 |
|
|
| |
|
|
 |
|
|
 |
|
|
 |
|
|
 |
|
Why it's a good idea to use self masking cuvettes |
|
 |
for low volume work. I performed this experiment a few years ago, and have been dying to try it for the last three years on a Cary 500! Well - at long last I got a spare few moments and here are the results. The experiment:
1. Take a suitable visible dyestuff, and make up a solution to give you a peak Absorbance measurement of 3+ Absorbance. In this case I used Sap Green, measured at 428 nm, with a 1.0 nm SBW.
2. Call this '100' as a top standard - and serially dilute to produce '75', '50', and '25' respectively.
3. Using a type 18/B - fill with water, and zero the Cary.
4. Re-measure the blank, and then each standard in turn.
5. Repeat 3, and 4 using a type 18.
6. Plot, and compare the 'Beer-Lambert' linear response! |
| 1. Using the type 18/B cells, I've restored my faith in my analytical expertise, in the fact that the series 0 -75 (2.5 A) is a perfect (linearity = 1) straight line. Linearity to 3.3 (100) isn't bad either at 0.9993, but you are beginning to see the stray light characteristics of the Cary at this point |
Black Walled |
Blank Corrected |
| 0 |
0.0004 |
0 |
0.0000 |
| 25 |
0.8508 |
25 |
0.8505 |
| 50 |
1.7149 |
50 |
1.7145 |
| 75 |
2.5611 |
75 |
2.5607 |
| 100 |
3.3106 |
100 |
3.3103 |
| 2. Using the type 18 - boy what a difference! On this evidence, I don't think I'd want to use this type of cell (without any masking) to measure more than 0.5 A? |
Black Walled |
Blank Corrected |
| 0 |
0.0004 |
0 |
0.0000 |
| 25 |
0.8177 |
25 |
0.8173 |
| 50 |
1.4730 |
50 |
1.4726 |
| 75 |
1.8064 |
75 |
1.8060 |
| 100 |
1.8999 |
100 |
1.8995 |
|
 |
 |
 |
Clear Walled |
 |
Linear Black Walled |
 |
Black Walled |
|
| Black Walled |
Clear Walled |
|
Difference |
% Difference. |
| 0.0000 |
0.0000 |
0 |
0 |
0 |
| 0.8505 |
0.8173 |
25 |
0.0331 |
3.9 |
| 1.7145 |
1.4726 |
50 |
0.2420 |
14.1 |
| 2.5607 |
1.8060 |
75 |
0.7547 |
29.5 |
| 3.3103 |
1.8995 |
100 |
1.4108 |
42.6 |
|
|
|
|
| |
| |
|
|
|
Starna
Scientific Limited, 52-54 Fowler Road, Hainault, Essex
IG6 3UT England Tel: +44 (0)20 8500 1264 sales@starna.com © Starna Group all rights reserved 1996-2007 |
|
|
|
|
