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Homework Help: Two point estimates am i correct

  1. Dec 10, 2005 #1
    Can anyone tell me if this concentration calculation is correct please, its my first attempt and a bit unsure.
    Two point determination of cocaine sample
    Cocaine (mg/ml) Average peak height
    0.015 13059
    0.20 98496
    Unknown (2mg/ml) 61136
    General equation Y = mx + c
    Equation 1 standard 1: 13059 = 0.015m + c
    Equation 2 standard 2: 98496 = 0.20m + c
    98496 – 13059 = 85437
    0.20 – 0.015 = 0.185
    therefore 85437 = 0.185m + 0
    85437 / 0.185 = m
    m = 461821.62
    c = 13059 = (0.015 X 461821.62)
    13059 – (0.015 X 461821.62) = 6132
    So, Y = 461821.62 X + 6132
    Unknown therefore:
    61136 = 461821.62 X + 0
    = 61136 – 0 / 461821.62 = 0.13
    0.13 / 2 X 100 = 6.6%
     
  2. jcsd
  3. Dec 10, 2005 #2

    cronxeh

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    Gold Member

    Why? You just determed that c is 6132. Following your logic it should be
    61136 = 461821.62 X + 6132

    0.20 – 0.015 = 0.19 <-- here you have only 2 significant figures.
    therefore 85437 = 0.19m
    85437 / 0.19 = m = 450000

    Hence 61136 = 450000*x + 6132
    55004 = 450000*x , x = 0.12
    0.12/2 = 0.06 = 6%
     
  4. Dec 10, 2005 #3
    not bad for a first attempt, close but no cigar, thankx for the pointers
     
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