ACS Analytical Chemistry Exam with Correct Solutions

ACS Analytical Chemistry Exam with Correct Solutions standard deviation (s) - Answer -the square root of the variance % relative standard deviation (%RSD) - Answer -Standard deviation divided by mean times 100 Grubbs test (Gcalc) - Answer -|Questionable value - mean/ std dev| If that is larger than the Gtable value then the value is thrown out. Locate Gtable value based on number of values in data set. Used to define outliers z score - Answer -(x- xavg)/s F Test - Answer -used to compare precision (s2)^2/(s1)^2 (should always be >1) Use n-1 to find on table. Fcalc> Ftable -- There is some noise or error External standard - Answer -use standard solutions spanning a range of conc, measure response Internal standard - Answer -substance similar to analyte (ie deuterated); used to normalize signal by reducing random error Standard Addition - Answer -ideal for analyzing sample in a complex matrix; add known standard to constant amount of sample; x-int =[sample] Box car average - Answer -minimizes distance between data points and best fit line/ minimizes standard deviation Limit of detection (LOD) - Answer -3*std dev Limit of quantitation (LOQ) - Answer -10* std dev