PDF《PinAAcle 900F火焰 原子吸收测定啤酒中》

Riccardo Magarini PerkinElmer, Inc.

Milano, Italy 简介 啤酒是一种广泛使用的饮料, 含有有机成分 和无机成分. 无机成分的浓度取决于原料 和酿造的过程. 啤酒知识中对无机成分的 浓度和类型有相当大的兴趣. 因为它们可能 PinAAcle 900F火焰 原子吸收测定啤酒中 重金属元素 Atomic Absorption 会影响口感、 外观、 产品稳定性和消费者的健康. 测定啤酒中无机元素的火焰原子吸收光谱法(FAAS)是一个著名的过程. 例如, 美国酝酿化学家协会(ASBC)在圣保罗,明尼苏达州,美国提出啤酒的常规测定钙 (Ca)、 铜(铜)、 铁(Fe)和钠(Na)使用火焰原子吸收光谱法(FAAS)测定. 火焰原子吸收光谱法(FAAS)使用更低的成本为每个元素测定提供精密, 准确的 技术基础, 相比其他微量元素测定方法, FAAS需要更少的操作人员. PinAAcle

900 FAAS提供了一个更直观、 高效的系统简化分析方法, 同时保证数据性能和 无与伦比的生产力. 应用文章作者:

2 Experimental Instrumentation All measurements were performed on a PerkinElmer PinAAcle 900T atomic absorption spectrometer equipped with high sensitivity nebulizer (HSN) and ceramic impact bead. An air-C2H2 flame with a

10 cm 3-slot solid titanium burner head was used for the determination of copper (Cu), iron (Fe), zinc (Zn), and manganese (Mn). Aluminum (Al) was determined with N2O-C2H2 flame on a

5 cm solid titanium burner head. A nebulizer spacer was used for calcium (Ca) and sodium (Na) to reduce sensitivity, and for Al to improve N2O flame stability and minimize interferences. Lumina? cableless hollow cathode lamps were used for all elements. Sample Preparation Several brands of beer were purchased in a local supermarket in Singapore. When available, the same brand was purchased in two different packaging materials: a glass bottle and a metal can. A total of five bottled and six canned beers were analyzed. Sample aliquots for analyses were obtained by pouring the beers in

50 mL polyethylene autosampler tubes with caps. Samples were degassed of CO2 by ultra-sonication at full power for

30 minutes and then acidified to

2 % (v/v) with HNO3 (70 % w/v, Clean Room Chemical, Air Products and Chemicals Inc, Allentown, Pennsylvania, USA). All elements were measured against external calibration curves with linear-through-zero regression, except Na, which used a non-linear through zero regression. Standards were prepared by serial dilutions of

1000 mg/L PerkinElmer Pure single-element standards in 2% HNO3 (v/v). Elements usually present at trace levels (Al, Cu, Fe, Mn, and Zn) were determined directly in the undiluted beers. The calibration solutions for these elements were prepared in 5% (v/v) ethanol (99.5% GR grade, Kanto Chemical Co. Inc., Japan) for matrix matching. For Al determination, 0.2% lanthanum (La) (w/v) was added to all samples and standards as an ionization buffer (La2O3 99.5% LAB grade, Merck, Germany). For the determination of Ca and Na, the samples were diluted

30 fold with ≥

18 MΩ ultrapure water (MilliQ system, Millipore, Billerica, Massachusetts, USA). Calibration standards were prepared in 1% HNO3 (v/v). No ethanol was added, due to the dilution factor. La 0.2% (w/v) was added as a releasing agent (to avoid phosphate suppression on Al) and as an ionization suppressant for Na and Ca (releasing agents are cations that react preferentially with an interferent). Table

1 shows the instrumental conditions used for this work. Results and Discussion Each beer sample was given a number to identify the brand and container type. Samples labeled G were from glass bottles, while samples labeled M were from metal cans. Results, reported in Table 2, show that Ca and Na are present at high concentrations (mg/L), while other elements are present at ?g/L levels, as expected. The data showed good quality for all beers tested, with respect to their elemental contents, based on the current ASBC guidelines. These results indicate that the container material (glass or can) does not significantly contribute to the element content of the beer, with the exception of Mn, which is always a little higher in the bottled beers. Due to the low level of Al in the beer samples tested, it could not be detected by FAAS in most samples. Instead, a more sensitive technique, such as graphite furnace atomic absorption spectrometry (GFAAS), should be used for Al determination. The PinAAcle 900T (and 900H) can easily be switched between flame and graphite furnace modes, offering the capability to determine the low concentration elements by GFAAS using a single system. For analysis using flame-only atomic absorption, the PinAAcle 900F is also available. Element Wavelength (nm) Slit (nm) Lamp Current (mA) Units Calibration Standards Air (L/min) Nitrous Oxide (L/min) Acetylene (L/min) Al 309.27 0.7