Owner: Chromatography URL:http://www.justchromatography.com/ Join Date: Sat, 28 Apr 2007 13:58:41 -0500 Rating:0 Site Description: Chromatography and Analytical Chemistry - from history and basic principles to the latest research news and concepts such as Nano HPLC and "Lab on a Chip" concepts. Site statistics:Click here
What is the response factor in chromatography? 2007-06-21 07:10:56 “What is the response factor
in chromatography?” is a question on Yahoo Answers.
So far there has been two answers:
1) A wordy and a bit confusing text book reply tailored more towards Gas Chromatography.
Response Factor
The size of a spectral peak is proportional to the amount of the substance that reaches the detector in the GC instrument. No detector responds equally to different compounds. Results using one detector will probably differ from results obtained using another detector. Therefore, comparing analytical results to tabulated experimental data using a different detector does not provide a reliable identification of the specimen.
A “response factor” must be calculated for each substance with a particular detector. A response factor is obtained experimentally by analyzing a known quantity of the substance into the GC instrument and measuring the area of the relevant peak. The experimental conditions (temperature, pressure, carrier gas flow rate) must
Columns in Nano LC 2007-06-27 15:13:17 As I mentioned in the last post from this series, capillary columns of 10–100 μm inner diameter are commonly used in nano-liquid chromatography setups. They are typically made either from fused silica or PEEK materials currently found in your everyday Gas Chromatography or HPLC, respectively.
There are three basic types of capillary columns used in nano-liquid chromatography: packed, monolithic, and open tubular.
Packed Capillary Column
Packed columns are made by “stuffing” the capillary with silica-modified particles of 3–5 μm. Though recently, particles of 1.5–1.8 μm were successfully employed in ultra performance LC (UPLC).
Such a small particle size provides nano-liquid chromatography systems with higher efficiency, resolution, selectivity, and shorter analysis time; however, it does increase the backpressure.
Due to the high cost and limited types of stationary phases available, many research labs pack the columns “in-house”. But it is a difficult
Carbon Nanoscrolls to Store Hydrogen 2007-06-24 15:02:34 As our planet is running out of petroleum resources, a new energy source must be found. Hydrogen is regarded as an ideal alternative to fossil fuel because of its abundance in environment, renewability, and zero emission. However, the most challenging and important aspect for the successful transition to a hydrogen economy is the problem of hydrogen storage.
Two-thirds of U.S. oil consumption is used to meet transportation energy needs, so unless there is a way to safely and efficiently store hydrogen on board a vehicle, it will be impossible to make a step forward to a hydrogen based economy.
Hydrogen Storage Methods
Presently there are three major directions in research and development of hydrogen storage systems:
Gaseous Hydrogen - storing hydrogen as a gas in tanks under high pressure. Recently 10,000-psi tanks made of lightweight carbon-fiber–reinforced composites have been demonstrated and certified; however, the energy content of hydrogen at even at 10,000 psi is only 1/8th Read more:Carbon
, Store
Cocaine Pollution 2007-07-02 15:10:22 Cocaine
is presently the most abused substance in Americas; however, the stimulant is gaining new advocates at an alarming rate in western Europe as well.
In 2005, a group of researches from Italy analyzed water samples from the Po River in northern Italy for the presence of cocaine and its main urinary metabolite - benzoylecgonine (BE)[1]. They took samples each day for four different days and extracted cocaine and BE by solid-phase extraction followed by analysis on LC - MS/MS with electrospray ionization.
Though the concentrations of benzoylecgonine and cocaine in the river were small - 25 and 1.2 ng/L, it is equivalent to 4 kg of cocaine per day that flows down the river or 40,000 (!) doses per day based on a typical cocaine dose.
This year, Italian researches form the Institute for Atmospheric Pollution
(IAP) theorized that if cocaine is in water, it could also be present in the air[2]. For example, cocaine seizures by the authorities and snorting can both release cocaine particl
Nanogenerators Powered By Heartbeat 2007-07-07 12:07:53
Scientists from Georgian Institute of Technology created a prototype nanogenerator that can generate electricity inside a human body.
Tiny little devices traveling in our bloodstream while performing complete blood analysis and monitoring our well-being is the future of implantable biosensors. However, these nanorobots will need to be self-powered and there are two ways for achieving it - either to use a battery or to harvest energy from the environment.
Generating electricity “on-board” is a very attractive option for in vivo medical application because biological systems provide a great medium for converting chemical, thermal, or mechanical energy to electricity ensuring a lifetime operation.
Zhong Lin Wang and colleagues have developed a DC (direct-current) nanogenerator that converts mechanical energy into electricity. The basic principle is to use piezoelectric and semiconducting coupled nanowires (NWs), such as zinc oxide (ZnO). The nanogenerator used in the experi Read more:Heartbeat
High Reactivity at Very Low Temperatures 2007-07-05 13:00:00 New research examines a class of reactions between neutral free radicals and neutral molecules that, unlike most reactions, happen rapidly at very low temperatures.
Chemical reactions generally accelerate when temperature increase. However, in today’s issue of Science Magazine [1] a research group from France revealed a class of gas-phase reaction between oxygen atoms and alkenes that just do the opposite - the rate coefficients increase as the temperature is lowered.
Reactions of this sort may be taking place in interstellar clouds, which are difficult to study directly. Hassan Sabbah and colleagues have performed rate measurements between oxygen atoms and ethene, propene, 1-butene, cis-, trans-, and iso- butene over a range of temperatures from 20 to 300 Kelvin. Then they modeled the unusually rapid low-temperature rates, providing a theoretical framework for predicting reaction rates in systems that may be useful for understanding the chemistry of interstellar clouds.
1. &ldq
Asparagusic Acid, Anyone? 2007-07-10 13:22:57 Thank God for Greg’s post “Odeur d’Asperge” over at Carbon Tet! The mystery is solved, and I thought my kidneys were failing and I would have to spend the rest of my life on dialysis.
This spring I had become an avid admirer of the young asparagus shoots. And practically everyday for breakfast I had steamed or, sometimes, boiled organic asparagus served with cold pressed flaxseed oil and a little bit of soy sauce.
The taste was incredible, and I could never get enough of it. I even “promoted” asparagus to my second most favorite vegetable (after the fresh green peas, of course) but then came the smell…
It took me a few days to confirm the pattern:
asparagus for breakfast –> 15 - 20 min later –> a pungent odor of rotten cabbage in urine.
I immediately assumed that there is something wrong with my metabolism because when I questioned my friends they had no clue what I was talking about it. None one them smelled anything unus Read more:Anyone
Polymer Solar Cells Build for Two 2007-07-12 13:00:00
Researchers have developed a new method for producing tandem solar cells, in which two solar cells working together to use a wider range of the solar spectrum.
The physical properties of the semiconductor materials in each cell allow one to absorb light at longer wavelengths and the other to absorb light at shorter wavelengths. Researchers have made tandem solar cells before, but the vapor-deposition methods used to produce the multilayer structure have made the cells relatively expensive.
Jin Young Kim and colleagues now describe a cheaper method for making a tandem semiconducting polymer cell, in which all of the layers, including the electrode connecting the two units, are processed from solution. They used bulk heterojunction materials made from semiconducting polymers and fullerene derivatives.
The cell’s efficiency exceeds 6 percent at illumination of 200 milliwatts per cm2, which is quite good for cells produced via an all-solution method.
Reference: “Efficient Tandem Read more:Polymer
, Solar
, Build
Unanswered Questions 2007-07-16 10:41:26 Today I studied my blog’s statistics to see what keywords people use to search in Google and Yahoo! to get to the pages of my site.
Here is what I found based on the last 60 days of statistics:
People used 1966 various search terms
The top 20 keywords are:
Top 20
Term
Perc
chromatography
20.04%
witricity
3.76%
response factor
3.15%
wireless power transfer via strongly coupled magnetic resonances
1.63%
response factor in hplc
0.92%
history of chromatography
0.76%
wi-tricity
0.61%
recent application pharmaceutical of hplc
0.56%
conrad zhang
0.51%
eluotropic series
0.51%
efficient tandem polymer solar cells fabricated by all-solution processing
0.51%
hplc for pharmaceutical scientists
0.51%
rocky mountain spotted fever
0.51%
chromatography in bio chemistry
0.41%
nano chromatography
0.41%
resolution gas chromatography
0.41%
hydroxymethyl
Motor Proteins in Nanotechnology 2007-07-19 13:00:00
The biological cell is basically a miniature factory, which contains a large collection of dedicated protein machines. In a Review, Martin van den Heuvel and Cees Dekker look at recent progress in using some of these proteins to move, manipulate or power artificial, nanoscale devices.
(more…)
nano, nanogenerator, nanoscale, protein Read more:Motor
, Nanotechnology
The Little Botanists 2007-07-18 19:24:03 135th BirthdayHappy Birthday Professor Tsvet!Chromatogram on the ceilingColorgramFrom Switzerland to RussiaThe Little Botanists I am continuing the series dedicated to the chromatography’s founder Mikhail Tsvet. So, in 1897 he moves to Russia from Switzerland, and here is his first impression of Russia:
“…during the first six months that I have been in Russia, in vain, I have been trying to force myself to feel that I have a Russian heart beating in my chest! I traveled throughout Russia. I visited Moscow, the holly city, and my eyes and ears were widely opened… Nothing moved, nothing responded in me. In my homeland I felt like a foreigner. And this feeling deeply and desperately is weighing on my mind… Now I regret that I left Europe…”
(more…)
tsvet Previous in series
Columns for Gas Chromatography: Performance and Selection 2007-07-22 20:07:37
Choosing the right column is key in Gas Chromatography. “Columns for Gas Chromatography: Performance
and Selection” is a new hands-on reference for scientists and technicians working with packed column and capillary column gas chromatography.
The authors Eugene F. Barry (University of Massachusetts Lowell) and Robert L. Grob (Villanova University) discuss the development, performance, selection, and technology of columns for gas chromatography and include a handy list of packed column separations and guidelines for column selection in Appendices A and B. A subject index completes the book.
Book Description
Gas Chromatography (GC) is the most widely used method for separating and analyzing a wide variety of organic compounds and gases. There have been many recent advancements in both packed column and capillary column GC. With numerous options and considerations, selecting the right column can be complicated. This resource provides essential guidance for scientists and tec
Fishy Chromatography 2007-07-25 13:01:07
Folks from India extracted 99.6% pure eicosapentaenoic acid (EPA) using silver ion (argentation) column chromatography from hydrolyzed sardine oil[1].
EPA and DHA (docosahexaenoic acid) are the two main long-chain polyunsaturated fatty acids, also frequently referred to as “omega-3″. These lipids are primarily found in oily fish and shellfish. Some researches theorized that the consumption of the aquatic creatures and, hence, DHA/EPA is a key to the brain development of our prehistoric ancestors some 150,000 years ago[2]. Omega-3s also have been found to reduce the risk of heart disease and stroke.
Chakraborty and Raj concentrated EPA from chemically hydrolyzed sardine oil using urea fractionation with methanol at different temperatures and urea/lipids ratios followed by argentation neutral alumina column chromatography. The urea-fatty acid complexes were analyzed by gas-liquid chromatography and gas chromatography-mass spectroscopy that revealed the highest EPA concentra Read more:Fishy
“Fast” HPLC better than UHPLC 2007-07-31 01:25:35 Research scientists from Schering-Plough Research Institute developed a rapid high-performance liquid chromatography (HPLC) technique that allows for efficient separation and analysis of pharmaceutical compounds.
The method uses a short column packed with 2.7μm “fused-core” silica particles that are made by fusing a 0.5μm layer of porous silica onto a solid silica particle[1]. These unique particles enable very rapid chromatographic separation at a relatively low backpressure.
Ultra-high-pressure liquid chromatography (UHPLC) is another chromatographic technique that allows the system to handle the high backpressure resulting from the stationary phase with sub-2μm particles. UHPLC offers advantages in chromatographic resolution, speed, and sensitivity over conventional HPLC systems.
(more…)
HPLC, UHPLC Read more:better
Nano LC Sensitivity 2007-08-05 16:34:49 Nano Liquid ChromatographyNano Liquid Chromatography - ReloadedDefinition of Nano Liquid ChromatographyColumns in Nano LCNano LC Sensitivity
In theory, the analyte sensitivity increases on decreasing the column inner diameter; however, because of the very low sample volumes injected - 20-60 nL, nano liquid chromatography cannot be considered as an analytical method of high sensitivity.
There are several research studies that focused on the improvement of sensitivity by using techniques such as on-column focusing[1] and 2-D separation[2].
1. “Trace Level Determination of Organophosphorus Pesticides in Water with the New Direct-Electron Ionization LC/MS Interface”, Achille Cappiello et al., Analytical Chemistry, 2002 vol. 74 pp. 3547-54
2. “Fully automated micro- and nanoscale one- or two-dimensional high-performance liquid chromatography system for liquid chromatography-mass spectrometry compatible with non-volatile salts for ion exchange chromatography” by Masud
Heat Flow through Hydrocarbon Chains 2007-08-09 13:00:00 Scientists have measured heat conduction through a monolayer of hydrocarbon chains using a novel technique. Researchers understand heat transfer on the scales of individual molecules and in solids, but there is still much to learn about the physics of heat transfer in just a few molecules that will be used in nanometer-scale electronics.
Zhaohui Wang and coauthors used a laser pulse to heat a gold substrate onto which a self-assembled monolayer of long-chain hydrocarbon molecules had been formed. The researchers used coherent vibrational spectroscopy to measure the heat conduction as it traveled through the chain of molecules via distinct vibrations. The heat flowed through the chains at about 1 kilometer per second in agreement with theoretical predictions.
References:
“Ultrafast Flash Thermal Conductance of Molecular Chains
,” by Z. Wang, J.A. et al., Science, 317, pp 787-90, DOI:10.1126/science.1145220
“Molecules Take the Heat,” by A. Nitzan, Science, 317 pp.
Forensic Application of Gas Chromatography 2007-08-24 14:02:04
These days gas chromatography (GC) is one of the primary analytical techniques used in every forensic laboratory. GC is widely used by forensic scientists - from analysis of body fluids for the presence of illegal substances, to testing of fiber and blood from a crime scene, and to detect residue from explosives. Yet scientists from Ohio University explored another application of gas chromatography with differential mobility spectrometry as a low cost, onsite detection method for ignitable liquids.
(more…)
explosives, forensic, GC/MS Read more:Forensic
, Application
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