The complimentary colour method of selecting wavelength may not be applicable in all situations, perhaps because the solution has no distinct colour, or the solution is of a complex nature and the absorbing species of interest is not the predominant colour. In these circumstances it will be necessary to scan across the spectrum to determine points of maximum absorbance.
Situations also exist where solutions will absorb at more than one wavelength. If this situation is encoun- tered it is usually best to select the wavelength which gives maximum absorbance.
It is always good practice to verify linearity (i.e; concentration vs reading) of the methodology at the se- lected wavelength. Where more than one absorbing wavelength is available, it is probable that one will offer better linearity characteristics than others.
To perform measurements the following procedures should be carried out:
Transmission Mode
This mode is selected by moving the cursor to the %T menu using the LEFT or RIGHT arrow keys. The primary display will show the transmittance, with %T units. The wavelength can be adjusted using the UP and DOWN arrow keys. A calibration routine is initiated by pressing the CAL key. The routine performs a zero% transmission calibration followed by a 100% transmission calibration. A blank (clear) solution should be used for this calibration procedure. (An internal shutter is automatically activated to perform the zero% setting and this part of the routine is therefore independent of the solution in the light path).
The following error codes are possible after a calibration:
Err 1 Dark cal error. This error occurs when the 6300 closes the shutter to block light entering the sample chamber. If the detector output does not fall to a level normally associated with a dark cal then this error is indicated. The most likely cause is that the sample chamber lid is not closed.
Err 2 Light cal error. This error indicates that there is insufficient light to calibrate to 100%. The most likely cause is that light at the selected wavelength is being absorbed by a sample in the sample chamber. This error can also be caused if the lamp has failed.
A calibration resets the sample number to unity.
Absorbance Mode
This mode is selected by moving the cursor to the ABS mode using the LEFT or RIGHT arrow keys. The primary display will show the absorbance, with ABS units. The wavelength can be adjusted using the UP and DOWN arrow keys. A calibration routine is initiated by pressing the CAL key.The routine performs a zero% transmission calibration followed by a 0.000 Absorbance calibration. A blank (clear) solution should be used for this calibration procedure. (An internal shutter is automatically activated to perform the zero% setting and this part of the routine is therefore independent of the solution in the light path). The instrument will display overrange
(1. ABS) absorbance during the dark calibration. The possible error conditions are the same as for the transmission mode.
7 | 6300/REV |
|
