Blank value

The dispersion of blank values can give indications of random and systematic deviations, e.g. in order to 

For this reason blank values should be analyzed both before and after a series of analyses. They can be experimentally determined from separately conducted multiple analyses. The mean blank value is subtracted from the information value yi and this corrected information value gives the concentration. 

Another possibility for determining the blank value consists in extrapolating the calibration curve. There the blank value is already recorded by the ordinate intercept ao (UBA research report 102031U, 1982, Verlag Chemie, Weinheim, FRG). 

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Atomic absorption spectroscopy of VPD solutions (VPD-AAS) and instrumental neutron activation analysis (INAA) offer similar detection limits for metallic impurities with silicon substrates. The main advantage of TXRF, compared to VPD-AAS, is its multielement capability AAS is a sequential technique that requires a specific lamp to detect each element. Furthermore, the problem of blank values is of little importance with TXRF because no handling of the analytical solution is involved. On the other hand, adequately sensitive detection of sodium is possible only by using VPD-AAS. INAA is basically a bulk analysis technique, while TXRF is sensitive only to the surface. In addition, TXRF is fast, with an typical analysis time of 1000 s turn-around times for INAA are on the order of weeks. Gallium arsenide surfaces can be analyzed neither by AAS nor by INAA. 

Blind-probe, /. blank test, -schlauch, m. flexible tube closed at one end. -strom, m. (Elec.) wattless current, -versuch, m. blank test, -wert, m. blank value, reagent value, -wlderstand, m. (Elec.) reactance. 

Barium Hand blank Values from 97 Persons in 30 Different Occupations. N... 

Degree of Overlap of Firing Values with Hand blank Values (from Ref 8)... 

Figure 1 Influence of the specific mechanical energy on the water-solubility (corrected from the blank values) of some raw materials...

It is further important to note that if only solid samples are taken, the calibration curve passes through the origin as is obvious in Figure 4.4. An intercept usually caused by blank values from reagents and digestion vessels in wet analysis can be excluded except in the case of matrix modification. 

Specificity is defined in Directive 96/46/EC as the ability of a method to distinguish between the analyte being measured and other substances. According to SANCO/825/00, blank values must be reported using representative matrices. They... 

Blank values must be reported they should not be higher than 30% of the LOQ. Confirmatory method/technique must be described if appropriate... 

Table 5 Example for an adequate presentation of blank values, recovery and reproducibility for...

Significant background interferences (high blank values)... 

Lower blank values because of reduced reagent quantities... 

The addition of fluxes increases the risk of raising the blank value, owing to the amount of flux required for a... 

Table I. Typical Blank Values of Various Fruits and Vegetables...

This approximation is probably adequate during method validation as it provides an indication of the concentration below which detection becomes problematic. It indicates that a signal more than 3 bi above the sample blank value could have arisen just from the blank in fewer than 5% of the measurements... 

For example, The concentration is derived from a 6 point calibration curve by reading off the concentration, corresponding to the sample absorbance, corrected for the blank value, and multiplying it by the concentration factor . 

A data processor plots the chromatogram, automatically integrates the peak areas and prints retention times, percent areas, baseline drift and attenuation for each run. It also computes blank values, constant factors and relative average elemental contents. 

In their proposed method, contamination only from the ammoniacal glutathione solution is expected. However, any inorganic mercury in this solution will be adsorbed on the glass container walls with a half-life about 2d, i.e. the blank value becomes zero if the solution is left to stand for more than a week. This method for mercury in sediments does not distinguish between the different forms of organomercury. Results are calculated as methylmercury. 

Results Average the counts per minute in vials 3 and 4. This is the blank value. Now, subtract the blank from all other counts per minute to obtain the actual counts per minute and average the counts per minute for vials 1 to 2 to find the total count per minute. The percent bound may be calculated using the following expression ... 

Copy the following table into your notebook. Then use the given information to predict the blank values. Do not write in this textbook. 

There are a few requirements for the application of the standard addition method. The analytical results have to be corrected for blank. Otherwise we would add the blank value to our sample content. Since we are using linear regression we need a linear relationship between signal and concentration. As stated above the homogeneity of variances is also a prerequisite for linear regression. We want to divide our sample into several sub-samples and spike them with known amounts of analyte. This means that we need to divide the sample homogeneously and to precisely add the analyte. 

It is an indicative valne and should not normally be nsed for decision-making pnrposes. It shonld be established nsing an appropriate measurement standard or sample and should not be determined by extrapolation. The LoQ is calculated as the analyte concentration corresponding to the sample blank value plus 10 standard deviations of the blank measurement. If measurements are made under repeatability conditions, a measure of the repeatability precision at this concentration is also obtained. 

The Blank Value Chart is also very important. This is a special form of a Shewhart chart where the direct measurements (e.g. in Volts) from the analyses of blank samples are used. From this chart information can be received about contamination of reagents e g. from the enviromnent and the state of the analytical system. 

Different Control Charts Blank Value Chart... 

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