|Support Center Ultrospec 7000|
What is the beam height ?
Beam height is 15mm above the base of the cuvette. Recommended fill level is at least 20mm.
Can I change the bulb myself ?
The pulsed Xenon lamp in the Ultrospec 7000 is not a customer replaceable part. Xenon lamp replacement can only be carried out by a qualified service engineer. The lamp in the Ultrospec 7000 has a 3 year warranty.
What is the difference in beam technologies ?
There are 3 main types of double beam technology:
Dual Beam with fixed 50:50 split (U7000, U8000 and U9000)
Modern optics and detectors are now more efficient and sensitive so that really a 100% beam split is not necessary in order to have small bandwidths, without any negative effects on signal to noise. This means that instruments are incredibly better value for the performance they achieve and there are less moving parts, making them inherently more reliable. The Ultrospec range achieve 4A and 0.5nm bandwidth with ease.
Double beam with chopper
This is the historical method of achieving a double beam. The chopper is used so that 100% of the lights goes through both paths at different times. It was developed because in those times, detector technology was not sensitive enough to cope with low signal levels that might be seen when very small bandwidths such as 0.1nm are used. So its primary use is in expensive high end instruments where very small bandwidths are needed and where absorbance measurements at 5A or above are needed. Typically optical thin film applications. It is essentially old technology and of course because it is a complex moving part the possibility of problems and breakdowns is increased.
With the introduction of Xenon flash lamps into spectrophotometers the split beam configuration has become necessary; this is because the high intensity flashes from the xenon pulse lamp are not always of equal magnitude. Thus approx. 70% of the energy from the monochromator is passed though the sample with the rest going to a separate feedback detector, enabling a means to taking into account drops and gains in energy via a feedback gain loop in the detector electronics. This stabilises the system and there are no large extra costs elements involved.
For absolute accuracy in your readings, take a reference measurement (zero reading), just before your sample readings. Regularly store a new default baseline, especially after changing a lamp.
Cuvettes - choose carefully
It is important to choose the best cuvette for your application. We recommend the use of Biochrom semi-micro disposable cuvettes, as some other makes may not fit reproducibly in the cell holders.
The instrument beam height of 15mm should be taken into consideration when choosing low volume cuvettes.
For best results choose quartz cuvettes.
Check your cuvette is filled sufficiently to at least 20mm from the base.
Check your cuvette is free from finger prints and scratches on the faces.
For low volume samples such as DNA, a 70µl black walled quartz cuvette can be used eg 80-2103-69. This cuvette should be used in the sample position only, filled with blank solution and a zero reference taken before the sample readings. When choosing a low volume cuvette, a black walled cuvette is best. Better results may also be achieved by using a background correction.
Meaningful results from DNA
When using a 10mm pathlength cuvette, your Ultrospec instrument is capable of measuring DNA concentrations from 5-200ng/µl.
The ideal linear range for DNA is 5-50ng/µl, equivalent to 0.1 to 1Abs at 260nm.
To get meaningful results, the following two criteria must be met:
Abs@260 > twice Abs @230. Abs 260 ≥ 0.1 (lower = solution too dilute).