Determination of metals content (Ag, Al, As, Ba, Ca, Cd, Cr, Co, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, Pb, Sb, Se, Sn, V, Zn) in thyme herb by method of atomic emission spectrometry with inductively coupled plasma

Abstract

The aim of the study is to quantitatively determine the content of 23 metals (Ag, Al, As, Ba, Ca, Cd, Cr, Co, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, Pb, Sb, Se , Sn, V, Zn) in medicinal plant raw materials «thyme herb» to
assess consumer safety and compliance with the requirements of modern regulatory documentation. Sample preparation (homogenization) was carried out in a «Multiwave Go Plus» microwave by combustion
with 70% HNO3. The contents were quantitatively transferred into a measuring cup and diluted to the desired concentration. Measurements of metal concentrations in test and blank solutions were carried out using an
Agilent 5800 ICP-OES inductively coupled plasma optical emission spectrometer. The metal content was measured by comparing the emission of the test and blank solutions with the emission of standard solutions. Low concentrations of tin and antimony were observed in thyme herb: Sn – 0,18, Sb – 0,23 mg/kg. Heavy toxic metals – cadmium, arsenic, lead – were found in the test sample: Cd – 0,13, As – 0,48, Pb – 0,76 mg/kg.
There were a small contents of cobalt, selenium, chromium, molybdenum, nickel, vanadium (Co – 0,35, Se – 0,544, Cr – 2,19, Mo – 0,68, Ni – 2,12, V – 2,27 mg/kg) and noticeable amounts of copper, barium, manganese and zinc (Cu – 5,83, Ba – 47,6, Mn – 83,2 and Zn – 16,8 mg/kg). Large amounts of aluminum and sodium were determined (Al 813,1, Na 781,7 mg/kg). The highest concentrations were identified for
calcium, iron, potassium and magnesium (Ca – 11062, Fe – 1184, K – 17753, Mg – 3741 mg/kg). The total metal content was 35498 mg/kg (3,55% of the mass of dry thyme herb). The concentrations of the chemical elements As, Ba, Cu, Fe, Mg, Mo, Mn, Ni, Sn in the tested sample are approximately 10 times (by an order of magnitude) lower than their distribution in the earth's crust. The
amount of chemical elements Al, Co, Cr, Na, Pb, V in the tested sample is approximately 100 times (two orders of magnitude) less than the content in the earth's crust. The content of the biogenic chemical elements Ca, K, Zn (necessary for the normal functioning of plants), Se (a useful trace element) and scattered impurity elements Cd and Sb are approximately of the same order. Literature data on the recommended content of chemical elements (Ag, Al, As, Ba, Ca, Cd, Cr, Co, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, Pb, Sb, Se, Sn, V, Zn) in medicines, pharmaceutical raw materials, medicinal plant raw materials were collected. Daily exposures of these chemical elements during oral administration are presented. These data can be used by manufacturers, in particular, when regulating the upper limit of the amount of metal compounds in dietary supplements. When recalculating the amount of these chemical elements per 10 g of thyme herb (the sample required to prepare an infusion for 1 day according to the recommendations of the Ministry of Health of Ukraine), the content of metals meets the requirements of modern regulatory documentation.