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C24H16CoBr2N4O4, monoclinic, P21/c (no. 14), a = 11.1134(4) Å, b = 16.1731(6) Å, c = 13.7057(5) Å, β = 105.363(4)°, V = 2375.41(16) Å3, Z = 4, R gt(F) = 0.0588, wR ref(F 2) = 0.1101, T = 170(2) K.

Due to the simplicity of tea preparation (pouring hot water onto different dried herbs) and its high popularity as a beverage, monitoring and developing a screening methodology for detecting the metal content is very important. The concentrations of Cd, Ca, Cr, Cu, Fe, Pb, Mg, Mn, Hg, Na and Zn in 8 samples of green tea (Camellia sinesis) and in 11 samples chamomile (Matricaria chamomilla L.) purchased both at local herbal pharmacies and supermarkets were determined using electrothermal atomizer atomic absorption spectrometry (ETAAS) and flame atomizer atomic absorption spectrometry (FAAS). The found concentrations in chamomile were: Cd (0.008 – 284 mg kg−1), Ca (2.42 – 6.29%), Cr (0.91 – 6.92 mg kg−1), Cu (6.27 – 11.39 mg kg−1), Fe (133.5 – 534 mg kg−1), Pb (0.561 – 1.277 mg kg−1), Mg (2.27 – 3.73%), Mn (62.2 – 165.6 mg kg−1), Hg (0.660 – 1.346 μg kg−1), Na (0.91 – 1.28%) and Zn (63.37 – 108.5 mg kg−1), in green tea Cd (36.29 – 202.1 mg kg−1), Ca (2.77 – 6.40%), Cr (1.520 – 5.278 mg kg−1), Cu (9.354 – 22.56 mg kg−1), Fe (162.6 – 513.3 mg kg−1), Pb (1.808 – 4.770 mg kg−1), Mg (1.41 – 2.62 %), Mn (1.147 – 1.729 g kg−1), Hg (1.045 – 2.802 μg kg−1), Na (0.44 – 0.98%) and Zn (30.65 – 115.6 mg kg−1), respectively. Principal Component Analysis (PCA) was applied to identify factors (soil, climate and country of origin) influencing the content of the measured elements in herbal samples. The proposed methodology developed in this work was successfully applied to the detection of metals in herbal samples. The analysis showed that the content of toxic metals in green tea samples was significantly higher and very close to the maximum dose recommended by the World Health Organization (WHO).

Due to the simplicity of tea preparation (pouring hot water onto different dried herbs) and its high popularity as a beverage, monitoring and developing a screening methodology for detecting the metal content is very important. The concentrations of Cd, Ca, Cu, Fe, Pb, Mg and Mn in 11 different samples of sage (Salvia officinalis L.), linden (Tilia L.) and chamomile (Matricaria chamomilla L.) purchased at local herbal pharmacy were determined using electrothermal atomizer atomic absorption spectrometry (ETAAS) and flame atomizer atomic absorption spectrometry (FAAS). The concentrations determined were: Cd (0.012 – 0.470 mg kg−1), Ca (5209 – 16340 mg kg−1), Cu (22.01 – 33.05 mg kg−1), Fe (114.2 – 440.3 mg kg−1), Pb (0.545 – 2.538 mg kg−1), Mg (2649 – 4325 mg kg−1) and Mn (34.00 – 189.6 mg kg−1). Principal Component Analysis (PCA) was applied to identify factors (soil and climate) influencing the content of the measured elements in herbal samples. The proposed methodology developed in this work was successfully applied to the detection of metals in herbal samples. The analysis showed that the content of toxic metals in herbal teas was below the maximum dose recommended by the World Health Organization (WHO).

The theoretical titration curve of a weak acid with a strong base was considered. The limitation of the Henderson-Hasselbalch equation for the calculation of pH in the buffer region was discussed. One novel simple equation for the exact calculation of pH from the beginning of titration up to the equivalence point was derived. By using this equation with one implicit approximation (the dissociation of water), the calculation of pH values after each addition of titrant is possible. A novel equation provides the simple and exact calculation of pH in the range of buffer, and that can be done in a simple and logical way without complex handling of acid-base equilibrium with computer and spreadsheet software. The calculated titration curves for different concentrations of acetic acid and sodium hydroxide were shown.

C24H16CoBr2N4O4, monoclinic, P21/c (no. 14), a = 11.1134(4) Å, b = 16.1731(6) Å, c = 13.7057(5) Å, β = 105.363(4)°, V = 2375.41(16) Å3, Z = 4, Rgt(F) = 0.0588, wRref(F2) = 0.1101, T = 170(2) K. [ABSTRACT FROM AUTHOR]