Exam 6: Quality Assurance and Calibration Methods

A____________________ is a sample that has been exposed to the site of sampling,containing all components except analyte,and it is taken through all steps of the analytical procedure.

A set of five solutions are prepared by delivering 10 mL of unknown sample and increasing volumes of standard (0,5,10,15,and 20 mL)into 50-mL volumetric flasks.Analytical reagents are then added and diluted to volume.The x-intercept is −3.90 mM.What is the unknown concentration?

There are several types of precision involved with method validation.

The detection limit for caffeine analysis must be calculated.Eight absorbance readings from a caffeine sample close to the estimated detection limit are 0.1239,0.1098,0.1182,0.1150,0.1219,0.1251,0.1199,and 0.1099.The average absorbance for eight blanks is 0.0182.The slope of a calibration curve is 0.59 /mM.What is the detection limit?

The response factor,F,for the analysis of pentane with the internal standard decane is 3.5.Which statements below are INCORRECT for the analysis? I The pentane concentration is 3.5 times greater than the decane concentration. II The decane concentration is 3.5 times greater than the pentane concentration. III Detector response to pentane is 3.5 times greater than detector response to decane. IV Detector response to decane is 3.5 times greater than detector response to pentane.

The percent by mass octane is quantified for an organic sample via GC using decane as the internal standard.A GC vial containing 0.5023 grams organic sample and 0.2384 grams octane is prepared and analyzed,returning peak areas of 119,993 for octane and 83755 for decane.If a response factor of 2.50 from previous work analyzing octane with a decane internal standard is used,what is the percent by mass octane in the organic sample?

The____________________ state(s)what steps will be taken and how they will be carried out.

Which are TRUE statements regarding internal standards? I The response factor is calculated by using a mixture containing known amounts of analyte and internal standard and by using detector response to the analyte and the internal standard. II Internal standards are useful where instrument response or quantity of sample analyzed varies over time. III Detector response is inversely proportional to concentration. IV Detector response to analyte and internal standard is assumed to be constant over a range of concentrations.

Which statement regarding standard addition to a single solution is FALSE? A Analyte signal is measured after each standard addition.

A water sample collected downstream from a gold-mining operation returns a cyanide concentration of 6.18 g/L CN⁻.A 10-mL aliquot is spiked with 100 L of 500.0 g/L sodium cyanide and analyzed.Analysis returns a cyanide concentration of 10.5 g/L CN⁻.What is the percent recovery for the spike?

There are many studies required to validate an analytical method.Which of the studies below is not required for method validation?

A____________________ is an analytical result that indicates the sample concentration is below a stated limit when the concentration is actually above the limit.

A solution is 2.0% by mass compound A and 3.5% by mass compound I.Separation via GC returns peak areas of 38234 for compound A and 23880 for compound I.Calculate the response factor.

A(n)________________________________________is a known amount of compound,different from the analyte,that is added to the unknown.

____________________ is the concentration range over which there is measurable instrument response.

Which statement regarding the multiple solutions with constant volume standard addition method is FALSE?

The____________________ is everything in the sample,except analyte.

Which of the following is(are)not a way to demonstrate the accuracy of a method? I Determine the limit of detection for the method. II Analysis of a certified reference material in a matrix similar to the sample. III Compare the results between two or more different analytical methods. IV Analyze a blank sample with a known amount of analyte in the same matrix as the sample.

A chemist is tasked with determining the concentration of nickel for a water sample drawn from a well next to a nickel mine.To analyze the sample using atomic absorbance spectroscopy (AAS),she prepares six samples (0-5)by adding 10.00 mL well water to a 50.00-mL volumetric flask,then adding an increasing volumes of 25.00-ppm nickel solution,diluting the resulting solution to 50.00 mL with 0.1 M HNO₃.Following AAS analysis,a graph of absorbance versus ppm nickel standard gave a best-fit line y = 0.0428x + 0.0487.Calculate the ppm nickel in the well water sample.

A____________________ is a sample containing all components except analyte,and it is taken through all steps of the analytical procedure.