Author
Dr. Samuele Giani
Enhance your productivity by measuring five parameters with just One Click™, namely density, refractive index, color, pH, and conductivity. These properties are routinely measured in quality control laboratories around the world.
METTLER TOLEDO offers modular multiparameter systems where you choose which parameter to include. Using an autosampler, the complete workflow, including sampling, measuring, and cleaning, is fully automated. Adding an integrated barcode reader to the system for data input management improves data reliability. Barcodes on vials are scanned automatically to select the optimal measuring method for each sample and to correctly associate each sample with the correct result.
Moreover, multiparameter systems can be equipped with the laboratory PC software LabX™ for complete instrument and results management. LabX supports state-of-the-art data integrity standards like FDA 21 CFR Part 11 or EU Annex 11.
This article demonstrates the power of METTLER TOLEDO multiparameter systems with three real-life examples. Discover how METTLER TOLEDO multiparameter systems have benefited laboratories in the flavor and fragrance industry, in beer brewing, sugar refining, and more.
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Quality control labs analyze various characteristics of a product according to predefined specifications that ensure consistent quality. Often, the combination of several parameters is needed to give a conclusive assessment of a product. It therefore does not come as a surprise that many international standards and norms require the measurement of multiple parameters.
Density, refractive index, their derived values (such as specific gravity, °Brix, concentration and more), pH, conductivity, and color are just some of the parameters that comprise the many analyses run in quality control laboratories on a daily basis. METTLER TOLEDO has various multiparameter solutions for exactly this purpose.
Depending on the industry and workplace, modular systems are easily customized to support a multitude of workflows. These may range from simple systems testing single samples to fully automated high-throughput processes that determine all parameters with just one click.
Autosampling is a key process to automating workflows. The SC30 is an autosampler that supports multiparameter measurements of up to 30 samples and automatic system cleaning, for a broad range of samples, in a flow-through system. (Figure 1).
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Figure 1. A multiparameter flow-through system, connected to an SC30 Autosampler and run with LabX PC software, analyzes density, refractive index and pH, and performs spectrophotometric measurements. |
Furthermore, adding a barcode reader to the system with the SC30 Autosampler improves data reliability; all barcodes can be scanned so that the results associated with each sample are saved automatically. Rather than spending time with measurements and cleaning each instrument, operators can use their time for other tasks.
Multiparameter systems can be optimized with LabX™ PC software. It is programmed for complete instrument and results management. In addition, it supports data integrity with a full audit trail in compliance with 21 CFR Part 11.
In this article, we present three application examples from different industries to illustrate the potential uses of a multiparameter system:
1. Flavors and fragrances
2. Brewed beer
3. Sugar solutions
1. Multiparameter Analysis of Flavors and Fragrances
The global flavors and fragrances market is expected to grow due to increasing demand from industries such as F&B, cosmetics, and pharmaceuticals. Particularly, aroma chemicals such as esters are in demand and expected to maintain the largest market share, with increasing research expenditure in developing such compounds supporting market demand in the upcoming years. Characterized by their multi-component nature, flavors and fragrances are often expensive to extract or produce. As such, many producers can only spare a small amount of their flavor or fragrance samples for testing. Typically quality control measures include testing the density, specific gravity, refractive index and color.
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The METTLER TOLEDO multiparameter system combines a density meter, refractometer, and a UV/VIS spectrophotometer to test these quality control parameters seamlessly. Digital density and refractive index determinations are carried out according to the oscillating U-tube and total internal light reflection measurement principle respectively. Color measurements are additionally done with a UV/VIS Excellence Spectrophotometer, which supports the most frequently-used color scales [1]. In this example, the color scale CIE L*a*b* is used for illustrative purposes.
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Table 1. Density (d20), refractive index (nD 20) at 20.00 °C and CIE L*a*b* mean results of repeated measurements (n=10) for red, green and blue samples. Standard deviations are indicated with s. |
Method and discussion
Fragrance and flavor samples are precious. As they have volatile components, it is recommended that they be filled in hermetically closed vials to prevent loss via evaporation. We measured samples with three colors; red, green and blue respectively in a multiparameter system with flow-through sampling. In this system a sample is filled in all measurement cells simultaneously, further reducing the possibility of sample contamination and minimizing evaporation. The properties of the sample – density, refractive index and color – are determined simultaneously, processed, and integrated in a single report to simplify data retrieval and documentation.
SC30 drains the sample back into the sample vial to be stored as a retention sample, or used for further analyses. The results, summarized in Table 1, show excellent repeatability for all measured parameters. This is seen in the CIE color coordinates a* and b* that span both positive and negative values, as well as the small standard deviations of density and refractive index.
Conclusions
The METTLER TOLEDO multiparameter system combines density, refractive index, and UV/VIS color measurements in one flow-through system; an increase in efficiency that saves time and achieves accurate and repeatable results. Instead of performing each individual analysis in sequence, the parameters are all determined in parallel. The SC30 sample changer holds up to 30 samples and the sample identification and start of the corresponding analysis is automated by using the barcode reader. Automatic electronic data handling and archiving is further facilitated with LabX PC Software, which can be set to process the flow of results for quality control purposes, while at the same time generating a full audit trail of the data and meta-data generated.
2. Multiparameter Analysis of Beer
Beer is the most widely-consumed alcoholic beverage in the world and the third most popular drink after water and tea. To guarantee that final quality requirements are met and the beer is brewed consistently batch after batch, brewers analyze a number of parameters. Beer manufacturers must be able to reproduce the characteristics of the beer consistently, in sufficient quantity, and in compliance with local and international regulations. Many laboratories base their beer quality control on European Brewery Convention (EBC) or American Society of Brewing Chemists (ASBC) methods.
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MEBAK®, the central European commission for brewing analysis, develops and evaluates methods relevant for this industry [2]. In addition to specific gravity, Plato and degree Brix, formulas are available to process and combine density and refractive index results into derived quantities such original wort, and apparent and real extract – allowing brewers to assess the alcoholic content of their batch of beer.
Important quality control parameters in beer are alcoholic and extract content, as well as color and bitterness determination according to EBC, ASBC, or International Bitterness Unit (IBU). The latter are tested spectrophotometrically by means of single-wavelength absorbance measurements and further calculations. Additional substance quantifications can be of a multiplicative nature or based on the Beer-Lambert law.
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Figure 2. Seven parameters of pale lager beer were determined with a multiparameter system. Parameters obtained by density and refractometry are depicted in grey, pH in red and UV/VIS in blue. |
Method and discussion
A multiparameter system consisting of an Excellence density meter, refractometer, pH, and UV/VIS spectrophotometer was used to analyze samples of pale lager beer, yielding the results as shown in Figure 2.
In total, seven parameters were analyzed according to MEBAK methods: alcohol content, original extract and apparent extract, pH, EBC and ASBC color and bitterness. Density meters and refractometers are able to calculate and display concentrations of beer samples by means of predefined or user-defined tables or formulas. Parameters according to MEBAK can be computed directly with a polynomial of second order.
Conclusions
Beer is brewed from four basic ingredients: water, a source of starch (malted barley), brewer’s yeast and a flavoring agent such as hops; but it is the subtle differences in ingredients, additives and brewing that produce the variety in beers.
This multiparameter system is a turnkey solution for all types of beer QC analyses. The METTLER TOLEDO system comes with pre-programmed standard methods that verify quality every step of the way; monitoring the beer brewing process from fermentation to final product.
3. Multiparameter Color Determination of Sugar Solutions
Sugar manufacturing plants regularly test the degree Brix and the solution color of their sugar products as a means to evaluate product quality and concentration, as well as to determine the amount that should be blended into a mixture.
The more a sugar product has been refined, the more color it loses: it helps to think of the refinement process as a series of steps from brown sugar with a lower market value to refined white sugar with higher market value. The International Commission for Uniform Methods of Sugar Analysis (ICUMSA) is a global standards body that defines analytical methods for the sugar industry. Many ICUMSA methods are used for the determination of the color of sugar in solution (summarized in Table 2), calculated as a function of the dry substance (RDS), obtained via refractive index and absorption of the solution at 420 nm (A420nm).
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The METTLER TOLEDO multiparameter system determines the ICUMSA color of sugars as follows: first, an Excellence Refractometer measures the RDS, and a calculation automatically calculates the density of the test solution. Next, an Excellence UV/VIS spectrophotometer determines the absorbance of the sample in solution. These results are then consolidated on one instrument and the ICUMSA color is determined directly; this saves many manual calculation steps and reduces the potential for transcription errors.
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Table 2. ICUMSA methods for determining the color of sugar solutions. |
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Figure 3. ICUMSA color results for white and brown raw sugars (n=5). Dotted lines indicate the maximum absolute difference allowed for measurement repeatability, as indicated in ICUMSA GS 1/3-7 for these samples and color ranges. |
Method and discussion
The ICUMSA color of five consecutively investigated specimens of white- and brown raw sugars was determined according to GS1/3-7 [3]. Due to different solution concentrations, varying cell path lengths were used: 5 and 2 cm for White 1 and White 2 raw sugar samples respectively, and 1 cm for brown raw sugars. For all investigated sugar solutions, the repeatability of the measurements was excellent and well within the maximum-tolerated repeatability criteria (Figure 3).
Conclusions
ICUMSA color of sugar solutions is calculated as function of sugar concentration and UV/VIS absorbance: refractive index of the solution and absorption at 420 nm are measured. The sugar concentration is determined using °Brix value and specific ICUMSA formulae.
Highly repeatable results are obtained with the METTLER TOLEDO refractometer and UV/VIS instruments. Harvesting sugarcane or sugar beet is a seasonal activity, and therefore occurs during a defined and limited time of the year. Often very large harvest quantities are involved.
The juncture between these two factors poses major challenges to sugar manufacturers, since the incoming raw sugar must be rapidly processed. Effective automation solutions, such as the InMotion™ and SC30 Autosamplers increase testing throughput.
Additionally, the multiparameter system can be connected to LabX Software to process the flow of results for quality control purposes. Statistical evaluations can be used to routinely test results against a target value or tolerance, generating automatic Pass/Fail reports.
Advantages of a multiparameter system
- Measurements of different parameters with one system
- Simultaneous analysis of one sample vial, preventing the alteration of samples between individual analyses
- Higher result reliability and reproducibility, less operator dependent
- Ensuring instant data analysis, overall QC-tolerance verification with one glance
- One software for multiple instruments, allowing you to manage your data and system from one place, reducing complexity
References
[1] Basics of Color Measurement Guide with UV/VIS Spectrophotometry, METTLER TOLEDO (30416740), 2017
[2] MEBAK® Collection of Brewing Analysis Methods, Wort, Beer and Beer-based Beverages, 2012
[3] ICUMSA Method GS1/3-7
