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FAQ - Picodrop™ µl Spectrophotometer


Questions

Answers

Q1

What is the sample concentration range for In-Direct protein measurement?

   A1

In-direct measurement depends on the assay, here are some examples:


Regular Bradford sample range 100-500 µg/ml: ± 25 µg/ml
Mini Bradford sample range 15-50 µg/ml: ± 4 µg/ml
Lowry sample range 0.2-1.0 mg/ml ± 0.01 mg/ml

Q2

Can there be liquid on the outside of the pipet tip?

   A2 For the most consistent results please make sure there is no additional liquid stuck to the outside of the tip (even a small film can increase variability by 10% or more). We recommend pipetting from the very top of the meniscus, or wiping the outside of the tip with a clean wipe.
Q3

What is the life of the flash lamp?

   A3 The lamp only illuminates when reading a sample. The life of the lamp is measured in flashes and is given as 1 x10^9. We use up 25 flashes per sample. This gives a theoretical 40 million samples per lamp which means at average user rates, a lamp will last for at least 7 years.
Q4

What is the purpose of the 'Other' box on the nucleic acid screen

   A4 The calculation of nucleic acid concentration uses a specific extinction coefficient (amout of UV light absorbed per mole) which is dependent on the molecule being measured, for example dsDNA has an Ext.Coefficient of 50 and ssDNA is 33, RNA is 40 ... the option 'Other' allows the user to input a different value which may be required for nucleic acids which do not follow the standard molecular structure.
Q5

Is there any cross contamination between samples?

   A5 The bottom of the tip is in the air and not touching anything during measurement so no contamination is possible. it is, however, a good procedure to wipe the outside of the tip gently with a tissue before placing in the pipette holder. This is of particular importance when measuring viscous protein solutions. If the lense does get dirty it is very easy to clean (follow instructions in manual)
Q6

Is it possible for the tip to bend in the pipette holder?

   A6 The tip is held straight in the sample block it is not possible to bend.
Q7

Is it possible to blank on air?

   A7 It is not possible to blank on air as air scatters the light. Water or sample buffer should always be used.
Q8

What is the lowest limit for DNA/RNA?

   A8 Picodrop has a lower limit of approx 3-5ng/µl depending on sample quality. With typical quality samples we would recommend not measuring below 5ng/µl. As with competitive Spectrophotometers such as nanodrop the tolerance at these low concentrations is approx. +/- 2ng/µl.
Q9

Can you blank with the same tip you use to measure sample in?

   A9 For very sensitive readings (at the lower end of the range), we recommend blanking in the same tip that you read in. That is, draw up a 2.5 ul blank in the tip, dispense the blank, and then draw 2.5 ul of your sample in the same tip. The tips are made of ultra-hydrophobic resin, so a negligible amount of blank solution should remain in the tip.
Q10

Do you offer an extended warranty or maintenance contract?

   A10 The Picodrop spectrophotometer comes with a standard 1 year warranty that covers parts, labor and shipping. We offer additional 1 year extended warranties under catalog number PICOWAR01. The unique “in tip” design for the Picodrop does not necessitate periodic recalibration, so there is no need for maintenance contracts.
Q11

What size cuvettes does the optional cuvette adapter accept?

   A11 Any standard cuvette with a 15mm read window.
Q12

What is the lowest volume that can be used with disposable cuvettes?

   A12 Using an Ultramicro cuvette with a 15mm read height, volumes as low as 70 ul can be used.
Q13
 In Admin settings what is 'samples before re-blanking'?   A13 The ‘samples before re-blanking’ is simply the number of measurements possible before the automated message, instructing user to re-blank, is displayed. This is set to 10 by default. We do not recommend increasing this as over time the lamp will ‘drift’ and environmental conditions will change so it is advisable to re-blank regularly at least every 10 measurements.
Q14

In admin settings, what is 'linearity' and 'outlier removal'?

   A14 When logging in as ‘admin’ it is possible to change the sensitivity of blanking. This means how much variation from zero is acceptable. The default is 5% so this is why ‘linearity’ and ‘outlier removal’ are set to 1.05. If the readings during the blanking stop being linear over the range or there are individual readings outside the 5% limit then the blanking step will be rejected and the user asked to re-blank. Changing these values is not recommended although for some non-homogenous samples (e.g.cell cultures) it may be advantageous to reduce the sensitivity a little to say 1.07.