Shafi Muhammad Nizamani

Rapid detection of melamine adulteration in dairy milk by SB-ATR-Fourier transform infrared spectroscopy

Melamine is a nitrogenous chemical substance used principally as a starting material for the manufacture of synthetic resins. Due to its very high proportion of nitrogen melamine has been added illegitimately to foods and feeds to increase the measured protein content, which determines the value of the product. These issues prompted private as well as governmental laboratories to develop methods for the analysis of melamine in a wide variety of food products and ingredients. Owing to this fact present study is aimed to use single bounce attenuated total reflectance (SB-ATR) Fourier transform infrared spectroscopy (FTIR) method as an effective rapid tool for the detection and quantification of melamine in milk (liquid and powder). Partial least-squares (PLS) models were established for correlating spectral data to melamine concentration with R(2)>0.99, and RMSEC 0.370. Linear calibration curves were obtained over the calibration range of 25-0.0625%. The LOD and LOQ of the method was 0.00025% (2.5 ppm) and 0.0015% (15 ppm) respectively. Proposed SB-ATR-FTIR method requires little or no sample preparation with an assay time of 1-2 min.

Complete degradation of dimethyl phthalate by biochemical cooperation of the Bacillus thuringiensis strain isolated from cotton field soil

Dimethyl phthalate (DMP), a phthalate ester, is widely used in cosmetics, perfumes, and plasticizers. It has been classified as a suspected endocrine disruptor by many countries. The present study describes the biodegradation of DMP by a new aerobic bacterium, isolated from soil samples of a cotton field by an enrichment culture technique utilizing DMP as the sole source of carbon and energy. The isolate was identified as Bacillus thuringiensis based on the morphological and biochemical characteristics as well as gene sequence analysis. Bacillus thuringiensis grows best in a mineral salt medium of pH 7.0 at 30 °C incubation for 48 hours. The effects of temperature, inoculum size, substrate concentration and incubation time on DMP degradation were also studied. Bacillus thuringiensis is able to biodegrade 400 mg L−1 of DMP under aerobic conditions with 99% degradation potential. A combination of GC and GC-MS analysis revealed a complete DMP biodegradation pathway. The results indicate that Bacillus thuringiensis may prove a promising source for DMP bioremediation at a commercial scale.

Molecularly imprinted surface plasmon resonance (SPR) based sensing of bisphenol A for its selective detection in aqueous systems

Bisphenol A (BPA) imprinted poly(ethylene glycol dimethacrylate-N-methacryloyl-L-phenylalanine-vinyl imidazole) [poly(EGDMA-MAPA-VI)] film deposition on a SPR sensor with improved efficiency is described in this paper. The molecularly imprinted SPR sensor was characterized by FTIR-ATR, atomic force microscopy and ellipsometry. A water-compatible molecularly imprinted film has been developed for rapid, sensitive, and label-free detection of BPA in aqueous solutions prepared in Milli Q water, tap water and synthetic wastewater. The real-time response allows the detection of BPA with concentrations ranging from 0.08 to 10 μg L−1 with LOD and LOQ values of 0.02 and 0.08 μg L−1 in Milli Q water, 0.06 and 0.2 μg L−1 in tap water and 0.08 and 0.3 μg L−1 in synthetic wastewater, respectively. A significant increase in sensitivity was therefore expected due to the use of the imprinted poly(EGDMA-MAPA-VI) thin film. The method showed good recoveries and precision for the samples spiked with BPA. The results suggest that the imprinted SPR sensing method can be used as a promising alternative for the detection of BPA. The sensor data fitted well with the Langmuir adsorption model. The selectivity studies showed that the imprinted cavities formed in the polymeric nanofilm recognize BPA preferentially rather than 4-nitrophenol, hydroquinone, phenol and 8-hydroxy quinoline with a relative selectivity coefficient of 2.5, 2.6, 2.7 and 2.5, respectively. The prepared BPA imprinted SPR sensor enables high sensitivity, label-free detection, real-time monitoring, low volume sample consumption, quantitative evaluation, and determination of kinetic rate constants very well. In addition, the SPR based BPA sensor is easy to use and can be a cost effective solution due to the reusability of the prepared sensor. Furthermore, the storage stability will be higher than antibody-based detection methods.

Quick determination of melamine in infant powder and liquid milk by Fourier transform infrared spectroscopy

A simple, cost-effective and environmentally friendly analytical method was developed for the quantification of melamine (MEL) in liquid milk and infant powder by using transmission Fourier transform infrared (FT-IR) spectroscopy. Standards and samples were analyzed in the form of a KBr pellet for recording FT-IR spectra. Partial least squares calibration was established in the FT-IR region, 851.62–798.39 cm−1, with a linear range of 0.001–1%. An excellent coefficient of determination (R2) of 0.9999 was achieved, with minimum errors in the root mean square error of calibration and the root mean square error of prediction, for which the values were 0.17 and 3.49, respectively. The accuracy of the calibration model was also verified using the root mean square error of cross-validation, which was found to be 2.25. The limit of detection and the limit of quantification of the method were 0.0001% (1 ppm) and 0.00035% (3.5 ppm), respectively. The method was successfully applied to liquid and infant powder milk samples and gave good recoveries (98.9–100.2%). The FT-IR method developed here is efficient, accurate and appropriate for MEL detection in the dairy industry, with a reduced cost and a short analysis time.

Natural co-occurrence of aflatoxins and deoxynivalenol in poultry feed in Pakistan

Two hundred and fifteen broiler poultry feed samples were analysed over the time period of one year for the co-occurrence of aflatoxins and deoxynivalenol (DON). These were determined by GC–MS and ELISA, respectively. LOD values for aflatoxins and DON were 0.5 and 5 µg/kg, respectively. From all investigated 215 poultry feed samples, aflatoxins and DON co-occurred in 100 samples (46%). DON was detected in 114 samples while 100 samples also were positive for aflatoxins. Mean concentrations of positive samples for aflatoxins and DON were 18 and 807 µg/kg, respectively. Twenty-one DON-positive and 42 aflatoxin positive samples were contaminated above the EU maximum legal limits of 1000 µg/kg and 20 µg/kg, respectively. The present study provided useful data on aflatoxin and DON contamination, which may be helpful for future strategies to control contamination and to formulate standards in poultry feeds.

Contamination profile of aflatoxin M1 residues in milk supply chain of Sindh, Pakistan

Aflatoxin M1 (AFM1) is a potent carcinogen, teratogen and mutagen found in the milk when lactating animals consume feed contaminated with aflatoxin B1 (AFB1). In the present study, the contamination of AFM1 was evaluated in the milk supply chain of the province of Sindh, Pakistan. For the broader profiling of targeted toxin, enzyme-linked immunosorbent assay (ELISA) was used for the determination of AFM1 in both branded and non-branded milk samples. The results showed that 96.43% of samples (81 out of 84) were contaminated with AFM1 in the range of 0.01–0.76 μg/L. The average contamination level was 0.38 μg/L. The determined values of AFM1 in the collected milk samples were above the standard limit of the European Commission while 70% of the samples exceeded levels established by United States regulations. According to these results, the estimated daily intake of AFM1 for adults was determined as 3.1 ng/kg of body weight per day.

Decontamination of poultry feed from ochratoxin A by UV and sunlight radiations

BACKGROUND Mycotoxin-contaminated feed is very dangerous for the growth and even life of poultry. The objective of the current study was to investigate the efficacy of ultra-violet irradiation for decontamination of ochratoxin A (OTA) in spiked and naturally contaminated poultry feed samples. Spiked and naturally contaminated feed samples were irradiated with ultra-violet light (UV) at distance of 25 cm over the feed samples. In vitro, the effect of UV intensity (0.1 mW cm(-2) at 254 nm UV-C) on different types of poultry feeds contaminated with OTA was evaluated. The same samples were also irradiated with sunlight and analysed for OTA by an indirect enzyme linked immunosorbent assay method. RESULTS Poultry feed samples containing 500 µg kg(-1) were 100% decontaminated in 180 min with UV radiation while OTA was decreased to 70-95 µg kg(-1) using the same poultry feed samples after 8 h sunlight irradiation. Therefore, UV light was found to be more effective. Only 1 h of UV irradiation was found to be sufficient to bring the OTA level to the maximum regulatory limit suggested for poultry feeds (100 µg kg(-1) ), while 8 h were needed to obtain this level using sunlight radiations. CONCLUSION The proposed approach is a viable option to reduce the level of OTA in contaminated poultry feeds.

Synthesis and characterization of molecularly imprinted polymer embedded composite cryogel discs: application for the selective extraction of cypermethrins from aqueous samples prior to GC-MS analysis

Molecularly imprinted particles embedded composite cryogel discs specific for α-cypermethrin and β-cypermethrin were prepared. Two different types of imprinted particles were embedded into cryogel to prepare composite cryogels specific for two isomers of cypermethrin simultaneously. Adsorption studies revealed that MIP is extremely selective for α-cypermethrin and β-cypermethrin with outstanding adsorption capacity. A sensitive analytical method comprising MISPE coupled with GC-MS has been developed to quantify trace levels of α-cypermethrin and β-cypermethrin in real water matrices. The polymer showed fast kinetics and follows a pseudo-second-order kinetic model very well (R2 = 0.9999). It shows excellent capacity towards α-cypermethrin and β-cypermethrin with a higher total number of binding sites (Nt = 96 μmol g−1 for α-cypermethrin and 95 μmol g−1 for β-cypermethrin). The MIP showed selectivity over the homologues of α-cypermethrin and β-cypermethrin with imprinting factor (IF) 11.2, 10.0, 1.04 and 1.20 for α-cypermethrin, β-cypermethrin, deltamethrin and permethrin, respectively. The developed MISPE method followed by GC-MS enhanced the sensitivity and selectivity of the assay. This method was successfully applied to samples of lake water for the determination of α-cypermethrin and β-cypermethrin simultaneously. Moreover, the synthesized MIP can be easily regenerated and repeatedly used without loss of efficiency.

Investigation of Dissipation, Adsorption, Degradation, and Leaching of Triazophos Pesticide in Various Soils

This study concerns the investigation of dissipation, adsorption, and degradation of triazophos in different soils from Pakistan. These processes help in the disappearance of pesticide from the environment. Gas chromatography was used for dissipation and adsorption analysis while for degradation study mass spectrometer was used in addition of gas chromatography (GC-MS). The dissipation rate of triazophos in three different soils was 90% over 30 days with average half-life of 9.059 days. From dissipation study it was inferred that rate is variable in each soil due to climatic changes, soil nature and soil-pesticide interactions. Adsorption experiment has revealed that the adsorption of this pesticide to soil follows the pseudo first order kinetic model with rate constant value of 0.479/h and Freundlich isotherm with adsorption capacity of 1.832 mol/g. Degradation study has displayed two major metabolites, one is phosphorothioic acid, S-[2-[(1-cyano-1-methylethyl) amino]-2-oxoethyl] O,O-diethyl ester at retention time of 9.136 and the other is sulfotep at 14.304 min. The leaching potential of triazophos was also calculated from its half-life and organic carbon content present in soil which was 1.688 representing it as non leacher pesticide.

Banana peel: an effective biosorbent for aflatoxins

ABSTRACT This work reports the application of banana peel as a novel bioadsorbent for in vitro removal of five mycotoxins (aflatoxins (AFB1, AFB2, AFG1, AFG2) and ochratoxin A). The effect of operational parameters including initial pH, adsorbent dose, contact time and temperature were studied in batch adsorption experiments. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and point of zero charge (pHpzc) analysis were used to characterise the adsorbent material. Aflatoxins’ adsorption equilibrium was achieved in 15 min, with highest adsorption at alkaline pH (6–8), while ochratoxin has not shown any significant adsorption due to surface charge repulsion. The experimental equilibrium data were tested by Langmuir, Freundlich and Hill isotherms. The Langmuir isotherm was found to be the best fitted model for aflatoxins, and the maximum monolayer coverage (Q0) was determined to be 8.4, 9.5, 0.4 and 1.1 ng mg−1 for AFB1, AFB2, AFG1 and AFG2 respectively. Thermodynamic parameters including changes in free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) were determined for the four aflatoxins. Free energy change and enthalpy change demonstrated that the adsorption process was exothermic and spontaneous. Adsorption and desorption study at different pH further demonstrated that the sorption of toxins was strong enough to sustain pH changes that would be experienced in the gastrointestinal tract. This study suggests that biosorption of aflatoxins by dried banana peel may be an effective low-cost decontamination method for incorporation in animal feed diets.