Aloe Vera and Nopal mucilage on the reduction of agglomeration during spray drying and storage of blackberry and raspberry extracts.

The objective of this investigation was to evaluate the influence of two carrier agents, Nopal and Aloe Vera mucilage on the physicochemical properties and stability of blackberry and raspberry powders obtained by spray drying. A pilot scale spray dryer with a feed flow of 20 L/h and an atomization speed of 28,000 rpm was used. The inlet and outlet air temperatures were from 180 to 80°C, respectively. Yield, moisture content, water activity, hygroscopicity index, solubility time, volumetric density, stability diagrams, micrographs, and particle temperature were evaluated. The highest yields for blackberry extract were 75% with a concentration of 2.5% (w/v) Nopal mucilage, while raspberry extract yielded 65% with a concentration of 5% (w/v) Nopal mucilage. The increase in the concentration of the carrier agent presented an increase in the values of humidity, water activity, volumetric density, and solubility when Nopal mucilage was used as a carrier agent in both blackberry and raspberry extracts. Furthermore, when Aloe Vera mucilage was used as a carrier agent, these same values decreased with increasing concentration. The storage conditions of the powders obtained should be stored at temperatures below 20°C and water activities below 0.4. In addition, the stability diagrams show the particle conditions that should not be exceeded during spray drying.

Quantifying the operation of sinusoidal mass filters.

Even though sinusoidal quadrupole mass filters have been around for more than 50 years, the relationships defining resolution, resolving power, and transmission from the applied voltages have not been rigorously quantified or discussed. Traditional quadrupole mass filter theory implies that voltages are scanned at constant direct current (DC) to alternating current (AC) voltage ratios with the scanline passing through the origin of the voltage stability diagram. A prominent feature of constant voltage ratio scans is constant baseline theoretical resolving power (m/Δm) that is the same for all masses. Commercial quadrupole instruments rarely scan at constant resolving power because ion transmission increases with mass. Instead, they scan at constant resolution, meaning that the mass window width is fixed. Constant resolution mass scans are preferred because ion transmission does not change with mass. Commercial mass filter systems create constant resolution scans by linearly changing the DC and AC voltages at a fixed ratio in the presence of an additional negative DC voltage offset. This manuscript systematically quantifies the effects of the DC and AC voltages on resolution, resolving power, pseudopotential well depth, and transmission. To quantify these properties, recently developed spreadsheet tools that calculate the laboratory frame stability of ions from the matrix solutions of Hill's equation were used. Voltage scanning methods and their effects on theoretically determined transmission and sensitivity will be discussed.

Computational evaluation of a new digital tandem quadrupole mass filter.

A tandem mass filter consists of two low-resolution mass filters arranged in series that operate with a small offset between their mass windows. In principle, the overlap of the two individual mass windows defines the tandem window. Tandem operation provides improved resolution and transmission compared to a single mass filter operated with the same mass window. The improvement in transmission is owed to the larger acceptance of the low-resolution quadrupoles. The tandem filter resolution and transmission are adjusted by changing the amount of offset separating the mass windows of the individual filters. Sine wave systems create this offset through voltage changes. Digital tandem mass filters depart from convention because they do not change voltage. The tandem mass window is created when the individual filters are operated with two slightly different duty cycles. Both quadrupoles operate at the same frequency, phase, and voltage. When the frequency, phase, and voltage of each quadrupole are identical, there theoretically are no changes to the Mathieu parameters to cause ion excitation and loss during transition between the quadrupole pair. The work presented here shows that a fixed AC voltage digital tandem mass filter can only operate in higher stability zones. However, unlike sine mass filters, the mass range of a digital system is not limited. This makes the digital tandem mass filter feasible as a commercial product. For the tandem digital mode to be successful, the duty cycles of each quadrupole must be precisely controlled because the duty cycle differences required to shift the mass windows are small. The creation of these mass window offsets requires waveform generation that can obtain high duty cycle resolution. Our method of generating waveforms can meet this demand; however, modifications to our current printed circuit board must be made. These modifications are minor and will be discussed.

Digital Waveform Technology and the Next Generation of Mass Spectrometers.

Ion traps and guides are integral parts of current commercial mass spectrometers. They are currently operated with sinusoidal waveform technology that has been developed over many years. Recently, digital waveform technology has begun to emerge and promises to supplant its older cousin because it presents new capabilities that result from the ability to instantaneously switch the frequency and duty cycle of the waveforms. This manuscript examines these capabilities and reveals their uses and effects on instrumentation. Graphical Abstract ᅟ.

Digital mass filter analysis in stability zones A and B.

Digitally driven mass filter analysis is an advancing field. This work presents a tutorial of digital waveforms, stability diagrams, and pseudopotential well plots. Experimental results on digitally driven mass filter analysis in stability zones A and B are also shown. This work explains duty cycle manipulation of the waveforms to axially trap and eject ions from linear quadrupoles and how to change and distort the stability diagrams to create mass filters and their effects on the pseudopotential well depth. It discusses the sensitivity and resolution that can be obtained and what limits these benchmarks. It reveals the advantages of mass filter operation without any added direct current potential between the quadrupole electrodes (a = 0).