routes a portion of the sample-carrier gas mixture from the interface into the MS ionization chamber, whereas the remainder is vented to atmosphere. An open-split interface can affect the shapes and areas of peaks because solutes make contact with several items including the interface liner, the outer surfaces of the fused-silica column, and the restrictor, which can adsorb trace-level analytes if they are not properly deactivated (21). 

Containers for Explosives. Zimmer Asaoka (Ref 1) have investigated various materials as candidates for fabricating containers that safely hold comparatively large loads of expl materials. The inspiration for this study came from earlier work at DuPont which led to the development of tote barricades" to protect personnel, hand-carting sensitive material, from the effects of an accidental explosion. These barricades withstood the expln of 2 grams of NG. The new sample carrier, to be explosion-safe, was reqd to withstand a min load of 5g expl sample, and was to be fabricated from a material which would form harmless fragments upon detonation of the expl... 

In CG-direct-current plasma (DCP), a direct-current arc is struck between two electrodes as an inert gas sweeps between the electrodes carrying the sample. Carrier gases such as helium, argon, and nitrogen have been used. 

Two membrane types that operate on different principles have been used in commercially available membrane separators microporous membranes and selectively permeable, nonporous polyimide or Nafion membranes. The micro-porous Teflon PTFE membrane can be used to remove water vapor or organic solvent vapor. Any gaseous component, including volatile analytes such as Hg, is partially or extensively removed. The sweep gas flow rate is typically similar to the sample carrier gas flow rate. 

The selected samples were sent to the University of Maryland. They were opened in a Class 100 clean room and half of each filter was cut from the holder with a stainless steel scalpel, folded and transferred to an acid-washed polyethylene bag. The bags were placed into pneumatic tube sample carriers ("rabbits") along with standards and flux monitors, and irradiated in the National Bureau of Standards (NBS) reactor at a flux of 5 x 10 n/cm -sec. Gamma-ray spectra of the irradiation products were observed with Ge r-ray detectors using procedures discussed by... 

Fig. 8.5. Miniaturized biodevices for ultra-high-throughput screening. (A) Piezo-electric ink-jet pipettor that allows pipetting down to the pico-liter scale with speeds up to 10,000 drops per second and an accuracy of 3 % [97] (B) Sample carrier containing six segments of a silicon wafer. Each segment comprises 900 reaction compartments with a maximum volume of 120 nl each [28].

In the case of trace analysis of °Sr (e.g., in natural water samples), carriers, most often ionic species such as Sr", Ba", Ca", and Ee" should be used [39]. Ionic calcium is very similar to ionic strontium and should be removed from samples on the basis of differences between the solubility of calcium and strontium nitrates in... 

Just before the NMR analysis, the cell is placed in a glove box under helium and samples are transferred into the sample-carrier rotor which is then hermetically scaled. 

Curie-point pyrolyser A pyrolyser in which a ferromagnetic sample carrier is inductively heated to its Curie point. 

Fig. 1 Two devices that can be used to obtain a small representative sample from a larger supply. (A) Systematic representative sampling of a powder can be achieved with the spinning riffler (From Ref. ) (B) the spinning riffler is composed of several removable sample cups (C) chaos-generating devices, such as the free-fall tumbling mixer, can be used for powder homogenization and sampling (From Ref.t f) and (D) exploded view of the sample carrier.

A soil-gas sample collected by hollow probe needs no further preparation for injection into a GC system. However, the results obtained from sulphur analysis of a soil gas may be inaccurate representatives of their original state in the field. The time elapsed between collection of the sample in the field and analysis in the laboratory permits many changes in the sample. Some sulphur components may adsorb on the walls of the glass, plastic, or stainless-steel syringes or sample carriers used for sample transportation. Non-adsorbed components may interact with each other. The most reliable soil-gas analyses are those made almost immediately after collection. Even these analyses may not be completely accurate. 

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