Rapid analysis method for paraquat and diquat in the serum using ion-pair high-performance liquid chromatography

Development of LC-MS/MS analytical method for the rapid determination of Diquat in water and beverages

This study aimed to develop simple, fast, and sensitive methods for the determination of diquat (DQ) in various matrices such as water and beverages. For water, direct injection was tested first, however, the sensitivity of the incurred samples were too low and couldn't possibly achieve the targeted limit of quantification. Hence, dilution with "weaker" injection solvents were tested, and the final conditions involved the dilution of water with acetonitrile (0.4 % ammonium hydroxide) which increased the sensitivity by more than ten times. Nevertheless, the beverages samples needed further treatment to achieve acceptable spiked recovery. The final conditions involved extraction using the aforementioned solvent, followed by heating and partitioning. Both of the methods satisfied the validation requirements, with an average recovery ranging from 85.9 to115 % and associated relative standard deviation (RSD %) within the range 3-8. Further applications on real samples were done to test the levels of contamination.

Aptasensor for paraquat detection by gold nanoparticle colorimetric method

This study aimed to develop an aptasensor for paraquat detection by gold nanoparticles. The specific aptamer for paraquat was selected by using the SELEX process via capillary electrophoresis. Sixty-three aptamer candidates were amplified by asymmetric PCR and screened for paraquat binding using gold nanoparticles (AuNPs). Aggregation of AuNPs was specifically induced by desorption of paraquat binding aptamers from the surface of AuNPs as a result of aptamer-target interaction leading to the color change from red to purple. Aptamer 77F with the following sequence: 5'-AGGCTTACACCTGAAAAGCGGCTTAATTTACACTACTGTAT-3' was selected as a highly specific aptamer for paraquat. The detection limit of paraquat was 0.267 µg/mL by colorimetry and 1.573 µg/mL by the quartz crystal microbalance (QCM) technique. This aptamer showed specificity for paraquat by colorimetry. Dimethyl phophite, diethyl phophite and O,O diethyl thiophosphate potassium salt did not react by colorimetry but, exhibited a weak nonspecific reaction by QCM. This is first time that an aptasensor was used for detection of paraquat based on QCM. However, the aptasensor based on the colorimetric method simply uses a generation of a signal that can be detected by the naked eye. This technique is rapid, low cost easy to use and suitable for on-site detection of herbicide residue.

Separation and Determination of Paraquat and Diquat in Human Plasma and Urine by Magnetic Dispersive Solid Phase Extraction Coupled with High-Performance Liquid Chromatography

A magnetic dispersive solid phase extraction method coupled with high-performance liquid chromatography was proposed for the simultaneous separation and determination of paraquat (PQ) and diquat (DQ) in human plasma and urine samples. Based on the reduction of PQ and DQ to a blue radical and yellow-green radical by sodium dithionite in an alkaline medium, a fast colorimetric method was also developed for the fast detection of PQ or DQ. In this paper, CoFe₂O₄@SiO₂ magnetic nanoparticles were used as the adsorbent for the magnetic dispersive solid phase extraction of paraquat and diquat, and these two analytes were found to be eluted directly from the adsorbent by NaOH solution. The main factors affecting the extraction efficiency including amount of extractant, extraction time, sample volume, sample solution pH, and elution volume were optimized. Under the optimized experimental conditions, the calibration curve was linear at a concentration range of 28.5-570.2 μg/L, and the correlation coefficient of paraquat and diquat was 0.9986 and 0.9980, respectively. The limits of detection of paraquat and diquat were 4.5 μg/L and 4.3 μg/L. The proposed MSPE-HPLC method was successfully applied to the detection of the paraquat and diquat in human plasma and urine with satisfied recoveries of PQ and DQ in the range of 87.5%-98.7%.

A novel electrochemical sensor based on Au nanoparticles/8-aminoquinoline functionalized graphene oxide nanocomposite for paraquat detection

In this paper, a novel electrochemical sensor based on Au nanoparticles/8-aminoquinoline functionalized graphene oxide (AuNPs/GAQ) nanocomposite was developed and tested for the first time for detection of paraquat (PQ). The morphology and composition of AuNPs/GAQ nanocomposite were characterized by various techniques, including transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy. Cyclic voltammetry and differential pulse voltammetry were utilized to investigate the electrochemical performances of AuNPs/GAQ nanocomposite modified glassy carbon electrode. The obtained modified electrode exhibited excellent electrocatalytic activity towards detection of PQ. Under the optimized conditions, the proposed sensor showed low detection limit (6 nM, S/N = 3), wide linear range (0.02-24 μM), high selectivity and good stability. In addition, it was successfully applied for detection of PQ in natural water samples with satisfactory results.

Paraquat Exposure of Pregnant Women and Neonates in Agricultural Areas in Thailand

This study aimed to assess paraquat concentrations in the urine of women at 28 weeks of pregnancy, delivery and 2 months postpartum and in the meconium of neonates. In all, 79 pregnant women were recruited from three hospitals located in agricultural areas in Thailand. The subjects were interviewed about personal characteristics, agricultural activities and pesticide use patterns. Paraquat was analyzed in urine and meconium using high performance liquid chromatography equipped with a fluorescence detector. The geometric mean (GSD) of urinary paraquat concentrations at 28 weeks of pregnancy, delivery and 2 months postpartum were 2.04 (4.22), 2.06 (5.04) and 2.42 (5.33) ng/mL, respectively. The urinary paraquat concentrations at 28 weeks of pregnancy, delivery and 2 months postpartum between agriculturist and non-agriculturist were not significantly different (p = 0.632, p = 0.915, p = 0.57, respectively). The geometric mean (GSD) of paraquat concentration in the meconium was 33.31 (4.59) ng/g. The factors predicting paraquat exposures among pregnant women and neonates included working outside, living near farmland, having family members who work on a farm, drinking well water and using herbicides or paraquat.

Human and experimental toxicology of diquat poisoning: Toxicokinetics, mechanisms of toxicity, clinical features, and treatment

Diquat (1,1'-ethylene-2,2'-bipyridinium ion; DQ) is a nonselective quick-acting herbicide, which is used as contact and preharvest desiccant to control terrestrial and aquatic vegetation. Several cases of human poisoning were reported worldwide mainly due to intentional ingestion of the liquid formulations. Its toxic potential results from its ability to produce reactive oxygen and nitrogen species through redox cycling processes that can lead to oxidative stress and potentially cell death. Kidney is the main target organ due to DQ toxicokinetics and redox cycling. There is no antidote against DQ intoxications, and the efficacy of treatments currently applied is still unsatisfactory. The aim of this work was to review the most relevant human and experimental findings related to DQ, characterizing its chemistry, activity as herbicide, mechanisms of toxicity, consequences of poisoning, and potential therapeutic approaches taking into account previous experience in developing antidotes for paraquat, a more toxic bipyridinium herbicide.

Clinical screening of paraquat in plasma samples using capillary electrophoresis with contactless conductivity detection: Towards rapid diagnosis and therapeutic treatment of acute paraquat poisoning in Vietnam

The employment of a purpose-made capillary electrophoresis (CE) instrument with capacitively coupled contactless conductivity detection (C⁴D) as a simple and cost-effective solution for clinical screening of paraquat in plasma samples for early-stage diagnosis of acute herbicide poisoning is reported. Paraquat was determined using an electrolyte composed of 10mM histidine adjusted to pH 4 with acetic acid. A detection limit of 0.5mg/L was achieved. Good agreement between results from CE-C⁴D and the confirmation method (HPLC-UV) was obtained, with relative errors for the two pairs of data better than 20% for 31 samples taken from paraquat-intoxicated patients. The results were used by medical doctors for identification and prognosis of acute paraquat poisoning cases. The objective of the work is the deployment of the developed approach in rural areas in Vietnam as a low-cost solution to reduce the mortality rate due to accidental or suicidal ingestion of paraquat.

Fast determination of paraquat in plasma and urine samples by solid-phase microextraction and gas chromatography-mass spectrometry

A simple, sensitive and reliable gas chromatographic-mass spectrometric method (GC-MS) for quantifying paraquat concentration in biological samples has been developed, using ethyl paraquat as an internal standard. The method involved the procedures of sodium borohydride-nickel chloride (NaBH4-NiCl2) reduction and solid-phase microextraction (SPME) of the perhydrogenated products. GC-MS was used to identify and quantify the analytes in selected ion monitoring (SIM) mode. Under the optimal conditions, recoveries in plasma and urine samples were 94.00-99.85% and 95.00-100.34%, respectively. Excellent sample clean-up was observed and good linearities (r=0.9982 for plasma sample and 0.9987 for urine sample) were obtained in the range of 0.1-50μg/mL. The limits of detection (S/N=3) were 0.01μg/mL in plasma and urine samples. The intra-day precision was less than 8.43%, 4.19% (n=3), and inter-day precision was less than 10.90%, 10.49% (n=5) for plasma and urine samples, respectively. This method was successfully applied to the analysis of the biological samples collected from a victim who died as a result of ingestion of paraquat.

Simple and sensitive liquid chromatography-tandem mass spectrometry methods for quantification of paraquat in plasma and urine: application to experimental and clinical toxicological studies

Simple, sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods have been developed and validated for quantification of paraquat (PQ) in plasma and urine. Plasma and urine sample preparation were carried out by one-step protein precipitation using cold acetonitrile (-20 to -10 °C). After centrifugation, an aliquot of 10 μL of supernatant was injected into a Kinetex™ hydrophilic interaction chromatography (HILIC) column with a KrudKatcher™ Ultra in-line filter. The chromatographic separation was achieved using the mobile phase mixture of 250 mM ammonium formate (with 0.8% aqueous formic acid) in water and acetonitrile at a flow rate of 0.3 mL/min. Detection was performed using an API2000 triple quadrupole tandem mass spectrometer in multiple reaction monitoring (MRM) mode via an electrospray ionization (ESI) source. The calibration curve was linear over the concentration range of 10-5000 ng/mL, with an LLOQ of 10 ng/mL. The inter- and intra-day precision (% R.S.D.) were <8.5% and 6.4% for plasma and urine, respectively with the accuracies (%) within the range of 95.1-102.8%. PQ in plasma and urine samples was stable when stored at -70 °C for three freeze-thaw cycles. The methods were successfully applied to determine PQ concentration in rat and human samples.

Enzymatic-spectrophotometric determination of paraquat in urine samples: a method based on its toxic mechanism

Paraquat is a broad-spectrum contact herbicide that has been encountered worldwide in several cases of accidental, homicidal, and suicidal poisonings. The pulmonary toxicity of this compound is related to the depletion of NADPH in the pneumocytes, which is continuously consumed by the reduction/oxidation of paraquat and reductase enzyme systems in the presence of O(2) (redox cycling). Based on this mechanism, an enzymatic-spectrophotometric method was developed for the determination of paraquat in urine samples. The velocity of NADPH consumption was monitored at 340 nm, every 10 s during 15 min. The velocity of NADPH oxidation correlated with the paraquat levels found in samples. The enzymatic-spectrophotometric method showed to be sensitive, making possible the detection of paraquat in urine samples at concentrations as low as 0.05 mg/L.

Supercritical fluid extraction as an on-line clean-up technique for rapid amperometric screening and alternative liquid chromatography for confirmation of paraquat and diquat in olive oil samples

A rapid and simple method for the direct screening of paraquat (PQ) and diquat (DQ) in olive oil samples is proposed. The sample screening method involves supercritical fluid extraction (SFE) (clean-up followed by the extraction of the analytes) followed by continuous flow electrochemical detection. Those samples for which the total concentration is close to or above the threshold limit established by the Columbian Society for Social Protection (0.05 microg g(-1)) are subsequently analyzed by liquid chromatography (LC) with diode array detection (DAD). This confirmation method allows the determination of PQ and DQ in the range between 0.04 and 1.0 microg g(-1), with average relative standard deviations lower than 3.5%, and 0.003 and 0.002 microg g(-1) detection limits for PQ and DQ, respectively. The proposed arrangement opens up interesting prospects for the direct determination of polar pesticides in complex samples with a good throughput and a high level of automation.

Determination of quaternary ammonium herbicides in soils. Comparison of digestion, shaking and microwave-assisted extractions

Very challenging analytical problems arise from the continuous introduction in agriculture of chemical pesticides. Particularly, diquat (DQ), paraquat (PQ) and difenzoquat (DF) are a difficult group of quaternary ammonium herbicides to analyze. This article reviews and addresses the most relevant analytical methods for determining the selected herbicides in soil. We discuss and critically evaluate procedures, such as digestion-based methods, shaking extraction and microwave-assisted extraction (MAE). Clean-up of extracts was performed by solid-phase extraction (SPE) using silica cartridges. Detection of these herbicides was carried out by liquid chromatography (LC) coupled to UV detection and mass spectrometry (MS) as confirmatory technique. Recoveries ranged from 98% to 100% by digestion, from no recovered to 61% by shaking, and from 102% to 109% by MAE with estimated quantification limits between 1.0 microg/kg and 2.0 microg/kg by digestion and 5.0 mug/kg and 7.5 microg/kg by MAE using LC/MS-MS as detection technique. The recoveries obtained under the optimum conditions are compared and discussed with those obtained from digestion extraction and MAE.

Gas chromatographic-mass spectrometric method for the determination of the herbicides paraquat and diquat in plasma and urine samples

In the present work, a method was developed and optimized aiming to determinate the herbicides paraquat (PQ) and diquat (DQ) in human plasma and urine samples. An initial procedure of chemical reduction of the analytes by adding NaBH4 directly in the buffered samples (pH 8.0) was performed. This procedure was necessary to convert the quaternary ammonium substances into more volatile compounds for gas chromatographic analysis. The reduction compounds were extracted with C18 cartridges (solid-phase extraction). Ethyl paraquat (EPQ) was used as internal standard (IS). Gas chromatography-mass spectrometry (GC-MS) was used to identify and quantify the analytes in selected ion monitoring (SIM) mode. The limits of detection were 0.05 mg/l for both PQ and DQ. By using the weighted least squares linear regression (1/x1/2 for plasma and 1/y for urine), the accuracy of the analytical method was improved at the lower end of the calibration curve (from 0.1 to 50 mg/l; r>0.98). This method can be readily utilized as an important tool to confirm the suspicion of PQ and/or DQ poisoning and evaluate the extent of the intoxication.

Method for Screening and Quantitative Determination of Serum Levels of Salicylic Acid, Acetaminophen, Theophylline, Phenobarbital, Bromvalerylurea, Pentobarbital, and Amobarbital Using Liquid Chromatography/Electrospray Mass Spectrometry

We investigated a method for the simultaneous screening, identification, and quantitative determination of salicylic acid, acetaminophen, theophylline, barbiturates, and bromvalerylurea, drugs that frequently cause acute poisoning in Japan and therefore require rapid analysis for effective treatment in the clinical setting. The method employs liquid chromatography/electrospray mass spectrometry (LC/MS) of solid-phase extracted serum samples. For LC/MS ionization, the electrospray-ionization method was used, with acetaminophen in the positive-ion mode, and salicylic acid, theophylline, phenobarbital, bromvalerylurea, pentobarbital, amobarbital, and o-acetamidophenol (internal standard) in the negative-ion mode, the base ions were used in each case for quantitative analysis. Quantitation was possible for the following sample concentration ranges: salicylic acid and acetaminophen, 100 to 5 microg/ml; theophylline, 100 to 0.5 microg/ml; and phenobarbital, bromvalerylurea, pentobarbital, and amobarbital, 100 to 1 microg/ml. Using full-scan mass spectrometry, the lower detection limits of 1 microg/ml for salicylic acid and acetaminophen, 0.1 microg/ml for theophylline, and 0.5 microg/ml for phenobarbital, bromvalerylurea, pentobarbital, and amobarbital were adequate for identifying acute poisoning. When each compound was added to serum to a final concentration of 5 microg/ml and solid-phase extraction was performed using Oasis HLB 1-cc (30-mg), the mean recovery rate of each compound was 89.2 to 96.1% (n=5), and the coefficients of variation of the intraday and interday assays were 3.55 to 6.05% (n=5) and 3.68 to 6.38% (n=5), respectively, which are acceptable. When this method of analysis was applied in testing the sera of a female patient who had consumed a large amount of an unknown commercial drug, salicylic acid and bromvalerylurea were identified, and the treatment strategy could be determined in accordance with the serum concentration of those drugs.