毛细管气相色谱法测定聚氯乙烯食品包装中的氯乙烯单体

研究采用毛细管气相色谱法检测聚氯乙烯薄膜中残留的氯乙烯单体,并用气相色谱质谱法进行确证.样品中的氯乙烯单体采用静态顶空技术提取.利用极性毛细管气相色谱柱进行分离并结合氢火焰离子化检测器进行高灵敏度检测.氟乙烯单体在0.05～0.2 mg/L的浓度范围内有较好的线性关系,相关系数为0.999,相对标准偏差在3.1%以内,检测低限为0.5 mg/kg,该方法具有较好的检测精密度和灵敏度.     

GC MS法测定人造革残留氯乙烯单体

建立了测定聚氯乙烯人造革中的残留氯乙烯的顶空气相色谱 质谱法(GC MS)。采用N,N 二甲基乙酰胺(DMA)溶解聚氯乙烯人造革样品,在70℃下平衡30 min,顶空进样进行气相色谱 质谱分析。结果显示,在0.2～20μg范围内,该方法线性关系良好,相关系数r=0.999。对样品进行3组不同浓度水平的加标测定(n=6),平均回收率为88%～92%,相对标准偏差(RSD)小于5.5%,检出限为0.2 mg/kg。该方法简便、快速,准确,可用于测定聚氯乙烯人造革中氯乙烯单体含量。     

鞋用人造革中氯乙烯单体含量的测定

以聚氯乙烯鞋用人造革为材料,建立了大体积顶空-气相色谱/质谱联用测定人造革中氯乙烯单体含量的方法。试验对顶空平衡时间和平衡温度的条件进行了优化,确定了最佳的操作条件,最终采用平衡温度为80℃,平衡时间为30 min,并选用DB-624毛细管色谱柱进行分离。结果显示,在0.3～25μg范围内该方法线性关系良好,相关系数r=0.998 8。对样品进行3组不同浓度水平的加标测定(n=3),平均回收率为85%～94%,精密度(RSD)<5.0%,检出限(LOD)为0.2 mg/kg。该方法可用于鞋用人造革中氯乙烯单体含量的简便、快速和准确测定。     

利用气相色谱质谱法测定棉花中杀虫剂残留量

探讨气相色谱-质谱法用于同时检测棉花中8种残留杀虫剂的检测效果。采用丙酮-正己烷(1+1,V/V)超声萃取法提取棉花中的杀虫剂残留物,将提取液定容后用气相色谱-质谱进行分析。结果表明:采用气相色谱-质谱法同时测试棉花中8种杀虫剂,杀虫剂浓度在0.2μg/mL~5.0μg/mL范围内与峰面积具有良好的线性关系;该方法平均回收率在91.8%~107.8%,测定结果的相对标准偏差在1.95%~4.69%。认为气相色谱-质谱法可用于棉花中8种杀虫剂残留的同时测定。     

食品包装材料中3种残留单体含量的测定分析

探讨顶空气相色谱法同时测定食品包装材料中残留氯乙烯、偏二氯乙烯和1,1-二氯乙烷单体含量的可行性。样品在自动顶空进样器中,用N,N-二甲基乙酰胺在80℃下提取40 min,气相色谱分析,外标法定量。在本试验条件下,氯乙烯、偏二氯乙烯和1,1-二氯乙烷单体线性关系良好,相关系数分别为0.999 0、0.999 6和0.999 4,检出限分别为0.02、0.25、1.00 mg/L,回收率为90.0%~97.7%,RSD值为1.86%~3.10%。     

葡萄酒中乙醇含量的气相色谱法测定

为建立气相色谱法直接测定葡萄酒中的乙醇含量的方法,将样品稀释后直接进样,经过DB-FFAP毛细管色谱柱分离后用气相色谱FID检测器进行分析。在所建立的最佳实验条件下,葡萄酒中乙醇峰得到有效分离,线性良好,最低检出限为0.01%,相对标准偏差为3.6%~4.0%,平均回收率为90%~95%。说明该方法灵敏、简单易操作、准确可靠,用此法检测葡萄酒中的乙醇含量,结果满意。     

GC-MS法测定罗汉果中拟除虫菊酯农药残留量

建立气质联用(Gas chromatography-mass spectrometry,GC-MS)测定罗汉果中6种拟除虫菊酯类农药的残留量方法。样品用石油醚-丙酮混合溶剂超声提后过固相萃取小柱净化,经HP-5MS色谱柱分离,以气相色谱质谱法进行检测,用外标法计算含量。结果表明:6种拟除虫菊酯类农药在0.1μg/mL~1.0μg/mL范围内呈现良好的线性关系,相关系数为0.999 1~0.999 9,检出限为0.139μg/kg~5.262μg/kg。样品中3个加标水平的回收率为83.5%~106.1%,相对标准偏差(RSD)为0.9%~6.5%。本试验所建立的方法操作简便,具有良好的回收率,精密度和灵敏度,符合检测要求,可用于罗汉果中6种拟除虫菊酯类农药残留的测定。     

Florisil固相萃取-气相色谱法测定蜂蜜中的六六六、滴滴涕残留量

目的建立Florisil固相萃取-气相色谱法测定蜂蜜中六六六(hexachlorocyclohexane,HCH)、滴滴涕(dichlorodiphenyl trichloroethane,DDT)残留量的分析方法。方法样品加水后利用乙腈提取残留农药,选用Florisil柱中加入乙二胺-N-丙基硅烷(primary secondary amine,PSA)为净化材料,以固相萃取方法净化样品,以DB-17石英毛细管色谱柱分离,采用气相色谱-电子捕获检测器测定,以峰面积外标法定量。结果 8种农药在3个添加水平下的平均回收率在70.2%~97.4%之间,相对标准偏差为1.2%~9.6%,方法检出限为0.00006~0.0004 mg/kg,均能达到农残分析的要求。结论该方法具有操作简便、快速、准确的特点,适用于蜂蜜中六六六、滴滴涕残留的分析。     

气相色谱质谱法同时测定甘蔗中18种农药残留

建立了气相色谱质谱(GC-MS)同时测定甘蔗中常见的18种农药残留方法。甘蔗样品破碎后,经乙腈提取,用QuEChERS方法净化,采用GC-MS进行分析检测,在选择离子模式(SIM)下,用外标法进行定量,线性良好(r20.996),检出限为0.09~1.82μg/kg。分别在甘蔗样品中添加18种标准农药样品50、100、400μg/kg水平上进行添加回收率实验,方法的回收率范围为82.8%~106.6%,相对标准偏差为0.9%~8.9%。该方法具有前处理简单快捷、灵敏度和准确度高等优点,符合农药残留检测要求,满足甘蔗中农药残留检测需要。     

凝胶渗透色谱-气相串联质谱同时测定海产品中34种多氯联苯和76种农药

建立海产品中34种多氯联苯和76种农药气相色谱-串联质谱分析方法。用乙腈为萃取溶剂,均质法均质提取样品,盐析法除水,凝胶渗透色谱净化,收集26~50 min流出液,在线浓缩。用气相色谱柱(DB-1701)分离后,在多离子反应监测模式(MRM)下进行质谱检测。在1.0~500μg/kg范围内线性关系良好(R2﹥0.99),方法检出限(LOD)0.05~108.43μg/kg。空白样品添加回收率51.6%~120.5%,相对标准偏差范围0.84%~24.5%,回收率60%~110%,目标化合物为106种。该方法通用性强,选择性好,灵敏度、准确度和精密度均符合多残留检测的技术要求,适用于动物源性海产品中多残留的日常检测。     

Headspace GC/MS analysis of residual vinyl chloride and vinylidene chloride in polyvinyl chloride and polyvinylidene chloride products

A headspace GC/MS analysis method for the simultaneous determination of residual vinyl chloride (VC) and vinylidene chloride (VDC) in polyvinyl chloride (PVC) and polyvinylidene chloride (PVDC) products was developed. A test sample was swelled overnight with N,N-dimethylacetamide in a sealed vial. The vial was incubated for 1 hour at 90 degrees C, then the headspace gas was analyzed by GC/MS using a PLOT capillary column. The recoveries from spiked PVC and PVDC samples were 90.0-112.3% for VC and 85.2-108.3% for VDC. The determination limits were 0.01 microg/g for VC and 0.06/microg/g for VDC, respectively. By this method, VC was detected in two PVC water supply pipes at the levels of 0.61 and 0.01 microg/g. On the other hand, VC and VDC were not detected in any of the food container-packages or toys tested.     

Hydrolytic stability of terephthaloyl chloride and isophthaloyl chloride

The phthaloyl chloride isomers, terephthaloyl chloride (TCl) and isophthaloyl chloride (ICl), are high production volume chemicals used in polymers to impartflame resistance, chemical resistance, and temperature stability and as water scavengers. In these studies, we determined the hydrolytic stability of TCl and ICl and their hydrolysis products in aqueous solutions. Hydrolysis rates for TCl and ICl were initially determined by gas chromatography/flame ionization detection in water buffered at pH 4.0, 7.0, and 9.0 and 0 degrees C for up to 30 min. Subsequent studies determined the products from TCl and ICl hydrolysis. The parent phthaloyl chlorides (TCl and ICl), their intermediate hydrolysis products (designated as the "half-acids"), and their stable hydrolysis products (terephthalic acid (TPA) and isophthalic acid (IPA)) were determined by high-performance liquid chromatography. The half-lives (t(1/2)) of TCl and ICl ranged from an average of 1.2 to 2.2 min and from 2.2 to 4.9 min, respectively, at pH 4-9 and 0 degrees C. The observed first-order rate constants (k(obs)) ranged from an average of 530 to 1100 (x 10(5) s(-1)) for TCl and 240 to 520 (x 10(5) s(-1)) for ICl. Both phthaloyl chlorides formed their respective short-lived intermediates, in which one of the two carboxylic acid chloride functionalities reacts with water to form the carboxylic acid ("half-acid"). Subsequently, the half-acids underwent further hydrolysis so that greater than 90% of the initial phthaloyl chloride hydrolyzed in less than 60 min at 0 degrees C. The hydrolysis products TPA and IPA were hydrolytically stable, undergoing no further transformations after 20 min at pH 7 and 25 degrees C. This work demonstrated that TCl, ICl, and their respective half-acids will not be persistent in aqueous systems for a time sufficient to have a sustained toxicological effect on aquatic organisms (less than 1 h). Performing additional aquatic toxicity studies, biodegradation studies, and potentially mammalian studies on TCl and ICl are unnecessary since the existing information on TPA and IPA with the hydrolysis data presented here is sufficient to address questions on the fate and effects of these two substances in aqueous environments.     

氯化银比浊法测定水样中氯离子

目的建立氯化银比浊法测定水样中氯离子的方法。方法用硝酸调节溶液pH,加入硝酸银溶液,使之与氯离子反应,生成氯化银悬浊液,利用分光光度法测定吸光度,通过工作曲线确定浓度。结果氯离子浓度为0～6μg/mL时线性方程为Y=0.0473X-0.0004,相关系数为0.9995,线性关系较好,相对标准偏差为2.0%,回收率范围为96.89%～108.25%。结论此方法检测效率高,适合测定氯离子含量较小的样品。     

Partial replacement of sodium chloride with potassium chloride in marinated rabbit meat

This study was aimed at evaluating the consequences of sodium chloride reduction by potassium chloride up to 50% on technological, sensorial and microbiological traits of marinated rabbit meat. In total, 226 rabbit loin meat samples were obtained and subjected to vacuum tumbling using solutions with different NaCl/KCl ratios. Replacing of sodium chloride up to 30% by potassium chloride did not change microbiological traits (total aerobic mesophilic and lactic acid bacteria maximum cell loads), sensorial acceptability (perceived saltiness and overall liking) and technological traits (pH, colour, texture, cooking loss and yield). Otherwise, reduction in sodium chloride to 50% significantly decreased perceived saltiness (4.15 vs. 4.73; P < 0.05) and reduced microbial shelf life by 1 day when compared to control, even if there was still no effect on technological traits. In conclusion, it is feasible imparting an added value for processed rabbit meat products by reduction in sodium content that could increase market interest.     

聚氯乙烯假发的染色

介绍了聚氯乙烯纤维的性能特点.聚氯乙烯纤维强度高、弹性好、耐磨性和耐气候性能好、保暖性能和保健性好、抗燃性强.针对聚氯乙烯纤维吸湿性差、不耐热的特性,提出了对聚氯乙烯假发采用分散黑EX-SF染料染色,加入助染剂,控制染色温度为(55±1)℃,染色中间加食盐,染色20 min左右的改色染色工艺;指出了聚氯乙烯假发染色和后处理过程的注意事项.     

Effect of application of ammonium chloride and calcium chloride on alfalfa cation-anion content and yield

A major factor predisposing the cow to periparturient hypocalcemia, or milk fever, is being fed a prepartum ration with a high dietary cation-anion difference (DCAD). The DCAD can be favorably altered to prevent milk fever by decreasing K and Na or increasing Cl and S in forages for cows in late gestation. The objective of this study was to test the hypothesis that application of Cl to alfalfa could increase Cl in forage, thereby lowering DCAD. We conducted a field experiment at 2 Iowa locations in which established plots of alfalfa were treated in April 2001 with 0, 56, 112, or 168 kg of Cl/ha using ammonium chloride, calcium chloride, or a mix of the 2 sources with equal amounts of chloride coming from each source. Plots were harvested 4 times in 2001 and once in 2002 and plant tissue analyzed for mineral composition. Applying chloride from either source once in the spring resulted in increased plant chloride content over all 4 cuttings for that year. Averaged across both locations, chloride levels were elevated from 0.52% in control plots to 0.77, 0.87, and 0.89% Cl in plots treated with 56, 112, and 168 kg of Cl/ha, respectively. Chloride application had no effect on plant potassium, sodium, calcium, magnesium, or phosphorus. These results suggest chloride application can elevate chloride content and lower DCAD values of alfalfa, and also maintain crop yield.     

Taste properties of potassium chloride alone and in mixtures with sodium chloride using a check-all-that-apply method

As consumers try to reduce their sodium consumption for health purposes, the food industry seeks ways to reduce the sodium content in products while maintaining palatability. One potential solution for lowering sodium content is using potassium chloride (KCl) as a substitute. However, many people find KCl to have unpleasant off-tastes, which limits its effectiveness to replace sodium chloride (NaCl). This study examined the taste properties of KCl using a check-all-that-apply (CATA) ballot. The objectives were to see which terms people use to describe KCl and in what ways this changes in various combinations with NaCl. Panelists were served mixtures of varying NaCl and KCl concentrations, and evaluated them using a set of predetermined terms on a CATA ballot. Frequency counts were taken, and binomial and McNemar tests were performed to see which stimuli changed the most between samples. Results showed that adding KCl increased salt perception slightly, and salty was chosen more frequently when in combination with NaCl. Adding NaCl in a mixture with KCl decreases unpleasant side tastes associated with KCl, such as bitter, chemical, and metallic.