Molar Mass and Molar Mass Distribution of Polystyrene Particle Size Standards

Abstract

Monodisperse polystyrene microspheres and nanospheres are often used as particle size standards for calibration of size-measuring instruments. They are potentially useful as the mass standards for particle mass spectrometry as well. We demonstrated in this work that it is possible to achieve high-precision mass determination for single polystyrene spheres using a quadrupole ion trap. We introduced the particles into the trap by laser-induced acoustic desorption and probed them with light scattering. Mass-to-charge ratios of the individual particles were determined from applied trap-driving frequencies, voltage amplitudes and the observed starlike oscillatory trajectories projected on the radial plane. Creation of one-electron differentials through charge-state changes by electron bombardment allowed determination for the absolute mass of a single trapped particle to a precision better than 0.1%. Both molar mass and molar mass distribution were deduced from a large number of measurements for NIST polystyrene particle size standards (SRMs 1690 and 1691). Our results are in excellent agreement with the size measurement for the 0.895-microm spheres (NIST SRM 1690), but a small discrepancy (4%) in number-average mass was found for the 0.269-microm spheres (NIST SRM 1691).

Quantitative Evaluation of Sonophoresis Efficiency and Its Dependence on Sonication Parameters and Particle Size

“…High‐frequency ultrasound has been shown to be effective for low‐molecular‐weight drugs (<500 Da) across human skin, whereas low‐frequency ultrasound is up to 3 orders of magnitude more effective at increasing skin penetration, such as for interferon‐γ (17 kDa) and erythropoietin 48 (kDa) 8 . The molecular weights of the 60‐, 220‐, and 840‐nm polystyrene nanospheres used in our experiment are 7.15 × 10 7 , 3.53 × 10 9 , and 1.69 × 10 11 kDa, respectively 18 . The discrepancy may have been due to the preexisting pores in the porcine ear skin specimens (≈100 μm, which were much larger than the holes produced by bubble cavitation [1–3 μm 39 ] and sweat pores [≈20 nm]), long continuous sonication, and less interaction of the polystyrene materials with the biological tissue.…”

“…For 60‐nm nanoparticles, the transdermal penetration efficiency increased from 28.0% ± 2.3% at the 7‐minute sonication to 62.6% ± 5.4% at the 30‐minute sonication. For even submicrometer particles (840 nm, whose molecular weight is ≈1.69 ± 1011 Da), 18 satisfactory results could also be obtained after the 30‐minute sonication (11.9% ± 1.1%). In addition, the temperature elevations in all conditions were less than 2°C as measured by a thermocouple (diameter, 0.5 mm) attached to the skin specimen and a thermometer (Omega, Stamford, CT) during the experiment, which were similar to the findings for sonication by 10 MHz over 2 hours 19 .…”

“…8 The molecular weights of the 60-, 220-, and 840-nm polystyrene nanospheres used in our experiment are 7.15 × 10 7 , 3.53 × 10 9 , and 1.69 × 10 11 kDa, respectively. 18 The discrepancy may have been due to the preexisting pores in the porcine ear skin specimens (≈100 μm, which were much larger than the holes produced by bubble cavitation [1-3 μm 39 ] and sweat pores [≈20 nm]), long continuous sonication, and less interaction of the polystyrene materials with the biological tissue. Hair removal (ie, using cream), which could enhance the efficiency of transdermal drug delivery substantially, as shown in this study, is not prohibited in clinics.…”

Wavelet-Based Method for Time-Domain Noise Analysis and Reduction in a Frequency-Scan Ion Trap Mass Spectrometer

“…In previous experiments [24,28], we reported the development of a new type of mass spectrometry for rapid measurement of the masses and the mass distributions of cells and polystyrene microparticles by measuring mass-tocharge ratio (m/Ze) and charge (Z) simultaneously using a charge-sensitive detector. Figure 1a shows a schematic diagram of the experimental setup, in which a 0.4-mm-thick antimony-doped single-crystal silicon (100) wafer was used as the target plate.…”

“…We know of no methods reported to remove the N RF (t) due to coupling of S x (t) with the rf driving voltage. Here, we present an OWPD method to achieve the task and show that N RF (t) is the dominant noise in the mass spectra obtained with LDCD-ITMS [22][23][24][25][26][27][28][29]. The removal of N RF (t) is critically important in our application of the LDCD-ITMS technique to measure the masses of nanometer-sized particles, of which higher rf frequencies are required for the trapping.…”