作者感谢斯洛文尼亚研究机构的财政支持（批准号:P2-0414、P2-0118、J1-2470、NK-0001 和 J1-4416）。

1.样品均质化
<ol><li>使用干净的陶瓷刀，手动将食物样品（西兰花、蘑菇、香肠和面条）切成小块，以加快干燥过程。准备足够的样品进行至少6次酸消解重复（确保干燥样品的最小质量为1500mg）。 注意:增加样品的表面积会使样品的更大一部分暴露在加热的周围空气中，从而增加水的蒸发速度。</li>
	<li>将样品放入250mL玻璃烧杯中，并使用干燥器在105°C下干燥至恒重。</li>
	<li>从干燥器中取出装有样品的玻璃烧杯，然后将其插入干燥器中。</li>
	<li>让样品冷却至室温。 注意:样品必须在恒温下称重，以确保砝码准确反映质量。温度变化会影响被测样品的体积和密度。</li>
	<li>打开干燥器，将玻璃烧杯和样品放在分析天平上。用样品测量玻璃烧杯的重量。</li>
	<li>称量完成后，将样品放回干燥机中。 注意:如果样品在干燥过程中明显收缩，可以使用塑料刮刀将其转移到较小的玻璃烧杯中，以便更方便地称量。</li>
	<li>重复步骤1.3-1.6中描述的过程，直到样品达到恒定重量。</li>
	<li>将干燥的异质样品放入混合烧杯中（参见 材料表），确保其不超过混合烧杯的最大体积。</li>
	<li>将搅拌杯插入搅拌器并关闭防护门（图 1）。</li>
	<li>按 下开始 按钮激活用于研磨和混合样品的刀片。</li>
	<li>进行研磨，直到样品变成细粉或均匀的糊状物。要获得这样的产品，请重复研磨过程几次。</li>
	<li>当样品均质化后，关闭混合器，打开防护门，取出混合器烧杯。</li>
	<li>从混合烧杯中取出匀浆样品，并使用干净的塑料刮刀将其转移到干净的 50 mL 玻璃烧杯中（图 2）。 注意: 如果样品太硬并且可能会损坏混合器的组件，例如刀片和混合烧杯，则可以通过其他方法对其进行均质化，例如在研钵中粉碎。混合器通常不适合均质硬质材料、冷冻样品或易燃样品，这可能会损坏混合器的组件。不鼓励在混合器中使用有机溶剂。 注意: 使用安全装备并确保当搅拌机的叶片高速旋转时，搅拌机的门已充分关闭。</li>
</ol>2.搅拌机清洗
<ol><li>将超纯水（见 材料表）添加到空混合烧杯的标记中。</li>
	<li>将搅拌杯插入搅拌杯并执行标准混合程序。</li>
	<li>将烧杯从搅拌机中取出，倒出废水。如有必要，用超纯水重复该过程数次，直到混合后水仍然保持清洁。</li>
	<li>从搅拌机上取下受污染的叶片和隔膜密封件，并用超纯水彻底清洁。 注意:使用中性清洁剂可提高清洁效率，尤其是在处理脂肪含量高的样品时，因为脂肪很容易粘附在实验室库存的表面。 注意: 拆卸和清洁刀片时，请穿戴适当的防护设备，例如手套，以降低锋利边缘可能造成伤害的风险。</li>
	<li>在105°C下干燥后的组件，然后将它们重新插入混合器中。 注意: 在将混合器的组件重新安装到混合器中之前，请确保它们完全干燥，以防止水残留到下一个样品中。</li>
</ol>3.样品称量
<ol><li>从 100 mL 三氟甲氧基-聚四氟乙烯 TFM-PTFE 反应容器33 上取下盖。</li>
	<li>将打开的反应容器放在分析天平上，并确保天平在每次测量前均处于水平状态并归零（图3）。 注意:称重必须在室温下进行。避开剧烈的温度波动和气流可能影响测量重量的区域。确保称重区域清洁且没有任何污染物。</li>
	<li>使用塑料刮刀将匀浆样品转移到反应容器中，并称取250mg样品。不要将样品称量到低于分析天平的最小称量限值。</li>
	<li>称量完成后，将盖放在反应容器上，以保护样品免受污染。 注意:超过消解过程的重量限制会导致消解不完全。小心处理样品和反应容器，以避免任何外部污染。</li>
</ol>4.加酸
<ol><li>将约 40.0 mL 68 wt% HNO3 和 5.0 mL 30 wt% H2O2 分别倒入单独的 50 mL 玻璃烧杯中。 注意:化学品必须是高纯度的，痕量金属杂质小于 1.0 μg/L （ppb），理想情况下在 ng/L （ppt） 范围内。痕量金属杂质会影响元素测定的准确性和可重复性。</li>
	<li>将反应容器置于通风橱中，打开盖盖，然后根据以下规格，用 1 mL 或 5 mL 自动移液器加入下述体积的 68 wt% HNO3 和 30 wt% H2O2 :<ol><li>西兰花、蘑菇、香肠和面条;对于 250 mg 样品，加入 5.0 mL 68 wt% HNO3 和 1.0 mL 30 wt% H2O2。为每个样品准备三个重复。</li>
		<li>为了确定方法的准确性（就回收率而言，Rec），使用步骤4.2.1中描述的程序，并使用200μL自动移液器向反应容器中加入37.5μL 100 mg/L ICP多元素标准溶液（参见 材料表）。对于每个样品，准备三个重复。 注:选择37.5μL的体积，因为它对应于样品的加标溶液与样品的非加标溶液中的浓度相比增加了15.0μg/ L。此外，样品加标溶液浓度的增加对应于所测量的每种分析物仍处于线性浓度范围内的最终浓度。</li>
		<li>使用与步骤4.2.1中用于消解食品样品的相同体积的68wt% HNO3 和30wt% H2O2 制备样品空白。对于样品空白，请勿将样品添加到反应容器中。 注意: 用于消解的 HNO3 具有腐蚀性并产生烟雾。因此，必须在通风橱中添加酸。必须使用标准的实验室防护设备（手套、护目镜和实验室外套）。如果与酸接触，应立即用冷水冲洗患处，并寻求医疗帮助。</li>
	</ol></li>
	<li>将盖盖放在反应容器上，让样品与添加的 68 wt% HNO3 和 30 wt% H2O2 反应 2-3 分钟。</li>
	<li>拧紧容器上的螺纹盖并拧紧盖盖。</li>
	<li>使用轻微的手部动作摇晃反应容器，将样品完全掺入化学品中。 注意:不要将样品留在反应容器的壁或盖子上，因为它们可能无法完全消化。</li>
</ol>5. 微波辅助湿酸消解
<ol><li>按下启动按钮打开微波系统（参见材料表）进行酸消解（图 4）。</li>
	<li>打开微波炉门并取下架子。</li>
	<li>将封闭的反应容器对称地分布在架子上，以确保微波均匀照射样品。</li>
	<li>将机架插入微波室并将其安装在支架上（图 5）。</li>
	<li>关闭微波炉门。</li>
	<li>使用笔形工具在微波炉触摸屏上设置合适的消解程序。选择合适的温度梯度、最终温度和要消解的样品数量。下面列出了针对不同食物样本的推荐消解程序:<ol><li>西兰花、蘑菇、香肠和面条:增加 10 分钟至 160 °C，增加 10 分钟至 200 °C，200 °C 下增加 15 分钟，最大功率 900 W。</li>
	</ol></li>
	<li>启动消解程序并在屏幕上监控反应条件的变化。如果温度没有按照规定的程序升高，请停止消化过程。 注意: 在消化过程中，微波炉屏幕上可能会突然出现温度峰值。当样品与化学物质发生放热反应时，就会发生它们。微波系统将通过调节输出功率自动调节温度。</li>
	<li>等到微波辅助消解完成，样品温度降低。</li>
	<li>打开微波炉门，从微波炉腔中取出架子。关上门并关闭仪器。</li>
	<li>从架子上取下反应容器，等待它们冷却至室温。</li>
	<li>手动慢慢打开盖盖以释放酸消解过程中形成的气体。将反应容器朝通风橱的方向转动（图6）。</li>
	<li>完全取下盖子，用少量超纯水冲洗盖子和反应容器壁。</li>
	<li>通过用超纯水反复冲洗盖子和反应容器，通过玻璃漏斗将反应容器的内容物定量转移到干净的 25 mL 玻璃容量瓶中。</li>
	<li>用超纯水将样品稀释至容量瓶的标记。用塞子关闭容量瓶并混合容量瓶的内容物。 注意:应用超纯水进一步稀释消解样品，因为它们应含有少于 5% （V/V） 的残余酸34 和少于 2 g/L 的溶解元素，也称为总溶解固体35。</li>
	<li>取一个 20 mL 塑料注射器，并将其与聚酰胺注射器过滤器（直径 25 mm，孔径 0.20 μm）连接。用稀释的样品填充塑料注射器，并通过施加压力将其内容物过滤到 50 mL 塑料离心管中。对每个样品使用新的塑料注射器和注射器过滤器，以避免任何交叉污染。 注意:样品需要过滤以去除任何不溶性物质或固体颗粒，这些物质或固体颗粒在 MAWD 后可能仍未消化。这些颗粒可能会堵塞仪器组件，从而干扰元素测定测量。过滤样品时，确保丢弃前几滴。使用亲水过滤器（由聚酰胺制成）处理水溶液。疏水过滤器（PTFE）不适合过滤水溶液，因为它们需要更高的施加压力，这可能导致膜破裂36。</li>
	<li>用螺旋盖关闭 50 mL 塑料离心管，将样品放入冰箱直至测量。 注意:消解后的样品在较低的温度下储存在冰箱中，以保存它们并延长其储存时间。</li>
</ol>6.反应容器清洗
<ol><li>将消化后的样品转移到 50 mL 容量瓶中后，用 5 mL 自动移液器向反应容器中加入 5.0 mL 68 wt% HNO3 和 5.0 mL 超纯水。</li>
	<li>用盖关闭反应容器并将其插入架子中。将架子转移到微波炉室。</li>
	<li>应用以下微波程序:15 分钟增加到 160 °C，10 分钟增加到 180 °C，最大功率 900 W。</li>
	<li>监测加热过程中的反应条件。加热完成后，让反应容器冷却。</li>
	<li>打开微波炉，从架子上取下反应容器，然后在通风橱中慢慢打开它们。</li>
	<li>将反应容器的内容物丢弃到塑料废物容器中。</li>
	<li>用超纯水冲洗反应容器，以去除多余的材料或化学物质。</li>
	<li>在下次使用之前，在干燥器中以105°C干燥反应容器。 注意:用于样品酸消解的相同微波程序（时间、功率、温度梯度和化学品体积）可用于清洁反应容器。或者，可以在没有微波系统的情况下清洁反应容器，方法是将反应容器浸没在浓HNO3 或HCl中数小时，然后用超纯水冲洗。</li>
</ol>7. 使用ICP-MS进行多元素测定
<ol><li>从冰箱中取出装有消解样品的 50 mL 塑料离心管，让它们加热至室温。</li>
	<li>将样品稀释10倍，以降低消解样品中的酸浓度并降低样品基质组分的浓度。使用自动移液器，将 2.50 mL 样品转移到 25 mL 玻璃容量瓶中，然后用超纯水将其填充至标记处。</li>
	<li>将稀释的样品转移到 15 mL 塑料管中，并将其置于自动进样器中的适当位置。</li>
	<li>准备 ICP-MS 仪器（见 材料表）进行测量:<ol><li>打开通风和冷却器，为 ICP-MS 提供冷却水并冷却其组件。</li>
		<li>使用兼容的软件确保冲洗液（1 wt% HNO3）连续从自动进样器流向 ICP-MS，而不会产生脉动。</li>
		<li>打开氩气（纯度为99.999%）和氦气（纯度为99.999%）气瓶，为ICP-MS提供两种气体。检查软件中的气体流量，并在必要时进行调整。 注意:当由于多原子离子的形成（例如， 40Ar16O+ 干扰 56Fe+）37 预计会出现光谱干扰时，请使用带有 He 气体的碰撞池。</li>
		<li>启动等离子体并使用调谐溶液校准仪器（参见 材料表）。</li>
		<li>校准仪器（割炬位置、增益电压、透镜电压、质量/分辨率、脉冲/模拟 （P/A） 校准、数据库 （DB） 校准和验证）后，选择所需的测量方法并执行测量。</li>
	</ol></li>
	<li>使用未知样品时，进行半定量测定，以获取有关样品中存在哪些元素及其大致浓度的信息。 注意:建议额外稀释样品以进行半定量测定，因为检测器一次可以检测到的元素浓度有限。较低的样品浓度可以延长仪器组件的使用寿命。</li>
	<li>在获得样品中元素的近似浓度数据后，在软件中创建定量元素测定方法。选择ICP-MS的工作条件（表1）并选择所需的元素（在本例中为Cu、Fe、Mn和Zn）。确定创建校准曲线（有时称为分析曲线或工作曲线）所需的标准溶液的数量和浓度（表1）。 注意:准备至少六种不同的浓度作为校准曲线的校准点。</li>
	<li>为校准曲线准备标准溶液。使用自动移液器，将所需体积的100 mg/L多元素标准溶液移液到25 mL玻璃容量瓶中，以制备具有以下浓度的标准品溶液:1.0 μg/L、2.5 μg/L、5.0 μg/L、10.0 μg/L、20.0 μg/L、30.0 μg/L、40.0 μg/L和50.0 μg/L。此外，使用 1 wt% HNO3 溶液制备校准空白。</li>
	<li>将制备的标准品溶液和样品转移到 15 mL 塑料管中，将它们放入自动进样器中，然后按照步骤 7.4 中描述的程序启动仪器。</li>
	<li>使用校准曲线方法对所选元素进行定量测量。</li>
	<li>测量完成后，关闭等离子体，关闭氩气和氦气供应，关闭 ICP-MS 冷水机组，并关闭通风系统。</li>
</ol>

用于多元素分析的食品样品均质化和消解

作者没有什么可透露的。

均匀 为了确保元素测定结果的可重复性，由于样品的结构和组成复杂且不均匀，因此有必要在酸消解之前对样品进行均质化。同质化旨在消除宪法和分配的异质性。混合样品通过在整个样品中均匀地重新分配组分来最大限度地减少分布异质性。同样，通过将粒径降低到均匀的尺寸，可以减少结构异质性44。从匀浆中获得的子样品必须包含与原始样品相同的组分比?...

元素分析是确定各种样品元素组成的分析过程。它可用于控制人体中金属（尤其是重金属1）的摄入量，因为它们的高浓度可能会导致不必要的健康问题。重金属也是主要的环境污染物之一，因此，控制它们在环境中的存在是必要的2.此外，元素分析可用于确定食品的地理来源3 ，并控制食物和水资源的质量4。此外，它还用于测定土壤中的微量和宏量营养素5 ，并通过检查矿物和沉积物的化学成分6 来深入了解整个历史的地质过程。还进行了研究，以确定电气和电子废物中稀有金属的存在，以便进一步进行金属再生7，评估药物治疗的成功8，并验证金属植入物的元素组成9。
电感耦合等离子体质谱法 （ICP-MS） 和电感耦合等离子体发射光谱法 （ICP-OES） 是用于各种样品元素分析的常用技术10。它们可以同时测定多种元素，检测限 （LOD） 和定量限 （LOQ） 低至 ng/L。一般来说，与 ICP-OES12 相比，ICP-MS 具有更低的 LOD 值11 和更宽的线性浓度范围。测定元素组成的其他技术是微波诱导等离子体发射光谱法13和原子吸收光谱法（AAS）的几种变体，包括火焰原子吸收光谱法、电热原子吸收光谱法2、冷蒸气原子吸收光谱法和氢化物产生原子吸收光谱法14.此外，使用不同的电分析方法可以进行低LOD和LOQ的元素测定，特别是阳极剥离伏安法15,16。当然，还有其他方法可以确定样品的元素组成，但它们不像上述方法那样经常使用。
使用激光诱导击穿光谱和 X 射线荧光17 对固体样品进行直接元素测定是可行的。然而，对于使用 ICP-MS、ICP-OES 和 AAS 进行元素测定，必须将固体样品转化为液态。为此，使用酸和辅助试剂（在大多数情况下是H2O2）进行酸消解。酸消解在高温和高压下进行，将样品的有机部分转化为气态产物，并将金属元素转化为水溶性盐，从而将它们溶解在溶液中18。
酸消解主要有两种类型，开血管消解和闭合容器消解。开式容器消解具有成本效益14 ，但有局限性，例如最高消解温度，它与常压下酸的沸腾温度一致。样品可以在热板、加热块、水浴、砂浴2和微波19上加热。通过以这种方式加热样品，产生的大部分热量会损失到周围环境20中，从而延长消解时间14。开式容器消解的其他缺点包括更大的化学品消耗量，来自周围环境的污染的可能性更大，以及由于挥发性组分的形成及其从反应混合物中蒸发而可能损失分析物21。
与开放式容器系统相比，封闭容器系统更便于有机和无机样品的消解。密闭容器系统利用各种能源来加热样品，例如传导加热和微波22。使用微波的消解方法包括微波诱导燃烧23、单反应室系统24和常用的微波辅助湿酸消解（MAWD）25,26。MAWD 允许在更高的工作温度下进行消解，范围在 220 °C 和 260 °C 之间，最大压力高达 200 bar，具体取决于仪器的工作条件27。
MAWD的效率和速率取决于几个因素，包括样品的化学成分，最高温度，温度梯度，反应容器中的压力，添加的酸的量和所用酸的浓度28。在 MAWD 中，由于与开放式容器系统中更持久的消解相比，反应条件升高，可以在几分钟内实现完全的酸消解。MAWD 中需要较低的酸的体积和浓度，这符合当前的绿色化学指南29。在MAWD中，与开血管消解相比，需要较少量的样品进行酸消解，通常高达500mg的样品就足够了30,31,32。可以消化较大数量的样品，但它们需要更多的化学品。
由于 MAWD 仪器自动控制反应条件，并且人在加热过程中不会直接接触化学品，因此 MAWD 比开放式容器消解更安全。但是，在向反应容器中添加化学物质时，该人应始终谨慎行事，以防止它们与身体接触并造成伤害。反应容器也需要缓慢打开，因为在酸消解过程中，反应容器内部的压力会积聚。
虽然酸消解是制备用于元素测定的样品的有用技术，但执行该技术的人员应了解其可能的局限性。酸消解可能并不适合所有样品，尤其是那些具有复杂基质的样品以及那些反应性高或可能发生爆炸反应的样品。因此，应始终评估样品成分，以选择适当的化学品和反应条件，以便完全消解，从而溶解溶解溶液中所有所需元素。用户必须考虑并解决的其他问题是样品制备过程中每一步的杂质和分析物损失。酸消解必须始终按照特定规则或使用方案进行。
下面描述的方案提供了在实验室大小的混合器中对食品样品进行均质化的说明，清洁混合器组件、正确称量样品、添加化学品、通过 MAWD 进行酸消解、在消解完成后清洁反应容器、制备样品进行元素测定以及使用 ICP-MS 进行定量多元素测定的程序。按照以下说明，应该能够制备适合元素测定的样品并对消解样品进行测量。

<table><tbody><tr><td>Ar gas</td><td>Messer</td><td>7440-37-1</td><td>Ar 5.0 gas (purity 99.999%).</td></tr><tr><td>AS-10 Autosampler system</td><td>Shimadzu</td><td></td><td>Autosampler connected to the ICP-MS, containing 68 ports for samples.</td></tr><tr><td>Automatic pipettes</td><td>Sartorius</td><td></td><td>200 &amp;micro;L, 1 mL, and 5 mL automatic pipettes.</td></tr><tr><td>Balance XSE104</td><td>Mettler Toledo, Columbus, Ohio, USA</td><td></td><td>Analytical balance scale with a maximum weighing mass of 120 g.</td></tr><tr><td>Ceramic knife</td><td></td><td></td><td>Ceramic knife used for cutting fresh food samples.</td></tr><tr><td>Dessicator</td><td></td><td></td><td>Glass desiccator with lumps of silica gel.</td></tr><tr><td>ETHOS LEAN</td><td>Milestone, Sorisole, Italy</td><td></td><td>Microwave system for wet acid digestion in closed 100 mL vessels made of TFM-PTFE.</td></tr><tr><td>Fume hood</td><td></td><td></td><td>Laboratory fume hood with adjustable air flow.</td></tr><tr><td>Glass beakers RASOTHERM</td><td>CarlRoth GmbH + Co.KG</td><td></td><td>50 mL, 250 mL glass beakers</td></tr><tr><td>Glass funnels</td><td></td><td></td><td>Small glass funnels fitting into the neck of volumetric flasks.</td></tr><tr><td>He gas</td><td>Messer</td><td>7440-59-7</td><td>He 5.0 gas (purity 99.999%).</td></tr><tr><td>Hydrogen peroxide</td><td>ThermoFisher Scientific</td><td>7722-84-1</td><td>Hxdrogen peroxide 100 volumes 30 wt.% solution. Laboratory reagent grade.</td></tr><tr><td>ICP multi-element standard solution VIII</td><td>Supelco</td><td>109492</td><td>100 mg/L ICP multi-element standard solution containing 24 elements (Al, B, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, K, Li, Mg, Mn, Na, Ni, Pb, Se, Sr, Te, Tl, Zn) in 2 % dilute nitric acid.</td></tr><tr><td>ICPMS 2030</td><td>Shimadzu</td><td></td><td>Inductively coupled plasma mass spectrometry system for multi-element analysis of digested samples.</td></tr><tr><td>ICP-MS Tuning Solution A</td><td>CarlRoth GmbH + Co.KG</td><td></td><td>250 mL tuning solution containing 6 elements (Be, Bi, Ce, Co, In, Mn) in 1 % nitric acid.</td></tr><tr><td>KIMTECH Purple Nitrile gloves</td><td>Kimberly-Clark GmbH</td><td></td><td>Disposable Purple Nitrile gloves (S, M or L).</td></tr><tr><td>Laboratory coat</td><td>Any available supplier</td><td></td><td>/</td></tr><tr><td>Mixer B-400</td><td>B&amp;Uuml;CHI Labortechnik AG, Flawil, Switzerland</td><td></td><td>Laboratory mixer with ceramic blades.</td></tr><tr><td>Nitric acid</td><td>ThermoFisher Scientific</td><td>7697-37-2</td><td>Nitric acid, trace analysis grade, 68 wt%, density 1.42, Primar Plus, For Trace Metal Analysis.</td></tr><tr><td>Plastic centrifuge tubes</td><td>Isolab</td><td></td><td>50 mL plastic centrifuge tubes with screw caps, single use.</td></tr><tr><td>Plastic syringes Injekt</td><td>B. Braun</td><td></td><td>2 pice, single use 20 mL syringes.</td></tr><tr><td>Plastic tubes for autosampler</td><td>Shimadzu</td><td>046-00147-04</td><td>Plastic tubes for autosampler, 15 mL capacity, 16 mm diameter, 100 mm length.</td></tr><tr><td>Plastic waste containers</td><td></td><td></td><td>Plastic containers for the removal of chemicals after the cleaning procedure of reaction vessels.</td></tr><tr><td>Protective googles</td><td></td><td></td><td>/</td></tr><tr><td>Samples (broccoli, sausage, noodles, zucchini, mushrooms)</td><td></td><td></td><td>Fresh samples, which were dried to a constant weight and homogenized during the procedure. The samples were purchased from a local shop.</td></tr><tr><td>Spatula</td><td></td><td></td><td>Plastic spatula.</td></tr><tr><td>Sterilizator Instrumentaria ST 01/02</td><td>Instrumentaria</td><td></td><td>Dryer with adjustable temperature.</td></tr><tr><td>Syringe filters</td><td>CHROMAFIL Xtra</td><td>729212</td><td>Syringe filters with polypropylene housing and polyamide hydrophilic membrane. Membrane diameter 25 mm, membrane pore size 0.2 &amp;micro;m.</td></tr><tr><td>Ultrapure water</td><td>ELGA Labwater, Veolia Water Technologies.</td><td></td><td>Ultrapure water with a resistivity of 18.2 M&amp;Omega;cm, obtained with laboratory water purification system.</td></tr><tr><td>Volumetric flasks</td><td></td><td></td><td>25 mL glass volumetric flasks.</td></tr></tbody></table>

preparation of food samples using homogenization and microwave-assisted wet acid digestion for multi-element determination with icp-ms

样品制备对于元素测定至关重要，并且有多种技术可供选择，其中一种技术涉及均质化，然后是酸消解。在制备阶段的样品处理过程中需要特别小心，以消除或尽量减少潜在的污染和分析物损失。均质化是一种同时减小粒径和均匀分布样品组分的过程。均质化后，样品进行酸消解，其中在高温下用酸和辅助化学品消解，将固体样品转化为液态。在这个过程中，原始样品中的金属与酸反应形成水溶性盐。通过酸消解制备的样品适用于使用电感耦合等离子体质谱法、电感耦合等离子体发射光谱法、原子吸收光谱法、电化学方法和其他分析技术进行元素分析。这项工作详细介绍了使用电感耦合等离子体质谱法制备用于多元素测定的食品样品。分步程序包括使用带有陶瓷刀片的实验室大小的混合器进行均质化过程，然后使用微波辅助湿酸消解在密闭容器中进行酸消解。5.0 mL 68 wt% HNO3 和 1.0 mL 30 wt% H2O2 的混合物用作辅助试剂。本指南对这两个阶段所涉及的过程进行了说明。

均匀 所有样品均用实验室干燥器干燥至恒定质量，以消除任何水分。将样品转移到干燥器中，使其冷却至室温，而不会结合周围环境的水分。然后使用实验室混合器将食品样品均质化，以获得细粉。所得均质颗粒大小均匀，分布均匀，确保用于酸消解的子样品（从较大样品中抽取的样品）具有代表性。在塑料刮刀的帮助下，样品很容易从混合烧杯中取出，但干肉样品除外，由于其?...

Watch this Scientific Journal Video about Author Spotlight: Technologies and Challenges in Elemental Analysis of Food Samples at JoVE.com

作者聚焦:食品样品元素分析的技术和挑战

所提出的方案描述了使用实验室混合器进行样品均质化，通过微波辅助湿酸消解使用68wt%HNO3和30wt%H2O2的混合物对食品样品进行酸消解，以及使用电感耦合等离子体质谱法进行多元素测定。

使用均质化和微波辅助湿酸消解制备食品样品，用于ICP-MS多元素测定

Sample preparation is crucial for elemental determination, and various techniques are available, one of which involves homogenization followed by acid ...

我们的研究旨在使用不同的光谱设备来确定不同食品样品的元素组成，例如控制食品样品的质量。除了ICP-MS之外，我们的实验室还可以使用ICP-OES、原子吸收光谱和离子色谱法对消化的食物样品进行元素分析。然而，我们也可以使用X射线光电子能谱和飞行时间二次离子质谱法进行元素分析。我们目前面临的实验挑战主要集中在样品制备过程中。我们的目标是提高样品通量并优化清洁程序，以尽量减少样品的任何残留。本文中的信息是关于样品均质化、酸消解和元素分析的，以便更好地了解样品制备和后续分析的关键程序，同时我们重点介绍了整个过程的重要步骤、建议和局限性。我们将专注于蔬菜、葡萄酒、冰淇淋、电子液体等样品的整个过程的优化，未来甚至包括需要不同样品制备技术的无机样品。

preparation-food-samples-using-homogenization-microwave-assisted-wet

Research

JoVE Journal

Chemistry

Preparation of Food Samples Using Homogenization and Microwave-Assisted Wet Acid Digestion for Multi-Element Determination with ICP-MS

2.1K 次观看.  University of Maribor. 我们的研究旨在使用不同的光谱设备来确定不同食品样品的元素组成，例如控制食品样品的质量。除了ICP-MS之外，我们的实验室还可以使用ICP-OES、原子吸收光谱和离子色谱法对消化的食物样品进行元素分析。然而，我们也可以使用X射线光电子能谱和飞行时间二次离子质谱法进行元素分析。我们目前面临的实验挑战主要集中在样品制备过程中。我们的目标是提高样品通?...

视频: 作者聚焦:食品样品元素分析的技术和挑战

Preparation of Homogeneous MALDI Samples for Quantitative Applications

This protocol demonstrates a simple sample preparation to reduce spatial heterogeneity in ion signals during matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. The heterogeneity of ion signals is a severe problem in MALDI, which results in poor data reproducibility and makes MALDI unsuitable for quantitative analysis. By regulating sample plate temperature during sample preparation, thermal-induced hydrodynamic flows inside droplets of sample solution are able to reduce the heterogeneity problem. A room-temperature sample preparation chamber equipped with a temperature-regulated copper base block that holds MALDI sample plates facilitates precise control of the sample drying condition. After drying of sample droplets, the temperature of sample plates is returned to room temperature and removed from the chamber for subsequent mass spectrometric analysis. The areas of samples are examined with MALDI-imaging mass spectrometry to obtain the spatial distribution of all components in the sample. In comparison with the conventional dried-droplet method that prepares samples under ambient conditions without temperature control, the samples prepared with the method demonstrated herein show significantly better spatial distribution and signal intensity. According to observations using carbohydrate and peptide samples, decreasing substrate temperature while maintaining the surroundings at ambient temperature during the drying process can effectively reduce the heterogeneity of ion signals. This method is generally applicable to various combinations of samples and matrices.

A protocol for reducing spatial heterogeneities of ion signals in MALDI mass spectrometry by regulating substrate temperature during sample drying processes is demonstrated.

定量应用同质MALDI样品的制备

This protocol demonstrates a simple sample preparation to reduce spatial heterogeneity in ion signals during matrix-assisted laser desorption/ionization ...

科研

生物化学

Microwave-assisted Intramolecular Dehydrogenative Diels-Alder Reactions for the Synthesis of Functionalized Naphthalenes/Solvatochromic Dyes

Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to the preparation of new organic dyes. Although numerous strategies have been reported to access naphthalene scaffolds, many procedures still present limitations in terms of incorporating functionality, which in turn narrows the range of available substrates. The development of versatile methods for direct access to substituted naphthalenes is therefore highly desirable.
The Diels-Alder (DA) cycloaddition reaction is a powerful and attractive method for the formation of saturated and unsaturated ring systems from readily available starting materials. A new microwave-assisted intramolecular dehydrogenative DA reaction of styrenyl derivatives described herein generates a variety of functionalized cyclopenta[b]naphthalenes that could not be prepared using existing synthetic methods. When compared to conventional heating, microwave irradiation accelerates reaction rates, enhances yields, and limits the formation of undesired byproducts.
The utility of this protocol is further demonstrated by the conversion of a DA cycloadduct into a novel solvatochromic fluorescent dye via a Buchwald-Hartwig palladium-catalyzed cross-coupling reaction. Fluorescence spectroscopy, as an informative and sensitive analytical technique, plays a key role in research fields including environmental science, medicine, pharmacology, and cellular biology. Access to a variety of new organic fluorophores provided by the microwave-assisted dehydrogenative DA reaction allows for further advancement in these fields.

Microwave-assisted intramolecular dehydrogenative Diels-Alder (DA) reactions provide concise access to functionalized cyclopenta[b]naphthalene building blocks. The utility of this methodology is demonstrated by one-step conversion of the dehydrogenative DA cycloadducts into novel solvatochromic fluorescent dyes via Buchwald-Hartwig palladium-catalyzed cross-coupling reactions.

微波辅助分子内Diels-Alder反应的功能化萘/变色染料的合成脱氢

Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to ...

化学

Microwave-assisted Functionalization of Poly(ethylene glycol) and On-resin Peptides for Use in Chain Polymerizations and Hydrogel Formation

One of the main benefits to using poly(ethylene glycol) (PEG) macromers in hydrogel formation is synthetic versatility. The ability to draw from a large variety of PEG molecular weights and configurations (arm number, arm length, and branching pattern) affords researchers tight control over resulting hydrogel structures and properties, including Young&#8217;s modulus and mesh size. This video will illustrate a rapid, efficient, solvent-free, microwave-assisted method to methacrylate PEG precursors into poly(ethylene glycol) dimethacrylate (PEGDM). This synthetic method provides much-needed starting materials for applications in drug delivery and regenerative medicine. The demonstrated method is superior to traditional methacrylation methods as it is significantly faster and simpler, as well as more economical and environmentally friendly, using smaller amounts of reagents and solvents. We will also demonstrate an adaptation of this technique for on-resin methacrylamide functionalization of peptides. This on-resin method allows the N-terminus of peptides to be functionalized with methacrylamide groups prior to deprotection and cleavage from resin. This allows for selective addition of methacrylamide groups to the N-termini of the peptides while amino acids with reactive side groups (e.g.&#160;primary amine of lysine, primary alcohol of serine, secondary alcohols of threonine, and phenol of tyrosine) remain protected, preventing functionalization at multiple sites. This article will detail common analytical methods (proton Nuclear Magnetic Resonance spectroscopy (;H-NMR) and Matrix Assisted Laser Desorption Ionization Time of Flight mass spectrometry (MALDI-ToF)) to assess the efficiency of the functionalizations. Common pitfalls and suggested troubleshooting methods will be addressed, as will modifications of the technique which can be used to further tune macromer functionality and resulting hydrogel physical and chemical properties. Use of synthesized products for the formation of hydrogels for drug delivery and cell-material interaction studies will be demonstrated, with particular attention paid to modifying hydrogel composition to affect mesh size, controlling hydrogel stiffness and drug release.

Microwave-assisted Functionalization of Polyethylene glycol and On-resin Peptides for Use in Chain Polymerizations and Hydrogel Formation

This video will illustrate a rapid, efficient method to methacrylate poly(ethylene glycol), enabling chain polymerizations and hydrogel synthesis. It will demonstrate how to similarly introduce methacrylamide functionalities into peptides, detail common analytical methods to assess functionalization efficiency, provide suggestions for troubleshooting and advanced modifications, and demonstrate typical hydrogel characterization techniques.

保利的微波辅助功能化（乙二醇）和On-树脂链聚合反应，并形成水凝胶的肽使用

One of the main benefits to using poly(ethylene glycol) (PEG) macromers in hydrogel formation is synthetic versatility. The ability to draw from a large ...

Quantification of Heavy Metals and Other Inorganic Contaminants on the Productivity of Microalgae

Increasing demand for renewable fuels has researchers investigating the feasibility of alternative feedstocks, such as microalgae. Inherent advantages include high potential yield, use of non-arable land and integration with waste streams. The nutrient requirements of a large-scale microalgae production system will require the coupling of cultivation systems with industrial waste resources, such as carbon dioxide from flue gas and nutrients from wastewater. Inorganic contaminants present in these wastes can potentially lead to bioaccumulation in microalgal biomass negatively impact productivity and limiting end use. This study focuses on the experimental evaluation of the impact and the fate of 14 inorganic contaminants (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Sb, Se, Sn, V and Zn) on Nannochloropsis salina growth. Microalgae were cultivated in photobioreactors illuminated at 984 &#181;mol m-2 sec-1 and maintained at pH 7 in a growth media polluted with inorganic contaminants at levels expected based on the composition found in commercial coal flue gas systems. Contaminants present in the biomass and the medium at the end of a 7 day growth period were analytically quantified through cold vapor atomic absorption spectrometry for Hg and through inductively coupled plasma mass spectrometry for As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sb, Se, Sn, V and Zn. Results show N. salina is a sensitive strain to the multi-metal environment with a statistical decrease in biomass yieldwith the introduction of these contaminants. The techniques presented here are adequate for quantifying algal growth and determining the fate of inorganic contaminants.

Integration of microalgal cultivation with industrial flue gas will ultimately introduce heavy metals and other inorganic compounds into the growth media. This study presents a procedure used to determine the end fate and impact of heavy metals and inorganic contaminants on the growth of Nannochloropsis salina grown in photobioreactors.

重金属和微藻的产其他无机污染物的量化

Increasing demand for renewable fuels has researchers investigating the feasibility of alternative feedstocks, such as microalgae. Inherent advantages ...

环境科学

Clean Sampling and Analysis of River and Estuarine Waters for Trace Metal Studies

Most of the trace metal concentrations in ambient waters obtained a few decades ago have been considered unreliable owing to the lack of contamination control. Developments of some techniques aiming to reduce trace metal contamination in the last couple of decades have resulted in concentrations reported now being orders of magnitude lower than those in the past. These low concentrations often necessitate preconcentration of water samples prior to instrumental analysis of samples. Since contamination can appear in all phases of trace metal analyses, including sample collection (and during preparation of sampling containers), storage and handling, pretreatments, and instrumental analysis, specific care needs to be taken in order to reduce contamination levels at all steps. The effort to develop and utilize "clean techniques" in trace metal studies allows scientists to investigate trace metal distributions and chemical and biological behavior in greater details. This advancement also provides the required accuracy and precision of trace metal data allowing for environmental conditions to be related to trace metal concentrations in aquatic environments.
This protocol that is presented here details needed materials for sample preparation, sample collection, sample pretreatment including preconcentration, and instrumental analysis. By reducing contamination throughout all phases mentioned above for trace metal analysis, much lower detection limits and thus accuracy can be achieved. The effectiveness of "clean techniques" is further demonstrated using low field blanks and good recoveries for standard reference material. The data quality that can be obtained thus enables the assessment of trace metal distributions and their relationships to environmental parameters.

Special care using "clean techniques" is required to properly collect and process water samples for trace metal studies in aquatic environments. A protocol for sampling, processing, and analytical procedures with the aim of obtaining reliable environmental monitoring data and results with high sensitivity for detailed trace metal studies is presented.

清洁取样和痕量金属研究河和河口水域分析

Most of the trace metal concentrations in ambient waters obtained a few decades ago have been considered unreliable owing to the lack of contamination ...

Determination of Inorganic Arsenic in a Wide Range of Food Matrices using Hydride Generation - Atomic Absorption Spectrometry.

The European Food Safety Authority (EFSA) underlined in its Scientific Opinion on Arsenic in Food that in order to support a sound exposure assessment to inorganic arsenic through diet, information about distribution of arsenic species in various food types must be generated. A method, previously validated in a collaborative trial, has been applied to determine inorganic arsenic in a wide variety of food matrices, covering grains, mushrooms and food of marine origin (31 samples in total). The method is based on detection by flow injection-hydride generation-atomic absorption spectrometry of the iAs selectively extracted into chloroform after digestion of the proteins with concentrated HCl. The method is characterized by a limit of quantification of 10 &#181;g/kg dry weight, which allowed quantification of inorganic arsenic in a large amount of food matrices. Information is provided about performance scores given to results obtained with this method and which were reported by different laboratories in several proficiency tests. The percentage of satisfactory results obtained with the discussed method is higher than that of the results obtained with other analytical approaches.

The usefulness of an analytical method to determine inorganic arsenic in a wide range of food matrices is demonstrated. The method consists of selective extraction of inorganic arsenic into chloroform with a final determination by hydride generation-atomic absorption spectrometry.

用氢化物发生-原子吸收光谱法测定多种食品基质中的无机砷。

The European Food Safety Authority (EFSA) underlined in its Scientific Opinion on Arsenic in Food that in order to support a sound exposure assessment to ...

The MPLEx Protocol for Multi-omic Analyses of Soil Samples

Mass spectrometry (MS)-based integrated metaproteomic, metabolomic, and lipidomic (multi-omic) studies are transforming our ability to understand and characterize microbial communities in environmental and biological systems. These measurements are even enabling enhanced analyses of complex soil microbial communities, which are the most complex microbial systems known to date. Multi-omic analyses, however, do have sample preparation challenges, since separate extractions are typically needed for each omic study, thereby greatly amplifying the preparation time and amount of sample required. To address this limitation, a 3-in-1 method for the simultaneous extraction of metabolites, proteins, and lipids (MPLEx) from the same soil sample was created by adapting a solvent-based approach. This MPLEx protocol has proven to be both simple and robust for many sample types, even when utilized for limited quantities of complex soil samples. The MPLEx method also greatly enabled the rapid multi-omic measurements needed to gain a better understanding of the members of each microbial community, while evaluating the changes taking place upon biological and environmental perturbations.

A protocol is presented for simultaneously extracting metabolites, proteins, and lipids from a single soil sample, allowing reduced sample preparation times and enabling multi-omic mass spectrometry analyses of samples with limited quantities.

土壤样品多涨价可能分析的 MPLEx 协议

Mass spectrometry (MS)-based integrated metaproteomic, metabolomic, and lipidomic (multi-omic) studies are transforming our ability to understand and ...

Sample Preparation for Analytical Characterization

Source: Laboratory of Dr. B. Jill Venton - University of Virginia
Sample preparation is the way in which&#160;a sample is treated to prepare&#160;for analysis. Careful sample preparation is critical in analytical chemistry to accurately generate either a standard or unknown sample for a chemical measurement. Errors in analytical chemistry methods are categorized as random or systematic. Random errors are errors due to change and are often due to noise in instrument. Systematic errors are due to investigator or instrumental bias, which introduces an offset in the measured value. Errors in sample preparation are systematic errors, which will propagate&#160;through analysis, causing&#160;uncertainty or inaccuracies through improper calibration curves. Systematic errors can be eliminated through correct sample preparation and proper use of the instrument. Poor sample preparation can also sometimes cause harm to the instrument.

分析制备的样品制备

Source: Laboratory of Dr. B. Jill Venton - University of Virginia
Sample preparation is the way in which&#160;a sample is treated to prepare&#160;for ...

教育

JoVE Science Education

分析化学

Introduction to Mass Spectrometry

Source: Laboratory of Dr. Khuloud Al-Jamal - King&#39;s College London

Mass spectrometry is an analytical chemistry technique that enables the identification of unknown compounds within a sample, the quantification of known materials, the determination of the structure, and chemical properties of different molecules.
A mass spectrometer is composed of an ionization source, an analyzer,&#160;and a detector. The process involves the ionization of chemical compounds to generate ions. When using inductively coupled plasma (ICP), samples containing elements of interest are introduced into argon plasma as aerosol droplets. The plasma dries the aerosol, dissociates the molecules, and then removes an electron from the components to be detected by the mass spectrometer. Other ionization methods such as electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI) are used to analyze biological samples. Following the ionization procedure, ions are separated in the mass spectrometer according to their mass-to-charge ratio (m/z), and the relative abundance of each ion type is measured. Finally, the detector commonly consists in an electron multiplier where the collision of ions with a charged anode leads to a cascade of increasing number of electrons, which can be detected by an electrical circuit connected to a computer.
In this video, the procedure of ICP-MS analysis will be described by the detection of 56Fe as an example.

Mass Spectrometer: Principle, Operation, Applications

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Source: Laboratory of Dr. Khuloud Al-Jamal - King&#39;s College London

Mass spectrometry is an analytical chemistry technique that enables the ...

Sample Preparation for Analysis: Advanced Techniques

Accurate analysis of complex samples often requires advanced preparation techniques to achieve reliable and reproducible results. Samples containing inorganic or organic materials can be challenging to dissolve or decompose effectively. Standard sample preparation methods include acid digestion, fusion, dry ashing, and wet digestion.
Acid digestion with strong acids is commonly used to dissolve inorganic materials that are insoluble (do not dissolve) in water. This method can be useful for analyzing soil or mineral samples. During acid digestion, the insoluble solid sample is finely ground or crushed to increase its surface area, which allows for a more effective reaction with the acids. The typically used acids include hydrochloric acid, nitric acid, sulfuric acid, and aqua regia &#8211; a mixture of nitric and hydrochloric acid. Each acid has specific advantages for different sample types:
<ol style="list-style-type: circle;">
	<li>Hydrochloric acid (HCl) is often used to dissolve chlorides, oxides, and carbonates and is also effective on materials such as metals and ores.</li>
	<li>Nitric acid (HNO&#8323;) is excellent for breaking down organic matter and oxidizing metals, making it a common choice for biological tissues or metal analysis.</li>
	<li>Sulfuric acid (H&#8322;SO&#8324;) is used when a strong dehydrating agent is needed, for instance, in dissolving more resistant samples like sulfides or metals.</li>
	<li>Aqua regia, a mixture of nitric and hydrochloric acids, is particularly effective for dissolving noble metals like gold and platinum, which are resistant to individual acids.</li>
</ol>
The sample is treated with the chosen high-strength acid in a suitable container, where it is broken down into soluble forms or ions. Heat may also be applied to speed up the digestion process. After digestion, the resulting mixture diluted with water is suitable for further analysis.
The fusion technique is an alternative method to dissolve inorganic materials that cannot be broken down to a soluble form by acid digestion. Here, the weighted sample is mixed with a flux material in a specific ratio, typically about 1 to 10 or 20. The sample-flux mixture is placed in a platinum crucible that is resistant to high temperatures and chemical reactions. This crucible is heated in a high-temperature furnace to obtain a molten mixture. After heating, the molten mixture is allowed to cool till it yields a new material soluble in water or dilute acid.
Several examples of flux usage in sample preparation for dissolving solid and liquid compounds are:
<ol style="list-style-type: circle;">
	<li>Na2CO3 and Na2O2 as Fluxes for Iron and Chromium Alloys: Sodium carbonate (Na2CO3) is a commonly used flux, but sodium peroxide (Na2O2) is employed due to its stronger oxidizing ability in certain cases. This combination is particularly useful for dissolving iron and chromium alloys in a nickel crucible.</li>
	<li>K2S2O7 for Refractory Oxides: When the target is refractory oxides (but not silicates), potassium disulfate (K2S2O7) serves as an effective flux. It can be prepared by heating potassium hydrogen sulfate (KHSO4) to decompose any foaming byproducts. K2S2O7 is effective in dissolving oxides and silicates with the application of heat.</li>
	<li>Li2B4O7 and Li2SO4 Mixture for Rapid Dissolution: A mixture of lithium tetraborate (Li2B4O7) and lithium sulfate (Li2SO4) in a 2:1 ratio by weight is highlighted for its rapid ability to dissolve refractory silicates and oxides.</li>
</ol>
Dry ashing and wet digestion methods are popularly used to decompose organic materials. In dry ashing, the organic sample is heated in a muffle furnace at a high temperature. The heat causes the combustion of the organic material in the presence of atmospheric oxygen, leaving behind an inorganic residue, or &#39;ash.&#39; This ash can then be dissolved in an appropriate solvent for further analysis. Wet digestion involves the use of acids to break down the organic material.

分析样品制备:先进技术

Accurate analysis of complex samples often requires advanced preparation techniques to achieve reliable and reproducible results. Samples containing ...