Elemental Microanalysis Service
Introduction
The Elemental Microanalysis Service in the Department of Molecular Sciences provides CHN and CHNS elemental analysis services for both the research needs of the Faculty of Science as well as for the wider research community within Australia.
CHN and CHNS analysis provides a quick and inexpensive method to find sample purity, and when used in conjunction with mass spectroscopy and NMR data can be used to characterise a compound. The service is able to obtain accurate, reproducible data for a wide range of samples.
So, how can we help you?
Below are some typical questions commonly asked about the Elemental Analysis Service. If one of the following fails to answer your question, please feel free to contact us:
- How do I submit my sample for Elemental Analysis?
- How much will it cost me to get Elemental Analysis
- For what type of samples can I get Elemental Analysis?
- How accurate is Elemental Analysis
- What sort of Elemental Analyser does the facility have?
- How does Elemental Analysis work?
- To whom do I direct questions about the Elemental Analysis Facility?
Principle of the Method
The organic samples are packed into lightweight containers of oxidisable metal (typically tin), and dropped at preset times into a vertical quartz tube, heated to 970°C, through which a constant flow of helium stream is maintained. When sample is introduced, the helium stream is temporary enriched with pure oxygen. Flash combustion takes place, enhanced by the oxidation of the container. Quantitative combustion is then achieved by passing the combustion products over several catalysts and specialised oxidation reagents producing carbon dioxide CO2, water H2O and nitrogen N2from the elemental carbon, hydrogen and nitrogen respectively. The amount of carbon dioxide CO2, water H2O and nitrogen N2 produced is determined using frontal gas chromatography.
All results for elemental analyses are calculated based on a known value of a standard by using the K value factors calculation. This K value is determined by analysing an organic standard of a known elemental composition.
The standards used are all traceable back to NIST primary standards and the instrument is checked with NIST primary standards on a regular basis to assure day-to-day accuracy of results. The instrument is typically standardised with acetanilide.
Apparatus
Vario MICRO cube elemental analysers (Elementar Analysensysteme GmbH, Germany) with PC based data system on WindowsTM and electronic micro balance.
The instrument can be run for CHNS (carbon, hydrogen, nitrogen, sulfur) simultaneously or for the combinations CNS, CHN, CN.
Applicability
The method can be used for analysis of pure organic compounds as well as for industrial and agricultural raw materials and intermediate and final products such as oils, pharmaceuticals. The high temperature created by the combustion of the tin capsules used to encapsulate the sample also ensures a complete decomposition of metal salts and other refractory materials.
Submitting Your Samples
CHN/CHNS Submission Form
Submission forms can be obtained from Elemental Microanalysis Service in the Department of Molecular Sciences or downloaded from here:
- CHN/CHNS Elemental Microanalysis Submission Form (Internal Macquarie Users)
- CHN/CHNS Elemental Microanalysis Submission Form (All other Users)
A CHN/CHNS submission form must accompany each sample submitted. The Sample ID given on the submission form MUST be the same as the label on the sample vial.
If you mailing in your samples, please send it to the address on the submission form. If you wish to hand deliver your samples, then they can be dropped off to: Dr Aleksei Marianov, Room 221, 4WW (was F7B), Macquarie University, 2109. Directions to the building can be found here. Make sure you inform Michelle that you are dropping off samples for Chemical Analysis.
Sample Size
Typically 2 to 5 mg will be enough material for a duplicate run for CHN or CHNS. Therefore if CHN/CHNS are required, then 5-10 mg will be required. Similarly if Ash is to be determined an additional 5-10 mg will be required. In cases where you have very little sample available, it is possible to do one CHN run with as little as 1 mg for organic samples.
| Sample analysed | Amount (CHN/CHNS) | Amount (Ash) |
|---|---|---|
| Organic / Pharmaceutical samples | Minimum 5 mg | Additional 5 mg |
| Solid samples with a particle size between 0.2 to 0.5 mm diameter | About 10 to 30 mg | Additional 5 mg |
The weight required is the amount that must be removable from the sample vial - not the amount put into the sample vial. We will happily return any unused sample to you if required. If you would like your samples returned, please indicate this on the submission form and include a stamped, self addressed Padded Bag with your samples.
Other Requirements
Molecular formula, Theoretical mass percentage composition of C,H,N,S
As the calibration of instrument requires either the molecular weight and formula of the compound or the approximate theoretical percentage of each element, it is important to have listed at least a range or approximate value of the expected mass percentage composition for each element in the compound.
Sample Purity
The determination of the mass percentage of CHN elements in your sample is based upon the direct weight of the material sampled. Therefore, it is very important that samples are dry, free of foreign substances such as dust, rust, hair, aluminium foil, parafilm, and paper filter fibers (the most common contaminant). We need to know if metals, halides, or other interferences are within the sample and if they are, what are they. It is also required to specify the physical state of the compound at submission (e.g. color, crystal, liquid, melting point and molecular weight).
Sample Containers
Use a sample vial that is in proportion to the size of sample. Many small samples are lost on the walls of large vials. We can only analyse what we can get out of the vial! Do not completely cover the sample with the label - a neat label down one side or around the top of the tube enables the analyst to see what is going on inside the vial when removing the sample on a spatula.
Remember, the analyst is faced with weighing out 1-5 mg of your sample to an accuracy of ± 0.002 mg or better and needing to do so within a certain time limit (i.e. the cycle of an automatic analyser). So anything you can do to assist the analyst in this regard will result in the best outcome for all.
Accuracy
The results of an elemental analysis for carbon, hydrogen and nitrogen have traditionally been regarded as acceptable, if the accuracy of the results is within 0.3 % absolute of the theoretical value and precision of sample duplicates is within 0.2 % (due primarily to the variability in sampling), provided that the sample is both pure and homogeneous .
Typical reasons for inaccurate CHNS results are:
- there is either solvents or moisture trapped in the sample
- the sample is not homogeneous - this is major cause of duplicate runs not agreeing to within 0.2 %.
- the sample is extremely volatile
- the sample is inherently difficult to combust
Cost of Service
Experienced and committed Analytical chemists in the Chemical Analysis Facility will do their best to bring you the accuracy you need in elemental analysis with carefully documented results. Turnaround times for CHN analysis average 3-4 working days for routine single samples. An express service is available for results within hours with an advance appointment.
Results will be reported as a percentage value (i.e. grams of carbon, hydrogen, nitrogen per 100 grams of sample) and carried out in duplicate unless otherwise instructed. If you have requested same day results, we will e-mail or fax your results. Otherwise, results will be sent via Australia Post or e-mail. Please specify clearly on the CHNS submission form who should receive the results for each sample. Your samples will only be returned upon request. If you would like your samples returned, please indicate this on the submission form and include a stamped, self addressed Padded Bag with your samples.
Standard Rates for Elemental microanalysis for Macquarie and other University Users
| Clients | Fees * |
|---|---|
External academic LIEF grant members# | $ 62.00 |
External academic | $ 77.00 |
External non-academic | $ 154.00 |
* All charges are exclusive of GST and subject to change.
# University of Sydney, UNSW, University of Newcastle, University of Wollongong Australia, UTS, Edith Cowan University
After you receive your results, you will be invoiced for the analyses. The invoice contains details of appropriate payment methods including credit card and direct deposit. The invoice will be sent to the name and address on the sample submission form. If the invoice should be sent to an alternate person/address please indicate this on the sample submission form.
Contact us
The microanalysis service is under the direction of Professor Peter Karuso. The service is managed by an experienced technician.
Please contact us for further information:
Microanalysis Service
Dr Aleksei Marianov
Macquarie Analytical and Fabrication Facility
Room 221, Level 2, 4 Wally’s Walk (was F7B)
Macquarie University NSW 2109 Australia
T: +61 (2) 9850 4219
E: aleksei.marianov@mq.edu.au