Analysis of crops and soils for residues of diethyl 1-(2,4-dichlorophenyl)-2-chlorovinyl phosphate. II.-Results

Crops and soils from field trials in 1963 and 1964 in the U.K. and Germany have been analysed for residues of the insecticide diethyl 1-(2,4-dichlorophenyl)-2-chlorovinyl phosphate (Birlanet, SD 7859). Residues of Birlane in turnips, cabbages, potatoes and white radish were less than 0·05 ppm when harvested 8-29 weeks after soil applications at 4-8 lb/acre. Residues in carrots were generally less than 0·05 ppm but were near 0·1 ppm in some mature carrots harvested from soil 17-26 weeks after application of granules at 8 lb/acre. The initial half-life of Birlane in soils varied from 2 weeks to more than 23 weeks depending on the soil type, the formulation, and the dosage level. Residues of the trichloroacetophenone that would result from the hydrolysis of Birlane could not be detected in crops and the limit of detectability was 0·02 ppm. Up to 0·1 ppm of the ketone could be detected in peat 15 weeks after application of Birlane at 8 lb/acre.     

Analysis of crops and soils for residues of the soil insecticides aldrin and "Telodrin"

Aldrin (2 lb/acre) and ‘Telodrin’ (0.5 lb/acre) were applied as emulsifiable concentrates to plots once in 1961 or in three annual applications 1961-3. Residues taken up into cabbage, carrots, celery, onions, potatoes and sugar-beet, and those remaining in the soil have been determined by electron-capture gas–liquid chromatography. The insecticide residue level in all crops was less than 0·1 ppm. Residues were found in crops grown in loam soils but not in peat, and only in the root crops (carrots, potatoes and sugar-beet). Crop residues did not increase markedly with annual re-treatment, but levels greater than 0·01 ppm continued to occur in carrots grown in loam soils in later seasons when treatment was not repeated. Residues were lost rapidly from soil immediately following application, dropping to about 15% of the initial values after a year, but loss thereafter was at a much slower rate.     

Analysis of crops and soils for residues of 2,6-dichlorobenzonitrile (dichlobenil) and 2,6-dichlorothiobenzamide (chlorthiamid). I.—Development of method

Methods are described for the analysis of residues of two new herbicides, 2,6-dichlorobenzonitrile and 2,6-dichlorothiobenzamide, in crop, soil and water samples. The methods are suitable for the analysis of samples containing the benzonitrile alone or the benzonitrile in the presence of the thiobenzamide. Gas/liquid chromatography (GLC) using electron-capture detection can be used to dctermine 2,6-dichlorobenzonitrile at 0·005 μg/ml in soil, crop and water extracts. The thiobenzamide cannot be analysed by GLC directly but is oxidised quantitatively to 2,6-dichlorobenzonitrile by treatment with alkaline permanganate prior to GLC analysis. The benzonitrile and the thiobenzamide can be separated before the final analysis by partition between hexane and water. Adequate extraction procedures are described as well as clean-up procedures using oxidation, steam distillation, thin-layer chromatography or column chromatography. Average recoveries of 2,6-dichlorobenzonitrile are between 85 and 100 % and of 2,6-dichlorothiobenzamide between 73 and 100% depending on the sample and the extraction procedure.     

Analysis of crops and soils for residues of 2,6=dichlorobenzonitrile (dichlobenil) and 2,6=dichlorothiobenzamide (chlorthiamid). II.—Results

Crops and soils from a large number of field trials have been analysed for residues of 2,6dichlorothiobenzamide (chlorthiamid) and for residues of 2,6-dichlorobenzonitrile (dichlobenil). The thiobenzamide is converted to the benzonitrile after application to the soil and only a small percentage of the material applied initially remains unchanged after 4 weeks. However, both the benzonitrile and the thiobenzamide are of similar low mammalian toxicity. The initial half-life of the ‘total nitrile’ residues (the thiobenzarnide + the benzonitrile) is, on average, near 4 weeks but varies from 1 to 12 weeks depending on the locality, soil type, climate, dosage level and formulation. The penetration of the herbicide into soils of different types is considered and it is shown that in sand, loam, and clay, residues in the 4–12 in. layer are less than 10% of the residue at the same time in the 0–4 in. layer. Residues of the thiobenzamide and the benzonitrile could not be detected in a very wide range of crops (other than rice) harvested at 2–6 months after soil applications of the thiobenzamide at 1–16 lb/acre. In rice grains, where the plants can be in intimate contact with the herbicide, the ‘total nitrile’ residues did not exceed 0·05 ppm.     

Residues of supona in sheep

Supona is a new organophosphorus compound which is highly effective for the control of maggot fly strike in sheep. Tissue samples taken from sheep which had been treated with various concentrations of Supona have been analysed for residues of Supona and the lipophilic metabolite trichloroacetophenone. As a result of treatment of sheep with concentrations of Supona at and above the intended field usage rate the following conclusions were drawn:

• 1 The Supona residues in the fat depots of sheep killed 7 days after dipping in double-strength dip wash never exceeded 0·1 ppm Supona and were in the main substantially below this level.
• 2 The residues in the major organs of these sheep were below the minimum detectable amount (0·003 ppm).
• 3 The residues of trichloroacetophenone in the body fats and organs of sheep treated with Supona were below the minimum detectable amount (0·001 ppm).
• 4 The residues of Supona in the body fat of sheep dipped in normal strength Supona dipwash and killed 3 days after treatment were less than 0·05 ppm.
• 5 The residues of Supona were considerably lower and much less persistent than those occurring with dieldrin when used at comparable concentrations.

     

DETERMINATION OF PIRIMIPHOS-METHYL IN PASTA BY GAS CHROMATOGRAPHY/CHEMICAL IONIZATION MASS SPECTROMETRY

A method for the determination of pirimiphos-methyl residues in pasta has been developed. The pesticide was extracted from pasta using the Luke procedure modified for low moisture, nonfatty food products. The extracts were analyzed by capillary column gas chromatography using an ion trap mass spectrometer in the chemical ionization mode as the detector. Quantification was performed using fluorene as the internal standard. The limit of detection was 0.005 ppm. Recoveries from spaghetti were 83.0% at the 0.100 ppm level and 93.3% at the 0.010 ppm level. Of 48 spaghetti samples analyzed, 38 contained detectable residues between trace (>0.005 ppm) and 0.180 ppm. Electron ionization (EI) was used to confirm residues as low as 0.016 ppm in more concentrated extracts.     

ESTIMATION OF α-, β- AND ISO-α-ACIDS IN HOPS,HOP PRODUCTS AND BEER USING HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

Methods are described in which high performance liquid chromatography (HPLC) is used to estimate α-, β- and iso-α-acids in hops, hop products and beer. The chromatography relies on an isocratic elution of components from a polythene ‘cartridge’ column, and the method is calibrated with the pure substances as primary standards. Using such a column over 1000 analyses have been carried out without any significant loss in resolution or precision. The procedures are sufficiently rapid for use in commercial transactions and for quality control purposes. For hops and hop extracts coefficients of variation (%) of 2·5 and 0·8 were obtained respectively for α-acids. Values of 0·9 and 0·3 were obtained for iso-α-acids in isomerised extracts and beers respectively. For some isomerised extracts it has been observed that peaks in addition to those given by the iso-α-acids are present on the chromatogram. The current method recommended by the EBC over estimates the iso-α-acid content since these other constituents are included in the analysis.     

Responses of Cereals to Residual Fertiliser Nitrogen Applied to the Preceding Potato Crop

The effects of N fertiliser and poultry manure, applied to potato crops, on soil mineral N (SMN) after harvest and on the grain N offtake (N_off) and yield of subsequent unfertilised cereal crops, were measured at six sites in England during 1989–1994. At three sites of medium textured soil N_off increased by between 0 and 49 kg ha^-1 and grain yield by between 0 and 2·1 t ha^-1, with increasing potato fertiliser N (PFN). The increases were greatest at applications of fertiliser N in excess of the optimum requirement for potatoes. No responses were found on two sandy and one shallow soil. Poultry manure applied in autumn or spring before the potatoes were planted increased N_off by between 0 and 52 kg ha^-1 and yield by between 0 and 2·1 t ha^-1 at one site on medium textured soil but not on one of the two sandy soils. These results suggest that, at the rates of fertiliser N currently recommended for potatoes, the N requirement of subsequent cereal crops may be reduced by between 20 and 40 kg ha^-1 on retentive soils but not on sandy and shallow soils. These reductions are less than currently recommended. However, the results also suggest that adjusting cereal fertiliser N according only to previous crop is unsatisfactory. The range of fertiliser N applied to potato crops in commercial practice is sufficiently great to significantly affect N_off, yield and hence the fertiliser N requirement of the subsequent cereal crop. © 1997 SCI.     

Cholesterol Oxides in Swedish Foods and Food Ingredients: Fresh Eggs and Dehydrated Egg Products

Cholesterol oxides were enriched from lipid extracts of fresh and dehydrated egg yolk products by chromatography on Lipidex and TEAP-Lipidex. Appropriate fractions from TEAP-Lipidex were analyzed by capillary GLC as their TMS derivatives. At the detection limit level, ca 0.2 ppm in total lipids, no cholesterol oxides could be detected in fresh egg yolk. Similarly, spray dried egg yolk powder contained only traces of cholesterol oxides when fresh or stored for 2 months at 4°C. Prolonged storage gave lipid extracts which contained variable levels (0.2–12 ppm) of known oxidation products, viz., cholest-5-ene-3β, 7α-diol, cholest-5-ene-3β, 7β-diol, 5,6α-epoxy-5α-cholestan-3β-ol, 5,6 β-epoxy-5 β-cholestan-3β-01, cholest-5-ene-3β, 20α-diol, 3 β-hydroxycholest-5-en-7-one. Traces or small quantifiable amounts of cholest ?5-ene-3β, 25-diol and 5α-cholestane-3β, 5, 6β-triol were observed in some samples at longer storage periods.     

In vivo and in vitro digestible fractions in forage

Faeces and the residues from the in vitro digestion of 13 forages were sequentially extracted with acid-pepsin, ethyl alcohol, hot water and diethyl ether and the quantity of the extracts was adjusted to a protein-free basis and expressed per 100 g of original forage organic matter. Undigested material inin vivo and in vitro experiments were respectively, 3·37 and 1·88 g (±0·12) for ethyl alcohol extracts, 1·13 and 1·10 g (±0·05) for hot water extracts, 0·15 and 0·12 g(±0·02) for diethyl ether extracts and 1·44 (±0·22) and 0g for 0·1 N -HCI extracts. The difference between values for in vivo and in vitro experiments was considered to represent endogenous material present in faeces.     

Ascorbyl Palmitate Efficacy in Enhancing the Accelerated Storage Stability of Canola Oil

The effect of various levels of ascorbyl palmitate (AP) and of butylated hydroxyanisole/toluene (BHA/BHT) on the accelerated storage stability of canola oils was determined by sensory, gas liquid chromatographic (GLC) and chemical evaluations. In Schaal oven tests (65°C, 0–16 days), chemical, GLC and trained sensory panel data indicated that 200 ppm AP retarded autoxidation in stored canola oils. Monoglyceride citrate (MGC) addition to oils containing 200 ppm AP did not enhance oil stability. Fluorescent light tests (7500 lux, 24°C, 0–24 hr) showed that 200 ppm AP, with or without MGC, had a limited effect in protecting canola oil from photooxidation. BHA/ BHT, at 100 ppm each, with MGC, did not improve canola oil stability.     

Determination of residues of 3-cyclohexyl-5,6-trimethyleneuracil

A method is described for determining residues of an experimental herbicide, based on Lenacil (3-cyclo-hexyl-5,6-trimethyleneuracil) in soil and sugar beets. The procedure is based on the gas chromatographic measurement of Lenacil after extraction from the substrate with an alkaline solution and subsequently partitioned into an organic solvent. Intermediate cleanup steps are required. The sensitivity of the method is about 0·04 ppm based on a 25-g sample, with an average recovery of better than 80%.     

Availability of Cu,Zn and Mn in soils: I.—Influence of soil pH,organic matter,and extractable phosphorus

Samples from Ap horizons of 36 cultivated Wisconsin fields were tested for concurrent availability of Cu, Zn and Mn. The effects of soil pH, organic matter, and available P were evaluated by using four chemical extract ants. Oats were used as the test crop and were grown using a self-watering pot-culture technique in a plant-growth room. The divergent soils had the following averages: pH, 6–4; organic matter, 2–6%; available P, 37 ppm; total Cu, 20 ppm; total Zn, 35 ppm; and total Mn, 631 ppm. Concentrations of the micronutrient elements in plants and soils were determined by atomic absorption spectrophotometer. NPK fertilisation resulted in greater plant uptake of Cu, Zn and Mn. Significant interactions between the soil properties and the different chemical fractions influenced the plant uptake of each micro-element; interactions between Cu, Zn and Mn in the same chemical fraction also influenced their individual uptake. Copper uptake was best predicted by inclusion particularly of soil pH, or the same chemical fractions of Zn and Mn in the regression equation; Zn uptake by inclusion of soil organic matter and available P, Mn uptake, or the chemical fractions of Cu and Mn; and Mn uptake by inclusion of available P, Cu chemical fraction, or Zn uptake in the equation. The extractants N ammonium acetate (pH 7) 10 · 01 M EDTA and 0·1 N -HCI show promise in soil tests for the simultaneous availability of Cu, Zn and Mn.     

Preservation of cultures of vegetative cells for use in antibiotic residue assays

Freeze preservation of suspensions of Micrococcus luteus CECT 4070 (ATCC 9341a) and Staphlococcus epidermidis CECT 231 (ATCC 12228) used for antibiotic residue determination was evaluated. Stability of cell suspensions was monitored during a 6 month period. The best homogeneity in the number of cells from different microtubes was obtained when glycerol was used as cryoprotectant for M. luteus and when methylcellulose was used for S. epidermidis. No significant differences (P < 0·05) were found between preservation at -20° and -80°C.     

Non-Volatile Organic Acids,pH and Titratable Acidity Changes in Pineapple Fruit Slices During Frozen Storage

Effects of freezing and frozen storage on pH, titratable acidity and non-volatile organic acids of two pineapple fruit cultivars, Smooth Cayenne and Red Spanish, were studied. Pineapple fruit was frozen as slices in a cold room at −18°C and stored at this temperature for a 12 month period. A negative correlation was found between pH and titratable acidity in the two cultivars throughout frozen storage ( r =-0·67 for Smooth Cayenne and r =-0·71 for Red Spanish). Non-volatile organic acids were determined by high performance liquid chromatography. The major components were citric and L-malic acids. A high correlation was found between these two acids during frozen storage ( r =0·75 in Smooth Cayenne and r =0·78 in Red Spanish). There were significant differences ( P⩽ 0·01) in pH and titratable acidity between the two studied varieties after a year of frozen storage. Significant differences ( P⩽ 0·05) were found in pH values during frozen storage in cv Smooth Cayenne and in citric and L-malic acids in cv Red Spanish. Freezing preservation of pineapple fruit slices led to minimal chemical changes after a year of frozen storage.     

Antioxidant efficacy of phytochemical extracts from defatted rice bran in the bulk oil system

The antioxidant compounds oryzanols, tocols and ferulic acid were identified in the methanolic extracts of defatted rice bran (DRB) by high pressure liquid chromatography (HPLC). The crude methanolic extract (CME) was partially purified by re-extraction with acetone to give an acetone extract (AE). For further purification of the acetone extract, sequential solvent extraction was employed yielding a lipophilic phase (AE-LP) with hexane and a polar phase (AE-PP) with acetone. The antioxidant potential of the DRB extracts and their phytochemical constituents in bulk oils were evaluated using the Schall oven test (SOT) and differential scanning calorimetry (DSC). The extracts were effective in inhibiting lipid oxidation as assessed by peroxide value, diene value and p-anisidine value. The activity of the extracts with respect to the inhibition of primary oxidation products followed the order AE-PP > AE-LP = AE > CME with the activity of AE-PP being equivalent to that of butylated hydroxytoluene (BHT) at a 200 ppm level. However, tertiarybutylhydroquinone (TBHQ) was most active as compared to extracts and pure compounds with AE-PP showing about 45% of the activity of TBHQ at 200 ppm level. Defatted rice bran extracts proved to be effective even at the high temperature employed in DSC. The antioxidant efficacy of AE-PP was close to that of TBHQ and far greater than that of BHT at a 200 ppm level as evident from DSC results. The increase in activity with purification might be due to the enhanced levels of antioxidants in purified extracts compared to CME.     

Effects of α-, γ-, and δ-Tocopherols on Oxidative Stability of Soybean Oil

The effectts of 0, 100, 250, 500 and 1000 ppm of α-, γ-, or δ-tocopherol on oxidative stability of purified soybean oil in the dark at 55°C were studied. We measured peroxide value and headspace oxygen consumption in the samples. Purified soybean oil was prepared by liquid column chromatography. Tocopherols acted as antioxidants or prooxidants depending on their concentration. Optimum concentrations of α -, γ -, and δ– tocopherols to increase oxidative stability was 100, 250 and 500 ppm, respectively. The tocopherols had significant prooxidant effect (P < 0.05) at higher concentrations above this.     

The lead content of pasture herbage

On soils in north-east Scotland derived from quite diverse parent materials, including granitic gneiss, sandstone, slate and mixed acidic and basic igneous rocks, the normal lead content of rotational mixed pasture herbage during the period of active growth is between 0·3 and 1·5 ppm in the dry matter. In autumn, at a date possibly determined by the cessation of active growth and therefore by climatic conditions, the lead content of the above-ground portion of the plant begins to rise, reaching 10 pprn in late autumn, and may reach 30-40 ppm in late winter or early spring before growth recommences. At this stage, young shoots with a low lead content appear and the senescent foliage withers away. The increase in lead content of the above-ground portion when the plant is dormant may indicate movement from the root rather than active uptake of lead from the soil. The possibility of surface contamination by petrolengine exhaust fumes or other industrial materials has been ruled out, and soil contamination of the herbage cannot account for the effect observed. The level of lead in pasture herbage in late winter appears sufficiently high to justify consideration of possible effects on the health of the animal consuming appreciable quantities during this period.     

Bioactive compounds extracted by liquid and supercritical carbon dioxide from citrus peels

This work investigated the extraction of bioactive compounds from citrus peels, an agri-food waste. Carbon dioxide (CO₂), an eco-friendly solvent, was used under liquid and supercritical conditions to perform the extractions from orange, tangerine and lemon peels. The possibility of using ethanol as a cosolvent at small percentages up to 20% was also studied. The extraction yield, total polyphenolic content, individual polyphenolic profile, antiradical activity and volatile organic compounds of the extracts were evaluated. The highest yields were obtained when 20% ethanol was used as a cosolvent in both liquid (at 20 MPa and 20 °C) and supercritical (at 30 MPa and 60 °C) CO₂ extraction. In addition, the extracts obtained with liquid CO₂ + 20% ethanol showed the highest content of naringin (35.26, 44.05 and 19.86 mg g^-1 in orange, tangerine and lemon peel extracts, respectively) and terpenes, in particular limonene. This type of extract also showed the highest antiradical activity (31.78–59.51 µmolTE g^-1) as measured by both ABTS·+ and DPPH·. These findings show that the extraction with a liquid CO₂ and ethanol mixture could be a valid alternative to traditional solvent extraction using 80% less organic solvent and producing extracts with high antiradical capacity and rich in volatile organic compounds.     

Analysis of wheat storage proteins by exhaustive sequential extraction followed by RP-HPLC and nitrogen determination

Wheat storage proteins are responsible for the viscoelastic properties of dough. Their effect on dough rheology depends on the glutenin components and the proportion of gliadins, high and low molecular weight glutenin subunits (HMW-GS, LMW-GS). A prediction of dough behaviour is possible when the concentration of each prolamin group is known. A method of sequential extraction and quantification of wheat flour proteins was developed. Reversed-phase high-performance liquid chromatography (RP-HPLC) was used to quantify gliadins and HMW-GS and LMW-GS. Non-prolamin proteins and lipids were extracted with phosphate buffer and phosphate buffer containing Triton X114 respectively and 70% (v/v) ethanol was used to extract gliadins. Several solvent systems were tested to exhaustively extract glutenins and a buffer containing 0·05 M tetraborate pH 8·5, 2% (v/v) 2-mercaptoethanol, 1 g litre⁻¹ glycine, and 8 M urea was selected. It facilitated the most complete extraction and was compatible with RP-HPLC analysis of extracts. The quantities of extracted prolamins were estimated from RP-HPLC profiles using peak area determination. The concentration of different classes of prolamins obtained by RP-HPLC was compared with their determination by nitrogen (N) content. The average yield of extractions performed on 45 cultivars was 0·99 (coefficient of variation (CV)=7·6%) for gliadins and 0·89 (CV=9·1%) for glutenins. Quantifications of proteins by N determination and RP-HPLC were strongly correlated: regression coefficients were 0·86 for total prolamins and gliadins, and 0·71 for glutenins with the gradient of regression of approximately 1. Therefore, RP-HPLC could be used to quantify prolamin groups without using N determination. © 1998 SCI.