Table 4 Summary of recent studies in rapid test paper technology
No. | Techniques | Mechanisms | Samples | Type of pesticides | References |
|---|---|---|---|---|---|
1 | Pesticide enzymatic and immunoassay test kits | The kits are qualitative colorimetric acetylcholinesterase (AChE) inhibition-based tests. Acetylcholinesterase hydrolyses acetylcholine (ATC) when an inhibitor, such as an organophosphate or carbamate, is absent. After that it interacts with 5,5′-dithiobis-(2-nitrobenzoic acid), resulting in a yellow colour which can be visualized with the naked eye or with a colorimeter at 405 nm wavelength. If OP or CM molecules are found in the sample, it will inhibit AChE, preventing or decreasing colour creation, depending on the quantity. | Water, vegetables, fruits, other ecological samples | Organophosphate (OP) and carbamate (CM) pesticides | Kumar et al. [96] |
2 | ELISA kits were used in the Mississippi River (immunoassays) | The first commercial immunoassay kit for pesticide analysis was made available in 1988. This kit was utilized to detect atrazine [10]. Immunoassays have been established for various analytes found in water, soil, and sediments. They are well suited for large-scale detection of metals, pesticides, and organic chemicals such as polychlorinated biphenyls, polyaromatic hydrocarbons, bacterial toxins, and TNT. | Water, soil, vegetables | Herbicides, pesticides such as Atrazine, and organic chemicals such as polychlorinated biphenyls, polyaromatic hydrocarbons, bacterial toxins, TNT | |
3 | Nanoparticle-based electrochemical, optical, and magnetic environmental sensors | Wang et al. [185] detected microcystin-LR in water from a Chinese lake with the use of antigen-coated filter paper and single-walled carbon nanotubes (SWNTs). The SWNT paper card serves as the electrode surface, the platinum wire serves as the counter electrode, and Hg2Cl2 serves as the reference electrode. As analytes spread through the SWNT layers, an interaction occurs between the antibodies in the paper and the analyte, forming an Ag-Ab complex that drives apart from the SWNT layers, reducing the current travelling through them. Thus, current decreases as the concentration of the analyte increases. This approach is simple, mobile, and highly sensitive, specialized, and inexpensive. This technique is equivalent to enzyme-linked immunosorbent assay (ELISA), but it is approximately 28 times quicker. | Apple fruit samples, water, air, dirt | Pesticides including phenoxy organophosphates, carbamates, pyrethroids, atrazine, neonicotinoids, organochlorines | Willner and Vikesland, [187], Motaharian et al. [129], Wang et al. [186], Wang et al. [185], Zhang et al. [193] |
4 | Biosensors | Biosensors for pesticides depend on enzyme inhibition, such as how carbamate and organophosphorus pesticides inhibit cholinesterase (ChE) by blocking the enzyme’s binding site. Pesticide toxicity is assessed by detecting the reduction in enzymatic activity following exposure to the sample. Calculating the percentage of inhibition of enzyme activity induced by pesticide exposure can be used to measure the concentration of the pesticide. The activity of the enzyme can be evaluated to identify substrata or enzyme reaction products by using amperometry, potentiometry, spectrometry, fluorimetry, or thermometry. Herbicides disrupt photosynthesis or phosphorylation, which is the basis for whole-cell biosensors and can be observed using an oxygen electrode, an amperometric sensor, or an optical sensor. Whole-cell sensors based on organophosphorus hydrolase were created using microalgae and bacteria (OPH). | Bananas, fruits, vegetables, food | Organophosphorus insecticides, for example, parathion, paraoxon, methyl-parathion | Mathivanan, [119], Zamora-Sequeira et al. [190], Liu et al. [110] |
5 | Fluoroimmunoassay (TRFIA) with a fluorescent europium chelate label | This approach was selective and sensitive, and they were able to achieve a detection limit for 17-estradiol of 2.3 pg/ml, which is similar to that achieved by ELISA. With the TRFIA, The detection limit for estriol was 4.3 pg/ml, which is 1–2 levels higher than ELISA. This technique with TRFIA was utilized to quantify 17-estradiol at 32 pg/ml and estriol at 5.5 pg/ml in water. Bacigalupo [15] employed a fast TRFIA screening technique in which liposomes trap a terbium/citrate complex to detect atrazine in water [15]. This method achieved a detection limit of 0.1 ng/ml, allowing multiple samples to be examined simultaneously. After a brief incubation period, atrazine covalently coupled to mastoparan, a polypeptide, facilitated the release of terbium citrate. Mastoparan is simple to make since it is made up of various amino acids. Mastoparan’s lysine amino acids allow it to bind to a wide range of target analytes. | Major arable crops, grassland, fodder crops. horticultural crops include fruit, vegetables, protected crops, hops, mushrooms, bulbs, flowers and hardy nursery stock, Chinese cabbage, honey | Imidacloprid residue chlorpyrifos | Thomas and Hutton [171], Chen et al. [38], Majima et al. [114], Si et al. [165] |
6 | Mass spectrometry (MS) | Researchers also designed a system using an ion trap mass-spectrometer whereby polydimethylsiloxane (PDMS) membranes were utilized to add analyte into the mass spectrometry system through membrane diffusion. After coarse filtering of the wastewater, the mass spectrometry system was installed into the treatment tank. At 12-minute intervals, the sampling apparatus injected 1 ml water samples into constant running water filtered by charcoal which was in contact with the membrane interface. The device measured chloroform, a product of clean water chlorination. | Fruits, vegetables | Carbaryl pesticides, imidacloprid, deltamethrin, cypermethrin, malathion, acetamiprid, monocrotophos, chlorpyrifos-methyl, diazinon | |
7 | Azo-coupling reaction-based method | 1-naphthol is produced when organic base pre-treated carbaryl insecticides react with a diazonium salt, resulting in a colour change from yellow to orange. | Fruits, vegetables | Carbaryl pesticides | |
8 | Microfluidic arrays sensor | A method based on paraoxon as a typical Organophosphate. Different concentrations of paraoxon pre-inhibited AChE for 30 minutes before adding it to the detection system to be incubated. Colour change from red to blue. | Fruits, vegetables | Organophosphate pesticides | |
9 | Gold nanoparticle-based colorimetric aptasensor | A method based on AuNP colorimetric assay for rapid detection of organophosphorus pesticides. A method based on AuNP colorimetric assay. The AuNP solution turned blue. | Food, water | Organophosphorus, carbamate pesticides | |
10 | Acetylcholine and acetylcholinesterase inhibitors detection using gold nanoparticles coupled with dynamic light scattering | To identify organophosphorus pesticides quickly. The acetylcholinesterase hydrolysis reaction and the dissolution of AuNPs in Au3+ - CTAB solution. The colour changes from red to colourless or red to bright pink. | Food, water | Organophosphorus pesticides | |
11 | A method based on citrate-capped AuNPs | Citrate-capped AuNPs. The Colour change from wine-red to purple-blue. | Food, water samples | Dithiocarbamate pesticides | |
12 | Immunoassay test card | The card is based on using alkaline phosphate (AP) to react with 5-BCIP/NBT to p-toluidine salt, 5-BCIP-4-chloro-3-Andolyphosphate nitro-blue tetrazolium chloride. In the sampled solution, there is competition between free atrazine and carbaryl for the antibodies of the card. The amount of free atrazine and carbaryl is indicated by the blue colour intensity. Atrazine band and carbaryl band do not conflict with each other. However, interference is observed when propazine is present at the same concentration or when ametryn, propazine, prometryn, simazine, and terbuthylazine are present in concentrations more than 10 ng/ml. However, this test card provides consistent measurement findings for GC-MS and HPLC-FD with concentrations 10 and 200 ng/ml visual atrazine and carbaryl in various fruits and vegetables. | Fruits, vegetables | Carbaryl, atrazine pesticides | |
13 | Bioactive paper-based sensors | Acetylcholinesterase is a type of enzyme that breaks down acetylcho (AChE). The test card is made of paper and is based on Ellman's colorimetric test (1 to 10 cm), in which a biopolymer chitosan gel immobilized by glutaraldehyde with AChE and 5,5'-dithiobis (2-nitrobenzoic) acid (DTNB) is cross-linked and acetylthiocholine iodide is utilized as an external reagent (ATChI). The test protocol includes introducing a pesticide-containing solution in the sensing zone. The paper is put in ATChI solution for the induction of enzymes catalysed hydrolyses after an incubation time. The card is placed in the ATChI solution after incubation to trigger enzyme-catalysed hydrolysis of the substratum, which causes the change of yellow colour. A lack of yellow colour or a decrease in yellow colour indicates AChE inhibitor levels. The Biosensor has a high sensitivity to organophosphate and carbamate pesticides (methomyl = 6.16 10(-4) mM and profenophos = 0.27 mM) and may respond quickly (5 minutes). The results pointed to a paper-based biosensor that is quick, sensitive, cost-effective, portable, disposable, and simple to use. | Fruits, vegetables | Organophosphate, carbamate pesticides | Badawy and El-Aswad [16] |
14 | A novel biosensor test card | Fernández-Ramos et al. [56] created a new organophosphate and carbamate pesticide biosensor. The test card is made of support paper (1 ~17.6 mm), which contains a small hole in place between the acetylcholine chloride (AChCl) and acetylcholine esterase (AChE), which ensures that they touch the reaction zone only when transported to the BCP (Bromocresol Violet-containing Reaction Zone) through a sample solution lateral flow. The sensor works at ambient temperature, and the inhibited reaction rate is used as an analytical message, determined by the suitable colour coordination with the camera. For carbaryl and chlorpyrifos, calibration courts of 0.24 to 20 g L-1 and 2.00 to 45 g L-1 were obtained, respectively. The limits for detection were 0.24 and 2.00 μg L-1, and replicability was between 4.2 and 5.5 per cent correspondingly. The procedure was used to determine pesticides without sample pre-treatment in diverse water samples. | Fruits, vegetables | Organophosphate, carbamate pesticides | |
15 | Multi-detection techniques based on enzyme inhibitions | Organophosphate and carbamate pesticides, according to Jia et al. [90], can inhibit cholinesterases, acetylcholinesterase (AChE), and butyrylcholinesterase. This technique allows multi-residue inhibition detection based on enzymes to be employed in the monitoring of multi-analytes. The level of inhibition is associated with pesticide content, which can be quantitatively detected. The nucleophile serine hydroxyl group present in the active site of AChE can form covalent bonds with the phosphorus atoms of the organophosphates. AChE is the most frequently utilized enzyme for the creation of multi-detection techniques based on enzyme inhibitions. In the presence of OP or CM insecticides, AChE may hydrolyze some colour-based substrates, whereas colour development can be reduced. Consequently, different colorimetric screening methods based on this idea have been developed. An optimized and validated AChE assay was utilized for carbofuran, carbofuran-3-hydroxy, and dichlorvos extracts. AChE test was performed. Indoxyl acetate was employed to build a substratum that can be degraded quickly by AChE. | Fruits, vegetables | Organophosphate, carbamate pesticides | |
16 | Paper partition chromatography | Using paper partition chromatography could remove many of the issues connected to the use of stationary phases in reverse-phase chromatography. Chemically altered papers could be used in many areas of pesticide detection, e.g. ion exchange papers that separate polar pesticides such as some herbicides, fungicides, and organophosphates. In some cases, fibreglass and acetylated papers have been used, and the results rationalize a further examination of their applicability in the chromatography of pesticides. Low temperatures limit the use of paper chromatographic separation for pesticides. Decreased temperatures reduce the chromatogram development rate and vastly improve the resolution by reducing the size of dots on the chromatogram. Low temperatures may allow volatile solvents to be used for both stationary phases and as developing solvents. | Fruits, vegetables | Water-soluble organophosphate pesticides, herbicides, fungicides | |
17 | Colorimetric technique | After pre-treating carbaryl with an organic base, 1-naphthol will be produced and quickly undergoes an azo-coupling reaction with Formylbenzene diazonium hexafluorophosphate (FBDP). Decomposing less reactive carbaryl into 1-naphthol and N-methyl carbamates into phenols can be done quickly in 1 minute. Both quantitative and qualitative analyses of carbaryl could be done based on colour differences with the FBDP solution. This colorimetric method can detect 50 μM of carbaryl from a sample of fruit without further processing. Cao et al. [32] covered the techniques and applications of many enzyme inhibition-based methods in their review. These included rapid detection of organophosphates and carbamates using electrochemical biosensors, optical colorimetric assays, assays based on fluorescence, test cards, and a microfluidic device. | Fruits, vegetables | Carbamate pesticides, carbaryl residue | |
18 | Microarray method | Antibodies and antigens of sixteen pesticide pairs were tested for cross-reactivity and reactivity. A microarray chip with 7 antigens immobilized on a nitrocellulose membrane was made. To acquire a sensitive colorimetric immunoassay, gold nanoparticles were utilized for labelling and signal amplification. Primary and secondary antibodies such as gold compounds were used as tracers to compare the detection formats (directly and indirectly). Based on the indirect approach, a seven-plex immunochip test was designed and optimized. In the case of pesticides, the detection limit was 0.02–6.45 ng mL-1. The visual assessment showed detection limits to be between 1 and 100 ng mL-1. The immunoassay chip has the potential for pesticide multi-analysis in fruits and vegetables, according to this study. The proposed microarray method is versatile and applicable to multiplex immunoassays for small molecular complexes. | Fruit | Phenoxybenzoic acid, atrazine mercapturate | |
19 | Nano-biosensors | Nano-biosensors have advantages like selectivity, sensitivity, rapid detection, and response. Nanosensors react and convert a target into a signal for rapid recognition with the help of biological parts. As per the previously mentioned methods, it is clear that the described techniques play an important role in pesticide determination. Pesticides have been detected using a variety of bio-elements, although enzyme-based biosensors are the most extensively used in comparison with other bio-elements for contaminant detection. This is due to the complex structure, which has a high selectivity for pesticide compounds and helps in recognizing them in multicomponent mediums. Nanobiosensors have shown exceptional results in pesticide detection. The progressions in nano-biosensors show encouraging and consistent data with no undesirable impacts while also offering new developments in pesticide identification. | Food, fruits, vegetables | Organophosphorus (OP), carbamates (C) | |
20 | Drop-wipe-test | In the research article by Wang et al. [184], they clarified that to achieve quick detection of pesticides in fruit, a “drop-wipe-test” method is established which is based on wiper-type filter paper coupled with SERS. Silver nanoparticles were used to coat the paper which was used as a wiper-type SERS substrate. The “drop” and “wipe” steps were combined to make the sampling and extraction operations easier. The last step, “test”, was done to acquire the data using a Raman spectrometer. The ideal wipe time was approximately 15 seconds which ensured a complete extraction of the analyte. SERS substratum was used to rapidly detect thiram in three different fruits by this technique. Pesticide concentrations increased, resulting in a linear association between average SERS spectra intensity and R-square values of 0.9991 for apple, 0.9872 for pear, and 0.9841 for grape. The limit of detection for thiram was 4.6261 in apple, 5.1799 in pear, and 5.7061 ng/cm2, in the grape peel. The detection limits are lower than the upper limits set for pesticides in food by China’s National Food Safety Standard. Thus, the SERS technique together with an absorbent SERS substrate is rapid, practical, reliable, and sensitive to detect pesticides. | Fruit | Organophosphate pesticide |