Chemical blank

Blanks may be differentiated into instrumental blank (background and baseline, respectively) and chemical blank (analyte blank). 

Sample with spike wet ashed, clean-up by anion exchange chromatography Isotope dilution-MS (isotopic quantification) 5pg (10 pg) uranium (total chemical blank) No data Kelly etal. 1987... 

In practice, measured isotope ratios are reported as mean and standard error. For analyses with stable ion-beam intensities, the within-run statistical errors are typically similar to those predicted by counting statistics. Uncertainties in sample weight, spike weight, spike concentration, chemical blanks, and filament blanks are typically small compared to the analytical uncertainty, but are also included in the error propagation through Eq. (1). 

Pipet into tube 1 100 of water, into tube 2 100 of standard solution 1 (2000 hqIL Pb), into tube 3 100 nL of standard solution 2 (4000 /ig/L Pb), into tube 4 100 nL of standard solution 3 (6000 ug/L Pb). The standard solutions 1 - 3 are prepared by diluting the stock solution with 0.01 M HNO3. To make a chemical blank pipet 150 nL of water and 850fiL of 0.1% Triton X-100 into an Eppendorf centrifuge tube. 

Pipet 200 /whole blood into a 4 mL acid-washed polystyrene tube. To make a chemical blank 200 fiL of water are pipetted instead of blood. If the calibration is performed by the internal standard addition technique, it is important to pipet exactly 200 juL of blood. This may achieved by the "reverse pipetting technique". 

For all real chemical measurements, the chemical blank Is the actual limiting factor. To assess Its magnitude and variability. 

Kelly, W. R. Notes, S. A. "The Importance of Chemical Blanks and Chemical Yields in Accurate Chemical Analysis" Preprint (1987). 

Although acridinium esters can be used to determine hydrogen peroxide, they are more commonly used as labels for immunoassay or DNA probes. As no catalyst is required, acridinium ester chemiluminescence has a lower chemical blank than the oxidation of luminol and therefore has superior detection limits. A strongly alkaline solution (pH 12-13) is required, but under these conditions acridinium esters undergo reversible conversion to the non-chemiluminescent pseudobase form (Scheme 1), which slowly decomposes. As a consequence, acidic hydrogen peroxide is added to reconvert the pseudobase to the acridinium ester before the chemiluminescence reaction is initiated with a sodium hydroxide solution. 

No sample standard normalization was applied since T1 normalization appears to be efficient to correct for instrumental bias. A blank solution of 3% v/v HNO3 added to a-Q water (18 Mil) similar to that used to adjust the sample solutions was prepared. The blank solution was systematically measured between each sample after careful washing out of the instrument. No electronic baseline or half-mass baseline was measured. The blank subtraction involved measurement of a real blank solution. In fact, the measurement included both the electronic blank from the instrument and the chemical blank from the water used to dilute samples. 

Chemical blanking used for thin parts requiring penetration through thickness. 

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