Table of Contents

Winter Quarterly Meeting Review

Pat Sackett

A small but highly engaged group met on the 24th of January to hear Dr. Ulrich Bernier speak about a subject near and dear to the hearts of all true Minnesotans: Mosquitoes, and how to thwart them.

Using a combination of novel sampling techniques, GC/MS, and plucky volunteers, Dr. Bernier and his colleagues at the USDA-ARS center for Medical, Agricultural and Veterinary Entomology in Gainesville, FL are beginning to make inroads towards rational mosquito control. He described the division of chemical compounds into 3 groups: attractants ("Dinner is served"), repellants ("Don’t go there") and inhibitors ("Nothing to see here; move along") and how synergies are achieved when blends from one group are offered to mosquitoes. With at least 277 compounds observed in human skin emanations, there are plenty of blends to be tested.

Skin emanations are collected using glass beads rubbed for an extended period between a subject’s hands, and grab bags to isolate low molecular weight volatiles which generally vaporize from bead surfaces. Further complicating the search for target compounds, the pattern of skin emanations changes from day to day, and may be affected by the use of such things as after-shave, hair treatments, and alcohol, and the fact that some compounds can remain on the skin for up to 2 weeks.

If the goal is to attract mosquitoes, a blend of L-lactic acid, acetone, and dimethyldisulfide is highly effective. Contrary to belief, limburger cheese is not a good attractant (cheddar and blue cheeses are much better) and CO2 isn’t particularly effective. Attractants can have wide variation in effectiveness depending on the species of mosquito, while inhibitors appear to be universal and species-independent.

The latest work presented involved a combination of inhibitors close to human subjects coupled with attractants placed away from the subject, resulting in over 90% of the mosquitoes avoiding the human and heading toward the attractant. Two patent applications have been submitted, and may offer some hope of relief to those involuntarily donating blood.

In the future, Dr. Bernier hopes to investigate structure/activity relationships for attractants and repellants, ultimately allowing prediction of a compound’s properties without bioassay testing; determine effective blends for multiple species; and evaluate emanations from other species such as chickens and cattle. Because individual mosquito species have evolved to prey on specific species, reducing attacks may contribute to the reduction of diseases such as malaria, dengue fever and yellow fever which involve mosquitoes as vectors.

From the Editor's Desk

Ravi Ravichandran

As the Past President of MCF and thus a Board member, I had the privilege of voting for Luke Charpentier as the interim President. Luke will fill out the term of office until the Spring Symposium. To many of you Luke is not a stranger. He has held several positions in MCF which include President (1998-1999) and Past President (1999-2000). Thank you Luke for agreeing to be the President.

The preparation for the Spring Symposium is is in full swing.

As promised in the last newsletter. I have managed to get a guest column from Dr. Chris Thomas on LC/ICP. Again, I request you to please consider writing a guest column or solicit guest columns from people you know on a subject related to separation science.

May I request all of you to spread the word about Undergraduate Award(UGA) and Palmer Award? There is still time! Please visit the MCF website for details.

By the way, the next issue of Retention Times will be coming out early March. The deadline for submitting newsletter items for February issue is February 16, 2001.

Selectivity is a vital ingredient in any separation scheme used in analytical chemistry. In chromatography, selectivity is tuned by the choice of column and mobile phase chemistry, as well as the detector specificity. While we are all familiar with conventional LC detectors such as UV, conductivity, fluorescence, and MS, I would like to introduce you to a new kind of detector used to improve selectivity in chromatography: the inductively coupled plasma (ICP).

ICP is a well-known technique used to characterize trace elements in materials, especially water. The technique is capable of detecting elements at the parts per billion (ICP-Optical Emission Spectrometry) and parts per trillion (ICP-Mass Spectrometry) levels. With such a selective and sensitive detector, it seems an obvious choice to use as an LC detector. But what do you gain in making this combination? From the chromatographer's perspective, you gain an extremely selective detector, which greatly simplifies complex separations reliant on universal detectors. From the elemental analysis perspective, you gain a whole new dimension in elemental information--that is the state of chemical combination of an element. Figure 1 shows an example of this capability: conventional ICP provides total Cr without regard to oxidation state of the chromium. Add a separation to this analysis and Cr (III) and Cr (VI) can be determined selectively and independently, down to very low levels.

Figure 1. Total elemental measurement vs. speciated elemental measurement.

The instrumental setup for such an experiment is actually quite simple (see Figure 2). The key is the interface: the effluent from the column must be introduced into the ICP without degrading chromatographic resolution. In some separation schemes, simply connecting the effluent from the column to the conventional ICP nebulizer and spray chamber is sufficient. In others, where dead volume needs to be minimized, a special low flow, low dead volume nebulizer (Direct Injection Nebulizer) can be used to directly inject the sample into the plasma to minimize dead volume. The ICP can acquire data as rapidly as 5 milliseconds per element, so peak definition is similar to that of conventional LC detectors. Since the detector is so selective, we can afford to simply use short guard columns to separate the analyte of interest, greatly reducing the total analysis time.

Figure 2. Instrumental box diagram for LC-ICP system. (IC/LC = Ion Chromatography / Liquid Chromatography, DIN = Direct Injection Nebulizer, ICP=Inductively Coupled Plasma, MS = Mass Spectrometer, OES = Optical Emission Spectrometer)

One example of the technique is the separation of chromium (III) and (VI). In this example, we are interested in measuring trace quantities of Cr (III) in the presence of large amounts of Cr (VI), as chromate (CrO42-). Figure 3 shows an example of the separation of the chromium species from the chromate plating bath.

Figure 3. Chromium speciation in Cr (VI) plating bath with IC-ICP-MS. Flow Rate: 200 mL/minute per minute Guard column (Dionex AG-11).

Another example of this technique is the separation of a trace analyte from a matrix. Ce is an element that causes severe spectral interferences in ICP-OES and severe matrix effects in ICP-MS. A 500 ppm sample of Ce was spiked with 10 ppb of several elements and injected onto a microbore anion guard column with dilute nitric acid as the eluent (see Figure 4).

Notice the separation of Ce from the other analyte. In effect, the elements eluting before Ce are analyzed matrix-free.

Figure 4. Separation of trace elements (10 ppb) from 500 ppm Ce matrix using IC-ICP-MS. Flow Rate: 200 mL/min per minute Mobile Phase 100 mM nitric acid. Microbore anion guard column (Dionex AG-11).

The technique can also be extended to organics for separations involving organic solvents. This technique would be useful in looking at organometallics, solvent extracts, and catalysts.While the technique is quite powerful, there are a few limitations that should be addressed. Sample preparation is a key limitation: species in a solid sample must be transferred to a solution without changing their state (i.e. oxidation). Also, the chemistry of the separations and analyte are quite complex and yet to be fully documented in the literature. For instance, coming up with a separation scheme for Sn (II) and Sn (IV) requires stabilization of the two forms on the column as well as an appropriate mobile phase to separate these on a suitable column.

Bibilography

"New Approaches for Elemental Speciation Using Plasma Mass Spectrometry," C. B'Hymer, J.A. Brisbin, K. L. Sutton, and J. A. Caruso, American Laboratory, February 2000, pp. 17-39.

2001Spring Symposium Courses

"Practical Advice for Developing Better GC Methods"
Cameron George, Technical Support Engineer,
Daron Decker, Technical Specialist, Agilent Technologies

"Basic LC/MS Techniques and Applications"
Matthew Dilts, Technical Sales Engineer, Micromass, Inc.
Dr. Roger Upham, Regional Sales Manager, Micromass, Inc.

"An Introduction to Ion Chromatography"
Dr. Arthur Fitchett, Ion Chromatography Evangelist, Dionex Corp.

For further information about the above courses contact Education Committee Chair, Kim Grandprey at kimg29@idt.net.

Minutes of the 25 January 2001 MCF Board Meeting

Present:
G Bailie, L Charpentier, S Cherney, J Jopke, R Ravichandaran, P Sackett, W Swanson

Treasurer’s Report:
The end-of-year 2000 balance is ~$7000 higher than the EOY 1999 balance, and efforts continue to properly categorize expenses to allow more informed budget planning.

President:
The Board unanimously elected president Luke Charpentier to serve out Becky Wittrig’s term.

Symposium Committee:
The call for papers is out, and all focus and keynote speakers have been confirmed. Booth sales are expected to pick up once PittCon is history.

Education Committee:
No submissions have been received for the UGA to date, deadline is 1 March. The HPLC class registration is full at 24, and 1 registration has been received for the Symposium courses. Michelle Pierson Iverson will replace Kim Grandprey as chair this fall. Advanced HPLC will be offered this fall, dates and location to be announced. Lars Pekay has declined an invitation to teach Design of Experiments again, but is willing to pass his course notes on to anyone willing to teach.

Quarterly Meeting:
A crowd which was disappointing in volume but more than compensated in enthusiasm showed up for the Winter meeting. The Spring meeting will most likely feature Peter Kissinger, dates and location yet to be determined.

Tips on Technical Writing

Brian Leafblad

Have you ever read an article or report and wondered what in the world the author was trying to say? Have you ever written a masterpiece only to have someone ask you what you were trying to say? If you haven’t found yourself in these situations yet, you probably will at some point. Writing is easy. Writing well is hard. Technical writing is even more difficult. What I am going to talk about is five pointers from a technical writing class I am taking. A lot of this will probably be familiar to most of you, but hopefully it will be a worthwhile reminder.

The single most important thing to remember in writing well is to know your audience. Are you writing an article for publication in a reviewed journal? Or, are you writing a project report to be read by someone in marketing? Are you writing to fellow chromatographers or to someone who isn’t even a scientist? Do you need to be formal or can you be informal? We, as scientists, are often characterized as smart people who can’t communicate to "normal" people. This is often why. We talk or write to others as if they are fellow experts in our field and they often don’t have a clue about what we are saying.

Another important aspect of good writing is variety. You may be able to elucidate the murkiest principles and results so that anyone can understand, but if your reader is bored they may fall asleep half way through. So, use variety in your words, sentences and paragraphs. Mix in short, common words with the big, complex scientific words we have to use. Use short sentences. Use long sentences. Then combine them all into some short paragraphs and some long ones.

Strike a balance between explaining every minutia and explaining nothing. You as the author are the expert, but your readers may not be. What is painfully obvious to you may be way over your reader’s head. So, avoid using words like clearly and obviously, especially when trying to drive home an important point. If your reader doesn’t get it, it won’t be clear or obvious to them. On the other hand, you don’t want to insult your audience by writing down to them. This is why knowing your audience is so important. You can assume more previous knowledge writing to fellow chromatographers than you can when writing to someone in marketing or sales, for example.

There is nothing wrong with using the active voice when you write. But again, strike a balance. Scientific writing is typically passive. We write things like, "The first experiment was performed with a gradient of 25% to 75% methanol over 15 minutes" rather than say, "I (or we) used a gradient of 25% to 75% methanol over 15 minutes for the first experiment." It is ok to take credit for your work, just keep two things in mind. First, if you say I did this or we did that over and over and over, you will come off sounding arrogant. Second, remember your audience. It is easier to use the active I and we when writing internal reports to your boss or a customer. It is standard to be more passive in writing for external publication.

One last tip! Have someone else read your work. Find someone that you trust will give you honest, helpful criticism and know what they are talking about. Even better, have two or three people that represent your target audience give you feedback. You know what you are trying to say while they read what you actually do say. There are a lot of good writers out there. Even if you are a good writer, use others to make yourself better.

Education Corner
MCF Education - What a Deal!

Kimberley Grandprey

Have you ever stopped to wonder about the education courses offered to the membership body of the MCF? Why or how they are available for you? Are you taking your education opportunities for granted?

If one surfs the Internet, several other organizations that offer courses throughout the year can be easily found (in addition to vendor classes). Others can be found listed in your monthly LCGC magazine. For a simple comparison, examine the costs of a Beginning HPLC course with lab:

These results show that the typical cost of a MCF course is half that of similar courses offered nationally. Examination of other MCF classes shows the same results. The most important aspect of the mission of the MCF is to provide area chromatographers with an opportunity to expand their knowledge of separation science. Offering classes at such affordable rates benefits both the membership body and MCF.

What factors help MCF to keep course costs down?

Location: MCF courses are typically offered at the Earle Brown Continuing Education Center at the University of Minnesota. While the location is comfortable and functional for most of the MCF membership body, the cost has been reasonable.

Vendors: Vendors regularly schedule themselves to help with our courses, providing for the best "hands on" experience possible. They provide an opportunity for exposure to multiple types of instruments during your training. Did you know that this is strictly a volunteer effort on their part?

Instructors: We are lucky to have a pool of very talented instructors to teach our chromatography courses. They are teaching because they love chromatography and want everyone to have the chance for the learning experience. While the MCF provides a stipend for the instructors, it is not one that would entice those instructors out on a major money making circuit!

Volunteer Organization: The MCF is a non-profit organization. This means that every person involved with the MCF volunteers for the job they do. All income generated from courses goes directly into the MCF coffers to fund events and items such as quarterly meetings, the Undergraduate Award (UGA) and the annual Symposium.

MCF currently offers 2 – 3 regular courses per year as well as 3 short courses at the Spring Symposium. While there are always people who need particular courses throughout the year, we need about 15 students to make a class financially viable. We have found that offering a course more than once a year does not usually draw enough attendees to pay for itself. The biggest hurdle is the need for more volunteers to organize and run courses. We are always looking for new volunteers with fresh ideas for course offerings and organizational ideas. Guess what? We are looking for you!

22nd Annual Spring Symposium Call for Papers