Timings of Sample Collections

When the well depth or diameter is unknown or a water-level measurement is not possible, purging should be carried out by pumping the well for a pre-determined period of time (e.g., at least 30min). Measurement of groundwater parameters should be monitored at intervals during the purging process and at the time of sample collection (Figure 3). 

The goal of a groundwater monitoring plan for pesticides is to produce water samples that are representative of the aquifer under study at the time of sample collection. Materials and methods must be established prior to implementing a monitoring program... 

The times of sample collection for a single paddy survey are set with respect to the application time, such as just before an application, immediately after, and 1, 3, and 7 days post-application, and at longer intervals as appropriate. For an area survey of water and waterway sediments, samples are usually collected periodically over a cultivation season focusing on the application time. 

Measurable levels of endrin have not been found in adipose tissue of the general population (Stanley 1986 Williams et al. 1984). Measurable tissue concentrations of endrin have been observed in cases of acute poisoning. The time of sample collection is critical as endrin residues in tissues decline rapidly after exposure has ceased. 

Acylcarnitine profiles are dependent on the clinical status of the patient at the time of sample collection [56, 57]. It is therefore important to provide the biochemical genetics laboratory with information regarding the clinical context during which the sample was collected. The laboratory must be conscientious of the fact that carnitine deficiency states can be associated with acylcarnitine profiles that lack any acylcarnitine species that are elevated above the reference range. Therefore, it is essential that the complete profiles are reviewed and even borderline elevated acylcarnitines should prompt further follow up in the presence of abnormally low free acetylcar-nitine (Fig. 3.2.2). If clinically indicated, a repeat sample should be collected at least 24 h after L-carnitine supplementation. 

The radiolead 210Pb activity is estimated on the basis of 210Po in growth after the lead fraction has been purified and stored for several months (up to two years) (procedure 6). The 210Pb activity at the time of sample collection is calculated from... 

T6 the ambient air temperature at the site and time of sample collection. 

In the first three samples of Table 13.6 the noble gas deduced temperature, T3, differs from the ambient air temperature at the time of sample collection, T6, revealing no equilibration at the point of emergence (in agreement with the previous paragraph). The last spring (Fara), however, shows T3 = T6. This water issues below a slope of tallus, and equilibration of noble gases could take place prior to sample collection. 

The ionisation chamber and the alpha scintillometer lend themselves best to the instantaneous mode of Rn determination because of their higher sensitivity compared to other methods. In this mode, the time of sample collection and analysis are of the order of minutes. Both instruments are also known as emanometers and both depend on a system of taking a soil-gas sample, usually by pounding a hollow rod into the ground. 

Interpretation of a negative result requires the consideration of assay sensitivity and efficiencies of nucleic acid extraction and amplification. A false-negative result may be caused by mhibition of or decreased efficiency of amplification, and proper controls for this have been described above. Insufficient sample, inappropriate specimen type, inappropriate timing of sample collection, and degradation of nucleic acid during transport and handling are other sources of false-negative results. 

The variation in results from study to study likely can be explained by variations in strains of LAB used, experimental design, age of the animal, type of challenge given to the animal, and the timing of sample collection. Also likely is that some strains of LAB are beneficial and can inhibit food-borne pathogens in poultry when administered correctly. 

Analyte Casualties (number) Time of sample collection Approximate concentration Remarks... 

One of the most critical steps in the analysis of procyanidins is their extraction. Preservation procedures and storage conditions of the crude samples as well as procedures and conditions during homogenization and extraction have a tremendous impact on the amount and composition of the extractable procyanidins. In view of a good reproducibility a complete standardization of all procedures and experimental conditions from the time of sample collection to the storage of the final extract must be emphasized. It is recommended to analyze fresh samples. If this is not possible, lyophilization is the drying procedure of choice. Samples should not be stored at all. If this can not be avoided care must be taken to exclude... 

Bruner, J. M., J. C. Scott-Moncrieff, and D. A. Williams. 1998. Effect of time of sample collection on thyroid stimulating hormone concentrations in euthyroid and hypothyroid dogs. Journal of the American Veterinary Association 212 1572-1575. 

The timing of sample collections is particularly critical for hormone measurements when effects on the female reproductive system are studied in smaller laboratory animals, given the shorter estrous cycles and pusatile/episodic changes of... 

Some significant pitfalls are associated with the measurement of cholinesterase, and these include the timings of sample collection and analysis. The time between blood and tissue sampling and assay should be minimized to prevent further inhibition... 

Short half-lives enable identification by decay measurement. They also require precise records of the time of sample collection, separation from the longer-lived parent, and the beginning and end of counting to calculate ingrowth and decay. Decay correction for reporting the activity at the time of collection is needed for all radionuclides, but is significant under usual sample analysis scheduling only for radionuclides with short and intermediate half-lives Sr is an example of the latter. 

Multiple patient factors may impact biomarker expression. For example, hydration status, medication, diet, tobacco use, exercise, concomitant diseases, or comorbidities may confound interpretation of biomarker values. For tissue biopsies, anesthetic agents and tissue ischania should be considered. Capturing this type of information at the time of sample collections may aid in identification of patient-related confounding factors that inflnence biomarker valnes and interpretation. 

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