LED-Induced Fluorescence System for Tea Classification and Quality Assessment

A fluorescence system is developed by using several light emitting diodes (LEDs) with different wavelengths as excitation light sources. The fluorescence detection head consists of multi LED light sources and a multimode fiber for fluorescence collection, where the LEDs and the corresponding filters can be easily chosen to get appropriate excitation wavelengths for different applications. By analyzing fluorescence spectra with the principal component analysis method, the system is utilized in the classification of four types of green tea beverages and two types of black tea beverages. Qualities of the Xihu Longjing tea leaves of different grades, as well as the corresponding liquid tea samples, are studied to further investigate the ability and application of the system in the evaluation of classification/quality of tea and other foods

15α,20β-Dihydr­oxy-6β-meth­oxy-6,7-seco-6,20-ep­oxy-1,7-olide-ent-kaur-16-ene

The title compound, C21H30O6, a natural ent-kaurane diterpenoid, was obtained from the medicinal plant Isodon serra. The five rings in the mol­ecule exhibit the expected cis and trans junctions. The three six-membered rings adopt chair, twist-boat and boat conformations, while two five-membered rings adopt envelope conformations. There are two mol­ecules in the asymmetric unit, related by a non-crystallographic twofold screw axis; the main difference is in the different degrees of distortion of ring B. In the crystal, the mol­ecules are linked by inter­molecular O—H⋯O hydrogen bonds, forming chains along the b axis

Bis[N,N-bis­(2-hydroxy­ethyl)dithio­carbamato-κ2 S,S′]copper(II)

In the title compound, [Cu(C5H10NO2S2)2], the CuII cation is chelated by two bis­(2-hydroxy­ethyl)dithio­carbamate anions with a distorted square-planar coordination geometry. Inter­molecular O—H⋯O hydrogen bonding is observed between the terminal hydr­oxy groups in the crystal structure

catena-Poly[[tetra­aqua­manganese(II)]-μ-5-carboxyl­ato-1-carboxyl­atomethyl-2-oxidopyridinium-κ2 O 5:O 1]

In the title coordination polymer, [Mn(C8H5NO5)(H2O)4]n, the MnII atom is coordinated by two carboxyl­ate O atoms from two 5-carboxyl­ato-1-carboxyl­atomethyl-2-oxidopyridinium (L 2−) ligands and by four water mol­ecules in a distorted octa­hedral geometry. The L 2− ligands bridge the Mn atoms into an infinite chain motif along [100]; the chains are further inter­linked by O—H⋯O hydrogen bonds into a three-dimensional supra­molecular net

Poly[[aqua­bis(μ3-isonicotinato-κ3 O:O′:N)tris­(μ2-isonicotinato-κ3 O,O′:N)(nitrato-κO)bis­(μ4-oxalato-κ6 O 1,O 2:O 2:O 1′,O 2′:O 1′)dierbium(III)tetra­silver(I)] tetra­hydrate]

In the title coordination polymer, {[Ag4Er2(C6H4NO2)5(C2O4)2(NO3)(H2O)]·4H2O}n, each ErIII atom is coordinated in a bicapped trigonal–prismatic coordination geometry by three O atoms from two isonicotinate (IN) ligands, four O atoms from two oxalate ligands and one O atom from either a nitrate ion or a water mol­ecule, both of which are half-occupied over the same site. One AgI atom has a Y-shaped geometry defined by one N atom from one IN ligand, one O atom from another IN ligand and one O atom from an oxalate ligand. The other AgI atom is coordinated by two IN ligands and one O atom from an oxalate ligand. One of the IN ligands is disordered over an inversion center and forms a bridge between two centrosymmetric AgI ions. Due to the disorder, this IN ligand coordinates to the Ag atom through either the pyridyl N or the carboxyl­ate O atoms. The IN and oxalate ligands link the Er and Ag atoms into a three-dimensional coordination framework. O—H⋯O and C—H⋯O hydrogen bonds are observed in the crystal structure