Automated gravimetric liquid dispensing is a more accurate and efficient method of preparing standards or samples in an analytical laboratory compared to volumetric measurements.
Accurate preparation of samples and standards is a fundamental starting point for any analysis in analytical, quality control or testing labs in pharmaceutical, chemical or food industry sectors, to name a few.
To achieve this, a sample or standard must be accurately weighed on an appropriate balance. The precise amount of solvent must then be added to make up to the required concentration.
Errors can creep in if the importance of this initial step is underestimated or correct weighing protocols are neglected. Any errors or variability introduced during this first step may be carried downstream, for example, through dilution series. This will affect the rest of the analytical process and potentially lead to errors in the final results.
The potential effects of mistakes can be significant and result in:
Automated gravimetric solution offers a resolution to the potential issues mentioned.
Forget the old and tedious was of preparing dilution series using pipettes and volumetric flasks. Watch the video to see how fast and easy gravimetric dilution is with METTLER TOLEDO's XPR Automatic Balance.
Manual processes can expose the operator to hazardous or toxic solvents and compounds. The XPR Automatic Balance offers automated liquid dispensing, which minimizes the likelihood of spillages and exposure risks during sample and standard preparation. This improves safety and reduces balance cleaning requirements, potentially saves time.
Automated solvent dispensing improves throughput by avoiding repetitive, time-consuming manual weighing and dilution steps. Standard solutions can be prepared faster without multiple dilution series, using the XPR Automatic Balance, it is possible to achieve a dilution factor of 10,000 in a single step.
Accuracy is key in any analysis. Automated solvent dispensing helps ensure preparation of consistently accurate solutions by automatically calculating the amount of solvent needed to achieve the target concentration. It reduces interference from environmental influences as well as inter-operator variability, and helps avoid human errors during the preparation of solutions, calculation of concentrations, and recording of data.
Manual errors in data recording and transfer – balance terminal to lab notebook to spreadsheet and then LIMS – are eliminated. When using a XPR Automatic Balance, data is fully traceable and easily retrieved for audit purposes.
It is universally accepted that a gravimetric measurement is intrinsically more accurate than a volumetric measurement. In fact, pipettes and volumetric measuring equipment are calibrated using gravimetric methods. In a fully gravimetric system, the user defines the concentration required and the target amount of solution. The system software calculates the target amount of a solid to dispense and then delivers the appropriate amount of diluent to prepare an extremely accurate and precise concentration according to the actual amount of solid dispensed. In a liquid dispensing system, the software calculates the required amount of diluent according to the actual amount of solid dosed manually; the result is still a highly accurate concentration. Implementing a gravimetric sample preparation system reduces laboratory errors and Out-of-Specification (OOS) incidents by up to 50 percent, while simultaneously increasing laboratory efficiency and reducing waste.
Would you like to prepare standard solutions faster and avoid repetitive, time-consuming manual weighing and dilution steps? Do you want to prepare highly precise concentrations down to 0.1 mg/g in just one step? Do you want to reduce potential errors in the calculation of concentrations and recording of data?
For further information or support regarding automated solvent dispensing, our team of experts is here to help. Please do not hesitate to contact us.
The XPR Automatic Balance is the ideal partner for accurate solution preparation. Combined with the liquid dispensing module, it makes gravimetric sample preparation highly accurate and simple to achieve.
The key advantages to the automatic approach are:
A METTLER TOLEDO XPR Automatic Balance equipped with a liquid dosing module enables you to prepare highly accurate standard solutions and dilution series. For a full workflow solution, it can be combined with LabX™ laboratory software, offering the benefits of comprehensive data handling and sample tracking functionalities.
LabX provides step-by-step SOP instructions on the balance display. 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.
Labels can be customized to include user ID, sample ID, actual concentration, production date and expiry date. Connecting a barcode reader allows sample and reference standard IDs to be read electronically. With the addition of a printer, labels can be printed automatically.
Preparation of pesticide standard solutions for pesticide residue testing by LC-MS (liquid chromatography-mass spectrometry) or GC-MS (gas chromatography-mass spectrometry), where each sample needs to be analyzed for several hundred different pesticides at a time.
Preparation of samples and standards for trace metal analysis by ICP-MS (inductively coupled plasma-mass spectrometry), where accurate concentrations are critical when concentrations are as low as 0.001 µg/g.
Preparation of pesticide standard solutions for pesticide residue testing by LC-MS (liquid chromatography-mass spectrometry) or GC-MS (gas chromatography-mass spectrometry), where each sample needs to be analyzed for several hundred different pesticides at a time.
Preparation of honey samples for food authenticity testing, where weighing of a specific amount of a very viscous substance to prepare an accurate concentration is a challenging task.
Gravimetric sample preparation is weighing the sample, either manually or automated, and then delivering the required amount of solvent to achieve the desired concentration. The solvent amount is calculated automatically based on the actual amount of sample weighed, and measured by weight. Gravimetric dosing is referenced in USP chapter 1251 Weighing on an analytical balance as a type of weighing typically used for sample or standard preparation.
A major advantage of automated systems is that without the need of a human operator. This allows to extend the working time of your lab to 24h a day.
Standard solutions are traceable when prepared on the XPR Automatic Balance because the amount of standard weighed and the amount of solvent added is recorded automatically. The resulting concentration is also calculated automatically. This information, along with all relevant metadata, is stored electronically or exported as required, making the standard preparation process fully traceable.
If you consider USP requirements for analytical weighing and data integrity by following the ALCOA+ framework, it is important to ensure that the balance you are using is appropriate for the amount you need to weigh out. You must respect the minimum weight specification and keep within the safe weighing range for your laboratory environment. The GWP Approved function on the XPR Automatic Balance will show you whether the minimum weight requirement is adhered to or not. For data management, the powder weighed is identified by the RFID chip in the dosing head to avoid errors, and the weight dispensed into each vial is recorded automatically and can be exported with all necessary metadata if required using LabX laboratory software. All this data is included in the audit trail for full compliance with regulations.
A concentration in mg/g can be converted to mg/ml, and vice versa, using a simple density conversion (density = mass/volume). However, if a standard calibration curve is generated in mg/ml to start with, then the conversion is unnecessary because the sample concentration is measured relative to the calibration curve.
