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What is the difference between an instrument detection limit and a method detection limit? What is the difference between robustness and intermediate precision?

Short Answer

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The analytical approach applied is said to be robust if it is capable of not being influenced by extremely minor changes in the operational parameters (having robustness). Ruggedness, on the other hand, is a type of precision that can be seen when an assay is carried out by different people using different tools on different days in the same laboratory.

Step by step solution

01

Definition of instrument detection limit and method detection limit

Instrument detection limit

In analytical chemistry, Instrument detection limit can be found by replicating the measurements of the sample.

Method detection limit

In analytical chemistry, Method detection limit can be found by analyzing every single sample.

02

The difference between an instrument detection limit and a method detection limit

The difference between them is that the method detection limit is attainable when we prepare at least 7 separate samples and analyze all of them. Contrary to this, the instrument detection limit is attainable when we perform replicate measurements of at least 7 aliquots coming from the same sample source. Moreover, the method detection limit is greater than the instrument detection limit.

Robustness

In analytical chemistry, robustness can be defined as the capacity of analytical process which can't be used affected by small changes.

Intermediate precision

In analytical chemistry, intermediate precision can be defined as the measure of precision under different kind of conditions. Such as same amount procedure, same measuring system, same location and same replicate measurements on the similar objects over an estimated period of time.

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Most popular questions from this chapter

What are the three parts of quality assurance? What questions are asked in each part and what actions are taken in each part?

Detection limit. In spectrophotometry, we measure the concentration of an analyte by its absorbance of light. A low-concentration sample was prepared and nine replicate measurements gave absorbances of 0.0047,0.0054,0.0062,0.0060,0.0046,0.0056,0.0052,0.0044, and 0.0058. Nine reagent blanks gave values of 0.0006,0.0012, 0.0022,0.0005,0.0016,0.0008,0.0017,0.0010, and 0.0011.

a) Find the absorbance detection limit with equation 5-3.

b) The calibration curve is a graph of absorbance versus concentration. Absorbance is a dimensionless quantity. The slope of the calibration curve is m=2.24x104M-1Find the concentration detection limit with Equation 5-5.

(c) Find the lower limit of quantitation with Equation 5-6.

Detection limit. A sensitive chromatographic method was developed to measure sub-part-per-billion levels of the disinfectant by-products iodate(IO3-), chlorite(CIO2-), and bromate(BrO3-)in drinking water. As the oxyhalides emerge from the column, they absorption at267nm. For example, each mole of BrO3-+8Br-+6H+R3Br3-+3H2Obromate makes by the reaction

Bromate near its detection limit gave the following chromatographic peak heights and standard deviations (s). For each concentration, estimate the detection limit. Find the mean detection limit. The blank is 0 because chromatographic peak height is measured from the baseline adjacent to the peak. Because blank =0, relative standard deviation applies to both peak height and concentration, which are proportional to each other. Detection limit is 3 s for peak height or concentration.

State when standard additions and internal standards, instead of a calibration curve, are desirable, and why.

Internal standard graph -- Data are shown below for chromatographic analysis of naphthalene (C10H8), using deuterated naphthalene (C10D8, in which D is the isotope 2H) as an internal standard. The two compounds emerge from the column at almost identical times and are measured by a mass spectrometer.

(a) Using a spreadsheet such asFigure 4-15, prepare a graph of Equation 5-12 showing peak area ratio(C10H8/C10D8)versus concentration ratio role="math" localid="1663559632352" ([C10H8]/C10D8) . Find the least-squares slope and intercept and their standard uncertainties. What is the theoretical value of the intercept? Is the observed value of the intercept within experimental uncertainty of the theoretical value?

(b) Find the quotientrole="math" localid="1663559638520" [C10H8]/[C10D8]for an unknown whose peak area ratio (C10H8/C10D8) is 0.652. Find the standard uncertainty for the peak area ratio.

(c) Here is why we try not to use 3-point calibration curves. For n = 3 data points, there is n - 2 = 1 degree of freedom, because 2 degrees of freedom are lost in computing the slope and intercept. Find the value of Student's for confidence and 1 degree of freedom. From the standard uncertainty in (b), compute the 95 % confidence interval for the quotient[C10H8]/[C10D8] . What is the percent relative uncertainty in the quotient[C10H8]/[C10D8]? Why do we avoid 3-point calibration curves?

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