Spectrum (Modular LC DAD)

Store

Store defines the points on signal A at which spectra will be taken and saved. The additional signals are not used to control spectra acquisition.

The availability of spectral storage options depends on the CDS application. Not all CDS applications support all spectral storage options.

None	No spectra are taken.
Apex	A spectrum is taken at the apex of the peak. (Not available for the G7115A, G7117A/B or the HDR-DAD Cluster.)
Apex + Baselines	Spectra are taken at the apex, and baselines of the peak. (Not available for the G7115A, G7117A/B/C or the HDR-DAD Cluster.) Note: This mode is available only if the application supports peak-detection functionality.
Apex + Slopes	Spectra are taken at the apex, upslope, and downslope of the peak. (Not available for the G7115A, G7117A/B/C or HDR-DAD Cluster.) Note: This mode is available only if the application supports peak-detection functionality.
Apex + Slopes + Baselines	Spectra are taken at the apex, baselines, upslope, and downslope of the peak. (Not available for the G7115A, G7117A/B/C or the HDR-DAD Cluster.) Note: This mode is available only if the application supports peak-detection functionality.
All in Peak	All spectra within the peak are taken. (Not available for the G7115A, G7117A/B/C or the HDR-DAD Cluster.) Note: This mode is available only if the application supports peak-detection functionality.
Note: The three spectra acquisition types mentioned above are also referred to as peak-controlled spectra acquisition. The peak detection is done by the detector firmware based on the threshold and peakwidth parameters you set for the DAD. If you want to use peak-controlled spectra storage, make sure that you set these parameters to recognize all the peaks of interest. The integration algorithm also includes peak detection based on the threshold and peakwidth parameters set in the integration events.
Every 2nd spectrum	Spectra are taken continuously as for All, but only every second spectrum is stored; other spectra are discarded. This reduces the amount of data storage necessary. (Not available for the G7115A, G7117A/B/C or the HDR-DAD Cluster.) Note: This mode is available only if the application supports peak-detection functionality.
All	Spectra are taken continuously depending on the setting of the Peakwidth. Eight spectra are acquired per Peakwidth. The acquisition time for one spectrum is slightly less than the Peakwidth divided by 8, that is, greater than or equal to 0.01s and less than or equal to 2.55s.

If there are no peaks in Signal A, there are no spectra. You cannot process spectra present in other signals.

Range

Range defines the wavelength range for spectral storage.

Limits:

G1315A/B/C/D	190 to 950 nm. The high value must be greater than the low value by at least 1 nm.
G4212A/B and G7117A/B/C	190 to 640 nm.

The precision with which you can set the wavelength values depends on the CDS application.

Step

Step defines the wavelength resolution for spectral storage.

Limits: 0.10 to 100.00 nm.

The precision with which you can set the Step depends on the CDS application.

Threshold (not G7117A/B/C)

The threshold is the height in mAU of the smallest expected peak. The peak detector ignores any peaks that are lower than the threshold value and does not save spectra.

Limits: 0.1 to 1000.0 mAU in steps of 0.1 mAU.

G4212 and G7117 Spectral Data Rate

The G4212A and G7117A/B/C DADs have a maximum overall frequency for data processing. Various settings have an impact on the data processing capabilities: the optical resolution, the spectrum length, and the spectral data rate. Optical resolution and spectrum length together result in the number of wavelength positions where the spectra are recorded. Large number of wavelength positions reduce the maximum data rate. For extreme application requirements, the system can be optimized for high spectral data rate or for wide spectral ranges and/or high spectral resolution.

For the G4212A and G7117A/B/C DADs, the data rate for spectral acquisition depends on the peakwidth as well as the number of data points per spectrum. For example, for the default values of a scan from 190 nm to 400 nm with a Step of 2, 106 data points are acquired:

(400 - 190) / 2 + 1 = 106

For the smallest peak width (<0.0012), this would result in a spectral data rate of 160 Hz (see ^* in the table below).

For a Step of 1, the spectrum would contain 211 data points, and would result in a spectral data rate of 80 Hz (see ^** in the table below). The data rate is lower because the resolution of the optical spectrum has been increased.

For additional information, see Peakwidth (Modular LC DAD)

Peak width at half height (min)	Response (sec)	Data rate (Hz) for Signals	Data rate (Hz) for Scan Data
			<= 126 points	<= 251 points	<= 501 points	<= 1024 points
< 0.0012 (0.0015625)	< 0.01 (0.015625)	160	160*	80**	40	20
> 0.0012 (0.0015625)	0.02 (0.03125)	160	160	80	40	20
> 0.0025 (0.003125)	0.05 (0.0625)	80	80	80	80	40