deebird24

1353580400[/url]' post='714604']

Was your lecturer questioning that you used the log of the Absorbance to plot the points on regular graph paper or semi-log paper? If so, then I agree with your lecturer. Instead, keep the original Absorbance values and plot them on log-log paper.

 

I also agree with CharonY. Because you're halving the concentrations serially, simply double an Absorbance and compare it to the previous Absorbance. There's a certain spot where the readings obviously begin to "go wrong". You can also see this in the log-log plot — some points will fall on a straight line, but others will deviate significantly. If it happened at the other end of the dilutions, then it would be a matrix effect.

We had to submit electronically, so I used Excel and performed a log-log graph. I am not questioning the absorbance results, I needed help from people to see how they would scale these values, would they too use a LOG graph? Given that the values range from 2 to 3000. I thought I done the right thing, I thought that data points should be spread evenly on a graph, but if you just plot the [C] as say, 3000, 1500, 1000, 500 and 0. - then what you get is a big clump of data points before the 500 mark on the X axis. This was why I converted to LOG. I just thought graphs were supposed to be spread out, but as I said originally, my tutor has asked me WHY I done log-log graph.

Hey folks,

Any help for this would be gratefuly recieved. I am so confused about where I went wrong recently with a graph. I used Excel, and converted the numbers into LOG to allow for a greater spread of the data, but my lecturer has now asked me WHY did I do that?

As you can see the data points have quite a high range, as the concentration was diluted by it's exponent each time (is that the correct term?) I'm not great at maths, but it was diluted by half each time. The absorbance given was the Y axis. I got a straight line and was using the line to find an unknown concentration based on y=mx+c if that makes sense? Please reply to me in non=maths speak, as I am so poor at maths. I have called a local tutor to come help me in the meantime, but I'd love to hear back if anyone knows how they could have plotted this on Excel without all data values being clumped at the bottome of the graph, without converting to LOG

Concentration Absorbance

3000 3.148

1500 1.627

750 0.88

375 0.453

187.5 0.257

93.75 0.146

46.88 0.095

23.44 0.076

11.72 0.057

5.86 0.05

2.93 0.047

1.46 0.042

As you can see the concentration was double dilution, and I felt the only way I could fit this into a coherent graph was to convert it into LOG, but my lecturer has said, why did you that?

Hey folks,

If any of you have ever done an ELISA and have spectro readings like these, can you tell me if you would do a LOG graph for them , or how you do them on excel?

Concentration Absorbance

3000 3.148

1500 1.627

750 0.88

375 0.453

187.5 0.257

93.75 0.146

46.88 0.095

23.44 0.076

11.72 0.057

5.86 0.05

2.93 0.047

1.46 0.042

As you can see the concentration was double dilution, and I felt the only way I could fit this into a coherent graph was to convert it into LOG, but my lecturer has said, why did you that?