Jump to one of the following section to explore and learn more:
- Typical workflow for trace metal analysis
- Know-How: Application and standard test methods for metal elemental analysis in various industries and workplaces
- Request free support on weighing samples and standards for trace metal analysis
- The challenges of trace metal analysis
- METTLER TOLEDO featured solution for standard preparation in trace metal analysis
- METTLER TOLEDO solution for semi-automated reference standard preparation
- FAQs - frequently asked questions on trace metal analysis
1. Calibration Standard Preparation
It is essential to use highly pure metals or chemicals to prepare the stock solution. Alternatively, high quality stock solutions can be purchased. Different metals require different preparation methods. Working standard solutions are prepared by diluting the stock solution with an appropriate solvent until the desired concentration is achieved, in accordance with the detection limits of the analyzing equipment. Depending on the stability of the stock solution, working standards are often prepared only as and when needed. When creating multi-element stock standard solutions, it is important to pay attention to the compatibility and stability of all the elements.
2. Sample Preparation
The sample preparation method varies according to the sample matrix and the analytical method used. However, most trace metal analysis procedures require the sample to be in liquid form. This may require sample treatment or digestion depending on the complexity of the sample, e.g. digestion by microwave method. Acid digestion is typically used to ensure the trace metal elements are completely dissolved.
- Prepare a stock solution of the sample
Depending on the analytical method, some sample solutions can be prepared directly without requiring preparation of a stock solution.
- Dilute the stock sample solution
The concentration needs to be suitable for the detection limits of the analytical equipment. It may require several runs to determine an appropriate dilution.
3. Sample Analysis Using the Selected Analytical Method
Using the example of the Inductively Coupled Plasma (ICP) analytical method, metal atoms in the sample solution are converted to metal ions. The different metal ions are separated and detected using optical emission spectroscopy (ICP-OES) or by plasma mass spectrometry (ICP-MS).
4. Data Analysis and Calculations
The ions detected in the analysis procedure are compared to the calibration curves enabling trace metals and heavy metals to be identified and quantified.
5. Results and Report
Know-How: Trace Metal Applications and Standard Test Methods in Various Industries and How to Choose Suitable Instruments
Food and Agriculture
Petroleum and Chemicals
Analytical Instrument for Trace Metal Analysis: Decision Criteria
If you are working according to a specific standard, the standard will define which analytical method to use. For example, determining trace metals in water and waste water using EPA Method 200.7 requires the use of an ICP-OES. In a pharmaceutical laboratory, working according to the requirements of USP Chapters <232>, <233> or <2232>, an ICP-OES or ICP-MS is recommended.
If it is not necessary for you to work according to an official standard, the most important decision criteria is the detection limit of the application. Furthermore, the needs of the application play a role in defining which analytical method is appropriate. Consideration should also be given to the complexity of your samples, the number of samples you want to measure per day and the limits of the concentration range of your samples.
How to Select the Correct Weighing Device
FAQ - Trace Metal Analysis
Frequently Asked Questions about Trace Metal Analysis
We are looking for a way to try to reduce the number of errors we get in our ICP analyses. Although we work under a laminar flow fume hood, we are suspecting sample contamination due to the nature of the errors. Can you advise?
Minimizing contamination at all steps in the process is key to successful trace metal analysis. All surfaces that samples and references standards come into contact with are potential sources of contamination. Ensure laboratory analysts follow clean-room rules, and that all equipment and surfaces are clean and dried thoroughly prior to use. Using an XPR analytical balance with the ErgoClip Flask accessory enables you to dose directly into your Erlenmeyer flask, eliminating several steps in the weighing process which could be sources of contamination.
Many of our samples and standards are in powder form. During dosing, we notice that some of the powder gets scattered over the balance. Is this because of static electricity? And, if so, what can we do about it?
When powders get scattered over your balance, this provides a strong indication that the powder and/or your sample containers have become electrostatically charged. You may also notice that the balance takes longer to settle or the figures may drift. For a comprehensive static detection and elimination system, the optional ionizing module can be installed on your XPR analytical balance. The StaticDetect™ function calculates the weighing error due to any electrostatic charges present and provides you with a warning if the error exceeds pre-define tolerances. The ionizer can be set to work automatically to remove the charge in just a few seconds. If space allows, a freestanding ionizing unit can also be placed next to your balance. Simply pass your samples and container through the unit before placing on the balance. Make sure you also take other practical precautions in your lab by wearing the appropriate clothes and shoes as well as an antistatic wristband. Increasing relative humidity also helps to prevent the build-up of electrostatic charge.
We are a testing lab and handle a large number of samples every day for trace metal analysis. How can we speed up sample and standard preparation so we can be more productive?
By attaching an ErgoClip container holder accessory to your XPR balance, you can dose directly into your sample container or flask. This one-step dosing eliminates the multiple steps that are involved with sample transfer, including tedious and error-prone back-weighing and recalculations. With outstanding weighing performance, XPR analytical balances offer fast settling times too. It easy to connect a printer to your XPR balance so you no longer need to spend time writing results or labels – and you eliminate transcription errors.
Our trace metal analysis SOP specifies that we must document all the information on the standards and samples as well as the results of the analyses. We also have to transfer them to the database on our LIMS/ERP system. We do several analyses per day so it takes a lot of time and effort and it's easy to make mistakes. Is there an easier way?
By connecting your XPR analytical balance to LabX software, all your weighing data and related process information can be handled automatically by LabX. LabX provides onscreen user guidance and saves all information in a secure centralized database ensuring full traceability. LabX is easily integrated with your company's information management system enabling bi-directional data transfer. With LabX, manual documentation and the associated transcription errors are eliminated. In addition, tasks, users and instruments can all be managed centrally.
For our trace metal analyses, we have to prepare many different the stock sample and standard solutions. The dilutions take time and we are sure that there is a high risk for error in this process. The sample is often not very stable so we also have to dispose of much of the sample solution before it gets used. How can we increase accuracy and reduce waste?
Using the automated liquid dispensing module with your XPR analytical balance gives you accurate concentrations every time. The system works by adding precisely the correct amount of solvent based on the actual dosed amount of substance to achieve the desired concentration. The same principle applies for dilution; dilution series can also be prepared faster and easier.