In the food research and production field, system complexity is increasing and several new challenges are emerging every day. This implies an urgent necessity to extract information and obtain models capable of inferring the underlying relationships that link all the variability sources which characterize food or its production process e.
The aim of this chapter is to offer the reader an overview of the most significant tools that can be used in a preliminary, exploratory phase, ranging from the most classical descriptive statistics methods, to multivariate analysis methods, with particular attention to projection methods. For all techniques, examples are given so that the main advantage of these techniques, which is a direct, graphical representation of data and their characteristics, can be immediately experienced by the reader.
Read more Read less. English Similar books to Chemometrics in Food Chemistry: Each day we unveil a new book deal at a specially discounted price - for that day only. See today's deal or sign up for the newsletter. Product description Product Description In the food research and production field, system complexity is increasing and several new challenges are emerging every day.
Kindle Edition File Size: An interesting technological progress, for both the electronic nose and eye, is the use of a smartphone to detect colour variation instead of using a scanner. The idea is to have an app that can extract RGB red, green and blue values of a picture taken by the smartphone camera after which the results are analysed, preferably with the same app, thus making the technology more portable. In light of these developments, this review aims to show the reader results that have been published from until , regarding the development of new methods that can be used as field tests for both screening tools and confirmation tests.
The article selection process was not only based on procedures already developed for forensic portable tests, but also on electrochemical analysis applied to forensic content, since these techniques have a high potential to become field tests, as already mentioned.
This approach was chosen to show the huge variety of promising new methods that could be applied to in-field and remote analysis, offering enormous value to forensic science. Is not our intention with this survey to undertake an exhaustive review of the literature, but rather to give an insight into the new trends in forensic analysis. Because of this, the reader is frequently directed to prior reviews on specific topics for a broader view of a particular subject.
Eight topics on forensics were chosen for this review: Due to the enormous number of publications found that relate to explosives and beverages, not all of the existing literature was covered. Nevertheless, it has come to our attention that, even with such a broad range of subjects, that there is still much work to be done in the field. In recent years, different groups have used corona ionization sources, obtaining very good results for explosives detection, such as 2,4,6-trinitrotoluene TNT , cyclo-1,3,5-trimethylene-2,4,6-trinitramine RDX , 27 pentaerythritol tetranitrate and cyclo-1,3,5-trimethylene-2,4,6-trinitramine.
Electrochemical techniques intrinsically present portability characteristics as one of their benefits, together with low cost and possibility of detecting electroactive explosive compounds such as TNT 2,4,6-trinitrotoluene. Recently, Silvester et al. This point needs to be highlighted at this section: Another very clever approach reported in the literature 35 relies on the concept of the electronic tongue to extract electrochemical information relating to three explosives, RDX, TNT and PETN, using a screen-printed carbon electrode.
The authors combined this information with chemometrics to quantify the three reported explosives in a single measurement; this represents an unprecedented method with electrochemistry application, which indicates the possibility of understanding crime scenes containing more than one explosive.
This multi-element determination helps to solve the false positive issue, which has been claimed to be an obstacle for the implementation of in-field electrochemical detection. Colourimetric detection presents some characteristics that are suitable for use in crime scene investigations such as low-cost, portability and, in some cases, the absence of an instrument to detect the presence, or not, of the analyte at the scene. Another new direction in the forensics field is the application of colourimetric sensors as a security screening for explosives detection using paper-based devices.
Additionally, the quantification ability of the proposed method was such that it could detect 0. Additionally, electrochemical detectors were associated with portable paper-based analytical devices in order to reach lower limits of detection than those achieved by colourimetric methods, as reported in the pioneering work of Dungchai et al. Similar to this Raman portable instrumentation, portable microchip electrophoresis ME analytical devices have emerged as promising platforms for quick screening and on-site monitoring.
They are powerful tools for forensic applications, especially due to their sample-in—answer-out capabilities, as is also possible with the Raman approach. In this field, Ueland and colleagues 45 reported the analysis of trinitrobenzene, 1,3-dinitrobenzene, 2,4,6-trinitrotoluene, methyl-2,4,6-trinitrophenylnitramine, 3,4-dinitrotoluene, 2-amino-4,6-dinitrotoluene, 4-amino-2,6-dinitrotoluene and 2,4-dinitrotoluene in soil samples using commercial ME devices coupled with laser-induced fluorescence detection.
The extracted target compounds were separated in their neutral forms by micellar electrokinetic chromatography MEKC on ME devices. Electrochemical techniques in this field have been attracted a great deal of attention and could be among the most used detection techniques for portable and miniaturized devices in this field due to their unique characteristics: However, the detection of more than one explosive in a multi-detection system will be one of the challenges for the future when trying to manufacture an e-tongue or e-nose system, as reported by Wang and co-authors 35 and the combination of an array of chemical sensors could be one of ways to bring about such devices in the future, or alternatively combining multiple detection systems in order to avoid the electrochemical disadvantages, i.
The organic components OGSR originate from the primer, burned and unburned powder can contain propellants, e. They contain nitrate and nitrite, originated during the decomposition of the organic components, and metallic particles formed with vapour condensation. A more extensive list of the possible constituents of GSRs can be found in the literature. They found compounds reported in the literature associated with OGSR and were able to reduce this number to 20, based on their forensic relevance with respect to the confirmation of GSR materials.
The GSR particles can be deposited onto the hands mainly onto the index finger and thumb , face, clothes of the shooter, the victim and the surroundings, bones and hair. Taudte and coauthors 65 discussed protocols for GSR collection, while the specific use of adhesive stubs and swabs embedded in different solutions was revised by Reid et al. Since GSRs are composed of such different types of substances, an important issue in GSR analysis is the possibility of obtaining false positives due to the presence of such compounds from other sources, such as fertilizers, machine operation, urine, fireworks among others.
Several reviews about analytical techniques applied to GSR analysis have already been published: Focusing on a particular technique, the analysis of GSR has also been the subject of other reviews, and these provide an extensive panorama of the different techniques used to analyse GSR along with the pros and cons of each. Recently Doty and Muro et al. Concerning the focus of this paper, we added the year in our time period since many articles found were dated to this year and we would like the reader have a more informed view of the subject.
Due to its intrinsic portability characteristic and the possibility of coupling with chemometrical tools to create electronic tongues, electroanalysis is presented here as a powerful tool to detect GSR. Potential false positives were also studied, i. They screen printed the electrodes onto a nitrile finger cot index finger and they coated another finger cot thumb with an ionogel electrolyte layer. After swabbing the GSR particles with the index, both fingers were placed in contact to create the solid state electrochemical cell and thus to perform the voltammetric measurements.
After the creation of heavy metal free ammunition, some articles were published focusing on the synthesis of luminescent materials, i. This approach could make GSR detection at crime scenes extremely easy and cheap. In the latter work, an extensive analysis was performed: They concluded that a wavelength of nm was the optimum value for such analyses. The literature covered in this section shows that portable GSR analyses are being performed using two different approaches: Within the electrochemical sensors, some interesting studies have been performed, especially regarding the development of electronic tongues.
However, this approach still requires some degree of sophistication to screen print the electrodes and to produce the ionogel electrolyte layer. A possibility for future studies could be the development of intelligent electrochemical devices on paper substrates. Regarding luminescent detection with the LnOFs, these present a very simple, low cost and fast analysis for the detection of GSR particles, however, the results are dependent on how the ammunition was manufactured, which makes the technique unfeasible for situations in which homemade ammunition was used.
Moreover, the authors believe that the development of a colourimetric detection technique using cheap substrates to target various GSR components could represent the future in this subject. Contaminants possibly found in the fuel ethanol or bioethanol are: From these compounds, methanol may be purposely added into the fuel due to its lower cost, similar properties to ethanol and difficulty of its fast visual detection in the presence of ethanol.
However, methanol can cause severe health effects on users and overall on the attendants of gas stations and thus it is not used as a fuel. Hence, methanol can be considered as an adulterant in fuel ethanol and its control is recommended by gas chromatography GC in accordance with ASTM and other regulatory agencies. Nevertheless, a GC method is not easily executed in the field e.
Concerning the focus of this paper, we also added the year of to our time period, since many articles found were form this year and we would like the reader have a more informed view of the subject. Electroanalytical methods can be easily adapted for the on-site quality control of fuels, some commercially available instrumentation and miniaturized analytical systems have been reported in the literature, as highlighted in reviews devoted to the electroanalysis of fuels.
Alternatively, the amperometric determination of ethanol in fuel ethanol samples using a batch-injection analysis BIA system with a gold electrode in an alkaline medium has been reported as a possible alternative to identify adulteration of ethanol fuel. Moreover, this method was applied for ethanol determination in gasohol a mixture of gasoline with ethanol samples.
Anhydrous ethanol is an antiknock agent added to gasoline and is considered an environmentally friendly substitute to lead- and manganese-based additives. At gas stations, a recommended method of the Brazilian regulatory agencies to identify an excess of ethanol in gasohol is based on the volume increase after extraction with water. Nevertheless, this method cannot identify whether solvents other than ethanol have been added to gasohol. Therefore, ethanol quantification in such samples can provide strong evidence of possible adulteration of gasohol. The amperometric determination of ethanol in gasohol using copper electrodes in an alkaline media , was reported.
The combination of voltammetric analysis with copper electrodes in alkaline conditions and with multivariate analysis was demonstrated to be suitable for the detection of adulteration of ethanol fuel with methanol. A compact sensing device based on capacitance measurements to detect water in ethanol fuel samples was reported. The simple instrumentation required for capacitance measurements may facilitate the development of a sensor or array of sensors being placed inside the fuel tank.
Other technique that can be combined with chemometrical tools to develop analytical methods able to detect ethanol fuel adulteration with methanol is Fourier transform infrared FTIR spectroscopy. FTIR spectroscopy and multivariate calibration were also applied to quantify residual oil or solvents as adulterants in biodiesel and biodiesel blended with diesel oil. A laboratory-made photometric device was developed to monitor the adulteration of ethanol fuel with water. The use of a photothermal chamber with a transparent transducer and a diode laser as a radiation source was applied to determine the water content in ethanol fuel samples; this method is based on changes in sample temperature due to non-radiative relaxation of water molecules after absorption of radiation incited by the laser.
A microwave sensor based on a microstrip antenna coated with single-walled carbon nanotubes was reported to detect water in ethanol fuel. This sensor enabled fast, in situ , compact, integrable and real-time analysis of ethanol fuel samples without poisoning or drift. Regulatory agencies typically recommend the Karl Fischer titration method to determine the water content in fuels but it is not easily adapted to on-site measurements. Therefore, these sensors and devices offer a promising future for on-site and fast analysis of fuel adulteration with water. A nanoporous silicon microcavity sensor able to detect adulteration of diesel oil or gasoline petrol with kerosene has been reported.
The authors verified a linear correlation between the kerosene concentration and the variation of the refractive index. In order to discourage adulteration of gasoline and fuel ethanol, some organic dyes makers are deliberately added into these fuels. Electroanalytical methods can be applied for the detection of such organic dyes in gasoline and diesel fuel. Ethanol fuel samples can be analysed after simple dilution in supporting electrolyte while gasoline and diesel fuel required a solid-phase extraction to eliminate sample matrix.
Most of the portable analytical methods employed to discriminate or detect fuel adulteration rely on electroanalytical or FTIR spectroscopic methods. Portable instrumentation capable of executing both techniques are commercially available or can be adapted for in-field analysis. Electroanalysis can detect adulterants in a sensitive and, in some cases, selective manner. On the other hand, FTIR spectroscopic methods can obtain a wide range of chemical information from fuel samples and their combination with chemometrical tools allows sample classification. Electronic noses or tongues using electrochemical detection also offer attractive strategies to detect fuel adulteration with chemometrical tools and portable devices are commercially available for different applications, mainly for food control, as will be discussed in a further section.
On the other hand, analytical methods devoted to the identification of biodiesel adulteration are scarce. FTIR spectroscopic methods were able to classify biodiesel samples that may contain unreacted oils or residual solvent and also to identify the oil source used for biodiesel production. Regulatory agencies worldwide control several physical—chemical parameters of biodiesel before its blending with diesel oil; however, at the moment, there is no legislation regarding the oil source used for biodiesel production.
Chromatographic methods are widely used for the analysis of forensic evidence and can be associated with different types of detectors, such as UV-vis, electrochemical and, mainly, mass spectrometry MS. Over the past few years, efforts have been made to reduce the gap in on-site drug of abuse identification and herein we describe some recent contributions of portable or potentially portable methods to three forensic strands: Since the reintroduction of paper as a portable and inexpensive platform for chemical sensing, many applications in forensics have been addressed.
A portable paper-based device for morphine detection using antibody Fab fragments as sensing molecules with gold nanoparticles was presented. An interesting study was reported by Musile and collaborators, wherein microfluidic paper devices were developed for the presumptive multiplexed determination of a variety of illicit, seized drugs.
The observable colour changes were qualitatively detectable with the naked eye with a few micrograms of each compound present cocaine, ketamine, opiates and various phenethylamines. Semi-quantitative analysis was also possible using a smartphone as the detector. The proposed method seems promising for on-site analysis during police actions due its simplicity; it does not require highly qualified operators or expensive instrumentation. Walczak and co-authors described a miniaturized paper-based strip image-based fluorescence detection system with a hand-held optical device, and demonstrated its viability as a highly sensitive tool for point-of-care analysis of drugs of abuse in human sweat, with a focus on cocaine detection.
Another work focused on the detection of cocaine using a portable paper-based device was reported by He and co-works. Upon the recognition of cocaine by two pieces of rationally designed aptamer fragments, the luminescence of the UCNPs immobilized on the paper is quenched by Au nanoparticles AuNPs , which indicates the cocaine concentration.
This device can also be used to track the drug content in blood samples.
Currently, several commercial kits are available for qualitative and semi-quantitative detection of drugs of abuse, predominantly colourimetric tests, for several types of biological matrices, mainly urine samples. These portable drug testing kits are portrayed as simple, quick and low priced, but it is also recognized that a lack of training or adequate quality assurance can result in potentially serious problems. After all, quality-control and quality-assurance procedures are routine in clinical laboratories but may be less familiar to those performing hand-held analyses directly at crime scenes.
Internal controls need be used to indicate insufficient samples, improper results or misinterpretations. Carrio and collaborators presented a smartphone-based automated reader for drugs of abuse amphetamines, ketamine and cocaine using lateral flow assay tests, consisting of an inexpensive light box and a smartphone device. Colourimetric test images captured with the smartphone camera were processed in the device using chemometrics computer vision and machine learning techniques to perform automatic extraction of the results, diminishing the subjectivity of the interpretation of the data as occurs in the case of simple visual inspection.
Electrochemical sensors exhibit good sensitivity and selectivity, especially when associated with bio chemical modifications of the electrode surface. Shaw and Dennany recently published a brief overview of some of the recent publications related to the application of electrochemical sensors to forensic drug analysis of several relevant samples. Several studies have reported the development of electrochemical sensors for on-site forensic applications, in this scenario, we can highlight the use of screen-printed electrodes or systems adapted for simple operation directly in field.
Freitas and collaborators reported the use of a robust batch-injection analysis system coupled with the use of a boron-doped diamond electrode for cocaine detection in seized samples with a detection limit of 0. The authors used a multivariate calibration for cocaine determination in the presence of three different commonly found interferers codeine, paracetamol or caffeine.
Several different contributions of electrochemical methods for drug analysis can be found on recent reviews about this topic. Electrophoresis devices are also good candidates for on-site analysis. Regarding this, a screening method for amphetamine-type drugs in street-grade illegal tablets and urine samples using portable capillary electrophoresis with contactless conductivity detection was also reported.
Penido and co-authors described in a recent review the use of Raman spectroscopy in forensic analysis for the identification of cocaine and other drugs of abuse. The authors discussed the recent developments in Raman spectrometers portable instruments and new excitation wavelengths offering alternatives for the identification and quantification of drugs of abuse, including investigations conducted immediately at the scene of a crime using this technique.
The chemical profiling is mainly conducted in the forensic laboratories of national police criminalistics programs to establish drug chemical characterization studies and provide useful data for law enforcement authorities involved with illicit drugs issues. Hence, a simple and fast method suitable for on-site screening analysis with great sensitivity and selectivity is highly desirable. In this scenario, electrochemical techniques were explored to detect and quantify several adulterants in seized drugs, especially cocaine samples.
This platform combined the use of screen-printed electrodes and a conductive and flexible gelatine hydrogel as the electrolyte, in a glove, see Fig.
The wearable fingertip sensor for on-the-spot identification of cocaine and its cutting agents offers considerable hope for detection at points of interest such as airports and harbours, by simply swiping the electrode system over the suspicious powder, joining both fingers and starting the square-wave voltammetric measurement.
Freitas and co-authors developed a compact and robust portable batch-injection analysis system with electrochemical detection for seized cocaine analysis allowing screening of its major adulterants benzocaine, caffeine, lidocaine, phenacetin, paracetamol and procaine. At the same time, there are several commercial kits for the detection of illicit drugs, in this manner, various colourimetric tests aim to identify the purity of drugs, as well as the qualitative detection of their main adulterants.
These devices provide presumptive assays, but still usually exhibit a lack of selectivity, thereby further studies are welcome to improve their performance. Silva and collaborators outlined recently an elegant approach to improve the selectivity of portable paper-based colourimetric assays through electrochemical pre-treatment of cocaine samples to determine procaine adulteration, see Fig. This kind of device can be explored as an alternative to solving the interference problems of traditional colourimetric tests, allowing selective multiplex analyses.
The unprecedented emergence in recent years of potentially dangerous NPS, that are not under international control, has led to the increased abuse of them, hospital emergency admissions and fatalities. The literature presents an increasing number of studies on the detection of different types of NPS, most of them using chromatographic methods, mass spectrometry and spectroscopy techniques, among others, as reported in recent reviews. There are several categories of new psychoactive substances, such as synthetic cannabinoids, cathinone analogues, piperazines, phenethylamines, tryptamines, etc.
Dronova and co-authors presented the electrochemical detection of synthetic cannabinoids SCs through electro-oxidative transformation of 11 new indole and indazole SCs which are illicit smoking mixtures on the drug market. The authors found voltammetric responses of SCs that can be used for their detection in smoking mixtures and artificial saliva with limits of detection in the nanomolar range.
This approach could make GSR detection at crime scenes extremely easy and cheap. Carrio and collaborators presented a smartphone-based automated reader for drugs of abuse amphetamines, ketamine and cocaine using lateral flow assay tests, consisting of an inexpensive light box and a smartphone device. Most of the assays developed for the portable monitoring of agrochemicals are based on enzymes, which may increase the final cost of such sensors or bioassays. As previously stated in this review, the replacement of enzymatic reactions by selective chemical reactions, e. This review discusses works published between and regarding portable or potentially portable devices such as electrochemical sensors , field tests and intelligent devices that can be used in different areas of forensic chemistry and covers the following subjects: Amperometric detection was the selected technique in the greater part of the sensors described, while differential-pulse voltammetry was also used and demonstrated higher sensitivity. Table 2 shows that many articles have been published regarding the detection of adulteration in beverages by a large range of techniques.
The proposed protocol has been successfully validated by the HPLC method and applied to seized street samples assays, which demonstrates the viability of this simple method. A colourimetric approach to detect cathinones was demonstrated by Philp and co-workers, who developed a presumptive colour spot test for synthetic cathinone detection in seized illicit materials.
This uncomplicated method provided positive results for 39 out of 44 cathinone substances tested. Cuypers and collaborators proposed a guideline for the use of classic commercial presumptive colour tests with the purpose of identifying different classes of NPS synthetic cathinones, synthetic cannabinoids, piperazines and phenethylamines.
The use of disposable cost effective screen-printed graphite macroelectrodes was described by Cumba and co-authors as a potential electrochemical approach for in-field screening of a NPS called synthacaine. Andrade and co-workers recently described the use of voltammetric measurements for the fast screening of phenethylamines derivatives NBOMe.
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This method relies on the electrochemical oxidation of these molecules in order to produce an analytical signal that can be related to the NBOMe concentration with an average lower limit of quantitation of 0. The proposed method achieved detection limits lower than 0. The authors of the present review believe that the increasing introduction of NPS into the drug market and the higher demand for affordable forensic and toxicological methodologies will drive a wider range of efforts to develop portable and user-friendly methods in this area, aiming for crime scene screening and other police activities.
Beverage analysis through electronic tongues has become one of the major applications of such devices. The first electronic tongue, at the time named taste sensor, 17 was initially developed as a sensor that could mimic the ability of the human tongue in differentiating between the five distinct tastes sweet, salty, sour, bitter and umami. Later, the term taste sensor was changed to electronic tongue as a more broad term and refers to a device with sensors of low selectivity that can analyse and differentiate between liquid samples according to their individual characteristics.
Several reviews regarding beverages analysis can be found in the literature. A short number of them are shown in this article, but there are many more papers available.
Focusing on the specific techniques, there are reports about the use of near-infrared spectroscopy, — NMR, Raman spectroscopy, electrophoretic methods, electronic nose, — electronic tongue, ,— combined e-tongue and e-nose, biosensors, colourimetric techniques and miscellaneous techniques. At last, there are reports on specific molecules found in beverages, e. Table 2 shows that many articles have been published regarding the detection of adulteration in beverages by a large range of techniques.
This discrepancy shows a great need to focus on the development of portable devices for other types of beverages.
For instance, a current worldwide problem is the adulteration of alcoholic beverages by diluting it or mixing with forbidden components, such as methanol. This practice harms the consumer financially and leads to health problems. Although there are in the market some electronic tongues to detect whiskey adulteration, they are still expansive and unheralded.
Chang developed two fluorescence sensors for determining two illicit date rape drugs, i. Furthermore, Leesakul et al. Electrochemical studies were performed by two groups led by Banks and Hart. In Banks's group, they evaluated the electrochemical response of flunitrazepam with a screen-printed graphite electrode, while Hart's group performed a study using a disposable screen-printed sensor to detect diazepam.
In addition, GHB can also be found naturally in alcoholic and non-alcoholic drinks, although at non-dangerous levels for a human. Nevertheless, studies are being performed to detect GHB in a lower concentration to differentiate between the criminal amount of GHB and the regular amount present in a beverage. The analysis of drug-facilitated crimes in beverages using portable devices is still an incipient topic, and work has been done in the areas of fluorescence and electrochemical sensors, ELISA and Raman.
However, besides the good results obtained by the works here described, there is no device yet that could be used by the final consumer to detect the presence of such molecules in their drinks. The virulence biomarkers of both Yersinia pestis , which causes the plague, and Bacillus anthracis , the etiological agent of anthrax infection, were chosen by Cohen et al.
They used an europium III tris-bipyridine cryptate as the fluorescent donor and successfully detected the analytes in apple juice, orange juice, cola, fresh milk, mineral water and tap water. Cyanotoxins are very powerful natural biotoxins that are produced by cyanobacterias and if ingested can cause damages to the liver, nervous and respiratory systems and can lead to death. When an exponential growth of cyanobacterias happens, the amount of those cyanotoxins also increases becoming extremely dangerous for animals and humans.
These molluscs such as mussels, clams, oysters and scallops can filter the water, and when doing so, the cyanotoxins can accumulate in the shellfishes. A complete review of the analytical tools and biological assays used for the paralytic shellfish poisoning toxins PSTs analysis was published by Humpage et al. Another extremely dangerous toxic substance that has been used for bioterrorism is the protein abrin found in the seeds of Abrus precatorius. A Chinese group developed an up-converting phosphor technology-based lateral flow assay abrin-UPT-LFA with high-affinity monoclonal antibodies mAbs for abrin protein.
With the LFA, they were able to detect abrin in spiked samples of water, soft drink, juice and beer, along with some solid and powder food samples. Experiments were performed in several samples, including apple juice and milk, and high specificity with little cross-reactivity was observed among the selected toxin antibodies. The articles presented in this section show that most of the studies have been developed using enzymes as an important part of the detection mechanism. However, enzymes usually are expensive, difficult to obtain especially in developing countries and are complicated to work with.
In this sense, the authors believe that methodologies that are not based on enzymes reactions are a good alternative for analysing bioterrorism agents.