Sample bulking

Bulk Samples Bulk samples must be submitted for all silica analyses. They have two purposes (1) For laboratory use only, to confirm the presence of quartz or cristobalite in respirable samples, or to assess the presence of other substances that may interfer in the analysis of respirable samples. (2) To determine the approximate percentage of quartz (or cristobalite) in the bulk sample. A bulk sample submitted "for laboratory use only" must be representative of the airborne free silica content of the work environment sampled otherwise it will be of no value. The order of preference for an evaluation is ... 

The literature on sampling bulk materials is more specific and more quantitative than the general discussion presented above. Nevertheless, experiments on the sampling and subsampling procedures... 

Programmed- temperature splitless Liquid sample from syringe into cold inlet heat programming vaporises sample. Bulk of sample vapour enters column during splitless time venting (0.5-1 min) Dilute samples thermally labile Very broad, focusing required 0.1-2 80-95... 

Dynamic headspace GC-MS involves heating a small amount of the solid polymer sample contained in a fused silica tube in a stream of inert gas. The volatile components evolved on heating the sample are swept away from the sample bulk and condensed, or focused on a cryogenic trap before being introduced onto the chromatographic column via rapid heating of the trap. The technique can be used qualitatively or quantitatively DHS-GC-MS is considered to be well suited towards routine quantitative analysis. 

Direct solid sampling (bulk metal, thin film, compacted powder, solution residues)... 

ASTM D 4057-95 contains procedures for sampling bulk oil in tanks, barges, etc. 

Define sample, representative sample, composite sample, selective sample, random sample, bulk sample, primary sample, secondary sample, subsample, laboratory sample, test sample. 

Let us note in conclusion that under illumination the Dember photo-e.m.f. also occurs in the sample bulk along with the above-considered photo potential space-charge region. The contribution of this e.m.f. is rather small and can be taken into account, if necessary, by means of appropriate formulas (see, for example, Seeger, 1973). 

A high vacuum laser ion source is combined with a dynamic (ToF-MS) or static mass spectrometer (Mattauch-Herzog instrument) for the separation of the ion beams formed and used in LIMS for multi-element major, minor and trace analysis of compact solid samples (bulk analysis).74... 

The fi-y coincidence spectrometry technique has been used for low level 131I measurements in various environmental samples. The presence of other y emitters in the samples and the sample bulk have often required... 

Particle Size of Coal Sample Bulk Density (lb/ft3) Percent Voids... 

As a general TSCA rule, at each separate cleanup site we must take a minimum of three samples for each type of bulk PCB remediation waste or porous surface. There is no upper limit on the number of samples. Bulk PCB remediation waste includes, but is not limited to the following non-liquid PCB-contaminated media soil, sediments, dredged materials, mud, sewage sludge, and industrial sludge. Example 3.1 illustrates the application of this rule. 

Scheme II. Direct space representation of the STM interface. The junction is composed of two adjacent metallic blocks. Each block is divided into characteristic subparts that are stacked along the Z direction Sample bulk, Sample surface, Tip apex and Tip bulk. For clarity, ethylene molecules are schematically drawn at the sample surface on an Ag-oxide overlayer. White, black, light and dark grey circles depict C, H, Ag and O atoms respectively. The tip is composed of a W 111 surface upon which a cluster of W is adsorbed to model the apex.

In the following, those ion beam analysis techniques that allow for fluorine detection will be presented. By far, the most important technique in this respect is nuclear reaction analysis (NRA). Although it can be rather complex to perform, it is the most often applied technique for fluorine trace element studies, due to a number of convenient and prolific resonant nuclear reactions which make it very sensitive to fluorine in most host matrices. NRA is often combined with particle-induced X-ray emission (PIXE) which allows for simultaneous determination of the sample bulk composition and concentrations of heavier trace elements. By focusing and deflecting the ion beam in a microprobe, the mentioned techniques can be used for two- or even three-dimensional multi-elemental imaging. 

The EXAFS results reported for the untreated samples (see Section 8.3.4) led to the conclusion that Zn may form highly ordered inner-sphere sorption complexes with gibbsite surfaces or substitute into an octahedral Al-hydroxide layer of some sort. The use of sequential extraction enabled more concrete conclusions to be made. For the nonextracted soil samples (bulk and coarse), second-shell Al coordination numbers did not exceed four, in fine with the dioctahedral structure of gibbsite sheets (only two out of three metal positions are occupied). Elsewhere, a gradual increase was observed in Al coordination up to six with each extraction step, indicating that Zn is part of a fully occupied, trioctahedral Al-Zn2+ layer and not part of gibbsite or another dioctahedral Al compound.67 While dioctahedral Al-hydroxide layers are... 

The Rb based on the sample cannot be calculated correctly, since the electric charge transfer resistance and the electric double layer in an electrode interface are also detected as a resistance, even if bias voltage is impressed to the measurement cell in order to measure the ionic conductivity. For the ionic conductivity measurement, a dc four-probe method, or the complex-impedance method, is used to separate sample bulk and electrode interface [4]. In particular, the complex-impedance method has the advantage that it can be performed with both nonblocking electrodes (the same element for carrier ion and metal M) and blocking electrodes (usually platinum and stainless steel were used where charge cannot be transferred between the electrode and carrier ions). The two-probe cell, where the sample is sandwiched between two pohshed and washed parallel flat electrodes, is used in the ionic conductivity measurement by complex-impedance method as shown in Figure 6.1. 

We have used a new cell developed by INEL FUREQUI H. This cell is attached on a standard INEL 120 diffractometer with a Cu wavelength (A = 1.54056 A). The furnace allows to heat polycrystalline samples (bulk or powder) from room temperature m to 220°C. Because of its sealed chamber, it is possible to work under vacuum (around 10" bars) or in controlled vapour flowing conditions. The inner part of the furnace is constituted by ... 

ASTM D1900-94 (1994), Standard practice for carbon black-sampling bulk shipments, 12... 

Unambiguous steady-state measurements are carried out only in the trap-free space-charge-limited-current (SCLC) regime (23), when the average transit time (f j of any excess injected carrier across the sample bulk is shorter than the time required for the bulk to locally neutralize the carrier (22). The transit time ( r) has been defined in equation 1. The time to neutralize any excess injected carrier is the bulk dielectric relaxation time, Tr ( r = in which p is the bulk resistivity and e is the bulk dielectric... 

In contrast, when sampling bulk material, the material cannot generally be viewed as a set of distinct units. For example, we sample liquids from tanks, drums, and pipelines, and particulate solids such as ore, powders, and soil. Individual units cannot be identified for sampling. Rather, we must decide on a sample mass Mg or volume the chemical sample size. Further, we must be concerned about whether to composite samples, and, if so, how much to include in each increment of the composite. An additionaJ complication is the restriction on the sample mass that must be used in a chemical analysis due to the method or instrumentation. In fact, a subsample is usually taken in the lab. 

FIG. 14.15 (a) Schematic diagram of Fukuda and Sumaru s model The velocity of the mass transport at the top layer (vj follows the directions predicted by the field-gradient model. The velocity of mass uansport Iot the layss undmteath, y,. decreases as they lie deeper In the sample bulk, and is zero at the substrate. (b)Thc coordinate system for the model. 

It can be seen from Figure 4.1.6 that considering only the thermal conductivity, the sample temperature increases very slowly compared to that of the heating element when the sample thickness is not extremely small. Fortunately, other types of heat transfer take place simultaneously, and part of this effect is diminished. However, to avoid a temperature gradient in the sample bulk, the sample should cover the heating surface in a thin and uniform film. 

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