Методики

Biogenic amines are released during the winemaking process. In wine, they are present as odorless salts. However, in the mouth their flavor is partially liberated, influencing the appearance for the wine taste. Besides this, biogenic amines have been related to lack of hygiene or poor manufacturing practices. The biogenic amines are determined applying suppressed cation chromatography.

Efficiently analyze food products with ion chromatography (IC). Discover its robust applications in quality control for beverages, food additives, and dairy.

Ion chromatography mass spectrometry (IC-MS) is a powerful tool that can handle many challenging analytical tasks which cannot be performed adequately by IC alone. IC-MS is a robust, sensitive, and selective technique used for the determination of polar contaminants like inorganic anions, organic acids, haloacetic acids, oxyhalides, or alkali and alkaline earth metals. After separation of the sample components via IC, mass selective detection guarantees peak identity with low detection limits. The inclusion of automated Metrohm Inline Sample Preparation (MISP) allows not only water samples, but also chemicals, organic solvents, or post-explosion residues to be readily analyzed without need for extensive manual laboratory work. This White Paper explains the benefits of IC-MS over IC in certain cases, the hyphenation of IC and different MS systems, as well as related norms and standards.

The Bulletin describes the determination of the following parameters in wine: pH value, total titratable acid, free sulfurous acid, total sulfurous acid as well as ascorbic acid (vitamin C) and other reductones.

Pyrimethanil is a broad-spectrum fungicide. As grapevines are susceptible to fungal pathogens, large-scale viticulture operations apply pyrimethanil as part of a mixed treatment. Although chemical analysis of wines post-fermentation finds low to undetectable amounts of residue, pyrimethanil is a suspected human carcinogen. The US FDA and EU have therefore established a maximum permissible level of 5 μg/mL pyrimethanil in finished wine products.In this application, trace detection of pyrimethanil in wine with Misa (Metrohm Instant SERS Analyzer) requires few laboratory supplies and minimal sample processing, yet returns rapid results.

Determination of sodium, potassium, calcium, magnesium, putrescine, cadaverine, and histamine in a wine sample using cation chromatography with direct conductivity detection.

Determination of coumarin and tartrazine in vodka.

Zinc, cadmium, lead, and copper can be determined in red wine after UV digestion by anodic stripping voltammetry (ASV).

The analysis of the reductants, free and total sulfurous acid, pH and total acidity of wine can be performed fully automated on an OMNIS system based on the directive OIV-MA-AS323-04B, OIV-MA-AS313-01 and OIV-MA-AS313-15.Added components like SO2 have preserving properties and affect the microbiological environment (anti-microbacterial and enzyme-deactivating), they trap fermentation byproducts such as acetaldehyde and suppress a coloring into brown. The bound and free sulfurous acid are in an equilibrium with each other and can be determined via iodometric titration. Iodometric titration is also the method of choice to quantify other reductants, such as dyes, tanning agents, degradation products of carbohydrates and ascorbic acid. Finally, the acidity of wine is an important quality parameter, which affects the color and taste of wines. The total acidity and the pH of wine can be determined on the same system. Hence, Metrohm offers an all-in-one solution for the analysis of these mentioned key parameters.

Psychoactive gamma-hydroxybutyrate (GHB) and its prodrug gamma-butyrolactone (GBL) are substances that are increasingly abused as date-rape and recreational (party) drugs. Since the non-controlled GBL converts into the illicit GHB both in-vivo and in-vitro, their legal distinction is of crucial importance.For the forensic determination of illegally added GHB and GBL in commonly consumed beverages, this work presents a simple and sensitive method that employs direct-injection ion chromatography combined with spectrophotometric detection. The method allows to trace GHB-GLB interconversion, whether in vivo or in vitro lactone cleavage or intramolecular GHB esterification, and thus complies with pertinent requirements of law enforcement agencies.

Dissolved oxygen (DO) is generally considered detrimental to wine quality, especially if introduced after fermentation, storage, or bottling. The presence of oxygen after primary fermentation and during the later stages of winemaking can enhance browning reactions, chemical and microbiological instability, and the formation of off-flavors such as acetaldehyde. Knowing the DO content in wine is important through the entire wine production process, because oxidation is a common fault in bottled wines. With the 913 pH/DO meter and the 914 pH/DO/Conductometer, the oxygen content of wine can be determined quickly and easily directly on site.

This Application Note describes the automated determination of the water content in liqueur (30% v/v) using volumetric Karl Fischer titration (MATi 10).

Beer wort is the liquid in which malt starch is converted enzymatically into sugars and is additionally flavored and preserved with hops. The most important sugars for beer brewing are maltose and maltotriose, which will be fermented into alcohol by the added brewing yeast. The composition of carbohydrates in wort is determined on a Metrosep Carb 2 - 250/4.0 column applying a Dose-in gradient to optimize resolution and duration of the analysis.

Product consistency and quality is of utmost importance to winemakers. This wine analysis evaluates nutrients and other ionic ingredients, which could potentially have deleterious effects on efficiency and production during the fermentation process. Inorganic and organic anions as acetate, chloride, phosphate, malate, sulfite, tartrate, sulfate, and oxalate are separated and quantified on a Metrosep A Supp 10 - 100/4.0 applying Inline Ultrafiltration and conductivity detection.

Monitoring the range of organic acids in wine is crucial to improve flavor and quality, and to fulfill universal standardized criteria such as the International Code of Oenological Practices. Analytically, organic acids can be properly determined with ion chromatography (IC) and suppressed conductivity detection. As a multicomponent method, inorganic acids can also be resolved which are also valuable tracers for wine quality and taste. This Application Note presents two IC methods for wine quality analysis: a fast isocratic screening method of major organic acids and anions including sulfite, and a complex monitoring method with a binary gradient to separate 15 organic acids. Inline Ultrafiltration was used for economical sample treatment.

Beer is a popular beverage consumed by millions of people for enjoyment, despite its humble beginnings as a water purification technique in pre-modern times. Brewing beer requires large amounts of water which must adhere to strict alkalinity, hardness, and pH parameters to ensure uniformity in flavor and appearance between each batch. Alkalinity is introduced by carbonates and hydroxides in water which raise and buffer the pH. Hardness, balanced to a large degree by the alkalinity, comes from Ca and Mg ions, mainly present as hydrogen carbonates. Depending on the concentration ranges, the 2035 Process Analyzer or the 2060 Process Analyzer are ideally suited for the fully automatic execution of these important analyses, as well as additional parameters like pH or conductivity. These process analyzers can signal the plant’s distribution system to correct the water chemistry, ensuring consistent product quality. In addition to alkalinity and water hardness, numerous other parameters can also be determined (pH, conductivity, etc.).

This Application Note presents ion chromatography as a precise method to analyze anions in beer as well as cations with non-suppressed conductivity. Automation with Inline Ultrafiltration is also discussed.

High-Performance Liquid Chromatography (HPLC) and Ion Chromatography (IC) are commonly used in the pharma, food, and environmental sectors to analyze samples for specific components and to verify compliance with norms and standards. However, users of HPLC may run into the limitations of this technique, e.g., when analyzing standard anions or certain pharmaceutical impurities. This white paper outlines how such challenges can be overcome with IC.

The coupling of ion chromatography and inductively coupled plasma mass spectrometry (ICP/MS) leads to a high-performance measurement system that masters several particularly challenging analyses. It enables for example reliable determination of element compositions, oxidation states and chemical bonds. This information is used, for example, for assessing the toxicity of medications, environmental and water samples as well as foods and beverages.

Non-enzymatic ethanol sensor based on a nanostructured disposable screen-printed electrode.

Methanol, often present in spirits prepared with industrial solvents like wood alcohol, can lead to blindness and even death when ingested. After an incident involving methanol-laced alcohol in the Czech Republic, they adopted Raman spectroscopy as the preferred method for identifying and quantifying methanol in contaminated spirits, following an exhaustive study using various screening tools. This Application Note discusses the reasons why Raman spectroscopy is the ideal choice for this application and shows a real-world example of Raman analysis of methanol-laced rum.

Wine sometimes contains heavy metals which can be precipitated out by the addition of potassium ferrocyanide. Generally, these are quantities of iron ranging between 1 and 5 mg, and exceptionally up to 9 mg Fe/L. Zinc, copper, and lead – in descending order of content – may also be present. To estimate the quantity of potassium ferrocyanide necessary for the «décassage of the wine», only very complicated and relatively inaccurate methods have been described until now.This Bulletin permits accurate results to be obtained easily with a simple instrumentation. The results are available in a short time.

Potassium is one of the most common elements and can be found in many different minerals and other potassium compounds. It is of importance for humans, animals and plants as it is an essential mineral nutrient and involved in many cellular functions like cell metabolism and cell growth. For these reasons, it is important to be able to declare the potassium content of food or soil to reduce problems that may arise by a potassium deficiency or extensive consumption.This bulletin describes an alternative to flame photometric method using an ion selective electrode and direct measurement or standard addition technique. Several potassium determinations in different matrices using the combined potassium ion-selective electrode (ISE) are presented here. Additionally, general hints, tips and tricks for best measurement practice are given.

It has been known for years that consuming too much nitrates from foodstuffs can result in cyanosis, particularly for small children and susceptible adults. According to the WHO standard, the hazard level lies at a mass concentration c(NO3-) ≥ 50 mg/L. However, more recent studies have shown that when nitrate concentrations in the human body are too high, they can (via nitrite) result in the formation of carcinogenic and even more hazardous nitrosamines.Known photometric methods for the determination of the nitrate anion are time-consuming and prone to a wide range of interferences. With nitrate analysis continually increasing in importance, the demand for a selective, rapid, and relatively accurate method has also increased. Such a method is described in this Application Bulletin. The Appendix contains a cselection of application examples where nitrate concentrations have been determined in water samples, soil extracts, fertilizers, vegetables, and beverages.

Currently, there are no simple tests to identify counterfeit beer. This Application Note demonstrates the ability of i-Raman EX, the B&W Tek Laboratory Raman instrument with a 1064 nm laser, with principal component analysis (PCA) to distinguish between beers from different brewers and from a mixture of beers.

Determination of copper, zinc, iron(II), and manganese in red wine using cation chromatography with UV/VIS detection after post-column reaction with PAR.

Biogenic amines and trimethylamine N-oxide (TMAO) are indicators for the quality of grape fermentation. The consumption of amine-rich wines often leads to headaches, which is why the amine concentrations in wine must be monitored. This Application Note describes the determination of trimethylamine N-oxide, putrescine, cadaverine and histamine, in addition to various standard cations, with the aid of the Metrosep C 6 - 100/4.0 column and subsequent direct conductivity detection.

Determination of the potassium content plays a major role in the food and beverage industry. Potassium is an essential mineral nutrient for humans. It is an important intracellular cation and also plays an important role in processes withincells, where it is involved in the regulation of numerous body functions like blood pressure, cell growth and muscle control.To declare the potassium content of drinks and food, it is usually determined by flame photometric method. However, flame photometry is linear only over a limited concentration range, and often sample dilution is necessary. Furthermore, the instrumentation is rather complex and expensive to buy and maintain. The ion measurement method presented here is a fast, less expensive, and reliable alternative to determine potassium content in beverages.

Sulfite is found in many drinks, dried fruit, snacks etc. It acts as a preservative and may be added artificially or can be a side product of fermentation. As sulfite can induce a health risk, it is banned in raw foods and must be labeled on processed foods. Analysis of sulfite by IC with DC amperometric detection is nearly impossible due to the food matrix which fouls and deactivates the electrode surface very fast. The new automatic CV activation procedure (CV treatment, patent pending) cleans the electrode surface and recovers its sensitivity. This report shows DC amperometric detection of sulfite in several foodstuffs applying this activation step prior to the sulfite detection.

The determination of the oxidation stability of wine with the Rancimat is a newly developed method able to determine the antioxidant potential of wines. Different grapes as well as varied processing methods impart the color, taste, and anti-oxidative capacity for each wine blend or varietal. With the Rancimat and Polyethylene Glycol (PEG) methods, the antioxidant potential in different wines can be easily compared.The PEG method is used to compare the antioxidant capacity of different vintages and grape varieties. The induction time can be used as a quality criterion for different types of wine or different vintages. In this Application Note, the oxidation stability of different wines is determined in this way.

This Application Note demonstrates the feasibility of the Rancimat method. Reproducible and accurate determination of the oxidation stability of flavored spirits is possible with the 892 Professional Rancimat.

Determination of lactate, chloride, nitrate, sulfite, and phosphate in wine using anion chromatography and conductivity detection after chemical suppression.

Determination of chloride, phosphate, sulfite, bromide, nitrate, and sulfate in a beer using anion chromatography with conductivity detection after chemical suppression.

Determination of chlorite, chloride, sulfite, and oxalate in beer using anion chromatography with conductivity detection after chemical suppression.

Determination of fluoride, chloride, phosphate, and sulfate in beer wort using anion chromatography with conductivity detection after chemical suppression.

Organic acids in wine are omnipresent in winemaking. Some of them are present already in the grape while others appear during fermentation. The sum of organic acids and their composition have a direct influence on the taste of the respective wine. In this application a wine is tested for minor organic acids, especially shikimic and iso-citric, besides typical acids and anions. The separation is performed by anion chromatography applying a low-pressure gradient to achieve the required selectivity.

For the determination of heavy metals in wine, UV digestion is required to mineralize the sample. The determination of platinum and rhodium is carried out with adsorptive stripping voltammetry (AdSV) at the HMDE.

Determination of Zn, Cd, Pb, and Cu in whiskey after UV digestion.

Zn and Pb are determined by anodic stripping voltammetry (ASV) in acetate buffer at pH 4.6.

The determination of nickel and cobalt in red wine using adsorptive stripping voltammetry can be carried out after UV digestion of the sample.

For the determination of nickel in white wine, UV digestion is required to mineralize the sample. The determination is done by adsorptive stripping voltammetry (AdSV) at the HMDE in ammonia buffer with dimethylglyoxime (DMG).

By using an enzymatic sensor with a screen-printed electrode, producers can measure lactic acid production, thereby monitoring fermentation processes.

Determination of reducing sugars in wine and candies according to Fehlings method by potentiometric/iodometric titration using the Pt-Titrode.

The alpha acid level (AA%) in hops plays a major role in the bitterness they can impart to beer. The AA% can vary between 1% up to 20% in hops. During boiling in the brewing process, alpha acids transform into iso-alpha acids which make the beer bitter. For this reason, it is important for brewers to know the exact AA value of the hops they use. The determination of AA% in hops with conductometric titration according to the EBC method 7.4 is shown in this Application Note.