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.

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.

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. 

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.

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.

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 bi-directional transfer of data between existing networks, data archives, LIMS, ERP and other knowledge-management systems. 

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.