Optimization of the liquid–liquid extraction method and low temperature purification (LLE–LTP) for pesticide residue analysis in honey samples by gas chromatography

This work optimized a simple and practical method for identification and quantification of the pesticides chlorpyrifos, λ-cyhalothrin, cypermethrin and deltamethrin in honey samples. The method was based on liquid–liquid extraction and low temperature purification using acetonitrile: ethyl acetate (6.5 mL:1.5 mL) as the solvent for extraction. A final clean up step with 2 g florisil was performed before analysis by gas chromatography using electron-capture-detector. The technique was proven satisfactory with efficiency exceeding 85% and linear chromatographic response for the tested pesticides, ranging from 0.033 to 1.7 μg g⁻¹ with correlation coefficients above 0.99. Detection and quantification limits were lower than 0.016 and 0.032 μg g⁻¹, respectively. The proposed method was applied to 11 honey samples. Chlorpyrifos and λ-cyhalothrin residues were found in two samples at concentrations below maximum residue limit (MRL) established for food products. The presence of these compounds was confirmed by mass spectrometry in SIM mode (GC–MS-SIM).     

Occurrence of aflatoxin M1 in pasteurised,UHT milk and milk powder from goat origin

In the present study, 36 samples of pasteurised, ultra-high-temperature (UHT) treated and goat milk powder traded in the city of Campinas, Brazil, were analysed for aflatoxin M₁ (AFM₁), from October to December 2004 and March to May 2005. Results showed 25 (69.4%) positive samples for AFM₁ at levels of 0.011–0.161 μg L⁻¹ of milk, which were below the tolerance limit of 0.500 μg L⁻¹ as adopted for AFM₁ in milk by Brazilian regulations. Mean levels of AFM₁ in pasteurised, UHT and goat milk powder were 0.072 ± 0.048, 0.058 ± 0.044 and 0.056 ± 0.031 μg L⁻¹, respectively. It is concluded that the incidence of AFM₁ in goat milk traded in Campinas is high, but at levels that probably leads to a non-significant human exposure to AFM₁ by consumption of goat milks.     

Antimicrobial effect of acidified sodium chlorite,sodium chlorite,sodium hypochlorite,and citric acid on Escherichia coli O157:H7 and natural microflora of fresh-cut cilantro

Fresh-cut cilantro is particularly susceptible to microbial growth and, therefore, use of an effective sanitizer on this product is of great importance. The objective of this study was to evaluate the efficacy of different sanitizing treatments on reducing Escherichia coli O157:H7 populations, aerobic mesophilic bacterial, yeast and mould counts on fresh-cut cilantro. Cut cilantro was treated with sodium hypochlorite (SH) at 0.2 g L^?1 free chlorine and acidified sodium chlorite (ASC) at 0.1, 0.25, 0.5 and 1 g L^?1, along with the components of ASC, i.e., citric acid (CA) at 6 g L^?1 and sodium chlorite (SC) at 1 g L^?1. In the present study, it was found that SH inactivated, at maximum, 1–1.3 log cfu g^?1 of background or pathogenic microflora present on cut cilantro. However, reductions of more than 3 log cfu g^?1 were observed after washing with 1 g L^?1 of ASC. Moreover, when lower concentrations of ASC were used (0.25 and 0.5 g L^?1), microbial populations were reduced by about 2 log cfu g^?1. SC was as effective as ASC at 1 g L^?1 in reducing aerobic mesophilic bacteria and E. coli O157:H7 populations, although it was not as effective as ASC in reducing yeast and mould populations.     

Optimization,kinetics, physicochemical and ecotoxicity studies of Fenton oxidative remediation of hydrocarbons contaminated groundwater

Fenton oxidation remediation of hydrocarbons contaminated groundwater was investigated for efficiency and effectiveness. 10% pollution was simulated in the laboratory by contaminating groundwater samples with diesel and domestic purpose kerosene (DPK) in two different experimental set ups. Optimum conditions of concentrations of the treatment solutions and pH were established: 300 mg/L (FeSO₄), 150,000 mg/L (H₂O₂) and pH = 3 for the kerosene contaminant; 100 mg/L (FeSO₄), 300,000 mg/L (H₂O₂) and pH = 3 for the diesel contaminant. The results from kinetics study show that the remediation process is pseudo-first order reaction with a rate constant of 8.07 × 10⁴ mgL^?1hr^?1 and 3.13 × 10⁴ mgL^?1hr^?1 for the diesel and kerosene contaminants in that order with 95.32% and 79.25% reduction in chemical oxygen demand (COD) for diesel and kerosene contaminated samples at the end of the remediation process respectively indicated that remediation have occurred significantly. Percent reduction in Total Petroleum Hydrocarbon (TPH) as kerosene was 89.84% and that of the diesel contaminant as 91.87% after 6 hours of remediation. The general pollution index (GPI) for the hydrocarbons contaminated samples was in the range of 6.70–7.52 against the background value of 4.39 for the control groundwater sample. After treatment the GPI had dropped to 4.13–4.43 which depicts remarkable remediation although the samples remained impaired. Therefore there is the need of post-treatments to make the groundwater fit for domestic and agricultural uses. The application of the Fenton oxidative process is found to be very efficient, effective and rapid in reducing total petroleum hydrocarbon as kerosene and diesel as target contaminants.     

Kinetics of thermal degradation of a Japanese oil sand

Thermal degradation characteristics of a Japanese oil sand at different heating rates (10, 20, and 30 °C/min), and 30 ml/min air flow rate have been investigated. The kinetic parameters have been calculated based on three stages of weight loss and/or the conversion of the sample. These include, stage 1 (SI): volatilization of moisture content and the light hydrocarbon (20–227 °C), stage 2 (SII): combustion of heavy hydrocarbon (227–527 °C), and stage 3 (SIII): oxidative decomposition of carbonaceous organic matter (502–877 °C). The results showed that the rate of change of the oil sand conversion with time $\left(\frac{d\alpha }{\mathit{dt}}\right)$ was affected by the heating rate. The time taken by the system to reach 0.99 conversion was observed as 85, 50, and 35 min at the heating rates of 10, 20, and 30 °C/min, respectively. The frequency factor, A, at SI was between 0.09 and 0.54 min^?1, while the activation energy, E_a, was 11.2–12.5 KJmol^?1 (the percentage weight loss, W_t, was 0–3.6 %w/w; and the conversion, α, was 0–0.2.). At SII, the values of A and E_a were 2.1–5.5 min^?1 and 17.6–19 KJmol^?1, respectively (W_t = 3.1–15.88 %w/w; α = 0.17–0.86.). The value of A at SIII was 5.5E11–1.1E13 min^?1, while E_a was 160–200 KJmol^?1 (W_t = 15.33–17.99 %w/w; and α = 0.84–0.99).     

Solid-phase extraction and HPLC determination of Ochratoxin A in cereals products on Chilean market

Ochratoxin A (OTA) is a mycotoxin produced by different species of Aspergillus and Penicillium fungi. The presence of this mycotoxin in cereals-based products has relation with manufacturing practices, especially with storage conditions. An extraction procedure for OTA from wheat-based products was implemented in this study. The method uses an alkaline extraction with NaHCO₃, purification with Sep-Pak^® RP-18 cartridges; and quantitative analysis by high performance liquid chromatography with fluorescence detection. The presence of OTA was confirmed by the formation of Ochratoxin A methyl ester. The method shows good validation parameters with a rate of recovery rate over 95%, limits of detection and quantification of 0.6 and 2.1 μg kg^?1, respectively. Once the method was validated; 31 samples including, flour, corn starches and rice were analyzed. About 70% of flour samples, 50% of rice and 63% of corn starch samples resulted positives for OTA.     

Kinetics and physicochemical studies of surfactant enhanced remediation of hydrocarbons contaminated groundwater

Kinetics and physicochemical studies of surfactant enhanced remediation of hydrocarbons contaminated groundwater were investigated for efficiency and effectiveness. 10% pollution was simulated in the laboratory by contaminating groundwater samples with crude oil, automatic gasoline oil (diesel) and domestic purpose kerosene (DPK) in replicates of five. Physicochemical properties of the hydrocarbons contaminated groundwater samples and a control sample were investigated before and after treatments. Total petroleum (TPH) hydrocarbon as target contaminant was monitored periodically to assess the extent of the remediation process. TPH was determined by molecular spectrophotometry technique. Other physicochemical parameters such as pH, turbidity, alkalinity, dissolved oygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), condutiivity, ammonia, nitrate, phosphate, salinity, total dissolved solids (TDS), total suspended solids (TSS) and total solids (TS) were obtained using standard methods while heavy metals levels were determined by atomic absorption spectrophotometry. Different kinetics models were tested to determine the appropriate kinetics model. The pseudo-first order kinetics is established with rate constant as 1.80 × 10⁴; 1.78 × 10⁴; 1.53 × 10⁴ mg^?1 L h^?1 for crude oil, diesel and kerosene respectively at 30 °C. At the end of the remediation after 6 h there was 89.11%; 93.21%; 87.76% reduction in TPH as crude oil, diesel and kerosene for the treated samples in that order. The application of surfactant enhanced remediation using sodium dodecyl sulphate is found be very efficient, effective and rapid in reducing total petroleum hydrocarbon as crude oil, kerosene and diesel as target contaminants. There is the need for post-treatments after remediation for most of the physicochemical parameters are impaired and do not meet the Guideline and Standards for Environmental Pollution Control in Nigeria set by Federal Ministry of Environment and World Health Organization for drinking water and agricultural uses in order to make them fit for these purposes.     

Microbiological quality of legume-based traditional fermented foods marketed in West Bengal,India

A total of 105 samples of six different types of legume-based popular fermented foods, namely amriti, dhokla, dosa, idli, papad and wadi, purchased from retail outlets in West Bengal, was analysed to determine their microbiological safety status. While dhokla and idli were of high-moisture foods (62 g (100 g)⁻¹), others had a lower moisture level (14–27 g (100 g)⁻¹). Papad was alkaline (pH 8.7), whereas all the other foods were acidic (pH 4.4–5.8). Every sample was found contaminated with total aerobic mesophilic bacteria (detection limit, 10 cfu g⁻¹); 38% (40/105) of the samples contained more than 10⁶ cfu g⁻¹. Aerobic mesophilic bacterial spores were found in 88% (92/105) of the samples (detection limit, 100 cfu g⁻¹), whereas their anaerobic counterparts were present in 39% (41/105) of the samples (detection limit, 10 cfu g⁻¹). Although all the samples, excepting one, were free from Staphylococcus aureus (detection limit, 100 cfu g⁻¹), 20% (21/105) of the samples were found contaminated with Bacillus cereus (detection limit, 100 cfu g⁻¹). Enterobacteriaceae were found in 46% (48/105) of the samples (detection limit, 10 cfu g⁻¹). Of the Enterobacteriaceae isolates, 92% were coliforms and 57% were faecal coliforms. Escherichia coli (detection limit, 10 cfu g⁻¹) was found in only one sample each of wadi and idli, at a load of 10³–10⁴ g⁻¹. Salmonella (detection limit, 1 cell (25 g)⁻¹) occurred in 12 samples of wadi, idli and papad, however was absent in the other three products. Clostridium perfringens (detection limit, 10 cfu g⁻¹) and Shigella (detection limit, 1 cell (25 g)⁻¹) could not be detected. The results obtained in the present study indicated that these foods were manufactured using poor-quality starting materials, processed under unhygienic conditions, or/and temperature-abused during transportation and storage. Based on these results, a guideline is recommended for obtaining safe products.     

Aflatoxins in rice – A limited survey of products marketed in Austria

Eighty-one rice samples were purchased from different markets in Vienna and were analysed for their aflatoxin content. The samples were extracted using methanol in water (80/20 v/v) followed by immunoaffinity clean up. The determination was carried out by HPLC–FLD coupled to a Kobracell. Different samples including basmati rice, whole grain rice, long grain rice, short grain rice as well as puffed rice were investigated. Moreover, conventionally and organically produced rice were compared. The results revealed that 24 out of 81 samples contained detectable amounts of aflatoxins. Aflatoxin B₁ could be quantified in 15 samples and aflatoxin B₂ in one sample. The contamination range was noted to be between 0.45 μg kg⁻¹ and 9.86 μg kg⁻¹ for aflatoxin B₁ and 1.5 μg kg⁻¹ for aflatoxin B₂. Aflatoxins G₁ and G₂ were not detected in any sample. Three samples exceeded the maximum levels set in the European Union; having AFB₁ concentrations of 2.16, 2.85 and 9.86 μg kg⁻¹. In the three organic produced rice samples only traces of aflatoxins were found.     

Simultaneous determination of melamine and cyanuric acid in dairy products by mixed-mode solid phase extraction and GC–MS

This report described a method for simultaneous determination of cyanuric acid (CYA) and melamine (MEL) in dairy products. The samples were extracted by a mixture of acetonitrile/water and cleaned by graphite carbon/strong cation exchange (CARB/SCX) mixed-mode solid phase extraction column. The CYA and MEL were derivatized with bis(trimethylsily1)trifluoroacetamide (BSTFA) containing 1% Trimethylchlorosilane (TMCS), and quantified with the internal standards of ¹⁵N₃-cyanuric acid and ¹³C₃-melamine by GC–MS. The results indicated that CARB/SCX mixed solid phase extraction column could be used for sample pretreatment. The fortification recoveries were 80.8–101.5%, and the relative standard deviations (RSDs) were 3.6–7.9%. The detection limits of CYA and MEL were 0.025 mg kg⁻¹ and 0.01 mg kg⁻¹ respectively.     

Determination of aflatoxin M1 in dairy cattle milk in Khartoum State,Sudan

Aflatoxins are a group of mycotoxins that contaminate various types of food and feedstuff leading to health risk in both humans and animals. Aflatoxin M1 (AfM1), the major metabolite of AfB1, was determined in dairy cattle milk samples of Khartoum State of Sudan using high-performance liquid chromatography (HPLC) with fluorescence detection. A total of 44 bulk dairy cattle milk samples were collected and analyzed. The percentage of AfM1 contamination has been found in 42/44 (95.45%) samples with contamination level ranging between 0.22 and 6.90 μg L⁻¹ and average concentration of 2.07 μg L⁻¹. AfM1 contamination in the samples of dairy cattle milk of Khartoum State of Sudan appears to be prevalent and may pose a public health problem at the moment. Awareness must be conveyed to producers, handlers and specialists.     

Aflatoxin B1 and ochratoxin A in breakfast cereals from athens market: Occurrence and risk assessment

A method for aflatoxin B₁ (AFB₁) and ochratoxin A (OTA) determination in breakfast cereals is described using a simultaneous methanolic-aqueous extraction followed by immunoaffinity columns clean-up step and High Pressure Liquid Chromatography (HPLC) with Fluorescence Detector (FD). Recoveries were found to be 78% and 83% for AFB₁ and OTA, respectively, while the detection limit (DL) was 0.02 ng g^?1 for both mycotoxins. Both determinations were applied in fifty five samples of breakfast cereals purchased from Athens market. Results revealed the presence of AFB₁ in 56.3% of the samples examined (mean 1.42 ng AFB₁ g^?1). Seven samples (median 3.5 ng AFB₁ g^?1) were found to be contaminated at levels higher than the EU limit (2 g g^?1). OTA was detected in 60% of the samples (mean 0.18 ng g^?1). Nineteen samples were found to be contaminated by both mycotoxins. In addition in the present study the daily exposure to AFB₁ and OTA is discussed.     

Evaluation of 10 pesticide residues in oranges and tangerines from Valencia (Spain)

One hundred and sixteen orange and tangerine samples from an agricultural cooperative of the Valencian Community (Spain) were analyzed for bitertanol, carbendazim, hexythiazox, imazalil, imidacloprid, methidathion, methiocarb, pyriproxyfen, thiabendazole, and trichlorfon by liquid chromatography–mass spectrometry (LC–MS) after a conventional multiresidue extraction procedure. Of 52 samples that contained pesticide residues, carbendazim was detected in 27 (51.9%) in the concentration range of 0.02–0.04 mg kg⁻¹, hexythiazox in 22 (42.3%) in the concentration range of 0.02–0.05 mg kg⁻¹, imazalil in 8 (15.0%) in the concentration range of 0.02–1.2 mg kg⁻¹, imidacloprid in 5 (9.6%) in a concentration range of 0.02–0.07 mg kg⁻¹ methidathion in 17 (32.6%) in the concentration range of 0.06–1.3 mg kg⁻¹, and methiocarb in 1 (2%) at a concentration of 0.02 mg kg⁻¹. Bitertanol, pyriproxyfen, thiabendazole and trichlorfon were not detected in any sample. Although 19 samples contained residues of two or three of the studied pesticides, no sample exceeded the European Maximum Residue Limits (MRLs). The results show that despite a high occurrence of pesticide residues in oranges and tangerines from Valencian Community, the contamination levels of these residues could not be considered a serious public health problem according to European Union (EU) regulations.     

Survey of aflatoxin B1 in helva,a traditional Turkish food,by TLC

A total of 102 helva samples consisting of 34 plain helva, 34 helva containing cacao, and 34 helva containing pistachio nuts purchased from helva-factories and supermarkets in Adana of Turkey were analysed for aflatoxin B₁ (AFB₁) by thin-layer chromatography. The detection limit of AFB₁ was 1 μg kg⁻¹. Recovery experiments were carried out with spiked samples in the range 2–10 μg kg⁻¹ of AFB₁. No AFB₁ was found in any plain helva and helva containing cacao samples. On the other hand, of 34 helva containing pistachio nuts AFB₁ was determined in eight samples. AFB₁ was found in excess of Turkish legal limit of 5 μg kg⁻¹ in 4 of 102 helva samples. This paper reports the data of the first survey for the presence of AFB₁ in helva in Turkey.     

Dissipation of propisochlor and residue analysis in rice,soil and water under field conditions

The analytical method for the residues of a new herbicide propisochlor and its dissipation and residual amounts in soil, water and rice plants in field conditions (rice cropping system) were studied. The chloroacetanilide herbicide, propisochlor (72% w/w EC) was applied at two dosages, 108 g a.i. ha⁻¹ (recommended) and 162 g a.i. ha⁻¹ (1.5 times of the recommended dosage) seven days after transplanting rice seedlings in the experimental fields in both Beijing and Fujian provinces (experimental localities). Soil, water and rice plant samples were collected at intervals and analyzed for propisochlor residues. The detection limit (LOD) of propisochlor is 0.2 μg kg⁻¹ and the limit of quantification (LOQ) was established as 1 μg kg⁻¹. At three different spiking levels, mean recoveries and relative standard deviation (RSD) from fortified samples in three replicated experiments for each matrix were in the range 81–109% and 1.3–13.1%, respectively. The results showed that the half-lives of propisochlor in water, soil and rice plant from Beijing were 0.56, 5.25 and 1.46 days respectively, and the half-lives of propisochlor in water, soil and rice plant from Fujian were 0.62, 5.12 and 0.81 days. At harvest, soil, straw, rice hull and husked rice samples were found to contain propisochlor well below the limit of detection (LOD) following the recommended dosage and 1.5 times dosage.     

Incidence and level of patulin contamination in pure and mixed apple juices marketed in Italy

A survey on the occurrence of patulin was conducted during 2005 on commercial pure apple juices (53 samples) and mixed apple juices (82 samples) marketed in Italy. The current study was undertaken to investigate the possible influence of the agro-food production process employed (conventional or organic), of the fruit percentage in the commercial product (higher or lower than 50%) and of the type of apple juice (clear or cloudy) on the occurrence and level of patulin contamination. Patulin could be quantified in 34.8% of the samples ranging from 1.58 to 55.41 μg kg⁻¹. With the exception of one sample, the level of patulin was lower than 50 μg kg⁻¹, the maximum permitted threshold in fruit juices according to the European legislation. Mean levels of patulin were significantly lower in mixed apple juices (4.54 μg kg⁻¹) than in pure apple juices (9.32 μg kg⁻¹). Levels of patulin contamination were comparable in clear and cloudy juices. A similar incidence of positive samples was found in conventional and organic apple based juices, and the magnitude between the mean contamination levels, although higher in organic (10.92 μg kg⁻¹) than in conventional juices (4.77 μg kg⁻¹), was not statistically significant (p = 0.771; Mann–Whitney test). The magnitude between the means of patulin contamination in juices containing more than 50% fruit (11.26 μg kg⁻¹) and in juices with 50% or less fruit (3.35 μg kg⁻¹) was statistically significant (p = 0.016; Mann–Whitney test).     

Determination of Listeria monocytogenes growth potential on new fresh salmon preparations

The aim of this work was to evaluate the increase of Listeria monocytogenes on new salmon preparations (salt–sugar–pepper–dill salmon) in comparison with that obtained on cold-smoked salmon. Salmon preparations were inoculated with L. monocytogenes and were analyzed during storage at 4 °C then 8 °C. At 8 °C, the bacteria growth was of 4.53 log CFU g⁻¹ in cold-smoked salmon and of 2.06 log CFU g⁻¹ in salt–sugar–pepper–dill salmon without background microflora. The growth of L. monocytogenes was different in new salmon preparation because the mixture salt–sugar–pepper had an anti-Listeria activity and its presence could inhibitory to the growth. It is difficult to generalize findings observed with cold-smoked salmon to a new salmon preparation.     

A sensitive and validated method for determination of melamine residue in liquid milk by reversed phase high-performance liquid chromatography with solid-phase extraction

A sensitive and validated method for the determination of melamine residue in liquid milk is developed using reversed phase high-performance liquid chromatography-diode array detection (RP-HPLC-DAD) with solid-phase extraction (SPE). The conditions of the extraction, SPE and HPLC were investigated and optimized. The linearity is satisfactory in the range of 0.1–50 μg/mL with a correlation coefficient of 0.9998. Under the optimal conditions, the method limit of detection (LOD) and method limit of quantification (LOQ) were 18 μg/kg and 60 μg/kg, respectively. The recovery of melamine for milk samples spiked with 0.10–3 mg/kg was in the range of 85.5–99.3% with the RSDs (n = 3) of 2.3–3.7%. The intra-day assay precision (RSD) was 5.6% for five replicates of quality control milk sample at 2 mg/kg level. Confirmation of the identities of melamine was achieved by monitoring the two transitions in multiple-reaction monitoring (MRM) mode, and has been applied successfully for the determination of melamine residue in liquid milk samples. The confirmatory method can permit the detection of melamine residues at levels as low as 60 μg/kg in different liquid milks.     

Pressurized fluid extraction for quantitative recovery of aflatoxins B1 and B2 from pistachio

A pressurized fluid extraction method for the extraction of aflatoxins B₁ and B₂ from contaminated pistachio samples was developed using a modified supercritical fluid extractor. The parameters of temperature, pressure, and flow rate of the solvent were optimized for the extraction process. The pressure variation in the range of (10–100) bar had an insignificant effect on the aflatoxins extraction yield. Solution of 80% (v/v) methanol in water as the extraction solvent at flow rate of 0.5 mL/min and temperatures of higher than 80 °C were obtained for efficient extraction of aflatoxins B₁ and B₂ from spiked and naturally contaminated pistachio samples. The developed method in comparison with the AOAC method offered the repeatability (RSD) of 13.5% and 12%, respectively, while the extraction yield or recovery of the analytes was about 20% higher corresponding to those obtained with the AOAC method. The higher recovery of the developed method was validated by HPLC analysis and it was also applied to the peanut samples analysis.     

Levels of polychlorinated dibenzo-p-dioxins,dibenzo-p-furans and polychlorinated biphenyls in farmed sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata) from Turkey

Farmed European sea bass and Gilthead sea bream were obtained from four different fish farms in Turkey during 2008–2009, for determination of 17 2,3,7,8-Cl-substituted PCDDs and PCDFs, and coplanar and indicator PCBs.Concentrations of ∑PCDD/Fs and DL-PCBs, as TEQ, in fish samples, ranged from 0.14 to 0.70 pg TEQ₍₁₉₉₈₎ g⁻¹ wet weight and from 0.46 to 4.51 pg TEQ₍₁₉₉₈₎ g⁻¹ wet weight, respectively. The concentrations of total indicator PCBs in fish samples ranged from 3.1 ng g⁻¹ to 22.1 ng g⁻¹ wet weight. Concentrations of PCDD/Fs and DL-PCBs were below the EU regulation (EC No. 1881/2006) limits.