大米中砷检测方案(等离子体质谱)

智能文字提取功能测试中

SPECIAL APPLICATION NOTEPlasmaQuant@ MS Elite analytikjena Analytik Jena AGKonrad-Zuse-Str. 107745 Jena/Germanyinfo@analytik-jena.comwww.analytik-jena.comPhone： +49 (0) 36 41/77 70Fax： +49 (0) 36 41/77 92 79Printout and further use permitted withreference to the source.5 analytikjena Fields of Application / Industry： Chemistry / Polymer Industry Clinical Chemistry/Medicine/Hygiene/Health Care Cosmetics Electronics Energy Environment/Water/ Waste Food / Agriculture Geology/ Mining Material Analysis Metallurgy /Galvanization Pharmacy ■Refineries/ Petrochemistry Semi-Conductor Technology Others analytikjena Speciation of Arsenic in Apple Juice by LC-ICP-MS onPlasmaQuant@MS Elite 1. INTRODUCTION The different physico-chemical forms of most elements vary in terms of mobility， toxicity and bioavailability. For example， arsenic species suchas the inorganic trivalent arsenic (As III) and pentavalent arsenic (AsV) are highly toxic whereas the organic forms as monomethyl arsenic(MMA) and dimethyl arsenic (DMA) have significantly reduced toxicities. Reporting only the total concentrations can often be misleading. When Liquid Chromatography (LC) is interfaced with Inductively Coupled Plasma MassSpectrometry (ICP-MS)， species elute one by one from the LC column directly to theICP-MS for detection by elemental speciation. The coupling of LC to ICP-MS is a straightforward task； no hardware changes are required to either the LC or ICP-MS. The LCcolumn is connected directly to the nebulizer of the ICP-MS. Coupling an LC to thePlasmaQuant@ MS Elite has the added advantage of offering up to 5 times moresensitivity， offsetting the loss of total signal resulting from the separation of each speciesand providing very low part-per-trillion (ng/L) detection limits. Fruits can be highly polluted with arsenic today， due to the use of arsenic-based pesticidesduring the past century. The following experiment shows the sensitivity and detectioncapabilities of the PlasmaQuant MS Elite for arsenic speciation in apple juice. SPECIAL APPLICATION NOTE PlasmaQuant@ MS Elite Speciation of arsenic in apple juice by LC-ICP-MS 2. INSTRUMENTATION The LC system used was a BRUKER Advance HPLC system with a 50 pm sample loop and a Hamilton PRP-X100 (4.6 mmx 150.0 mm，5 pm) anion exchange column. The ASpect MS software allows automatic optimization of the ion optics and plasma gas flows. Prior toconnecting the LC to the ICP-MS， it was optimized for maximum sensitivity on arsenic isotopes. ICP-MS and LC conditions are summarizedin tables 1 and 2. Table 1： PlasmaQuant@ MS Elite ICP-MS operating conditions Table 2： LC operating conditions Parameter Settings Mobile Phase A ： 12.5 mM ammonium carbonate， 1 % MeOH Auxiliary Gas Flow B：60.0mM ammonium carbonate，1% MeOH Flow Rate 1 mL/min Run Time 12 min Column Anion exchange， Hamilton PRP-X100， Monitored Ion 4.6 mm x 150.0 mm， 5 pm Column Temperature 40°C Sample Injection 50 pL Detection PlasmaQuantMS Elite ICP-MS lon Optics Optimized for 75As sensitivity 3. REAGENTS AND SAMPLES Deionized water (18.2 MQ/cm， Millipore MiliQ， Billerica， MA， USA) was used for all solution preparations (mobile phases， standardsolutions and samples). Mobile phase (LC) Ammonium carbonate Puratronic@ (Alfa Aesar) and methanol absolute ULC/MS (Biosolve BV， 5555 Valkenswaard) were used toproduce both A (12.5 mM ammonium carbonate，1% MeOH) and B (60 mM ammonium carbonate， 1 % MeOH) mobile phases.Mobile phases were prepared daily. Calibration standards Calibration solutions of arsenic trioxide (AslII， Acros Organics)， arsenic pentoxide (AsV， Sigma-Aldrich)， monosodium acid methanearsonate (MMA， Supelco) and cacodylic acid (DMA， Fluka) were prepared daily. Calibration ranged from 0.1 to 2.5 pg/l for all arsenic.species Sample preparation Five different apple juices (Juice 1 to 5) were purchased in a French supermarket including an organically grown product (Juice 2). Thesamples were filtered using a 0.45 um filter (Millipor Millex-HV) to suppress suspended matter. Filtrates were then diluted two-fold priorto analysis Internal standard Arsenobetaine (BCR626， IRMM) was spiked in every solution (standard solutions and samples) at 1 pg/L to correct for any potentialdrift and matrix effect. SPECIAL APPLICATION NOTE PlasmaQuant@ MS Elite Speciation of arsenic in apple juice by LC-ICP-MS 4. RESULTS AND DISCUSSION Elemental speciation Speciation of the four arsenic species (AsIII， DMA， MMA， AsV) and arsenobetaine (internal standard) were performed using the gradientLC method in less than 10 minutes. Excellent calibrations for each of the arsenic species were obtained with calibration coefficients≥0.9999 achieved when calibrating on solutions ranging from 0.1 to 2.5 pg/L as illustrated in Figure 1. Figure 1： Calibration curves for AslII， AsV， DMA and MMA Apple juice analysis Table 3 summarizes the As determination in five apple juice samples. Table 3： As species concentration in five commercial apple juices Concentration(ug/L) AslII DMA MMA AsV Total As Juice 1 0.297 0.088 0.010 1.550 1.945 *Juice 2 0.052 0.037 0.007 0.102 0.198 Juice 3 0.186 0.084 0.007 0.430 0.707 Juice 4 1.172 0.220 0.006 0.197 1.595 Juice 5 0.331 0.051 0.000 1.847 2.229 *Juice 2 was an organically grown product and had the lowest concentration of arsenic. The total As content in all five juices did not exceed3 pg/L. SPECIAL APPLICATION NOTE PlasmaQuant@ MS Elite Speciation of arsenic in apple juice by LC-ICP-MS Spike recovery To evaluate the repeatability of the method， undiluted apple juice1 was spiked with 1ug/L of each species. The spiked sample wasmeasured ten times and the average spike recovery for the four species is reported in table 4. Table 4： Results of the spike recovery test Average con- Spiked samples Average centration inthe unspiked 1 2 3 4 5 6 7 8 9 10 spike recovery sample AsllI 0.297 1.254 1.236 1.210 1.244 1.184 1.244 1.228 1.190 1.184 1.210 92% DMA 0.088 1.022 1.000 0.966 1.018 0.966 1.018 1.004 0.972 0.962 0.998 90% MMA 0.010 0.918 0.900 0.884 0.952 0.884 0.936 0.918 0.884 0.904 0.898 90% AsV 1.550 2.548 2.538 2.440 2.602 2.448 2.608 2.566 2.480 2.512 2.474 97% 500DO Figure 2：Overlay of 1 ug/L spiked (red) and unspiked (black) apple juice chromatograms SPECIAL APPLICATION NOTE PlasmaQuant@ MS Elite Speciation of arsenic in apple juice by LC-ICP-MS Long Term Stability 40 apple juice samples (8 hours) were run in the same sequence and a calibration check solution at 1 pg/L was measured every10 samples. Table 5 summarizes the results Table 5： Robustness test using a 1 pg/L calibration check solution over a sequence of 40 samples (8 hours) AslII (ug/L) DMA (ug/L) MMA (ug/L) AsV (ug/L) Check 1 1.021 1.031 1.012 1.024 Check 2 1.046 1.025 1.014 1.014 Check3 1.024 1.029 1.001 1.000 Check 4 0.997 1.048 1.026 1.034 The average readback for each species fell within the range of 1.013-1.033 ug/L and with a precision of 1-2 %RSD over the 8 hoursduration， thus validating the long term performance of the method. Typical detection limits Table 6 shows the method detection limits (DLs) for the four common organic and inorganic forms of arsenic in apple juice. All themeasurements were made under routine laboratory conditions. Detection limits were calculated using 3 times the standard deviation of blank samples (n=10). Table 6： Typical detection limits in apple juice using the PlasmaQuant@MS EliteArsenic species Detection limit (ng/L)Arsenite (AslII) 2.7Dimethyl arsenic acid (DMA) 2.6Monosodium acid methane arsonate (MMA) 2.7Arsenate (AsV) 3.3 5. CONCLUSION This work has demonstrated that the PlasmaQuant@MS provides excellent detection capability when coupled with a BRUKER AdvanceHPLC system for arsenic speciation in apple juice. Minimal sample preparation is required and consists of simple filtration and a two-folddilution. The high sensitivity of the PlasmaQuant@ MS Elite allows for routine detection of arsenic species to low part per trillion (ng/L)levels. uonal c Tuves CERT 8886189 Tic