Measurement repeatability solution

Static measurements (stationary solution). After a coulometric pulse of specific magnitude, the resulting pH step is measured. Repeating the experiment with different pulses allows the construction of the titration curve. 

The molar absorptivities for the two betaines and the three sulfobetaines in aqueous solution are listed in Table I. Before being used for surface tension measurements, aqueous solution of surfactants were further purified by repeated passage (12) through minicolumns (SEP-PAK Cjs Cartridge, Waters Assoc., Milford Mass.) of octadecylsilanized silica gel. The concentration of surfactant in the effluent from these columns was determined by ultraviolet absorbance, using the molar absorptivities listed in Table I. 

C. butyricum was immobilized in polyacrylamide gel membrane and the immobilized whole cells were fixed on the anode. A linear relationship was obtained between the steady-state current and the BOD from 0 to 250 ppm. The steady-state current was reproducible within 7 % of relative error, when the standard solution (50 mg 1 glucose, 50 mg l glutamate) was measured repeatedly. The standard deviation was 2 ppm. 

In order to establish that the enhancement was due to the LSPR effect and not to variations in the dye emission when conjugated to the silica shell surface, a separate experiment was performed where the metal NP was replaced by a pure silica NP with the same radius. These NPs were synthesized using a microemulsion technique [18] and the dye was attached as in the case of the metal NPs. The enhancement measurement was repeated and the fluorescence from the dye - silica NP was almost identical to that measured in solution hence confirming the plasmonic nature of the enhancement. 

The interpretation of such rate measurements repeatedly encountered difficulties related to the structure of the organomagnesium species present in the solutions, in particular, when solvents, such as tertiary amines or when magnesium bromide, were added [86]. 

Almost all detection techniques can be coupled with flow analysis even the analytical balance [2] and the microscope [3] have been used as detectors. It is however a fact that spectrophotometry1 is the most common detection techniques used in flow analysis, as it usually requires extensive manual solution handling. Moreover, the flow-through cuvette is permanently located in the detector unit, thus maintaining the detection geometry. This leads to an improvement in the measurement repeatability compared with batch-wise analytical procedures, in which the cuvette is removed from the instrument between measurements. 

If the pH of other sample solutions is to be measured, repeat the procedure in the previous paragraph. If more than a couple minutes will elapse before the next measurement, immerse the electrodes in distilled water. At the end of the laboratory period, be sure that the function knob is on STANDBY, disconnect the line cord, rinse the electrodes thoroughly with distilled water, and replace the protective cap or vial containing fresh distilled water. 

The material from Problem 8.3 was dissolved in a solution of 0.2 M sodium chloride and the surface tension measurements repeated. The results are given in the following table ... 

All mixtures were prepared in duplicate fresh solutions were prepared and the measurements repeated if the resulting optical densities differed for more than three units in the third significant figure. Therefore, the optical densities had an accuracy of 0.6%. Readings on solutions containing DNA were made with reference to a blank containing the same concentration of DNA in buffer. 

First, the voltammetric response of a solution of unknown concentration is measured. This solution is then repeatedly spiked with a known concentration of the analyte and the voltammetric response recorded after each addition. From the intercept of a plot of the response versus the additional concentration of the solution, the initial solution concentration can be found. An example of such a plot is shown in Fig. 9.7, where the intercept (as indicated on the graph) shows that the initial analyte concentration was 3mM. 

Experimentally, a solution of known concentration of starting material A is prepared, and then as the reaction proceeds, the concentration of A and/or B is measured repeatedly. In this simple reaction, A continually decomposes without coreactants or catalysts. When the supply of A reaches half the original concentration, the rate should be half the initial rate. If the rate at any point in time is divided by [A] at that point, the quotient should be a constant k, sometimes called the rate constant or specific rate (Eq. 4.8). The constant k is expressed in reciprocal seconds, s , and is simply the rate of the reaction when [A] = 1, even though it may have been determined at much lower concentrations than 1 molar. 

With the exception of the certified standard ERM-AE 670, which can be directly used for spiking, isotopicaiiy labelled species must be characterised in terms of isotopic abundance and concentration before use. Isotopic abundance is usually determined using repeated GC-ICP-MS measurements of the isotopicaiiy labelled species solution after following the same derivatisation process as envisaged for the sample. Procedure blanks must be measured repeatedly in order to perform blank corrections, if necessary, on the spike material. Data evaluation is performed using integrated peak areas of all element isotopes. 

To prepare the solution we measure out exactly 0.1500 g of Cu into a small beaker. To dissolve the Cu we add a small portion of concentrated HNO3 and gently heat until it completely dissolves. The resulting solution is poured into a 1-L volumetric flask. The beaker is rinsed repeatedly with small portions of water, which are added to the volumetric flask. This process, which is called a quantitative transfer, ensures that the Cu is completely transferred to the volumetric flask. Finally, additional water is added to the volumetric flask s calibration mark. 

Precision is a measure of the spread of data about a central value and may be expressed as the range, the standard deviation, or the variance. Precision is commonly divided into two categories repeatability and reproducibility. Repeatability is the precision obtained when all measurements are made by the same analyst during a single period of laboratory work, using the same solutions and equipment. Reproducibility, on the other hand, is the precision obtained under any other set of conditions, including that between analysts, or between laboratory sessions for a single analyst. Since reproducibility includes additional sources of variability, the reproducibility of an analysis can be no better than its repeatability. 

If a sample solution is introduced into the center of the plasma, the constituent molecules are bombarded by the energetic atoms, ions, electrons, and even photons from the plasma itself. Under these vigorous conditions, sample molecules are both ionized and fragmented repeatedly until only their constituent elemental atoms or ions survive. The ions are drawn off into a mass analyzer for measurement of abundances and mJz values. Plasma torches provide a powerful method for introducing and ionizing a wide range of sample types into a mass spectrometer (inductively coupled plasma mass spectrometry, ICP/MS). 

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