Development of sensitive immunoassays for the detection of the glucuronide conjugate of 3-phenoxybenzyl alcohol, a putative human urinary biomarker for pyrethroid exposure

Pyrethroids are widely used in agriculture as insecticides. This study describes a sensitive enzyme-linked immunosorbent assay for the detection of the glucuronide conjugate of 3-phenoxybenzyl alcohol, a putative pyrethroid metabolite that may be used as a biomarker of exposure to pyrethroids. Four antisera were elicited against two different immunizing haptens. Antisera were characterized in combination with several coating haptens. The lowest IC50 value (0.5 ng/mL) was obtained with antiserum 1891 and 3-phenoxybenzoic acid-BSA conjugate as the coating antigen. Antiserum 1891 was highly selective for the target compound with an overall cross-reactivity of <0.3% to structurally related compounds. The assay sensitivity was negligibly affected by pH 4-9. A 5-fold improvement in IC50 was observed using a 10-fold concentrated phosphate-fuffered saline as the assay buffer. Compared to assays conducted in normal phosphate-fuffered saline, the maximal absorbance was almost identical. A good correlation (r 2 = 0.99 and 0.97 for urine samples A and B, respectively) was observed between spiked levels and the levels detected by the immunoassay.     

基于声振响应法的香梨硬度无损检测

为了探索香梨硬度无损检测的方法,该研究搭建了由压电梁式传感器进行信号激励和感测的检测装置,分析了装置信号检测的稳定性,提取了香梨共振频率和声速并进行香梨硬度评估,然后将这两响应参数的评估硬度与香梨硬度的M-T穿刺法(Magness-Taylor)测量结果进行线性回归分析,以构建香梨硬度的检测模型。结果表明,检测装置的共振频率和声速信号检测稳定可靠,并且在香梨赤道部不同位置激励感测均无显著差异(P0.05);基于共振频率法和声速法的硬度评估指标可以构建3种香梨硬度检测模型,相关系数分别为0.841、0.877和0.938,其中由共振频率检测硬度和声速检测硬度联合构建的检测模型硬度检测敏感度为67.30%,最接近M-T穿刺法检测敏感度,该模型对香梨正常果和粗皮果的检测准确率较高,达到86.7%。研究结果可为声振法无损检测香梨硬度提供参考。     

Determination of cytotoxic trichothecenes in corn by cell culture toxicity assay

The great sensitivity of some cell species to toxins has been adapted to a direct biological determination of trichothecene contamination of food and feeds. The murine spleen lymphocyte stimulated by PHA (Phaseolus vulgaris phytohaemagglutinin) appeared to be the most convenient cells because of their particular sensitivity to cytotoxic trichothecenes and the opportunity to translate this cytotoxicity to immunosuppressive hazard, one of the most important concerns for trichothecenes. In this paper, the use of cell cultures was adapted for a survey of corn. The toxins were extracted by aqueous methanol, and the extract was defatted with hexane and purified on a silica gel/Florisil column. This extract was then used for a gas chromatographic (GC) determination and the biological test. The growth of cells was measured by the incorporation of tritiated thymidine (3H Tdr), and the inhibition was expressed by the IC50: concentration of corn extract inhibiting by half the 3H Tdr incorporation. We have tested pure toxins, control corn, corn spiked with T-2 toxin, corn experimentally inoculated with toxigenic Fusarium strains, and naturally contaminated corn. A good correlation exists between IC50 and the T-2 toxin concentration as determined by GC analysis. The response is not affected by the presence of zearalenone or by small amounts of deoxynivalenol. A quantitative evaluation of cytotoxic trichothecenes in corn is valuable in the range of 100 ppb to 10 ppm, expressed as T-2 toxin equivalents. The result is obtained in 48 h.     

T-2 toxin, a trichothecene mycotoxin: review of toxicity, metabolism, and analytical methods

This review focuses on the toxicity and metabolism of T-2 toxin and analytical methods used for the determination of T-2 toxin. Among the naturally occurring trichothecenes in food and feed, T-2 toxin is a cytotoxic fungal secondary metabolite produced by various species of Fusarium. Following ingestion, T-2 toxin causes acute and chronic toxicity and induces apoptosis in the immune system and fetal tissues. T-2 toxin is usually metabolized and eliminated after ingestion, yielding more than 20 metabolites. Consequently, there is a possibility of human consumption of animal products contaminated with T-2 toxin and its metabolites. Several methods for the determination of T-2 toxin based on traditional chromatographic, immunoassay, or mass spectroscopy techniques are described. This review will contribute to a better understanding of T-2 toxin exposure in animals and humans and T-2 toxin metabolism, toxicity, and analytical methods, which may be useful in risk assessment and control of T-2 toxin exposure.     

Detection of T-2 toxin in different cereals by flow-through enzyme immunoassay with a simultaneous internal reference

In most previously described membrane-based immunoassays a separate negative control assay is always carried out to evaluate the performance of the assay. To overcome this problem, a membrane-based flow-through enzyme immunoassay with an internal control has been developed for the detection of T-2 toxin in cereals (patent pending). An Immunodyne ABC membrane was coated with 2 microL of goat anti-horseradish peroxidase (HRP) (internal control spot) (1:1000) and 2 microL of rabbit anti-mouse (test spot) (undiluted) immunoglobulins, and the free binding sites were blocked. In addition to the antibody-coated Immunodyne ABC membrane, the assay also comprises a plastic snap-fit device, absorbent cotton wool, mouse anti-T-2 monoclonal antibodies (Mab), and T-2-HRP conjugate. The color intensity (Delta) of the internal control and that of the negative sample showed no difference (P > 0.05), whereas there was a significant difference between the internal control and positive samples (P < 0.05). The minimum detectable limit that could be visually detected with confidence was 50 ng of T-2 per gram of cereal sample.     

Development of an indirect competitive ELISA for the detection of furazolidone marker residue in animal edible tissues

Due to its carcinogenicity and mutagenicity, furazolidone has been prohibited completely from being used in food animal production in the world since 1995. To monitor the illegal abuse of furazolidone, a polyclonal antibody-based indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) was developed for the determination of tissue-bound furazolidone metabolite 3-amino-2-oxazolidone (AOZ). The highly specific antibody was targeted for PAOZ, the benzaldehyde derivative of AOZ. The 50% inhibition values (IC 50) of 0.91 microg/L for AOZ was achieved with the most sensitive antibody Ab-B1 by altering ELISA conditions. In the ELISA, sample extraction and cleanup were performed by an is MAX cartridge following combined hydrolysis of the tissue-bound AOZ and derivatization of the homogenized tissues with benzaldehyde. The limits of detection (LOD) calculated from the analysis of 20 known negative tissue samples (swine liver, swine muscle, chicken liver, chicken muscle,and fish muscle) were 0.3-0.4 microg/kg (mean+3 SD). Recoveries of AOZ fortified at the levels of 0.4, 1, and 5 microg/kg ranged from 55.8 to 96.6% in the tissues. The coefficients of variation were less than 20% over the range of AOZ concentrations studied. The linear detection range was between 0.1 and 25.6 microg/L. Validation of the ELISA method with swine muscle and liver from furazolidone-treated pigs was carried out using HPLC, resulting in a similar correlation in swine muscle (r=0.99) and in swine liver (r=0.98). The results suggest that this ELISA is a specific, accurate, and sensitive method of detecting AOZ residues in animal edible tissues.     

Availability of Organic and Inorganic Phosphorus Fractions to Wheat in Toposequences of Calcareous Soils

Abstract

Information on the availability of different soil phosphorus (P) forms is useful for crop production. Phosphorus contents of 12 Iranian calcareous soils from upper‐, mid‐, and lower‐slope positions of two arid and two semiarid toposequences were fractionated to various organic and inorganic pools, and correlations of the P fractions with wheat responses were investigated. Among the inorganic P (IP) fractions, apatite type (Ca₁₀‐P) and dicalcium phosphate equivalents (Ca₂‐P) possessed the highest and the lowest amounts of P reserve in the soils, respectively. On average, about 20% of the total P was found in organic form (OP), of which 32% was labile (LOP), 51% was moderately labile (MLOP), and 17% was nonlabile (NLOP). The amounts of the soil P fractions were considerably influenced by the positions of the soils on the landscapes. The maximum contents of soil IP, Ca₂‐P, Fe‐P (iron‐bound P), and Ca₁₀‐P were observed in the lower‐slope positions. The amount of soil available [0.5 M sodium bicarbonate (NaHCO₃) extractable] P was significantly correlated with Ca₂P (r=0.895), Fe‐P (r=0.760), and Occl‐P (iron‐occluded P) (r=0.897). Direct correlation studies, however, showed that wheat shoot dry‐matter yield (DMY) was significantly affected by the amounts of Ca₂‐P, Fe‐P, OP, LOP, and MLOP fractions both at early (4 weeks) and late (10 weeks) stages of growth. All organic and inorganic P fractions, except Al‐P (aluminum‐bound P), Ca₈‐P (octacalcium phosphate equivalents), and NLOP, also showed significant relations to the amount and/or concentration of P in wheat tissues at 4 and 10 weeks after sowing. Among the measured soil properties, the amount of organic carbon was the most affecting factor on the size of the P fractions.     

Simultaneous analysis of T-2 toxin and HT-2 toxin by an indirect enzyme-linked immunosorbent assay

An indirect enzyme-linked immunosorbent assay (ELISA) for the detection of HT-2 toxin in the presence or absence of T-2 toxin is described. In the indirect ELISA, the relative cross-reactivities of antibodies against T-2 toxin (anti-T-2) with T-2 toxin and HT-2 toxin were 1 and 0.1, whereas anti-HT-2 cross-reactivities with T-2 toxin and HT-2 toxin were 0.33 and 1, respectively. Using such relationships, a formula was established that could be used to calculate the individual toxin concentration in a mixed sample after experimentally analyzing for T-2 and HT-2 toxins in the 2 indirect ELISAs. This method was tested by analyzing urine samples spiked with HT-2 toxin alone and samples spiked with both T-2 toxin and HT-2 toxin. A cleanup protocol for treatment of urine samples before ELISA was also established. The overall analytical recovery of HT-2 toxin when it was added at concentrations of 0.1-10 parts per billion (ppb) to the urine samples was ca 89%. When both T-2 and HT-2 toxins were added to the urine samples at equal concentrations of 0.5 to 5.0 ppb, their recoveries were 112 and 109%, respectively.     

Metabolite profiling based on lipophilic compounds for quality assessment of perilla (Perilla frutescens) cultivars

Lipophilic compounds from Korean perilla ( Perilla frutescens ) seeds were characterized to determine the diversity among their phytochemicals and to analyze relationships between their contents. Twenty-four metabolites consisting of policosanol, phytosterol, tocopherol, and fatty acids were identified. The metabolite profiles were subjected to data mining processes, including principal component analysis (PCA), partial least-squares discriminate analysis (PLS-DA), and Pearson's correlation analysis. PLS-DA could distinguish between all cultivars except between Daesil and Daeyeup cultivars. Linolenic acid contents were positively correlated with β-sitosterol (r = 0.8367, P < 0.0001) and γ-tocopherol contents (r = 0. 7201, P < 0.001) among all perilla grains. The Daesil and Daeyeup cultivars appear to be good candidates for future breeding programs because they have simultaneously high linolenic acid, phytosterol, and tocopherol levels. These results demonstrate the use of metabolite profiling as a tool for assessing the quality of food.     

Enzyme-linked immunosorbent assay for T-2 toxin metabolites in urine

A direct competitive enzyme-linked immunosorbent assay (ELISA) for determination of total T-2 toxin metabolites in urine was developed. The assay involves coating anti-3-acetyl-neosolaniol-hemisuccinate-bovine serum albumin conjugate (anti-3-Ac-NEOS-HS-BSA) antibody to the ELISA plate and using 3-Ac-NEOS-HS-peroxidase as the enzyme marker. Competitive ELISA revealed that the antibody had good cross-reactivity with acetyldiacetoxyscirpenol (Ac-DAS), T-2 tetraol tetraacetate, 3'-OH-Ac-T-2, 3-Ac-NEOS, and 3,4,15-triacetyl-12,13-epoxytrichothec-9-en-8-one (Ac-T-2-8-one), but less cross-reactivity with Ac-T-2 toxin and T-2 toxin. All metabolites of T-2 toxin in urine were converted to T-2 tetraol tetraacetate (T-2-4ol-4Ac) by acetylation of the sample extract before ELISA. To test the ELISA accuracy, a radioimmunoassay (RIA) was performed simultaneously. The linear portion of the standard curve of this direct ELISA for T-2-4ol-4Ac was 0.2-2.0 ng/mL, which was 10 times more sensitive than RIA. The minimum detection level for T-2-4ol-4Ac was 0.02 ng/mL (0.4 pg/assay) in the absence of urine sample. The overall analytical recoveries for T-2 toxin, HT-2, T-2-4ol, 3'-OH-HT-2, NEOS, and a mixture of these 5 toxins added to the urine samples in the ELISA at concentrations of 0.05 and 0.2 ng/mL were 87 and 94%, respectively.     

Amperometric determination of ascorbic acid in real samples using a disposable screen-printed electrode modified with electrografted o-aminophenol film

Ascorbic acid (AA) is an antioxidant considered to play a crucial role in human health. Therefore, diverse methods for the determination of AA in foods have been developed, most of them time-consuming and requiring costly instrumentation. A simple and sensitive method for the quantification of AA in fresh fruits and vegetables and commercial juices using an amperometric sensor is presented on the basis of disposable screen-printed carbon electrodes (SPEs) modified with an o-aminophenol (o-AP) film selective for the detection of AA. The sensor exhibited a linear response for AA from 2-20 microM, with a correlation coefficient r2 = 0.998 and a limit of detection of 0.86 microM. Common possible interferents of the sample matrices were tested, and results showed high selectivity of the o-AP SPEs toward AA. The sensor exhibited an excellent reproducibility (RSD% = 1.98, n = 8) and surface stability. The method was validated by a comparison to a reference method, and excellent correlation is obtained.     

Gas chromatographic screening method for T-2 toxin, diacetoxyscirpenol, deoxynivalenol, and related trichothecenes in feeds

A gas chromatographic method for screening trichothecene mycotoxins in feeds is described. Feed is extracted with acetonitrile-water, and the toxins are purified with charcoal-alumina-Celite, Florisil, and silica mini-columns. Deoxynivalenol (DON), nivalenol (NIV), diacetoxyscirpenol (DAS), T-2 toxin, and their fungal metabolites are hydrolyzed to their corresponding parent alcohols (DON, NIV, scirpentriol, or T-2 tetraol) by alkaline hydrolysis. After derivatization to their pentafluoropropionyl analogs, they are quantitated by capillary gas chromatography with electron capture detection. Identity can be confirmed and sensitivity can be increased by using negative chemical ionization mass spectrometry with no additional sample workup. Recoveries of DAS, DON, and T-2 toxin averaged, respectively, 80, 65, and 85% in corn; 84, 65, and 88% in soybeans; and 70, 57, and 96% in mixed feeds at concentrations ranging from 0.1 to 2.0 ppm. Recoveries of 15-monoacetoxyscirpenol (MAS), HT-2, NIV, and T-2 tetraol were 97, 97, 86, and 56%, respectively, in corn at a concentration of 0.25 ppm: A detection limit of 0.02 ppm in corn, soybeans, and mixed feeds, and 0.05 ppm in silages is estimated.     

Identification and apoptotic potential of T-2 toxin metabolites in human cells

The mycotoxin T-2 toxin, produced by various Fusarium species, is a widespread contaminant of grain and grain products. Knowledge about its toxicity and metabolism in the human body is crucial for any risk assessment as T-2 toxin can be detected in processed and unprocessed food samples. Cell culture studies using cells of human origin represent a potent model system to study the metabolic fate of T-2 toxin as well as the cytotoxicity in vitro. In this study the metabolism of T-2 toxin was analyzed in a cell line derived from human colon carcinoma cells (HT-29) and primary human renal proximal tubule epithelial cells (RPTEC) using high-performance liquid chromatography coupled with Fourier transformation mass spectrometry (HPLC-FTMS). Both cell types metabolized T-2 toxin to a variety of compounds. Furthermore, cell cycle analysis in RPTEC proved the apoptotic effect of T-2 toxin and its metabolites HT-2 toxin and neosolaniol in micromolar concentrations.     

The Occurrence of Type A and B Trichothecenes in Lithuanian Cereals

Samples of winter wheat (n =84), winter rye (46) and barley (29) were collected from the larger family farms and from partnerships in Lithuania just after the 1998 harvest. The number of samples collected from each region was proportional to the amount of grain produced in it. The levels of the Fusarium toxins deoxynivalenol (DON), 3-acetyl-DON, 15-acetyl-DON, nivalenol (NIV), fusarenon-X (4-acetyl-NIV), T-2 toxin, HT-2 toxin, 4,5-diacetoxyscirpenol (DAS), 1,5-monoacetoxyscirpenol (MAS) and scirpentriol in the grain were determined by gas chromatography with mass-selective detection (GC-MS). DON was most often detected in the wheat and rye samples and NIV in the barley samples. The concentrations found were lower than those causing acute or chronic toxic effects in livestock or humans. No fusarenon-X or 15-acetyl-DON was detected, and only small amounts of other trichothecenes were present. Climatic conditions in Lithuania in the summer of 1998 were slightly cooler and wetter than the average for the 1992-1996 but were close to the norm. Because the samples analysed were representative of grain produced for the market in seasons with normal weather, trichothecene contamination of grain from large family farms and partnerships would not be expected to be a problem in most years.     

Use of deuterated internal standards for quantitation of T-2 and HT-2 toxins in human blood by tandem mass spectrometry

Deuterated acetyl derivatives (3-trideutero-acetyl-T-2 and 15-trideutero-HT-2) were prepared for use as internal standards for the quantitation of T-2 and HT-2 in blood by tandem mass spectrometry. The method used was multiple reaction monitoring (MRM), which essentially involves the selection of a parent ion for analysis followed by monitoring of the daughter ions generated by collision activated decomposition. The parent ions chosen for the trifluoroacetate derivative of T-2 and HT-2 were m/z+ 478 and 532, respectively. Both parents yield the same daughter ions, i.e., 180, 138, and 121. HT-2 and T-2 were added to blood extracts in amounts ranging from 1 to 20 ppb. The limit of detection is about 0.5 ppb with an effective detection limit of 1.0 ppb in a range of 1-20 ppb. The recovery is about 90%. This method can be used by veterinarians for purposes of diagnostics. It can be used for urine as well as blood.     

Development of an enzyme-linked immunosorbent assay for the detection of dicamba

A competitive indirect enzyme-linked immunosorbent assay (CI-ELISA) was developed to quantitate the herbicide dicamba (3,6-dichloro-2-methoxybenzoic acid) in water. The CI-ELISA has a detection limit of 2.3 microg L(-1) and a linear working range of 10--10000 microg L(-1) with an IC(50) value of 195 microg L(-1). The dicamba polyclonal antisera did not cross-react with a number of other herbicides tested but did cross-react with a dicamba metabolite, 5-hydroxydicamba, and structurally related chlorobenzoic acids. The assay was used to estimate quantitatively dicamba concentrations in water samples. Water samples were analyzed directly, and no sample preparation was required. To improve detection limits, a C(18) (reversed phase) column concentration step was devised prior to analysis, and the detection limits were increased by at least by 10-fold. After the sample preconcentration, the detection limit, IC(50), and linear working range were 0.23, 19.5, and 5-200 microg L(-1), respectively. The CI-ELISA estimations in water correlated well with those from gas chromatography-mass spectrometry (GC-MS) analysis (r(2) = 0.9991). This assay contributes to reducing laboratory costs associated with the conventional GC-MS residue analysis techniques for the quantitation of dicamba in water.     

ASI法速测土壤指标与植物N吸收的相关性研究

本研究选用ASI法对山西褐土41个、河南潮土73个、辽宁棕壤43个、黑龙江黑土69个土样进行了土壤硝态N(ASI-NO3--N)、铵态N(ASI-NH4+-N)、碱溶有机质(ASI-OM)的测定,同时用常规方法测定了碱解N和有机质。并对测定值进行了相关性分析。同时选取土壤进行盆栽试验以验证ASI法测定值与植物吸N量的相关性。结果表明:四类土壤ASI-NO3--N与碱解N测定结果达到了极显著相关(褐土r=0.89**,潮土r=0.79**,棕壤r=0.90**,r=0.47**),四类土壤ASI-OM与常规方法有机质测定结果均达到了极显著正相关(褐土r=0.92**,潮土r=0.88**,棕壤r=0.93**,黑土r=0.96**),ASI-NH4+-N与碱解N测定结果也均达到了极显著正相关(褐土r=0.76**,潮土r=0.64**,棕壤r=0.97**,黑土r=0.61**)。褐土、棕壤土壤ASI-NO3--N含量与植物吸N量呈极显著正相关(P<0.01),潮土、黑土土壤ASI-NO3--N含量与植物吸N量呈显著正相关(P<0.05)。褐土、棕壤土壤ASI-NH4+-N含量与植物吸N量呈显著正相关(P<0.05),潮土、黑土土壤ASI-NH4+-N含量与植物吸N量相关性不显著(P>0.05)。除褐土土壤ASI-OM含量与植物吸N量呈显著正相关外(P<0.05),潮土、棕壤、黑土土壤ASI-OM含量与植物吸N量相关性不显著(P>0.05)。     

Dissipation of [(14)C]acetochlor herbicide under anaerobic aquatic conditions in flooded soil microcosms

Acetochlor degradation was studied under anaerobic conditions representative of conditions in flooded soils. Soil-water microcosms were prepared with a saturated Drummer clay loam and made anaerobic by either glucose pretreatment or N(2) sparging. Sparged microcosms consisted of sulfate-amended, unamended, and gamma-irradiated microcosms. The microcosms were sampled in triplicate at predetermined time intervals during a 371 day incubation period. Volatile, aqueous, extractable, and bound (unextractable) (14)C residues were quantified with liquid scintillation counting and characterized using high-performance liquid radiochromatography (HPLRC) and soil combustion. SO(4)(2)(-), Fe(II), CH(4), and pH were monitored. Complete anaerobic degradation of [(14)C]acetochlor was observed in all viable treatments. The time observed for 50% acetochlor disappearance (DT(50)) was 10 days for iron-reducing and sulfate-reducing conditions (sulfate-amended), 15 days for iron-reducing conditions (unamended), and 16 days for methanogenic conditions (glucose-pretreated). Acetochlor remained after 371 days in the gamma-irradiated microcosms, and metabolites were observed. [(14)C]Metabolites were detected throughout the study. Formation of one of the metabolites correlated with Fe(II) formation (r(2)(), 0.83). A significant portion of the (14)C activity was eventually incorporated into soil-bound residue (30-50% of applied acetochlor) in all treatments.     

Comparison of phosphorus impregnation and bray 1 soil tests for evaluating plant available phosphorus

Abstract

The relationship between soil test phosphorus and crop response has not been studied for maize (Zea mays L.) in some major benchmark soils of Zambia. The suitable soil test procedure for estimating available P needs to be identified. The objective of this study was to compare two soil test methods, impregnation of phosphorus (Pi) and Bray 1, in predicting P requirement of maize grown in Makeni (fine, mixed Isohyperthermic Udic Paleustalf), Maheba (clayey, kaolinitic, isohyperthermic Haplic Acrustox), and Konkola soil series (fine, oxidic, isohyperthermic oxic, Rhodustalf). The three soil series were treated with 0, 262, 524, and 1,048 mg P per pot as triple superphosphate (TSP). Maize was grown in pots, and after 8 weeks the plants were harvested and analyzed for total P concentration. Phosphorus uptake (P uptake) was calculated as a product of P concentration in the plant and maize dry matter yield. The soil was dried, sieved and analyzed for available P. The available P content estimated by Bray 1, and Pi soil tests was correlated with maize dry matter yield, and P uptake. The P which was extracted from Makeni soil series by Pi soil test correlated highly significantly (r=0.996**) with maize dry matter yield, but the correlation of maize dry matter yield and P extracted by Bray 1 soil test was not significant (r=0.908 ns), Correlation of P uptake with P extracted by Bray 1 soil test was high and more significant (r=0.991 * *), than correlation with P extracted by Pi soil test (r=0.958*). The P extracted from Makeni soil series by Pi soil test correlated highly significantly (r=0.996**) with maize dry matter yield, but the correlation of maize dry matter yield and P extracted by Bray 1 soil test was not significant (r=0.908 ns), Correlation of P uptake with P extracted by Bray 1 soil test was high and significant (r=0.990**), as well as correlation with P extracted by Pi soil test (r=0.958**). The correlation of P extracted from Maheba soil series by Pi soil test and maize dry matter yield followed the same trend as for Makeni series with correlation of r=0.990**. The correlation of P uptake and P extracted by Pi soil test was high but less significant (r=0.955*) than that for Makeni soil series. The correlation of P extracted by Bray 1 soil test with maize dry matter yield was high (r=0.973 *) and significant, but the correlation with P uptake was low and not significant (r=0.879 ns). The available P extracted from Konkola soil series by both Bray 1 and Pi soil tests produced poor and not significant correlation with maize dry matter yield, as well as P uptake. The results show that Bray 1 soil test extracted larger amounts of P from all the three soil series than P impregnation (Pi) soil test. The results further demonstrated that Pi soil test was consistently more closely related to P uptake and dry matter yield of maize grown in Makeni and Maheba soil series. Therefore, Pi soil test was more effective than Bray 1 soil test in evaluating soil solution P that the plant usually takes up.     

Detection of hexabromocyclododecane and its metabolite pentabromocyclododecene in chicken egg and fish from the official food control

During routine gas chromatography with electron capture detection (GC/ECD) analysis of chicken eggs, we observed that the most prominent peak in some samples did not match the retention time of any of the food contaminants screened. Subsequent GC coupled with mass spectrometry (GC/MS) studies clarified that the mass spectrum of the peak was very similar to hexabromocyclododecane (HBCD), which was also identified by GC/MS in the egg. The unknown compound was positively identified as pentabromocyclododecene (PBCDE), a metabolite of HBCD detected for the first time in foodstuffs. Studies of the analytical method used for the analysis of pesticides and contaminants showed that this cleanup method was suitable for the determination of HBCD and PBCDE, but storage of sample extracts resulted in the loss of HBCD when the sample extracts were not sufficiently purified. The concentrations of HBCD and PBCDE in the high polluted sample were 2.0 and 3.6 mg/kg egg fat. HBCD and PBCDE were also detected in two additional eggs at lower levels (<0.15 mg/kg), whereas 75 eggs did not contain these compounds (<0.02 mg/kg). We also detected HBCD and PBCDE in two samples of whitefish (Coregonus sp.), while an eel sample (Anguilla anguilla) positively tested for HBCD did not contain PBCDE. Surprisingly, the potential metabolite of HBCD, PBCDE, has not been detected before in any food or environmental sample. The present results indicate that more attention should be paid to the detection of HBCD and its metabolite PBCDE in chicken eggs.