A novel chemiluminescence assay of organophosphorous pesticide quinalphos residue in vegetable with luminol detection

Designed fluorescence "on-off-on" probe based on cobalt, zinc, and nitrogen co-doped graphene quantum dots: A case of quinalphos sensing

In this study, we developed a new fluorescence "on-off-on" sensor utilizing water-soluble cobalt/zinc-nitrogen co-doped graphene quantum dots (Co/Zn-N-GQDs) to recognize quinalphos pesticide in vegetable and fruit samples. Primarily, the synthesis method employed a one-pot hydrothermal approach, using betel leaves as a natural precursor and cobalt ("Co"), zinc ("Zn"), and urea ("N") as dopant sources. The Co/Zn-N-GQDs probes underwent comprehensive analytical characterization. The Co/Zn-N-GQDs were synthesized with a remarkable luminescence yield of 31.49%, exhibiting excitation at 320 nm and emission peak at 393 nm. Interestingly, the luminescence of Co/Zn-N-GQDs was selectively "Turned Off" by Cu2+ via a static quenching setup. Remarkably, quenched fluorescence was surprisingly reactivated upon adding quinalphos to the quench setup, indicating a direct correlation between luminescence reactivation and quinalphos concentration. Briefly, this phenomenon is ascribed to the functional groups in quinalphos, such as quinoxalinyl and phosphorothioate, which chelate with Cu2+ ions, disrupting the nonfluorescent Cu2+-Co/Zn-N-GQDs complex. The design sensor demonstrated a limit of detection (LOD) of 0.11 μM and a broad linear span of 0.5 to 200 μM. In conclusion, Cu2+-Co/Zn-N-GQDs sensor showed immediate applicability, stability, and reproducibility, making it highly effective for quinalphos sensing in various samples.

Development of a rapid aptamer-chemiluminescence sensor for detecting glyphosate pesticide residue in soybeans

Glyphosate (GLY) is a widely used herbicide worldwide, particularly in cultivating genetically modified soybeans resistant to GLY. However, routine multi-residue analysis does not include GLY due to the complexity of soybean matrix components that can interfere with the analysis. This study presented the development of an aptamer-based chemiluminescence (Apt-CL) sensor for rapidly screening GLY pesticide residue in soybeans. The GLY-binding aptamer (GBA) was developed to bind to GLY specifically, and the remaining unbound aptamers were adsorbed onto gold nanoparticles (AuNPs). The signal was in the form of luminol-H2O2 emission, catalyzed by the aggregation of AuNPs in a chemiluminescent reaction arising from the GLY-GBA complex. The outcomes demonstrated a robust linear relationship between the CL intensity of GLY-GBA and the GLY concentration. In the specificity test of the GBA, only GLY and Profenofos were distinguished among the fifteen tested pesticides. Furthermore, the Apt-CL sensor was conducted to determine GLY residue in organic soybeans immersed in GLY as a real sample, and an optimal linear concentration range for detection after extraction was found to be between 0.001 and 10 mg/L. The Apt-CL sensor exploits the feasibility of real-time pesticide screening in food safety.

A sensing platform based on zinc-porphyrin derinative in hexadecyl trimethyl ammonium bromide (CTAB) microemulsion for highly sensitive detection of theophylline

A new porphyrin-based sensing platform in hexadecyl trimethyl ammonium bromide (CTAB) microemulsion is developed for highly sensitive detection of theophylline. In this sensing system, the zinc-porphyrin-cinnamic acid conjugate (Zn-TPPCA) works as fluorescence probe while theophylline can decrease fluorescence intensity of the probe. Further studies indicate the linear relationship between the fluorescence quenching value and the concentration of theophylline within a given range. And the introduction of CTAB microemulsion can greatly enhance sensibility and stability of this detecting system and facilitate the detection of theophylline. On the basis above, a highly sensitive sensing platform for theophylline is created with a low limit of detection (LOD) of 0.0083 μg mL^-1 under the optimal detection conditions. And further application of this method in determination of commercially available theophylline preparation shows excellent results. Subsequent studies on quenching mechanism indicate that static quenching appears between Zn-TPPCA and theophylline. Therefore, this work provides not only a highly sensitive method for determination of theophylline but also further evidence for creation of biosensors for drugs with porphyrin derivatives.

The effectiveness of vitamin C on quinalphos ileal toxicity: a study of histological, ultrastructural, and oxidative stress markers

There is a significant hazard of human exposure to the organophosphates which is a constant threat, and they are responsible for numerous cases of poisoning and mammalian toxicity annually in non-target wildlife. The antioxidants, including the vitamin C (Vit C), have a protective effect on some organophosphorus compounds-induced organ damage. Quinalphos (QP) is one of these compounds. The investigation's objective is to see if there was any effect of QP on the rat ileum which could be rectified by using Vit C. Three groups of 24 animals were created. As a control, the first group was given pure water. Second group subjected to oral gavages of QPs. Third group rats were given oral gavages of Vit C plus QPs for 10 days. The reaction of ileal enterocytes to food-borne QPs was marked by poorly organized microvilli, numerous vacuoles within them, disrupted nuclei with chromatin margination, disoriented mitochondria, and an expanded intercellular space. The absorptive columnar cell illustrated many vacuoles inside with herniation of microvilli, and normal goblet cells were also seen. Many Paneth cells towards the lumen of intestinal gland contained secretory granules of different sizes and shapes. The histological architecture of the ileal mucosa in the QP plus Vit C group was found to be close to those of healthy controls. The outcomes of this study suggest that administering Vit C in rats treated with QPs protects them from ill dysfunction caused by QP.

Facile synthesis of carbon dots from Tagetes erecta as a precursor for determination of chlorpyrifos via fluorescence turn-off and quinalphos via fluorescence turn-on mechanisms

Convenient one-pot synthetic route for the fabrication of carbon dots (CDs) from Tagetes erecta flower (TEF), named as "TEF-CDs', through solvo(hydro)-thermal carbonization of the TEF was developed. The TEF-CDs revealed high selectivity towards chlorpyrifos and quinalphos, acting as a fluorescent probe. The CDs synthesized from T. erecta flower showed a strong blue color at 495 nm when excited at 420 nm, along with the exhibition of a strong quantum yield of 63.7%. The synthesized CDs revealed their richness in the surface-active organic group that synthesized CDs from T. erecta flower are mainly comprised of C, O, and N, which were crystalline in structure that was revealed by TEM image and XRD spectra. Furthermore, when the probe was exposed to different pH conditions, no major noticeable changes were recorded. Moreover, when the probe was exposed to chlorpyrifos and quinalphos, we have noticed that fluorescence spectra was turned off when the probe was exposed to chlorpyrifos and "turned on" after the exposure quinalphos. Moreover, fluorescence spectral changes showed a good linearity with chlorpyrifos and quinalphos concentrations in the range of 0.05-100.0 μM for chlorpyrifos and 0.01-50.0 μM for quinalphos. The limit of detection are 2.1 ng mL^-1 and 1.7 ng mL^-1 for chlorpyrifos and quinalphos, respectively. Finally, the TEF-CDs-based fluorescent nanoprobe was successfully applied to estimate chlorpyrifos and quinalphos with an effective accuracy in rice and fruit samples with rapid detection time.

Organophosphorus pesticide quinalphos (Ekalux 25 E.C.) reduces sperm functional competence and decreases the fertilisation potential in Swiss albino mice

Quinalphos (QP) is one of the most commonly used organophosphate pesticide for agriculture. In this study, adult Swiss albino male mice were orally administered with 0.25, 0.5 and 1.0 mg/kg of QP (Ekalux 25 E.C.) for ten consecutive days and the reproductive function was assessed at 35 and 70 days after QP treatment. At highest dose (1.0 mg/kg), QP exposure resulted in significant decrease in motility and increase in sperm head defects and DNA damage. Pharmacokinetic data showed a threefold increase in concentration of QP in the testis as compared to serum. QP was detectable in testes even after 24 hr of administration indicating slow clearance from tissue. In addition, high oestradiol, low testosterone level with a parallel increase in aromatase and cytochrome P450 transcript levels was observed. Significant decrease in fertilisation, lower blastocyst rate and poor blastocyst quality was observed when spermatozoa collected from QP exposed mice were subjected to in vitro fertilisation. In conclusion, exposure of QP to male mice decreases the sperm functional competence and fertilising ability, which appears to be mediated through elevated oxidative stress and altered steroidogenesis in testes.

Determination of quinalphos in human whole blood samples by high-performance thin-layer chromatography for forensic applications

A simple and rapid procedure for the determination of quinalphos in human whole blood using liquid-liquid extraction and high-performance thin-layer chromatography was developed and validated. Seven different organic solvents were tested for optimum extraction of quinalphos from spiked blood samples. The effect of pH on the extraction yield of quinalphos was also examined. An average recovery of 93.61% was achieved from diethyl ether solvent at pH 3. Chromatographic separation was performed on silica gel 60F₂₅₄ plates using mobile phase n-hexane-acetone in the ration 9:1 (v/v). Densitometric detection was carried out at 325 nm in absorbance mode. The interference of other organophosphorus pesticides of forensic relevance was not observed. The linear regression analysis in spiked whole blood samples resulted in linear calibration plot in the range 1 to 100 μg mL^-1 with r² = 0.9981. Sensitivity was represented by LLOQ at 1 μg mL^-1. The within-day precision and between-day precision ranged from 0.18 to 1.04%, and 0.14 to 0.79% with an overall average recovery of 91.06% at three concentrations 1, 10, and 50 μg mL^-1. No significant decrease in the concentration of quinalphos was observed for samples under different storage conditions. Finally, the developed procedure was applied to postmortem blood samples obtained in three fatal cases of poisoning by quinalphos.

A proposed image-based detection of methamidophos pesticide using peroxyoxalate chemiluminescence system

Pesticides pose a serious public health risk due to their toxicity, such as in the case of the widely distributed organophosphorus pesticide methamidophos. There is a strong need to develop a simple, rapid, and cost-effective method of detecting methamidophos residues; thus, this study proposes the TCPO-Rubrene-H2O2 chemiluminescence (CL) system as a means of pesticide detection via quenching effect. The results show that the methamidophos concentration is inversely proportional to the CL system's light output as confirmed through fluorescence spectroscopy and Batch Measure Macro (BMM) analysis. The light intensity differences were correlated with the methamidophos concentration with both methods showing linear trends. Both the digital camera and the smartphone camera BMM analyses displayed good sensitivity, with respective detection limits of 1.6 μg/mL and 1.0 μg/mL and respective quantitation limits of 5.0 μg/mL and 3.0 μg/mL. Both also showed good linearity within the 100-10000 μg/mL range, suggesting viability as alternatives to the fluorescence spectrometer; however, the light intensity difference values per pesticide concentration of both camera systems were significantly different from one another owing to differences in camera features.

Insulin: a review of analytical methods

Insulin is an important polypeptide hormone that regulates carbohydrate metabolism.

Acetylcholinesterase biosensor based on a gold nanoparticle-polypyrrole-reduced graphene oxide nanocomposite modified electrode for the amperometric detection of organophosphorus pesticides

A nanohybrid of gold nanoparticles, polypyrrole, and reduced graphene oxide sheets (named as Au-PPy-rGO) was achieved by electrochemical deposition of reduced graphene oxide with pyrrole and the introduction of gold nanoparticles. Acetylcholinesterase (AChE) was further encapsulated in a silica matrix and immobilized on the Au-PPy-rGO nanocomposite by co-deposition with (NH4)2SiF6. The presence of PPy helped to avoid the aggregation of rGO caused by van der Waals interactions between individual sheets and significantly increased the surface area of the modified electrode. The obtained Au-PPy-rGO nanocomposite not only showed excellent conductivity but also exhibited a high electrocatalytic activity and specific affinity for thiocholine, the hydrolysis product of the enzyme, and thus an improved detection sensitivity. Since AChE molecules were protected by the circumambient silica matrix, which provided a biocompatible environment and facilitated mass transport, the fabricated AChE biosensor displayed high stability and excellent activity together with a fast response to organophosphorus pesticides. Under optimum conditions, the biosensor led to the rapid and sensitive detection of paraoxon-ethyl from 1.0 nM to 5 μM with a detection limit of 0.5 nM.

Trends of pesticide exposure and related cases in the Philippines

The study aims to provide a comprehensive trend of pesticide poisoning cases in the Philippines as well as pesticide exposures, and risk factors related to the adverse effects of pesticide. Records were gathered from the National Poison Control and Management Center (NPCMC), the Philippine General Hospital, De La Salle Medical Center, and other hospitals, and reviewed research studies conducted in the Philippines. Based on hospital surveys, the number of pesticide cases as well as mortality trends have been increasing. Studies from 2006 to 2010 showed that human health especially those of the farmers is at risk due to pesticide exposure. Illnesses and symptoms such as headache, skin abnormalities, fatigue, fever, and weaknesses were the common health complaints experienced by the farmers as reported in the research studies. Moreover, the studies showed risk factors to pesticide exposure, work practices, and pesticide residues in environmental media that could be contributory to pesticide poisoning cases. Government agencies should intensify their surveillance and regulation on both household and agricultural pesticides. The state of pesticide-related illnesses mirrors the poor safety practices among farmers as well as lack of necessary supervision from the government agencies.