There are numerous areas in laboratory that you can reorganize to work leaner and safer. more
To use all functions of this page, please activate cookies in your browser.
There has been much discussion surrounding the benefits of gravimetric sample preparation during the last 12 months <1 – 5>. It has been recognised by industry organisations such as the United States Pharmacopeia (USP) who proposed an update to sub-chapter <1251> “Weighing on an Analytical Balance” in Pharmacopeial Forum (PF) Sept/Oct 2012. This proposal includes a detailed description of the steps involved in gravimetric dosing for sample and standard preparation.
Pfizer’s Analytical Research and Development Group (AR&D) in Groton, USA have embraced this new approach to sample preparation using a pioneering fully automated gravimetric sample preparation workstation. Detailed studies have been carried out which compare the differences between preparing samples and standards using manual volumetric processes and the new automated gravimetric methods.
This article presents data generated by two specific experiments performed by the AR&D group in Groton.
The solid sample used in both experiments is the non-proprietary material caffeine. The first experiment focuses on the reproducibility and precision of sample
preparation. The second experiment is a linearity study. In both experiments sample preparation is performed manually with volumetric flasks and compared with a new fully automated method, where samples are prepared on a gravimetric sample preparation workstation, the Quantos QX1 from Mettler Toledo. The QX1 workstation incorporates a 6-place microbalance for weighing of the solids and solvents with automated interchange of up to 10 solid dosing heads and 5 solvent dosing heads.
The first experiment is designed to investigate the reproducibility and precision of manual sample
preparation compared to the new automated gravimetric method.
Six replicate solutions were prepared by weighing 20 mg of caffeine and making it up to 50 ml in a volumetric flask using a 30:70 methanol/water mixture. This procedure took a total of 50 minutes. Dissolving/mixing the samples on a shaker took 15 minutes of this time, so the manual labour time is 35 minutes full-time equivalent (FTE) – 5 minutes per sample for each weighing and dilution plus 5 minutes for the diluent prep. Table 1 shows the data. The key metric is that the relative standard deviation of these samples is 1.67 % (Tab.1).
Table 2 shows the equivalent data from the automated gravimetric method. Six replicate solutions were prepared by weighing 5mg of caffeine and adding 12.5 g of the same diluent (30:70 methanol/water) directly into a vial. This procedure took a total of 30 minutes, consisting of 10 minutes preparation time (such as filling and installing powder and liquid dosing heads and setting up the sequence) with an additional 20 minutes running time.The RSD of these samples is 0.49 % (Tab. 2).
This experiment highlights three advantages of automated gravimetric sample preparation. 75 % less substance and solvent are used to prepare the sample solutions; more than 70 % of labour time is saved in the sample preparation steps and most importantly the precision is improved by a factor of more than three.
The second experiment is a linearity study. To generate the manual data, five different concentrations from 0.2
to 0.6 mg/ml were prepared in 100ml volumetric flasks, which took 60 minutes. Linear regression analysis resulted in a correlation coefficient of 0.99473.
Five unknown samples were prepared with concentrations that varied between 0.3 to 0.5 mg/mL. Table 3 indicates the actual amount of caffeine weighed into the solution (Wv) versus the amount determined from comparison with the linearity plot (Wa). The agreement between these 2 values varies between 97 and 100 % (final column) (Tab. 3).
An equivalent experiment was carried out to generate the automated gravimetric data. This time the solutions were prepared in 10g solvent rather than 100ml solvent. It took 40 minutes to prepare the solutions (plus 5 mins to set up the sequence). In this experiment, the linear regression analysis resulted in a near-perfect correlation coefficient of 0.99998 (see Figure 1).
As in the manual experiment, five unknowns were prepared with concentrations that varied between 0.3 to 0.5 mg/g with the mass of each solution recorded. (Tab. 4). The final column in the “unknowns” Table 4 indicates that the actual versus determined caffeine weights for each unknown are in 100 % agreement in each case.
The data generated during the linearity study reinforces the superior quality of the automated gravimetric approach: 90 % less substance and solvent are used; 25 % of time is saved; the correlation coefficient is improved and the unknown samples are accurately identified.
The accuracy of the samples prepared is significantly improved, which will have a knock-on effect in the
quality of the analytical results generated. The reduced labour time and amount of substance and solvent saved has the potential to have a dramatic impact on laboratory efficiency and running costs.
 „One-click sample preparation“, Joanne Ratcliff, World Pharmaceutical Frontiers, März/April 2012, S. 77.
 „Innovations in Gravimetric Preparation of Analytical Solutions: Regulatory and Compendial Perspectives“, Gregory Martin, American Laboratory, Juni/Juli 2012
 „The benefits of automated gravimetric sample preparation“, Joanne Ratcliff & Jan Prochnow, q&more, März 2012.
 „Reducing Variability and Out-of-Specification Results by Implementing High Quality Gravimetric Sample Preparation (GSP)“, Charles Ray, Klaus Fritsch, Joanne Ratcliff, ISPE, Februar/März 2012.
 On-demand-Webinare auf www.mt.com/Q-webinars: „Recent USP changes: Regulatory and quality aspects of sample preparation“; „What’s the matter with Sample Prep? Novel approaches and solutions“; „Preventing costly out-of-specification investigations“.
There are numerous areas in laboratory that you can reorganize to work leaner and safer. more
Advantages of automated liquid dosing with the LabX software compared to conventional manual preparation more
XSR balances are designed to withstand accidental overload, harsh chemicals, dust and dirt more
With the model XPR6UD5, Mettler-Toledo presents the first ultra-micro balance on the market, delivers unique 0.5μl resolution more
Balance accessories for your laboratory balance can help to simplify your processes and ensure you get the accurate results you want. more
METTLER TOLEDO has launched its new Dubai Free Zone Competence Center. This new facility will offer advanced analytical support for all industries operating in the Middle East and North Africa. It will also provide hands-on equipment training for METTLER TOLEDO’s range of products, which ar ... more
Mettler Toledo presents a special offer for 2016 - a limited-edition, full-color lab calendar. More than a way to track days and dates, this 12-month calendar will provide a series of enlightening topics devoted to ensuring weighing accuracy in all critical lab processes. Using calendar pag ... more
The English version of the q&more online portal is now available online. The q&more portal was developed in a unique cooperation between succidia AG and CHEMIE.DE Information Service GmbH, and is supported by METTLER TOLEDO. It is aimed specifically at decision-makers, and uses attractive c ... more
Lean management has expanded in scope to establish itself in corporate functions beyond production. In present-day laboratory operations, it forms a basis for optimized processes and efficient quality management, providing valuable tools for the digital transition to Laboratory 4.0. more
Weighing is one of the key activities carried out in every QC laboratory. Usually, it is one of the first parts of a whole analysis chain. As any weighing errors have the potential to propagate through the whole analysis and deliver an inaccurate final result, the United States Pharmacopeia ... more
For about 200 years, any mass given in kilograms, grams and micrograms referred to a defined artifact accessible in only a single location on earth. A small metal cylinder had represented one kilogram since the metric system was introduced in France. Its successor became world famous as the ... more
Christian Müller-Schöll, born in 1966, studied mechanical engineering at the University of Stuttgart, Germany, and graduated as Diploma-Engineer. At the ZHAW Zurich University of Applied Sciences he obtained a certificate for Integrated Risk Management. He headed the primary mass calibratio ... more
Igor Knapp, born in 1968, is a qualified computer science engineer and Team Leader for Interaction Design at Mettler-Toledo GmbH. In 1993, he successfully completed a design education at the Basel School of Design (Switzerland) and subsequently worked for more than seven years in corporate ... more
Wolfgang Boos, born in 1965, initially trained as an Information Technician before studying Technical Computer Science at Flensburg University of Applied Sciences (Germany), graduating with a diploma degree. He subsequently worked as a software developer at the Forschungszentrum Jülich, Ins ... more
MS-TS balances are reassuringly easy to use and fully support lean processes in the laboratory and on the factory floor. more
The 1 kg redefinition is part of the biggest overhaul of the International System of Units (SI) since its inception in 1960. During the last several years, Mettler-Toledo has been privileged to participate in several strategic partnerships that have contributed to the newly established and ... more
Daily weighing routines are easy and efficient thanks to the ergonomic design features of the NewClassic ME balances. Essential functionality is at your fingertips to provide you with accurate and reliable weighing results day after day. But there is more. These robust all-round balances no ... more
Over 50% of out-of-specification (OOS) results in analytical workflows are reportedly caused by sample processing and operator errors (…)
The q&more concept is to increase the visibility of recent research and innovative solutions, and support the exchange of knowledge. In the broad spectrum of subjects covered, the focus is on achieving maximum quality in highly innovative sectors. As a modern knowledge platform, q&more offers market participants one-of-a-kind networking opportunities. Cutting-edge research is presented by authors of international repute. Attractively presented in a high-quality context, and published in German and English, the original articles introduce new concepts and highlight unconventional solution strategies.
> more about q&more
q&more is supported by: