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TUTORIAL OMICS tomatically selected from a drop-down menu in onboard software of the Libra S60 dual beam spectrophotometer and five recorded measurements were averaged together. Samples were then progressively diluted and the measurements repeated for all sub- sequent concentrations. The measured con- centration was plotted against the expected value, along with the percent difference be- tween the measured and expected values. Repeatability was tested by measuring a single sample multiple times before calculating the peak and RMS variation between measure- ments. The BioDrop Cuvette was removed from the instrument between each run. The detection limit was also tested by performing a series of measurements on ultra-pure water and recording the reported concentrations. When carrying out such investigations, con- tamination and cleanliness were of paramount importance, especially considering the small size of the samples being used. Care was taken during testing to ensure no bubbles or dust particles were caught in the pipetted volumes, while the BioDrop Cuvette's large sample win- dow allowed the user to see any physical con- tamination. Sample carry over was assessed by alternating between samples of ultra-pure water and concentrated DNA, wiping with a lint-free cloth after each measurement. Results Figures 2 and 3 show the measured con- centration against dilution factor. A linear least squares fit shows that both pathlength Cuvettes exhibit excellent linearity. A cor- relation of 0.9998 and 0.9997 was shown with the 0.5 mm and 0.125 mm pathlength BioDrop Cuvettes respectively, showing sta- tistically accurate results with all measured concentrations. A detection limit of 1.2 ng/µL was mea- sured with the BioDrop Cuvette 500, while a detection limit of 7.1 ng/µL was measured with the BioDrop Cuvette 125. These were similar to the carry over testing results, in- dicating that contamination between succes- sive samples is negligible when the user fol- lowed a simple cleaning protocol. Finally, reproducibility tests showed a peak to peak value of 1.0 and a standard de- viation of 0.5 for a 100 ng/µL concentration, followed by a peak to peak of 4.1 and a SD of 2.4 for a 1,000 ng/µL concentration when using the BioDrop Cuvette 500. When the same concentrations were measured with the BioDrop Cuvette 125, peak to peaks of 4.6 and 6.6 and standard deviations of 2.3 and 3.2 were measured for 100 ng/µL and 1,000 ng/µL respectively. As well as demonstrating the consistency of results, this suggested that identical posi- tioning of the cuvette does not significantly impact measurement results, as the BioDrop Cuvette was removed and replaced each Arjun Dhanoya (Arjun.Dhanoya@ biochrom.co.uk) is the life science product specialist at BioDrop. Web: www.biodrop.co.uk. Genetic Engineering & Biotechnology News | genengnews.com | October 1, 2012 | 33 time. There was no need for adapters with lenses or screw adjustments to ensure the light beam was correctly coupled with the device when it was reinserted. Conclusion The BioDrop Cuvette has proven itself able to overcome some of the most common disadvantages of conventional low volume spectroscopy techniques, providing a simple and effective way to quantify microliter vol- umes in almost any UV/Visible spectropho- tometer. The tests of accuracy, precision and linearity of the BioDrop Cuvette 500 and the BioDrop Cuvette 125 confirmed high-qual- ity measurement performance over a wide dynamic range when used with a Biochrom Libra S60 spectrophotometer. Results were reliable, accurate, and repeat- able, and experimental procedure was notice- ably simplified in comparison to other com- mon techniques. The BioDrop Cuvette ap- pears to be ideally suited for low volume work in modern life science laboratories. When it comes to nuclear receptor screening, who you know can determine what you know. With INDIGO's nuclear receptor experts at your service, you get results you can be confident in, every time. With our convenient lab-in-a-box assay kits, you can bring the power of INDIGO into your lab to perform quick, simple and reliable in-house discovery and toxicology screening. If you'd rather put our experts to the test, send us your compounds and we'll screen them in our lab. Either way, when you need fast, accurate results, trust the nuclear receptor experts. KNOW INDIGO. BRUCE A. SHERF, Ph.D. CHIEF TECHNOLOGY OFFICER JACK VANDEN HEUVEL, Ph.D. FOUNDER, CHIEF SCIENTIFIC OFFICER www.INDIGOBiosciences.com 814.234.1919