Terahertz Time-Domain Spectroscopy and Quantitative Analysis of Metal Gluconates

Abstract

A series of metal gluconates (Na(+), K(+), Mg(2+), Ca(2+), Fe(2+), Cu(2+), and Zn(2+)) were investigated by terahertz (THz) time-domain spectroscopy. The absorption coefficients and refractive indices of the samples were obtained in the frequency range of 0.5-2.6 THz. The gluconates showed distinct THz characteristic fingerprints, and the dissimilarities reflect their different structures, hydrogen-bond networks, and molecular interactions. In addition, some common features were observed among these gluconates, and the similarities probably come from the similar carbohydrate anion group. The X-ray powder diffraction measurements of these metal gluconates were performed, and the copper(II) gluconate was found to be amorphous, corresponding to the monotonic increase feature in the THz absorption spectrum. The results suggest that THz spectroscopy is sensitive to molecular structure and physical form. Binary and ternary mixtures of different gluconates were quantitatively analyzed based on the Beer-Lambert law. A chemical map of a tablet containing calcium D-gluconate monohydrate and α-lactose in the polyethylene host was obtained by THz imaging. The study shows that THz technology is a useful tool in pharmaceutical research and quality control applications.

[Retracted] Enterprise Digital Transformation and Stock Price Crash Risk: Evidences from China

“…H1: better EDT could reduce stock price crash risk. Actually, enterprises sometimes choose to disclose information with strategic purposes, when they intend to exaggerate the degree and effect of transformation [43] and hide corresponding negative consequences and information. For enterprises with more bubbles in their stock price, it may make the market blindly optimistic, overestimate their transformation degree and operation status, and miss the opportunity to find bubbles, thus weakening the suppression effect of digital transformation on stock price crash risk.…”

“…Based on existing studies [43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58], this paper measures stock price crash risk by NCSKEW (negative coefficient of skewness) and DUVOL (down-to-up volatility). e specific calculation methods are as follows.…”

“…Most of the existing research on EDT mainly focuses on qualitative analysis from the perspectives of policy suggestions [4] [41] and theoretical analysis [42]. Some scholars began measuring the digital transformation level of enterprises from the microenterprise perspective and considered indicators such as digital intangible assets [43], e-commerce sales revenue [44], and the frequency of words related to digital transformation [12]. According to the research of Lin and Xie [58], word frequency represents the importance level an enterprise has given to the key issues (represented by the word).…”

A Feasible Approach to Detect Pesticides in Food Samples Using THz-FDS and Chemometrics

“…In recent years, THz spectroscopy combined with chemometrics is increasingly used for qualitative and quantitative detection in the field of biochemistry [12]. THz time-domain spectroscopy (THz-TDS), a widely used THz technology, has been applied to the detection of glucose hydrochloric acid [13], amino acids [14,15], and antibiotics [16]. It was found that these analytes all have fingerprint features in the THz range and thus their qualitative and quantitative detection can be achieved.…”

Wavelength Selection Method Based on Differential Evolution for Precise Quantitative Analysis Using Terahertz Time-Domain Spectroscopy

“…Hence, THz spectroscopy is widely adopted for qualitative and quantitative analysis of different types of materials such as amino acids, explosives, pharmaceuticals, and carbohydrates. 1–4 In particular, terahertz time-domain spectroscopy (THz-TDS) has proven to be a successful tool for constituent analysis of various mixtures. 5–8 However, the accuracy of quantitative analysis by THz-TDS is constrained by several factors.…”