Sample transport

Sample Transport Transport time, the time elapsed between sample withdrawal from the process and its introduction into the analyzer, shoiild be minimized, particiilarly if the analyzer is an automatic analyzer-controller. Any sample-transport time in the analyzer-controller loop must be treated as equivalent to process dead time in determining conventional feedback controller settings or in evaluating controller performance. Reduction in transport time usually means transporting the sample in the vapor state. 

Air-dilute with necessary blowers, flow measurement, and control systems Use isokinetic sampling, refrigerated sample transport, and careful handling to minimize physical or chemical changes... 

Sample transportation logistics Freezer storage sample processing j capabilities... 

Audits of each phase of the study should include personnel training, preparation of collection forms, application calibration, each sample collection procedure, sample transport, each type of chemical analysis, data recording, data entry, data verification and data storage. Data collection in the field is often tedious if automated logging devices are not in place. To ensure data integrity, the paper and ink used for field studies should be waterproof. Each data collection form should contain appropriate locations for information detailing the time and location of sample collection, sample transport and sample analysis. Data collection forms should be stored in an orderly fashion in a secure location immediately upon return of field teams from the field at the end of each day. It is also important for data quality for studies to collect necessary field data seven days per week when required. In our experience, poor study quality is likely when field sample and data collection do not proceed on weekends. 

Each data point must be transferred from data sheets into spreadsheets or databases. Verification of each datum should be performed by an individual who did not enter the data being verified. Audits of each phase of the study should be performed (i.e. preparation of collection forms, application calibration, each type of sample collection, sample transport, each type of chemical analysis, data recording, data entry, data verification and data storage). 

Field recovery samples are an important part of the quality control in DFR studies. Field fortifications allow the experimental data to be corrected for losses at all phases of the study from collection through sample transport and storage. Fresh laboratory fortifications monitor losses due to the analytical phase. This section details how the field recovery process was handled in the oxamyl tomato DFR study. 

Approximately 100% sample transport efficiency from GC to plasma... 

In 1976, Radiometer61 presented for the first time a microprocessor-controlled titration system. Since then, the microprocessor has been used preferentially and as a fully integrated part (in line) in electroanalytical instruments as a replacement for the on-line microcomputer used before. Bos62 gave a comprehensive description of the set-up and newer developments with microprocessors in relation to microcomputers and indicated what they can do in laboratory automation. Many manufacturers are now offering versatile microprocessor-controlled titrators such as the Mettler DL 40 and DL 40 RC MemoTitrators, the Metrohm E 636 Titroprocessor and the Radiometer MTS 800 multi-titration system. Since Mettler were the first to introduce microprocessor-controlled titrators with their Model DK 25, which could be extended to a fully automated series analysis via the ST 80/ST 801 sample transport and lift together with the CT 21/CT211 identification system, we shall pay most attention to the new Mettler MemoTitrators, followed by additional remarks on the Metrohm and Radiometer apparatus. 

Although the DL 40 was capable of performing Karl Fischer water titrations and Mettler developed a separate microprocessor-controlled push-button operated DL 18 KF titrator, they also introduced as an all-purpose apparatus the improved DL 40 RC (see Fig. 5.11) with a dual titration head and with a modified software program to handle the new two-component titrants for Karl Fischer titration (see pp. 204-205). The instrument can also be expanded into an automatic series titrator by connecting the RT 40 sample transport for 16 samples and storage of 50 sample weights from a connected balance this series routine can be interrupted at any time after completion of the titration in progress. 

In each of these plants, the characterization of the dust explosion potential was carried out by sampling transport ducts for explosive dust concentrations during an actual plant operation. The critical measurements taken were the quantification of explosive dust concentrations and level of electric energy generated from the electrostatic charge accumulations found in the duct. 

This Second Edition continues the basic approach of the first with the addition of four chapters. Chapter 1 is an outline of the development of soil chemistry with specific reference to the development of instruments that have been essential to the present understanding of soil chemistry. Chapter 7 is a new chapter dealing with soil sampling, both in the field and in the laboratory, soil water sampling, sample transport, and storage. Chapter 8 discusses direct, modified, and indirect methods of soil analysis. Chapter 15 covers the recent development of hyphenated instrumental methods and their application to soil analysis. 

SOIL AND SOIL SOLUTION SAMPLING, SAMPLE TRANSPORT, AND STORAGE... 

Field samphng, sample transport, and laboratory sampling are the three steps that must be carried out before sample analysis in the laboratory. Not getting a representative sample in the held, transport, and storage under nonideal conditions, and improper sampling in the laboratory can all cause dramatic changes in the results of an analytical procedure and thus alter its accuracy. The effect of these factors on variation in the data obtained is always larger than the inherent accuracy of the actual chemical procedure. 

Finally you have your laboratory costs. For even a modest site involving petroleum where you are miming 30-50 samples per month, the cost can exceed 300,000 per month. A good and fully equipped laboratory can exceed 500,000 in costs, and a single sample of soil by GC/MS can exceed 2500 when you include labor to collect the sample, transportation, chain of custody, and costs for analyses. If you have a radioactive program, the costs can double or triple. 

Many times swab samples have to be taken at a remote location where the equipment necessary for the analysis may not be available. Because the samples would be in transit for 24-48 h, an alternative to using test tubes for sample transport was investigated. Screw-cap scintillation vials either with a polyethylene insert or with an aluminum foil liner in the top of the cap were tested. Four polyester swabs were placed into each vial along with 10 mL of 1.00 pg/mL 50 50 ethanohwater solution of clarithromycin or 10 mL of 50 50 ethanohwater. The vials were capped and then shaken to wet the surface of the vials. Half the vials were refrigerated and the other half were left at room temperature on the... 

The physical nature of the process stream. Is it single-phase or two-phase Is it liquid, solid, vapor or slurry What is its temperature and pressure at the sampling point, and how far can these be allowed to change during sampling What is its viscosity at the appropriate sample measurement temperature The chemical nature of the process stream. Is it at equilibrium (a final product) or is it to be measured mid-reaction Is sample transport possible, or must the sample be measured in situ Is it corrosive, and what material and metallurgical constraints exist ... 

Alternatively, for nonequilibrium process streams, where a pumped reactor sample recycle line is available, in-line fiber-optic transmission cells or probes (Figures 5.26 and 5.27) can be used to minimize sample transport. It is highly desirable that some form of pumped sample bypass loop is available for installation of the cell or probe, so that isolation and cleaning can take place periodically for background reference measurement. 

Sampling mode effects The goal was to be able to measure at-line, with no sample preparation at all, using a fiber-optic probe or a remote sampling head. However, the area sampled by the hber-optic probe is much smaller than for the sample transport module. It was found that the remote (probe) spectra were very similar to the static (sample transport) spectra, but the baselines were shifted significantly higher and the absorbance peaks consequently reduced in intensity as before, the characteristic peak positions were not affected. Calibration models developed using spectra obtained with the hber-optic probe performed equivalently to those developed with the sample transport module. 

The instrumentation developed employs units for (1) automation of the basic operations (2) sample transport (3) central control (4) the entry and weighing station and (5) the output for results and logistics. 

The sample-transport mechanism is the physical link between the units for the basic operations and it moves the sample cups to the entry ports. The sample identification system ensures that samples are available to the appropriate unit at the right time. The mechanism functions hke a railway system it receives a command to move a cup containing a standard volume of sample from one place to another and then waits for the next instruction, which may require transport of the next sample cup or of the same sample to a different module. 

Whereas the microprocessor controls an individual basic operation, the central computer, which has all the analytical procedures held in its memory, controls the particular analytical procedure required. At the appropriate time, the central computer transmits the relevant set of parameters to the corresponding units and provides the schedule for the sample-transport operation. All units are monitored to ensure proper functioning. If one of the units signals an error, a predetermined action, such as disposing of the sample, is taken. The basic results from the units are transferred to the central computer, the final results are calculated, and the report is passed to the output terminal. These results can also be transmitted to other data processing equipment for administrative or management purposes. The central control is, therefore, the leading element in a hierarchy of... 

A sample of specified weight is normally required in the procedure. An interactive form of weighing is used, in which the display or printing unit of the entry station indicates whether or not the sample has been accepted. Before analysis it is necessary to specify the code number of the analytical method that is to be used, and to store this in the memory of the central control. To indicate where samples are located, it is necessary to identify them before weighing. Optical readers are therefore mounted on the sample-transport mechanism to register each sample. The sample is identified by a unique code placed on the outside of the sample cup. 

The titration cycle, Hke most of the other functions, can be repeated at will. Back-titrations are therefore possible, as well as multiple titrations for multi-component analyses. At the end of the cycle, the sample is returned to the sample transport. All dispensing is from a multi-burette system with up to 20 dispensing assembhes, each with a total dehvery volume of 10 or 20 ml. 

To optimize the applicability of the electrothermal vaporization technique, the most critical requirement is the design of the sample transport mechanism. The sample must be fully vaporized without any decomposition, after desolvation and matrix degradation, and transferred into the plasma. Condensation on the vessel walls or tubing must be avoided and the flow must be slow enough for elements to be atomized efficiently in the plasma itself. A commercial electrothermal vaporizer should provide flexibility and allow the necessary sample pretreatment to introduce a clean sample into the plasma. Several commercial systems are now available, primarily for the newer technique of inductively coupled plasma mass spectroscopy. These are often extremely expensive, so home built or cheaper systems may initially seem attractive. However, the cost of any software and hardware interfacing to couple to the existing instrument should not be underestimated. 

The sample cycle is now ffnished and the sample transport steps to the next sample. The average sample cycle time is 3 minutes wath four measuring instruments. 

Fig. 7.21 Schematic diagram of automated pH conductivity instrument, showing the sample transport mechanism.

---