Hello friends,
I got confused with the calibration room in my company. They said to me during audit that they cannot calibrate The spectrometer use to analysis chemical composition of material. What they do is to buy master sample and use it as reference point when running the equipement once a month.

Is this correct concept for calibration? If not, what should they do to comply with the calibration concept?

Thank you for your feed back.

QSMSO

That's basically it, you don't really calibrate it, you standardize the readings. Now, that is a fine line to walk, but if you make sure that your records are good, you should be ok. We standardize once per shift.

hint: teach everyone to avoid the "C" word whenever possible.

qsmso

I am sure that there are more qualified people who will chime in here, but let me take a shot.

One suggestion would be to see if the "owner's manual" is available, either at your plant or from the manufacturer. It should have some advice on working calibration.

That said, we use a similar "master sample" system weekly on our most important QC tests, just to confirm that our testing is OK. It has worked well. The Western Electric handbook has advice on how to use this method with XMR charts to maintain testing systems, and it is a valid approach.

Hope this helps, and good luck.

I agree with Steelmaiden - we call it "profiling of spectrometer" and we "profile" it once per day (minimum) against certified standards (we alloy our own aluminum).

Just curious - what kinds of Gage R&R numbers has anyone seen/submitted for a spectrometer. Mine have been anywhere in the range from 7.5-145% of tolerance, depending on the element being checked. With respect to anything over 25%, we have been able to "correct" the spectrometer and/or operator methodology to have satisfactory numbers to submit.

Bill

I have had 2 different experiences with Spectrophotometers. The first was in Blood Banking. The monthly maintenance required that a known set of standards be read by the spectrophotometer in 3 categories: Repeatability (20 times), Linearity and Drift (performance over a predetermined amount of time). These standards were supplied by the manufacturer and NEVER considered a calibration. They were an indicator of lamp stability and performance. The equipment went through a seperate validation prior to use.

The second is in the Chem lab I manage. We don't have a predetermined, colormetric standard to performance check the spec but we do run 5 standards (purchased material diluted to the appropriate concentration) with each assay performed. The readings are used to calculate a curve. The tested samples, of course, fall within this curve. This is done with each assay type being performed. Again, not a "calibration", just a performance check of how the lamp is reading and how well the material being assayed is extracted by the Chemist.

I don't think you can actually calibrate a spec unless there are some filters you can manipulate.

Hope I don't sound like a complete dolt. Have a good one.

:bonk:

Thank you for all responses. However, the master sample, that used as reference standard, needs to be calibrated or not? I am considering how to track to national standard or equivalent as 4.11.2.b(QS-9000)
The reason I asked because when I audit the calibration room, they use gage blocks to do inside calibrate of vernier gages. Those gage blocks were sent out to calibrate periodically. They can show certificate result when we need to track. So, I think they should use the same concept with master sample of spectrometer. However, they said very difficult.

PLEASE advice !
QSMSO:confused:

I was just wondering what type of spectrometer you are talking about. For analysis of chemical composition of a material it could be several instruments. Is it an Emission spectrometer or XRF spectrometer? We happen to use both of these. We have standards for both instruments that we use to make calibration curves with. Due to the type of alloys we make we could only buy a couple certified standards. We cast the rest of the standards ourselves and then analyzed them on an AA. We ran at least one of the certified standards on the AA at the same time we analyzed our own standards and this gives us tracibility. The instruments are then drift corrected, (Standardized), on a regular basis and a known sample is then run as a QA/Check standard to verify the instrument was drift corrected properly.

Hope this helps.

I'll echo sgray's and Steel Maiden's comments here. Depending on what kind of spectrometer you're running, the term calibration may not be "useful". We use XRF, and calibration means setting up an analytical program for a material using certified reference materials to make a set of calibration curves. This process is "calibration", and is done one time, unless a major change takes place with the spectrometer. Day to day "drift" is corrected for by another procedure, which is NOT calibration. A check for instrument drift is also performed, but this is not a calibration check, per se, but a drift check. This is done per the manufacturer's recommendations, and we set up tolerances in the software to tell us when a drift correction must be performed. We do run certified reference samples for daily QC checks, along with the daily drift check.

We do something very similar with our ICP. The instrument is "profiled" daily with a standard solution, and each method used is checked with a QC standard and standardized, if outside the specified tolerances.

Don't let an auditor paint you in a corner with the term "calibration" when it comes to spectrometers. Our previous lab manager let the auditor make him set up a calibration check/correction that was totally inappropriate for XRF (dealing with pressed powders), and would actually have done the opposite of the intended end, most of the time. Always talk with your instrument maufacturer on this before setting up a "calibration" procedure for a spectrometer.

Bill, I've never submitted an R&R for the spectrometers. The manufacturer suggested calculating 3 SD after about 50 runs of the drift check sample, and setting that for the limits. Regular drift correction should ensure that the spectrometer stays in those limits, barring a catastrophic failure of a part (which can be replaced and then drift correction comes back in.) We've seen this work pretty well on our main spectrometer after implementing it.

Joe

qsmso said:

Thank you for all responses. However, the master sample, that used as reference standard, needs to be calibrated or not? I am considering how to track to national standard or equivalent as 4.11.2.b(QS-9000)
The reason I asked because when I audit the calibration room, they use gage blocks to do inside calibrate of vernier gages. Those gage blocks were sent out to calibrate periodically. They can show certificate result when we need to track. So, I think they should use the same concept with master sample of spectrometer. However, they said very difficult.

PLEASE advice !
QSMSO:confused:

Yes, your master sample should be a known sample. They are known as "Certified Reference Materials", and they are generally available from your national lab, as well as several private companies.

Ryan

Ryan Wilde said:

Yes, your master sample should be a known sample. They are known as "Certified Reference Materials", and they are generally available from your national lab, as well as several private companies.

Ryan

Ryan, for many spectrometer types, that is true, but not for all. For XRF, to check the spectrometer for "drift" (or standardization check), all that is required is a sample with the desired elements in sufficient quanity, in a form that is "permanent". All you're doing is checking instrument count rates for drift from Day Zero, so if the check sample is unchanging, it will do fine without ANY certified #'s associated with it. That being said, it is still a really good idea to check the calibration curves with a CRM of the type analyzed by that set of curves.

Daily/shift/hourly correction for instrument drift is a must, but I think it's a misnomer to call it calibration with a spectrometer. It may or may not involve the use of CRM's; depends on the spectrometer type and manufacturer instructions. Calibration and recalibration (or calibration update or method standardization) DOES involve CRM's.

I just got through this subject with a supplier profile from one of our customers, who is a major Big 3 supplier. They wanted a copy of a certificate of calibration (by external calibration source) on a piece of equipment in our process that affects their product. They wanted a spectrometer calibration certificate. I couldn't give them one, because we don't get an official certificate of calibration from the manufacturer for any of our 2 different spectrometer types (XRF and ICP). When they come in to PM 2/year, they give a PM report, but they have no way to "calibrate" the spectrometer in the way a vendor like Midwest Balance would calibrate an analytical balance for us. The spectrometer vendors can't sit there and PM an instrument and then totally redo each set of calibration curves a customer has, and then run QC checks with a CRM.

Well that's what I told the customer, and our registrar, and they seem to be okay with that :)

qsmso, I'd be interested to hear what type of spectrometer(s) you are having to deal with. We investigated the proper route needed for drift correction/"calibration check", put it in our QMS, and then folowed it, with proper records, and the registrar is more than satisfied with this. That should be all that is necessary.

Joe

I got confused with the calibration room in my company.
QSMSO Hello , I'm confused too. Could anybody suggest to me the error acceptance level for spectrometer used for chemical analysis in foundry. Should be one error acceptance level for every element (C,Mn,Si,P,S,Cr,Ni, etc) or only one for the instrument. Who is able to answer obtains from me charma points :tg: By.

We have had questions about the calibration of our spectrometer in our plant also. It seems that every time a master sample is burned the machine has to be re-adjusted. We use the spectrometer to add alloy to our melt furnances and this always seems to come up as an audit issue. I have actually had to put a calibration sticker on the spectrometer every 6 months when the pm is done. I would also appreciate any thoughts on this subject.

Thanks
Dale :confused:

I spent 35 years as an analytical chemist, but no longer work in this field. However, I was involved with Optical Emission Spectrometers for about 10 years and I'm casting my mind back as to what practices we used .....

The instrument was profiled on a daily basis using setting-up samples (we didn't work shifts).

The initial calibration of the instrument had been carried out using nationally/internationally recognised standards for each programme related to a type of alloy (e.g. low alloy and carbon steels on one programme, high alloys on another, tool steels on yet another). The calibrations were carried out using the ratio % element/% base element vs the ratio of voltage element/voltage base element.

The calibration standards were certified and analysis had been carried out by a number of organisations using varying techniques. The certficates stated the standard deviation for each element. On a daily basis, we used to run a certified calibration standard applicable to each of the programees to be used - if the result for each element was within 3 standard deviations of the average stated on the certificate, then that was considered acceptable. If the result varied from the average by more than that amount, the instrument profile was carefully repeated and the standardisation rechecked - if this didn't bring the instrument back in line, then the matter would have to be ivestigated.

We used to keep a control chart for each element of the calibration standard used per programme to keep track of the variation and identify any trends.

The use of nationally/internationally certified standards in such a manner can be expensive. One route to consider is getting together with organisations in the same field, finding a reasonably large quantity of homogenous material typifying the alloy(s) you are concerned with and collaborating on carrying out exhaustive chemical and statistical analysis. An agreement would have to be reached on how to share costs, of course.

The parameter that has the greatest effect on these types of instruments on a routine basis (e.g. not power cuts, or if applicable, vacuum pump failure) is temperature - good stable room temperature control is a must.

Hope this may be of help.

Lyn

if the result for each element was within 3 standard deviations of the average stated on the certificate, then that was considered acceptable. If the result varied from the average by more than that amount, the instrument profile was carefully repeated and the standardisation rechecked - if this didn't bring the instrument back in line, then the matter would have to be ivestigated.

LynThank a lot. Anyway what Could I Write for spectrometer Acceptance level in a table like Attached

Cavanna - some thoughts that may help. In my last position I ran a Mechanical testing lab. Our tensile and Rockwell testing equipment was calibrated twice a year by an outside vendor. We verified the equipment at the beginning of each turn prior to use. For the Rockwell testers we used certified test blocks for the scale we were testing on that were provided by an external vendor, and simply recorded results in a log. If we needed to switch Rockwell hardness scales during a turn, we'd reverify after making the appropriate changes to the tester. For the tensile test equipment we used internally developed standards and SPC charts. We would pull 2 tensile specimens and plot average and range for ultimate tensile strength, 0.2% offset yield strength, and % elongation over a 2" gauge length.

Our chemistry laboratory also used spc charts and standards to verify prior to the beginning of the turn, depending on the grades of steel being produced. (We produced electrical steels, PH grades of stainless steel, 300 series grades of stainless, and 400 series of stainless.) Some of the standards used were purchased and traceable to NIST (The US government body responsible for standards, measurements, etc.) Others had been developed through interlaboratory cooperative testing arrangements. (One lab would take it upon itself to produce a set of samples that were sent to other producing using labs, and they would do multiple rounds of analyses until a consensus agreement was reached regarding the level of various elements in the sample. Then all labs would use the new standard as part of their verification/calibration activities.) For carbon and sulfur, we typically used special analyzers developed by Leco that were more accurate than a spectrometer in the ranges we measured. Standards for verification of Leco instruments were purchased from Leco.

For your spectrometer, I'd probably be interested in seeing accuracy versus analytical ranges by element. For example: iron based alloys, Cr range of 0.40 % to 18.00 % with an accuracy of+/- 10% of reading over the entire range, or whatever might be appropriate if accuracy varies over the range of alloys you produce.

To help quantify lab competency, our chem lab took part on a regular basis in interlaboratory comparison testing that was managed by an external company, whose whole business was managing and reporting interlaboratory tests for many different types of labs. I used the same service for both tensile and B & C scale rockwell hardness testing. Hope the info helps some.

If you're looking at providing some NIST traceability for a 96 well microtitre plate spectrophotometer, Molecular Devices provide an interesting product. Here's the link to their SpectraTest product:

http://www.moleculardevices.com/pages/instruments/spectratest.html

I've used it. You need to check what the wavelengths are that it offers reference for and make sure that those are the wavelengths that you use.

It appears that at least some of the discussion centers around the items used to check the spectrophotometer.

As has been stated, these are generally a CRM (Certified Reference Material) or SRM (Standard Reference Material). These should be available from the National labs.

If the Thai National lab does not have CRM/SRM for the use, then look at the APLAC (Asia Pacific Laboratory Accreditation Cooperation) for suppliers of CRM/SRM or APLAC signatories that accredit suppliers of CRM/SRM. Those accrediting bodies will have lists of the accredited labs. http://www.aplac.org

Consensus standards (e.g. Rockwell blocks used as an example) have also been mentioned. At times the consensus standards are necessary, but they tend to be non-traceable.....just something to watch for.

Hershal

We have had questions about the calibration of our spectrometer in our plant also. It seems that every time a master sample is burned the machine has to be re-adjusted. We use the spectrometer to add alloy to our melt furnances and this always seems to come up as an audit issue. I have actually had to put a calibration sticker on the spectrometer every 6 months when the pm is done. I would also appreciate any thoughts on this subject.Thanks Dale :confused:

We also use spectrometers in the foundry for receiving metal inspection and melt chemistry.

Most auditors/customers have no idea what the equipment is or how it works so they just ask for "calibration records"

I have a set speech about this...It takes about 5 minutes to educate them. Some can't be educated so I just show them the cert for the masters to shut them up.

Another thing to consider is inter lab correlation studies. How do your burns compare to your supplier, customer, and competitors?

ASTM has several programs

http://www.astm.org/cgi-bin/SoftCart.exe/STATQA/index.html?L+mystore+frvt4284+1110356023

Consider asking your raw material supplier about this..they would likely love to help. We work with our Aluminum ingot suppplier and they are all over this topic..they have experts in this...people who do nothing but this.

It is fascinating and humbling to get involved in this...there is a lot to know about spectrometers and the test sample. Every little thing matters.

Good luck!

Caster,

Great reply.....have you considered putting in to deliver a paper at Measurement Science Conference (MSC)?

http://www.msc-conf.com

If you have not, then let me encourage you.....of course this type of equipment is a bit unique, but then, Metrologists love strange toys......... :agree1:

Hershal