Trace Metal Analysis: Sample and Standard Preparation

Why Accurate Weighing is Crucial to the Analysis of Metal and Heavy Metal Inorganic Contaminants

Trace metal analysis identifies and quantifies very small amounts of metals and heavy metals in a sample. Although having some trace metals in our diet is essential for our well-being, many metals can be toxic and can negatively impact human, animal and plant health, as well the environment. Trace metal analysis is used to ensure compliance with legal requirements and regulations. In pharmaceutical, chemical and petrochemical industries, trace metal analysis is used in quality control to identify and measure metal contaminants in products such as drugs, fertilizers, cosmetics, packaging, medical devices, lubricants and catalysts. Due to the influence metals may have on different chemical reactions, trace metal analysis is also used in chemical formulation research and for improving manufacturing processes.

Determining very small quantities of potentially toxic elemental impurities such as lead (Pb), mercury (Hg), arsenic (As), cadmium (Cd), copper (Cu), nickel (Ni), zinc (Zn) etc. requires highly sensitive analytical equipment. The metals in a sample are typically measured in parts per million (ppm), parts per billion (ppb) or even parts per trillion (ppt), depending on the complexity of the sample (i.e. the sample matrix) and the analytical technique used. Common analytical methods used for trace metal analysis include atomic absorption spectroscopy (AAS), inductively coupled plasma optical emission spectroscopy (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS).

Why Accurate Weighing Is Important

The analysis of trace metals by ICP is a highly sensitive procedure. It is therefore essential that samples, reference standards and calibration standards are weighed, dosed and diluted carefully and very accurately. There are always some inherent errors in volumetric preparation of solutions and dilution series associated with both pipetting and volumetric glassware, such as Erlenmeyer flasks. Gravimetric preparation of solutions and dilutions provides a much higher degree of accuracy.

Watch the Video: Trace Metal Analysis – Preparation of Reference Standards

The analysis of trace metals using spectroscopy techniques requires the preparation of reference standards with exact concentrations of each metal potentially present. Automate such tedious and repetitive tasks: This video presents the solution for fast, efficient, and safe preparation of samples and reference standards for trace metal analysis, using gravimetric automated liquid dispensing with METTLER TOLEDO's XPR Automatic Balance. Benefit from up to 30% reduction in sample volume, automatic calculations and accurate concentrations.

Typical Workflow for Trace Metal Analysis

A general overview of the trace metal analysis workflow is provided below. The details of the individual steps vary according to the particular metal element under investigation, the sample matrix, and the selected analytical method. It is important to refer to the specific details in the relevant standard methods.

Almost all analytical methods require the preparation of a series of calibration reference standard solutions of varying concentrations. After putting the calibration solutions through the same analytical procedure as the sample, the results are plotted to produce a 'calibration curve'. This provides a basis for comparison of the results from the analysis of the sample. The reference standards used to create the calibration standard solutions must be highly pure and free from elemental impurities as this may influence the result of the trace metal analysis of the sample.

Typical Workflows to Prepare Chromatographic Analysis Samples and Standards

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 the 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

Pharmaceutical Industry

Due to their toxicity, trace metals can cause harm to the patient when ingested in a medicine as well as serve as a catalyst for the degradation of the drug. Analysis of trace metal content is therefore an essential quality control procedure in the manufacture of medicines and nutritional supplements as well as in clinical trials.

Clinical research – blood, serum, urine, tissue samples (complex matrices, viscous, high levels of C, S, P, Na, Mg, Fe, Cl)
Trace, toxic, and nutritional

Standard test methods:

Elemental Impurities - Limits (USP <232>)
Elemental Impurities - Procedure (USP <233>)
Elemental Contaminants In Dietary Supplements (USP <2232>)
Metal Catalysts or Metal Reagent Residues (Ph. Eur. 5.20)
Determination of Metal Catalysts or Metal Reagent Residues (Ph. Eur. 2.4.20)

Food and Agriculture

Metals occur naturally in the environment in soil, water and the atmosphere, which is why they are also found in our food. Having some trace metals in our diets are essential for our health, but the accumulation of heavy metals in the body can lead to harmful effects over time.

Food safety (toxic elements Pb, Cd, Hg, Cr, As)
Plants, herbs
Fertilizers, animal feed
Food, fruit, beverages (toxic, essential and macro minerals)

Standard test methods:

AOAC official methods in Food (e.g. 973.34, 974.27)
ISO Methods (e.g. ISO 6561-1:2005, ISO 6561-2:2005)
CEN published standards (e.g. EN 14082:2003, EN 14084:2003, CEN/TS 15506:2007, CEN/TS 15621:2007)

Environment

Testing for trace metals in the environment is important for the health of people, plants and animals as well as to ensure protection of the environment as a whole. National and international legislation set the limits for the maximum allowable concentrations of trace metals in the air, water and aquatic ecosystems.

Water analysis (drinking water, effluents from industrial sites)
Sea water analysis
Soil, sediment and land site contamination

Standard test methods:

Determination of Metals and Trace Elements in Water and Wastes by Inductively Coupled Plasma – Atomic Emission Spectrometry (EPA Method 200.7)
Determination of Trace Elements in Waters and Wastes by Inductively Coupled Plasma – Mass Spectrometry (EPA Method 200.8)
Metal elements analysis in soil and solid waste (EPA Method 6010)

Petroleum and Chemicals

Information on trace element concentrations in petroleum and its derivatives is important both for technical diagnostics and for specific sample characteristics. Lubricant analysis is critical to identifying contamination and wear of metals. Regular analysis of trace metals produced by engines or equipment helps identify wear and deterioration conditions.

Lubricating grease and oil
Kerosene
Naphtha
Gasoline

Standard test methods:

Determination of Metals in Lubricating Greases by Inductively Coupled Plasma – Atomic Emission Spectrometry (ASTM D7303)
Determination of Additive Elements in Lubricating Oils by Inductively Coupled Plasma – Atomic Emission Spectrometry (ASTM D4951)
Determination of Trace Elements in Middle Distillate Fuels by Inductively Coupled Plasma Atomic Emission Spectrometry (ASTM D7111)

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

How to select device for metal analysis?

For determining trace metals in water and waste water using EPA Method 200.7 and 200.8, an "analytical balance, with capability to measure to 0.1 mg, for use in weighing solids, for preparing standards, and for determining dissolved solids in digests or extracts" is required. For other applications, the required detection limit of the metal in the sample is the most important factor which needs to be taken into consideration when selecting the right balance.

METTLER TOLEDO developed GWP®, Good Weighing Practice™, as a standardized scientific methodology for the secure selection, calibration and operation of weighing equipment.

The free GWP® Recommendation service supports you in selecting the right weighing instrument according to your measurement needs. This helps you to ensure that the equipment you choose will be “fit-for-purpose”. The GWP® Recommendation report is usually integrated into design qualification (DQ) and is based on the following elements:

Maximum amount weighed
Smallest net sample weighed
Weighing tolerance
Safety Factor
Standards or regulations that must be adhered to

Cómo elegir una balanza o báscula

Do You Need Support?

Trace metal analysis requires highly accurate sample solutions and calibration standard solutions to identify and quantify the metals present in the sample. If you need any further information on selecting the right balance to meet the needs of your application or want to be sure that your current balance meets your accuracy requirements, our team of experts is here to help. Please do not hesitate to contact us.

The Challenges of Preparing Accurate Sample and Standard Concentrations

Laboratory Conditions

Trace metal analysis results can easily become skewed if samples or equipment are contaminated. Cleanliness within the laboratory is therefore paramount and working in a clean-room environment is recommended. To avoid potential sources of contamination, all surfaces and equipment should be thoroughly cleaned. Electrostatic charge must be eliminated as this can attract air-borne sources of contamination as well as cause scattering of powders being dosed. Preparing samples under a laminar flow fume hood helps to minimize the risk of air-borne contamination but the airflow can make it difficult for a sensitive balance to settle.

Fully Automated Preparation of Multi-Component Formulations (Many to Many).

Sample and Standard Preparation

Even clean sample containers and dosing spatulas are potential sources of contamination. It is therefore important to try to minimize contact of the sample with other surfaces. Accurate weighing is essential to produce the precise concentrations required to ensure reliable results. Dilution of the sample and standard solutions is also a time consuming and error-prone activity, being dependent on the use of volumetric flasks and the subjective assessment of the meniscus.

Workflow Productivity and Efficiency

Companies and laboratories carrying out trace metal analysis often have to handle large numbers of samples per day. The highly sensitive analytical procedure requires skilled laboratory analysts who are often under pressure to complete analyses as quickly as possible to satisfy the demands of their customers.

METTLER TOLEDO's Solutions for Gravimetric Standard Preparation

Automated Dispensing of One Solid Substance in up to 30 Target Vessels (One to Many)

Featured Full Workflow Solution: XPR Automatic Balance

The METTLER TOLEDO XPR Automatic Balance with a liquid dispensing module enables you to prepare highly accurate standard solutions. The automated gravimetric approach saves time and delivers outstanding reproducible results. For a full workflow solution, combine the balance with LabX™ Balance software and benefit from comprehensive data handling and sample tracking functionalities.

Eliminate Major Sources of Error

Gravimetric standard preparation involves weighing not only the solid substance but also the solvent, enabling you to prepare specific concentrations with a high degree of accuracy. The actual weight of the substance recorded by the balance is used to calculate the precise amount of solvent required to reach the target concentration. The gravimetric approach thereby eliminates major sources of error in the standard preparation process, reduces the labor requirement, and minimizes variability. Furthermore, only one container is required.

Minimize the Amount of Substances

The high degree of accuracy achievable enables small quantities of solutions to be prepared. Less material is required, so you save costs, reduce waste and minimize the impact of disposal on the environment.

Automatic Calculations and Documentation

Connecting the automated liquid dosing system to LabX laboratory software offers a full workflow solution. It provides step-by-step SOP instructions on the balance display. LabX retrieves the purity from the reference standard spreadsheet and uses the actual amount of standard dosed to automatically add the correct amount of solvent to achieve the desired concentration. All data is handled automatically by LabX and saved in a secure, centralized database to ensure full traceability. Manual documentation is no longer necessary, eliminating transcription errors entirely.

Easy System Integration

Labels can be customized to include user ID, sample ID, actual concentration, production date and expiration date. Connecting a barcode reader allows sample and reference standard IDs to be read in electronically. With the addition of a printer, labels can be printed automatically. Import/export options allow bidirectional transfer of data between existing networks, data archives, LIMS, ERP, and other knowledge-management systems.

Trace Metal Analysis Solution - Excellence Analytical Balances

XPR Analytical Balances

XPR analytical balances are the perfect choice for challenging weighing applications that require exceptional accuracy.

Reduce Risk of Contamination

The optional ErgoClip Flask enables you to dose directly into your volumetric flask. The risk of contamination is substantially reduced, transfer errors are eliminated and dosing is much faster. For easy cleaning, the full draft shield and weighing pan dismantle in seconds, and the tray underneath simply slides out. No tools are needed and all parts are dishwasher-safe. Touchless operation further helps to minimize the risk of contamination.

Eliminate Electrostatic Charges and Avoid Weighing Errors

Containers and samples, particularly powders, are prone to becoming electrostatically charged through normal handling. StaticDetect™ measures the weighing error due to electrostatic charging and provides a warning if tolerances are exceeded. In combination with the optional ionizer, you have a unique solution that guarantees static-free weighing.

Increase Productivity

Save your own weighing applications on the balance, and start them via the method library. It's quick and easy, and every analyst follows the same procedure. With fast results, right-first-time quality assurance functions and automation options, XPR analytical balances help you to improve throughput and reduce costs.

Effortless Data Management

Weight results can be saved directly to the built-in results protocol, eliminating manual transcription. Multiple connectivity options (USB, Ethernet) enable your data to be transferred digitally to your existing information system.

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Application Note: Cost-Efficient Trace Metal Analysis

Accurate sample or standard preparation is the most time-consuming part of any analysis in the laboratory. It starts to become crucial when the concentrations are as low as 0.001 μg/g, as is the case with standard solutions for Inductively Coupled Plasma (ICP) analysis. Save time and reduce the amount of standards and solvents with automated gravimetrical dispensing. Minimize the cost of the entire analysis and eliminate human error in calculations or recording and transcription of data.

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Frequently Asked Questions

FAQ - 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.

Buscar sugerencias

Trace Metal Analysis: Sample and Standard Preparation

Why Accurate Weighing is Crucial to the Analysis of Metal and Heavy Metal Inorganic Contaminants

Watch the Video: Trace Metal Analysis – Preparation of Reference Standards

Typical Workflow for Trace Metal Analysis

Know-How: Trace Metal Applications and Standard Test Methods in Various Industries and How to Choose Suitable Instruments

Pharmaceutical Industry

Capítulos USP 41 y 1251 sobre Balanzas

Garantiza el Cumplimiento con la Última Revisión 2025 / 2026

Food and Agriculture

Environment

Petroleum and Chemicals

Analytical Instrument for Trace Metal Analysis: Decision Criteria

How to Select the Correct Weighing Device

Do You Need Support?

The Challenges of Preparing Accurate Sample and Standard Concentrations

Laboratory Conditions

Sample and Standard Preparation

Workflow Productivity and Efficiency

METTLER TOLEDO's Solutions for Gravimetric Standard Preparation

Featured Full Workflow Solution: XPR Automatic Balance

XPR Analytical Balances

Product Recommendations

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Application Note: Cost-Efficient Trace Metal Analysis

Frequently Asked Questions

FAQ - 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?

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?

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?

Buscar sugerencias

Trace Metal Analysis: Sample and Standard Preparation

Why Accurate Weighing is Crucial to the Analysis of Metal and Heavy Metal Inorganic Contaminants

Watch the Video: Trace Metal Analysis – Preparation of Reference Standards

Typical Workflow for Trace Metal Analysis

Know-How: Trace Metal Applications and Standard Test Methods in Various Industries and How to Choose Suitable Instruments

Pharmaceutical Industry

Capítulos USP 41 y 1251 sobre Balanzas

Garantiza el Cumplimiento con la Última Revisión 2025 / 2026

Food and Agriculture

Environment

Petroleum and Chemicals

Analytical Instrument for Trace Metal Analysis: Decision Criteria

How to Select the Correct Weighing Device

Do You Need Support?

The Challenges of Preparing Accurate Sample and Standard Concentrations

Laboratory Conditions

Sample and Standard Preparation

Workflow Productivity and Efficiency

METTLER TOLEDO's Solutions for Gravimetric Standard Preparation

Featured Full Workflow Solution: XPR Automatic Balance

XPR Analytical Balances

Product Recommendations

Balanza Automática XPR

Balanzas analíticas

Soluciones antiestáticas para el pesaje

Explore More Content

Application Note: Cost-Efficient Trace Metal Analysis

Frequently Asked Questions

FAQ - 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?

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?

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?

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