A screening method for sulfonamides extracted from animal tissues.

A screening method for the estimation of possible residues of sulfonamides in poultry tissues is described. The method utilizes thin layer chromatography (TLC) to separate Bratton-Marshall positive reactants. In the absence of interference and the identification of 1 sulfonamide by TLC, the colorimetric method is recommended for quantitation. When interferences are present, TLC should be used for both qualitative and quantitative analysis. The screening method has a sensitivity of less than 0.05 ppm and a recovery of greater than 80%.     

A screening method for determining nitrofuran drug residues in animal tissues.

A method was developed for measuring low levels of total nitrofurans in animal tissues and milk. The antimicrobial nitrofurans (5 or more products) used in agriculture are extracted from tissue with aqueous acid in the presence of ethyl acetate. After centrifugation and evaporation, the organic residue is washed with hexane and the nitrofurans are hydrolyzed to 5-nitrofuraldehyde in aqueous acid at 70 degrees C. The hydrolysis product is extracted with benzene and measured by gas-liquid chromatography with electron capture detection. Recoveries of nitrofurazone and furazolidone from fortified poultry and swine tissues at the levels of 0.5 and 0.1 ppm are 75 and 65%, respectively. This procedure can be used to detect the total nitrofuran content of as little as 10 ppb muscle tissues and milk, 100 ppb liver, and 50 ppb fat with no interference from related veterinary nitrodrugs.     

Rapid screening method for aflatoxins and zearalenone in corn.

The methanol-water extraction system used in AOAC Method II for aflatoxins extracts both the aflatoxins and zearalenone from corn. Using this methanol-water extraction system as a base, a rapid screening procedure has been developed for these mycotoxins. The methanol-water extract is defatted with hexane and the pigments are precipitated with copper carbonate. The aflatoxins and zearalenone are subsequently extracted into chloroform and are then detected by half-plate TLC. An elapsed time of about 1 hr is required to analyze 1 sample. The sensitivity of the method is about 2 mu-g/kg for aflatoxin B-1 and 100 mu-g/kg for zearalenone.     

Pollution-reduced Kjeldahl method for crude protein.

Pollution from the Kjeldahl method for crude protein has been reduced by substituting a low level of copper (0.04 g CuSO4) for the mercury (0.7 g HgO) specified in the AOAC official method, 2.049. Adjustments were made in the salt-acid ratio so the new system could handle hard-to-digest samples in a reasonable time. The new method was rugged for lysine. HCl. It is designed to be used for crude protein in feeds or similar Kjeldahl work. Precision and accuracy were equal to or better than that for the official method in a study of 17 samples analyzed in duplicate on 3 different days. The following samples were used in the study: lysine. HCl, tryptophan, NBS standards, urea, meals, mixed feeds, grains, and forage. The average per cent nitrogen found was 9.52 by the official method and 9.53 by the copper method. The average standard deviation was 0.038 by the official method and 0.033 by the copper method, giving the corresponding relative standard deviations of 0.40 and 0.35%.     

A rapid spectrofluorometric screening method for enrofloxacin in chicken muscle

A simple spectrofluorometric method was developed for screening enrofloxacin (ENRO) in chicken muscle. A single-step extraction with acidic acetonitrile gave the best results without further cleanup. Following centrifugation the supernatants were excited at 324 nm and the emission was measured at 442 nm. Using this procedure, 18 chicken breast samples from 3 producers were tested. The results showed background signal levels significantly lower than those corresponding to 300 microg/kg ENRO, the FDA approved tolerance level. Statistical treatment of these data established a threshold which can be used in subsequent screening of ENRO at the tolerance level. The calibration curve revealed a satisfactory linear relationship (R(2) = 0.9991) in a range of 0-700 microg/kg ENRO in fortified chicken breast. ENRO-incurred samples were examined using this approach, and the results agreed with those obtained from more extensive separation followed by high-performance liquid chromatography. Because the threshold can be set at the 3 sigma limit, reliable screening can be accomplished with an error rate of less than 0.26%. Based on this investigation, a high-throughput screening method for ENRO in chicken tissue is proposed.     

Rapid screening method for detection of deoxynivalenol

A rapid method for detecting deoxynivalenol (DON), also known as vomitoxin, was developed. DON was extracted from grains and other samples with acetonitrile-4% potassium chloride solution (9 + 1). Impurities that would interfere with detection were removed on a C18 silica gel reverse phase column. Water was removed from eluates on a hydrophilic matrix column. DON was detected by thin layer chromatography using an aluminum chloride solution to develop the blue response characteristic of the mycotoxin. Total time involved is approximately 30 min. The method was applicable to corn, wheat, and barley at detection levels of 1 ppm, and oats at 1.5 ppm. It is applicable to environmental samples (soil, green plants, and water) at detection levels of 0.75 ppm.     

Ultrafast capillary electrophoretic analysis of cereal storage proteins and its applications to protein characterization and cultivar differentiation

Free zone capillary electrophoresis conditions have been improved to allow rapid (2-8 min) separations of grain proteins from several cereals (wheat, oats, rice, barley, and rye) with high resolution and reproducibility. This new method utilized the isoelectric compound iminodiacetic acid (IDA) in conjunction with 20% acetonitrile and 0.05% hydroxypropylmethylcellulose. Cultivars of all cereals tested could be differentiated in 3 min, including wheat, using either prolamin or glutelin protein patterns. Resolution was similar to or higher than that of separations in other acidic buffers. Migration time repeatability was excellent with run-to-run variability <1% RSD, day-to-day <1.4% RSD, and capillary-to-capillary <3.3% RSD. Because larger inner diameter capillaries (50 microm) could be used with this buffer, sensitivity was improved and capillary rinse times could be reduced when compared to smaller capillaries (25 microm i.d.). This also served to reduce total separation time so that the majority of cereal storage protein from several types of cereals could be analyzed with total analysis times of 2-8 min with extremely high resolution and repeatability. This method would allow unattended, high-throughput ( approximately 180-400 samples/24 h) analysis of cereal proteins without the generation of much organic solvent waste as well as automated data analysis and storage.     

Fast and sensitive screening method for detection of trichothecenes in maize by using protein synthesis inhibition in cultured fibroblasts

A fast and sensitive bioassay with hamster (BHK-21 C13) fibroblasts for the detection of toxic trichothecenes in maize is described. Cells are exposed to pure toxins or crude maize extracts for 30 min. The mixture is then incubated with [1-14C]-leucine for an additional 60 min and the radioactivity incorporated into the protein of the washed cells is determined. The sensitivity of the assay was in the range 1-10 ng/mL (or 50 ppb in maize) for T-2, HT-2, and diacetoxyscirpenol. At least 1000-fold higher concentrations of non-trichothecene mycotoxins and plant toxins were necessary to cause an inhibition of protein synthesis in the cells. Of 24 maize samples tested, 14 gave a positive response in this assay and the presence of trichothecenes could be confirmed chemically in 11 samples. Therefore, the described bioassay is proposed as a useful screening method for cytotoxic trichothecenes in maize.     

Electrofocusing: A new method for characterization of soil humic matter

Electrofocusing in polyacrylamide gel was carried out on humic substances extracted by 0.1 n NaOH, 0.1m Na₄P₂O₇, and by the method of Burns, El Sayed and McLaren (1972) from the upper and lower organic horizons of an alpine podsol. The electrophoretic patterns were characteristic of both humus origin and extractions procedure. The best resolution of the isoelectric bands for the humus were obtained by the Burns-McLaren procedure. The ionic component does not have much influence on the distribution of humus constituents within the electrophoretic pattern, but the presence of phosphate appears to be essential to obtain good separations.     

The relative nitrogen utilization method for evaluating protein quality.

A single-dose rat assay for protein quality called relative nitrogen utilization (RNU) is described. The method includes a factor for the protein utilized for maintenance. The protein quality of the test protein is expressed as a per cent of the value for lactalbumin, the reference protein. For good quality proteins RNU gives results that are similar to those obtained by net protein ratio and relative protein value; for poor quality proteins RNU results fall between values by the other 2 methods. The protein efficiency ratio (PER) gives much lower values for poor quality proteins than any of the other 3 aforementioned methods and is influenced more by both level of protein and lipid in the diet. RNU is a more precise assay then PER as judged by the coefficient of variation.     

Rheological properties and characterization of polymerized whey protein isolates.

Whey protein polymers were formed by heating whey protein isolate solutions at 80 degrees C. Flow behaviors of whey protein polymers produced from different protein concentrations and heating times were comparable to various flow behaviors of hydrocolloids. Polymer formation was found to be a two-phase process. The initial protein concentration was a significant factor that determines the size and/or shape of the primary polymer in the first phase as shown by intrinsic viscosity. Heating time was a factor in determining the aggregation in the second phase as shown by apparent viscosity. Intrinsic viscosity of whey protein polymers was as high as 141.7 +/- 7.30 mL/g, compared to 5.04 +/- 0.20 mL/g for native whey proteins. The intrinsic viscosity and gel electrophoresis data suggested that disulfide bonds played an important role in whey polymer formation.     

Simple and rapid method for the differentiation of Lens culinaris Medik. from false lentil species

The practice of using both common vetch (Vicia sativa L.) and single-flower vetch (Vicia articulata Hornem.) seeds as food or feed is encouraged by the very high resemblance of their seeds with those of small-seeded lentil cultivars. Among the Vicieae, antinutritional and toxic factors are particularly important, because many species, containing high levels of these compounds, are not safe. A simple and fast capillary electrophoresis (CE) method was proposed for the differentiation of lentil cultivars from false lentil species (i.e., single-flour vetch and common vetch). Proteins were extracted from defatted milled seeds with an alcoholic/saline solution. Extracts were separated in an uncoated fused-silica capillary with iminodiacetic acid (IDA) isolectric buffer containing 0.05% hydroxypropylmethylcellulose (HPMC) and 20% acetonitrile. The presented method is useful also for the detection of contamination of whole or split seeds of lentil by vetch species. With respect to alternative techniques, such as DNA-based markers or thin-layer chromatography (TLC), CE has the advantages of being less expensive, faster, and fully automated.     

Rapid screening method for aflatoxin M1 in milk

A rapid screening method for detecting aflatoxin M1 in milk has been developed, based on minicolumn chromatography and requiring 8-10 min for each test. The minicolumn is packed with dry Florisil (100-200 mesh) on the bottom, anhydrous Na2SO4 as the next layer, topped with neutral alumina (70-200 mesh) to which 8% water (wet basis) has been added. A blue fluorescent band at the Florisil-Na2SO4 interface indicates the presence of aflatoxin M1. The limit of detection is estimated to be about 0.2 microgram/kb. Because several items are disposable, both the time to maintain glassware and the cost per determination are reduced.     

Determination of chlorinated pesticide residues in foods. I. Rapid screening method for chlorinated pesticides in milk.

A rapid analytical method for determining chlorinated pesticide residues in milk was developed. Thirteen pesticides were almost completely extracted. Ten mL samples of fortified milk were extracted 3 times with 20 mL portions of n-hexane as follows: (A) in the absence of water-soluble solvent; in the presence of (B) 1 mL acetonitrile; (C) 3 mL acetonitrile; (D) 5 mL acetonitrile; (E) 5 mL ethanol; (F) 5 mL acetonitrile and 1 mL ethanol. System F produced the highest pesticide recoveries but the lowest fat extraction, thus eliminating the necessity for liquid-liquid partitioning and minimizing Florisil column cleanup. Pesticide recoveries throughout the procedure were 94--103%. It was noticed, however, that the fat in high fat-containing raw milk is more readily extracted than that in commercial milk.     

A novel method for the synthesis of cellulose nanofibril whiskers from banana fibers and characterization

Alkali treatment coupled with high pressure defibrillation and acid treatment have been tried on banana fibers obtained from the pseudo stem of the banana plant Musa sapientum. The structure and morphology of the fibers have been found to be affected on the basis of the concentration of the alkali and acid and also on the pressure applied. Steam explosion in alkaline medium followed by acidic medium is found to be effective in the depolymerization and defibrillation of the fiber to produce banana nanowhiskers. The chemical constituents of raw and steam exploded fibers were analyzed according to the ASTM standards. Structural analysis of steam exploded fibers was carried out by FTIR and XRD. The fiber diameter and percentage crystallinity of the modified fibers were investigated using X-ray diffraction studies. Characterization of the fibers by SFM and TEM supports the evidence for the development of nanofibrils of banana fibers.