Manual sampling

In summary, the precision of sampling improves with the size of each of the increments collected and with the number of increments included in a gross sample and manual sampling involves the principle of ideal sampling insofar as every particle in the entire mass to be sampled has an equal opportunity to be included in the sample. 

One particular method of sampling (ASTM D-6883) that relates to the standard practice for manual sampling of stationary coal from railroad cars, 

The practices described by the method provide instructions for sampling coal from beneath the exposed surface of the coal at a depth (approximately 24 in., 61 cm) where drying and oxidation have not occurred. The purpose is to avoid collecting increments that are significantly different from the majority of the lot of coal being sampled due to environmental effects. However, samples of this type do not satisfy the minimum requirements for probability sampling and, as such, cannot be used to draw statistical inferences such as precision, standard error, or bias. Furthermore, this method is intended for use only when sampling by more reliable methods that provide a probability sample is not possible. 

Systematic spacing of increments collected from a stopped belt is accepted universally as the reference method of sampling that is intrinsically bias-free. Stationary sampling, that is, sampling coal at rest in piles, or in transit in trucks, railcars, barges, and ships, suffers decreased reliability to an indeterminate degree. 

Where it is not possible to move a pile, there is no choice but to sample it as is, and the sampling regime usually involves incremental spacing of samples over the entire surface. The reliability of the data is still in doubt. However, without any attempt at incremental spacing of the sample locations, any sample taken directly from an unmoved storage pile is a grab sample that suffers from the errors that are inherent in the structure of the pile as well as in the method by which the sample is obtained. 

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Although mechanical sampling methods are to be the focus of attention, manual sampling methods are also employed for practical sample collecdion in commerce. Techniques of mechanical sampling should be emulated as closely as possible for best results with sampling by manual procedures. 

Notwithstanding the possibility of such automation, many successful operations depend almost entirely on manual sampling. Density determinations of the pulp on the media-return line and on each of the drainage screens are made at scheduled intervals, and the operator adjusts the media flow as needed. 

Manual sampling/ analysis is part of control scheme resulting in a large lag time in determining when to proceed and what to do (heat/cool, etc.). 

Ensure that safety is not compromised by using manual sampling/analysis as part of the control scheme, e.g., increasing hold times... 

Sampling needs vary with the batch being run. Use of same equipment/procedure may lead to operator exposure. Frequency of manual sampling is much higher than in continuous plants. 

Manual sampling should be carried out by grounded personnel, preferably using grounded metal equipment such as a metal sample thief bonded to the tank via metal cord. A satisfactory alternative is to place one or more glass sample bottles in a grounded metal cage (5-S.4.2). 

On-line coupled LC-GC methods have been developed in food analysis for several reasons, i.e. lower detection limits can be reached, the clean-up is more efficient, and large numbers of samples can be analysed with a minimum of manual sample preparation in shorter times. 

A multidimensional system using capillary SEC-GC-MS was used for the rapid identification of various polymer additives, including antioxidants, plasticizers, lubricants, flame retardants, waxes and UV stabilizers (12). This technique could be used for additives having broad functionalities and wide volatility ranges. The determination of the additives in polymers was carried out without performing any extensive manual sample pretreatment. In the first step, microcolumn SEC excludes the polymer matrix from the smaller-molecular-size additives. There is a minimal introduction of the polymer into the capillary GC column. Optimization of the pore sizes of the SEC packings was used to enhance the resolution between the polymer and its additives, and smaller pore sizes could be used to exclude more of the polymer... 

Test pits permit visual examination of the soil in place. Such pits also allow manual sampling of undisturbed soil samples. These samples can be taken from the side walls of the pit. 

Figure 2. Schematic representation of the reactor system computer-controlled pumps (PI, P2) pump controllers (fc) reactor (CSTR) reception vessel valves (S1-S4) monomer and initiator storage vessels (Tl, T2). (a) Digital input from GPC injection valve (b) analogue output from GPC (c, d) digital outputs to recorder chart drive and event marker (e, f) analogue outputs for pump set-point adjustment (g,h) reactor feeds (i) reactor output (j-m) digital outputs to reception system valves (n) manual sampling of products by GPC,...

In the last several years, on-line extraction systems have become a popular way to deal with the analysis of large numbers of water samples. Vacuum manifolds and computerized SPE stations were all considered to be off-line systems, i.e., the tubes had to be placed in the system rack and the sample eluate collected in a test-tube or other appropriate vessel. Then, the eluted sample had to be collected and the extract concentrated and eventually transferred to an autosampler vial for instrumental analyses. Robotics systems were designed to aid in these steps of sample preparation, but some manual sample manipulation was still required. Operation and programming of the robotic system could be cumbersome and time consuming when changing methods. 

The advantages of automation of extraction under reflux versus manual sample preparation are well illustrated for HDPE/(Irganox 1010, Irgafos 168) (Table 3.7) [118]. No spikes were observed in the former case, as opposed to the latter. Boiling under reflux is considered by some [4] as the best all round conventional extraction method. 

The above so-called automated titrations still require manual sample introduction directly into the measuring cell60 in order to avoid this in series analysis, a few manufacturers added automatic samplers, which in laboratory practice require only the previous introduction of samples into a series of cups... 

Achiral-chiral multidimensional chromatography remains one of the best ways to separate chiral analytes from interfering matrix components or other compounds. The flexibility offered by different operation modes, stationary and mobile phases, and configurations allows analysis methods to be tailored to the analytical problem. By offering possible configurations for both online sample cleanup and concentration, achiral/chiral LC/LC reduces manual sample preparation. The ability to be coupled to... 

The repeatability of gas sample separation is presented in Fig. 6.12. The separation peaks of the mixed gaseous analytes match those for each individual analyte quite well, irrespective of the analyte concentration, which correlates to the peak height (Fig. 6.12a, b). Although manual sample injection may introduce a certain degree of variation in retention time measurement, using a gas marker can significantly improve such measurement, as demonstrated in Fig. 6.12c, in which decane is used as a marker. 

Filters are used on almost all analyses many types or different materials are used in automated and manual sampling. Validation of the pre-wetting or discard volume is critical for both the sample and standard solutions. Plugging of filters is a common problem, especially with automated devices and with Apparatus 4. 

Manual sampling techniques can introduce error by virtue of variations in strength and size of the human hand, from analyst to analyst. As a result, the pulling velocity through the filter may vary considerably. Too rapid a movement of liquid through the filter can compromise the filtration process itself. 

Dissolution methodologies and apparatus described in the USP can generally be used either with the manual sampling or with automated procedures. ... 

SCIEX API 365 equipped with a TurboIonSpray interface operated in positive ion mode. The calibration range 0.124-497 ng/mL was readily validated with a negligible carry-over effect from this system. The method offered a total cycle time of 8 min and completely eliminated the manual sample preparation. ... 

A comparison of automated pipetting with manual pipetting, by Weltz [16]. demonstrates a difference of approximately one order of magnitude 0.4% RSD for automatic sample introduction versus 3.2% RSD for manual sample introduction. To achieve optimum results for trace elements in biological materials, the use of dedicated automated samplers is recommended. The Hquid-handhng capabihties of a pipetter/diluter workstation have been evaluated at Ortho Pharmaceutical (Haller et al. [17]). Four different volumes of each of three solvents were dispensed 20 times. Actual volumes... 

Weekly monitoring of the interstitial space of a double-walled tank may be practiced using pressure monitoring, vacuum monitoring, electronic monitoring, or manual sampling. 

Materials. Gelman 37 mm, type A/E glass fiber, GN-4 0.8 metricel, and DM-800 0.8 membrane filters were used in this study. Spectral quality, pyrolytic coated, graphite furnaces and rods were used in the study. The furnace capacity was 5 yL of solution. Manual sample injections were made with a 5 yL Eppen-dorf pipet 4700 using disposable tips. 

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