气相色谱法测定鸡蛋中氯霉素残留量

研究了鸡蛋中氯霉素残留的气相色谱测定方法。样品经乙酸乙酯提取后,用SylonBFT衍生化,进电子捕获检测仪(ECD)测定,外标法定量。结果表明,方法的线性范围在1.0～300ng/mL之间,平均回收率达93.4%,平均相对标准偏差5.5%,检测限为0.1μg/kg。     

水产品中拟除虫菊酯类农药残留检测方法的研究

建立了水产品中氯氰菊酯、甲氰菊酯、氰戊菊酯和溴氰菊酯等拟除虫菊酯类农药残留的提取、净化以及毛细管气相色谱的测定方法。选择40mL正己烷：丙酮（V／V,2：1）混合溶液作为提取液,经冷冻去脂,柱层析净化过程中选用3g中性氧化铝作为净化填料,30mL正己烷：丙酮（V／V,4：1）混合溶液进行洗脱,然后用气相色谱法测定,外标法定量。实验结果表明,在10～200ng／mL线性范围内线性良好,相关系数在0．9993～0．9998。标准品添加量在10～66μg／kg范围内,罗非鱼样品加标实验的回收率在76．9～90．3％,相对标准偏差在1．25—4．66％,样品中氯氰菊酯、甲氰菊酯、氰戊菊酯、溴氰菊酯残留量检测方法的检出限为10μg／kg。另外采用鳗鱼和对虾样品的标准添加回收实验进行方法的验证,实验结果表明,平均回收率达到70％以上,相对标准偏差小于10％,符合药残检测要求。本方法可用于进行水产品中多种菊酯类农药残留的检测分析。     

水产品中五氯酚及其钠盐的高效液相色谱串联质谱检测方法的优化

对水产品中五氯酚及其钠盐的高效液相色谱串联质谱检测方法进行了深入优化。样品通过三乙胺碱化的70%乙腈水溶液提取,使目标物保持在离子态,之后采用大粒径的阴离子交换(MAX LP)小柱进行富集,依次用5%氨水(V/V)溶液、甲醇和50%的甲醇水溶液(含2%甲酸,V/V)进行淋洗,最后用5 mL的4%甲酸甲醇溶液洗脱。净化浓缩后样品采用C_(18)色谱柱进行分离,以甲醇和5 mmol/L乙酸铵水溶液为流动相进行梯度洗脱,多反应监测负离子模式扫描,采用同位素稀释内标法定量。目标化合物在相关范围内线性关系良好,相关系数r不低于0.99,方法在不同水产品基质中的定量限均为0.5μg/kg,基质加标回收率范围为92.4%～102.0%,相对标准偏差为3.21%～9.15%。经验证,本研究优化后的方法适用于水产品中五氯酚及其钠盐的残留检测,且相比标准方法,减少了前处理所需时间,同时避免了堵柱情况出现,解决了蟹类样品回收率偏低的问题。     

气相色谱法测定鸡蛋中氯霉素残留量

研究了鸡蛋中氯霉素残留的气相色谱测定方法。样品经乙酸乙酯提取后，用Sylon BFT衍生化，进电子捕获检测仪（ECD）测定，外标法定量．结果表明，方法的线性范围在1．0～300ng／mL之间，平均回收率达93．4％，平均相对标准偏差5．5％，检测限为0．1μg／kg。     

气相色谱质谱法测定海洋沉积物中的类雌激素烷基酚和双酚A

通过研究建立了同时测定海洋沉积物中辛基酚、壬基酚、双酚A残留量的气相色谱质谱法。实验样品用甲醇超声萃取,经铜粉、石墨化炭固相萃取小柱净化,七氟丁酸酐衍生,HP-5ms柱分离,气相色谱质谱测定。方法回收率84．3％～94．5％之间,4-N-辛基酚、壬基酚、双酚A定量限分别为0．25、0．15、0．15μg/kg。该实验定量准确,可满足对沉积物中烷基酚类化合物的定性确证和定量分析。     

农产品中除草剂残留检测的研究进展

化学除草剂在农业生产中的使用率呈迅速上升趋势,其在农产品中的残留问题已成为人们关注的热点.本文综述了近些年来农产品中不同种类除草剂残留检测的样品前处理方法及分析技术,为食品安全检测提供依据.前处理方法中液液萃取法仍为普遍使用的提取方法,加速溶剂萃取法或基质固相分散萃取法因提取效率高、溶剂耗费少、回收率高也得到广泛应用.固相萃取法、凝胶渗透色谱或分子印迹固相萃取法作为净化方法,常与上述提取方法联用.检测技术上,气相色谱和液相色谱是目前主要的分析方法,其与质谱联用不仅检测限低、选择性好,而且定性更准确,符合痕量检测的发展趋势,因而在除草剂残留分析中发挥着越来越重要的作用.     

GB/T 22338—2008方法测定水产品中氯霉素残留量存在的不足与探讨

我国国家标准《动物源性食品中氯霉素类药物残留量测定》(GB/T 22338—2008)规定了对水产品中氯霉素类(CAP、氟甲砜霉素和甲砜霉素)残留测定的气相色谱—质谱(GC-MS)法,但在检测过程中发现加标回收率经常超过100 %,且不稳定,难重复。在实际检测中,应用食品中氯霉素残留量气相色谱质谱联用负化学源法测定的标准操作程序检测水产品中氯霉素的残留量可以获得更为理想的结果,更能满足检测工作需要。文章指出基质效应是造成前一种方法加标回收率偏高的主要原因,详细介绍了后一种方法的前处理过程和实验条件,并对改进的部分进行了探讨。     

鲈鱼组织中阿维菌素、伊维菌素残留的高效液相色谱荧光检测法研究

采用高效液相色谱分离,荧光检测器检测,建立鲈鱼组织中阿维菌素和伊维菌素残留的检测方法.样品用乙腈提取,碱性氧化铝SPE柱净化,N-甲基咪唑和三氟乙酸酐的乙腈溶液为衍生化试剂,常温衍生化15 rain.荧光检测器激发波长为365 nm,发射波长为475 nm.结果表明,阿维菌素和伊维菌素衍生化产物的浓度与峰面积在0.5～200 ng/ml范围内有很好的线性关系.添加水平为1～10 μg/kg,阿维菌素和伊维菌素的平均回收率在80.6%～88.0%和78.8%～82.8%之间,相对标准偏差均小于10%.阿维菌素的检出限为0.1/μg/kg,伊维菌素为0.2 μg/kg.该方法简便、灵敏、可靠,可用于鲈鱼组织中阿维菌素和伊维菌素残留的检测.     

液相色谱-串联质谱法测定养殖水体中的氯霉素

本文采用回收率较高、较稳定的内标定量法（对养殖水体中氯霉素的检测方法进行了研究, 建立了养殖水体中氯霉素残留的检测方法。应用液相色谱-串联质谱（LC-MS/MS）测定养殖水体中氯霉素的含量,量取250 mL水样,用100 mL乙酸乙酯分2次萃取,萃取液经旋转蒸发仪浓缩近干,以40%的甲醇-水溶液定容至1 mL。氯霉素标准系列溶液浓度为0.25、0.50、1.00、1.25、2.50、5.00 ng/mL,氘代氯霉素的含量均为2.0 ng/mL,上机检测,内标法定量。结果表明,氯霉素为外标,氘代氯霉素为内标,其峰面积比值（y）与浓度比值（x）的曲线方程为：y=1.136512x+0.012050（R2＝0.9990）;该方法氯霉素的检出限为2 ng/L,定量限为4 ng/L,仪器线性范围为0.25～5.0 ng/mL;加标浓度在2～20 ng/L时,平均回收率在80%～110%,相对标准偏差小于10%。实验证明该方法比较稳定、灵敏度高,适用于检测养殖水体中氯霉素的含量。     

气相色谱测定水中六六六和滴滴涕残留处理方法研究

对气相色谱法测定水中HCHs和DDTs残留的前处理方法进行研究,新的前处理方法（方法二）以5μg/L、50μg/L、150μg/L作为不同添加水平测定水中HCHs和DDTs的回收率,出峰顺序为：①α-HCH、②γ-HCH、③β-HCH、④δ-HCH、⑤ρ＇ρ-DDE、⑥ο＇ρ-DDT、⑦ρ＇ρ-DDD、⑧ρ＇ρ-DDT,加标回收率范围为85.3%-114.6%。与方法一（GB7492-87）相比,能够达到定量准确、具有高的精密度和准确度,而且操作较简单,需时较短,因此本文推荐使用方法二作为气相色谱法测定水中HCHs和DDTs残留前处理方法。     

Rare serotype occurrence and PFGE genotypic diversity of Streptococcus agalactiae isolated from tilapia in China

Previously, we reported 10 PEGE types of 85 tilapia Streptococcus agalactiae(GBS), which shifted from Streptococcus iniae in China, by using PEGE method. Presently, larger and more representative tilapia GBS were isolated, for the ?rst time in China, to characterize their serotypes and genetic diversities more precisely than had done before. 168 GBS strains were distributed in ?ve provinces of China, in which Guangdong, Guangxi and Hainan were the major ones, holding36.9%(62/168), 37.5%(63/168) and 19.6%(33/168), respectively. Serotypes, Ia, Ib and III, were observed in these strains and the most predominant one was Ia(95.2%), which mainly distributed in Guangdong, Guangxi and Hainan. Ia initially occurred in 2009, it shoot up to 32.1% in 2010,but decreased to 16.1% in 2011 before went up to 45.2% in 2012. Ib sporadically occurred during2007–2011, III onlyoccurred in 2012. 14 different PFGE types, including 4 new types(N, O,P and Q), were observed, in which B, D, F and G were the predominant types, holding 83.9%(141/168) of the total GBS strains. Ia corresponded to 11 PFGE types(A–H, N–P), in which type D predominated(51%). Ib represented 3 genotypes(I, J and Q) and III harbored only 2genotypes(N and F). Type N and Fsynchronously presented in Ia and III. In summary, the genetic diversity of tilapia GBS varied by serotypes and changed with geographical locations and years.Although Iastillpredominated, new rareserotypeIII alreadyoccurred in China.     

Growth hormone (GH) and reproduction: a review

Interaction between growth and reproduction occurs in many vertebrates and is particularly obvious at certain stages of the life cycle in fish. Endocrine interactions between the gonadotropic axis and the somatotropic axis are described, the potential role of GH being emphasised. A comparative analysis of these phenomena in mammals, amphibians and fish, suggests a specific role of GH in the physiology of puberty, gametogenesis and fertility. It also shows the original contribution made by studies on the fish model in this field of investigations.     

Purification and partial characterization of GtHs (cfLH and cfFSH) from Indian walking catfish (Clarias batrachus) (L.) and development of a homologous ELISA for cfLH

Two gonadotropins (GtH; Qa and Qb) were purified by gel filtration and ion exchange chromatography from the pituitaries of Indian walking catfish (Clarias batrachus). The presence of GtH during purification was assessed by in vitro oocyte maturation and in vivo steroidogenic activity, and their identities were determined by elution profiles, molecular weight, biological activities and yield. The molecular weights of Qa and Qb were 37 and 42 kDa, respectively, and composed of distinct subunits (Qa: 20 and 14 kDa and Qb: 26 and 18 kDa). Polyclonal antibodies raised against Qa immunostained Qa, Qb and pituitary GtH cells. A competitive Qa‐ELISA was developed whose sensitivity was 6.25 ng mL^?1 (1.25 ng well^?1) with intra‐ (3.5%) and inter‐ (12.4%) assay coefficients of variation. Displacement curves parallel to the standard were obtained with plasma and pituitary extracts of catfish, Qb and carp GtHII. The assay was validated by measuring the plasma Qa levels after LHRH treatment and in relation to ovarian growth in the female catfish during different reproductive phases. Based on the results, Qa and Qb corresponded to fish LH and FSH respectively. The findings will increase the knowledge of the mechanisms controlling fish reproduction and identification of sensitive phases in fish in captivity for hormonal manipulation.     

Controlled infection of Poecilia reticulata Peters (guppy) with Tetrahymena by immersion and intraperitoneal injection

Tetrahymena is a protozoan parasite, which infects guppy, Poecilia reticulata Peters, and causes substantial economical losses in commercial farms worldwide. Studies of guppy infected by Tetrahymena require standardized infection protocols. The LD50 for Tetrahymena infection of guppies by intraperitoneal (IP) injection was calibrated, and the level obtained was 946 parasites per fish. Guppy infection with Tetrahymena by immersion, imitating the natural route of infection via the integument, was studied under normal or stress conditions. Exposure to cold and netting (CNI) and to cold only (CI) followed by immersion exposure to 10 000 Tetrahymena per mL resulted in 22.5% and 19.2% mortality, respectively, as compared to 14.2% and 10% in groups that were netted only (NI) or non‐stressed (I). Histopathology revealed that immersion infection resulted in a systemic infection. Lysozyme levels, measured 3 weeks after infection, were significantly higher in the CNI group (288 μg per mg protein) compared with CI‐, NI‐ and I‐treated groups (94.5, 64 and 62.3 μg mg^?1, respectively). There was no evident parasite immobilization activity in body homogenates, suggesting no development of acquired immunity. Re‐infection by IP injection revealed no increase in protection in any of the treatment groups, mortality range of 56.3–75%, higher than in the non‐exposed control (40.6% mortality).     

Evaluation of a Fast Method Based on the Presence of Two Restriction Sites in the Mitochondrial ND5 (mt ND5) Gene for the Identification of Scomber Species

The purpose of this work was to evaluate the suitability of a method based on the presence of two restriction sites (for Hae III and Hindf I) in the mitochondrial NADH dehydrogenase subunit 5 (mt ND5) gene to identify Scomber species. The evaluation was performed on 144 reference and market samples by sequencing of the entire 505-bp fragment of the mt ND5 gene and of a 464-bp fragment of the Kocher fragment of the cytochrome b gene (mt Cytb). Sequence analysis of any of the two fragments allows the identification of each of the four Scomber species, but S. japonicus and S. colias had the same restriction sites at the ND5 amplicon and would not have been differentiated by this analysis. Similarly, loss of the Hae III site in some S. scombrus individuals would have misidentified them as not being Scomber. All the market products were correctly labeled except one acquired in Spain labeled as originating in the Atlantic and containing S. japonicus.     

Imported ornamental fish are colonized with antibiotic‐resistant bacteria

There has been growing concern about the overuse of antibiotics in the ornamental fish industry and its possible effect on the increasing drug resistance in both commensal and pathogenic organisms in these fish. The aim of this study was to carry out an assessment of the diversity of bacteria, including pathogens, in ornamental fish species imported into North America and to assess their antibiotic resistance. Kidney samples were collected from 32 freshwater ornamental fish of various species, which arrived to an importing facility in Portland, Oregon from Colombia, Singapore and Florida. Sixty‐four unique bacterial colonies were isolated and identified by PCR using bacterial 16S primers and DNA sequencing. Multiple isolates were identified as bacteria with potential to cause disease in both fish and humans. The antibiotic resistance profile of each isolate was performed for nine different antibiotics. Among them, cefotaxime (16% resistance among isolates) was the antibiotic associated with more activity, while the least active was tetracycline (77% resistant). Knowing information about the diversity of bacteria in imported ornamental fish, as well as the resistance profiles for the bacteria will be useful in more effectively treating clinical infected fish, and also potential zoonoses in the future.     

Effect of iodophor disinfection of non‐hardened Salmo trutta eggs on their bacterial and fungus load

This study investigated the efficiency of iodophor disinfection (135 ppm active iodine for 15–30 min) of non‐hardened Salmo trutta eggs against different groups of bacteria and against fungus. Egg samples were taken from non‐disinfected and from disinfected eggs, microorganisms were cultured on specific nutrient media and their mass was measured by turbidimetric methods. Bacteria and fungus mass of non‐hardened eggs could be reduced but not eliminated by iodophor disinfection with 135 ppm active iodine for 15 min. The extent of reduction was 47–65% (Experiment 1). The efficiency of disinfection increased with disinfection time as the reduction in bacteria and fungus mass was 40–55% after 15 min and 58–74% after 30 min (Experiment 2). Disinfection efficiency of iodophor solution diluted in water (reduction 49–57%) and of iodophor solution diluted in sodium chloride solution iso‐osmolar to the oocytes (reduction 52–61%) was similar (Experiment 3). The reduction in bacteria and fungus mass was persistent as it was 39–72% lower in embryos deriving from disinfected eggs than in embryos deriving from non‐disinfected ones (Experiment 4). In conclusion, the tested disinfection method is inadequate to eliminate pathogens completely but it could positively influence immune defence of eggs and embryos.     

Nitrogenous waste excretion and accumulation of urea and ammonia inChalcalburnus tarichi (Cyprinidae), endemic to the extremely alkaline Lake Van (Eastern Turkey)

The endemic, anadromous cyprinidChalcalburnus tarichi is the only fish species known to occur in alkaline Lake Van (Eastern Anatolia, Turkey). EightC. tarichi were maintained individually in Lake Van water (17 – 19°C; pH 9.8; 153 mEq·I^–1 total alkalinity; 22 total salinity) and tank water samples analyzed for 24 h in 2 to 4 h intervals. At zero time, < 1µM ammonia was present and urea was undetectable in the tank water; at 24 h, total ammonia and urea made up 114±32 and 35±25µM, respectively. Over the experimental period, ammonia-N and urea-N excretion averaged 1041±494 and 607±169moles·kg^–1 fish·h^–1, respectively. The extent of urea excretion was highly variable between specimens. Uric acid excretion was not detectable.Urea was present at high concentrations in all tissues and plasma (25 – 35moles·g^–1·ml^–1) of freshly caughtC. tarichi; total ammonia content of the tissues was by a factor of 1.9 (liver) to 3.0 (brain) lower. High arginase activity (2.4±0.2 U·min^–1·g^–1) was detected in the liver ofC. tarichi but ornithine carbamoylphosphate transferase, a key enzyme of the ornithine-urea-cycle, was absent. Ureagenesis is likely through degradation of arginine and/or uricolysis. High glutamine synthetase activity (11±0.6 U·min^–1·g^–1) and low ammonia content in brain suggest that, like other teleosts,C. tarichi has an efficient ammonia detoxification in the brain, but in no other tissue.Nitrogenous waste excretion at alkaline pH is discussed. The ability ofC. tarichi to excrete high levels of ammonia at extremely alkaline pH is unique among teleosts studied so far. The mechanism of ammonia excretion under Lake Van conditions remains to be elucidated.