young researcher was evaluating a standard method for determining the methylmercury content in blue fin tuna using high performance liquid chromatography (HPLC). She determined the standard deviation (?)(s) for the method to be 0.440.44 ppb and assumed that ?s was a good approximation of ?σ . As a test, she used this method to evaluate the methylmercury content in a National Institutes of Standards and Technology (NIST) standard and determined the unknown amount to be within 0.210.21 ppb (?)(μ) of the known mean with 99% probability. How many replicate measurements of the NIST standard did the researcher perform?

20 To determine the organic material in a dried lake bed, the percent carbon by mass is measured at two different locations. To compare the means of the two different locations, it must first be determined whether the standard deviations of the two locations are different. For each location, calculate the standard deviation and report it with two significant figures. location 1 standard deviation: location 2 standard deviation: What is the calculated F value for comparing the standard deviations? Fcale = no Sample 1 2 3 4 5 Are the standard deviations for the two locations significantly different at the 95% confidence level? O yes Location 1 (% Location 2 (%) C) C) 10.40 10.10 10.30 10.90 10.30 10.30 10.40 10.80 10.20 10.40

In the determination of ethanol concentration in alcoholic beverages using the GCFID method, why do we need to calculate the coefficient variation (CV). standard deviation, repeatability, response factor and response ratio? And how to calculate this parameter?

Five blood samples got these results: 0.752, 0.756, 0.752, 0.751, 0.760 ppm The standard deviation of these results is: Please fill in the space with a numerical value with four digits or two decimal places without units and no exponents Answer:

Chemistry   0.1237 (±0.0001) g of sodium carbonate (Na2CO3) required 22.46 (±0.02) cm3 of aqueous HCl for complete neutralisation. Determine the concentration of the HCl in mol dm–3 together with its uncertainty in mol dm–3 to an appropriate number of digits. You may assume the error in the molar mass of Na2CO3 is negligible.

An analysis where we know what analytes we are looking for is called An analysis where we do not know what analytes are in the sample is called a An example is A) untargeted, confirmation, targeted, Comprehensive drug screen B) targeted, confirmation, untargeted, comprehensive drug screen C) targeted, comprehensive drug screen, untargeted, confirmation analysis. An example is analysis. ▪ True or false: The purpose of the internal standard is to make quantitation of the analyte insensitive to injection errors

In a particular trial, a student got a value for R of 0.083. Calculate the percent deviation of this result. Enter a number without the % sign. The percent deviation should be reported as a positive value.

Which is correct?     Random errors affect accuracy and systematic errors affect precision.     An accurate result shows agreement with the true or accepted value.     Precise results can contain significant random error, but little systematic error.     The standard deviation is a good measure of accuracy.   Polydimethylsiloxane (PDMS) stationary phases have low polarities.  Which of the following statements is TRUE about gas chromatography using PDMS stationary phases?     The gas chromatography column is typically packed with silica microparticles.     An oven is used to control the column temperature because a constant temperature is always needed in gas chromatography     Octane (C8H18, boiling point: 126 ºC) is eluted later than dodecane (C12H26, boiling point: 216 ºC)     3-Pentanone ((C2H5)2CO, boiling point: 102 ºC) is eluted later than propanol (CH3CH2CH2OH, boiling point: 97 ºC)

Often the analyst will compare known quantities of analyte to unknown quantities of the material to be analyzed. This may be done in one of three ways: -use calibration curves; use standard additions; or use internal standards. The method of standard additions would be used when A) the quantity of sample analyzed or the instrument response varies from run to run.   B) the standard solutions and the unknown solution all have similar characteristics are unaffected by the other material in the sample.   C) the sample composition is unknown or complex and affects the analytical signal.

Blank determinations reveal errors due to interfering contaminants from the reaagents and vessels employed in the analysis.