Analytical Instrument Documents

Three-dimensional electron diffraction crystallography (microED) can solve structures of sub-micrometer crystals, which are too small for single crystal X-ray crystallography. However, R factors for the microED-based structures are generally high because of dynamic scattering. That means R factor may not be reliable provided that kinetic analysis is used. Consequently, there remains ambiguity to locate hydrogens and to assign nuclei with close atomic numbers, like carbon, nitrogen, and oxygen. Herein, we employed microED and ssNMR dipolar-based experiments together with spin dynamics numerical simulations. The NMR dipolar-based experiments were 1H-14N phase-modulated rotational-echo saturation-pulse double-resonance (PM-S-RESPDOR) and 1H-1H selective recoupling of proton (SERP) experiments. The former examined the dephasing effect of a specific 1H resonance under multiple 1H-14N dipolar couplings. The latter examined the selective polarization transfer between a 1H-1H pair. The structure was solved by microED and then validated by evaluating the agreement between experimental and calculated dipolar-based NMR results. As the measurements were performed on 1H and 14N, the method can be employed for natural abundance samples. Furthermore, the whole validation procedure was conducted at 293 K unlike widely used chemical shift calculation at 0 K using the GIPAW method. This combined method was demonstrated on monoclinic l-histidine.

Orientationally-dependent interactions such as dipolar coupling, quadrupolar coupling, and chemical shift anisotropy (CSA) contain a wealth of spatial information that can be used to elucidate molecular conformations and dynamics. To determine the sign of the chemical shift tensor anisotropy parameter (δaniso), both the |m| ​= ​1 and |m| ​= ​2 components of the CSA need to be symmetry allowed, while the recoupling of the |m| ​= ​1 term is accompanied with the reintroduction of homonuclear dipolar coupling components. Therefore, previously suggested sequences which solely recouple the |m| ​= ​2 term cannot determine the sign a 1H's δaniso in a densely-coupled network. In this study, we demonstrate the CSA recoupling of strongly dipolar coupled 1H spins using the Cnn/1(9003601805400360180900) sequence. This pulse scheme recouples both the |m| ​= ​1 and |m| ​= ​2 CSA terms but the scaling factors for the homonuclear dipolar coupling terms are zeroed. Consequently, the sequence is sensitive to the sign of δaniso but is not influenced by homonuclear dipolar interactions.

Dioxins are a general term for polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). Their structures consist of two chlorinated rings. Many congeners differ in terms of number of chlorine atoms and binding sites (Fig. 1). These substances are considered as persistent organic pollutants (POPS) due to their presence in the environment and the health risks associated. A World Health Organization (WHO) study has demonstrated the health risks (carcinogenic and immunotoxic) when population are exposed to them. In addition, dioxins have been regulated by the Stockholm convention on POPs in May 2001. In particular, 17 substances have to be monitored because they are regulated (7 PCDDs and 10 PCDFs). The highest toxic compound is the 2378-TeCDD. Currently, dioxins analysis can be done not only using GC-HRMS but also with GC-MS/MS according to European commission regulation (EU644/2017). Especially, GC-triple quadrupole MS is interesting in terms of handling, instrument size and operating costs. Recently, JEOL has developed a new GC-triple quadrupole MS (JMS-TQ4000GC) and a new dedicated dioxins analysis software called TQ-DioK. In this study, we evaluated JMS-TQ4000GC with TQ-DioK using dioxins standard samples.

JEOL 2mm MAS probe enables MA Spinning at nearly twice MAS speed of the conventional 3.2mm and 4mm MAS probe with 20 times the sample volume of the 1mm MAS probe. An attractive application of the 2mm MAS probe is 19F NMR. Strong 19F homonuclear dipolar coupling and wide chemical shift range cause a series of spinning side band (SSB) which make it difficult to analyze 19F spectra obtained by using the conventional 3.2mm and 4mm probes. The 2mm probe can achieve 40kHz MAS speeds, the resulting 19F spectra will had small well managed SSB’s. Here, we introduce 19F solid state NMR spectra of Nafion known as a solid polymer electrolyte for fuel cells. Fig.1 shows 19F MAS spectra of Nafion at various MAS speeds. 40kHz MAS gives a clear 19F spectrum without overlapping of SSBs whereas overlap occur between center bands and their SSBs at MAS speeds less than 40kHz. Moreover, the much greater sensitivity of the 2mm probe than the 1mm probe enables direct observation of low sensitive nuclei such as 13C. Thus, 13C{19F} CPMAS( Fig.2) and 13C-19F 2D-HETCOR (Fig.3) can easily be obtained.

JEOL 2mm HXMAS probe is a multi-use probe capable of high speed magic angle spinning (MAS) up to 40kHz and high sensitivity measurements. It is not only available for general use in standard 13C measurements of organic materials, but also for highly sensitive 1H indirect detection utilizing high resolution 1H NMR. Since it is also suitable for 19F measurements where spinning side bands are likely to appear (JEOL application note: NM180013 ) and MQMAS measurements of quadrupole nucleus, the 2mm probe is strongly recommended probe that can handle a variety of measurements as a single probe.

Analysis of Pesticides in Spinach Purchased from Local Grocers Using Triple-Quadrupole GC-MS/MS Analysis

Analysis of Pesticides in Kale Purchased from Local Grocers Using Triple-Quadrupole GC-MS/MS Analysis

Analysis of Pesticides in Honey Using QuEChERS Extraction and Triple-Quadrupole GC-MS/MS Analysis

JEOL NMR systems have had all FDA 21 CFR Part 11 support functions available in the standard Delta software since version 4.3 was released in 2004. All newer versions of the software have maintained and added to this functionality.

JEOL offers a full range of Magic-Angle-Spinning (MAS) probes and tools matched to a wide variety of solid-state NMR applications. JEOL MAS probes feature sample tube diameters to match the user sample and sensitivity needs. JEOL narrow bore MAS probes offer improved stability for high-speed spinning or for very large volumes. The JNM-ECZ Series NMR Spectrometer automatically updates the relevant spectrometer settings for all NMR probes for fast and easy switching between solids and liquids NMR operation.