How hard is CG to get a handle on

[NZBen]

I'm considering buying an HP5890 II with an intention to measure food samples for things like pesticide, BPA, vinyl benzene residues etc. There are two options locally available, one has dual columns the dual FID the other is jst single - what advantages are there with the dual unit? I assume you can put a polar column in one and vise versa in the other?

I'm wanting to know if the wise and experienced among you think I'll be capable or just wasting my time and money.

I am fairly good at picking up new things, I have lab experience and have taught myself to setup use, service and repair XRF spectrometers. I have good electronics and mechanical experience.

I've not used a CG before but have done some reading and think I have a rough handle on it. I think the biggest issue I'll have initially is food sample prep and machine setup. I anticipate destroying a couple of columns during my learning phase.

I was thinking about using H2 as the carrier gas, I'm not too concerned about explosion/fire risk. Everything I've read on the net says you should use as high quality H2 as poss - but how critical is it? I don't want to spend money unnecessarily. We dont have large resources here so the cost goes up fairly fast with purity. A bottle of 99.95% gas is $38 where as 99.999% is $540. I believe the largest impurity is O2, I do have a number of cryogenic coolers that could freeze out any O2/N2 in the gas stream. Also I guess the other option is to look at a gas generator?

Any thoughts / suggestions would be greatly appreciated.

Thx
Brendon

[Peter Apps]

Hi Brendon

Welcome to the forum.

You ask a simple question; would you be wasting your money ?

The simple answer is: Yes.

A GC-FID will not be able to do the analyses that you want to do - you need the extra selectivity of a mass spectrometer detector to get the necessary detection limits in complex matrices like food. With an FID you might be able to work on surface and drinking water samples, but even then you will struggle to reach the detection limits that are required for serious work.

Your first step needs to be to look up the methods and equipment that are used to do these analyses in real working labs - then decide if you want to try to replicate that.

Alternatively, look up what you can do with a GC-FID and decide if those are the kind of analyses that you would be interested in doing.

Peter

[Don_Hilton]

Keep in mind that even with a GC-MS, sample preparation is a big part of the picture. Keeping the GC or GC/MS up and running can be the easy part.

[NZBen]

Thanks so much for that you guys just saved me lots of money and frustration. However.... now wondering, should I save some more pennies and look for a GC/MS.

I still realize the sample prep is key and where all the time is involved. Having little knowledge on these machines I would be concerned some inadvertent poor prep may damage the MS - I dont mind damaging the odd column and think it would be unlikely to irreparably damage an FID but the MS concerns me.

[Peter Apps]

Why do you want to analyze food samples for the analytes that you mention ? Is this going to become a commercial venture, is it part of a larger operation, or just something that piques your interest ?

If you just want to have fun with a GC then have a go at essential oils - they come ready prepared from aromatherapy shops, they are satisfyingly complex in their makeup, you can detect their components readily with an FID and once you get some skills developed you can try making your own extracts from local plants etc.

Peter

[MSCHemist]

It is diffucult to put two columns one polar and one not in one GC because the polar columns like a wax have a max temp of 250-260 deg C and the nonpolars like db-1 or db-5 can go as high as 325-350+.

I run a lot of food samples. I do a lot of flavors duplication and identification (TIC) as well as some trace level analyses like 3-mcpd on the GC/MS and I run the more routine quant methods on my 5890-FID like amino acids, piperine, I'm working on scoville heat units and some silyated compound methods (silyation analyses quickly foul up the MS source).

[Don_Hilton]

now wondering, should I save some more pennies and look for a GC/MS.

I do a pretty good job playing a radio. I saved up some pennies and purchased a guitar. It now has a thick coating of dust on it...

As long as you are willing to take the time and effort to learn the techniques that make a GC/MS usful, it can be a profitable adventure. But just because they can look at the screen on a computer beside a GC/MS on CSI and read that the crime was done by a fellow driving a red car with Arkansas plates, it is not really that easy. (Even for those of us who have done this for a while, the plates can be really trickly sometimes... )

As long as your samples are reasonable for chrmatography, you are not likely to damage the MS. And, when you have good chromatography going on, you have many wonderful spectra to dig through. For some of us, this is where the fun begins. But, it is also where the novice gets into a lot of trouble. The computer will suggest names for compounds based on on a spectral library match score. But you need to have the chemical knowledge - about your samples, the chromatography, and what goes on in a mass spectrometer to make a judgement as to wether that name makes sense. I recall waliking into a QC lab where they had a method for checking flavorings the analyst was supposed to be sure that compunds A, B, and C were present and matched the custom library where the proprietary compunds were labeled A, B, and C. The new, bright, young chemist in the lab decided that the laboratory should be more "scientific" and applied library searches to the compunds. I saw the list and a couple of compunds listed, if actually present, would probably have requried personel in the lab to be wearing moon suits. I shudder to think what would have happend had FDA walked through that lab.

If you take the time to learn - go for it. Segovia did it with a guitar, others of us work our art on GC/MS systems to smaller audiences.

[NZBen]

Thanks for all you answers so far. Basically my goal is not for profit, but for the greater good of mankind I would like to buy regular foods from the supermarket (competing brands), test them for residues and publish the results on a webpage/facebook etc.

I've talked to several farmers, livestock and produce. Apparently sprays, antibiotics etc are most often used outside their recommended range, along with epoxy/styrene food packaging leaching. What I want to accomplish is making the consumers aware of what they are consuming in an easy to read platform and potentially have a flow on affect of food suppliers to push toward lower levels of synthetic contaminants.

I'm not out to cause panic or chemophobia amongst society, I will try to present data in a balanced format but with the ultimate goal to allow consumers to make an informed decision.

New Zealanders have one of the highest cancer rates in the world, I believe its due to a lot of what we are eating. Many crops and farmland in the country as an example get fertilized with superphophate high in cadmium, the NZ food safety authority carry do not regularly carry out food safety testing - and with a statement they provided to me "we leave it up to industry to decide what is safe"

I'm well aware of the fact what the computer says is not necessarily the case from my experience with Xray fluorescing spectrometry - the user must be familiar with the expected graphical spectrum and once use to it, it's fairly easy to tell if the computer got it right or not. Many people I trained on it struggled initially - expecting the results would be as displayed.

[Peter Apps]

Forgive me for being blunt - you are rushing in where angels fear to tread.

For your results to have any credibility at all your "lab" will have to be accredited to the same standard as the monitoring and surveillance labs that are already analysing at least some of the food in New Zealand. With a single GC-MS and learning as you go along you are not going to get that accreditation for several years, if ever.

What do you think is going to happen when you post that product X, Brand Y has some dreadful chemical in it ? - you will have to hock your GC-MS to pay for your legal fees when you get sued. The opposition will line up a row of experts with decades of experience and all sorts of higher degrees in analytical chemistry with the specific brief of making you look like a bumbling amateur.

If you really want to poke a hornet's nest in the food industry take a look at undeclared meat species in processed meats. You can do that with off-the-shelf DNA kits, or if you want a cheaper (and just as effective) alternative Google Ouchterlony immunodiffusion.

Peter

[NZBen]

I love to rush in where angels fear to tread, I find its the sort of think that makes life exciting and gives me the motivation to get out of bed early in the morning.

I am well aware of the legal ramifications and am taking advice from lawyers about it before I make a start in an effort to minimize collateral damage - which I fully expect to encounter.

At the initial stages I am not too concerned with the credibility of my work, if for eg I find something that I consider to be really nasty I may decide to get it re tested at an accredited Lab. I am fairly meticulous with my work and use to run an accredited instrument calibration laboratory here in NZ.

I enjoy things that people find too hard or too risky. I totally agree with you that very few people would dare to tread where I aim to. Especially since there will be no financial gain to be had.

This week already I have been to two funerals from cancer, I have a friend who have had three members of their family diagnosed with cancer THIS YEAR. A decade ago the cancer society said cancer in NZ affects 1 in 5 persons, today they say it affects 1 in 3. In Australia it now affects 1 in 2 men, http://www.cancer.org.au/about-cancer/w ... gures.html people have all number of theories and many believe its preposterous to think synthetic chemicals can be causing it, and that's fine, I'm not going to try and change their mind.

I think people deserve to have an idea what they are consuming. While many wont agree with what I'm trying to do, I think a lot will. If you listen to industry or regulatory bodies things like asbestos was perfectly safe to work with till the late 70's even tho it was linked to mesothelioma in 1911, tetraethyl lead was a perfectly safe additive to put into fuel for 50 years. DDT wasnt harmful for about 40 years. Xrays were perfectly safe to expose yourself to and were used in shoe shops for trivial purposes such as checking the fit of a shoe (fluoroscope - equivalent to 1000 chest xrays per fitting). The list goes on.

I do apologize for my digression on this thread. This is something I may or may not do, but I am passionate about. I genuinely people should be able to make an educated decision about what they expose themselves to.

I appreciate its specialist equipment with specialist operating experience required and there will likely be a steep and expensive learning curve. I just wanted to get a feel for the equipment, processes and practices from the experienced and knowledgeable folk on this board.

[Peter Apps]

Your concern does you credit.

How many people in New Zealand smoke, and how many are obese, how many have diseases associated with drinking too much alcohol ? Do these statistics suggest that people make "informed choices" about health and their eating habits and lifestyles ?

On the cadmium in fertilizer problem (you probably know that you can't analyze for cadmium with a GC), do some back of the envelope calculations; how much fertilizer goes onto the land ?, what is its cadmium content ?, how much of that cadmium is taken up plants ?, how much of that cadmium is eaten by consumers ?, what are the health impacts ?

This is all about balance of risks - are the health impacts greater from plasticizers leached from packaging, or from microbial pathogens on exposed food ?. Does a reduction in mycotoxin concentration justify the health impacts of the use of fungicides ?

Good luck with it.

Peter

[gcguy]

Just to add my thoughts....
Probably less than 10% of agrichemical "contaminants" in food would be volatile/stable enough to be seen on GC, GC/MS.
There are thousands of naturally occuring pesticides that plants have evolved, most of which will have no tox data! I was told many years ago that the level of certain "natural" pesticides in cabbage is so high they would not receive registration for sale if it was a new product. So much for "organic" food.
All new pesticides these days go through tox and metabolite testing that is not dissimilar to the pharms industry but with one important extra...environmental fate. Stuff put on fields these days must be accounted for by the producer of these compounds before a product licence is granted.

GCguy

[NZBen]

Thanks for all yr input guys. Ive learned a lot from this forum and this post already. I dont intend to tell people whats good and whats bad, just show what was found. People can make their own mind up about what they choose to buy and feed their family.

With regards to cadmium I was aware its not really volatile enough to send through the machine, I can pick it up down to 10ppm with XRF however thats not sensitive enough - there are plenty of chemical sets out there for heavy metals, I'll have a play with those. I know none of this may have an influence on cancer - but who knows... It may. One thing that sparked my concern was from a mate of mine who started growing tomatoes.. he did his hazardous goods course so he could handle sprays etc. He said they have a three week stand down, but.. "most of the growers spray right until harvest because no one ever checks"

Question time...

Probably less than 10% of agrichemical "contaminants" in food would be volatile/stable enough to be seen on GC, GC/MS

How come??? I was under the impression that a GC/MS would pick nearly every pesticide if there were significant traces there? I dont mind if I cant see whats been used if it's broken down into something. Sales brochures Ive read go on about detecting over 500 diff pesticides etc...

Terminology wise I see some people refer to Mass Detectors and others refer to Mass Spectrometers - I assume they r one n the same? - jst checkin.

Ive been looking as GC/MS on eBay and one thing I wonder is the MS box often doesnt seem large enough to have a turbo and backing pump inside. Are they integral to the unit or do you need to provide vacuum from another source?

Are there any brands to stay away from? I'm Looking at a Finnigan Trace 2000 with polaris mass detector... does anyone have much bad to say about this model?

Thanks

[Don_Hilton]

A lot of the legacy pesticides - like organocholoro pesticides are "easy" to detect with GC/MS. Many of the newer pesticides are more easily degraded at temperatures needed for GC/MS analysis or are too polar to be analyzed by GC/MS.

On purchasing an instrument from eBay... Look at other posts on this site. There is a good chance that you will purchase in instrument billed as "in good condition" that will have been customized and be missing parts needed to work as you want it to - or just missing parts. The MS should have a backing pump (also known as a rough pump) that will sit on the floor close to the instrument. This should be part of the package, but I've seen more than one lab get rid of a mass spec that was not usable to them and keep the pump as a backup in the event a rough pump failed on some other instrument. There are used instrument dealers - and unless you have experience setting up and repairing GC/MS instruments so that you can look at an instrument and see what is missing, you might look to a reputable dealer. Even the refurbished instruments will have some issues - and you can see some accounts of issues after puchase from eBay and from used isntrument dealers on various threads on this site.

[MSCHemist]

Don't but a GC/MS off ebay or Labx. Go with one of the professional refurbishers I bought a GC/MS off lab-x with no EI source, an analyzer chamber full of diff pump oil, bad seals and that was just from visual inspection. I then bought one from Gentech and it was much better.

As for rough pumps, Vac-tech and AJ sell rebuild Edwards E2M1.5's for under a $1000 USD. Make sure you get a KF 10/16 centering seal.