Chemists, get in here.

[simms]

When you're doing Atomic Absorption, use of addition methods, why do you take the X-intercept when you have your linear equation? I know it's the concentration, but why do you extrapolate and find that value when absorbance = 0?

More specifically, why do you have to take the NEGATIVE value of that value? I realize it's to make the number go from negative conc to postive, but any other reasonable explanation why?

Picture here of what I'm talking about

 

[dragonballgtz]

When you're doing Atomic Absorption, use of addition methods, why do you take the X-intercept when you have your linear equation? I know it's the concentration, but why do you extrapolate and find that value when absorbance = 0?

😕
<---Stupid

 

[z0mb13]

Originally posted by: dragonballgtz

When you're doing Atomic Absorption, use of addition methods, why do you take the X-intercept when you have your linear equation? I know it's the concentration, but why do you extrapolate and find that value when absorbance = 0?

😕
<---Stupid

time to change ur sig dude!

we already have a

 

[simms]

Oops, should be y=mx+b. not mb+b. 🙂

 

[dionx]

you know that amount is in the unknown soln because the unknown soln was blanked at absorption 0 against itself.

in otherwords, imagine having 6 ppm in the unknown. if you redefined 6 ppm to be "0", points such as 7, 8, 9 would now be 1, 2, 3. so because of redefining your points, when you read the points off the chart, you gotta go backwards to the raw data. so even if you see a -5 on that chart, the raw data is actually 1.

well something like that anyways 😛

 

[simms]

So basically, it's negative so you can move the y-axis around, so that the y-axis will be located when the X-intercept is 0. You "transpose" the graph from x=0 to x=-2.17, so the rest of the plots will be in linear fashion (like how you would do it with a calibration curve?)