Sampling time proportional

The type of water sample to be taken at each site is part of the strategy for the monitoring programme. For most water bodies, spot samples are likely to be appropriate. In specific situations, where pollutant concentrations are heavily influenced by flow conditions and temporal variation, and if pollution load assessments are to be performed. Other more representative types of sample may be beneflcial. Flow-proportional or time-proportional samples may be better in such cases. A single depth sample might not be adequate to reflect the situation in stratifled water bodies such as lakes, estuaries and coastal areas. Hence, waters samples should be taken at several depths at such locations. For example, multiparameter probes (e.g. CTD probes) can be employed to detect stratifications. 

To estimate the pollutant load that is transferred across Member State boundaries and into the marine environment, an enhanced sampling frequency is necessary. In case of spot sampling for substances, which show a wide range of concentrations, biweekly sampling, e.g., 26 samples a year, is advisable. Flow-proportional or time-proportional sampling may be beneficial in such cases. 

As a basic rule, flow-proportional sampling is recommended flow-proportional composite samples can be produced from the individual samples taken, where necessary, with automatic sampling devices. In the case of time-proportional sampling, no account is taken of the quantity of water. 

Time Proportional Sampling—An automatic sampler should preferably operate in proportion to flow. However, sampling in a time proportional mode is acceptable if the flow rate variation is less than 10 % of the average rate over the entire parcel. 

The contribution to the plate height from molecular diffusion in the mobile phase arises from the natural tendency of the solute band to diffuse away from the zone center as it moves through the column [59,60,63,64]. Its value is proportional to the diffusion coefficient and the. time the sample spends in the column. Its contribution to the total plate height is given by... 

However at long times a sample of prepared complex molecules will deplete according to the law, N(t) = N(0)e /T, where the lifetime r is related to the resonance width according to r = h/F. Furthermore, the decay flux into each outgoing channel is locked in fixed proportion at all... 

This chapter focuses on gas-liquid chromatography, in which compounds in a sample are separated based on vapor pressures and differences in affinity for the stationary phase (a high boiling point liquid) versus the gaseous mobile phase. The time between sample injection and detection of the individual compound eluting from the column is called the retention time. Compounds that have limited solubility in the stationary phase will exit the column quickly as a large proportion will remain in the mobile phase. Compounds with polarity similar to that of the stationary phase will have longer retention times and potentially broader peaks, due to increased interaction with the stationary phase. 

Database For glacier streams, Versegeres and Calancasca mean load calculated as mean discharge times mean concentration. For the other rivers, loads represent means and medians, respectively, of biweekly water discharge proportional samples over the whole measuring period... 

The adjusted retention time of a probe molecule, such as n-octane, can be used as a means of determining the surface area of certain polymers. Different weight samples are placed in a chromatographic column onto which the probe is injected. A plot of adjusted elution time versus sample weight is fairly linear with a slope proportional to the specific surface area. 

The controller has tuning parameters related to proportional, integral, derivative, lag, dead time, and sampling functions. A negative feedback loop will oscillate if the controller gain is too high but if it is too low, control will be ineffective. The controller parameters must be properly related to the process parameters to ensure closed-loop stability while still providing effective control. This relationship is accomplished, first,... 

Automatic liquid samplers are also available to collect intermittent samples from pressurized pipelines and deposit them in sample containers. The sample can be collected on a time-proportional or on a flow-proportional basis. The sampler can withdraw a predetermined volume of sample every time the actuator piston is stroked. In the time-proportional mode, the sampling frequency is constant, whereas in the flow-proportional mode, it is a function of the flow. 

Count the alpha particles in each tracer sample for a time period sufficient to accumulate at least 1000 counts. An initial estimate of the sample counting period is based on the activity of the tracer and the known counting efficiency. Count all disks for the same period of time. The samples may be counted more than once. Count the spectral analysis background for approximately 200,000 s and the proportional-counter alpha-particle background at least 30,000 s. Record data in Data Table 6.2. 

We will see that in 2D NMR, the sampling in the second dimension can also be done either way, except that this choice is up to the user and is not hard wired. The alternate ( Bruker-like ) sampling method is called TPPI (time proportional phase incrementation), and the simultaneous ( Varian-like ) method is called States or States-Haberkorn (after the originators of the technique). The consequences for processing and interpretation of the data are the same in the second dimension of 2D spectra as they are in ID NMR. 

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