Sequential sampling

Fairbrother A, Bennett RS, Bennett JK. 1989. Sequential sampling of plasma cholinesterase in mallards (Anasplatyrh5Uichos) as an indicator of exposure to cholinesterase inhibitors. Environ Toxicol Chem 8 117-122. 

Figure 3.5 Schematic representation of data processing in a 2D experiment (one zero-filling in and two zero-fillings in F ). (a) A(, FIDs composed of Afj quadrature data points, which are acquired with alternate (sequential) sampling, (b) On a real...

Some major concerns in sampling include required depth of sampling, whether or not sequential samples at different depths will be... 

Surface sampling should be augmented with 12-15 sequential samples taken down to 1.5 meters In order to determine If the pollutant has moved downward. These 12-15 additional samples should be located In the area of major contamination. 

Occupational exposure to carbamate insecticides may be monitored by measuring RBC-ACHE and/or PCHE. However, given the low cholinesterase inhibition levels and the short time duration of this effect, ACHE inhibition can generally be used as a biomarker of exposure only when exposure levels are high. Three sequential samples are recommended to establish an individual baseline before exposure. In exposed workers, blood sampling and analysis should be carried out soon after the end of exposure (WHO, 1986). 

Sampling Procedures for Inspection by Attributes - Part 5 System of Sequential Sampling Plans Indexed by Acceptance Quality Limit (AQL) for Lot-by-Lot Inspection , ISO 2859-5 2005, International Organization for Standardization (ISO), Geneva, Switzerland, 2005. 

If sequential sampling seems incongruent with the performance of rapid trackers, then what other information is available Several researchers have suggested... 

In routine spectrophotometers, photomultiplier tubes are replaced by photodiodes (Fig. 11.11), which have excellent sensitivity, linearity and dynamic range. The photoelectric threshold, in the order of 1 eV, allows detection up to wavelengths of 1.1 pm. In diode array systems, each rectangular rectangular diode (15 pm x 2.5 mm) is associated with a capacitor. The electronic circuit sequentially samples the charge of each capacitor. While a photomultiplier tube measures the instant intensity in watts, a diode measures the emitted energy in joules over a time interval. 

A set of sequential samples taken during the simple batch or pot distillation of a charge of low wines into brandy were analyzed for higher alcohols and fatty acid esters as shown in Table III. These represent the... 

Table III. Pot Distillation of Beverage Brandy—Composition of Sequential Samples...

When Vs is very large, the time required for sampling can be substantial. By using the sequential sampling procedure both the required sample volume and the time required to obtain samples may be reduced. 

Figure 3.19 Schematic drawing of the sampling device used for sequential sampling of reaction products at the outlets of the parallel micro channel reactor [51] (by courtesy of SCS).

Another IEF/CGE separation was carried out on a PC chip for protein analysis. First dimension in one horizontal channel was used to perform denaturing IEF and second dimension in an array of 10 channels was used for SDS-gel electrophoresis, as shown in Figure 6.46. Instead of sequentially sampling proteins eluted from IEF, they are electrokinetically transferred in a parallel fashion... 

Xu, Z.R., Fang, Z.L., Composite poly(dimethylsiloxane)/glass microfluidic system with an immobilized enzymatic particle-bed reactor and sequential sample injection for chemiluminescence determinations. Anal. Chim. Acta 2004, 507,129-135. 

Accelerated solvent extraction (ASE) is becoming more popular because of its rapidity. This however is offset by sequential sample processing. Samples are placed in a stainless steel vessel and subj ected to solvent at elevated pressure and temperature. The pH of the extraction can be modified to assist in extracting acidic or basic compounds. 

Carry out the same procedure for the other starch solutions buffered at different pHs. Use your time wisely all the solutions can be handled simultaneously if you are familiar with the procedure. Slightly stagger the sequential sample withdrawal so that there is enough time for sample preparation and handling. 

Tamers, M.A. and Scharpenseel, H.W. (1970) Sequential sampling of radiocarbon in groundwater. In Isotope Hydrology 1970, IAEA, Vienna, 241-257. 

Sometimes it is obvious that the two-component model is inadequate rain combined with glacial meltwater (Behrens et at, 1979), for example. For rain-on-snow events where snow cores are used to assess the new-water composition, a two-component model is also inadequate (Wallis et al., 1979). However, if the catchment is snow-covered, overland flow is minimal, the surface area of the stream is small, and several snowmelt lysimeters are used to catch sequential samples of new water derived from infiltration of both rain and melting snow, a two-component model may be sufficient. It is difficult to judge a priori when the isotopic difference between soil water and groundwater is sufficient to require a three-component model (Kennedy et al., 1986 DeWalle et al., 1988 Swistock et al., 1989 Hinton et al., 1994). 

The computing software program performs the peak finding and identification tasks and determines the concentration of each metal in the sample at the end of a standard addition cycle. Concentration values for each metal, sampling time, date, and sequential sample number are printed out. 

The absolute procedure requires an auxiliary channel in the upper subsystem, through which the acceptor solution is also passed, furnished with an auxiliary injection valve (AIV in Fig. 4.19) of the same characteristics as the main injection valve (MIV), which is used to inject the sample for analyte separation and monitoring. Two sequential sample... 

J.M. Onorato, J.D. Henion, P.M. Lefebvre, J.P. Kiplinger, SRM LC-MS determination of idoxifene and its pyrrolidinone metabolite in human plasma using robotic high-throughput, sequential sample injection. Anal. Chem., 73 (2001) 119. 

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. 

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