Determination of chlorogenic acid in traditional Chinese prescription Shuanghuanglian capsule using quantitative nuclear magnetic resonance spectroscopy in combination with solid phase extraction

The determination method of chlorogenic acid in traditional Chinese prescription Shuanghuanglian capsule was established by using quantitative nuclear magnetic resonance spectroscopy(q NMR) in combination with solid phase extraction(SPE). As the capsule’s main active component, chlorogenic acid comes from the extraction of Chinese herb medicine Flos Lonicerae. The chlorogenic acid in capsule was ultrasonically extracted at room temperature using pure water as solvent. The extracting solution was enriched and cleaned using HC-C18 SPE cartridge. The effect of ultrasonic extraction, sample pretreatment conditions via SPE and q NMR experimental conditions were investigated. The q NMR experiment conditions were selected using deuterated DMSO as solvent, calibrated 1,4-phthalaldehyde as internal standard, and P1(pulse width) = 14.4 μs, d1(pulse delay time) = 1 s, NS(number of scan) = 512. The 1 H NMR peaks of δ 6.138–6.182(H-8’, d, 1 H) of chlorogenic acid was chosen as the quantitative peaks. Method validation was performed, including precision(the intra-day RSD = 1.2% and the inter-day RSD = 1.5%), linearity(correlation coefficient r>0.9999), LOD(0.0017 mg/g) and LOQ(0.079 mg/g). The recovery of the SPE-q NMR was within the range of 100.2%–103.2%. The result showed that the method was stable, accurate and reliabile. Determined by the method, the chlorogenic acid in a real Shuanghuanglian capsule was within the range of 9.68–10.35 mg/g.

Accurate Quantification of Pure Thiacloprid with Mass Balance and Quantitative H-NMR

Thiacloprid is the first-generation neonicotinoid insecticide,which is widely used in modern agriculture.Reference materials are essential for sound measurement and traceability of results in chemical analysis.Pure thiacloprid was comprehensively assessed by two orthonormal methods:mass balance(MB) and quantitative nuclear magnetic resonance spectroscopy(qNMR).From MB,its mass fraction value was 998.4 mg/g with the subtraction of structurally related impurities(99.87%),inorganic impurities(0.006 mg/g),water(0.33 mg/g),and volatile organic solvent(0 mg/g).To guarantee sufficient separation of structurally related purity,peak purity of thiacloprid was evaluated by five points of UV spectra.From the qNMR of hydrogen,its mass fraction value was 995.7 mg/g which was traced to the internal standard(methyl sulfone).Finally,the certified value was assigned to 997 mg/g,together with an expanded uncertainty of 3 mg/g(k=2).This high-purity thiacloprid can be applied to routine monitoring in agriculture and the food fields.