Hi AMMRL!
Thank you to all 18 (!) who gave me such great insights into practical aspects
of operating and managing dual-use solids/liquids NMR spectrometers. This is
the kind of help that can't be found in any textbook or manual, and I'm grateful
for your responses and follow-up conversations.
There are three portions of this summary:
* Key Takeaways
* Original post
* Compendium of answers to each question
* Compendium of full responses
To be clear, the interest here is in systems that are equipped so sometimes
they are running liquids, and sometimes they are running solids with the
same magnet, console, and some other components. To switch between modes, one
probe has to be disconnected and removed, and another installed. This requires
commitment of the instrument to one mode or another for a period of time -
it's *not* meant to handle a combination of liquids and solids samples throughout a
given day. For the system we're configuring, the sample would be loaded from the
top of the magnet. This is usually done via a transfer tube that connects a little
platform on top of the magnet to the stator inside the probe. Other systems require
lowering/removal of the probe from the bottom of the magnet to load each sample.
Bruker has developed a new "shuttle" roughly resembling a spinner, which can
transport a solids sample to the probe using the same top-loading autosampler
hardware normally used for liquids.
Thank you all for participating in such a helpful community!
* Josh
KEY TAKEAWAYS
* While most people report that the arrangement works adequately for them,
several indicated they’d prefer to dedicate an instrument for solids work
if possible.
* A big operational risk in the dual-mode configuration is that users may
find it too inconvenient to use either mode, and eventually one set of expensive
hardware sits unused next to the instrument. Availability and scheduling ease
are thus paramount considerations.
* Most of the switchable systems could be safely described as "premium"
instruments, ranging from 500 to 750 MHz. This aligns with a userbase
either willing to undergo advanced training to run experiments themselves,
or be satisfied with the convenience of having staff run their experiments.
* Five facilities reported switching between solids and cryogenic liquids
probes (four helium cryo, one Prodigy). The mechanics of the switch appears
routine, but the cooldown/warmup time affects how quickly the switchover can
be made and how frequently changes can be tolerated without wearing out the
cryogenic hardware.
* Helium cryoprobes are typically given overnight to warm up or cooldown.
Given the intensity of the process, swapping a helium cryoprobe is typically
only done a handful of times in a year, which affects scheduling. It seems
this is best done in large facilities, where users have other options for
advanced work when the switchable instrument is not in their desired configuration.
* Prodigy appears to take about four hours to warm/cool and change. One
Prodigy user reported swapping it out many dozens of times with no apparent
performance loss, suggesting it is not significantly riskier than switching a RT probe
* Switching between RT liquids and solids probes take between 15 minutes
and four hours to change, depending on how careful the staff members are about
making/verifying calibrations.
* Hardware switchover is typically handled by staff, though some facilities
enable users with a strong solids focus to do the switchover if the liquids probes
are non-cryogenic.
* At several facilities, staff runs all or most of the solids experiments.
* A key challenge I see is the need for advance experiment planning. Users
accustomed to signing up for extended experiments a day or two ahead of time may
not transition well into an environment that needs one to three weeks of advanced planning.
* With staff changing a RT liquids probe, it seems one could dedicate a
week every month to solids, and let trained users run it.
* With staff changing a cryogenic probe, it seems the instrument should be dedicated
to solids for one to three weeks every couple of months.
* The facility with the Prodigy probe is actually running solids most of the
time, switching to liquids when demand on other liquids instruments grows. But the
relatively rapid warmup/cooldown time of Prodigy suggests it might work well in an
environment that dedicated the instrument to solids for a few days every month.
* Some facilities operate on a schedule for being in solids or liquids mode,
but allow for some flexibility based on demand. Others report they switch as needed,
but let requests accumulate and switch when there is enough demand. It appears that all
switchable instruments require at least a week of advanced planning, preferably more,
and the amount of use is determined primarily by demand at any given time. The
continuing uncertainty of scheduling appears to be a major driver in dedicating an
instrument for solids full time.
* Risks to hardware are usually the same as any probe change. Swaps are done
by staff or specially trained expert users to reduce the probability of banging the
probe around, damaging the liquids insert or other components. One responded
acknowledged that expert users are often preoccupied with their experiments, and
they may not be sufficiently attentive to probe change protocols. The biggest
risks to hardware appear to not be those associated with probe switching, but the
ones inherent to solids NMR, e.g., rotors breaking while spinning. Modern software
seems to interface well enough with the hardware that it is difficult to inadvertently
blast solids-level high-power RF into a liquids probe.
* On most everyone’s instruments, it is practically impossible for a casual
user to submit a liquids sample to the instrument when configured for solids. I asked
primarily because Bruker has recently developed a "shuttle" that can load solids
samples into the instrument from a SampleCase autosampler. I can see a confused
novice user potentially trying to load a liquids sample when the instrument is
configured for solids. Simply removing all the liquids spinners should give them the hint.
* One helpful insight advocates for Bruker users to purchase their "Autocalibrate"
software package (and, presumably, standard samples). This eases the calibration one
would like to do after any probe change, and sound like a good idea. I think AutoTune
is the Agilent/Varian equivalent.
ORIGINAL POST:
Hi AMMRL.
I'd like some practical insights from anyone experienced with an instrument configured
for switching between liquids and solids NMR, especially operating in a core facility.
In our academic Chemistry research environment, we're considering upgrading a Bruker
instrument that's currently used for liquids walkup and moderately advanced manual use
(VT, DOSY, 2D) so that it can also do solids when needed. We've already scoped out
hardware requirements, but I'd like your help with a number of operations questions, such as:
* For your situation, who is authorized to switch the hardware? Facility staff? Trained expert users?
* How much time does it take to switch modes?
* Do you have a set schedule for solids/liquids modes, or is the switch done as needed?
* What are the major risks to hardware on a dual-mode instrument?
* Do you charge different rates for solids and liquids modes? If so, how do you perform
the dual-mode accounting on one instrument?
* How do you prevent users who are only trained for liquids from trying to use the
instrument in solids mode?
* What other insights do you have?
Thanks for your help.
* Josh
* COMPENDIUM OF RESPONSES *
RESPONSE 1:
I have a 600 with a TCI(F) cryoprobe and an HX solids probe. Only staff changes
the probes. We put in the solids probe about every 8 weeks for our usage. Only
staff set up and run solids. I don't have regular SSNMR users. I don't charge
different rates. I block my scheduler when I do solids. I have a Sample Case
which we shut down when the solids probe is in. The cryoprobe takes 2.5 hours
to warm. 1 hour to swap to SSNMR. I usually run about 1 week on solids.. When we
go back to the cryoprobe, we pump overnight and cool it. Our Bruker is a NEO.
We found we have to do cf with each change. It also takes us several tries to
get the 3.2 mm rotors to seat in the stator.
RESPONSE 2:
we switch between a TXI probe and solids probes often on our 750wb.
it takes about 3 hours to get the solids going and about 1 hour for the liquids.
sometimes liquids can need extensive shimming but the 3d topshim helps.
i've begun to calibrate the entire NMR thru CF to on resonance with adamantane
13C at 38.48ppm for solids but our magnet is large and drifts.
you could probably get away with just using "edprobe" to change between solids
and liquids for the most part without having to worry about the base frequency.
it would be good to run CF once however to install the solids pul progs.
Ps it is best to designate solids and liquids time slots on the order of weeks
to make your life easier.
RESPONSE 3:
. For your situation, who is authorized to switch the hardware? Facility
staff? Trained expert users?
Staff only
. How much time does it take to switch modes?
Couple hours if I do it, less if my staff does
. Do you have a set schedule for solids/liquids modes, or is the switch done as needed?
As needed
. Do you charge different rates for solids and liquids modes? If so, how do you
perform the dual-mode accounting on one instrument?
Hourly rate regardless of who's using. I occasionally charge time to switch if external or non-academic user.
. How do you prevent users who are only trained for liquids from trying to use the instrument in solids mode?
Put up signs - hit with sticks if they can't read signs..
. What other insights do you have?
Not a really big deal - more inconvenience.
RESPONSE 4:
We have a 600 that has been switched every ~2 weeks for 6-7 years.
Only 3 groups (1 Solids, 2 Liquids) are using this instrument.
The rest of the department is using a 400 for routine Liquids samples.
We use an online calendar to inform users which probe is installed.
The schedule is set new every month. No difference in the chargeback rates.
Only our Solids group does the probe changes (in and out).
I usually only check whether the solution probe still performs after a swap.
Both probes had to be sent out for repair this summer with VT issues, probably
due to some mishandling.
RESPONSE 5:
We have two instruments that we operate in this manner. Both have cryoprobes for
liquids. They are open access for liquids, but solids are run strictly by facility
staff or highly trained users.
. For your situation, who is authorized to switch the hardware? Facilitystaff? Trained expert users?
Facility staff only
. How much time does it take to switch modes?
Because of the cryoprobe warmup/cooldown, we typically give ourselves a full day (24h) to make the change.
. Do you have a set schedule for solids/liquids modes, or is the switch done as needed?
Not a set schedule. By default, we run in liquid state, but we ask our solid-state users
to plan their experiments so the solid-state probe will be in for 3 weeks, minimum, and
to give us several weeks notice before they want to use it. We have the luxury of having
dedicated solid-state instruments, as well, so most "urgent" solid-state work can be performed on them.
. What are the major risks to hardware on a dual-mode instrument?
For us, the biggest risk is the cryo-cycling. Our Bruker cryoprobes have been pretty robust,
but I still feel like I'm rolling the dice each time I have to go from 20 K to room temp
and back (one positive is that it extends the interval between coldhead replacement). We
have had rotors break and damage solids probes, but I don't think that is a specific risk to dual-mode.
. Do you charge different rates for solids and liquids modes? If so, how do you perform
the dual-mode accounting on one instrument? Same rates, but since it is generally staff
running solids, we tack on service fees and a rotor rental fee. Our billing process is
convoluted enough that the dual-mode instruments are a drop in the bucket.
. How do you prevent users who are only trained for liquids from trying to use the instrument in solids mode?
We block out the schedule and generally each instrument is in heavy enough use while
in solid-state mode that, if a person were to walk-in and try to use it, an experiment
is fairly likely to be already running.
. What other insights do you have?
Because of various factors, our usage on these two instruments is somewhat low right now.
I can easily imagine a situation where that changes and I have to tighten up my normally
laid back approach to this. In that event, I think the first thing I'd look at would be a
set probe-switching schedule.
RESPONSE 6:
We're down to just 2 instruments (Varian NMRS 500 and Agilent DDR2 750) that we regularly
switch modes on. But in both cases, the answers are the same, so in order:
* For your situation, who is authorized to switch the hardware? Facility staff? Trained expert users?
* Currently, it's facility staff only. Back when we had a dedicated
NMR group, the senior members were permitted to perform switches, but only
with a facility staff member present.
* How much time does it take to switch modes?
* The fastest I've ever performed a switch and calibration was about
30min. That was going to solids with a probe already configured for P31 and using
a solution standard. Most of the time it takes me about an hour for changing &
full calibration provided everything goes smoothly. When we used to do cryoprobe
to UFMAS (with VT stack) changes, that took closer to 2 hours each way. We calibrate
each probe change and that takes the most time once you're comfortable with the hardware changes.
* Do you have a set schedule for solids/liquids modes, or is the switch done as needed?
* Switch as needed. We usually wait until there's a decent queue of
samples/instrument time need built up. Ideally, we try to not switch more than once a week
anymore. Back when we had a solids-focused NMR group and a solution group, we had a set
schedule for the 500 MHz of roughly 4 weeks solution then 2 weeks solids based on the group sizes.
* What are the major risks to hardware on a dual-mode instrument?
* Mainly cable damage/wear. More so an issue when students were involved with switching.
We'd have people step on cables and damage them (like the directional coupler cables) or try to
force connectors together and damage the shielding "fins" on them. The worst I saw was someone
rushing to put the probe in and they hit the bottom of the magnet with the top of the probe
(missed the bore). This resulted in a broken insert in the probe. I guess you could run the risk
of hooking a 1kW solids amp to a solution probe, but we just make it a habit to double check all
connections (thus the staff member present) before starting calibration and have never had
something like this happen.
* Do you charge different rates for solids and liquids modes? If so, how do you perform the
dual-mode accounting on one instrument?
* Only briefly before I started. There were a handful of student accounts that only ran
solids and they were billed at the higher rates. For at least the past 10 years, we charge the
same hourly rate for solutions and solids, but still do charge the time it takes us to pack
samples. For academic, we use the instrument rate. For industrial it's a lower staff hour rate.
This is billed manually for both since all solids samples are now submitted and measured by staff.
* How do you prevent users who are only trained for liquids from trying to use the instrument in solids mode?
* Currently, we have one staff account for running in solids. When away from the
instrument, I lock the screen.
* We only ever had one research group that used solids themselves. So it was in that faculty
member's interest to discourage any untrained students to run solids and potentially break the probe.
* What other insights do you have?
* If you use attenuators on your amps and you find that you need to change their configuration
between modes, it is helpful to move them from the input on the back of the amp to the output of the
attenuation (or newer transmit+attenuation) board on the front of the console. For example, in our
500 MHz setup, we use 6dB on the H1 channel for solutions, but remove it for solids work. Without
attenuation, I've found the standard amp to be sufficient for decoupling and CP. Then I don't have
to retool for the solids amp. Having it on the front where it is easily accessible makes changes go
easier. You don't have to take off the back panel and it reduces the amount of NMR yoga required
for changes (our console is against a wall).
* Power on the solids spin controller and turn on its air supply before connecting the air
lines to the probe. This idiot-proofs the process a bit. At least on our "newer" Varian controller,
if you turn on the air before the controller (or the controller is in manual mode with a valve open),
it will send it directly to the probe. If there's a sample in there, it's going to rocket out.
* Even if changes are set to be staff only, take the time to write up solutions->solids and
solids->solutions SOPs with pictures. You'll appreciate it if you go a while without switching or
need to train a new staff member or TA. I'm currently in the process of creating and updating ours.
RESPONSE 7:
Although I am retired now, I oversaw a dual instrument for many years.
* For your situation, who is authorized to switch the hardware? Facility staff? Trained expert users?
Only the Facility staff were permitted to switch between liquids and solids.
* How much time does it take to switch modes?
Liquid to solids - approx 30 min
Solids to liquids - approx 2 hours
It takes longer to switch to liquids as the shimming requirements are far more stringent.
These times were for a wide bore magnet for which the shim set had to be switched between
liquids and solids. A wide bore shim set was used for solids and a narrow bore shim set
( with spacers to fit in a wide bore magnet) was used for liquids. The switching time will
be less if you are using a narrow bore magnet for both solids and liquids.
* Do you have a set schedule for solids/liquids modes, or is the switch done as needed?
Switched as needed with a 1 week minimum of time on one or the other. It was more common
to have the instrument set up on solids for two weeks at a time.
* What are the major risks to hardware on a dual-mode instrument?
One must be careful with power levels and duty cycles in solids which typically use 1 kW amplifiers.
* Do you charge different rates for solids and liquids modes? If so, how do you perform
the dual-mode accounting on one instrument?
Same rate for solids or liquids.
* How do you prevent users who are only trained for liquids from trying to use the instrument in solids mode?
Honestly, this was not an issue. Users trained only for liquids would have no idea how
to use the instrument for solids. Our booking software told the users whether the instrument was on solids or liquids.
* What other insights do you have?
None.
RESPONSE 8:
Primary comment I'll make is that I really have not liked splitting a spectrometer
in this way. Started this about 3 yrs ago, and was a mess. Found it very hard to
get students on ssNMR to plan ahead, so very hard to manage the calendar. Everyone
wants it during days, and at their convenience. Perhaps you'll figure out a better
method, but a real problem here at least initially. Compounded by the instrument being
pretty busy (~40% on a 24/7 basis) prior to the addition of ssNMR. We're re-working
ssNMR (i.e., grow the user base) after re-opening from pandemic and building closures.
--Only facility staff do the changeover, which takes about 2 hr. Of course more when
we were using the LN2-cooled Prodigy probe (about 4 hr), but about 2hr for bbfo liquids
to a standard cp/mas probe.
--We tried both set schedules for the calendar, and on demand. Neither worked well,
and neither user group was particular happy.
--I don't think there's a lot of risk to the instrument from a hardware perspective,
beyond the normal dangers associated with ssNMR use.
--We charge the same rate for liquids and ssNMR. Too much trouble otherwise with our
last log accounting system. That might change if usage is low now that we're mostly
ssNMR on the instrument.
--Don't worry too much about the weird student trying something. They all know they'd
get in big big trouble if they tried. We did, even so, get a few students trying to
do liquids when the ssNMR probe was in. Got better at _really_ blocking the sample changer.
We're now having the spectrometer do solids "most of the time". Liquids only if it gets
in very high demand in facility. A lot easier, if you have the capacity elsewhere for
liquids. We got that with an upgrade of a low-use liquids instrument recently.
RESPONSE 9:
We have an old Oxford 600 magnet that added new Bruker console with 2 probes: a
carbon observe cryoprobe and their CMP_HRMAS probe. Since both of these are a little
more complicated than a regular RT probe and require careful installation, it is only
done by myself. I suppose one could train a suitable heavy user, but their minds are
typically elsewhere and its typically more than just plug and play. I usually schedule
a full day, not so much for the hardware swap, but to make sure everything is working
as it should after installation. Often things can be ready by the afternoon ( the
cryoprobe needs a night of vacuum pumping). Determining how much time in the magnet for
each probe is an ad hoc decision; I usually gather requests from users for one or the
other and then plan to leave it in for a month or more. This then requires regular
communication with users to make sure they are taking advantage of the current setup
and finding out their research time frames. If the schedule starts to be empty I
make up a deadline for the next swap. If you are switching between an RT liquids
probe and a regular solids probe, then swapping more often wouldn't be such an issue.
We charge the same for both probes; our online scheduling calendar (currently
FACES.ccrc.uga.edu<
https://urldefense.com/v3/__http:/FACES.ccrc.uga.edu__;!!BpyFHLRN4TMTrA!piap5vAHQEAjAC5Br3iKpJvlRuINnqfZhBr3Nhs8zqtDagtttpRmhxWqyrIZh19fGaE$>) has two possibilities and only shows the
active probe calendar, so users only trained on one cannot book time on the other.
Swapping in and out a cryoprobe is a bit of a pain and probably reduces its lifetime.
The HRMAS probe is relatively easy to install and get running - I have only limited
experience with an older DOTY wide-bore solids probe, and that was complicated and
finicky to install and get working correctly. So I guess it depends on the hardware
you are purchasing. My preference always would be to have dedicated instruments without
probe switching but our setup has been working pretty well for about 5 years- we are
keeping an eye on the used magnet market, hoping to get a good deal that coincides
with available funds.
RESPONSE 10:
We've had one dual use instrument here for a long time - actually 2 but only one at
a time. We go thru stages but right now the solids is not getting much use but it has
in the past. In those times, we would try to concentrate the solid time into Friday to
Monday as solid experiments take longer. Most of the time was taken by only two groups.
One did (and does) sophisticated bioNMR experiments and only needed intro to the equipment,
not the experiments. The other was an organic student who only did the most basic CPMAS
experiment. Other answers below.
.
For your situation, who is authorized to switch the hardware? Facility staff? Trained expert users?
For those who are going to be repeatedly using solids, then training is what we do and
is the way to go. Usually a watch-us-do-it demo and then we watch them on subsequent
switchovers until they (and we) are comfortable. This is for students who know or
need-to-know NMR, not your average organic/material/inorganic/biochemist. For those
later types, staff running the instrument is the only way to go.
. How much time does it take to switch modes?
30 min or less once you become good at it.
. Do you have a set schedule for solids/liquids modes, or is the switch done as needed?
as needed but SSNMR on or around the weekends.
. What are the major risks to hardware on a dual-mode instrument?
We've never had any problem but if one inadvertently read a solids parameter set
with high powers, it could potentially damage a liquid probe. Fortunately, the
power limitations are set in edprobe so I believe it wouldn't actually execute that
higher power but would give an error as long as you have defined the probe in edprobe!
As for solids in general, crashing a rotor is the most common risk and that will
entail sending the probe back for a costly new coil usually. Decoupling for too long
and too high a power is another.
. Do you charge different rates for solids and liquids modes? If so, how do
you perform the dual-mode accounting on one instrument?
same rate
. How do you prevent users who are only trained for liquids from trying to use
the instrument in solids mode?
Never had a problem. it's completely obvious that there is no where to put a liquid
sample when it's in solid mode.
. What other insights do you have?
solids is a pain in the ass from a managers’ POV because unless you have an NMR group
where users learn NMR and will be the ones doing SSNMR, then you will be doing the SSNMR.
Casual users will request solids and will have no idea how much different it is from
liquids and sometimes no idea what SSNMR can do or is. For example, I often get requests
for 1H SSNMR.
RESPONSE 11:
I've had a dual solids/liquids system for many years. Currently, I have
more liquids customers than solids so I leave it on liquids most of the
time.
Switching is done by staff only!
Switching takes about 15 minutes, including checking 1st sample.
Solids are by appointment and generally for several days to a week at a
time.
I haven't seen any risks.
Same rates.
None of my liquids users would dare to try solids without my permission.
Plus, the solids rotors are kept out of sight.
Funny story: users don't check the schedule, and walk up to the magnet
with a tube in hand- and can't see how to insert it with the solids
transfer tube sticking up. No, no one has actually tried to put a tube
in the solids transfer tube.
RESPONSE 12:
We have a 500 MHz spectrometer that I think matches pretty closely to your scenario.
. For your situation, who is authorized to switch the hardware? Facility staff? Trained expert users?
Switching back to solutions is only done by Facility staff.
The switch to solids involves facility staff in as much that we will remove and store
the solutions probe. Facility staff may also install one of the solids probes (we have
several for 500MHz), or this could be done by one of the few expert solid state NMR users.
With solids, it often requires more than just a change of probe, but we also have to
consider external RF filters and such. Most of the solids users are aware of what is
required, butnot all of them.
. How much time does it take to switch modes?
Realistically a few hours. People will say it can be done in less time, but that's because
they forget about all of the overhead time. For high resolution solutions, it will take a
while for the probe to stabilize in the magnetic field and come to temperature. For solids,
I always check the magic angle and do a few other routine tests every time I install a solids
probe. That takes time. Whenever possible I tend to coordinate the switchover with the regular
weekly nitrogen fill to minimize the downtime.
. Do you have a set schedule for solids/liquids modes, or is the switch done as needed?
We generally go in two-week intervals. Two weeks solids, two weeks solutions. Of course, we are
flexible, so if/when someone needs one or the other, we try to accommodate. Prior to COVID, we
stuck to this schedule pretty firmly, but things are more flexible now.
. What are the major risks to hardware on a dual-mode instrument?
We have a SampleCase installed on our 500 MHz magnet, so I worry about knocking any of those
parts with the transfer line, or whenever we change solids samples. It hasn't happened yet,
but that is one concern. I also worry about the external RF filters, especially when people
are doing solids. One other hardware issue that doesn't have anything to do with DUAL mode:
the BCU-II has failed twice on this instrument since 2019. The first one got replaced under
warranty. The second one is being looked at by Bruker service engineers (they were here for
something else anyway). This is a very expensive accessory to replace.
. Do you charge different rates for solids and liquids modes? If so, how do you perform
the dual-mode accounting on one instrument?
Yes. Solutions are charged by spectrometer time, either logged by IconNMR, or if they are
doing hands one experiments then by FACES scheduling. The solids users are changed a flat
monthly fee whether they use the spectrometer or not (they are a major user who will use all
the time they can get).
. How do you prevent users who are only trained for liquids from trying to use the instrument in solids mode?
Even those solutions users who are trained to use the spectrometer "hands-on" are not trained
to swap probes. I can't even imagine any of them would even try without first coming to me to ask about that.
. What other insights do you have?
I would definitely prefer to have dedicated solids and solutions systems, which is what we have mostly.
But this is a good compromise for 500 MHz.
RESPONSE 13:
I hope all is well; we’ve got a 500 that we use for liquids and solids, with the emphasis on
liquids, so one of us (read: staff or steward) changes to the solids probe every Thursday, and
we advertise the system as such. We can get away with 8am Thursday morning to 9am Friday morning,
and since it's a pretty small number of solids users, I build a schedule for them each week.
We don't specifically keep trained liquids users from doing solids on their own, but no one has
ever tried in 3 years - users supply their own rotors, which are expensive enough that it limits
casual or speculative use.
We can typically switch probes in an 30-45', so it's not a tremendous burden. Our solids probe is
manual tune, so we train users to tune the probe - and this is the most likely source of hardware
failure (one busted capacitor in three years). From an operational standpoint, they also learn how
to pack rotors and cap them so that their samples will spin and not get stuck in the probe. Early on,
this was something we had to learn about!
RESPONSE 14:
We have a dual-use 600 that’s usually in liquids mode for manual use (no autosampler). Generally,
only one lab uses solids, and they are all "experts". To answer your questions:
* Facility staff insert and remove the liquids probes, but the expert users in the solids
research group are allowed to insert and remove the solids probes & transferlines.
* About 15 minutes plus any time needed for reshimming or recalibrating the MAS.
* No set schedule, done as needed.
* No major risks. One minor risk is the constant removal/re-insertion of the solids transferline
can cause scratching to the bore. Also, the solids people like to use a lot of cold VT gas in our
lab so we have to remind them to turn off the shim flush gas when they are done.
* Yes, we charge more for MAS ($9 vs $5/hr). We do the accounting manually.
* This has never really come up – our liquids users don’t have access to rotors, etc.
But, we do remind our liquids users to check for the solids transferline sticking out of the
bore and to let us know if they see it there. In theory this should never happen since the
solids users are supposed to install and remove the probe and transferline at the start and
end of their booking (usually 1-2 weeks)
RESPONSE 15:
Here are some answers that I've come to doing solids/liquids changing. I'm running an AVANCE III 400 WB,
mostly solids with a Doty liquids probe. Our DMX 500 is a solution state with solids option.
* Only me. Since the 400 is primarily a solids instrument, I don't train users unless
they're going to be using it for the majority of their graduate career and beyond. Potential
breakage on the solid state probes is with the rotors (~$600 for a 4 mm, ~$1k for 3.2 and 2.5 mm)
which can cause issues at the coil and stator block (min $3k repair). Things happen often enough
with spinning issues that only experienced users should be dealing with the probes. I have one
student that I'd trust to pull a probe, but only I maintain them. The 500 is primarily solutions,
and hasn't had any call for solids work for a long time.
* Not long, actually. Bruker said for their probes, maybe 15-30 minutes. I can switch mine in
about 10 minutes now. Bear in mind, I'm not switching for bsms to eject for solutions on the 400.
That will add some time. That's found in the bsms menu of ha.
* On older instruments, previous managers here did have a set schedule. I don't maintain a set
schedule on my 400 and the 500 isn't routinely used for solids anymore.
* My colleague in the Chemistry department and I have spoken on this. We actually don't want
any of our instruments to be dual solids/liquids going forward. Even though it’s only 30 minutes
to change over everything, you are still pulling a probe and moving things around. Chances of
breakage are always higher.
* No change to rate for us. We charge by the hourly usage on the instrument, not the experiment being done.
* Are you considering opening solids to everyone that uses NMR? Training times are usually longer
for solids; I hear somewhere between 8 and 16 hours (I sit on the longer side) of training because
there's more involved in the hardware. Consider it like a biomolecular NMR experiment. There's a
lot of adjustment in the instrumental parameters and hardware. After that, there's usually a 2 week
or so period where the student is overseen by a manager before they can work alone. That's a
significant amount of effort to put in for each student. Better to leave it to staff and experienced
users. We give it as an on request system.
* If you have the option to get a stand alone solid state, I would suggest looking at that route.
I've found that because of the switching time and trainings, solid/liquid instruments are more of
a "well, we have it but it's difficult to do" and no one will want to do it as opposed to the
"we have it, so just go submit your sample." I'd also add that you should really look at the research
profile of the department and see what NMR experiments are being done in the solids literature for
that so that you can target the correct probes. If you have people that want fast MAS for getting
high resolution spectra like a solution state spectrum, you'll want to look at probes that can handle
that. Likewise, if you're looking at biomolecular solid state, you want an E-free probe that won't
overheat your sample. There's no one fits-all probe in solids because of the powers involved.
RESPONSE 16:
we have a 700 Avance Neo which we switch between solids and solution.
* For your situation, who is authorized to switch the hardware? Facility staff? Trained expert users?
Facility staff and expert users - phD students which mainly work in NMR
* How much time does it take to switch modes?
For sample case probe changer only a few minutes more than switching between probeheads of the same type.
It may work different for other sample changers.
* Do you have a set schedule for solids/liquids modes, or is the switch done as needed?
We switch on demand. But we are a small university, that may be unfavorable for larger facilities.
* What are the major risks to hardware on a dual-mode instrument?
"Never touch a running system=". The more changes to more chances to make mistakes or damage
something you carry around. And loosening/fastening all the cables and pressured gas connections
leads to faster aging. We have some problems to bring the MAS unit back to work after having
done solution measurements. But this is rather a software issue.
The different power requirements are restricted and controlled by the software, so this should not be a problem.
* Do you charge different rates for solids and liquids modes? If so, how do you perform the
dual-mode accounting on one instrument?
Yes we do. Different prices for solution and solid state measurements. Different prices for rotors,
higher risk for probehead damage in solid state, higher costs for replacement parts, pressurized gas
consumption (especially if you use N2!) and so on. But for people doing their measurements themselves
in both modes I am still looking for a good solution. It would be nice to share ideas.
* How do you prevent users who are only trained for liquids from trying to use the instrument in solids mode?
They all have to sign that the are only allowed to do things which they were trained for and for that
they have received the permission by the head ofnmr department, otherwise they have to take the costs
if something happens.
* What other insights do you have?
What I would recommend is to buy “autocalibrate” which makes all the adjustments for solution
probes automatically and to buy an iprobe also for solids if possible (they do not offer it for
700 MHz L) to have an automated MAS adjustment and some other features which help to make the
procedure more efficient for the staff.
RESPONSE 17:
I don't have very much to say, either, except that we’ve attempted to implement something
similar: we have a Varian 500 MHz VNMRS which has traditionally been our instrument for long
or interesting experiments (long 13C, VT, DOSY) and we were able to purchase solids accessories
from --- a few years ago. So I had to think about the same ideas as you. Unfortunately, I
don't have much actual data as the probe has crashed three times already! This seems to be due
to incompetence (the first time), bad luck (the second time), and a failing MAS unit (the third time).
Between each of the crashes, I had a significant mental block to get over before using it again,
which is why there hasn't been much use.
As far as the switchover is concerned, it's quick unless you want to install the Varian solids
VT stack, which is a bit finicky. However, on Bruker this isn't such an issue. When I worked
at ---, we had a narrowbore system which we switched between solids and liquids and it was
straightforward. However, until you're very confident yourself and can document the whole
switchover clearly, I wouldn't let students do it on their own. It shouldn't take more than
an an hour to switch the hardware over, set the magic angle on KBr, and reference / test
setup with glycine, once you're used to it.
Regarding timing: the plan was to coordinate with students and always sign up for solids work
long in advance. No solids over the weekend except in unusual circumstances, so that I'm
never very far away.
I don't see major hardware risks for Bruker dual-use instruments. Be gentle with hardware, of
course, as there will be more handling than usual, but I don't see any issues. For Varian,
I'm worried about the VT connector, but that's not a problem for Bruker.
For charging, I was applying our WB solids rates to the NB instrument. They're a bit less than
the liquids rates, but then experiments tend to be longer so overall usage is higher, so It balances
out. Accounting-wise, for solids we use a logbook. There's rarely more than one user per day on
solids, so although it's a bit annoying to type up the Excel spreadsheet when it comes time to do
billing, it's not a major problem. For liquids, we have a script to process the acctlog.xml file
that Varian generates.
For keeping liquids users off I use different Linux logins for the two modes (this is close to
being a requirement on Varian, although not on Bruker) so it looks a bit different. Once things
are set up, I often lock the computer screen. And I put a sign on the desk.
Overall, I think that your plan is a good one, and in fact if we get funding to get a new system,
it'll be a 500 MHz Bruker and we'll get the Phoenix kit so that we can keep using our Varian NB
probes on it, in alternation with a standard two-channel iProbe and one with simultaneous 1H and
19F decoupling. That is, assuming that the useful solids probe (3.2 mm) can be successfully repaired!
RESPONSE 18:
My experience with multiple personalities (solids, liquids, Diffusion) on a
Bruker are not encouraging. The system loses its mind and often requires
full reconfiguration. Really complicated.
I used a JEOL dual system at --- and had a great experience. I or a trained
expert user would make the switch using a written and reliable changeover SOP.
Switching probes usually takes less than one hour sometimes 30 minutes if every
step goes smoothly. The biggest delay is in rechecking power levels on the
solids probe at every install. The experts were "trained" over the course of
about 4 probe changes before given the green light to work unsupervised. We
ran solids "by request" and no more than once or twice a month for up to 24hours
(there was one exception where the project required a couple of weekend runs.
Other than exploding spinners the biggest risk was the solids user leaving the
liquids system in an unusablestate. [Our] charge scheme was flat hourly rate
no matter what was being done.
If you can get the Bruker to reliably switch under a well-documented SOP, it
should work out.
Josh Kurutz, PhD
NMR Facility Manager, Chemistry Dept.
https://voices.uchicago.edu/chemnmr/
jkurutz_at_uchicago.edu
Received on Wed Feb 23 2022 - 05:13:05 MST