Applications

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.

Brilliant Blue (BB) FCF, more commonly known as FD&C Blue #1, is the most commonly used blue dye worldwide for food and beverages. It is generally accepted as safe and non-toxic. Aside from foods labelled as organic or as free from artificial dyes, there is little objection to the use of BB at levels at or exceeding 100 μg/g in foods.This application for Misa (Metrohm Instant SERS Analyzer) is unique. The benefit is twofold — successful detection of a fluorescent dye, and a unique sample cleanup technique that permits detection of a target that does not exhibit a strong SERS signal and is present in a complex matrix. While Misa successfully detects BB in direct sampling, this application describes a simple extraction method that improves detectability of BB with Misa.

SERS (Surface-Enhanced Raman Scattering) detection of a toxic dye (Sudan 1) used to adulterate saffron demonstrates the power of MISA (Metrohm Instant SERS Analyzer) for simple, portable food authentication in this Application Note.

With MISA and MIRA, easy-to-use test kits and flexible sampling allow rapid and accurate interrogation of suspect materials with minimal time, training, and expense.

Potassium ferrocyanide (KFC) is an anti-caking compound added to table salt. Although this is a common non-toxic food additive, its spectroscopic response is representative of analogous cyanide compounds. Trace detection of other cyanides in food products is essential to the safety of consumers, as they can be toxic at oral consumption levels as low as 20 μg/g.This application demonstrates rapid trace analysis of potassium ferrocyanide in table salt with Misa (Metrohm Instant SERS Analyzer), in a simple assay format with minimal use of laboratory reagents.

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.

Carbendazim (MBC) is a common fungicide approved for regulated use in agriculture globally, outside of the EU. Most MBC is found on fruits as surface contamination, the result of sprays applied prior to harvest. The US EPA has determined that a concentrations below 80 μg/mL in orange juice are not a health risk, while the EU restricts MBC levels to 10 ng/g (from imported produce) in foods intended for baby food production.This Application Note describes a very simple test for surface MBC and provides library spectra demonstrating the sensitive detection of MBC with Misa (Metrohm Instant SERS Analyzer).

Rhodamine B is a dye utilized extensively in biotechnology and industrial applications and is one of several colorants banned for use as food additives in Europe and North America. The most common analytical methods for detection of illicit dyes in food products, GC/MS and HPLC, are laboratory-based instrumental methods that require specialized training.With Misa (Metrohm Instant SERS Analyzer), detection of trace amounts of Rhodamine B in ground cayenne pepper is quick and easy after a facile extraction procedure with minimal material consumption. Rhodamine B can be detected in cayenne powder at a concentrations as low as 10 µg/g.

Thiram is used extensively as a fungicide and parasiticide to prevent disease in crops and as an animal repellent to protect trees and ornamental plants. However, extensive toxicological studies conclude that chronic, high-level exposure can cause considerable organ damage to land and aquatic species. The US defines maximum residue limits that vary for different food crops. In contrast, the EU recently banned thiram and is moving to use pesticides that carry reduced health risks.Using Misa (Metrohm Instant SERS Analyzer), low level detection of thiram on apples is achieved with guided workflows adapted for use by diverse testers.

In 2008, a scandal was discovered in China that melamine was being deliberately added to raw milk. Thousands of young children and infants that consumed formula produced from melamine-tainted milk experienced kidney damage and death. As a result, both daily intake limits and increased monitoring of melamine in dairy products were established globally.Misa (Metrohm Instant SERS Analyzer) provides quick, easy, and robust detection of melamine in a complex food matrix. As a direct test with no additional reagents, Misa’s assay format requires minimal user training, in contrast to standard analytical tests for detecting melamine, including capillary electrophoresis, GC-MS, LC-MS, and immune-based assays.

Erythrosine B (EB), also known as Red Dye #3, is a synthetic dye approved for use in candy in the US, and in pharmaceuticals and cosmetics in the EU and elsewhere. However, rodent studies suggest that ingestion of EB can promote thyroid tumor formation. EB may also be implicated as a dietary factor contributing to hyperkinesis in children. WHO recommends a daily intake of EB less than 0.1 mg/kg of body weight.The ability to obtain fast results with a portable test platform recommends Misa (Metrohm Instant SERS Analyzer) as a competitive and cost-effective alternative to laboratory technologies (e.g., CE, HPLC) currently employed for detecting EB in foodstuffs.

Thiabendazole (TBZ) is a broad-spectrum pesticide used both as a fungicide in fruits and vegetables and for controlling parasites in animal feed. To ensure consumer safety, regulatory agencies establish maximum residue levels (MRL) for pesticide-treated crops based on their review of risk assessment studies. For bananas, which are either aerially sprayed or dipped in protectant solutions of TBZ, the US FDA reports a MRL of 3 μg/g, and the EU stipulates a MRL of 6 μg/g by weight.With Misa (Metrohm Instant SERS Analyzer), the rapid and sensitive detection of TBZ on bananas is demonstrated in formats easily adapted for food safety surveillance testing.

Malachite green (MG) is a textile dye with effective fungicidal properties, however it is acutely toxic and its metabolites persist in the flesh of fish and mammals, making it a threat to the human food chain. The EU has concluded that contaminated foods containing levels higher than 2 μg/g MG constitute a credible health risk, and several countries have banned malachite green as an aquaculture additive. Despite tight regulation, seafood products contaminated with MG continue to find their way to consumers.Using Misa (Metrohm Instant SERS Analyzer) to ensure food safety, the rapid and highly sensitive detection of malachite green is achieved in a facile assay format.

Some studies suggest that consumption of the artificial sweetener, aspartame, is correlated with increased risk for brain and hematopoietic cancers, however, others find it to be a safe food additive. Consequently, the US and EU approve aspartame as a multi-purpose sweetener with an acceptable daily intake of 40 mg/kg body weight/day. However, the clear health hazard to individuals suffering from phenlyketonuria and ongoing criticism by health food advocates continues to fuel the challenge against aspartame’s widespread use in the food industry.Using Misa (Metrohm Instant SERS Analyzer), beverage products are screened for aspartame levels with no sample preparation beyond simple dilution of a consumer product.

Paraquat is a highly effective, yet exceptionally toxic herbicide used to manage weeds in agricultural operations. In recognition of paraquat’s danger, the EU and several other countries have banned its use for any application, though the US EPA permits its limited use by licensed applicators. Despite tight regulation, paraquat continues to be produced and is liberally used as an herbicide in over 100 countries without regulatory oversight.Testing for paraquat typically requires involved sample processing and analysis by trained chemists using expensive laboratory instruments such as HPLC, CE, and LC/MS. Misa achieves trace level detection of paraquat residue in tea leaves in a fully integrated, portable, smart system for easy on-site testing by non-technicians.

Malathion is an insecticide widely used on a broad spectrum of plant species. Several studies have implicated chronic exposure to malathion in the development of certain cancers. Maximum residue limits for malathion have been enacted by the regulatory agencies of several countries: the US Food and Drug Administration sets maximum residue limits at 8 μg/g in foods, while the EU has a considerably more stringent limit of 20 ng/g.SERS is an accepted method for detection of malathion on fruit and vegetable surfaces. Misa (Metrohm Instant SERS Analyzer), which requires minimal laboratory chemicals and consumables and provides an extremely user-friendly interface, is an excellent SERS solution for trace detection of food adulterants.

Fenthion is a multi-purpose insecticide used in many countries for mosquito control. To minimize human exposure and the unintentional poisoning of wildlife, the US EPA has classified fenthion as a restricted-use insecticide. However, the widespread spraying of olive orchards in Mediterranean countries results in olive oils that occasionally exceed the maximum residue limits established for olives.Misa (Metrohm Instant SERS Analyzer) easily achieves sensitive trace detection of fenthion in spiked olive oil after a simple organic solvent extraction. This Application Note presents an excellent example of how the signal from SERS substrates can compete with the target signal at very low levels of detection.

Diphenylamine (DPA) is used as a dye fixative and antioxidant in industrial applications and as a produce preservative in agricultural operations. Food safety advocates are concerned that daily ingestion of DPA, particularly in foods meant for babies, could have negative effects on children’s health. To mitigate potentially toxic effects of DPA, both the US and EU stipulate a maximum residue limit (MRL) of 5 μg/g for whole pears and a stringent MRL of 10 ng/g for all processed baby foods.Misa (Metrohm Instant SERS Analyzer) provides a user-friendly and cost-effective alternative to traditional analytical methods used for detecting DPA in foods, such as GC-MS and GC-NPD.

Metanil yellow (MY) is an azo dye used in the manufacture of external-use products such as textiles; however, it is prohibited from use as a food additive in many countries. Toxicology studies demonstrate that ingestion of MY results in significant neurological and multi-organ damage. Despite these hazards, MY is commonly used as an illicit colorant for enhancing the visual appeal of spices and legumes, most notably turmeric. Ideal tests for such food adulterants feature methods that are selective and sensitive, yet portable and convenient.Misa (Metrohm Instant SERS Analyzer) achieves rapid and accurate detection of MY in a facile assay format.

Auramine O (AO) is an industrial dye used for a broad range of manufactured products and as a fluorescent stain for detecting acid-fast bacteria in clinical specimens. Due to its intense yellow coloration, AO is also prized as an additive for enhancing the visual appeal of illicitly processed food products. Despite bans on AO as a food additive, surveillance testing indicates its persistent use as an adulterant in foods and spices.Misa (Metrohm Instant SERS Analyzer) achieves the rapid and sensitive detection of AO in curry powder in a simple assay format.

This application note presents the Orbital Raster Scan (ORS) technology from Metrohm Raman to overcome low resolution, poor sensitivity, and sample degradation while still interrogating a large sample area.

Raman analysis of fentanyl-soaked paper, SERS detection range for fentanyl on paper, and real-world example of fentanyl identification.