Phân tích định lượng các nguyên tố vết trong cây artichoke tại thành phố đà lạt sử dụng phương pháp huỳnh quang tia X phản xạ toàn phần

f research have shown that the concentration of 
elements in plants depends on the kinds of plants and their parts: Flowers, leaves, crowns, 
trunks, and roots. For example, Pb contamination can caused by the bioaccumulation of 
Pb in edible vegetables. Finster, Gray, and Binns (2003) investigated Pb contamination 
from the soil via the root system by direct foliar uptake and translocation within the plant. 
Alexander et al. (2009) showed that Cd accumulates in the leaves of plants. Pb is an 
environmental contaminant that occurs naturally and in traffic. As one case, terrestrial 
plants may accumulate arsenic by root uptake from the soil or by absorption of high levels 
of airborne arsenic deposited on the leaves. Arsenic is a metalloid that occurs in different 
inorganic and organic forms (European Food Safety Authority, 2009). The European 
Union has also published (Commission of the European Communities, 2006) a regulation 
in which maximum levels have been set for Cd and Pb in foodstuffs such as vegetables. 
Trace elements play an essential role in health. Beccaloni, Vanni, Beccaloni, and Carere 
(2013) have investigated the daily necessary concentrations of essential trace elements in 
food. In a recently published paper, Biel, Witkowicz, Piątkowska, and Podsiadło (2019) 
found twelve elements for which toxic inorganic concentrations are very low (Cr, Pb and 
Cd) just only. 
Artichokes are a rich source of vitamins and nutrients to stimulate fat burning and 
lower the levels of bad cholesterol in the blood. Normally, people use fresh artichokes, 
especially the flowers, in hot soup for their family meals. Roots and flowers of the 
artichoke are also used to manufacture tea. In this study, the main purpose is to determine 
the trace element concentrations in artichokes that grow in Dalat. The artichokes were 
collected from two farms: One farm is located near Than Tho Lake, and the other farm is 
on Huynh Tan Phat Street. Both farms are located in Ward 12 of Dalat, which is well 
known for growing artichokes. The stems, leaves, flowers, and roots of the artichokes 
were examined with the TXRF technique in this research. 
2. MATERIALS AND METHODS 
2.1. Sampling 
Dalat is a tourist city, about 390 km² in area, located in Lam Dong province in 
Vietnam. Dalat is located at 11.95º latitude and 108.44º longitude and sits approximately 
1500 m above sea level. The two best places where artichokes have good conditions for 
growth in Dalat are near Than Tho Lake (located at 11.95842º latitude and 108.47579º 
longitude) and on Huynh Tan Phat Street (located at 11.9706º latitude and 108.48704º 
longitude) which are part of Ward 12 in Dalat. Dalat artichokes are not only famous in 
Vietnam but also worldwide. The harvest season for artichokes in Dalat is from February 
DALAT UNIVERSITY JOURNAL OF SCIENCE [NATURAL SCIENCES AND TECHNOLOGY] 
70 
to July annually. In our research, the artichoke collection was carried out for two weeks, 
from 2nd to 16th February 2020. The artichoke sample sites in Dalat are shown in Figure 1. 
Figure 1. The artichoke sampling locations (shown as ovals) in Ward 
Figure 2. The location of Ward 12 on a map of Dalat 
For the samples, around 20 kg of fresh artichokes were collected, including 
flowers, stems, leaves, and roots. Twelve samples were collected, three samples for each 
of the four parts of the artichoke. Figure 3 presents the morphology of the artichokes and 
a powder sample. 
(a) 
(b) 
(c) 
(d) 
(e) 
Figure 3. Parts of artichokes 
Notes: a) Flowers; b) Stems; c) Leaves; d) Roots; and e) Artichoke powder. 
Nguyen Thi Minh Sang, Pham Thi Ngoc Ha, Nguyen Thi Nguyet Ha, and Nguyen An Son 
71 
To minimize the influence of the substrate, the different parts of the artichoke, 
flowers, stems, leaves, and roots, were chopped. After collection, the flowers, stems, 
leaves, and roots of the artichokes were cleaned of soil particles, washed three times with 
distilled water, then dried at 700C for 50 hours. Next, they were crushed and homogenized 
to a powder (~0.5 mm) in an analytical sieve shaker AS 300 control for 30 min. As the 
next step, the artichoke powder samples were ground down to grain sizes of 50 µm using 
a RETSCH MM 400 mixer mill. In the final step of sample preparation, the moss powder 
sample must be turned into a liquid form using digestion. In this investigation, a MARS 
6 Microwave Acid Digestion System was used. An artichoke powder sample weighing 
0.5 g was placed into the digestion vessel and 10 ml of HNO3 (14 N) was added. We 
gently swirled the mixture and waited approximately 15 min before closing the vessel. 
Operating the RETSCH MM 400 mixer mill is 50 min. After finishing this procedure, the 
artichoke sample was a liquid. Then 500 µl of the original sample was transferred to a 
polymer container, to which was added Galium internal standard liquid so that the sample 
reached 1 ppm Galium. The sample must be thoroughly homogenized by an automatic 
sample shaker. After thorough homogenization, 10 µl of the sample was transferred to a 
sample carrier and then dried at 300 degrees C. Figure 4 shows a sample. According to 
the Bruker AXS Microanalysis GmbH (2007), a good condition for quantification using 
an internal standard is to prepare the sample as a thin layer (<100 μm). Furthermore, the 
diameter of the sample spot on the sample carrier must not exceed 10 mm. 
(a) 
(b) 
Figure 4. A prepared artichoke sample 
Notes: a) A drop of liquid artichoke on the sample carrier; and b) A dry artichoke sample. 
2.2. TXRF technique 
In this research, an S2 PICOFOX™ TXRF spectrometer, provided by Dalat 
University, was used for the multi-element analysis. The ability of TXRF detection 
depends on the energy of the X-ray tube and the elements in the sample. The S2 
PICOFOX spectrometer can detect and measure K-line energy in many elements (Towett, 
Shepherd, & Cadisch, 2013). 
The S2 PICOFOX™ TXRF spectrometer was used to collect the characteristic X-
ray spectrum for each artichoke sample. The spectrometer was operated at 50 kV voltage 
with a maximum tube rating of 50 W. All 12 artichoke samples and the gain correction 
sample must be introduced into the sample changer (Figure 5). 
DALAT UNIVERSITY JOURNAL OF SCIENCE [NATURAL SCIENCES AND TECHNOLOGY] 
72 
Figure 5. The sample insertion into the TXRF spectrometer 
The reset of the spectroscopic amplification is accomplished with the gain 
correction software function. In this process, a correction value is transferred to the 
spectroscopic amplifier after performing a duplicate measurement with a known 
fluorescence peak. For the gain correction, a mono-element standard sample was used. A 
measurement time of 120 s for each sample was established as sufficient for the necessary 
statistics. Spectra for the four artichoke parts are shown in Figure 6. 
Figure 6. The X line spectra collected from an artichoke sample 
Notes: Colors of spectra: __ flower, __ leaf, __stem, __root . 
The fit quality is a statistical parameter that measures the quality of the 
deconvolution. The value for the fit quality should preferably be smaller than 10. High 
values (>10) are an indication of misidentified or nonidentified elements, respectively, or 
inaccurate gain correction. The fitting function is used to fit the following: 
 𝜒2 =
1
𝑛2−𝑛1
∑
1
𝛿𝑖
2 (𝑦𝑖+1 − 𝑦𝑖)
2𝑛2
𝑖=𝑛1
 () 
2 4 6 8 10
- keV -
0
20
40
60
80
x 1E3 Pulses
 Ga Ga P P K 
 K 
 Ca Ca Mn Mn Fe 
 Fe 
 Zn 
 Zn 
 Cu 
 Cu 
 Cd Cd 
 Cd 
 Hg Hg Hg Pb Pb 
 Pb As As 
Channel (keV) 
Counts 
Nguyen Thi Minh Sang, Pham Thi Ngoc Ha, Nguyen Thi Nguyet Ha, and Nguyen An Son 
73 
where n1 is the first channel of peak i (the left channel), n2 is the end channel of 
peak i (the right channel), yi+1 is the counts of channel i+1, and yi the counts of channel i. 
𝛿𝑖 = √𝑁𝑖 + 2𝑁𝐵𝐺 (2) 
where δi is the standard deviation for the peak area, Ni is the net peak area for 
element i, and NBG is the background area. 
3. RESULTS AND DISCUSSION 
Element concentrations for four parts of the artichokes from the two farms are 
shown in Table 1. In this method, the errors in the concentrations are less than 10% 
(Bruker AXS Microanalysis GmbH, 2007). Concentrations of 11 elements, P, K, Ca, Mn, 
Fe, Cu, Zn, As, Cd, Hg, and Pb, were measured in this work. The concentrations of all 11 
elements were obtained in units of mg.kg-1. 
In this result, the mean concentrations of the elements in the Dalat artichoke 
samples decreased as: K > Ca > P> Cd > Fe > Mn > Zn > Cu > Hg > Pb > As. The nutrient 
most absorbed by artichoke plants during the growing cycle, especially on flowers and 
leaves. In our data, the element concentrations in the stems are usually the lowest. The 
potassium and calcium concentrations in the flowers and leaves usually are a little higher 
than in the roots and stems. We suggested that the farmer had sprayed pesticide on the 
leaves directly. As a result, three toxic metals, As, Hg and Pb, have very low 
concentrations, but cadmium, which has existed in inorganic elements, is high in 
concentration. Cadmium is a heavy metal that poses severe risks to human health. 
Normally, cadmium is part of the chemical composition of pesticides, so the farmers need 
to control and reduce pesticide use. 
The mineral profile of globe artichoke floral stems was found to be significantly 
affected by cultivar, season, and interaction (Lombardo, Pandino, Mauromicale, Carle, 
Knódler, & Schieber, 2011). In general, the present results are in good agreement with 
those of previous studies (Lombardo, Pandino, Mauro, & Mauromicale, 2013; Pandino, 
Lombardo, & Mauromicale, 2010). According to literature data (Rincón, Pérez, Pellicer, 
Abadía, & Sáez, 2007; Romani, Pinelli, Cantini, Cimato, & Heimler, 2006), the element 
concentrations decrease as follows: K > Ca > Na > Mg (for alkali metals and alkaline 
earth metals), and Fe > Cu > Mn > Pb >As > Hg (for lanthanides). All toxic trace metal 
concentrations in this investigation are lower than Lombardo’s results (Lombardo et al., 
2013). Our data are similar to those of Terzić, Atlagić, Maksimović, Zeremski, Zorić, 
Miklič, & Balalić (2012), especially for those trace minerals required for biological 
processes in the body, including Fe, Cu, Mn, and Zn. 
DALAT UNIVERSITY JOURNAL OF SCIENCE [NATURAL SCIENCES AND TECHNOLOGY] 
74 
T
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Nguyen Thi Minh Sang, Pham Thi Ngoc Ha, Nguyen Thi Nguyet Ha, and Nguyen An Son 
75 
4. CONCLUSION 
Artichokes grown at two farms in Dalat were investigated. The TXRF technique 
was used to determine the concentrations of 11 inorganic elements, including P, K, Ca, 
Mn, Fe, Cu, Zn, As, Cd, Hg, and Pb in four different parts of the artichoke. The element 
concentrations of artichoke flowers and leaves are similar. Our research also shows that 
these trace minerals, which are required for biological processes in humans, are in good 
agreement with values from previous work (Terzić et al., 2012). 
One notable finding for agriculture is that the concentration of cadmium is quite 
high, so farmers could slash pesticide use if they want to grow safe foods and develop 
stability in agricultural production. 
ACKNOWLEDGMENTS 
This work was supported by Dalat University under the project. 
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