Is That Really bis (2-chloroisopropyl) ether: Potential Issues for EPA Methods 625 and 8270
I would like to welcome you all to SPEX CertiPrep’s Webinar “Is That Really bis (2-chloroisopropyl) ether: Potential Issues for EPA Methods 625 and 8270”. I would like to introduce myself, I’m Amy Williams, I am the Marketing Manager for SPEX CertiPrep and I will be monitoring the presentation today. Before we begin I would just like to get a few housekeeping tips out of the way. Everyone in attendance will receive emails with the presentation slides and links to the webinar recording on our YouTube channel. If you have any questions during the presentation, please type them in the question box on your screen and we will answer them during the Q & A session following the webinar. Now, I would like to introduce our presenters for today’s webinar. Mark Ferry is the GC/MS technical specialist for the ECS division of SPEX CertiPrep. He has worked with GC and GC/MS systems for over thirty years and his areas of expertise include EPA 500 , 600 and 8000 series GC and GC/MS methods. He formed Environmental Consulting and Supplies in 1991, which was acquired by SPEX in 2015. And Julian Burton is the Director of Organic Manufacturing at SPEX CertiPrep. He has a PhD in chemistry from Rutgers and joined SPEX in 2012. And prior to joining us, he was in R & D performing instrument and detection algorithm design for trace detection systems. Now I would like to hand the presentation over to Mark. Thank you Amy, welcome everyone.
The first thing you're probably wondering is “why would anyone want to hold a webinar on bis (2-chlorosiopropyl) ether? Its not the most glamorous of subjects but there is a problem growing and needs to be addressed. So the idea for this webinar occurred to me several years ago when I was purchasing this new material and I noticed the price had gone up from three hundred dollars per gram to about three thousand dollars per gram. So I started looking into why that was. And I decided at some point to hold a webinar to not only address that issue but to also clarify some ambiguities that have been existing for this compound and its isomer 2,2’-Oxybis (1-chloropropane) really since I started in mass spec thirty years ago. So we are going to address those problems, those ambiguities, and we are also going to propose a solution to these problems. And finally at the end, we are going to solicit input from the laboratories and also, ultimately, to other standards providers, with the intent of contacting the EPA so we can solve this problem.
OK now why is bis (2-chloroisopropyl) ether important? Well it's a target compound on EPA method 625 and 8270. And it’s become an issue over the past few years because of the following; number one, there’s been widespread confusion among labs and providers and on EPA methods as to the correct CAS number, name and structure for this compound and its isomers. Number two, as I mentioned earlier, the cost has risen from three hundred dollars per gram to three thousand dollars per gram. That cost will be passed on to the labs unless something can be done to bring down the cost. And even more troublesome than the rising cost is that is it frequently unavailable. If you call to order it, it will frequently be backordered, which jeopardizes the ability of suppliers to make mixes that contain this analyte and therefore jeopardizing the ability of the labs to obtain standards in a timely manner. Now the first thing is, what confusion exists? On EPA method 625 and 8270 as well as on lab reporting documents, and on certificates of analysis from suppliers, one might see either or both of the following isomers listed; bis (2-chloroisopropyl) ether and 2,2’-Oxybis (1-chloropropane). Note these are two separate compounds with different structured and different CAS numbers. To use them interchangeably as if they are the same compound is incorrect and that is what we frequently see; people mix and match CAS numbers, they use them as if they’re the same compound, but they’re really not. At this point, I will not turn the presentation over to Julian.
Thank you Mark. Here we see the two isomers on screen and the top isomer is the bis (2-chloroisopropyl) ether and you can see the CAS number of the two isomers there are very different. As is typical with this sort of compound, we are seeing the difference between a chain and a branch substance and in the bis (2-chloroisopropyl) ether we have one carbon between our chlorine and our oxygen and in the other isomer we have two carbons between the chlorine and the oxygen. So what does that mean when we actually run the sample with the chemicals in it? We see both of these peaks. They’re not resolved on a GC/MS system. That’s not unusual, like most isomers you would expect that they’re going to have similar physical characteristics such as boiling points, they’ll elute closely on most columns that we would use to do the analysis. They have very similar mass spectre. So what we see is that in most cases you see a sort of one big peak or a peak with a shoulder and not really fully isolated on most GC systems. So what that means is that labs will typically integrate a total area of ion 45 and report the result as either bis (2-chloroisopropyl) ether or 2,2’-Oxybis (1-chloropropane). Now what they should be doing is reporting a combined total of both of them and that is one of the issues that we’ve identified. Mark..
All right, let's talk a little bit more about the cost and availability problems, which is what really started me on this path. When the price went from three hundred dollar per gram four or five years ago to five hundred dollars per gram, to a thousand dollars per gram to its current three thousand dollars per gram price I started asking “why is this happening?”. So I contacted domestic suppliers and suppliers abroad and we believe that the answer to that is that the process necessary to obtain the two isomer, bis (2-chloroisopropyl) ether standard from the three isomer starting material is quite costly. So now I’ve introduced a new term, there’s a third isomer? Yes, there’s a third isomer and that’s, I believe, the root of the problem. Apparently, when US suppliers obtain this bis (2-chloroisopropyl) ether it actually contained a third isomer, which has been deemed an impurity. So the suppliers, either here or abroad, have to go through some extreme measures, presumably some complex fractional distillation procedure, to remove ninety percent of this third isomer. So let's talk more about that third isomer. Data obtained by ECS and SPEX with our in-house GC/MS systems and in conjunction with information provided by Supelco, application note 18, seems to indicate that the third isomer is bis (3-chloroporpyl) ether. And the structure of bis (3-chloropropyl) ether is shown on the screen and you will notice that it has a separate CAS number from the other two isomers and that there are three carbons between the chlorine and the oxygen. And the other two isomers are shown on the right side of the screen so you can see that they are three distinct isomers, three separate compounds.
Let’s take a look at the chromatography you would obtain. On the top figure is the two-isomer standard that ECS and SPEX and virtually all suppliers have been using. You notice that you see two, on our system we have a high-resolution column we are able to separate actually you’ll see all three isomers. You’ll see two sharp peaks and then you see the third little shoulder right here, that’s the third isomer. If you were to buy the three-isomer standard that has not had the purification process, you see three distinct peaks. So in both figures, the first two isomers are bis (2-chloroisopropyl) ether and 2,2’-Oxybis (1-chloropropane). I don't know which isomer is which, for the purposes of this webinar it really doesn’t matter because as Julian said you are going to integrate the combined area and report it as a sum. You can see on the top chromatogram that third isomer is a very small blip on the shoulder of the second peak; it’s only about two point five (2.5) percent of the total area. Where on the bottom, the unpurified three-component isomer, the third isomer is twenty-five percent of the total area. And we know what the isomers are, because when we do a library search of both chromatograms, it comes up with a ninety percent match with bis (3-chloropropyl) ether in our NIST library. So that led us to conclude that what’s happening is that the raw material has the three isomers and suppliers are now going through a process to remove ninety plus percent of that third isomer.
Ok we have three isomers, now what? As I told you, they’re removing this third isomer, so that raises three questions; number one, why are they doing this? Number two is this bis (3-chloropropyl) ether really an impurity? And three, why not just provide the three-isomer mix? And on the screen you can see that, those of you familiar with EPA methods 625 and 8270, will recognize the mass spectrum as the bis (2-chloroisopropyl) ether. And on the top screen you get a zoom in and you can actually see the shoulder of the second peak, which is that third isomer which we can confirm. Ok so let’s answer those questions that I just posed. Why are they doing this? In my opinion it’s just because it’s the inertia that has always existed in the industry. I’ve been doing GC/MS since 1985, this is when I starting doing method 625 and on every EPA method I’ve ever seen, on every lab reporting document I’ve ever seen, when I got into consulting I would go from lab to lab throughout the United States, I would see certificate of analysis from other suppliers, the only two compounds I ever saw were bis (2-chloroisopropyl) ether and 2,2’-Oxybis (1-chloropropane). There was no mention of a third isomer and most of you probably didn't even realize it existed until just now. So it’s understandable that suppliers would continue along that path unless there was some motivation, some reason to change, mainly the EPA changing the EPA 625 and 8270 methods. In the absence of that, it is unlikely that there’s going to be a reason for change. Next question, is the bis (3-chloropropyl) ether truly an impurity? Well no, it’s not an impurity, it's a third isomer that would naturally appear if the other two isomers were present if you were to ever find it in a natural industrial sample. Third question, why not just provide a three-isomer mix? Well that’s what we think should be going on. Since the three-isomer mix, in our opinion, would represent what a lab might find if it had an industrial waste sample, a real world sample that they’re analyzing in their lab, it seems logical that if the material in the environment has three isomers then the calibration standard also should have three isomers. So why is the three isomer standard superior? Well the material itself is easier to synthesize, it doesn’t require “quote/un-quote” purification, and because it doesn't require the purification its readily available at only three hundred dollars per gram, not three thousand dollars per gram and it doesn't have availability issues because it doesn't have to go through this fractional distillation process. Most importantly, it best represents what a lab might see in a real world sample. So we’ve been using this two component bis (2-chloroisopropyl) ether for thirty plus years and, in actuality, they’ve been removing this third isomer which we now think that they should not have been doing; we should have been using this three-isomer standard all along. So better late than never, we are finding it came to light only because the cost went up so high but now we are aware of it, I think that we should make some changes. Now, what about quantitation? You might think to yourself “ok what if we were to have this three-component standard and we had a PT sample that only had the two-component standard, would we be able to quantitate accurately and get accurate PT results?”. Well the answer is no, there’s a difference in the responses between the two or three isomer standards. In the two isomer mix ion 45, which is the quant ion, represents about thirty nine percent of the total area. In the three- isomer, ion 45 represents only about thirty-five percent of the total area. So that’s a twelve percent built-in error right there. Now the reason for that is because, in that third isomer bis (3-chloropropyl) ether, ion 45’s abundance relative to the total ion chromatogram is slightly less than it is in the other two isomers, there’s more ion 41 that’s just the fragmentation pattern of that particular compound is that you get more 41 and it comes out at the expense of ion 45. That causes this skewing in the quantitation. So unless the proficiency ampules and the calibration standards are both of the same type you are going to get a twelve percent built-in error and that’s obviously not good. This is why it’s important that the entire industry decide whether we want to stick with the two-component isomer or switch to the three isomer mix.
So where do we go form here? Well that really depends on the labs. We don't have the power to change the EPA methods, only the EPA does. But what we really need is a consensus in the environmental industry in order to affect some kind of change. So we want to contact other suppliers in the industry and ultimately to the EPA with the hopes that they will change the methods and make it state, unequivocally, that you should have a three-isomer standard and that you should sum the entire area of ion 45 over those three isomers and report the sum. And in order to do that, we need to get some input from the labs. First of all, we presented our opinion on this, none of this is a fact, this is just our opinion that the three-isomer mix would be superior. Now that you have heard our opinion, we’d like to know your opinion. You’ve been doing these methods for many years, you’re used to the two-isomer mix, do you agree with us that the industry should switch to the three-isomer mix or would you rather just stay with the two-isomer mix? So we’d like you to email us with your opinion on that. The other thing I am interested in is, have you ever found any of the bis (2-chloropropyl) isomers in any sample. If you have, do you remember if you found one isomer, two isomers, or all three isomers? We are just trying to get a feel for how prevalent this compound is in nature. So my email address is right there on the screen. if you can please email me your opinion and if you’ve ever found this compound in any samples we’d appreciate it.
Ok I’ll turn this back over to Amy. Ok, Thank you very much Mark and to Julian. We do have a few questions that we’d like to have answered now so I’ll ask Mark:
Q: What do you plan to do with all the feedback you receive from the webinar?
A: All right what we plan to do is, if there’s not an overwhelming consensus in the labs, then we probably won’t do very much. However, if the overwhelming consensus is that the labs think that the three-isomer mix is superior, we then will start proceeding with this. We are going to contact other suppliers who make this mix, get their opinion on it and if we get enough labs that are interested in change and enough suppliers that are interested in change, then we’re going to contact the EPA and try to get the methods changed.
Q: Are there any other compounds that you have seen with similar concerns?
A: Well there are other compounds that are quite expensive. Some of the PAH neat materials can be seven, eight, nine hundred dollars per gram, but I don’t know of any compounds on the EPA 500 or 600 or 8000 series methods that are anywhere near three thousand dollars per gram. I’m also concerned that if something doesn't happen, that these compounds can be four or five thousand dollars per gram in another couple of years, if they’re even available at all. So to my knowledge this is the only compound where the price has gone up drastically over the last few years and where availability has been a problem so I think it’s limited to just this one compound.
Q: Does this compound have another name? The question is, I cannot find it in the NIST MS2011 library.
A: Well when we did our search we actually found all three. If you go back to the slide here and you look at the bottom, if you do a background subtracted mass spectrum of the first peak, it’ll come up either bis (2-choloroisopropyl) ether or 2,2’-Oxybis (1-chloropropane). The mass specs are so similar that if you do a library search of the second peak you’ll come up with the same two results. And if you do a library search of the third peak, you can’t really do it on the top one because it’s such a small peak, but if you do it on the bottom one on the three component mix, if you were to do a library search of this one, you would come up with a ninety percent match of bis (3-chloropropyl) ether. So, I had the 98K library and the system had no problem at all identifying all three isomers.
Q: And we have another question, when you say 8270, what revision date and number are you quoting?
A: I actually don’t have an answer for that. I just know there’s so many revisions, this is just the standard that we’ve always used. To my knowledge there’s been no changes in this compound in any revisions. If anyone knows of any revisions of EPA methods where this compound is addressed, that would certainly factor into what is going on here. So, you know please email us with that. To my knowledge, they just list these compounds, there’s no mention of the third isomer but if there is, we’d like to know about it.
Q: One more question, as per your explanation about the isomers, I think that the EPA has to agree that the three isomers can be found in real samples, not only one. Is that true?
A: Well I have been in GC/MS for thirty years and I can honestly say that at no lab that I ever worked at or consulted for did I ever find this compound so it seems logical that when its manufactured you get the three isomers that if it were to show up in an industrial waste sample that you would see three isomers. But I have no direct experience with it, which is why I was asking for people to tell us what have you seen? I’ve never seen any of these isomers in any sample, I’m just saying what, if it were to be present, it seems more logical to me that you would see all three isomers, but I can't say for sure. I’m hoping that some of you who are in the lab will have seen this compound and I’ll trust what you tell me with regard to this.
Q: And we have one more question Mark. What are typical spiking levels for these methods?
A: Typically anywhere from fifty to one hundred ppb for water samples or two hundred and fifty to five hundred ppb for soil samples.
Well thank you very much again to Mark and Julian. I am going to be sending out the slides for this presentation to everyone a little bit later today, so you’ll be getting those by email. And you’ll also be getting a copy, within a week or so, of the recording of the presentation. So we very much appreciate you attending this today and we look forward to seeing you at future webinars. Thank You.