NanoDrop Lite User Guide Rev A Jan 2012

© 2012 Thermo Fisher Scientific Inc. All rights reserved. Trademarks are the property of Thermo Fisher Scientific Inc., and its subsidiaries. Thermo Fisher Scientific Technical Support 3411 Silverside Road Bancroft Building, Suite 100 Wilmington, DE 19810 U.S.A. Telephone: (302) 479-7707 Fax: (302)792-7155 E-mail: [email protected] www.thermoscientific.com/nanodrop

Thermo Fisher Scientific Inc. provides this document to its customers with a product purchase to use in the product operation. This document is copyright protected and any reproduction of the whole or any part of this document is strictly prohibited, except with the written authorization of Thermo Fisher Scientific Inc. The contents of this document are subject to change without notice. All technical information in this document is for reference purposes only. System configurations and specifications in this document supersede all previous information received by the purchaser. Thermo Fisher Scientific Inc. makes no representations that this document is complete, accurate or errorfree and assumes no responsibility and will not be liable for any errors, omissions, damage or loss that might result from any use of this document, even if the information in the document is followed properly. This document is not part of any sales contract between Thermo Fisher Scientific Inc. and a purchaser. This document shall in no way govern or modify any Terms and Conditions of Sale, which Terms and Conditions of Sale shall govern all conflicting information between the two documents.

For Research Use Only. This instrument is not a medical device and is not intended to be used for the prevention, diagnosis, treatment or cure of disease.

C

Contents Chapter 1

Thermo Scientific

NanoDrop Lite User Guide...1 General Safety... 2 NanoDrop Lite Basic Operation... 2 Installation... 2 Keypad Operation... 4 Menu Selection... 4 Measurement Basics... 7 Nucleic Acid Measurements... 7 Making a Measurement... 7 Nucleic Acid Measurement Screen... 8 Nucleic Acid Calculations... 8 Protein Measurements... 9 Making a Measurement... 9 Protein Measurement Screen... 10 Protein Calculations... 10 Transferring Data From Instrument to Computer... 12 Helpful Information for Measuring Samples... 13 Sample Volume Requirements... 13 Sample Measurement Accuracy and Reproducibility... 14 Sample Homogeneity... 15 Sample Carryover... 15 A260/A280 Ratio... 15 Effect of Evaporation and Solvent Usage... 16 Using NanoDrop Lite With Optional Printer... 16 Troubleshooting Paper Feed... 19 Printing Labels... 20 Printer Output... 21 Printer Serial Number Location... 21 Maintenance... 22 Calibration... 22 Calibration Check... 22 Cleaning... 24 Reconditioning... 25 Solvent Compatibility... 26 Decontamination of Upper and Lower Pedestals... 26 Diagnostics... 26

NanoDrop Lite

iii

Contents

Troubleshooting... 27 Error Messages... 27 Frequently Asked Questions... 27 Warranty... 30

iv

NanoDrop Lite

Thermo Scientific

NanoDrop Lite User Guide The Thermo Scientific NanoDrop Lite is a small, stand-alone UV spectrophotometer developed specifically for microvolume measurements of nucleic acids and purified proteins. The NanoDrop™ Lite comes with preloaded software and is designed to be used without a computer. The NanoDrop Lite can also be connected to an accessory printer for printing measurement information on labels.

The sample retention system of the NanoDrop Lite is identical to that used in all NanoDrop instruments: surface tension is used to hold 1-2 μl of sample between two stainless steel pedestals that contain optical fibers. Using Light Emitting Diode (LED) technology, the NanoDrop Lite measures the sample absorption at 260 and 280 nm and corrects for scattering and background effects in the sample with light from a reference wavelength at 365 nm. The A260 and A280 is calculated with respect to the baseline absorbance at 365 nm. Thus the NanoDrop Lite provides accurate and reproducible measurements for microvolume samples with no need for cuvettes. When measuring nucleic acids (dsDNA, ssDNA and RNA), the NanoDrop Lite provides concentration information using the A260 measurement and sample purity information using the A260/A280 ratio. When measuring purified protein samples, the NanoDrop Lite provides concentration information using the A280 measurement.

Thermo Scientific

NanoDrop Lite

1

NanoDrop Lite User Guide General Safety

General Safety NOTICE Be sure that all persons operating this system read the site and safety manual first.

CAUTION Operating the instrument with the cover off exposes the operator to the instrument’s sharp metal edges and delicate fiber optics. Removal of the cover may also void the warranty. Note The NanoDrop Lite is supplied with a 6 V power supply. Use only the power supply provided with the instrument. The unit also comes with a grounded power cord. Plug this cord into a properly grounded outlet. Use of the instrument in a manner not specified by the manufacturer may impair the protection provided by the supplied power cord and power supply. The power supply can remain plugged into the NanoDrop Lite while the instrument is not in use. When the instrument is plugged in but not in use, the power consumption is ~5 W and the LED sources are not energized. Since the NanoDrop Lite does not use a power switch, it is recommended that it is positioned in a fashion that allows easy access to the power connection so that it can be easily disconnected.

NanoDrop Lite Basic Operation Installation Figure 1.

Back view

6VDC 18W

External power supply

2

NanoDrop Lite

Thermo Scientific

NanoDrop Lite User Guide NanoDrop Lite Basic Operation

Figure 2.

Left side view

Power Indicator

Port for customer USB memory device

For factory use only Example memory device for customer data

Figure 3.

Bottom view

Connector used with optional printer

CE label with serial number

Thermo Scientific

NanoDrop Lite

3

NanoDrop Lite User Guide NanoDrop Lite Basic Operation

Keypad Operation Figure 4.

Basic screen features

Autoprint On icon Baseline correct Off icon

Message bar Button functions Buttons Key or button

Function

•When pressed, initiates a specific function as displayed above each button •Functions will change depending on the screen •Arrow keys that control the direction of the cursor Select

•Accepts entered or selected values •Advances to the next parameter or screen

Home

•Returns to the main menu

Blank

•Initiates blank measurement

Measure

•Initiates sample measurement

Change

•Allows user to change settings

Back

•Returns to previous screen

Menu Selection Figure 5. Home screen

4

NanoDrop Lite

Thermo Scientific

NanoDrop Lite User Guide NanoDrop Lite Basic Operation

DNA

dsDNA

factor = 50

ssDNA

factor = 33

RNA

RNA

factor = 40

Protein

Protein (1A/cm = 1 mg/ml)

Default general reference setting

Protein (IgG)

E1%=13.7

Protein (BSA)

E1%=6.7

Tools & Settings

Figure 6.

Function

Tools & Settings screen

Settings

Thermo Scientific

Autoprint: On/Off

•Off is the default state. •When Autoprint On is selected, and the NanoDrop Lite is docked onto the printer, a label will print automatically every time a measurement is made. •Labels will not be printed automatically if Autoprint Off is selected.

Baseline correct: On/Off

•On is the default state. •It is best to keep Baseline correct setting On. •If Baseline correct setting is Off, the instrument no longer uses the 365 nm correction.

Date & Time

•Set at the factory for Eastern Standard Time, USA. •Upon instrument installation, ensure the time and date is set for the local time zone.

NanoDrop Lite

5

NanoDrop Lite User Guide NanoDrop Lite Basic Operation

Tools & Settings

Function

System Info Product

•NanoDrop Lite

Serial Number

•Instrument identification.

Firmware Version

•Version number of firmware currently installed.

Cal. Check Date

•Date shown is the last date the calibration was checked on the NanoDrop Lite.

Reset Sample ID Reset Sample ID? Yes/No

•When Yes is selected, the instrument will reset sample ID number back to #1.

Calibration Check •Verifies that the pathlengths are within tolerance. •It is recommended that a pedestal calibration check be performed every six months to verify that the instrument is performing within specifications. New Cal. Check

•Follow on-screen directions to perform new calibration check using the CF-1 Calibration Check solution. •See NanoDrop Lite Calibration Check Procedure for more details.

View Previous Cal. Check

•Displays data from last calibration check.

Diagnostics •Follow on-screen directions. Test checks the LED output and ensures that arm sensor and pedestals are operating correctly. •Results will be Pass/Fail. Sample History •Displays previous measurements •Print option available. •The instrument memory holds data for 500 samples. Sample data #501 overrides sample data #1.

6

NanoDrop Lite

Thermo Scientific

NanoDrop Lite User Guide Nucleic Acid Measurements

Sleep

Function

•When Sleep is selected, the instrument enters a low-power state. •The screen will go black and the blue LED below the keypad will pulse. •To wake the instrument, push any button or raise the arm.

Measurement Basics A 1-2 μl sample is pipetted directly onto the lower pedestal. A fiber optic cable (the source fiber) is embedded within the lower pedestal while a receiving fiber is imbedded in the upper pedestal and the arm. Light emitted from the LEDs traverses the sample and absorbance is measured using a silicon photodiode. Raise the arm and pipette the sample onto the lower pedestal. 1. Lower the arm and initiate a measurement. The sample column is automatically drawn between the upper and lower pedestals and the measurement is made. The formation of the liquid column during measurement may be viewed through the aperture on the side of the NanoDrop Lite arm. 2. When the measurement is complete, raise the arm and wipe the sample from both the upper and lower pedestals using a dry, lint-free laboratory wipe. Tip Simple wiping with a dry laboratory wipe is sufficient to prevent sample carryover in subsequent measurements.

Nucleic Acid Measurements Nucleic acid samples can be easily checked for concentration and purity using the NanoDrop Lite spectrophotometer. To measure nucleic acid samples (dsDNA, ssDNA and RNA) select the appropriate Nucleic Acid application from the Home screen.

Making a Measurement 1. Select the appropriate application from the Home screen (DNA or RNA). For DNA measurements, select either the dsDNA or ssDNA assay. 2. Following the on-screen instructions, establish a blank by pipetting 1-2 μl of the blanking buffer onto the bottom pedestal, lower arm and press Blank. 3. When measurement is complete, raise the arm and wipe the buffer from both the upper and lower pedestals using a dry laboratory wipe.

Thermo Scientific

NanoDrop Lite

7

NanoDrop Lite User Guide Nucleic Acid Measurements

4. Confirm Blank by pipetting a fresh aliquot of blanking buffer onto the bottom pedestal, lower the arm and press Blank. 5. When measurement is complete, raise the arm and wipe the buffer from both the upper and lower pedestals using a dry laboratory wipe. 6. Measure sample by pipetting 1-2 μl of sample onto the bottom pedestal, lower arm and press Measure. 7. Wipe the upper and lower pedestals using a dry laboratory wipe and the instrument is ready to measure the next sample. Note Use a fresh aliquot of sample for each measurement.

Nucleic Acid Measurement Screen Figure 7.

Sample measurement screen Application Sample number Absorbance Purity ratio Concentration Time & date sample and blank measurements were collected

Nucleic Acid Calculations The NanoDrop Lite should be used to measure the concentration of purified nucleic acid samples. Direct nucleic acid concentration measurements assume a purified sample as all absorbance at 260 nm is included in the calculation of the nucleic acid concentration. Carryover of nucleotides, primers, purifying reagents, and cell material into the measured nucleic acid sample will overestimate the nucleic acid concentration. For nucleic acid quantification, the Beer-Lambert equation is modified to use a conversion factor with units of ng-cm/μl. The modified equation used for nucleic acid calculations is the following:

8

NanoDrop Lite

Thermo Scientific

NanoDrop Lite User Guide Protein Measurements

c

= (A *CF)/l

where, c

= the nucleic acid concentration in ng/μl

A

= the sample absorbance

CF = the conversion factor in ng-cm/μl l

= the pathlength in cm

The generally accepted conversion factors for nucleic acids are: • Double-stranded DNA: 50 ng-cm/μl • Single-stranded DNA: 33 ng-cm/μl • RNA: 40 ng-cm/μl Table 1. Nucleic acid concentration range Sample Type

Lower Detection Limit

Upper Detection Limit

Typical reproducibility (10 replicates, SD = ng/μl; CV=%)

dsDNA

4.0 ng/μl

1500 ng/μl

4.0 - 100 ng/μl: +/- 2 ng/μl >100 ng/μl: +/- 2%

ssDNA

2.6 ng/μl

990 ng/μl

2.6 - 66 ng/μl: +/- 1.3 ng/μl >66 ng/μl: +/- 2%

RNA

3.2 ng/μl

1200 ng/μl

3.2 - 80 ng/μl: +/- 1.6 ng/μl >80 ng/μl: +/- 2%

Note Absorbance reported is normalized to a 1.0 cm (10.0 mm) pathlength for all measurements.

Protein Measurements Purified protein samples can be quantified on the NanoDrop Lite spectrophotometer. To measure the concentration of a protein sample, select the Protein application from the Home screen and then select the appropriate assay type (1A/cm = 1 mg/ml, IgG or BSA).

Making a Measurement 1. Select Protein from the Home screen. 2. Select the appropriate assay type: 1A/cm=1mg/ml, IgG, or BSA. 3. Following the on-screen instructions, establish a blank by pipetting 2 μl of the blanking buffer onto the bottom pedestal, lower arm and press Blank.

Thermo Scientific

NanoDrop Lite

9

NanoDrop Lite User Guide Protein Measurements

4. When measurement is complete, raise the arm and wipe the buffer from both the upper and lower pedestals using a dry laboratory wipe. 5. Confirm Blank by pipetting a fresh aliquot of blanking buffer onto the bottom pedestal, lower the arm and press Blank. 6. When measurement is complete, raise the arm and wipe the buffer both the upper and lower pedestals using a dry laboratory wipe. 7. Measure sample by pipetting 2 μl of sample onto the bottom pedestal, lower arm and press Measure. 8. Wipe the upper and lower pedestals using a dry laboratory wipe and the instrument is ready to measure the next sample. Note A fresh aliquot of sample should be used for each measurement. When working with protein samples it is recommended that a 2 μl sample volume be used to ensure that a liquid column is formed between the upper and lower pedestals. This is especially true for concentrated samples or samples that contain detergents. See “Sample Volume Requirements” on page 13.

Protein Measurement Screen Figure 8.

Sample measurement screen Application Sample number Absorbance Concentration Time & date sample and blank measurements were collected

Protein Calculations Proteins, unlike nucleic acids, exhibit considerable diversity. The Protein A280 application is indicated for purified proteins that contain Trp, Tyr residues or Cys-Cys disulphide bonds and exhibit absorbance at 280 nm. The Protein A280 application measures sample absorbance at 280 nm (A280) and calculates the concentration (mg/ml) using the selected extinction coefficient. The Protein A280 application does not require generation of a standard curve.

10

NanoDrop Lite

Thermo Scientific

NanoDrop Lite User Guide Protein Measurements

The NanoDrop Lite should be used to measure the concentration of purified protein samples. Direct protein concentration measurements assume a highly purified sample as all absorbance at 280 nm is included in the calculation of the protein concentration. Carryover of starting materials, purifying reagents, and cell material into the measured protein sample will result in an artificially high protein concentration. Protein concentration is calculated using the Beer-Lambert equation: c

= A/*l

where, c

= the protein concentration

A

= the sample absorbance



= the protein specific mass extinction coefficient

l

= the pathlength in cm

The protein specific concentration measurement options are: 1A/cm = 1 mg/ml: A general reference setting based on a 0.1% (1mg/ml) protein solution producing an Absorbance at 280 nm of 1.0A (where the pathlength is 10 mm or 1 cm). This is the default setting for the Protein application. IgG: Immunoglobulin G reference. Sample protein concentrations are calculated using the mass extinction coefficient of 13.7 at 280 nm for a 1% (10 mg/ml) IgG solution. BSA: Bovine Serum Albumin reference. Sample protein concentrations are calculated using the mass extinction coefficient of 6.7 at 280 nm for a 1% (10 mg/ml) BSA solution. Table 2. Protein Concentration Range Extinction Coefficient

Lower Detection Limit

Upper Detection Limit

Typical reproducibility (10 replicates, SD = mg/ml; CV=%)

1Abs=1 mg/ml

0.08 mg/ml

30 mg/ml

0.08 - 2 mg/ml: +/- 0.04 mg/ml >2 mg/ml: +/- 2%

BSA

0.12 mg/ml

45 mg/ml

0.12 - 3 mg/ml: +/-0.06 mg/ml >3 mg/ml: +/-2%

IgG

0.06 mg/ml

21 mg/ml

0.06 - 1.4 mg/ml:+/-0.03 mg/ml >1.4 mg/ml:+/-2%

Note Absorbance reported is normalized to a 1.0 cm (10.0 mm) pathlength for all measurements.

Thermo Scientific

NanoDrop Lite

11

NanoDrop Lite User Guide Transferring Data From Instrument to Computer

Transferring Data From Instrument to Computer The NanoDrop Lite automatically stores the last 500 measurements in the internal memory. Measurements include samples, blanks, and blank confirmations. A USB memory device can be used to transfer these measurements from the NanoDrop Lite to a computer for archival or further analysis. The internal software of the NanoDrop Lite does not support connecting the NanoDrop Lite to an external hard drive. Only USB memory devices (memory sticks) should be used to transfer data. These options appear when a USB device is inserted: Figure 9.

USB Operations

USB Operations

Function

Save Data

Saves all data currently in instrument’s memory to USB memory device.

Save Diagnostics

Appends diagnostic data to sample measurements and saves to USB memory device.

Save Cal. Check

Saves the last calibration check data to USB memory device.

The sample data is automatically saved on the instrument. To transfer data from the instrument to a USB memory device, insert the device and select Save Data from the USB Operations menu. This file can be transferred to a computer and opened in Microsoft Excel®. The Save Data option will only appear when a USB device is inserted. If a USB memory device is inserted, the Save option appears on the Home screen.

12

NanoDrop Lite

Thermo Scientific

NanoDrop Lite User Guide Helpful Information for Measuring Samples

Figure 10. Save option from Home screen

Use the Save option on the Home screen to return to the USB operations menu shown in Figure 9. NOTICE A maximum of 500 measurements will be saved in the instrument and are available to be transferred to a USB memory device at any time. Measurement #501 will replace #1.

Helpful Information for Measuring Samples Sample Volume Requirements Sample volume is important because it is essential that a proper liquid column is formed and that the path between the upper and lower pedestals is bridged with liquid sample which is held in place by surface tension. The dominant factor determining the surface tension of a droplet is the hydrogen bonding of the lattice of water molecules in solution. Generally, all solutes (including protein, DNA, RNA, buffer salts and detergents) can reduce the surface tension by interfering with the hydrogen bonding between water molecules. Although 1 μl volumes are usually sufficient for most sample measurements, increasing the sample size to 2 μl will ensure proper column formation for samples with reduced surface tension. This is particularly true when working with protein samples which may contain detergents. Such samples do not "bead" on the pedestal but tend to spread across the measurement surface. To ensure that a liquid column forms in the gap between the upper and lower pedestals, a 2 μl volume is indicated for such samples. Protein samples, especially those containing detergents, are subject to bubble formation. Extra care is required while pipetting onto the pedestal to ensure bubbles are not present into the light path of the spectrophotometer. Field experience indicates that the following volumes are sufficient to ensure reproducibility: Aqueous solutions of nucleic acids: 1 μl Aqueous solutions of purified protein: 2 μl

Thermo Scientific

NanoDrop Lite

13

NanoDrop Lite User Guide Helpful Information for Measuring Samples

It is best to use a precision pipettor (0-2 μl) with precision tips to ensure that sufficient sample (1-2 μl) is delivered. Lower precision pipettors (0-10 μl and larger) are not as good at delivering 1 μl volumes to the lower pedestal. If the user is unsure about the sample characteristics or pipettor accuracy, a 2 μl sample volume is recommended.

Sample Measurement Accuracy and Reproducibility Sample or aliquot heterogeneity and/or liquid column breakage may result in erroneous or non-reproducible results. Follow the recommendations below to ensure accurate and reproducible results: • Ensure the pedestal surfaces are clean. Although the second blank measurement is designed to prevent "false blanks" that are due to dried sample adhering to pedestals, a dirty pedestal (i.e., a pedestal with sample dried on it) may cause erroneous absorbance readings (even negative values) and signal saturation. It is good practice to clean the pedestal surfaces with deionized water prior to starting a measurement. Note Do not use a squirt or spray bottle to apply de-ionized water. • Use a 1.5-2 μl sample volume. Unexpected results can occur when the liquid sample column is not completely formed during a measurement. During the measurement, visually confirm that the liquid column is formed. Also, proteins and solutions containing surfactants are known to “un-condition” the pedestal surfaces so that the liquid column does not form. If this occurs, use the Thermo Scientific Pedestal Reconditioning compound (PR-1) to recondition the pedestals. Refer to “Reconditioning” on page 25 for more details. • Heat high molecular weight DNA samples to 55 °C and gently vortex before measurement. Due to the small volumes required by the NanoDrop Lite, it is important to ensure that the sample being measured is homogeneous. Field experience has shown that samples containing large molecules such as genomic or lambda DNA are particularly susceptible to heterogeneity. • Ensure that a fresh aliquot of blanking solution is used for the blank confirmation (the second blank) prior to making a sample measurement. • Confirm that blank and sample buffer are the same pH and ionic strength. Some buffer components absorb in the UV range, therefore, it is critical to blank the instrument with the same solution (buffer from the same bottle if possible) in which the sample is suspended. • Confirm that the sample is not too dilute or too concentrated. Analyzing samples at or near the detection limit will result in variable measurements. Refer to Table 1 and Table 2 for guidance on detection limits.

14

NanoDrop Lite

Thermo Scientific

NanoDrop Lite User Guide Helpful Information for Measuring Samples

• Confirm instrument is working within specifications with CF-1. CF-1 is a concentrated potassium dichromate calibration standard available from Thermo Fisher Scientific and its distributors. It is recommended that the calibration check procedure be performed every six months with a fresh vial of CF-1 to confirm that the instrument is performing within specifications.

Sample Homogeneity Sampling from heterogeneous solutions, particularly when using small volumes, may result in poor data reproducibility regardless of the technology being used to make the measurement. Genomic DNA, lambda DNA and viscous solutions of highly concentrated nucleic acids or proteins are common examples that require careful attention to ensure homogeneity before sampling. Proteins are subject to denaturation, precipitation, and aggregation and therefore also require special handling to ensure homogeneity before sampling.

Sample Carryover Wiping of the upper and lower pedestal with a clean, dry laboratory wipe is sufficient to eliminate carryover between samples differing in concentration by as much as three orders of magnitude.

A260/A280 Ratio Some researchers may encounter a consistent A260/A280 ratio change when switching from a standard cuvette spectrophotometer to the NanoDrop Lite. The three main causes for this are: Change in sample acidity - Small changes in solution pH will cause the A260/A280 ratio to vary1. Acidic solutions will under-represent the A260/A280 ratio by 0.2-0.3, while a basic solution will over-represent the ratio by 0.2-0.3. When comparing the NanoDrop Lite to other spectrophotometers, it is important to ensure that the pH of an undiluted sample measured on the NanoDrop Lite is at the same pH as the diluted sample measured on the second spectrophotometer. Wavelength Accuracy of the Spectrophotometers - Although the absorbance of a nucleic acid at 260 nm is generally on a plateau, the absorbance curve at 280 nm is quite steeply sloped. A slight shift in wavelength accuracy will have a large effect on A260/A280 ratios. For example, a + 1 nm shift in wavelength accuracy will result in a +0.2 change in the A260/A280 ratio. Since many spectrophotometers claim a 1 nm accuracy specification, it is possible to see as much as a 0.4 difference in the A260/A280 ratio when measuring the same nucleic acid sample on two spectrophotometers that are both within wavelength accuracy specification.

1 William W. Wilfinger, Karol Mackey, and Piotr Chomczynski, Effect of pH and Ionic Strength on the

Spectrophotometric Assessment of Nucleic Acid Purity: BioTechniques 22:474-481 (March 1997)

Thermo Scientific

NanoDrop Lite

15

NanoDrop Lite User Guide Using NanoDrop Lite With Optional Printer

The difference in the A260/A280 ratio is important when comparing measurements taken on the NanoDrop Lite to measurements made on other spectrophotometers. The NanoDrop Lite uses LED sources centered at 260 and 280 nm. The selection of quality LEDs and narrow band filters combine to ensure the highest wavelength accuracy. Therefore, the NanoDrop Lite has no moving parts and wavelength calibration is not required. Nucleotide Mix in Your Sample - The five nucleotides that comprise DNA and RNA exhibit widely varying A260/A280 ratios2. The following represent the A260/A280 ratios estimated for each nucleotide if measured independently: Adenine: 4.50 Cytosine:1.51 Guanine: 1.15 Thymine:1.47 Uracil: 4.00 The resultant A260/A280 ratio for the nucleic acid being studied will be approximately equal to the weighted average of the A260/A280 ratios for the four nucleotides present. It is important to note that the generally accepted ratios of 1.8 and 2.0 for DNA and RNA are “rules of thumb.” The actual ratio will depend on the composition of the nucleic acid. Note RNA will typically have a higher A260/A280 ratio due to the higher ratio of Uracil compared to that of Thymine.

Effect of Evaporation and Solvent Usage A fresh aliquot of sample should be used for each measurement. Evaporation of the sample during the measurement cycle usually has a minimal effect on absorbance readings and may result in a 1-2% increase in sample concentration. However, repeated measurements on the same sample aliquot will result in increasing concentrations and/or column breakage. Highly volatile solvents, such as hexane, will likely result in evaporation before the measurement can be completed. Less volatile solvents such as DMSO can be used successfully.

Using NanoDrop Lite With Optional Printer  To connect NanoDrop Lite to printer

1. Ensure power supply is disconnected from both the NanoDrop™ Lite and the printer. 2. Firmly push the instrument onto the printer base as shown. The instrument will snap into place when properly docked. The NanoDrop Lite is now powered through the printer.

2 Leninger, A. L. Biochemistry, 2nd ed., Worth Publishers, New York, 1975

16

NanoDrop Lite

Thermo Scientific