Data column precision

Isotope data (6 in %o relative to the PDB belemnite standard) for C6-C14 n-alkanes are from whole oil analysis using PONA methylsilicone column. Precision of the measurement 0.2%o for each compound. Data for C15-C19 n-aUcanes and pristane and phytane are from DB-1 analysis of saturated hydrocarbon fractions using DB-1 column. 

Katz et fl/.[l] searched the literature for data that could be used to identify the pertinent dispersion equation for a packed column in liquid chromatography. As a result of the search, no data was found that had been measured with the necessary accuracy and precision and under the sufficiently diverse solute/mobile phase conditions required to meet the second criteria given above. It became obvious that a... 

The results obtained were probably as accurate and precise as any available and, consequently, were unique at the time of publication and probably unique even today. Data were reported for different columns, different mobile phases, packings of different particle size and for different solutes. Consequently, such data can be used in many ways to evaluate existing equations and also any developed in the future. For this reason, the full data are reproduced in Tables 1 and 2 in Appendix 1. It should be noted that in the curve fitting procedure, the true linear velocity calculated using the retention time of the totally excluded solute was employed. An example of an HETP curve obtained for benzyl acetate using 4.86%v/v ethyl acetate in hexane as the mobile phase and fitted to the Van Deemter equation is shown in Figure 1. 

To confirm the pertinence of a particular dispersion equation, it is necessary to use extremely precise and accurate data. Such data can only be obtained from carefully designed apparatus that provides minimum extra-column dispersion. In addition, it is necessary to employ columns that have intrinsically large peak volumes so that any residual extra-column dispersion that will contribute to the overall variance is not significant. Such conditions were employed by Katz et al. (E. D. Katz, K. L. Ogan and R. P. W. Scott, J. Chromatogr., 270(1983)51) to determine a large quantity of column dispersion data that overall had an accuracy of better than 3%. The data they obtained are as follows and can be used confidently to evaluate other dispersion equations should they appear in the literature. 

It is seen that in order to measure retention volumes with a precision of 0.1%, the temperature control must be +/- 0.04°C. This level of temperature control on a thermostat bath is not difficult to achieve but it is extremely difficult, if not impossible, to return to a specific temperature to within +/- 0.04°C after prior change. To achieve a precision of retention volume measurement of 1%, the temperature control must be +/- 0.4°C. This is far more practical as most column oven temperature can be set to a given temperature to within +/-0.25°C. Although the data was obtained for three specific solutes, the results can be taken as reasonably representative for all solutes and phase systems. In most practical analyses, the precision limits of retention volume measurement will be about 1% but this will not include the reproducibility of the flow rate given by the pump. As... 

One can also state that the log double-centered biplot shows interactions between the rows and columns of the table. In the context of analysis of variance (ANOVA), interaction is the variance that remains in the data after removal of the main effects produced by the rows and columns of the table [12], This is precisely the effect of double-centering (eq. (31.49)). 

In this analysis, weight coefficients for rows and for columns have been defined as constants. They could have been made proportional to the marginal sums of Table 32.10, but this would weight down the influence of the earlier years, which we wished to avoid in this application. As with CFA, this analysis yields three latent vectors which contribute respectively 89, 10 and 1% to the interaction in the data. The numerical results of this analysis are very similar to those in Table 32.11 and, therefore, are not reproduced here. The only notable discrepancies are in the precision of the representation of the early years up to 1972, which is less than in the previous application, and in the precision of the representation of the category of women chemists which is better than in the previous analysis by CFA (0.960 vs 0.770). 

The precise location of the feed point will affect the number of stages required for a specified separation and the subsequent operation of the column. As a general rule, the feed should enter the column at the point that gives the best match between the feed composition (vapour and liquid if two phases) and the vapour and liquid streams in the column. In practice, it is wise to provide two or three feed-point nozzles located round the predicted feed point to allow for uncertainties in the design calculations and data, and possible changes in the feed composition after start-up. 

Kublin and Kaniewska [52] used a gas chromatographic method for the determination of miconazole and other imidazole antimycotic substances. The conditions have been established for the quantitative determination of miconazole and the other drugs, which are present in pharmaceuticals such as ointments and creams. The column, packed with UCW-98 on Chromosorb WAW, and flame-ionization detector were used. The statistical data indicate satisfactory precision of the method, both in the determination of imidazole derivatives in substances and in preparation. 

A large number of separations can be performed by HPLC by simply injecting various samples and appropriate final data reduction, although the column and/or solvent may require a change for each new application. Based on these comments, it should be obvious that HPLC is considerably more convenient and less operator-dependent than classical LC. The greater reproducibility and continuous quantitative detection in HPLC allows more reliable qualitative analysis as well as more precise and accurate quantitative analysis than classical LC. 

Capillary GC/ECD, dual column capillary GC/ECD, and capillary GC/MS have been used for quantitation of mirex in milk with sensitivity in the low to sub-ppb range (Bush et al. 1983b Mes et al. 1986 Mussalo-Rauhamaa et al. 1993 Rahman et al. 1993 Rehman et al. 1993). Recovery data for milk are generally very good (>70%) (Mes et al. 1993 Mussalo-Rauhamaa et al. 1993 Rahman et al. 1993), but precision data were not reported. 

Mirex can be extracted from feces with hexane-acetonitrile and the extract cleaned up on alumina/Florisil columns, then analyzed using GC/ECD. Sensitivity, precision, and accuracy data for feces were not reported (Gibson et al. 1972). 

The traditional HPLC instrument is composed of two different parts the first part separates the components of the sample and the other part accomplishes the detection of the components separated. The part of the HPLC carrying out the separation contains a column, an injection device and the eluent delivery system (pump with filters, degasser and transfer tubing, eventually a mixer for gradient elution). One or more detectors, a signal output device coupled with appropriate software, are responsible for detection and primary data evaluation. Pumps deliver the eluent or the different components of the eluent into the column with a precise, constant and reproducible flow rate. 

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