酸度计法测定面粉中的味精

味精是人们日常生活中的主要调味品之一,其主要成分是谷氨酸钠,随着社会经济文化的日益提高,对美食美味的追求日益呈强烈之势。目前,在面粉中添加味精还是很少见的,测定面粉中味精的方法还未见报道,本文通过酸度计法对面粉中的味精进行了测定。1 实验部分1.1 仪器与试剂 pH-HJ 90B型酸度计;磁力搅拌器;DZ-1型滴定装置(上海第二分析仪器厂)碱式滴定管。     

酸度计法测定麸氨酸钠取样方法的探讨

麸氨酸钠又名麸酸钠、谷氨酸钠 ,分子式为C5H8O4Na·H2 O。麸氨酸钠是味精、鸡精及味鲜精等调味品的主要成分 ,麸氨酸钠的含量是这类调味品的主要成分 ,也是决定这类调味品品质的主要指标。测定麸氨酸钠含量的方法主要有旋光计法、凯氏定氮法和酸度计滴定法。在食品卫生检验中规定测定麸氨酸钠含量的方法是旋光计法和酸度计滴定法[1] 。酸度计滴定法是利用麸氨酸钠的两性作用 ,加入甲醛以固定氨基的碱性 ,使羧基一端显示酸性 ,根据产生酸的量 ,用氢氧化钠标准溶液滴定后定量。酸度计法由于其不需旋光计 ,因而更适合于基层单位。另旋光计…     

电位滴定法测定谷氨酸钠含量方法的改进

测定谷氨酸钠含量的方法有旋光计法、电位滴定法、高氯酸非水滴定法等。实际工作中 ,受仪器条件限制 ,基层实验室通常采用电位滴定法测定味精中的谷氨酸钠含量。该法操作简便 ,但是 ,测定结果仅达谷氨酸钠理论含量的 90 %左右〔1〕,不能正确反应味精的品质。我们采用合成试样做对照实验 ,对电位滴定法测定谷氨酸钠含量的方法进行了改进 ,取得了与仲裁法 (高氯酸非水滴定法 )一致的结果。现介绍如下。仪器与试剂　 (1)ＰＨＳ -Ｗ型智能酸度计 ;ＡＧ2 0 4型电子天平。 (2 )甲醛 (36 % ) ;谷氨酸钠标准品 (旋光计法分析测定含量 >99 7% ) ;氯化…     

自动电位滴定法测定调味品中总酸和氨基酸态氮

目前,国家卫生标准测定酱料调味品中总酸和氨基酸态氨的方法是人工电位滴定法,但人工滴定操作误差大,试验条件不容易控制。利用自动电位滴定仪可以连续自动测定调味品中的确总酸和氨基酸态氮的特点,作者用自动电位滴定仪代替人工操作测定调味品中的总酸和氨基酸态氮,结果令人满意,现报告如下。     

用自动电位滴定仪代替人工滴定法测定水的总硬度和钙含量

络合滴定是理化检验工作中常用的滴定方法。目前一般实验室滴定分析采用的是人工滴定法,它是根据指示剂的颜色变化指示滴定终点,然后目测滴定溶液消耗体积,计算分析结果。自动电位滴定仪法是通过电位的变化,由仪器自动判断终点,并计算测定结果,为了比较仪器和人工滴定方法的测定结果,我们选用总硬度和钙含量两个指标,分别用自动电位滴定法和人工滴定法进行样品分析。1　实验仪器和方法11　自动电位滴定法的仪器瑞士梅特勒—托利多(ＭＥＴＴＬＥＲ-ＴＯＬＥＤＯ)ＤＬ50型滴定仪;ＤＰ550光度电极。ＤＬ50滴定仪用光度电极感应溶液透光率变化,…     

酸度计法测定味精中麸氨酸钠方法的探讨

在国标方法中 ,味精中麸氨酸钠的测定方法有旋光计法和酸度计法。我们经多次实验证明 ,酸度计法与旋光计的测定结果相差较大。我们通过摸索 ,认为单纯靠改变滴定终点来改善结果的准确度不是办法[1] ,经改用高氯酸 -非水滴定法标定后的大于 99%的味精 (作为标准 )来标定氢氧化钠标准溶液的浓度[2 ] ,以ｐＨ 9.2为滴定终点[3 ] ,浓度以滴定度表示。其测定结果 (简称改进法 1)与旋光计法及高氯酸 -非水滴定法比较 ,均无差异显著性 ,精密度好。1　材料与方法1 1　酸度计1 2　甲醛 (36 % )1 3　高氯酸标准溶液 [Ｃ(ＨＣｌＯ4 ) =0 .10 0 0ｍｏｌ/…     

硝酸银标准滴定溶液测量不确定度分析与评定

[目的]分析与评定自配硝酸银标准滴定溶液的不确定度。[方法]按GB/T 5009-2003《硝酸银标准滴定溶液配制标定》自配硝酸银标准滴定液,并分析评定。[结果]对氯化钠标准物质、称量误差、使用玻璃量器、重复性测定、终点观察误差、温度引起的误差等不确定度分量的分析与评定,求得本次自配硝酸银标准滴定溶液的相对合成标准不确定度为0.79%。[结论]评定本次自配硝酸银标准滴定溶液的合成标准不确定度,为提高实验室和化学分析人员的技术水平、评价分析方法提供了重要依据。     

自动电位滴定法测定生活饮用水中总硬度的测量不确定度评定

在理化检测中,由于受各种因素影响.分析过程常带有误差,不能得到真值,而只能对其作出相对准确的估计.随着不确定度概念引入[1],它能更合理、完整地描述评定测量的准确程度.我们根据中国金属学会推荐技术和方法CSM01010101-2006滴定法测量结果不确定度评定规范[2],本文对自动电位滴定法测定生活饮用水中总硬度的不确定度进行了评定.     

氢化物原子荧光光度法测定味精中砷含量的不确定度评定

目的 确定氢化物原子荧光光度法测定味精中砷的不确定度主要来源，从而提高测定的准确性。方法 采用国家标准GB／T5009．11-2003氢化物原子荧光光度法对味精中砷测定的不确定度进行评定。结果 氢化物原子荧光光度法测定味精中砷产生不确定度最重要的份量为标准曲线产生的不确定度和A类不确定度。结论 在测定时应加强这两方面的控制，可提高测量结果的准确性。     

自动电位滴定法连续测定酱料调味品中总酸和氨基酸态氮

目前 ,国家卫生标准中测定酱料调味品中总酸和氨基酸态氮的方法是人工电位滴定法 ,但人工滴定操作误差大 ,试验条件不容易控制。利用自动电位滴定仪可以连续自动测定酱料类调味品中的总酸和氨基酸态氮的特点 ,作者用自动电位滴定仪代替人工操作测定酱料类调味品中的总酸和氨基酸态氮 ,结果令人满意 ,现报告如下 :1　材料与方法1 1　实验仪器与试剂1 1 1　自动电位滴定仪　 785ＤＭＰＴｉｔｒｉｎｏ型 ;6 .0 2 32、10 0复合ｐＨ电级1 1 2　 36 %甲醛溶液1 1 3　氢氧化钠标准溶液 (ＣＮａｏＨ=0 .0 5ｍｏｌ/Ｌ)1 2　实验方法　精密称取 5 .0 0…     

Trends in meningococcal disease in Italy in 1988

Meningococcal disease in Italy decreased 15% in 1988 from the previous year (290 vs. 342 cases). The decline was particularly evident in military cases (1.7/100,000 in 1988 vs. 5/100,000 in 1987) reflecting the full coverage of bivalent serogroup (A + C) meningococcal polysaccaride vaccine in army recruits, achieved since January 1988. The highest proportion of cases was seen in people older than 25 years of age (25%). Serogroup C constituted 60% of the isolates, while 19% belonged to serogroup B. The proportion of strains resistant to sulphonamides was 45%, while 15% were resistant to Minocycline and none to Rifampin. Out of the five military cases, only one (due to serogroup C) was attributable to the vaccine failure. A single coprimary case, but no secondary cases occurred among civilians. These findings are consistent with the trends reported in Italy in the previous years.     

Benzene in blood and phenol in urine in monitoring benzene exposure in industry

Determinations of benzene concentration in blood and of phenol in urine were made by head-space gas chromatography techniques on samples taken near the end of the work day from two groups of workers potentially exposed to low levels of benzene in the work-place atmosphere. Preliminary results suggest that benzene in blood is more reliable than phenol tests for assessing both exposure and uptake of benzene. Normal values of phenol in urine (10 mg/liter or less) were found in nearly all those cases in which benzene was detected in the blood.     

2015年郑州市饮用水放射性水平状况调查

目的了解郑州市不同地区、不同季节、不同水源类型的放射性水平。方法分别于丰水期和枯水期采集郑州市区黄河水源水、井水源水、丹江口水源水、出厂水和末梢水各一份;以县为单位,每单位采集出厂水、末梢水、水库水、河水、井水各1份,按《生活饮用水生活标准检验方法》(GB/T 5750.13-2006)检测饮用水中总α和总β放射性水平,依据《生活饮用水卫生标准》(GB 5749-2006)进行判定。结果丰水期、枯水期水体总α、总β放射性水平均低于国家标准限值。结论郑州市不同水源类型均处于正常的天然放射性本底水平。     

Occupational stress in nurses in psychiatric institutions in Taiwan

Nurses are known to be exposed to occupational stress. However, occupational stress is not well documented for nurses in psychiatric institutions in Taiwan. A cross-sectional study was conducted to explore the work-related stress and risk factors of nurses in psychiatric institutions in Taiwan. A structured questionnaire was distributed to nurses at five state-owned psychiatric hospitals in Taiwan in 2001. Demographic information, working environment, and personal health status were inquired. Occupational stress was assessed based on the Chinese version of Job Content Questionnaire (JCQ). General health status and mental health were evaluated by the International Quality of Life Assessment Short Form-36 (IQOLA SF-36). A total of 573 questionnaires were disseminated to nurses and 518 (90.4%) were satisfactorily completed by nurses, including 408 female full-time nurses who had been in their current work for more than 6 months. In the past one month, 17.2% of nurses reported being under significant stress often or always. Assault episodes were reported by 45.1% of nurses in the past 6 months. Among the nurses, 16.9%, 25.2%, 50.0%, and 7.8% belong to the "High strain", "Low strain", "Active", and "Passive" groups, respectively. Perceived occupational stress was associated with young age, widowed/divorced/separated marital status, high psychological demand, low workplace support, and threat of assault at work. Lower general health score was associated with low job control, high psychological demand, and perceived occupational stress. A lower mental health score was associated with low job control, high psychological demand, low workplace support, and perceived occupational stress. We concluded that nurses in psychiatric institutions are under significant stress related to work factors.     

Changes in nursing administration in supporting transplantation in Brazil

This historical and bibliographic study aimed to understand how Nursing was organized to support care in transplantation. The HISA, LILACS, BDENF, PERIENF and DEDALUS databases were consulted, and thirteen references were found, ten of which were scientific articles, two were master's dissertations and one was a doctoral thesis. The span of time chosen for study ranges from the date of the first kidney transplant in Brazil (1965), to the date of publication of the last scientific article found in the databases mentioned above (2003). After reading these articles, the ones that were similar in topic were grouped together, thus creating the thematic axis for the presentation of the results. The results showed that the Nursing profession has played an important and active role in transplants ever since the first procedure in 1965.     

2019年中国肿瘤流行病学研究进展

恶性肿瘤已成为中国居民的主要死因之一。近些年来,中国政府积极推进肿瘤预防和控制领域的研究工作,取得了很大的进步。本文简要汇总中国在肿瘤流行病学领域的研究进展,具体包括2019年的肿瘤负担、癌症危险因素及其干预、筛查和早期发现、癌症防治专项行动(2019-2022年)方案等方面,以期为我国肿瘤防治工作的有效开展提供技术支撑和理论依据。     

2012年绵阳市蔬菜中农药残留状况

目的 了解绵阳市2012年市售蔬菜中农药残留情况,为食用蔬菜监管提供依据.方法 全部样品均按照GB/T 5009-2003的方法进行农药的残留检测.依据GB 2763-2005《食品中农药最大残留限量》进行判定.结果 2012年共检测蔬菜165份,农药检出率和超标率分别为72.12％和23.64％.豆类、根茎类、叶菜类、瓜果菜类和食用菌类蔬菜检测农药残留超标率分别为8.00％、23.53％、36.00％、5.26％和27.03％,差异有统计学意义(x2=11.41,P＜0.01).不同种类农药超标率差异有统计学意义(x2 =62.42,P＜0.01).夏季和冬季蔬菜农药超标率差异无统计学意义(x2=3.44,P＞0.05).结论 绵阳市叶菜类蔬菜中农药残留情况较为严重,应采取有效措施,加强蔬菜的监督管理,从源头禁止高毒农药的使用,加大蔬菜种植、销售环节的监测,确保市民食用蔬菜的安全.