以硝酸钯作为基体改进剂——石墨炉原子吸收法测定水产品中的铅

铅元素易挥发、难测定,进行石墨炉原子吸收法测铅需要选择合适的基体改进剂。研究比较了硝酸钯和磷酸二氢铵两种基体改进剂的应用效果,加入硝酸钯后,灰化温度可达到1 100℃,而加入磷酸二氢铵,灰化温度只能达到900℃,因此以硝酸钯作为基体改进剂,利用连续自动进样塞曼纵向扣背景原子吸收法测定水产品中铅元素含量,10.00~50.00μg/L浓度范围内线性关系良好,R~20.9900,平均相对标准偏差3.7%,回收率106.8%,与磷酸二氢铵相比,硝酸钯可提高灰化温度和原子化效率,具有较好的应用效果,此方法线性范围宽、灵敏度高、准确稳定,有较大的推广价值。     

原子吸收光谱法测定黄颡鱼体中微量元素的初步研究

黄颡鱼肌肉经过硝酸、商氯酸等处理后，用火焰原子吸收光谱法。测定其中的铁、锌、镉、铅含量，用石墨炉原子吸收光谱法测定其中的铬。结果表明：长湖黄颊鱼肌肉中含铁208．19μg/g，含锌68．50μg／g，含镉37．57μg/g，含铅130．90μg／g，含铬377．01ng／g。     

真江蓠对氨氮去除效率与吸收动力学研究

以真江蓠(Gracilaria asiatica)为实验材料,在实验室水平上测定了真江蓠培养密度对NH4-N去除效率和吸收速率的影响,比较了真江蓠在氮半饥饿和氮饱和状态下的氨氮吸收动力学特征以及不同起始浓度NH4-N对其吸收速率的影响.结果表明:真江蓠密度为2～24 g·L-1时,5 h内随着藻体密度增大和实验时间延长,真江蓠去氨氮能力也增强.当藻体密度为24g·L-1时,真江蓠在5 h内去除氨氮效率最高,达到99.77%.各种藻体密度在起始阶段保持较高吸收速率(30～41 μmol·g-1·h-1),随后藻体密度与吸收速率呈反比关系,其最低藻体密度组(2 g·L-1)在3 h和5 h吸收速率最大,分别为28.33 μmol·g-1·h-1和18.85μmol·g-1·h-1.在起始浓度梯度实验中,氮半饥饿和氮饱和真江蓠吸收氨氮的最大吸收速率和半饱和常数在1 h均达到最高值,分别为116.47、159.40μmol·g-1·h-1和439.70、913.61 μmol·g-1·h-1.之后随着培养时间的延长而降低.氮半饥饿和氮饱和真江蓠对NH4-N的吸收差别不显著;当氨氮浓度为300～500μmol·L-1时,氮半饥饿的真江蓠在起始1 h内有一个快速吸收阶段(40.7～102.1μmol·g-1·h-1),吸收速率与NH4-N浓度几乎成正比,此时不符合米氏动力学饱和方程,而在低N浓度下(100～200μmol·L-1),藻体对NH4-N的吸收则没有出现这种现象;随着培养时间延长,直到NH4-N浓度达到一定限度时,吸收速率可达到一极大值而符合米氏动力学饱和方程.该研究结果为大规模栽培真江蓠净化水体和生态修复提供了理论依据.     

微波消解 — 原子光谱法测定海洋生物体中砷和镉

应用优化后的微波消解—原子光谱法测定6种海洋生物体标准物质中砷和镉元素含量,其中,使用原子荧光光谱法测定砷,石墨炉原子吸收光谱法测定镉,并评估测试结果的准确度和精密度。实验结果表明,砷和镉分别在1.0～20.0和0～5.0μg/L范围内有良好的线性关系,其线性相关系数均在0.999 5以上,测定结果的准确度和精密度令人满意,方法快速简便,消解完全且试剂节省,污染少,适合于海洋生物体中砷和镉含量的定量分析。     

超高效液相色谱-电喷雾串联质谱法同时测定鱼类加工品中12种杂环胺类化合物

建立了超高效液相色谱-电喷雾串联质谱法同时测定鱼类加工品中12种杂环胺类化合物（HAAs）的分析方法。经过条件优化,肉样选用乙酸乙酯、氨水和三乙胺提取,提取液经MCX固相萃取小柱净化,按V（甲醇）∶V（氨水）=9∶1洗脱,采用Thermo Hypersil Gold C18色谱柱,以甲醇和5 mmol.L-1乙酸铵溶液为流动相进行梯度洗脱分离,电喷雾离子源（ESI）,正离子模式,采用选择反应监测（SRM）扫描模式,内标法进行定量分析。结果表明,12种HAAs在1.0～100.0μg.L-1范围内线性关系良好,相关系数R〉0.99,在12 min内实现分离,3个加标水平的平均回收率为42.98%～125.00%（n=6）,相对标准偏差（RSD）为1.49%～9.88%,检测限（LOD）为0.3～1.0μg.kg-1。该方法简便快捷,准确度高,易推广应用,可作为快速测定鱼类加工品中多种HAAs的有效方法。     

抗坏血酸预还原钯作基体改进剂GFAAS法测定贝类产品中铅的含量

在抗坏血酸预还原钯作为基体改进剂的条件下,确定了灰化温度及原子化温度,建立了一种石墨炉原子吸收光谱法测定贝类产品中铅的实验方法.结果表明,在抗坏血酸预还原钯为基体改进剂、灰化温度为800℃和原子化温度为1 900℃条件下,铅在0 ～ 50.0 μg/L的浓度范围内具有良好的相关性,相关系数为0.9 997.当取样量为0.250 g干样、定容体积为25 mL时,方法检出限为0.04 mg/kg,加标回收率为93.5％ ～ 103.0％,RSD为1.41％～4.35％.参考物质缢蛏的测定值在证书推荐值的允许误差范围内.该方法比其他方法的灵敏度高,准确可靠,适合贝类产品中铅的检测.并应用此方法测定了福建省中北部海域贝类中铅的含量,结果表明,福建省中北部海域中贝类均未超标,安全性良好.     

牙鲆肌肉中微量元素的测定

以微波消解样品,利用石墨炉法原子吸收光谱法测定了牙鲆肌肉中的铅、镉、砷、硒、铜、铬、锰、镍、钻、锡等十种微量元素的含量。结果表明此方法简便、精密度和灵敏度高。牙鲆肌肉中铬、铜、锰和硒的含量分别可达1．096μg／g、0．613μg／g、0．347μg／g和0．199μg／g,提示牙鲆肌肉中各种有益微量元素含量较高,而有害微量元素砷、铅、镉等的含量均较低,分别仅为0．083μg／g、0．097μg／g和0．010μg／g。因此,牙鲆肌肉是人类微量元素的良好来源。     

HPLC-MS/MS法测定水产品中硫酸粘菌素、杆菌肽及维吉尼霉素M1的残留量

建立了水产品中硫酸粘菌素(CS)、杆菌肽(BTC)及维吉尼霉素M1(VBGMM1)3种多肽类抗生素残留量检测的HPLC-MS/MS法。样品经水溶液[V(甲醇)∶V(0.1%甲酸水溶液)=2∶5]提取,4%三氯乙酸乙腈除蛋白,乙腈饱和正己烷除脂,过OASIS HLB(60 mg)小柱净化后,利用HPLC-MS/MS法,以选择反应监测模式检测,外标法进行定量分析。CS和BTC在0.01～10.00 mg.L-1质量浓度范围内线性良好,VGMM1在0.002～2.000 mg.L-1质量浓度范围内线性良好,R2均大于0.995;3种多肽类抗生素的检出限分别为CS 10μg.kg-1、BTC 10μg.kg-1、VGMM12μg.kg-1,定量限分别为20μg.kg-1、20μg.kg-1和4μg.kg-1;选择3个不同浓度水平做加标回收,平均回收率在72.3%～103.9%,相对标准偏差为1.10%～10.92%。该方法具有操作简便、准确性高、灵敏度高和重现性好等优点,可为检测水产品中这3种药物的残留提供相关技术支持。     

水产品中镉两种测定方法的不确定度评定比较

为建立和比较水产品中镉含量测定不确定度评定的方法,分别采用石墨炉原子吸收法和电感耦合等离子体质谱法测定FAPAS质控样品T07279QC中镉的含量,分析不确定度的主要来源,建立水产品中镉测定的不确定度评定的数学模型,并计算两种方法的不确定度分量。试验结果表明,石墨炉原子吸收法不确定度主要来源于标准曲线拟合,而电感耦合等离子体质谱法主要来源于标准溶液配制,石墨炉原子吸收法测定镉含量的扩展不确定度高于电感耦合等离子体质谱法,两种方法测定质控样品T07279QC中镉的含量分别为(7.47±0.470) mg/kg和(7.53±0.376) mg/kg,两种方法的测定值均在质控样品参考值含量5.76~9.33 mg/kg内。     

石墨炉原子吸收法在测定日本对虾体中铅、铜含量的应用

采用石墨炉原子吸收法测定日本对虾体中的Pb、Cu。结果测得Pb为0.1152mg/kg、Cu为6.4493mg/kg。Cu的含量明显高于Pb，表明日本对虾对Cu有一定的富集能力。测定回收率，Pb为99.0%－101.0%，Cu为98.0%－98.8%。此方法可靠、简便。     

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.     

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 performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.     

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.     

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).     

The optimal dietary protein level of juvenile silver sillago Sillago sihama at three dietary lipid levels

A 5 × 3 factorial growth trial was conducted to evaluate optimal dietary protein and lipid levels (dietary protein level, DP; dietary lipid level, DL) for juvenile Sillago sihama (S. sihama) (2.0 ± 0.02 g, initial weight). Fish were fed 15 diets containing 5 DPs (350, 400, 450, 500 and 550 g/kg) and 3 DLs (60, 90 and 120 g/kg) for 8 weeks. The interaction between proteins and lipids significantly influenced the feed conversion ratio, condition factor, body composition, antioxidant indices and lipase activity (p < .05). DP 450 g/kg showed the highest average final body weight. DPs 500 and 550 g/kg significantly decreased the protein efficiency ratio (p < .05). DL 120 g/kg showed the highest percentage weight gain. The low feed conversion ratio was found in diets P45L12, P55L9 and P55L12. Diet P45L12 showed high superoxide dismutase activities. DP 450 g/kg showed the lowest average malondialdehyde content. Lipase activity was increased by increasing DP (p < .05) with a fall at DP 550 g/kg. Under the present experimental conditions, the optimal DP for S. sihama was 450 g/kg under the DL 120 g/kg.     

Involvement of gonadal steroids in final oocyte maturation of white perch (Morone americana) and white bass (M. chrysops): in vivo and in vitro studies

Plasma estradiol-17 (E₂), testosterone (T), 17,20-dihydroxy-4-pregnen-3-one (DHP) and 17,20,21-tri-hydroxy-4-pregnen-3-one (20-S) levels were measured by radioimmunoassay (RIA) in white perch (Morone americana) and white bass (M. chrysops) that were induced to undergo final oocyte maturation (FOM) with human chorionic gonadotropin (hCG). Plasma DHP levels increased in females of both species in association with oocyte germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) and decreased thereafter. Plasma 20-S levels also increased with oocyte GVM in white bass, but were several-fold lower than DHP levels. Circulating E₂ and T levels were greatest during GVM and GVBD in both species and decreased to low levels during oocyte hydration and ovulation. Follicles from white perch and white bass which received a priming injection of hCG in vivo, produced both DHP and 20-S in vitro after exposure to hCG and their oocytes underwent GVBD. Ovarian incubates from unprimed fish of either species produced only E₂ and T and their oocytes did not complete GVBD. Oocytes from unprimed bass, but not perch, matured when follicles were exposed to hCG in vitro. Both trilostane and cycloheximide blocked in vitro production of DHP and 20-S and oocyte GVBD by white perch follices. DHP and 20-S were equipotent inducers of FOM in the GVBD bioassay. None of several other structurally-related steroids tested were effective within a physiological range of concentrations. These results indicate a role for DHP and 20-S in the control of FOM in white perch and white bass.