LATVIA UNIVERSITY OF AGRICULTURE - Latvijas ...

ROOT VEGETABLES FROM LATVIA:QUANTITATIVE ANALYSIS OF TRACE ELEMENTSZane Vincevica-Gaile, Maris KlavinsCurrent study involves assessment of quantitativeanalysis of nine trace elements (As, Cd, Co, Cr, Cu,Ni, Pb, Se, Zn) in root vegetables grown in Latvia.Materials and MethodsSample collection and pre-treatmentFresh samples of harvested root vegetables (carrotsDaucus carota, onions Allium cepa and potatoesSolanum tuberosum) were collected over the territoryof Latvia in the harvesting season of 2010. The edibleparts of selected vegetables (carrot roots, onionbulbs and potato tubers) as well as some potato peelsamples were prepared for analyses. All the collectedsamples were confirmed as locally grown food cropsand were obtained at markets or directly from farmersand individual households. Sampling was carriedout by selecting 5 pieces of vegetables within everysingle sample. Cleaned, washed, peeled and crushedfresh samples were dried in the drying oven at 80 °Ctemperature for 20 hours. To avoid contaminationof samples only ceramic, porcelain, polypropyleneand certified laboratory glass vessels and tools wereexploited. After drying, the samples were milledor triturated till the consistence of powder. Beforeanalyses triturated vegetable samples were stored inclosed disposable plastic bags in a dry and dark place.Sample pretreatment can be conducted byseveral methods, e.g., dry ashing, wet ashing or wetdigestion that may be intensified by heat, microwaveor ultrasound influence (Alvarez et al., 2003). Theselected method, wet digestion of organic matter,is widely applied for samples of a biological origin(e.g., Gonzalvez et al., 2008; Ekholm et al., 2007;Soceanu et al., 2007). The mineralization processshould be implemented not only for cleavage oforganic matrix of biological samples but it also helpsto prevent analytical techniques from undesiredresidues that can settle on the burner heads and in thespray chambers and may affect spectral interferencesthat can result in inaccuracy of measurements (e.g.,Soceanu et al., 2007). The sample pre-treatmentprocedure was done as follows: a) 0.5000 ± 0.0020 gof dry sample was weighted on analytical balances;b) 10 ml of analytically pure concentrated HNO 3and 5 ml of ultra pure concentrated H 2O 2was added;c) after hold overnight, the sample solutions weredigested by heating at 160 °C temperature; d) afterthe digestion, sample solutions were filled up to 50 mlwith ultra pure deionised water.Applied analytical methodsSeveral modes of analytical methodologies canbe applied for trace and major element detectionin biological samples, including plants. Precision,accuracy and relative simplicity are the basic criteriathat the performance of analytical methods has to meet.There are several analytical methods that have beenused more frequently, for example atomic absorptionspectrometry (AAS) methods such as graphite furnaceatomic absorption spectrometry (Samsoe-Petersen etal., 2002) or flame atomic absorption spectrometry(Hashmi et al., 2007; Soceanu et al., 2007), that canbe useful also for the analysis of vegetables andfruits. Inductively coupled plasma mass spectrometry(ICP-MS) and inductively coupled plasma atomicemission spectroscopy (ICP-AES) are more sensitivetechniques and can be applied for trace and ultra traceanalysis of element content (Gonzalvez et al., 2008;Ekholm et al., 2007; Samsoe-Petersen et al., 2002).Total reflection X-ray fluorescence spectroscopy(TXRF) can also be applied (Alvarez et al., 2003).Within this study in total more than 200 samples(in triplicates) of onion bulbs (n=98), carrot roots(n=81), potato tubers (n=55) and potato peel (n=3)were analyzed. Nine elements (As, Cd, Co, Cr, Cu,Ni, Pb, Se and Zn) were detected by inductivelycoupled plasma mass spectrometry (ICP-MS). Theaccuracy of the applied analytical method was verifiedTable 1Accuracy of applied quantitative analytical method for some elements – certified and measured valuesof reference sample NCS ZC73017 (GSB-10)-AppleElementCertified values / 95% confidence Measured values by ICP-MS: mean ±interval, mg kg -1 standard deviation, mg kg -1Cd 0.0058 / 0.0046 – 0.0070 0.0051 ± 0.0002Pb 0.084 / 0.052 – 0.116 0.077 ± 0.007Zn 2.1 / 1.7 – 2.5 1.63 ± 0.17Cu 2.5 / 2.3 – 2.7 2.33 ± 0.04Ba 2.5 / 2.2 – 2.8 2.42 ± 0.08Mn 2.7 / 2.5 – 2.9 2.65 ± 0.04Rb 5.0 / 4.4 – 5.6 5.28 ± 0.09132 Research for Rural Development 2012