Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Sampling and measurement methods

There are a variety of sample collection and hydrocarbon analysis methods use in geochemical surveys for oil and gas deposits. In the case of free gas, samples are collected either in the atmosphere or, more usually, within the soil. For bound gas soil or rock is collected and the gas is liberated by one of several methods. In practice, however, it is rarely possible to determine solely free gas or solely bound gas. [Pg.155]


Future studies of biogenic emissions should be designed to include sufficient data for uncertainty analyses of flux estimates. It is also important to conduct intercomparisons ot different sampling and measurement methods, as well as the methods used for estimating emissions, i.e. the dynamic chamber vs the micrometerological methods. Additional data are required to confirm emission estimates for those environments which have been characterized, and to extend the emission estimates to environments which have not been studied. Studies in ecosystems such as tropical rain forests should include surveys designed to identify potential terrestrial "hot spots of volatile sulfur emissions. [Pg.8]

The most common form of monitoring for air contamination is by using samplers at a number of selected locations intended to be reasonably representative of the breathing zone of the workers. Usual sampling and measuring methods of airborne radioactivity are shown in Table 9.8. [Pg.419]

Sampling and measuring methods of airborne radioactive materials... [Pg.420]

In order to provide a more representative picture, sampling and analytical procedures such as automatic sequential sampling to provide composite samples over a period of time (usually 24 hours), continuous on-line monitoring, frequent sampling, or in-field measurement must be used. The first two involve the use of expensive equipment that requires a power supply, and needs to be deployed in a secure site, and the third would be expensive because of transport and labour costs. The last one can be considered as emerging techniques and represents a very useful alternative to current practice. Field techniques (both sampling and measurement methods) can be cost effective, and can provide a rapid representative overview of the parameter of interest. [Pg.42]

Many chemical component-s present in such aerosols are relatively stable they can be measured long after (days, week.s, or more) the aero.sol has been collected on a filter or impactor plate, for example. Short-lived reactive and/or volatile species such as peroxides and aldehydes are not usually determined. This may make it difficult to evaluate the health and ecological effects of aerosols because chemically reactive chemical species tend to be the most active biochemically. The chemical components present in the particles collected on a filter or impactor plate may react with each other when they are in close proximity. Particle deposits in filters or on surfaces may also react with molecular components of the gases flowing over them. Chemical reactions between the gas and aerosol may not affect mea.surement.s of metallic elements but may modify chemical speciation (compound form) on the collector surface. All of these factors must be taken into account in selecting sampling and measurement methods for aerosol chemical properties. [Pg.174]

Major integral sampling and measurement methods used for measuring atmospheric aerosols... [Pg.114]

The evaluation phase of industrial hygiene is the process of making measurements on some set of samples which permits a conclusion about the degrees of hazard. Before conducting an evaluation, it is necessary to make a number of choices of what and where to sample, when to sample, how long to sample, how many samples to take, what sampling and analytical methods to use, what exposure criteria to use in the analysis of the data, and how to report the results. These choices as a whole constitute the evaluation plan. The object is to find if one or more workers have an unacceptable probabiUty of being exposed in excess of some estabUshed limit. [Pg.106]

Operations capable of generating airborne beryUium particulate, such as melting, machining, welding, grinding, etc, are effectively controUed by local exhaust ventilation or other control measures. To assure a safe environment and measure compliance with the OSHA standards, employee exposures should be periodicaUy measured by prescribed air sampling and analytical methods. [Pg.69]

Measurement of specific chemical or biological contaminants can be very expensive. Before expending time and money to obtain measurements of indoor air pollutants, you must decide how the results will be used (e.g., comparison to standards or guidelines, comparison to levels in complaint-free areas) what substances(s) should be measured where to take, samples when to take samples what sampling and analysis method to use so that the results provide useful information. [Pg.225]

Author s comment] Because a general rendition of the Scientific Method cannot be cast in legally watertight wording, all possible outcomes of a series of measurements and pursuant actions must be in writing before the experiments are started. This includes but is not limited to the number of additional samples and measurements, and prescriptions on how to calculate and present final results. Off-the-cuff interpretations and decisions after the fact are viewed with suspicion. [Pg.277]

Cornelis R, De Kimpe J, and Zhang X (1998) Trace elements in clinical samples revisited -speciation is knocking at the door. Sample preparation, separation of the spedes and measurement methods. Spectrochim Acta 536 187-196. [Pg.102]

The logical approach to problem solving for rubber analysis at Polysar Ltd was described by Chu [73] (cf. Schemes 2.4 and 2.5). Systematic analysis involves sampling, elimination of interference and measurement. Methods employed include chromatography (GC, HS-GC, HPLC, SEC, IC), spectroscopy (AAS, UV/VIS, IR, NMR), MS, microscopy and thermal analysis. The specific role of each of these techniques for the analysis of rubber compounds with or without... [Pg.37]

The question that arises next is how automated laboratory methods can be applied in and/or should be adapted to plant control. In principle those methods can be devoted to this role191 193 provided that some additional field effects (see Table 5.1) are taken into account, viz., special sampling and measuring requirements we shall confine ourselves to these aspects and not consider extra safety measures against hazards such as contact explosions in plants. [Pg.372]

For this range of temperature, the experimental apparatus, the shape and geometrical factor g of the sample and the method of measurement (mean conductivity method) are different from those used for the very low-temperature range. [Pg.274]

A great number of methods have traditionally been used for sampling and measurement of odors. The need for a standard procedure has, in Europe, led to the development of a (draft) standard (CEN, 1999 Sneath and Clarkson, 2000). [Pg.180]

The second timescale involves equilibration of a food sample with the air or known relative humidity environment (e.g., saturated salt solutions, in the case of obtaining an isotherm). In this case, equilibration depends on the size of a sample, the measurement method used, and the nature of the sample being measured (this factor is related to the first timescale discussed previously, as illustrated with butter). For example, measuring the of 2 g of corn... [Pg.29]

The above flame retardants, HMPN and TMP, along with another commercially available alkyl phosphate, triethyl phosphate (TEP), were systematically characterized by Xu et al. To quantify the flammability of the electrolytes so that the effectiveness of these flame retardants could be compared on a more reliable basis, these authors modified a standard test UL 94 HB, intended for solid polymer samples, and measured the self-extinguishing time (SET) instead of the universally used flame propagation rate. Compared with the UL 94 HB, this new quantity is more appropriate for the evaluation of the electrolytes of low flammability, since the electrolytes that are determined to be retarded or nonflammable by this method all showed zero flame propa-... [Pg.163]

Slope/bias correction This method, which is really a postprocessing of model outputs, is one of the simplest improvement methods, and can be quite effective in cases where temporal shifts in analyzer response are expected [105]. However, when used, it should be accompanied by a well-defined sampling and measurement protocol, in order to generate a sufficiently large population of time-localized standards that can be used to determine stable estimates of slope and bias correction factors. [Pg.426]

Its related value was originally denoted as X- Numerous % values in terms of volume fractions are collected in Ref. [37]. Unfortunately the scatter in % values found in the literature is large as they reflect also both the polymer source (e.g., narrow molar mass fractions or anionically prepared samples) and the method of measurement, for example, light scattering, osmometry, or inverse gas chromatography. The interaction parameters g (%) for the polymer-good solvent systems assume values between 0 and 0.5 [37]. [Pg.453]

In 1971 when safety and health standards were established by the U. S. Department of Labor for several hundred chemical substances, there were analytical methods available for some of the compounds, but few were validated to ensure the accurate monitoring of the exposure of workers to these toxic substances (1). Consequently, programs were undertaken by the National Institute for Occupational Safety and Health (NIOSH) to develop and validate sampling and analytical methods. The initial intent was to provide methods that would be useful to industry in measuring the exposures of personnel to potentially toxic materials at concentration levels near the accepted standard levels. Consequently, many earlier methods were developed around the standard levels established by the Occupational Safety and Health Act with validation at, for example, levels ranging from one-half to twice the established standard level (2). Often these methods were not validated at lower concentration levels, say, one-tenth of the original level. [Pg.49]

We have presented a statistical experimental design and a protocol to use in evaluating laboratory data to determine whether the sampling and analytical method tested meets a defined accuracy criterion. The accuracy is defined relative to a single measurement from the test method rather than for a mean of several replicate test results. Accuracy here is the difference between the test result and the "true value, and thus, must combine the two sources of measurement error ... [Pg.512]

Note that the common analytical methods for determining the total organic material present in a sorbent often involve combusting the sample and measuring evolved... [Pg.291]

Modified filter sampling methods that are available will measure ambient levels of strong acid in ambient aerosol samples, and these methods do so with acceptable precision and accuracy [as indicated by the balance between measured anions and cations (56, 57)] in the absence of significant levels of particulate weak acids. Additional intercomparisons involving intrinsically different techniques for particulate strong acidity [e.g., IR spectroscopy (48), thermal speciation (38, 45), and filter methods (28)] are needed. Further information on the occurrence of various weak acids in airborne particles is needed, along with further studies of techniques for their specific determination in atmospheric aerosol samples. [Pg.249]

Water Chemistry. Sampling and analytical procedures, as well as quality control and assurance information for chemical and biological parameters, are described in detail elsewhere (e.g., 7-9). A brief summary of sampling and analytical methods is provided here. Water samples were collected biweekly during the ice-free season and every 5 weeks under the ice at depths of 0, 4, 6, 8, and 9 m in the north basin and 0, 4, and 6 m in the south basin. Water was pumped from depth by using a peristaltic pump and Tygon tubing and collected in prewashed polyethylene bottles. Alkalinity and pH were measured on unfiltered, unpreserved samples. [Pg.130]


See other pages where Sampling and measurement methods is mentioned: [Pg.90]    [Pg.172]    [Pg.155]    [Pg.222]    [Pg.90]    [Pg.172]    [Pg.155]    [Pg.222]    [Pg.14]    [Pg.108]    [Pg.152]    [Pg.231]    [Pg.51]    [Pg.279]    [Pg.342]    [Pg.162]    [Pg.192]    [Pg.95]    [Pg.15]    [Pg.2]    [Pg.4]    [Pg.505]    [Pg.755]    [Pg.371]    [Pg.152]    [Pg.108]    [Pg.45]    [Pg.95]   


SEARCH



Measuring sample

Sample measurements

Sample methods

Sampling methods

© 2024 chempedia.info