Beyond Simple Colorimetry With MeasureNet

by Dr. Jerry DeMenna

Sacred Heart University “Gypsy” Professor & MeasureNet Technology Curriculum Specialist

A typical Colorimeter is usually a simple, Single-Beam optical system to measure “color” in the VISIBLE Spectrum of light and provide ABSORBANCE data at a single wavelength. These systems can cost $1,000 or more for stand-alone Colorimeters that merely provide simple ABS data… unless you consider the MeasureNet Model MDBC-138 true Double-Beam, Multi-Functional “Colorimeter” based on a unique set of LEDs (Light-Emitting Diodes)... for under $500! The MeasureNet “Colorimeter” is actually FOUR (4) instruments in ONE (1) compact and rugged box… and works as a Colorimeter (to make Beer’s Law Curves for VISIBLE Wavelengths), a UV Fluorometer (to demonstrate Fluorescence & Quenching in certain Organic molecules), a Turbidometer (to measure the Turbidity of particulate & colloidal suspensions) and a Phosphorimeter (to analyze the Phosphorescence [“glow”] of specific materials).

#1) BEER’S LAW ABSORBANCE & KINETIC SPECTROSCOPY =
This unit can be used as a “simple” Colorimeter to demonstrate Beer’s Law using three (3) high-output VISIBLE Light LEDs at 472nm (BLUE), 525nm (GREEN) and 630nm (RED); which cover over 75% of the classic General Chemistry and Analytical Chemistry Laboratory experiments that teach Spectrophotometric measurements. The Wavelength coverage of these LEDs allows highly accurate relative measurement of almost all the ROYGBIV Colors. The disposable & unbreakable 10mm pathlength, near-UV Plastic Cuvettes included with the “Colorimeter” can be used from ~300nm (in the near-UV) to over 1000nm (in the near-IR) for Analytical measurements… and come with Sealing Caps to preserve prepared solutions for future tests. Some of the popular Laboratory experiments defined in MeasureNet’s proprietary FUN-SCIence™ Laboratory Programs and its upcoming “Chem-Lab Library” that provide an excellent framework to create or supplement YOUR OWN Academic Lab curriculum program for Gen Chem, Analytical or Student Research are:

-=> Red / Blue / Green Colorimetric ABS Data for Beer’s Law plots:
• Test for Mineral IRON in your Daily “Eats”… check your Cereals, Breads and special Treats!
• Unsaturated FATS can be easily seen… just get a purple Color using some IODINE!
• Evaluation of Nutritional Food Proteins… React it to get a “BLUE” and see what can be seen!
• Consistency of M&M and Skittles Candy Colors: Is the "blue" true blue or “faux” to you!
• Changing “Colors” of some pH Dyes… [H+] makes them look *new* to our eyes!
• General Colorimetric Assay… for ANION (X, PO4, SO4, NO3, NO2, etc) saves the day!

Unlike most other popular Spectrophotometers… even those costing over $5,000… the MDBC-138 is a TRUE Double-Beam Optical System… and provides a Reference Cell to “blank” out the Reagents used to create a very stable ABS reading for several Organic Reactions. Data from these Labs can be used to calculate Rate Constants, Equilibrium Factors and Reaction conditions (for Thermal, Ionic and Electrochemical variables). This is a MUST for making accurate Kinetic Experiment tests. A few of them from our “Library” include:

-=> Dual-Beam ABS Data for Kinetic Measurements:
• The Iodine Test for Starches is GREAT… just Hydrolyze with Amylaze to get a Kinetic Rate!
• Perform REDOX “Clock” Reactions in School… and show Students that Chemistry is Cool!
• pH-based Hydrolysis of p-nitrophenylacetate Ester… try it out in your Lab this Semester!

#2) QUANTUM FLUORESCENCE & KINETIC SPECTROMETRY =
Many types of Organic molecules will exhibit a VISIBLE Fluorescent “Emission” when exposed to high energy ULTRA-VIOLET light to create the “Excitation”. This spectro-chemical response is due to the interaction of the energetic UV photons with the loosely-held pi-electrons and other “labile” functional groups in Aromatic, Olefinic, Alkaloidal, Xanthinoid and poly-Cyclic compounds… and there are many important applications for this little-understood, rarely-taught, under-utilized Technology. Using the newest in LED technology, the MeasureNet “Colorimeter” has several “Excitation” sources available… with the 370nm UV-LED providing the most useful range of responses for relative Fluorescence analyses (since it is very close to the classic 366nm Long-Wavelength UV from a Mercury Lamp)… although several alternate User-Defined Wavelengths are available from a growing list of LED sources, please inquire for more information!

When used in the “Fluorometer” mode, the Detector is situated at a 90° angle from the UV LED Source, to generate TRUE Fluorescent “Emission” data without potential interference from the “Excitation” wavelength. Laboratory exercises for both Qualitative comparisons and Quantitative analysis of many materials can be found in the MeasureNet FUN-SCIencetm Labs and soon-to-be introduced “Chem-Lab Library” to cover Organic chemistry, Analytical Sciences, Biology/Biochemistry, Environmental and Nutritional Science programs, as highlighted here:

-=> UV-LED Fluorometry for Single-range EMISSION Values:
• “Zap” UV against Chlorophyll from things that Grow… and see what makes it eerily Glow!
• The Highlights of Highlighting Markers: How bright is bright? is it LABELLED right?
• Evaluation of Cigarette Second-Hand Smoke: Nicotine for the Masses in your Breathing Gases?
• Analysis of Alkaloid Material: Don't do drugs!....., but do drug analysis! It’s fine with Quinine!
• Measure Amino Acids in “Energy Drinks”… Are their labels Accurate or does their Data Stink!?
• Check Ground-Water “Plumes” with Fluoresceine… Water-Table extracts will also be green!

#3) TURBIDIMETRIC / NEPHELOMETRIC LIGHT-SCATTERING SPECTROMETRY =

The “Colorimeter” can also be used in the “Turbidometer” mode… or more precisely, as a “Nephelometer”, since Nephelometry uses a Near-IR LED (@ 880nm) to measure the SCATTERED light at a 90° angle from the Light Source, as it is done on the MeasureNet unit. Tests can be made on sample Solutions that have existing particulate suspensions… or a reaction can be made to produce a range of particulates for relative and direct measurements. Originally used for Clinical Chemistry applications, Turbidometry / Nephelometry can be applied to a wide range of curriculum subjects… from Organic Synthesis & Analytical Chemistry to Environmental & Biochemistry Labs. Some of these unique and educational Labs are shown here:

-=> Turbidity (“Nephelometry”) for Kinetic & Relative Comparison at Single values:
• Environmental Testing of “Settleable Solids” for River / Stream & Estuarial Waters
• Reducing Sugars by Benedict’s Test... great for Diabetics, Atkins-Diets and all the rest!
• Collect some of the DUST from your “Air”… is it okay to breathe or is something there?
• Rate of Reaction of Silver Ion + Chloride Ion to form AgCl precipitate… Kool Kinetics!
• The classic Princeton “Nassau Clock” Reaction… makes for a great teaching Lab attraction!
• Measurement of Yeast Growth in Beer… is it fermenting slow or in high-gear?

#4) LUMINESCENCE/PHOSPHORIMETRY =

Last, but certainly not least, is the use of the MeasureNet “Colorimeter” as a “Phosphorimeter”… also called a “Luminometer”… which, unfortunately, is one of the more versatile Analytical “tools” not readily found in most Laboratories. A “Phosphorecent” response can be induced by UV-fluorescence AFTER the Light souce is removed… or it can be caused by a Chemical Reaction that causes the “Emission” of VISIBLE Light photons. The proprietary design of the “Colorimeter” Optical layout allows the Analyst to get the desired response from their Sample material… again using the same high-sensitivity Optics.

Bio-Luminescence in Fish and Algae, the Luciferin/Luciferase Reaction in Fireflies, the UV-Blocking capacity of SPF Lotions & Sunglasses, the ‘controllablel” Oxidation of Luminol Light-Sticks, the newly developed Photo-Luminescent additives for Plastics used in skyscraper Building and more can be beginning Labs you can use directly as-is, or modify for your own specific curriculum… as outlined for your review:

-=> Luminescence (“Phosphorescence”) for Kinetic & Relative Comparison valuess:
• Check out these Glow-in-the-Dark Plastics… some are made of material quite Fantastic!
• Bio-Luminescent Algae and Bacteria are found in “Healthy” Waters… See anything “Fishy”?
• P-AminoBenzoic Acid is the SPF of “Old”… using Luminscence its tale can be told!
• “UV” Light causes “Glow-in-the-Dark” Photon Motions… “Block” it with some SPF Lotion!
• “Luciferase” is the enzyme in the Fire-Fly… catch a few & give this Phosphorimetry Lab a try!
• The Luminol “Light Stick” reaction… uses Organic Oxidation to set those Photons in action!

Many current MeasureNet Users that have the MDBC-138 “Colorimeter”… and potential Customers, too… may not be aware of the tremendous versatility of this Spectral device… and many potential *new* Customers in Academia can save a significant amount of Time, Money and Resources by implementing this little Hidden Treasure Trove of Technology for their Teaching Laboratories and Educational Curricula. Designed for simple, direct Plug-n-Play capability with any MeasureNet Workstation… it requires no external Power-Supply (running off the internal electronics) and is available for IMMEDIATE use, since it requires NO warm-up time! Please call or write us for additional details on this Powerhouse of Spectroscopic FUN and we’ll be glad to work with you on YOUR specific needs to take the best advantage of these Technologies!

Stay tuned... More to come!!

Thanks for your Time and Attention… and Happy Learning & Teaching!

Dr. Jerry

MeasureNet Technology Ltd. manufactures patented, network-based data acquisition interfaces for science teaching laboratories. It is a spin-off of the University of Cincinnati's Department of Chemistry and is headquartered in Cincinnati, Ohio. Measurenet's award-winning, PC-reducing design helps reduce laboratory maintenance and operational costs while giving students access to high quality shared UV-vis spectroscopy, gas chromatograph and HPLC connectivity, and an array of innovative probeware. Its acclaimed intuitive design provides improved transparency to enable better science-focused learning. Winner of the Ohio Governor's Award For Excellence in Energy Efficiency, MeasureNet networks are found in universities, community colleges, high schools, and vocational training centers across the United States and around the world.

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tel. toll-free: 866-396-6765

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> University of Central Missouri Department of Chemistry and Physics