StrayLightP - Stray light curve correction

Description

J E Patterson - jepspectro.com - version 20150902

Spectrophotometers have some stray light or detector dark current which causes the calibration to be non linear at high absorbances.

Absorbance = Log (Incident light Intensity)/(Transmitted light Intensity).

This program corrects for the calibration curvature caused by the presence of stray light.

You can enter f USER to avoid the f or GSB key during data input.

Input two standard concentration values y1 ENTER y2 GSB A.
Input two corresponding absorbances x1 ENTER x2 GSB B.
The % stray light is displayed. This is stored in register 8.

Input an unknown sample absorbance x GSB D the resulting concentration y is displayed and stored in register 9

Example 1:
Sample data: [y,x] 5,0.53 10,0.87].
5 ENTER
1 0 GSB A
. 5 3 ENTER
. 8 7 GSB B
Stray light is 9.62%

This curvature is not unusual for Atomic Absorption spectrometry. Spectrophotometry can be much more linear in the near absence of stray light.

Example 2:
Unknown sample absorbance is 0.74
. 7 4 GSB C
The unknown sample concentration is 7.66 units, using the same concentration units as the standards.
Repeat x GSB C for further samples.

Program Resources

Labels

Name Description
 A y1 Enter y2 A - Enter concentrations
 B x1 Enter x2 B - Enter absorbances
 C Enter absorbance x to get concentration y
 1 Start of loop

Storage Registers

Name Description Name Description
 1 x1 concentration of standard 1  8 % stray light
 2 x2 concentration of standard 2  9
 4 Stray light fraction .1 y1 absorbance of standard 1
 5 Stray light old .2 y2 absorbance of standard 2
 6 Temp 1 .3 y absorbance
 7 Temp 2 I Loop counter register, decrement 20 to 0.

Program

Line Display Key Sequence Line Display Key Sequence Line Display Key Sequence
000 025 1 1 050 45 4 RCL 4
001 42,21,11 f LBL A 026 40 + 051 26 EEX
002 44 2 STO 2 027 43 13 g LOG 052 2 2
003 33 R⬇ 028 30 053 20 ×
004 44 1 STO 1 029 44 6 STO 6 054 44 8 STO 8
005 43 32 g RTN 030 45 2 RCL 2 055 43 32 g RTN
006 42,21,12 f LBL B 031 45 1 RCL 1 056 42,21,13 f LBL C
007 44 .2 STO . 2 032 10 ÷ 057 44 .3 STO . 3
008 33 R⬇ 033 20 × 058 1 1
009 44 .1 STO . 1 034 44 7 STO 7 059 45 .3 RCL . 3
010 2 2 035 45 .2 RCL . 2 060 13 10ˣ
011 0 0 036 45 7 RCL 7 061 30
012 44 25 STO I 037 30 062 45 4 RCL 4
013 0 0 038 13 10ˣ 063 20 ×
014 44 4 STO 4 039 1 1 064 1 1
015 42,21, 1 f LBL 1 040 30 065 40 +
016 45 4 RCL 4 041 1 1 066 43 13 g LOG
017 44 5 STO 5 042 36 ENTER 067 30
018 45 .1 RCL . 1 043 45 .2 RCL . 2 068 45 6 RCL 6
019 1 1 044 13 10ˣ 069 10 ÷
020 45 .1 RCL . 1 045 30 070 45 1 RCL 1
021 13 10ˣ 046 10 ÷ 071 20 ×
022 30 047 44 4 STO 4 072 44 9 STO 9
023 45 5 RCL 5 048 42, 5,25 f DSE I 073 43 32 g RTN
024 20 × 049 22 1 GTO 1