Selection of samples

Before a source analysis program is undertaken, it is important to decide which information is really required. Sampling sites must be selected with care. Choice of the site can significantly affect accuracy and cost. Care must also be taken in the selection of sampling points at the site. Measurement usually involves the deterrnination of temperature, concentration, and characterization of the gas contaminants. It also requires the mass rates of emission of each contaminant, therefore concentration and volumetric flow data are required. 

Naes, T., Isaksson, T., "Selection of Samples for Calibration in Near-Infrared Spectroscopy. Part I General Principles Illustrated by Example", Appl. Spec. 1989 (43) 328-335. 

Table II. Selection of Sample Size (Using Equation 8)...

Taylor, R. E., Radiocarbon Dating of Pleistocene Bone Toward Criteria for the Selection of Samples, Radiocarbon. 1980, in press. 

The performance of a solids mixer was assessed by calculating the variance occurring in the mass fraction of a component amongst a selection of samples withdrawn from the mixture. The quality was tested at intervals of 30 s and the data obtained are ... 

Fate-and-transport studies using computer modeling and mathematical calculations can effectively evaluate the potential for contaminant migration and degradation through the natural and anthropogenic processes active at the site. Often a brief fate-and-transport study early in the project can lead to optimal placement of monitor and recovery wells, and selection of sample analytical procedures. 

The predicted concentration-time profiles for all three formulations are shown in Figure 5 (panel a). These simulations use the fitted in vitro profiles for input to the model. For comparison, the simulations assuming zero order release are shown in panel b. Although the zero order simulations may be useful for initial specification of target profiles, they offer little of value for selecting specific formulations for the in vivo study or for study design (e.g., selection of sampling times),... 

Level 3 of the screen is designed to determine the cytotoxic selectivity of samples for tumor cells vs. normal cells. Where possible, the same patient s tissues are used. As in Level 2, six serial dilutions (of four- to five-fold each) are assayed in triplicate for each sample. The diluted samples are then added to the tumor cell and normal cell cultures, and the IC50 is determined. A "selectivity index" (SI) is determined based on the IC50 for normal cells/IC5Q for tumor cells. Samples with an SI of three or more are advanced to Level 4 of the screen. Additionally, only purified and well-characterized compounds are promoted for further testing. 

T. Isaksson and T. Ntes, Selection of samples for calibration in near-infrared spectroscopy. Part II selection based on spectral measurements, Appl Spectrosc., 44, 1152-1158 (1990). 

Selection of sampling frequency and duration will be determined primarily by the relevant standard, potential sources and resources. The current particulate standard is based on a 24-hour and annual average. Thus, sampling duration should probably not exceed 24 hours. 

In the selection of sampling media, an effort was made to use media that would be compatible with a limited number of inexpensive analytical methods. A conscious effort was made to develop methods that would be useful for a class of chemicals with limited success. 

Each instrument is dedicated to a specific analyte and shares the following common features. The sample inlet allows microprocessor-programmed selection of sample, zero, and calibrant gas. Rather than being programmed for continuous aspiration of the sampled air, the instrument is programmed to alternate between sample and zero with periodic (every 4... 

The electronic nose was used to have the first selection of sample to submit for further analyses, such as the volatile compounds and the volatile fatty acids for the study and the definition of the fermentations in progress, the electrophoresis determination of casein, chemical analyses and sensory analysis. 

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