水产品中氯霉素检测条件的优化

目的建立液相色谱串联质谱法测定加工水产品中的氯霉素,并对提取溶剂、净化条件、流动相进行了优化。方法样品采用乙酸乙酯提取,HLB固相萃取柱净化,C_(18)色谱柱分离,ESI源负离子模式对氯霉素进行检测。结果氯霉素在0.1~10μg/kg范围内线性关系良好,相关系数为0.999,在基质样品中添加0.1、0.2和10.0μg/kg 3个水平药物,其回收率在95.0%~103.2%之间,相对标准偏差3.72%~6.85%,方法检测限为0.1μg/kg.结论该方法可靠、稳定,可满足加工水产品中氯霉素残留检测与确证需要。     

原苏联钨钼加工材生产状况

介绍了苏联主要难熔金属(钨钼)生产厂家及主要产品、工艺技术、装备状况,并作了初步评价。     

One-step extraction/methylation method for determining the fatty acid composition of processed foods

In a one-step extraction/methylation (OSM) method for determining individual fatty acids (FA) in processed food products, freeze-dried samples, containing 10–50 mg fat, were transmethylated without prior fat extraction with a mixture of methanol-HCl/toluene. After washing the organic phase the formed FA methyl esters were ready for separation by gas-liquid chromatography (GLC). The relative standard deviation for total FA content was <3.5%, regardless of the food type analyzed. Furthermore, the FA composition of selected fatty foods as obtained by the OSM procedure was almost identical with the FA composition of the pure fats extracted by the Soxhlet procedure and with chloroform-methanol, respectively. The OSM method is inexpensive and simple to perform and is, therefore, well suited for nutrient labeling studies, especially in situations where many samples have to be analyzed for their total FA content.     

Intake and risk assessment of nitrate and nitrite from New Zealand foods and drinking water

Exposure to excess nitrite is a potential health risk for humans. One hundred meat and processed foods and 100 vegetable samples purchased from New Zealand retail outlets were prepared as for consumption and analysed for nitrite and nitrate concentration using a standard, validated methodology. Nitrate concentrations ranged from less than the limit of detection (LOD = 5 mg kg^-1) in cheddar cheese and cream cheese-based dips to 3420 mg kg^-1 in lettuce. Nitrite was detected in half the processed foods and meats analysed (levels up to 119 mg kg^-1), but detected in only one vegetable sample above the LOD (broccoli at 27 mg kg^-1 nitrite). Concentration data were combined with 24 h dietary recall information to generate 4398 individual adult daily exposure scenarios for exogenous nitrite and nitrate including a contribution from water assessed from 1021 drinking water samples. The mean adult daily intake of exogenous nitrate and nitrite from food and water combined was 16 and 13% of the Acceptable Daily Intake (ADI), respectively, and therefore should not pose a health risk for the average consumer. A maximally exposed New Zealand adult is estimated to have an intake of up to seven times the ADI for nitrate. When the endogenous conversion of nitrate to nitrite is taken into account, approximately 10% of people with an average rate of conversion and half of all people with a high rate of conversion are estimated to exceed the ADI. Either the ADI is inappropriate and needs to be re-evaluated, or those individuals who have a high rate of conversion of nitrate to nitrite are at risk to adverse effects of nitrite exposure.     

Five-year survey of ochratoxin A in processed sultanas from Turkey

The results of surveillance for ochratoxin A (OTA) in 1885 samples of sultanas taken during five crop years between 1999 and 2003 are reported. The analytical method was based on extraction with methanol + sodium bicarbonate and clean-up by immunoaffinity column chromatography followed by high-performance liquid chromatography with fluorescence detection. The limit of detection for OTA was 0.3 µg kg^-1. The results show that 9.3% of the samples contained no detectable levels of OTA, whereas 0.6% had concentrations exceeding 10 µg kg^-1; the remaining 90.3% had levels within the range 0.3-10 µg kg^-1. The overall mean OTA concentration in the total number of 1885 samples taken was 1.36 ± 2.91 µg kg^-1; the overall median was calculated as 0.90 µg kg^-1.     

澜沧江古水水电站坝前复杂松散堆积体的基本地质特征及稳定性初步评价

本文通过详细的野外调查、勘测和类比分析，在对古水水电站坝前复杂松散堆积体的基本地质特征有了足够认识的基础上，从内外地质动力耦合作用来探讨并分析该复杂松散堆积体的形成机制，并对复杂松散堆积体的稳定性进行了初步评价，为对该松散堆积体的进一步深入研究和治理方案设计提供强有力的依据。     

APC values and volatile compounds formed in commercially processed,raw chicken parts during storage at 4 and 13 °C and under simulated temperature abuse conditions

Skinless chicken breast fillets, thighs, wings and boneless breast with skin were selected from the production line of a commercial processor. Samples were evaluated over time in storage at 4 and 13 °C and under temperature abuse conditions for microbial proliferation and production of volatile compounds (VCs). Aerobic plate counts (APCs) were enumerated and VCs quantitated at 24 h storage intervals; however, APC increases were not reflected by significant correlations with headspace VCs. Compounds isolated from sample headspaces by solid phase microextraction (SPME) and direct headspace sampling and then analysed by gas chromatography (GC), gas chromatography/mass spectrometry (GC/MS) and gas chromatography/chemiluminescence detection (GC/SCD) were hydrogen sulphide, methanethiol, ethanol, acetone, C5, C6 and C7 hydrocarbons, dimethyl sulphide, methyl ethyl ketone, carbon disulphide, 1‐propanol, ethyl acetate, 1‐butanol, S‐methyl thioacetate, 3‐methyl‐1‐butanol, dimethyl disulphide and dimethyl trisulphide. Compounds appearing in the samples with any degree of consistency and therefore considered pertinent for these analyses were ethanol, acetone, methyl ethyl ketone, ethyl acetate, hydrogen sulfide, dimethyl sulphide and carbon disulphide. Elevated APCs and VC diversity occurred more prevalently in those samples from higher‐temperature storage. Published in 2000 for SCI by John Wiley & Sons, Ltd.     

净菜加工中常用的消毒杀菌剂

综述了净菜常用的消毒杀菌剂如卤素及卤素化合物、离子化合物质、有机酸、活性氧化合物等各自的优缺点。