Planar microcoils with diameter ranging from 20 to 1000 μm I.D. (130–1130 μm O.D.) are evaluated for their applications in NMR spectroscopy. The coils are first overfilled with a standard sucrose solution and compared against each other. Coils with smaller I.D. (≤100 μm) perform extremely well. One hypothesis is that as the coils get smaller the volume occupied by the copper turns increases relative to the open I.D.; as such a large proportion of the sample is brought in close proximity to the coil turns and likely gives rise to strong sample–coil magnetic coupling, which increases the signal. The applications of the planar microcoils are demonstrated on Cypselurus poecilopterus (fish) and Daphnia magna (water flea) eggs. A single D. magna egg on a 50 μm coil yielded at least 3000 times the mass sensitivity (∼9,000,000 time saving) when compared to a 5 mm probe. This value could be at least 4 times higher if the B₁ homogeneity of the coils could be improved. With the current design, 80% of the signal is lost in multiple pulse experiments that rely on phase inversion and signal cancellation between scans. The data were extrapolated to predict that biological samples as small as ∼4 μm may become accessible via planar microcoil designs. To fulfill their potential for in situ metabolic screening, specialized magnetic susceptibility matched sample holders that restrict the sample to the homogeneous B₁ field region (i.e. within the 90% RF field) of the coil and advanced experiments that narrow spectral lines, suppress lipids and disperse signals into multiple dimensions will be required.

中文翻译：

---

使用微线圈NMR进行单卵毒性筛选

评估直径范围从20到1000μmID（外径130-1130μm）的平面微线圈在NMR光谱中的应用。首先将线圈用标准蔗糖溶液过度填充，然后进行比较。内径较小（≤100μm）的线圈性能非常好。一种假设是，随着线圈变小，铜匝所占的体积相对于开路内径增加；反之，则减小。因为如此大比例的样品被放置在靠近线圈匝的地方，并且可能引起强大的样品-线圈磁耦合，从而增加了信号强度。平面微线圈在鱼（Cypselurus poecilopterus）（鱼）和蚤（Daphnia magna）（水蚤）卵上的应用得到了证明。单个D. magna与5 mm探针相比，在50μm线圈上的鸡蛋产生的质量灵敏度至少是其3000倍（节省约9,000,000的时间）。如果可以改善线圈的B ₁均匀性，则该值至少可以高出4倍。使用当前的设计，在依赖于两次扫描之间的相位反转和信号消除的多脉冲实验中，有80％的信号丢失。外推数据可预测通过平面微线圈设计可获取小至约4μm的生物样品。为了发挥其原位代谢筛选的潜力，专门的磁化率与样品架匹配，将样品限制在均匀的B ₁场区域（即 在90％的RF磁场范围内）和先进的实验，这些实验需要缩小光谱线，抑制脂质并将信号分散到多个维度。