Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) Applied to Wine

Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES)Applied to WineQuantitative AnalysisCell 7Connor McBroom, Heather McCann, Melinda McClure, Caitlyn McCurdy, Matthew Mohr, Anthony Mu, Matthew Nesloney, Anh-Vu Nguyen, Phan Nguyen

1Why do we care about ICP-AES?Many wines contain metalsPb: 300 PPB can cause brain damage and infertilityMg: Accumulation in the brain can be linked to Parkinsons DiseaseHg: Can cause Minamata disease and ataxiaMetals enter wines via the soil, fungicides, and lead caps of wineGovernments regulate metal content in wine in order to protect consumersRegarded as the most versatile analytical technique in the chemistry laboratory for both robustness and speed, making laboratories much more efficientThe ICP-AES method is used to determine concentration of metals in many applications, ranging from soils and pond water to wine.

What is ICP-AES?Plasma Hot gas with ions and fast-moving electrons (7000-10000K)Usually superheated Argon for ICP-AESAll bonds within sample are brokenNeutral particles become charged and electron advance to higher energy levels as particles collide Particles release photon as they move to a lower energy stateWavelength is received by spectrometer, which is usually in the UV-VIS rangeFinal readings show presence of analyte and its concentration based on light intensity at given wavelengths.

National History Museum, 2006

FusionFuture, 2012Argon is awesome

As seen, argon is both cheap and easily ionizable, making it ideal for use with plasma generation and reaction in an ICP-AES, cost of operation will make a huge difference. Joachim, 2003 p. 13How ICP-AES WorksThe Mechanics

Sample PreparationSample Must Be:Dissolved in solutionA mixture of nitric and hydrochloric acid (acidic)Measured quicklyMatrix matched (all samples must have same acidity)FilteredDilutions might be needed to fall within machines level of detection WhyTo keep the machine in properly working orderMinimizes error in concentration readingALSOStandard solutions must be made at this step! And then run with every sample. More on this later.

Sample IntroductionPutting the sample into the machine is a delicate processDo not want to impair stability of sampleDo not want to influence emission signalsTurning sample into aerosol helpsUse of NebulizationUltrasonic NebulizerSample pumped into small vibrating platePneumatic NebulizerCreates negative pressure zoneAnalogous to suction through a strawCross flow is normally usedNebulizer chamber separates larger particles from smaller onesOnly 1-2% of original sample makes it to plasma torch the rest is gone as waste.

Perkin-Elmer Instruments, 2005NebulizerChamberTorch

Perkin-Elmer instruments, 2000Burning PlasmaIgnition of Plasma (7000-10000 degrees Kelvin)Oxygen and Nitrogen purgedRadiofrequency generatorIonizes Argon with high frequency electrical fieldAlternating magnetic fields accelerate particles even more heat generatedParticles begin colliding

Plasma used to atomize and excite particlesSample aerosol injected with peristaltic pump into plasma torchVarious tubes wrapped in an induction coil

New Mexico State University, 2006 Pennsylvania State University, 2008

Output and Emission LinesLight from the excited plasma enters optical refinementMany mirrors and refraction graters relay light to computer as a 2D image IMPORTANT

Perkin-Elmer, 2014

Perkin-Elmer, 2014Conceptual UnderstandingAnalysis of Metals in Wine

Perkin-Elmer, 2011Maria, April 26th, 2013Objective of AnalysisICP-AES is used to find metal content in wineMultiple traces and elements can be determined at onceWe want an accurate means of detecting these metals that is reproducible and accurateAs many as 200 samples can be analyzed a day and over 10,000 analytes can be detected among them

Methods

10 samples of Sherry wines prepared by heating 100 mL samples to get rid of oxygenated compounds After heating, wine samples transferred to 100 mL volumetric flask and diluted with DI water, which had pH 2.8 3.1, which was in the range of standard working solutions used to calibrate the ICP-AESSamples diluted to fall within range of detection based on metal type:Al, Cu, Fe, Mn, Na, and Zn had 1:5 optimal dilutionsK and Mg had optimal emission at 1:25 dilutionCa required 1: 15 (diluent 0.5% lanthanum to correct)

NYT, 2013Methods cont. In order to obtain a linearity of the response among the samples, a calibration curve was prepared by analyzing the standard aqueous solutions with concentration ranges from 0.020 to 4.000 mg/L. This regression allowed us to connect wavelength and intensity to concentration: I (intensity)a = intercept (regressed, fit from data +/- SD) + slope(+/- SD)*[concentration of element in mg/L] The computer generates as many numbers of these curves as the user wishes to identify, and this is obtained from standard and sample preparation. The standard deviations are thrown in as a means of ensuring the concentrations are applied to a range, or levels of detection (LOD) that are statistically verifiable. Based on the emission signals per element, concentration of analyte is interpolated from these calibration curves.

Measurable QuantityMachine detects the characteristic wavelength of light being emitted by each element in the sampleMonochromator measures the corresponding wavelengths intensity and converts both readings into a concentration using the calibration curve for that element.

Metal Content in WineSD = Standard DeviationRSD = Relative standard deviation

Journal of AOAC, 1996Fundamental PrinciplesElements can only have a certain energy state and the differences in energies are E = nhvThe former equation, along with = c / vC is the speed of lightV is the frequency of the waveWith these equations the identity and concentrations of metals can be found

Accuracy and PrecisionRegulations set by states and countries need to be metSpectrometer is flushed with N2 gasAnalyze samples in random order, at room temperatureAllow the machine to warm up because of high temperaturesToo much free oxygen causes background interference

Quiz questionsWhy is argon gas used in the plasma torch?Argon gas is used because it is a low molecular weight gas that is easily ionizable/ignitable and is efficient at the temperatures required. Quiz cont.How does the machine convert an emission signal into an analyte concentration? The machine is pre-calibrated with elements to reduce background noise. This is a part of ensuring the analysis is accurate. Light from the burning plasma is filtered through an optical series and read by a photomultiplier, which in turn is interpreted as the presence of a metal based on the the emission wavelengths generated, similar to how in infrared spectroscopy gives wavenumbers for very specific functional groups. The concentration is obtained from calibration curves which primed the machine based on the wavelengths intensity

Things to considerWhy ICP-AES? Why not GFAAS, ICP-MS, Flame AAS?Other methods can do the same thingInductively coupled plasma-mass spectrometry (ICP-MS)Flame Atomic Absorption Spectroscopy (Flame AAS)Graphite Furnace Atomic Absorption Spectrometry (GFAAS)

Pennsylvania State University, 2008ICP-AESCheapRobust and accurateStudent proofGood for routine analysisEfficientWine is awesome

References1 - "What Is Plasma?"FusionFuture.org. Wordpress, n.d. Web. 31 Mar. 2014.2 - "Inductively Coupled Plasma (ICP) Techniques."Natural History Museum. N.p., n.d. Web. 31 Mar. 2014.3 - Nolte, Joachim.ICP Emission Spectrometry: A Practical Guide. Weinheim: Wiley-VCH, 2003. Print.4 - "Chapter12 Metal Flows and Environmental Impact."Environmental Science. The Baltic University, 2005. Web. 01 Apr. 2014.5 - "NMSU: ICP Introduction."NMSU: ICP Introduction. New Mexico State University, 2006. Web. 01 Apr. 2014.6 - "Materials Characterization Lab - ICP-AES."Materials Characterization Lab - ICP-AES. Pennsylvania State University, 2008. Web. 01 Apr. 2014.7 - Optima 8300 ICP-OES Spectrometer. Digital image.PerkinElmer Inc.Perkin-Elmer, 2014. Web. 01 Apr. 2014.8- Maria. "Femmepirical Evidence: Take Chances! Make Mistakes! Get Messy! Femmespiration: Ms Frizzle."Femmepirical Evidence: Take Chances! Make Mistakes! Get Messy! Femmespiration: Ms Frizzle. Blogspot, 26 Apr. 2013. Web. 01 Apr. 2014.9 - Asimov, Eric. "In Spain, Sherry Producers Learn to Think Small."The New York Times. The New York Times, 19 June 2012. Web. 01 Apr. 2014.10 - References cont.9- Repetto, Manuel, Ana M. Camean, and Miguel Lopez-Artiguez. "Determination of Nine Elements in Sherry Wine by Inductively Coupled Plasma-Atomic Emission Spectrometry."Journal of AOAC97.5 (1996): 1191-197. Print.