Technique selection guidelines

The guiding principles for the selection or development of speciation procedures are similar to those recommended for other forms of chemical analysis. For example, the initial step should be careful definition of the problem, including listing of the analytical specifications (e.g. type of analysis, concentration range, potential sources of error). This step can be followed by selection of a suitable measurement procedure, nomination of a selective separation procedure (if required) and organisation of the total protocol. 

The unique aspects of speciation procedures arise from the additional specification that the procedure adopted should not disturb existing equilibrium conditions. The choice of procedure is further restricted by the fact that the total concentration of element present in a sample (e.g. Cu, Pb, Cd, Zn in water samples) is often near the detection limits of many standard analytical techniques, and modified or refined techniques are required to handle the even lower levels present in isolated sub-categories. In biological matrices, the concentrations of inorganic and organo-metallic compounds present can range from 10 3 to 10 12 mol dm 3, and at the lower levels even the determination of total element content can be greatly in error, if suitable correction is not made for interference effects which can arise from the nature of the sample. 

With solid samples (e.g. suspended particles, sediments and soils), determination of the species distribution pattern usually involves a series of selective chemical extraction steps, but it is now recognised that many experimental parameters can influence the amount extracted by the reagents, and there are many potential sources of error. For example, during an extraction step, metal ions released from one phase can resorb on other exposed surfaces and, where coatings are being removed in the process, the values obtained can be influenced by the order in which reagents are used. 

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In order to harmonize an odor measurement technique, national guidelines or recommendations from Germany, France, the Netherlands and the United Kingdom are compared with respect to selection and treatment of panelists. Different methods of mathematical treatment of threshold data are also presented. 

Intrusive measurement techniques such as a Pitot static tube and hot-wire anemometer [24-26], and nonintrusive techniques such as laser Doppler velocimeter and particle image velocimetry (PIV) have been used to study the flow field. Goh, Kusadomi, and Gollahalli [13-15] mapped the velocity field in the flame using a Pitot static tube with a pressure transducer (Barocel). Details of the techniques and selection guidelines are presented in books on experimental aspects of fluid mechanics. Interested readers are referred to Holman [27], Goldstein [28], and Miller [29], to name a few. 

Although safety talks are short, these types of talks should not become just a routine part of the workday. Thus, to be effective, they must cover current concerns or information, be relevant to the job, and have value to the workers. Plan safety talks carefully in order to effectively convey a specific message and a real accident prevention technique. Select topics applicable to the existing work environment plan the presentation and focus on one issue at a time. Use materials to reinforce the presentation and clarify the expected outcomes. Some guidelines to follow ... 

The chemical propjerties of the contaminants have to be considered when selecting separation techniques. Some of the liquids are absolutely immiscible in water, and if the process stream involves water and the contamination is liquid/liquid, then the separation technique can greatly reduce the volume of contaminated water. For example, if acetone is the contaminant of concern, a simple vap>or stripping technique can be effective in making a separation. In the case of refined oil, which has a solubility limit of approximately 50 ppm, one of the oil/water separation techniques could be effective. Some general guidelines to consider are ... 

The purpose of these 3 volumes is to present techniques of process design and to interpret the results into mechanical equipment details. There is no attempt to present theoretical developments of the design equations. The equations recommended have practically all been used in actual plant equipment design, and are considered to be the most reasonable available to the author, and still capable of being handled by both the inexperienced as well as the experienced engineer. A conscious effort has been made to offer guidelines to judgment, decisions and selections, and some of this will be found in the illustrative problems. 

Review Techniques The review techniques used at the various stages of a project should be selected based on the amount of process information and detail available. Figure 23-47 depicts some typical review techniques at the various stages of a capital project. A detailed description, including the type and amount of process information required, for each review technique can be found in Guidelines for Hazard Evaluation Procedures Second Edition with Worked Examples (CCPS, 1992). The process information required for the review should be defined and documented in the review guidelines. Up-to-date and accurate process information is essential to conducting a successful review. 

HIC is more challenging than some analytical chemistries. It requires more attention to environmental controls, to equipment maintenance, and to column qualification. The retention mechanism is both more complicated and less intuitive than other methods. And, there are fewer practical guidelines concerning how to exploit the technique to its full potential. Despite these limitations, the bottom line is that HIC provides selectivities that are not obtainable with any other analytical method. 

To provide guidelines for the selection of material and techniques to be used for the construction of equipment and supporting accessories used to manufacture the process water... 

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