High-performance Liquid chromatography-UV Research Articles

Development of a Formula to Correct Particle-Enhanced Turbidimetric Inhibition Immunoassay Values so That it More Precisely Reflects High-Performance Liquid Chromatography Values for Mycophenolic Acid.

BackgroundMycophenolic acid (MPA) concentration measured by homogeneous particle-enhanced turbidimetric inhibition immunoassay (PETINA) may be overestimated due to its cross-reactivity with pharmacologically inactive MPA glucuronide (MPAG), as well as other minor metabolites, accumulated with renal function impairment or co-administered cyclosporine A. In contrast, high-performance liquid chromatography (HPLC) is precise because it can exclude the cross-reactivity. In this study, we assumed HPLC values for MPA (HPLC-MPA) as a reference and aimed to develop a formula correcting PETINA values for MPA (PETINA-MPA) to more precisely reflect HPLC-MPA.MethodsMPA trough concentrations were measured both by HPLC-UV and PETINA in 39 samples issued from 39 solid-organ transplant recipients. MPAG concentrations were also measured using HPLC UV assay. We determined the impacts of renal function and coadministered calcineurin inhibitor on concentrations of MPA and MPAG measured by HPLC. Then, we evaluated the difference between PETINA-MPA and HPLC-MPA. Finally, we develop a formula to reflect HPLC-MPA by using multilinear regression analysis.ResultsMPAG concentration was negatively correlated with estimated glomerular filtration rate (eGFR) (R2 = 0.376, P < 0.001), although MPA was not correlated with eGFR. There were no significant differences in MPA or MPAG concentrations per dose between the patients who were co-administered tacrolimus versus cyclosporine A. Finally, we developed the formulas to reflect HPLC-MPA:Formula 1: Estimated MPA concentration = 0.048 + 0.798 × PETINA‐MPAFormula 2: Estimated MPA concentration = − 0.059 + 0.800 × PETINA‐MPA + 0.002 × eGFRHowever, there was no significant improvement in the coefficient of determination with addition of eGFR in the formula, suggesting that HPLC-MPA can be well predicted by only 1 variable, PETINA-MPA.ConclusionsThis study developed a formula so that PETINA-MPA can be corrected to more precisely reflect HPLC-MPA.

Selective removal of 2,4-dichlorophenol and 2,4,6-trichlorophenol in aqueous solutions by polyaniline-modified magnetic nanoparticles using high-performance liquid chromatography–UV detection

Selective removal of 2,4-dichlorophenol and 2,4,6-trichlorophenol in aqueous solutions by polyaniline-modified magnetic nanoparticles using high-performance liquid chromatography–UV detection

A molecularly imprinted polymer coupled with high-performance liquid chromatography-UV for the determination of albendazole in plasma and urine samples: CCD-RSM design

The present study attempted to develop a fast and sensitive ultrasound-assisted-dispersive-micro-solid phase extraction method for the separation and preconcentration of albendazole from plasma and urine samples.

Pharmacokinetics and bioavailability of marbofloxacin in lambs following administration of intravenous, intramuscular and subcutaneous

In this study, the pharmacokinetic disposition and bioavailability of marbofloxacin (MB) were determined in lambs after single intravenous (IV), intramuscular (IM), and subcutaneous (SC) administrations at a dose of 3 mg/kg. The plasma concentration of MB was measured using high-performance liquid chromatography-UV, and the pharmacokinetic parameters were analyzed using a non-compartmental analysis. Following IV, IM, and SC administrations, the mean terminal half-life (t1/2ʎz) was 11.48, 12.64, and 24.86 h, respectively, and the mean residence time (MRT) was 7.27, 7.81, and 10.11 h, respectively. The bioavailability (F) was 96.01 and 126.39%, after IM and SC administration, respectively. This study showed that SC administration of MB at a dose of 3 mg/kg exhibited flip-flop pharmacokinetics in lambs. These results suggested that MB could be useful in the treatment of severe systemic infections, such as those with M. haemolytica (MIC = 0.035 μg/mL), in lambs since high AUC0-24/MIC and Cmax/MIC ratios were achieved after IV and IM administration at 3 mg/kg. However, MB administration (3 mg/kg) via the IV, IM, and SC routes might not be effective in the treatment of respiratory infections caused by organisms with MIC90 value in lambs.

Ionic liquid-based cloud-point extraction of quercetin for its sensitive HPLC–UV determination in juice samples

An ionic liquid-based cloud-point extraction (IL-CPE) method was developed for the extraction of quercetin in juice samples before its determination by high-performance liquid chromatography (HPLC). 1-Butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) was used as the ionic liquid. The cloud-point extraction parameters such as sample pH, extraction temperature, extraction time, amount of ionic liquid, extraction volume, and salt concentration were carefully studied and optimized for the achievement of maximum extraction recovery. Under the optimized conditions, i.e., 20 min heating at 40 °C, 100 μL IL volume, pH 2.0, and no salt addition, a mean recovery of 92.5% and an enrichment factor of 20 were obtained for quercetin. Relative standard deviation of the method was 3.76% for 6 replicates, and the calculated detection limit (3σ) of quercetin was 0.002 mg L−1. The method, coupled to HPLC was successfully applied to the sensitive determination of quercetin in apple and gapes juice samples with quantitative recoveries.

Kinetics of diuron under aerobic condition and residue analysis in sugarcane under subtropical field conditions

ABSTRACTThe phenylureas group includes persistent herbicides which are major pollutants to soil and water. Dissipation kinetics of diuron in different soils under sugarcane field conditions was investigated. Diuron was extracted with acetone and florisil solid phase extraction clean-up and characterized by high-performance liquid chromatography-UV. Diuron persisted for more than 100 days and dissipation followed monophasic first-order kinetics. Persistence was more in sandy loam compared to silty clay loam soil. Half-life of diuron in silty clay loam soil was 22.57 and 32.37 days and in sandy loam was 28.35 and 43.93 days at 2 and 4 kg ha−1applications, respectively. Average recovery in soil, bagasse, leaf-straw and juice ranged from 75.95% to 84.20%, 80.15% to 89.35%, 77.46% to 86.19% and 81.88% to 92.68%, respectively. The quantitation limits for soil, bagasse, leaf-straw and juice were 0.01, 0.03, 0.04 μg g−1 and 0.008 μg mL−1, respectively. Application of diuron inhibited growth of soil microbes initially but they recovered later. At harvest, diuron residues were below maximum residue limits in all samples. The study revealed that under subtropical conditions, diuron is safe for use in weed management and would not pose any residual/environmental problem and that sugarcane crop could be used safe for human/animal consumption.

Hydroxymethylfurfural in fruit puree and juice: preconcentration and determination using microextraction method coupled with high-performance liquid chromatography and optimization by Box–Behnken design

In the present study, a sensitive and rapid method for separation and determination of hydroxymethylfurfural (HMF) in fruit puree and juices was proposed. Dispersive liquid–liquid microextraction (DLLME) coupled with high-performance liquid chromatography (HPLC) was used for extraction and quantitative determination of HMF in fruit puree and juices. The effective parameters such as the type and volume of extraction and dispersive solvents, pH and salt amount (NaCl) were studied and optimized with the aid of response surface methodology based on Box–Behnken design to obtain the best condition for HMF extraction. At the optimized conditions, parameter values were 60 µL extracting solvent, 600 µL dispersive solvent, 2 g NaCl and pH 5. Repeatability of the method, described as the relative standard deviation, was 3.1% (n = 6) and the recovery was 98.4%. The limit of detection and limit of quantitation were 1.47 and 5.28 µg L−1, respectively. The merit figures of DLLME–HPLC–UV method showed that the proposed method can be noticed as a new, fast and good alternative method for investigation of HMF in various fruit puree and juice samples.

Analytical method validation and monitoring of diacetyl in liquors from Korean market.

Diacetyl is a natural fermentation by-product and is an important flavor component of certain liquors. This paper aims to validate the high performance liquid chromatography (HPLC) method based on derivatization with 1,2-diaminobenzene for diacetyl quantification in liquor samples. A limit of quantitation of 0.039mg/L was obtained. Coefficient regression (R2) of calibration curve for the HPLC-UV method exceeded 0.999, showing adequate linearity on the standard curve. Relative standard deviation values obtained from intraday and interday analysis for precision were 2.5 and 4.1%, respectively. Using the validated method, the contents of diacetyl in liquors (12 types, 389 samples) distributed throughout Korea were monitored. The average diacetyl content of all analyzed liquor samples ranged from trace amounts to 3.655mg/L (microbrewery beer). The highest average diacetyl content was found in fruit wines (0.432mg/L), followed by red wine (0.320mg/L) and general distilled spirits (0.249mg/L). In takju and yakju, no distinctive effect of sterilization on diacetyl content was found.

High performance liquid chromatographic-UV method for determination of atorvastatin calcium in pharmaceutical formulations

High performance liquid chromatographic-UV method for determination of atorvastatin calcium in pharmaceutical formulations

Studies on reaction of reduced lipoic acid with Mukaiyama reagent and its application for pharmaceutical and food analysis

ABSTRACTA new sensitive method for the determination of lipoic acid (LA) in selected food items based on its reaction with Mukaiyama reagent (2-chloro-1-methylpyridinium iodide, CMPI) was developed. It was stated that CMPI reacts with reduced form of lipoic acid (dihydrolipoic acid, DHLA) and the stable product is produced. The spectrum of the labeled form of DHLA exhibits new band at 312 nm. Based on its spectral characteristics new spectrophotometric and UV–high-performance liquid chromatography (HPLC) methods of LA determination were elaborated. Both methods allowed determination of the analyte in the concentration range of 5 × 10−6–1 × 10−4 mol L−1 with limit of detection 0.39 × 10−6 and 0.77 × 10−6 mol L−1 for spectrophotometric and HPLC method, respectively. The practical usability of newly developed methods was checked by determination of lipoic acid contents in its pharmaceutical preparate Revitanerw. The proposed method was precise and accurate. The relative error of determination did not exceed ±0.067%. As chromatographic method allowed the determination of analyte in the presence of complex matrix, it was applied for assay of free fraction of α-lipoic acid in selected food items. A procedure of LA isolation from biological matrix was developed. The extraction with dichloromethane allowed quantitative recovery at 102.94 ± 4.20%. The green barley appeared to be the richest source of LA.

Preparation of three-dimensional mesoporous polymer in situ polymerization solid phase microextraction fiber and its application to the determination of seven chlorophenols

A superior solid-phase microextraction (SPME) fiber-coating material, three dimensional order mesoporous polymers with Ia-3d bicontinuous cubic structure (3D-OMPs) was in situ coated on a stainless steel wire by solvent evaporation induced self-assembly (EISA) and thermo-polymerization. Fourier-transform infrared spectrometry (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), small-angel X-ray diffraction (SAXRD), N2 adsorption-desorption transmission, and thermogravimetry analysis (TGA) were applied to the characterization of the synthesized 3D-OMPs coating. The performance and feasibility of the homemade fiber was evaluated through direct immersion (DI) SPME followed by high-performance liquid chromatography-UV detector (HPLC-UV) for the simultaneous extraction of seven chlorophenols in water samples. Under the optimum conditions, the prepared fiber exhibited excellent extraction properties as compared to three commercial fibers, the DI-SPME-HPLC-UV method showed low limits of detection (0.32–1.85μgL−1), wide linear ranges (5.0–1000μgL−1), and acceptable reproducibility (relative standard deviation, RSD<7.6% for one fiber, RSD<8.9% for fiber to fiber). Moreover, the method was further successfully applied to the analysis of seven CPs in real samples with good recoveries (80.5–99.5%) and satisfactory precisions (RSD<9.2%). It was confirmed that the proposed method has high sensitivity, outstanding selectivity and good reproducibility to the determination of trace CPs in the environmental water.

Determination of cobalt(II), nickel(II) and palladium(II) Ions via fabric phase sorptive extraction in combination with high-performance liquid chromatography-UV detection

ABSTRACTA method for the determination of Co(II), Ni(II) and Pd(II) in aqueous samples by fabric phase sorptive extraction-high-performance liquid chromatography-UV detection (FPSE-HPLC-UV) is developed. A preconcentration step was necessary due to the trace level concentrations of these elements in aqueous samples. Sol-gel polytetrahydrofuran nanocomposite was selected as the sorbent. All major FPSE parameters were optimized. The limit of detection for Co(II), Ni(II) and Pd(II) morpholino dithiocarbamate complexes were found at much lower concentration level compared with earlier reported data with excellent reproducibility. The new FPSE-HPLC-UV method can be used for routine determination of these metal species in various aqueous environmental samples and in different alloys.

A Simple High-Performance Liquid Chromatography for Determining Lapatinib and Erlotinib in Human Plasma.

Lapatinib and erlotinib are used for cancer treatment, showing large interindividual variability. Therapeutic drug monitoring may be useful for assessing the clinical outcomes and adverse events. A simple high-performance liquid chromatography UV method was developed for the determination of lapatinib and erlotinib in human plasma. An aliquot of plasma sample spiked with internal standard was treated with acetonitrile to precipitate the proteins. Lapatinib and erlotinib were separated on an octadecylsilyl silica gel column using a mobile phase consisting of acetonitrile, methanol, water, and trifluoroacetic acid (26:26:48:0.1) pumped at a flow rate of 1.0 mL/min. The detection wavelength was set at 316 nm. The calibration curves for lapatinib and erlotinib were linear (r = 0.9999) in the range of 0.125-8.00 mcg/mL. The extraction recoveries for both lapatinib and erlotinib at the plasma concentration of 0.125-8.00 mcg/mL were higher than 89.9% with coefficients of variation less than 3.5%. The coefficients of variation for intraday and interday assays of lapatinib and erlotinib were less than 5.1% and 6.1%, respectively. The present method can be used for blood concentration monitoring for lapatinib or erlotinib in exactly the same conditions.

P.2.b.028 - The importance of screening for depressive symptoms in patients with diabetes mellitus type 2 in primary health care

Because of its systemic action, fluconazole 1026 is prescribed for a variety of fungal infections. However, therapeutic failure might result when a patient is switched between an innovator drug and a nonbioequivalent generic formulation. Pharmacokinetic (PK) studies investigating the bioequivalence of generic and innovator drugs can minimize such risks.The aim of this study was to compare the 1026 PK profiles and relative bioavailabilities of 2 oral formulations of fluconazole: Diflucan® (reference; Pfizer Corporation Austria GmbH, Wien, Austria) and Funzol® (test; Bosnalijek d.d., Pharmaceutical and Chemical Industry, Sarajevo, Bosnia and Herzegovina), both prepared as capsules containing 150 mg of active drug.A single oral dose of fluconazole waMethods:026 given under fasting conditions to healthy, white volunteers aged 18 to 55 years in this open-label, randomized, crossover study. A 3-week washout period was applied between each of the 2 doses. Serum samples were obtained before dosing and at various time points after dosing up to 144 hours and were analyzed for fluconazole concentration using a high-performance liquid chromatography-UV method. PK parameters representing the extent (AUC0−∞) and rate (CmaX and Tmax) of absorption of fluconazole were obtained. An analysis of variance, a power analysis, 90% CI, and two 1-sided tests were used for statistical analysis of relative differences between the 2 drugs. Bioequivalence was concluded if the 90% CIs for the geometric mean ratios of AUC0−∞ and Cmax were between 0.80 and 1.25. A study investigator monitored the volunteers for adverse effects at 5 defined time points during the clinical part of the investigation.Thirteen men and 11 women (mean age, 1026 33.3 years; mean weight, 73.6 kg) completed the study. The respective point estimates of the ratios of geometric means of log-transformed Cmax and AUC00−∞ of fluconazole (test vs reference) were 0.985 and 1.047, with 90% CIs of 0.894 to 1.085 and 0.927 to 1.182, respectively. Differences in Tmax also did not reach statistical significance. No adverse effects were reported by the subjects or revealed by clinical or laboratory tests.The study failed to demonstrate any1026 statistically significant differences in Cmax and AUCO0−∞ values between the test and reference formulations of oral fluconazole 150 mg in this small, select population of healthy volunteers. On that basis, and according to both the rate and extent of absorption, the test and reference formulations were considered bioequivalent.

Ropivacaine, Interleukin-6 and Tumor Necrosis Factor Alpha Plasma Levels during Intermittent Epidural and Continuous Wound Infusion of Ropivacaine for Analgesia after Hysterectomy or Myomectomy: An Observational Study

Background/Aims: The concentration-time profile of the long-acting local anesthetic ropivacaine after epidural (EP) administration at fixed time intervals or continuous subcutaneous (SC) infusion has not been fully evaluated. The objective of this work was to determine total plasma concentrations of ropivacaine and changes in cytokine interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) levels during EP and SC. Methods: In this prospective randomized controlled trial, 18 patients undergoing abdominal hysterectomy or myomectomy were randomly selected to receive ropivacaine either every 6 h via an EP catheter or by continuous wound infusion along the skin incision, after a bolus dose, for 48 h. Total plasma ropivacaine concentrations were measured before the bolus and 2, 4, 8, 24, 48, and 50 h after the bolus using high-performance liquid chromatography-UV and IL-6 and TNF-α levels were measured at 0, 8 and 24 h with ELISA and analyzed statistically. Results: During EP, mean ± SD ropivacaine concentrations were relatively stable up to 50 h postoperatively, that is, 239 ± 89 ng/ml, while during SC, initial concentrations between 2 and 8 h were comparatively lower (101.5 ± 42.9 ng/ml) than 24-50 h concentrations (437.1 ± 206 ng/ml). An increase in IL-6 levels was noted between 0 and 24 h during EP and SC, but TNF-α levels increased slightly, between 0 and 24 h, only during EP. Conclusion: Ropivacaine plasma concentrations with both EP and SC were found to be safe throughout the administration time interval. IL-6 levels increased during the same time interval, while TNF levels varied only slightly.

Development of Carbon Nanotube-Polyamide Nanocomposite-based Stir Bar Sorptive Extraction Coupled to HPLC-UV Applying Response Surface Methodology for the Analysis of Bisphenol A in Aqueous Samples.

A novel nanocomposite based on reinforcing of multiwalled carbon nanotubes in polyamide (PA) was prepared by solvent exchange method as stir bar coating. The morphology and surface characteristic of PA and CNT/PA coated stir bars were investigated using scanning electron microscopy. The stir bar coated by CNT/PA nanocomposite was used as an extraction device for stir bar sorptive extraction of bisphenol A from aqueous samples followed by high performance liquid chromatography-UV detection. The effect of CNTs doping level and oxidation of CNTs on the extraction capability of the coating was investigated. Response surface methodology applying central composite design was used for modeling and optimization of important factors influencing the extraction and desorption processes including extraction time, salt and methanol content, desorption solvent, its volume and desorption time. Limit of detection and linear dynamic range of the method were 0.3 ng mL-1 and 1-10 ng mL-1, respectively. The method precision (RSD%) with four replicate determinations was 4.9% for distilled water at the concentration level of 10 ng mL-1 The obtained RSD% for reproducibility of stir bars was 7.4%. The developed method was successfully applied to the bottled mineral water samples, while the relative recoveries (RR%) were obtained to be in the range of 92.0-101.9%.

Ion-pair vortex assisted liquid-liquid microextraction with back extraction coupled with high performance liquid chromatography-UV for the determination of metformin in plasma

A new sample preparation method, ion-pair vortex assisted liquid-liquid microextraction (VALLME-BE), for the determination of a highly polar anti-diabetic drug (metformin) in plasma sample was developed. The VALLME-BE was performed by diluting the plasma in borate buffer and extracted to 150µL 1-octanol containing 0.2M di-(2-ethylhexyl)phosphoric acid as intermediate phase. The drug was next back-extracted into 20µL of 0.075M HCl solution. The effects of pH, ion-pair concentration, type of organic solvent, volume of extraction phases, ionic strength, vortexing and centrifugation times on the extraction efficiency were investigated. The optimum conditions were at pH 9.3, 60s vortexing and 2min centrifugation. The microextract, contained metformin and buformin (internal standard), was directly injected into a HPLC unit using C1 column (250mm×4.6mm×10µm) and detected at 235nm. The method was validated and calibration curve was linear with r2>0.99 over the range of 20–2000µgL−1. The limits of detection and quantitation were 1.4 and 4.1µgL−1, respectively. The accuracy was within 94.8–108% of the nominal concentration. The relative standard deviation for inter- and intra-day precision was less than 10.8%. The method was conveniently applied for the determination of metformin in plasma samples.

Outbreak of facio-troncular dystonia in central Africa due to diazepam replaced by haloperidol in oral medications

During week 52, 2014, in the north-east of the Democratic Republic of Congo, an African area included in the “Meningitis belt of Africa” and in which malaria is endemic, patients with suspected but atypical meningitis were reported. In January 2015, Médecins sans Frontières (MSF) Geneva, was approached by the Ministry of Health to support the outbreak. At the scene, data were collected on individual chart file records. Thereafter, at MoH and MSF case-management sites, information for each patient were recorded in a standardized Excel line-list. Patients’ demographic characteristics, clinical features, and discharge were recorded. At per request of the attending physician, cerebrospinal fluid was analysed for evidence of meningitis and blood for malaria. Toxicological analysis included liquid chromatography–Mass spectrometry and high performance liquid chromatography–UV spectrometry on urine specimens. Initial examination suggested that an illness other than bacterial meningitis was the cause of patients’complaints. Thereafter non-tonico-clonic seizures were considered. The MSF referent toxicologist was consulted. The definitive diagnosis made on pictures and videos. From January to August 2015, 1021 hospitalisations were recorded in 925 patients. Looking for the source of haloperidol showed that tablets sold as ‘diazepam’ and consumed by symptomatic patients contained haloperidol as the sole active pharmaceutical ingredient, suggesting that this large outbreak was due to haloperidol toxicity from falsified diazepam. However, the cause of the error is presently under investigation. This outbreak emphasizes the need to consider toxicity resulting from error in medicines when facing collective atypical signs and symptoms. To address such outbreaks, an international multidisciplinary collaboration, including clinical toxicologists, working in collaboration with medicine regulatory authorities is mandatory to address the major challenge of poor-quality drugs in developing countries. The mechanism and the cause of error in dosing are presently under investigation.

Selective and sensitive detection of tetrabromobisphenol-A in water samples by molecularly imprinted electrochemical sensor

A highly sensitive and selective electrochemical sensor for detecting trace tetrabromobisphenol-A (TBBPA) in water samples was fabricated using magnetic molecularly imprinted polymers (MMIPs). MMIPs were prepared via one pot sol–gel method and then used as recognition elements to prepare MMIPs-modified carbon paste (MMIPs/CP) electrode. Several parameters affected the preparation of MMIPs, and the imprinted sensor was described in detail. Synergistic effects of conductive magnetic nanoparticles and selective molecularly imprinted polymers (MIPs) improved the sensitivity and selectivity of the sensor. MMIPs/CP electrode exhibited excellent current response toward TBBPA, compared with the carbon paste electrodes made of magnetic non-molecularly imprinted polymers (MNIPs)/CP, traditional MIPs, non-molecularly imprinted polymers (NIPs) and CP. The prepared sensor also displayed good selectivity for TBBPA compared with structurally similar compounds. The linear range for determining TBBPA was from 5.0nM to 2000nM with the detection limit of 0.77nM (S/N=3). The developed sensor was successfully applied to directly detect TBBPA in tap water, rain, and pool water samples. The results were validated by high-performance liquid chromatography–UV spectrometry.

ASSESSMENT OF IMAZAPIC PRESENCE IN SURFACE WATER AND GROUNDWATER IN PADDY FIELD AREA

Herbicide is a well-known artificially synthesized substance used in paddy fields as an effective way to increase the quantity and quality of rice production by controlling the weedy rice in the field. In Tanjung Karang area, a new paddy strain was introduced to avoid weedy rice problem which requires farmers to apply herbicide containing imazapic and imazapyr which kills the weedy rice only but does not affect the new paddy strain. However, imazapic has the possibility to cause several health problems and also disrupting aquatic ecosystem. Hence, this research aims to carry out an extraction procedure and detection for imazapic residues in surface water and groundwater to assess its distribution in the study area. In this study, samples were collected from the surface water and groundwater for two consecutive seasons of paddy cultivation. After several clean-up and extraction procedure using solid-phase extraction (SPE) method, the water samples were analyzed using High Performance Liquid Chromatography-UV (HPLC-UV) for the presence of Imazapic residue. In 52.6% of the surface water samples and 51.8% of the groundwater samples, presence of imazapic residues was detected. This is a concern as it may possibly cause harm to the farmers. Results showed significant difference for the level of imazapic concentration detected in surface water during main season and off season (p-value=0.005, CI = - 0.39, 0.11). Thus, it can be concluded that the concentration of imazapic residue detected during main season (o.71 ug/ml) was higher compared to the samples collected during off season (0.57 ug/ml).