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In environmental research, it is critical to understand how toxins impact invertebrate eggs and egg banks, which, due to their tiny size, are very challenging to study by conventional nuclear magnetic resonance (NMR) spectroscopy. Microcoil technology has been extensively utilized to enhance the mass-sensitivity of NMR. In a previous study, 5-axis computer numerical control (CNC) micromilling (shown to be a viable alternative to traditional microcoil production methods) was used to create a prototype copper slotted-tube resonator (STR). Despite the excellent limit of detection (LOD) of the resonator, the quality of the line shape was very poor due to the magnetic susceptibility of the copper resonator itself. This is best solved using magnetic susceptibility-matched materials. In this study, approaches are investigated that improve the susceptibility while retaining the versatility of coil milling. One method involves machining STRs from various copper/aluminum alloys, while the other involves machining ones from an aluminum 2011 alloy and electroplating them with copper. In all cases, combining copper and aluminum to produce resonators resulted in improved line shape and SNR compared to pure copper resonators due to their reduced magnetic susceptibility. However, the copper-plated aluminum resonators showed optimal performance from the devices tested. The enhanced LOD of these STRs allowed for the first 1 H- 13 C heteronuclear multiple quantum coherence (HMQC) of a single intact 13 C-labeled Daphnia magna egg (∼4 μg total biomass). This is a key step toward future screening programs that aim to elucidate the toxic processes in aquatic eggs.

Beryllium (Be) is still not well understood from a toxicological point of view, and studies that involve the determination of different Be compounds species in tissues need to be conducted. In this paper we describe the development and validation of reliable methods for the detection of ultra-trace levels of Be in various biological matrices. Blood and tissues (liver, lung, spleen, and kidney) were used in this study. The samples were digested with a mixture of nitric and perchloric acids for Be and BeAl and an addition of sulfuric acid was made for BeO. The solutions were analyzed by inductively coupled plasma mass spectrometry with (6)Li as internal standard. The detection limits are in the order of 0.02 ng/g for tissue and 0.03 ng/mL for blood, and were compared to existing reference methods. To our knowledge, this is the first study that assesses dissolution of the different Be compounds in biological matrices, while also undergoing a rigorous optimization and complete validation. This method has proven that it is reliable, among the most sensitive available in the literature, and that it can be used in trace toxicological studies for Be.