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The analysis described in this poster dicusses thermometric titration as a promising method for the straightforward sodium determination in foodstuffs. Thermometric sodium titration was tested for its applicability to various food matrices such as soups, gravy and several salty snacks. Enthalpy change can be monitored as a change in temperature of the solution using a sensitive digital thermometer. The sodium determination described here relies on the exothermic precipitation of elpasolite (NaK2AlF6). The titrant is a standard aluminum solution which contains an excess of potassium ions. The titration is performed directly on a suspension of the food sample and is completed in under two minutes. The method is robust, can be fully automated and due to the highly reproducible high-frequency homogenization, copes with a variety of challenging food matrices (ketchup, instant soups, pretzels, etc.). In addition to this application note, you can find more information on thermometric sodium determination in foods in our application video available on YouTube: https://youtu.be/lnCp9jBxoEs

The Rancimat method is a widely accepted method for the determination of the oxidation stability of natural fats and oils. Its main application is quality control in oil mills and the oil processing industry. At elevated temperatures and under the exposure of air, fatty acids are oxidized. The reaction products are absorbed in ultrapure water that is continually monitored for conductivity. After an induction period with slow reaction, the formation of volatile carboxylic acids is accelerated. At that time the conductivity begins to increase rapidly. Instead of investing weeks or months, the sample can be oxidized within a few hours.The method can also be used to determine the oxidation stability of solid foodstuffs that contain natural fats or oils. Frequently, a direct determination without extraction of the fat is possible, if the fat content exceeds a minimum level. In these cases, a simple and reliable assessment of the quality of the produced foodstuff is possible.A number of fat-containing solid foodstuffs such as almonds, peanuts, peanut-flavored puffs, potato chips, muffins, butter cookies, French fries, and instant noodles were successfully tested with the Rancimat method. The experiments revealed that the comminution of the sample is one of the most important steps. The grinding procedure of the tested samples was kept as simple as possible to avoid the use of expensive milling instrumentation.

Fructose (fruit sugar) is the only ketose that occurs naturally. It is found free in a mixture with dextrose (honey, sweet fruits, tomatoes) or bound as a component of cane sugar and various starch-like carbohydrates. As fructose tastes sweeter than dextrose, it finds great use as a sweetening agent.In 1932, the polarographic reducibility of sugar was described for the first time by Heyrovsky and Smoler. The following method can be used to determine the fructose content of fruit, fruit juice and honey quantitatively.

This Application Bulletin describes the voltammetric determination of the elements antimony, bismuth, and copper. The limit of detection for the three elements is 0.5 ... 1 µg/L.

The determination of sodium with the sodium ISE represents a selective, rapid, accurate, and favorably-priced method which is described in this Bulletin. Examples are used to show how determinations can be carried out with the 692 pH/Ion Meter using either direct measurement or the standard addition technique. The sodium concentration has been determined in standard solutions, water samples (tap water, mineral water, wastewater), foodstuffs (spinach, baby food), and urine. The construction, working principles, and areas of application of the two Metrohm ion-selective sodium electrodes – the 6.0501.100 Glass membrane ISE and the 6.0508.100 Polymer membrane ISE – are explained in detail.

This Bulletin describes analysis methods for determining the following parameters: pH value, total titratable acid, ash alkalinity, formol number, total sulfurous acid, chloride, sulfate, calcium, and magnesium. These methods are suitable for the analysis of jams, fruit and vegetable juices, and their concentrates.

This Application Bulletin describes the determination of mercury by anodic stripping voltammetry (ASV) at the rotating gold electrode. With a deposition time of 90 s, the calibration curve is linear from 0.4 to 15 μg/L; the limit of quantification is 0.4 μg/L.The method has primarily been drawn up for investigating water samples. After appropriate digestion, the determination of mercury is possible even in samples with a high load of organic substances (wastewater, food and semi-luxuries, biological fluids, pharmaceuticals).

In addition to its natural occurrence in fruit and vegetables, ascorbic acid (Vitamin C) is used as an antioxidant in foods and drinks. Ascorbic acid is furthermore also to be found in numerous drugs.Ascorbic acid and its salts and esters can be determined with titration or by using polarography, for which ascorbic acid is oxidized to form dehydroascorbic acid.Bi-voltammetric or photometric equivalence point indication can be used for titrimetric determination. It must be taken into account here that only bi-voltammetric indication is independent of the inherent color of the sample. Polarography is the most selective of the methods described, as other reducing or oxidizing substances are not recorded.

Cadmium, lead, and copper can be determined simultaneously in oxalate buffer by anodic stripping voltammetry (ASV) after digestion with sulfuric acid and hydrogen peroxide. Tin present in the sample does not interfere with the determination of lead.For the voltammetric determination of tin please refer to Application Bulletin no. 176.

Cu2+, Co2+, Ni2+, Zn2+, and Fe2+/Fe3+ are determined simultaneously. Interference due to the presence of other metals is mentioned, and methods given to eliminate it. The threshold of determination is ρ = 20 µg/L for Co and Ni, and ρ = 50 µg/L each for Cu, Zn, and Fe.

This Application Bulletin describes methods for the polarographic and voltammetric determination of small quantities of chromium in water, effluent water and biological samples. Methods for the sample preparation for various matrices are given.

In the past, selenium determinations have always been either unreliable or have required complicated methods. However, as selenium is on the one hand an essential trace element (vegetable and animal tissues contain about 10 μg/kg), while on the other hand it is very toxic (threshold value 0.1 mg/m3), it is very important to cover determinations in the micro range. Cathodic stripping voltammetry (CSV) enables selenium to be determined in mass concentrations down to ρ(Se(IV)) = 0.3 μg/L.

Bromide is removed from the sample as BrCN by distillation. The BrCN is absorbed in sodium hydroxide solution and decomposed with concentrated sulfuric acid, then the released bromide ions are determined by potentiometric titration with silver nitrate solution. Iodide does not interfere with the determination.Iodide is oxidized to iodate by hypobromite. After destruction of the excess hypobromite, the potentiometric titration (of the iodine released from iodate) is carried out with sodium thiosulfate solution. Bromide does not interfere, even in great excess.The described methods allow the determination of bromide and iodide in the presence of a large excess of chloride (e.g., in brine, seawater, sodium chloride, etc.).

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.

Potentiometric titration is an accurate method for determining chloride content. For detailed instructions and troubleshooting tips, download our Application Bulletin.

As the determination of the exact content of individual glycerides in fats and oils is difficult and time-consuming, several fat sum parameters or fat indices are used for the characterization and quality control of fats and oils. Fats and oils are not only essential for cooking, they are also an important ingredient in pharmaceuticals and personal care products, such as ointments and creams. Consequently, several norms and standards describe the determination of the most important quality control parameters. This Application Bulletin describes eight important analytical methods for the following fat parameters in edible oils and fats:Determination of water content in accordance with the Karl Fischer method; Oxidation stability in accordance with the Rancimat method; Iodine value; Peroxide value; Saponification value; Acid value, free fatty acids (FFA); Hydroxyl number; Traces of nickel using polarography; Special care is taken to avoid chlorinated solvents in these methods. Also, as many of the mentioned methods as possible are automated.

In most electrolytes the peak potentials of lead and tin are so close together, that a voltammetric determination is impossible. Difficulties occur especially if one of the metals is present in excess.Method 1 describes the determination of Pb and Sn. Anodic stripping voltammetry (ASV) is used under addition of cetyltrimethylammonium bromide. This method is used when:• one is mainly interested in Pb• Pb is in excess• Sn/Pb ratio is not higher than 200:1According to method 1, Sn and Pb can be determined simultaneously if the difference in the concentrations is not too high and Cd is absent.Method 2 is applied when traces of Sn and Pb are found or interfering TI and/or Cd ions are present. This method also uses DPASV in an oxalate buffer with methylene blue addition.

Formaldehyde can be determined reductively at the DME. Depending on the sample composition it may be possible to determine the formaldehyde directly in the sample. If interferences occur then sample preparation may be necessary, e.g. absorption, extraction, or distillation.Two methods are described. In the first method formaldehyde is reduced directly in alkaline solution. Higher concentrations of alkaline or alkaline earth metals interfere. In such cases the second method can be applied. Formaldehyde is derivatized with hydrazine forming the hydrazone, which can be measured polarographically in acidic solution.

In an acidic solution (containing NH4F * HF, Al(NO3)3 / KNO3) sodium forms NaK2AlF6 which precipitates in an exothermic solution, enabling analysis by thermometric titration. Several foods were analyzed, namely bouillon, gravy, tomato ketchup, corn chips, pretzel sticks as well as crackers. The reproducibility of the results was good. After weighing in and adding solutions, samples were crushed with a polytron to ensure homogeneity in the measuring solution. Relative standard deviations were between 0.08% and 3.75%. In addition to this application bulletin, you can find more information on thermometric sodium determination in foods in our application video available on YouTube:https://youtu.be/lnCp9jBxoEs

Determination of free fatty acids (FFA) in oils.

Titration of an unfiltered suspension of the sample with a standardized solution of aluminum containing a stoichiometric excess of potassium ions in the presence of ammonium hydrogen difluoride at ~ pH 3 to give an exothermic reaction, forming insoluble NaK2AlF6. The titrant is standardized against a solution prepared from anhydrous sodium sulfate or sodium carbonate. In addition to this application note, you can find more information on thermometric sodium determination in foods in our application video available on YouTube: https://youtu.be/lnCp9jBxoEs

This Application Note describes the determination of the total concentration of sodium in precursor solutions used in the manufacturing of margarine. The solutions of the precursors are mixed with edible fats and oils to make margarine. Traces of sodium chloride and other sodium and potassium salts may be added to the margarine during this process, usually in the form of emulsifiers, stabilizers, antioxidants, vitamins, coloring agents or flavor enhancers. The analysis of the total sodium content in the precursor solutions is more efficient and cost-effective for the manufacturers than later total sodium content analyses in the final product.As a rule, argentometric titration of chloride is used for indirect determination of the sodium content of foodstuffs. The assumption behind this approach is that the chloride ions are present in a molar ratio of 1:1 with the sodium ions. This is however not the case when – as is usually the case with foodstuffs containing sodium – additional compounds containing sodium are also present in the margarine. The use of potassium chloride as a partial replacement for sodium chloride in some formulations is an additional source of error.The direct titration of sodium by means of thermometric endpoint titration (TET) eliminates these problems. TET is a direct determination method that not only takes into account the entire sodium content present in the solution but is also not hampered by the presence of potassium ions. In addition to this application note, you can find more information on thermometric sodium determination in foods in our application video available on YouTube:https://youtu.be/lnCp9jBxoEs

This application note describes the determination of the total sodium content in soy milk products. The methodology may also be applied to the determination of sodium in milk products from cows, goats and sheep. A standard addition technique is employed to permit the accurate and precise determination of sodium at relatively low levels.

This Application Note offers an easy way to determine the ammonia content in cacao nibs by using ion measurement, applying the standard addition technique in a reliable cost- and time-saving manner.

The water content of lemongrass oil is determined according to Karl Fischer. To prevent unwanted side reactions, special KF reagents for aldehydes and ketones are used and the determination is carried out at 0 ... 4 °C.

The water content of flour is determined according to Karl Fischer. To shorten the analysis times and to obtain more precise results, the determinations are carried out at 50 °C.

The water content of potato chips is determined according to Karl Fischer using the oven method (140 °C).

The water content of margarine is determined according to Karl Fischer.

Water content determination by volumetric Karl Fischer titration is one of the most important analyses worldwide, particularly when it comes to food quality. This parameter has a major influence on the growth of microorganisms, and thus indirectly affects the storability of the raw materials and final products. Consistent quality is only possible with precise measurements during the process. This measurement is performed with the Metrohm Eco KF Titrator for flour, dough, and baked goods.

Determination of chloride, nitrate, phosphate, sulfate, and oxalate in dried potatoes using anion chromatography with direct conductometric detection.

Near-infrared spectroscopy (NIRS) is a fast, chemical-free analytical method for the simultaneous analysis of density, water activity, and moisture of green coffee beans.

Near-infrared spectroscopy (NIRS) is a fast, chemical-free alternative analytical technology for caffeine and moisture analysis in roasted coffee beans and grounds.

Near-infrared spectroscopy can quickly determine multiple edible oil quality parameters simultaneously without sample preparation as shown in this Application Note.

Monitoring the iodine value in edible oil blends is crucial to produce vegetable oils with the desired properties. This Application Note displays the benefit of using the Metrohm NIRS DS2500 Liquid Analyzer for quality control in food laboratories.

Evidence of maleic acid in Asian foodstuffs led to the recall of many starchy foods because long-term consumption of maleic acid can cause kidney problems. Cyclic kojic acid is however approved in Asia, both as a bleaching additive in foodstuffs and as a preservative in cosmetics. This Note describes their simultaneous determination in a single analysis.

Separation of polysaccharides with increasing numbers of inulin units using gradient elution and pulsed amperometric detection.

Determination of polysaccharides (n glucose units) in potato starch using pulsed amperometric detection and a high-pressure gradient.

Determination of polysaccharides (n glucose units) in a plant extract using pulsed amperometric detection and a high-pressure gradient.

Nutritionally, banana fruit is a good source of mineral elements and vitamins A and C. Bananas begin the ripening process as soon as they are harvested, when they contain approximately 20-25% starch and 1% sugar. When the bananas turn yellow with some brown spots, they are fully ripened, and the ratio is completely reversed.

Maltodextrin is a polysaccharide consisting of glucose units. Maltodextrins are classified as dextrose equivalents (DE, with DE = 3–20). This application shows the determination of glucose (DE = 1), maltose (DE = 2) till maltoheptaose (DE = 7). The separation is achieved on a Metrosep Carb 2 - 250/4.0 column with subsequent pulsed amperometric detection (PAD).

Cooked Italian pasta consists of about 30% carbohydrates, mainly starch. Sugars are water soluble and therefore most of them are extracted into the cooking water. This application identifies and quantifies the extractable sugars after water extraction of pasta at 60 °C.

Adulteration in the food industry is a significant concern due to potential health risks and changes in product quality and nutrition. Detecting such adulteration is challenging, however, to ensure high-quality products, precise measurements during the manufacturing process are essential for identifying any contamination in raw materials and final products. This Process Application Note details the inline analysis of potato starch in the wheat flour manufacturing process with a 2060 The NIR Analyzer from Metrohm Process Analytics.

Instant noodles have become very popular in many parts of the world. During the production process instant noodles are deep-fried, which enables a quick preparation for the consumer. Due to their high fat content (up to 22%), instant noodles can get rancid. The 892 Professional Rancimat can be used to determine the oxidation stability of deep-fried instant noodles without prior fat extraction.

The 892 Professional Rancimat can be used for determining the oxidation stability of fats contained in solid, non-meltable foodstuffs, such as peanuts, almonds, potato chips (crackers), cookies and french fries. The crushed samples can be used directly without extraction of the fat.

Oxidation of sweet almond oil can occur over time, affecting its organoleptic characteristics. This Application Note describes the reproducible and accurate determination of oxidation stability of sweet almond oil using the 892 Professional Rancimat.

Oxidation stability is an important parameter defining the quality of tea. It also provides information about the long-term stability of the naturally included antioxidants and thus the stability of the product. However, tea cannot be measured directly with the Rancimat method, as no evaluable induction time is obtained. The reason for this is that no measurable oxidation product is formed. However, using polyethylene glycol (PEG) as carrier material, many of these samples can be directly and reproducibly measured without any sample preparation. This is due to the antioxidants that are naturally present in the sample matrix, which stabilize the induction time of the PEG. The induction time can therefore be directly related to the oxidation stability of the sample.A reproducible and accurate determination of the oxidation stability is feasible using the 892 Professional Rancimat. In this Application Notes the oxidation stability of different teas is determined in this way. More information on the Rancimat method can be found on the Metrohm website.

The freshness as well as the smell and taste of coffee depend, among other things, on the content of antioxidants. The antioxidant content is critical to set a retail price and therefore it is of great interest for manufacturers and distributors to determine it. Classically, this parameter is determined via long-term storage tests. Oxidation stability offers a fast, alternative method, which can define the quality of coffee.Using the modified Rancimat method, the oxidation stability of coffee can be determined quickly and reliably. The sample is analyzed together with polyethylene glycol (PEG). The antioxidants present in the sample matrix stabilize the induction time of the PEG. The induction time can therefore be related directly to the oxidation stability and antioxidant content of the sample.This Application Note demonstrates the feasibility of the modified Rancimat method. Using the 892 Professional Rancimat, reproducible and accurate determination of the oxidation stability of different coffees is possible.

Higher antioxidant levels mean longer product viability. The 892 Professional Rancimat determines antioxidant content in many products using a linear regression method.

In this Application Note, MISA (Metrohm Instant SERS Analyzer) from Metrohm Raman excels in the detection of the pesticide acetamiprid on commercially sold raisins. MISA is a viable alternative to analytical laboratory testing in the quest to prevent contaminated foods from reaching and harming consumers.

Determination of sulfite in ginger powder using anion chromatography with conductivity detection after chemical suppression and dialysis for sample preparation.