原子荧光法测定食品中总砷的3种前处理法比较

目的建立准确、可靠、稳定的测定食品中总砷的分析方法。方法利用湿消解法、微波消解法、干灰化法分别处理食品样品,用氢化物发生原子荧光光谱法测定食品中总砷的含量。结果鱼粉、紫菜(GBW 10023-GSB-14)、大米(GBW 10010)、鸡肉(GBW 10018)干灰化法测定总砷的结果为3.18±0.052、27.01±0.063、0.104±0.002、0.115±0.004 mg/kg均在参考值范围,加标回收率为93.7%~98.5%,RSD≤2.31%;湿消解法测定结果为3.12±0.041、26.93±0.072、0.103±0.003、0.112±0.003 mg/kg均在参考值范围,加标回收率为89.2%~97.5%,RSD≤1.92%;微波消解法处理鱼粉和紫菜的测定结果为1.74±0.032、15.40±0.096 mg/kg不足参考值的60%,但大米、鸡肉的测定值为0.102±0.001、0.114±0.005 mg/kg在参考值范围,加标回收率为96.3%~97.5%,RSD≤2.51%。湿消解法具有灵活调节消解温度,消解酸种类、用量和消解时间等优点,可适用于大部分食品样品的前处理;微波消解法耗费时间短,但用酸量大,适用于砷存在形态相对简单的样品;干灰化法耗费时间较长,适用于挥发温度高、油脂含量高、砷存在形态比较复杂的样品。结论湿消解法、干灰化法适用于大部分食品样品的前处理,微波消解法使用有局限性,仅适应于砷存在形态相对简单的样品。     

原子荧光光谱法和电感耦合等离子体质谱法测定紫菜中总砷的3种前处理方法比较

目的 比较微波消解、湿法消解、干灰化法3种前处理对原子荧光光谱法(atomic fluorescence spectrometry, AFS)与电感耦合等离子体质谱(inductively coupled plasma mass spectrometry, ICP-MS)测定紫菜中总砷(As)结果的影响。方法　用微波消解、湿法消解、干灰化法对紫菜标准物[总As参考值：(27±6 )mg/Kg]进行前处理和总砷衍生萃取,分别采用AFS与ICP-MS对总砷进行测定。结果　AFS和ICP-MS测定总砷的线性相关系数均达到0.999。结果显示3种前处理应用于AFS和ICP-MS测定紫菜中总As符合标准物质总As参考值范围的包括：硝酸微波消解后ICP-MS测定总砷为26.45 mg/Kg;硝酸：双氧水=3:2, V/V微波消解后ICP-MS测定总砷为27.85 mg/Kg;硫酸1.25 mL、硝酸：高氯酸=4:1, V/V湿法消解后AFS测定总砷为27.84 mg/Kg;硝酸湿法消解后ICP-MS测定总砷为24.63mg/Kg;硝酸：高氯酸=4:1, V/V湿法消解后ICP-MS测定总砷为28.04 mg/Kg;干灰化法后AFS测定总砷为27.62 mg/Kg;干灰化法后ICP-MS测定总砷为26.49mg/Kg。结论　不同的前处理方法、仪器对紫菜样品中总As的测定结果不同。3种前处理后均可用于ICP-MS测定紫菜中的总As,平均值24.63 mg/Kg ~28.04 mg/Kg,RSD2.8%~5.6%,回收率90.1%~106.5%。干灰化法平均值27.62 mg/Kg,RSD6.7%,回收率99.2%~100.9%,可用于AFS测定紫菜中总As。湿法消解采用硫酸1.25 mL、硝酸：高氯酸=4:1, V/V此介质最为理想,总As平均值27.84 mg/Kg,RSD1.8%,回收率101.5%~105.6%;微波消解后AFS测定总As为8.92、12.31、12.25 mg/Kg,远低于紫菜成分分析标准物质中总砷的参考值范围,不适合用于测定紫菜样品中总的As。     

不同消解方式对电感耦合等离子体质谱法测定 水产品中无机元素的影响

目的为研究不同消解方法对水产品中重金属元素测定的影响,找到最佳的前处理方法。分别采用高压消解罐消解、微波消解和湿法消解3种方法对紫菜(GBW10023)、扇贝(GBW10024)、大虾(GBW10050)等成分分析标准物质进行前处理。方法在电感耦合等离子体质谱(ICP-MS)优化条件下,测定3种标准物质3种消解方法的9种元素(Pb、Cd、Cr、As、Sn、Ni、Cu、Mn、Sr)含量,与标准参考值做对比,并测定各元素的回收率。结果 3种消解方法的测定结果基本在参考范围内,消解效果均较为理想,而微波消解法消解最彻底且消解液澄清,所受环境干扰最小,测定值更接近参考值,回收率也基本在90%~105%之间,较为理想;紫菜标物的湿法消解和高压消解罐消解法中均有剩余残渣;且湿法消解的回收率结果较不理想;9种元素标准曲线的线性关系较好,相关系数均大于0.999,仪器灵敏度、精准度较高。结论综合比较认为,微波消解法更适合扇贝、大虾、紫菜等水产品中无机元素测定的前处理要求。     

不同前处理方法对食品中总砷含量测定结果的影响

目的探究适合于测定不同食品中总砷的前处理方法。方法分别采用干法消解、湿法消解、微波消解分别对不同类型样品进行前处理,食品中总砷含量依据GB/T5009.11—2014《食品中总砷及无机砷的测定》氢化物原子荧光法进行,通过计算回收率、精密度以及质控样品的准确性对测定结果进行分析和比较。结果对于大米这类成分简单的食品,干法消解、湿法消解、微波消解3种方式进行前处理结果相差不大,但微波消解法处理后结果准确度更好。对于有机砷的形态主要为砷糖和砷脂类的海产品,干灰化法消解后测得结果最接近于真值,微波和湿法消化存在消化不完全的问题。对于油炸食品,微波消解法准确度更好;湿法消解耗费试剂多,时间长;干法消化法操作容易起泡、飞溅,从而造成样品砷损失。结论不同消解方法在食品中总砷的测定过程中各有优缺点,要根据不同样品中砷形态来选择,对于砷形态比较复杂的食品,也可以利用不同的消解方式的优点相互结合的方式-混合消解法对样品进行前处理。     

乳与乳制品中总砷测定的不同前处理方法比较

目的比较不同前处理方法的处理效果,选择适合乳与乳制品中总砷测定的前处理方法。方法分别采用湿法消解、干法灰化、微波消解对乳与乳制品样品进行前处理,利用氢化物原子荧光法测定总砷含量。结果 3种前处理方式的检测结果均满足方法学要求,湿法消解、干法灰化和微波消解的回收率分别为81.7%～86.5%,90.0%～94.4%和90.8%～95.6%,精密度分别为8.84%～9.80%,3.22%～4.37%和3.18%～4.82%;检出限分别为0.0042、0.00068、0.0028mg/kg;微波消解法处理的质控样品结果更接近于标准值。结论微波消解法操作简便、准确性好,适合乳制品企业批量产品检测。     

石墨消解-微波消解法测定乳粉中总砷、总汞、铅和镉

目的建立石墨消解-微波消解法测定乳粉中的总砷、总汞、铅和镉含量的分析方法。方法样品经石墨加热预消解,采用微波消解法前处理,并采用电感耦合等离子体质谱法(inductively coupled plasma mass spectrometry,ICP-MS)测定乳粉中的总砷、总汞、铅和镉含量。结果总砷、总汞、铅和镉的平均加标回收率为94.4%?108.3%,精密度的相对标准差(relative standard deviation,RSD)为1.1%?4.6%,方法检出限分别为4.4、4.8、4.9、0.6?g/kg。乳粉质控样和考核样中总砷、总汞、铅和镉的测定结果均在参考值范围内,结果均为满意。结论该方法操作简便,重现性良好,测定结果准确、可靠,适用于乳粉中总砷、总汞、铅和镉的含量测定。     

不同前处理对原子荧光法测定海产品总砷的影响

对氢化物-原子荧光法测定海产品中总砷的前处理进行研究,探讨了微波消解、干法灰化、湿法消解、微波-湿法消解四种前处理方法对原子荧光法测定海产品中总砷结果的影响。实验证明不同的前处理方法对样品结果有很大影响:微波消解不适于海产品总砷的前处理,干法灰化不适用紫菜类植物性海产品的前处理,硝酸-高氯酸-硫酸体系的湿法消解、微波-湿法消解(加高氯酸、硫酸)可以作为一般海产品的前处理,且两种前处理的回收率均大于90%。     

微波消解-氢化物原子荧光光谱法测定大米中的总砷

针对《食品中总砷及无机砷的测定》GB 5009.11-2014对食品中总砷的测定方法进行了改进.根据国家标准GB 5009.11 2014总砷的测定中氢化物原子荧光光谱法,分别采用微波消解与湿法消解对质控样品和试样样品处理后进行总砷含量的测定.结果 表明:总砷在0～10.0 μg/L线性范围的相关系数为0.999 8,...     

不同前处理方法对火焰原子吸收光谱法测定饲料中铜含量的影响

目的通过比较不同的样品前处理方法,建立一种火焰原子吸收光谱法测定饲料中铜的含量。方法以饲料样品为原料,微波消解、湿法消解和干法灰化前处理方法分别对样品前处理后,采用火焰原子吸收光谱法测定饲料样品中铜的含量。结果 3种前处理方法测得的饲料中铜含量的加标回收率为92.0%~108%,在测定质控样品时,微波消解和湿法消解测定结果的相对标准偏差为1.3%~2.3%,符合要求;但干法灰化测定结果的相对标准偏差最大值为11.0%,超出标准范围。结论微波消解和湿法消解均能得到准确的检测结果,但湿法消解存在试剂消耗多、消解时间长等问题,而微波消解相对快速、准确、精密度高,更适合作为日常实验时饲料中铜的测定分析方法。     

比较微波消解-原子荧光法和电感耦合等离子体质谱法测定饲料中总砷

目的对比微波消解-原子荧光法和电感耦合等离子体质谱法测定饲料中总砷含量。方法采用微波消解作为样品前处理手段,原子荧光法和电感耦合等离子体质谱法作为检测方法,采用标准物质对两种方法进行验证。结果微波消解-原子荧光法检出限为0.006 mg/kg,线性相关系数为0.9998,相对标准偏差为6.3%和3.2%;微波消解-电感耦合等离子体质谱法检出限为0.003 mg/kg,线性相关系数为0.9999,相对标准偏差为2.4%和2.6%。2种方法对标准物质的测定结果均在标准值允许范围内。结论2种方法均操作简便快速,具有较低的检出限、较高的准确度和精密度,其中原子荧光法适合批量样品分析,电感耦合等离子体质谱法适用于总砷含量较高的样品。     

Effects of fatty acid supplements on ruminal and total tract nutrient digestion in lactating dairy cows

Saturated and unsaturated fatty acid supplements (FS) were evaluated for effects on ruminal digestion kinetics, and ruminal and postruminal nutrient digestion. Eight early lactation ruminally and duodenally cannulated cows (77 ± 12 days in milk, mean ± SD) were used in a replicated 4 × 4 Latin square design experiment with 21-d periods. Treatments were control and a linear substitution of 2.5% fatty acids from supplemented saturated FS (SAT; prilled, hydrogenated free fatty acids) for partially unsaturated FS (UNS; calcium soaps of long-chain fatty acids). All rations contained identical forage and concentrate components including 37.2% forage and 13.5% cottonseed. Saturated FS linearly decreased ruminal digestibility of dry matter and organic matter and linearly decreased ruminal neutral detergent fiber (NDF) digestibility. The reduction in ruminal NDF digestibility was because of a linear decrease in digestion rate and a linear increase in passage rate of potentially digestible NDF with increasing saturated FS. Total tract digestibility of NDF was not different between treatments because of compensatory postruminal digestion. Ruminal fatty acid and C18 fatty acid digestibility tended to increase linearly with increasing unsaturated FS, and postruminal C18 fatty acid digestibility decreased with increasing saturated FS. Saturated FS linearly decreased ruminal organic matter digestibility and decreased intestinal long-chain fatty acid digestibility, although differences in fatty acid digestibility may be partially explained by fatty acid intake.     

体外模拟消化技术研究进展

依据体外消化状态和消化部位的不同对体外模拟消化进行了分类、简述,对不同种类的体外模拟消化试验进行了总结分析,并列举了体外模拟消化在不同营养成分中的应用情况。     

麦草氧碱制浆及全无氯漂白

研究了麦草氧碱制浆的最佳工艺条件.结果表明,氧碱制浆可以在比常规烧碱-AQ法节碱35%左右,蒸煮最高温度120℃的条件下,取得64.8%的粗浆得率.对纸浆进行全无氯漂白的结果证明,采用合适的螯合剂和漂白活化剂可以漂至较高的白度.     

土壤中镉含量测定的前处理方法优化研究

利用标准土壤样品对比实际土壤样品,研究电热板消解法和微波消解法对测定土壤中镉元素的不同差异.将两种不同的土壤消解前处理方法以及结果进行分析比较,其中,电热板消解法根据消解状态不同又可分为两个批次,再针对不同消解方法的优缺点以及分析结果,确保推荐的消解预处理方法更加方便快捷、实用,结果更加准确、精密.通过以上测试结果发现...     

利用超高压液相色谱串联三重四级杆质谱定量 检测人乳中的α-乳白蛋白

目的 建立一种新型基于多肽标准品体系的母乳α-乳白蛋白的定量检测方法。方法 从母乳α-乳白蛋白筛选出特异性多肽,并建立对应的检测方法;利用化学方法人工合成特异性多肽、同位素标记特异性多肽和内标;通过方法学验证对该方法进行考察。结果 本方法所选择的多肽具有高度特异性,α-乳白蛋白的检测灵敏度分别为8.0 mg/100 g,精密度均<5.22 %,回收率均在97.21 – 102.45 %之间。结论 本方法建立了利用特异性多肽检测人α-乳白蛋白的方法,具有较高的准确度、灵敏度和稳定性。通过对447份母乳样品进行检测,初步探索了母乳中α-乳白蛋白的含量范围,为母乳化配方奶粉的华人配方奠定理论基础。     

Mechanisms of starch digestion by α-amylase—Structural basis for kinetic properties

Recent studies of the mechanisms determining the rate and extent of starch digestion by α-amylase are reviewed in the light of current widely-used classifications for (a) the proportions of rapidly-digestible (RDS), slowly-digestible (SDS), and resistant starch (RS) based on in vitro digestibility, and (b) the types of resistant starch (RS 1,2,3,4…) based on physical and/or chemical form. Based on methodological advances and new mechanistic insights, it is proposed that both classification systems should be modified.

Kinetic analysis of digestion profiles provides a robust set of parameters that should replace the classification of starch as a combination of RDS, SDS, and RS from a single enzyme digestion experiment. This should involve determination of the minimum number of kinetic processes needed to describe the full digestion profile, together with the proportion of starch involved in each process, and the kinetic properties of each process.

The current classification of resistant starch types as RS1,2,3,4 should be replaced by one which recognizes the essential kinetic nature of RS (enzyme digestion rate vs. small intestinal passage rate), and that there are two fundamental origins for resistance based on (i) rate-determining access/binding of enzyme to substrate and (ii) rate-determining conversion of substrate to product once bound.     

Effects of proanthocyanidins,dehulling and removal of pericarp on digestion of barley grain by ruminal micro‐organisms

The effects of proanthocyanidins (PA), dehulling, and removal of the pericarp on the rate and extent of barley digestion by ruminal micro‐organisms were studied using a control barley (cv Harrington) and three PA‐free barley lines (Caminant, Ca504316 and Ca802711). Each barley was studied in five preparations: whole grain (W); dehulled kernels (DH); kernels with pericarp removed (DP); dry‐rolled grain (DR), and the pericarp‐testa fraction (PT) produced during preparation of DP. Vanillin‐HCl staining and chemical analysis confirmed that PA were present only in the Harrington barley, and localised in the pericarp‐testa layer. Whole kernels, DH and DP were incubated with diluted ruminal fluid in vitro, and all five preparations were incubated in situ (nylon bag technique). Harrington DR and all four PT fractions were also incubated in vitro in the presence (0.074% w/v) and absence of polyethylene glycol (PEG), which specifically binds PA. The four barleys did not differ in in vitro dry matter disappearance (DMD) or gas production from W, DH or DP preparations, nor in in situ DMD rates from W, DH or DP (P > 0.05). In vitro DMD and gas production among PT fractions from the four barleys were also similar (P > 0.05), as were in vitro DMD from PEG‐present and PEG‐absent DR Harrington. With Harrington PT, in vitro ammonia concentrations were higher (P < 0.05) with PEG than without. For each barley line, in vitro DMD rates were highest (P < 0.01) with DP, followed by DH, and then by W (P < 0.01). In in situ incubations also, DMD rates and effective degradabilities of DR samples exceeded (P < 0.05) those of DH samples. It was concluded that the presence of proanthocyanidins did not affect ruminal digestion of barley grain, and that abrasive milling to breach the hull and pericarp may be a promising method by which to regulate the rate of barley digestion in the rumen. © Minister of Public Works and Government Services Canada 1999     

火焰原子吸收/发射光谱法对小麦粉中钠的检测

本文对钠元素在食品中的检测方法进行了简要比较,同时采用火焰原子吸收和火焰原子发射光谱法对国家标准物质小麦粉中的钠元素进行了检测,对前处理干法消化、湿法消化两种不同过程进行了比较,在两种前处理方法的称样量、消化时间、所用试剂、损失等方面进行了对比,找到两种方法各自的优缺点;同时本实验也对检测方法进行了比较,在前处理过程对结果无较大的影响,发射光谱法较吸收光谱法测得结果略微偏低。本文对于试验研究中,尤其是营养标签必测项Na元素的检测,选择何种前处理方法和检测方法具有一定参考价值。