Firma:                   Beckman

Modell:                DU 650

Kommentar:        Dokumente engl.

General Description

The DU® Series 600 Spectrophotometer is a microprocessor controlled Spectrophotometer intended for use in quantitative and qualitative biological research and industrial procedures that require spectrophotometric measurements in the UV-visible region of the electromagnetic spectrum. If the instrument is used in a manner other than as described, the safety and performance of the instrument can be impaired.

The DU Series 600 Spectrophotometer operates in the wavelength range of 190 to 1100 nm. Models of the instrument are available with either a monochrome or a color video display. Data storage on a 31/2 inch diskette is optional. Various optional accessories are available, to configure the instrument for specific application needs.

The instrument features a graphic video display, which provides operational Information using windowing techniques, and a "mouse" for operator control. The mouse is used to position an arrow on the window. When the arrow points to the desired position, the left button on the mouse is pressed to initiale the desired action. In these instructions, the positioning of the arrow and pressing the left mouse button is called "clicking on".

The instrument has two rapid reading modes: RediRead- for taking readings at a fixed wavelength and RediScan" for making a wavelength Scan.

The instrument has three standard Routine Measurement modes. They include:

Fixed Wavelength - Takes absorbance or transmittance readings at up to 12 wavelengths. Readings at each wavelength can be multiplied by a factor.

Wavelength Scan - Performs wavelength scann in absorbance or transmittance. Data are automatically stored for manipulations includ­ing Trace, zoom, overlay and tabulate. Calculations include peak pick, valley pick, point pick, firnt to fourth derivative, log of absorbance, scatter correction, spectral addition, subtraction and multiplication, and net absorbance. Repetitive Scanning is also performed in this mode.

Kinetics/Time - Calculates the rate of an absorbance versus time reaction with a choice of blank subtraction and graphic display of the data for multiple samples. Data are automatically stored for manipulations including Trace, zoom, overlay and tabulate.

Other Application modes are also available, which include:

Protein Analysis - Calculates the protein concentration using the Bradford, Lowry, Biuret, direct UV method, colloidal gold, and bicinchoninate (BCA). Prepares a standard curve using up to 30 stan­dards. The user can choose to add, delete or rerun individual standards based upon a statistical analysis of the standard curve.

Nucleic Acid - Determines protein impurity in nucleic acid samples based upon the ratio of readings at two wavelengths with a choice of background correction. Protein and nucleic acid concentrations can also be calculated using the Warburg and Christian" coefficients.

Fraction Read/Plot - Collects, plots and tabulates data from a Set of related fractions. Keadings can be corrected for dilution. After data correction, individual fractions can be added, deleted or rerun. Data are plotted versus either fraction number or volume. Other data obtained for the fractions can be Input and plotted with the absorbance data.

Single component quantitative analysis - Calculates a standard curve from up to 30 standards using either linear or nonlinear least-squares regression. Performs statistical analysis on the standard data. Allows the user to add, delete or rerun individual standards to optimize the calibration. Calculates the concentration of samples from the calibration data.

Enzyme Mechanism - Guides the Operator through the necessary steps to calculate Km and Vmax. Displays the following plot typen: Michaelis-Menten, Lineweaver-Burk, Eadie-Hofstee, and Hanes-Woolf. Calculates the Hill constant from the Hill Plot. Graphs inhibitor plots to determine Ki.

Enzyme Activity - Calculates the enzyme activity of large numbers of samples.

Multicomponent analysis - Uses Full Spectrum Quantitation (FSQTM) to calculate the concentration of up to ten components in a mixture from up to 32 standards which are mixtures. Performs a statistical analysis of the standard data to determine the accuracy of the calibration. Allows individual standards to be added, deleted or rerun to optimize the calibration. Calculates the concentration of samples from the calibration data.

Gel Scan - Collects and plots absorbance data as a function of distance for a Sample prepared by electrophoresis. Calculates peak and valley locations, which are used for subsequent area calculation or molecular weight determination.

Performance Validation - Provides a simple procedure to verify the performance of an instrument. Tests which are performed include: wavelength accuracy and repeatability, resolution, baseline flatness, noise and stability.

One model of the instrument also contains a program mode, which allows the user to customize applications by writing programs which blank, collect and Store data at the desired wavelengths, calculate results from the data, prompt the operator, formal and label the output and control sampling accessories.

The instrument is provided with a parallel output for a Dot Matrix Printer and a bidirectional RS-232 communications port that can be configured for either communications or an X-Y Plotter. The communications port can be used for data transfer to and from the instrument and for remote control of the instrument by an external Computer.

A full live of modular sampling accessories is available for the instrument. Included are temperature controlled cell holders, automatic multi-position cell holders, a batch sampler, sipper samplers, and long pathlength cell holders. The automated sampling accessories (sipper samplers, batch sampler, and auto samplers) are designed to operate in the modes described previously to automate analyses. Microsampling capabilities include the use of the 50 µL- Microcell, the 100 µL- Multi-Microcell, and the 5µL Ultra­Microcell.

Principles of Operation

Optical Principle

The optical diagram of the DU Series 600 Spectrophotometer is shown in Figure 1-1.

The DU Series 600 Spectrophotometer is a single beam Spectrophotometer. Light from both sources entern the monochromator, where it is dispersed by the concave holographic grating. Monochromatic light exits the monochromator and Illuminates the sample. The amount of light that passen through the sample is measured by the single photodiode detector.

The focal point of the beam in the sample compartment is on the right-hand side. This location permits the maximum amount of transmitted light to reach the detector from scattering samples. All sampling accessories position the sample at the focal point for best performance with microsamples and gels.

Blanking Method

A blank is always required before data collection; any reading taken without a blank is invalid. A blank reading is taken when < <BLANK> > (located in the permanent menu bar on the bottom of the window) is clicked on.

NOTICE

In the RediRead- Mode the blank command is <ReadBlank>. In the RediScan Mode, the blank command is <ScanBlank>.

When the instrument blanks, the following steps are performed:

1. The monochromator is moved to the proper wavelength. This is the specified wavelength for a single wavelength reading.

2. The proper detector gain value is selected automatically. This minimizes the noise level and maximizes photometric accuracy.

3. Dark current is measured and corrected. This compensation assures accurate readings at high absorbance.

4. In the Wavelength Scan mode, only, a background scan is made. The blank (or reference) is automatically scanned over the same range at the same Speed that the samples will be scanned, so that the background correction is optimal.

This calibration assures repeatable readings every time the instrument is used.

In all modes, a blank solution should be in the sample compartment during the blank. It is suggested that the solvent used to prepare the samples be used for the blank. However, air (no sample) may be used. A new blank reading should be taken each time the solvent is changed.

NOTICE

Plastic cuvettes, glas (Pyrex) cuvettes, and some solvents haue significant absorption in the UV region. Verify that they transmit UV light by Scanning them versus air before using them in the UV region.

To re-zero the instrument at any time between samples, innert the same blank solution and click on «BLANK>>.

The instrument stores the blank and uses it until either the sources are turned off or another blank reading is taken. For best results, the instrument should be blanked frequently, allowing the blank reading to be taken shortly before the sample measurement is taken. A new blank should be read if the instrument has not been used for an hour.

Scanning

The background scan, made as part of the Blank procedure, is stored in the instrument and can be reused for an unlimited number of sample scans as long as the range and scan speed remain the saure; unless the user blanks, the sources are turned off or the instrument is turned off. (The range can be decreased as long as the scan speed remains constant and no new back­ground is required.) When a new background is required, it is indicated on the display.

A new background scan should be made every time a solvent is changed, because the background spectrum will likely be different. A new background scan should also be made if no scan has been made for over an hour. To rescan the background, click on < <BLANK> >, while in the Wavelength Scan mode.

The selected Scanning speed determines the distance between each data point that is collected as the instrument scans through the Chosen region. At 1200 nm/min, a data point is collected every nanometer. At 600 nm/min, a data point is collected every half nanometer.

As the sample data are collected the background is subtracted and the difference in absorbance (or ratio in transmittance) is plotted on the display.

Read Average Time

The noise level of the instrument, and therefore the uncertainty of a sample reading, is decreased by taking a number of readings and averaging them. The instrument takes a reading every 0.05 second. lt takes a series of these readings over a user-selected time and averages them to obtain the blank and sample readings. For example, wich a read average time of 0.5 seconds, ten readings are taken and averaged. The Operator can specify a read average time from 0.05 to 99.9 seconds in all modes except Wavelength Scan and Multicomponent Analysis.

Read averaging is not used in the RediScan and Wavelength Scan modes. Background and sample scann are collected without averaging. Smoothing is used to improve the appearance of the data.

Smoothing

The displayed wavelength scan can be smoothed using a selectable Smoothing function. The calculation, using the Savitzky and Golay" coefficients (as modified for end points by Peter A. Gorry ³ ), is done for every data point in the scan, using the data points before and alter the point of interest. The user selects the total number of data points used for the calculation, from 7 to 25. Use of too few points does not rid the scan of noise. Use of too mang points can cause real peaks to be combined.

Performance Specifications

Scan Speeds                                        120, 240, 600, 1200, 2400 nm/min

Data Collection Rate                                                 20 samplings/second

Response Time                                                                       0.05 second

Wavelength Range                                                             190 to 1100 nm

Wavelength Accuracy                                                                    ±0.5 nm

Wavelength Repeatability                                                               ±0.2 nm

Spectral Bandwidth                                                                        ≤1.8 nm
(from 200 to 680 nm)

Photometric Readout                                                      -0.300 to 3.000 A

                                                                                        or 0.0 to 200.0 %T

Photometric Accuracy                                                                   ±0.005 A

(at 1 A wich NIST 930D

solid Filter at 546 nm)

RMS Noise                                                                           ≤0.0005 A rms

(OA, average of 10 standard

deviations of 10 readings at

0.05 sec intervals at 500 nm)

Stray Light                                                                                       <0.05%

(measured using NaI at

220 nm per ASTM E387-84)

Stability                                                                                          <0.003 A

(OA, constant ambient conditions,

measured for 1 hour at 340 nm)

Baseline Flatness                                                                 ±0.003 A RMS

(from 200 to 900 nm, at 0 A)

Physical and Environmental Specifications

Width                                                                                69 cm (27 inches)

Height                                                                                58 cm (23 inches)

Depth                                                                                53 cm (21 inches)

Weight                                                                                      33 kg (73 lbs)

Lilie Voltage                                                                                                               100/120V±10% or

                                                                                              220/240V±10%

Frequency                                                                                        50/60 Hz

Power                                                                                  200 watts typical

Ambient Temperature

Operating Range                                                  +15 to 40°C (59 to 104°F)

Humidity                                                   <85% maximum relative humidity,

                                                                           not to exceed 32.5°C WBT