Multiple dilution

Gas Stream Mixing A t Two or more gas streams flowing at a known rate are mixed to give the desired concentration. Multiple dilution stages may be used to give lower concentrat ions. 

The accuracy of multiple dilutions fades as more and more dilutions are made because of the added errors of additional flow measurements. In the double dilution above, four flow measurements are needed, two for each dilution. Fortunately, however, multiple dilutions are used to produce low concentrations where perhaps analysis accuracy of 10% would be acceptable. 

Requiring low-sample volume micro-scale tests for its cost-effective application, the PEEP index has thus far employed bioassays with bacteria, algae and microinvertebrates. While well-standardized toxicity tests using freshwater fish existed at the time of the PEEP s conception in the early 1990 s (e.g., the Environment Canada fingerling rainbow trout 96-h lethality test to assess industrial wastewaters), they were excluded because of their large sample volume needs (e.g., close to 400 L of effluent sample required to undertake a multiple dilution 96-h LC50 bioassay in the case of the trout test). In addition to effluent sample volume, the cost of carrying out salmonid fish acute lethality bioassays for the 50 priority industrial effluents identified under SLAP I (the first 1988-93 Saint-Lawrence River Action Plan) was prohibitive. 

Oily matrices (sludge, fuel-contaminated soil) may undergo multiple dilutions during analysis. The interferences from the oil constituents and the analytical uncertainty induced by dilutions may reduce the data obtained with definitive analytical methods to screening data. 

Because each vial with the soil/water slurry can be analyzed only once, sample dilutions are not possible. To overcome this problem, we should always have a sample aliquot preserved in methanol. Methanol extracts are diluted in water for analysis, and because the laboratory needs very small amounts (5-300 microliters [pi]) of methanol extract, multiple dilutions and reanalysis of sample preserved in methanol can be easily performed. 

Sometimes a multiple dilution method may be used to prepare a final mixture with acceptable uncertainty in typical low concentration of minor components. 

Calibration standards are prepared by single or multiple dilutions of the stock metal solutions. A reagent blank and at least three calibration standards should be prepared in graduated amounts in the appropriate range of the linear part of the curve. The calibration standards must contain the same acid concentration as in the samples after processing. 

Figure 1.5. Examples of single and multiple dilution of a sample. (Reproduced from Ref. 3 with permission from LC-GC North America.)...

FIGURE 3.9 Evaluation of minimal required dilution. Individual and pooled normal human serum samples are analyzed at multiple dilutions. The matrix dilution at which spike recovery falls within an acceptable range (80 120%) in at least 80% of the samples indicates the MRD. 

FIGURE 3.13 Hook effect revealed by dilutional linearity experiment, (a) The analyte when assayed neat resulted in a low measured concentration. When reassayed at multiple dilutions, the measured concentration for several dilutions was greater than the assay ULOQ. (b) The results, when corrected for the dilution factor, showed dilutional linearity at dilutions greater than 400 fold, indicating the presence of a HDHE. 

Determine recovery from whole blood and other body fluids at multiple dilutions... 

Making a dilution series is highly important in immunoassay. In most cases, multiple dilution ranges can be made using the multichannel pipets. A dilution series is given next. 

Multiple tube methods are very sensitive to small numbers of micro-organisms due to the powerful amplification of these techniques. However, the methods are not very accurate statistically, and have considerable errors associated with them. In addition, the multiple dilutions needed are very demanding on technician time, sterile glassware and media. Tube methods may be run in conjunction with plate counts. 

We routinely silanate glass microscope slides that have small wells 3-5 mm in diameter that have been formed by a paint coating. These are available commercially (not silanated) from Roboz (Rockville, MD). Alternatively, cut holes in strips of vinyl electrical insulation tape using a hole punch and apply this tape to microscope slides that have previously been silanated. This tape forms small wells that contain the drops of immunoreagents that are subsequently applied. The use of small wells conserves expensive immunoreagents and allows multiple dilutions of an antibody to be tested on different wells of a single slide. Sections of the tissues are cut and deposited onto the slides. The sections are allowed to air dry at room temperature for 20-30 min prior to commencement of immunolabeling... 

Jeon et al. [6] reported a microcharmel network method for generating defined concentration gradients in a microfluidic device. Solutions of different concentrations were introduced into the microfluidic device by syringe pumps at separate inlets and repeatedly mixed and split through the microchannel network, producing multiple diluted streams with predictable concentrations. These streams flowed side by side in a common chaimel and generated a soluble or... 

Two classic techniques for separation and enumeration of microbial populations utilize pour plates or spread plates. Both suffer from logistical and interpretational difficulties. It is generally necessary to plate multiple dilutions (in duplicate) of the same sample in order to arrive at plates that are countable and statistically valid. In the case of pour plates, embedded colonies may be difficult to recover and transfer. Further, where either method is used for enumeration purposes, it is assumed that each developed colony arose from a single cell. As previously noted, in the case of yeasts this may not be a completely valid assumption. 

Since the microorganisms respond only to free biotin, bound forms must be treated prior to analysis to release biotin in its free form. Following extraction of biotin from the sample by high-temperature acidic and/or ambient enzymatic strategies, the methodology relies on the incubation of the food extract at multiple dilution levels with the microbiological culture in a biotin-deficient... 

Conducted crystallization in an oil bath containing multiple dilute polymer solutions. The bath is slowly cooled to < 0°C. 

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