Sampling equipment, purpose

Select the employee to be sampled and discuss the purpose of the sampling. Inform the employee when and where the equipment will be removed. Stress the importance of not removing or tampering with the sampling equipment. Turn off or remove sampling pumps before an employee leaves a potentially contaminated area (such as when he/she goes to lunch or on a break). 

Equipment blanks enable us to assess the collected sample representativeness. The purpose of collecting equipment blanks is to detect the presence of contamination from the sampling equipment itself or any cross-contamination with previously collected samples. For example, metal liners for core barrel or split spoon samplers are not always precleaned by the manufacturer or distributor. They must be cleaned in the field prior to sampling to eliminate the potential for sample contamination. 

Many improvements have been made to streamline performance and to reduce machine operation labor. Some of these are tensionless jigs using variable speed electric motors with built-in drag for brakes, automatic reversing equipment, and automatic temperature and level controls. These machines are widely used for goods that are easily creased, such as fabrics consisting of filament acetate, heavy filament nylon, or cotton duck. They are also convenient for small dye lots and for sampling purposes. 

The review should emphasize developing an understanding of the processing sequence, the equipment, the equipment plot, the operating conditions, instrument and sample locations, the control decisions, and the operators perspectives. Wmle the preparation effort may be less for those who have been responsible for the unit for a long period of time, the purpose of the test requires that the types and locations of the measurements be different from those typically recorded and typically used. The condition of these locations must be inspected. Operating specifications may be different. Therefore, refreshment is always necessaiy... 

The methods that have been discussed require specially designed instruments. Laboratories without such instruments can measure these gases using general-purpose chemical analytical equipment. A compendium of methods for these laboratories is the "Manual on Methods of Air Sampling and Analysis"published by the American Public Health Association. (10). 

Analytical methods available to labbratories with only general-purpose analytical equipment may be found in the "Methods of Air Sampling and Analysis" cited at the end of the previous section. 

Sanq>ling With Capillaries. Earlier it was pointed out that with the aid of a constriction pipette a sample can be measured accurately. A similar effect can be obtained by allows ing the serum to enter a capillary open at both ends. The serum will reach the opposite end of the capillary if it is held at an angle and then stoppered, and if the capillary has been carefully calibrated an accurate volume can be measured out. Such capillaries are now available commercially, and have been in use in automated equipment in the authors laboratory for at least 10 years. It is now possible to take the capillary and empty its contents into a container for analysis, or into a stream for the purpose of determining any of the materials which can be determined with the autoanalyzer. Figure 33 shows an instrument which is used for this purpose (58). 

It is clear that neither NMEA nor NDPA is appropriate for an internal standard in NDMA determination if criteria are interpreted strictly, but both compounds have been used for this purpose. Addition of a nitrosamine, not normally present in the sample, is helpful in detecting any gross errors in the procedure, but the addition should not be considered to be internal standardization. Utilization of NMEA or NDPA to indicate recovery of NDMA can lead to significant errors. In most reports of the application of these "internal standards", recovery of all nitrosamines was close to 100%. Under these conditions, any added compound would appear to be a good internal standard, but none is necessary. NDMA is a particularly difficult compound for use of internal standardization because of its anomalous distribution behavior. I mass j ectrometry is employed for quantitative determination, H- or N-labeled NDMA could be added as internal standard. Because the labeled material would coelute from GC columns with the unlabeled NDMA, this approach is unworkable when GC-TEA is employed or when high resolution MS selected ion monitoring is used with the equipment described above. 

For this purpose we studied a temperature-programmed interaction of CH with a-oxygen. Experiments were carried out in a static setup with FeZSM-5 zeolite catalyst containing 0.80 wt % Fe203. The setup was equipped with an on-line mass-spectrometer and a microreactor which can be easily isolated from the rest part of the reaction volume. The sample pretreatment procedure was as follows. After heating in dioxygen at 823 K FeZSM-5 cooled down to 523 K. At this temperature, N2O decomposition was performed at 108 Pa to provide the a-oxygen deposition on the surface. After evacuation, the reactor was cooled down to the room temperature, and CH4 was fed into the reaction volume at 108 Pa. 

In those cases where there are any doubts about the feasibility of producing a sufficiently homogeneous and stable reference material, a feasibility study might be needed. For this study, an extra amount of material is needed. Questions regarding the best way of preparing the sample, the stability of the material, or the fitness for purpose might justify the inclusion of a feasibility study in the project. In the BCR projects, it is common practice to have a feasibility study, which usually has as the sole purpose of assessing the performance of the laboratories in the collaborative study in relation to the certification of the reference material. The feasibility study allows the participants to fine-tune their equipment, their methods, and their procedures in view of the characterization measurements. In each of these cases, a considerable extra number of samples is needed. 

In the preparation of many solid state reference materials, reduction of the grain size plays an important role. Usually this reduction is required because of the measurement methods to be used both in the projects and later by the users of the reference material, as well as to come to an acceptable minimum sample intake. The minimum sample intake can be defined as the minimum amount of material needed, so that the heterogeneity of the material does not affect the repeatability of the measurement method. The reduction of the grain size is usually implemented by crushing and/or grinding techniques. The techniques employed and the equipment used must be suitable for the purpose of processing the material. Potential problems of contamination, loss of volatile components, and/or other physical and... 

The location of the position of double bonds in alkenes or similar compounds is a difficult process when only very small amounts of sample are available [712,713]. Hass spectrometry is often unsuited for this purpose unless the position of the double bond is fixed by derivatization. Oxidation of the double bond to either an ozonide or cis-diol, or formation of a methoxy or epoxide derivative, can be carried out on micrograms to nanograms of sample [713-716]. Single peaks can be trapped in a cooled section of a capillary tube and derivatized within the trap for reinjection. Ozonolysis is simple to carry out and occurs sufficiently rapidly that reaction temperatures of -70 C are common [436,705,707,713-717]. Several micro-ozonolysis. apparatuses are commercially available or can be readily assembled in the laboratory using standard equipment and a Tesla coil (vacuum tester) to generate the ozone. Reaction yields of ozonolysis products are typically 70 to 95t, although structures such as... 

The popularity of MAE methods for in-polymer additive analysis is reflected in a limited list of reported applications. This is both on account of the former lack of dedicated microwave equipment designed specially for small analytical samples and the relatively recent commercial introduction of the technique. Microwave extraction for analytical purposes is a relatively new growth area [441]. 

Cleaning is a form of maintenance which is particularly relevant where a piece of equipment is used repeatedly, but is also applicable to decontamination of equipment after use in dirty environments. The purpose of cleaning is to ensure that when the piece of equipment is used for an application or measurement, the risk of contamination from previous samples, chemicals, standards or the laboratory environment will be minimized. In the majority of cases, the process of cleaning introduces new chemicals to whatever is being cleaned. After cleaning, the equipment must be well rinsed to remove all traces of the cleaning chemicals, and then dried. 

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