Determination of organochlorine pesticide and polychlorinated biphenyl residues in fatty fish by tandem solid-phase extraction cleanup

A rapid, multiresidue solid-phase extraction (SPE) technique for determination of organochlorine pesticide and polychlorinated biphenyl (PCB) residues in nonfatty fish was modified for use with fatty fish. In the modified procedures, samples are extracted with acetonitrile, and the extract is cleaned up with both C18 and Florisil SPE columns. Residues are determined by gas chromatography with electron capture detection. The original method was modified for use with fatty fish by reducing the amount of tissue extracted and by using an improved Florisil SPE cleanup. Recovery data are presented for 24 fortified organochlorine pesticide residues (0.12 ppm) and 3 fortified PCB residues (0.80 ppm) from flounder, bluefish, and shad samples, which contained 0.8, 5.4, and 22.6% fat, respectively. For the 3 types of fish, recoveries of 23 of 24 fortified organochlorine pesticide residues ranged from 55 to 129%, and recoveries of 3 fortified PCB residues ranged from 55 to 104%. There were no significant differences in recovery based on fish species and/or fat content for the majority of residues studied. This SPE method and the official AOAC method yielded comparable results for fish containing incurred organochlorine residues.     

Possibilities and limits of modern rapid procedures for process control of cleaning and disinfection methods

In food production and processing, hygienic measures and their control gain more and more importance. The disadvantage of the commonly used control methods is their time-consuming process providing results after 24 hours at the earliest. From all microbiological rapid methods developed in the past, the bioluminescence method is a suitable hygienic measure for detection of adenosine triphosphate (ATP). In this test, ATP from microorganisms and ATP from somatic cells is detected. Within 2 minutes cleaned and disinfected surfaces can be reliably evaluated. Different equipment was tested in the laboratory and in a meat processing plant. The quality of the hygiene evaluation of the cleaned surfaces is decisively depending on the surface structure of the materials and on the product residues remaining in the peak-to-valley heights. Therefore, limiting values for ATP shall be determined individually for each plant. In this case, the bioluminescence method can be recommended as suitable tool for hygiene monitoring.     

固相萃取-气相色谱法测定大米中有机氯有机磷农药残留

采用固相萃取方法,结合气相色谱建立了同时检测大米中15种有机氯、有机磷农药残留的分析方法.样品用乙腈提取,氨基固相萃取柱净化,经DB-5石英毛细管柱分离后,直接用气相色谱(GC)检测,外标法定量.结果 表明15种农药在0.01 ～0.2 μg/mL浓度范围内呈现良好的线性关系,相关系数r均大于0.995 1,样品在2个...     

Multiresidue liquid chromatographic method for determining residues of mono- and dibasic penicillins in bovine muscle tissues

A liquid chromatographic method with UV detection at 325 nm was developed for simultaneous determination of amoxicillin, ampicillin, penicillin G, and cloxacillin residues in bovine muscle tissue as their mercaptide derivatives. The penicillins are extracted from bovine tissues with 0.1 M phosphate buffer (pH 8.5), cleaned up on a t-C18 Sep-Pak cartridge, and eluted with 2 mL acetonitrile. After the acetonitrile in the eluate is evaporated to dryness, the residue is dissolved in 200 microL (40 + 60, v/v) acetonitrile-phosphate buffer (pH 6.5) and derivatized with acetic anhydride and mercuric chloride in the presence of 1,2,4-triazole at 65 degrees C for 30 min. Gradient analysis on a Spherisorb 5 microns ODS(2) (octadecyl silane) analytical column using a binary mobile phase consisting of acetonitrile and 0.10 M phosphate buffer (pH 6.5) in the presence of 0.0157 M sodium thiosulfate at 1 mL/min permits determination of each intact penicillin in bovine muscle tissue at > or = 10 ppb with recoveries > or = 72%. This laboratory method provides detection sensitivities equivalent to those of rapid tests used for screening beta-lactam drug residues in bovine tissue samples for regulatory enforcement.     

Gas-liquid chromatographic determination of alachlor (2-chloro-2', 6'-diethyl-N-(methoxymethyl)-acetanilide) herbicide residues in corn and soybeans

A method has been developed for the extraction and determination of alachlor (2-chloro-2',6'-diethyl-N- (methoxymethyl)-acetanilide) residues in green corn and soybeans. Residues are extracted with acetonitrile and cleaned up on a Florisil column. The methylene chloride extract is sufficiently clean for electron capture gas-liquid chromatographic analysis and for verification by thin layer chromatography. Average recoveries of spiked samples (0.2 ppm) were 69 and 82% for corn and soybeans, respectively. This procedure could be useful for the detection of the parent compound in these crops soon after field application, but it does not detect metabolites.     

Antimicrobial drug residues in milk and meat: causes, concerns, prevalence, regulations, tests, and test performance

This paper presents a historical review of antimicrobial use in food animals, the causes of residues in meat and milk, the types of residues found, their regulation in Canada, tests used for their detection, and test performance parameters, with an emphasis on immunoassay techniques. The development of residue detection methods began shortly after the introduction of antimicrobials to food animal production in the late 1940s. From initial technical concerns expressed by the dairy industry to the present public health and international trade implications, there has been an ongoing need for reliable, sensitive, and economical methods for the detection of antimicrobial residues in food animal products such as milk and meat. Initially there were microbial growth inhibition tests, followed by more sensitive and specific methods based on receptor binding, immunochemical, and chromatographic principle. An understanding of basic test performance parameters and their implications is essential when choosing an analytical strategy for residue testing. While each test format has its own attributes, none test will meet all the required analytical needs. Therefore the use of a tiered or integrated system employing assays designated for screening and confirmation is necessary to ensure that foods containing violative residues are not introduced into the food chain.     

Identification of cholesterol as a possible interference in the analysis of fish tissue for industrial chemical residues

The presence of cholesterol in cleaned up fish tissue extracts has been established by gas-liquid chromatography and confirmed by mass spectrometry. It was found both in extracts cleaned up by gel permeation chromatography and in those extracts prepared by the AOAC method for nonfatty foods. It is not normally observed in routine residue analyses because selective gas chromatographic detectors such as electron capture are commonly used.     

Effects of carbohydrate restriction on the hypoglycemic phase of the glucose tolerance test

A gas-liquid chromatographic method has been developed for the analysis of residues of chlorphoxim, 2-chloro-alpha ((diethoxyphosphinothioyl)oxy)imino)-benzeneacetonitrile, in water and fish. The method is based on the in-block methylation of chlorphoxim with 0.01M trimethylanilinium hydroxide in methanol. The derivative, O,O-diethyl O-methyl phosphorothioate, was determined quantitatively by using a flame photometric detector specific for phosphorus. The in-block reaction is 70% efficient. Water samples were extracted with hexane; fish were extracted with methylene chloride and cleaned up on an acetonitrile-hexane partition column. Recoveries from water and fish samples spiked with chlorphoxim averaged 86.3 and 80.4%, respectively. Limits of detection were 10.0 ppb for 5 g samples of fish and 0.10 ppb for 300 ml water samples.     

The challenge of preparing the curved root canal

Heavily restored teeth which become pulpally involved are now often root canal treated rather than extracted. While this is laudable it has a significant impact on the practice of endodontics today. The curved calcified canal can prove very difficult to prepare to its natural shape by conventional techniques and there is always the likelihood of iatrogenic damage. To compensate for this many clinicians tend to under-prepare these canals, perhaps leaving them inadequately cleaned and certainly remarkably difficult to fill to length. The purpose of this article is to outline the stages of and the rationale behind a hand instrumentation preparation method which uses the balanced force method of movement of files from canal entrance to apical constriction. In the authors' experience this technique has gone a long way towards solving the problem of cleaning and shaping the fine curved canal. With some practice, but no extra expense, the technique described will not only speed up canal preparation but will also make it more predictable.     

Assignment of HLA-antigens in CREGs facilitates the detection of acceptable mismatches in highly sensitized patients

The purpose of this study was to investigate whether in highly sensitized patients (HSPs) the acceptable HLA-A and -B mismatches (AMs) can be predicted on the basis of patients' HLA-phenotype. To this affect, 1000 historical serum samples obtained from 50 HSPs (PRA > 60%), panel reactive antibodies (PRA) value and the specificity of class I anti-HLA-antibodies were detected by two techniques in parallel: An anti-human globulin augmented cytotoxicity (AHG-CDC) and an Elisa technique. Thereafter, class I HLA-antigens of the nonreactive cells in the screening panel and class I HLA-antigens of the patients were assigned to CREGs. The AMs for each one of the patients were detected using a separate cell panel, which was prepared in a way to include almost all the HLA-antigens belonging to the CREGs of the patients as well as to those of the nonreactive cells in the screening panel. It was found that the AMs in HSPs, detected with this protocol were more, compared to those we usually detect using only the HLA-antigens of the nonreactive cells in the screening panel (up to 8 versus 2-5). Both, the definitively detected AMs, and the HLA-specificities of the nonreactive cells of the screening panel belonged to the same CREGs. These CREGs were equivalent to the CREGs of class I HLA-phenotypes of each patient. The data presented in this paper introduce a new, rapid and easier way for the detection of AMs in HSPs. According to this proposed protocol, the assignment of patients' standard class I private HLA-phenotypes in CREGs, not only greatly facilitates the detection of AMs, but the detected AMs are also in fact significantly more than those determined by the conventional methodology. We have also confirmed that the majority of antibodies induced by HLA alloimmunization are directed against mismatched shared or public group epitopes CREGs. Moreover, we have confirmed that prospective matching for major CREGs would be feasible on a national level and would not significantly prolong waiting time, which could result in a significant augmentation of the potential donor pool.     

Evaluation of amperometric detector for liquid chromatographic determination of 2-phenylphenol residues in orange rind

A modular component liquid chromatograph has been assembled which has on-stream ultraviolet (UV) and amperometric detectors connected to a dual pen recorder. In this method, the commonly used UV detection technique provides a reference for direct comparisons of results from the amperometric detector. The system has been evaluated and applied to the determination of 2-phenylphenol (2PP) fortified in orange rind. The method is not tedious; before liquid chromatographic analysis, the sample is extracted with methylene chloride and cleaned up on a Florisil column. The method is sensitive to less than 1 ppm 2PP fortified in orange rind; there are no electrically oxidizable interference, from control samples, in the chromatographic region of 2PP. Some background interference does appear from the same samples on the UV chromatogram. Thus, amperometric detection is more specific than UV detection for this application.     

Determination of organochlorine and organophosphorus pesticide levels in imported beef

A simple and efficient cleanup method was established for capillary gas chromatographic determination of 12 organochlorine and 11 organophosphorus pesticides in beef. Extracted fat was subjected to silica gel dry column chromatography and further cleaned up by Florisil minicolumn chromatography for organochlorine pesticide analysis, while partitioning between n-hexane and acetonitrile of the extract and silica gel minicolumn chromatography were employed for the analysis of organophosphorus pesticides. Several samples (imported Australian beef) were analyzed by the proposed method. DDT was detected in 14 (0.01-0.10 ppm). BHC was found in 11 (0.003-0.031 ppm) and dieldrin was demonstrated in 2 (0.004 and 0.008 ppm). Heptachlors and the 11 organophosphorus pesticides investigated were not detected in any of the meat samples.     

In vitro and in vivo comparisons of valnemulin, tiamulin, tylosin, enrofloxacin, and lincomycin/spectinomycin against Mycoplasma gallisepticum

The minimum inhibitory concentrations (MICs) for valnemulin, tiamulin, enrofloxacin, tylosin, and lincomycin/spectinomycin were determined for a virulent strain of Mycoplasma gallispeticum (MG). At the initial reading, the lowest MICs were seen with valnemulin and tiamulin, followed by tylosin, enrofloxacin, and a relatively high MIC for lincomycin/spectinomycin. At the final reading, at 14 days, a similar pattern was obtained, with valnemulin giving the lowest MIC (< 0.008 mg/ml). The same strain of MG was used to infect groups of 20 2-day-old chicks in two separate experiments. In both, several concentrations of valnemulin and tiamulin and one each of tylosin and enrofloxacin were administered to separate groups in the drinking water. In the second experiment, one group of chicks was given lincomycin/spectinomycin. Each experiment had one infected unmedicated group and an uninfected unmedicated group. Mortality, clinical signs, and gross lesions, in both experiments, were significantly less (P < 0.001) in the uninfected and infected medicated groups (except for the two lowest dosages of valnemulin, lincomycin, and spectinomycin) than in the infected unmedicated groups. Also, the mean body weight gain was greater in the uninfected and infected medicated groups. Among the infected birds, MG was recovered from fewer chicks in the infected medicated groups except for the lowest two dosages of valnemulin. Serologic results were negative for the uninfected groups, and there were fewer positive reactors for the infected medicated groups except for the group treated with lincomycin/spectinomycin. Valnemulin should prove to be a useful addition to the antimicrobials in the control of MG infection in chickens.     

Molecular characterisation of Cryptosporidium parvum from two large suspected waterborne outbreaks. Outbreak Control Team South and West Devon 1995, Incident Management Team and Further Epidemiological and Microbiological Studies Subgroup North Thames 1997

Routine paper chromatographic screening of the urine of racing greyhounds exposed to BIGELOIL, a veterinary counter-irritant, revealed metabolites suggestive of menthol, an ingredient of BIGELOIL. To determine whether BIGELOIL use caused these metabolites, 2 Dalmatian dogs were exposed to BIGELOIL. Thin-layer chromatographic screening of their urine confirmed that exposure to BIGELOIL by either dermal or oral routes causes the same metabolites as those observed in the racing greyhounds. Metabolites suggestive of thymol were also present in some samples. We conclude that, if metabolites suggestive of menthol are detected in urine of animal athletes, further analysis for the other performance-affecting ingredients of BIGELOIL should be undertaken.     

Selective detection in RP-HPLC of Tyr-, Trp-, and sulfur-containing peptides by pulsed amperometry at platinum

A technique for electrochemical detection of Trp-, Tyr-, and sulfur-containing peptides, using a two-step potential waveform at a platinum wall-jet electrode, has been developed. The detection is fully compatible with reversed-phase HPLC employing gradients of acetonitrile in water/trifluoroacetic acid. At approximately +1.2 V (first potential) versus Ag/AgCl, Trp-, Tyr-, and Cys-containing peptides are predominantly detected, while at +1.4 - 1.6 V, Met- and (Cys)2-containing peptides are additionally detected. The electrode surface is cleaned by the second potential (+2.0 V). the linearity is at least 2 orders of magnitude. The sensitivity is in the picomole range. By using postcolumn electrochemical conversion, the selectivity toward Met and Cys-containing peptides can be enhanced. Applications are shown for the determination of caseinomacropeptide (6.6 kDa) and a tryptic map of beta-casein.     

L-fucose residues on cellulose-based dialysis membranes: quantification of membrane-associated L-fucose and analysis of specific lectin binding

Contact of mononuclear human leukocytes with cellulose dialysis membranes may result in complement-independent cell activation, i.e. enhanced synthesis of cytokines, prostaglandins and an increase in beta 2-micro-globulin synthesis. Cellular contact activation is specifically inhibited by the monosaccharide L-fucose suggesting that dialysis membrane associated L-fucose residues are involved in leukocyte activation. In this study we have detected and quantitated L-fucose on commercially-available cellulose dialysis membranes using two approaches. A sensitive enzymatic fluorescence assay detected L-fucose after acid hydrolysis of flat sheet membranes. Values ranged from 79.3 +/- 3.6 to 90.2 +/- 5.0 pmol cm-2 for Hemophan or Cuprophan respectively. Enzymatic cleavage of terminal alpha-L-fucopyranoses with alpha-L-fucosidase yielded 7.7 +/- 3.3 pmol L-fucose per cm2 for Cuprophan. Enzymatic hydrolysis of the synthetic polymer membranes AN-69 and PC-PE did not yield detectable amounts of L-fucose. In a second approach, binding of the fucose specific lectins of Lotus tetragonolobus and Ulex europaeus (UEAI) demonstrated the presence of biologically accessible L-fucose on the surface of cellulose membranes. Specific binding was observed with Cuprophan, and up to 2.6 +/- 0.3 pmol L-fucose per cm2 was calculated to be present from Langmuir-type adsorption isotherms. The data presented are in line with the hypothesis that surface-associated L-fucose residues on cellulose dialysis membranes participate in leukocyte contact activation.     

Neonatal screening for congenital hypothyroidism

In Austria, neonatal screening for congenital hypothyreosis has been introduced since 1976 as a part of the national screening program for inborn errors of metabolism. Capillary blood spots are collected on filter paper from all newborns on day 3 to 5 and are subsequently investigated with a delayed fluorescence-immunoassay (DELFIA) for the determination of TSH. Since 1992 we have detected 105 patients with congenital hypothyreosis among 365,120 newborns. The recall rate of the primary TSH screening is about 0.35%. Only primary (thyroidal) hypothyreosis, but not secondary and tertiary (pituitary and hypothalamic) types of hypothyreosis are detected by the primary TSH newborn screening. As TSH is physiologically high during the first 2 days of life, the trend to early hospital discharge will result in a significant increase of the recall rate in future.     

Problems associated with drug residues in beef from feeds and therapy

Drug residues in beef have been reported internationally. These include antimicrobials, anti-inflammatories, growth promotants, parasiticides and insecticides. The main factors associated with residues are animal age and use, and failure to observe withdrawal time for regular or extra-label use. Public health concerns include toxic and anaphylactic reactions, and development of drug-resistant strains of bacteria. The maximum residue level (MRL) is the current standard for residues in food adopted by the Codex Committees of the Food and Agriculture Organisation and World Health Organisation, but is not universally accepted or standardised. Detection of residues at slaughter is a critical point in residue control. Several live animal tests are available, but these vary in reliability and usage. After slaughter, tissues sampled and tests used are more uniform. To prevent international trade barriers associated with drug residues in beef, the following conditions should be implemented: standardisation of testing methods used to detect drug residues; standardisation of methods for determining MRLs; establishment of active surveillance programmes to monitor residues.     

鞍钢冷轧厂2号生产线钢板表面质量的优化

为了提高鞍钢新轧钢公司冷轧厂2号生产线的产品质量,结合生产实践,对影响产品表面质量的因素进行了分析研究,采取了一系列措施,对各因素进行了优化,使产品表面质量得到了大幅度改善,冷轧卷清洗后的反射率达到了92%.