Standard deviation required dilution

The experiment consists in the incubation of the labeled antigen (1) with increasing concentrations of MIP or NIP/CP, and (2) with the same set of concentrations but in the presence of a constant concentration of analyte sufficient to displace significantly the probe from the polymer [22]. Each point in the dilution curve should be determined at least by duplicate and preferably between five and ten replicates so that we can obtain not only the optimum polymer concentration for the assay but also an estimate of the standard deviation of the response at each point along the curves. The curve representing the difference (% bound label) of the bound label in the absence and in the presence of the analyte will render the optimum MIP concentration to be used in the assay. Using this approach we have optimized the amount of polymer required for the development of a fluoroimmuno-like assay for penicillin analysis [36],... 

As an alternative to the methodologies based on standard deviation, one can define the LOD (or LOQ) to be the lowest concentration that produces an analytical response that meets predefined quality requirements. For example, one might define the LOD as the lowest analyte concentration that produces a percent relative standard deviation (%RSD) of 10%. The LOD can be determined by performing replicate analyses of successively more dilute samples. The LOD could be estimated if one plots percent relative standard deviation vs. the analyte concentration (Fig. 7). 

Serious consideration and time must be given to whether the component of interest is in exceptionally high concentration which, in such cases, may have to be diluted to fit calibration standards or, if low, may require pre-concentration. In some cases it may be necessary to carry out a trial-and-error to ascertain the approximate concentration of metals in samples. The low value must at least be at quantitative limits (i.e. ten times the standard deviation of baseline noise, to be confident of results see Section 3.8.1.7). If it is lower than ten times standard deviation of the baseline the sample may have to be preconcentrated prior to analysis to a level that can be comfortably detected and is suitable for reproducible measurements. The following is a list of common methods of sample preparation techniques. Choosing the correct method is of primary importance and poses a challenge to most analysts, particularly for unknown samples ... 

In the analytical procedure, an accurately measured aliquot of the product is diluted Avith a diluent (normally the mobile phase) and the resulting sample solution is injected into the HPLC. Because the majority of injectable pharmaceuticals are clear solutions, typically a simple dilution step is all that is needed for sample preparation. However, if the parenteral product is an emulsion or a suspension, appropriate steps must be taken to dissolve the product to achieve a clear solution (ultrasonication, filtration, etc.). For the assay procedure, the sample concentration chosen should be such that the peak areas obtained from multiple injections from the same sample are reproducible with minimum variance (<2% relative standard deviation). Peak shape and retention time also play important roles in the precision of the assay. A tailing factor less than 1.5 and a capacity factor less than 10 for the active peak are generally required for a good analytical method. A reference standard solution having the same concentration and using the same diluent as the sample solution is prepared. 

The determination of MSR for titer precision requires dilution profile data of at least five high-positive mock samples, diluted past the screening cut point, from at least three independent runs by two or more analysts (if relevant). The mock positive samples are drug-naive samples from individual donors spiked with a high concentration of the ADA-positive control. The titer results of all these mock positive samples from different runs should be log transformed and analyzed to obtain the overall standard deviation. This estimate of overall SD is then used to determine the MSR of the titer results, where MSR = 10A[2 sqrt(2) SD], assuming that base 10 was used in the log transformation of the titer results. In addition to the practical usefulness of the MSR concept in this application, an attractive feature is that it applies to any range of titer results. This is because the variability in log scale tends to be quite similar across the entire range of titer results. 

Kubasik et al. (KIO) determined lead in whole blood using the carbon rod atomizer. Only a 3-fold dilution of the whole blood with Triton X-100 (50 ml/liter) was required, and results were comparable to those obtained by flame techniques. Addition of xylene to the carbon rod (M3) did not prevent soaking of the sample into the rod and so blood standards had to be used. Rosen and Trinidad (R8) described a method for the measurement of lead in capillary blood samples, developed in conjunction with a simple micro blood-collecting system. Heparinized, untreated blood (0.5 jal) was injected into the carbon rod, with 0.2-O.3 ftl of xylene on either side of the sample. The sample was subsequently dried, ashed, and atomized. The sensitivity was 0.5 ftg/100 ml per 1% absorption, and the standard deviation of over 450 blood samples analyzed in duplicate was 0.91 /xg/100 ml. Results agreed closely with those obtained using conventional flame methods carried out on simultaneously collected venous samples. 

Recently, LC/MS has made significant contributions in the analysis of sterols and steryl esters. Takatsu and Nishi (1993) have employed discharge-assisted LC/TS/MS for the determination of total serum cholesterol. The method incorporates stable isotope dilution using [3,4- C] cholesterol as an internal standard. [MM — H20] ions were monitored by the SIM method. Satisfactory agreement between the analytical result and the certified value of the National Institute of Standards and Technology standard reference material was obtained with a relative standard deviation of 0.6%. The method does not require sterol derivatization. Yang et al. (1992) used FAB/MS to identify cholesteryl sulphate m/z 465) as the [M — H] ion recovered from the appropriate TLC fraction. 

Jager etal. (1992) used a dilution unit in conjunction with laser diffraction measurement equipment. The combination could only determine, however, CSD by volume while the controller required absolute values of population density. For this purpose the CSD measurements were used along with mass flow meter. They were found to be very accurate when used to calculate higher moments of CSD. For the zeroth moment, however, the calculations resulted in standard deviations of up to 20 per cent. This was anticipated because small particles amounted for less then 1 per cent of volume distribution. Physical models for process dynamics were simplified by assuming isothermal operation and class II crystallizer behaviour. The latter implies a fast growing system in which solute concentration remains constant with time and approaches saturation concentration. An isothermal operation constraint enabled the simplification of mass and energy balances into a single constraint on product flowrate. 

The CLND is the most critical component in the platform. With our current experience, the most crucial factor is the stability at the sprayer exit. This may well be the source of the large deviations (up to 80%) observed for some of the examined compounds. The unpredictable nature of such operational malfunction strongly suggests the need for replicate determinations as the minimal requirement for reliable quantitative estimates. Other factors (injection error of the autosampler, dilution error in the preparation of solutions or standards) may account for only a limited fraction of the total measured variance and could be easily corrected for by the introduction of an appropriate internal standard. 

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