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PubMed1998

Particle size distributions from multiparticulate dissolution.

It has been demonstrated theoretically that the particle size distribution of particles in a given sieve fraction of a powder may be assessed by means of short-term dissolution data. Theoretical considerations in this article show that by accounting for polydispersity in a powder sample, the cubic expression in time for amount undissolved and fraction undissolved gives rise to integrals that are essentially moments of the distribution function of one of the defining dimensions of the particle. The first and the second moments can be used to calculate the distribution parameters, (mean and standard deviation) of such a dimension of a crystalline powder. The theory is based on a model geometry, a parallelepiped, for the description of particles such as needles, plates, and prisms. The theory is substantiated by experimental data. A method for obtaining the particle size distribution parameters from the results of dissolution of three sieve fractions of oxalic acid dihydrate, and the general application of this to particle size determination is discussed. To validate the method, the distribution of lengths and breadths of oxalic acid dihydrate particles was obtained from microscopy. From actual powder dissolution data, an estimate of the mean height-to-breadth ratio of these particles belonging to a certain sieve fraction was obtained. With the knowledge of the dissolution rate constant, K, for oxalic acid dihydrate under specified hydrodynamic conditions, it was possible to evaluate the moments of the distribution function. The distribution parameters so obtained were in good agreement with the results obtained from microscopy.

Crystallization↗

PubMed1998

Light-scattering method in particle size analysis of parenteral emulsions.

The use of a light-scattering particle size distribution analyzer has been shown to be a convenient method for characterizing the particle size distribution of parenteral emulsions. However, the concentrations of the samples used were found to have a major impact on the particle size distribution results, particularly for samples with a mean particle size smaller than 0.2 micron. An increase in sample concentration caused a shift to smaller particle sizes as a result of multiple scattering. The blue-light (tungsten lamp) intensity, instead of the He-Ne laser integrity, should be used to control sample concentration within the optimal range for measurement.

Emulsions↗

PubMed1988

Estimation of mean and median particle size of ruminant digesta.

An alternative exponential equation with a parameter as an exponent was compared to a recently published exponential procedure for estimating mean and median particle size. Both equations were fit to literature values for particle size distributions of esophageal extrusa, rumen digesta, and feces. In addition, 112 observations of particle-size distributions of esophageal extrusa were fit to both equations for comparison. Both equations gave adequate fits of rumen digesta and feces, but the earlier model was biased by regular deviations from observed data for esophageal extrusa. Use of the previously published model overestimated mean particle size in esophageal extrusa from 4.5 to 10.3%. Median particle size was underestimated from 4.9 to 5.6%. Analytic solutions exist for mean and median particle sizes for the earlier model, but it is necessary to estimate numerically the mean and median particle sizes when using the proposed equation. Even though the solution for the proposed equation must be determined numerically, it will prevent bias between experimental treatments, give more accurate estimates of mean and median particle size, and result in a lower residual sums of squares. In addition, a single equation can be used to model particle size reduction throughout the digestive tract.

Animals↗

PubMed1992

Fat emulsion particle-size distribution in total nutrient admixtures.

The fat particle-size distribution in and physical stability of two commercially available lipid emulsions before and after their use in total nutrient admixtures (TNAs) are reported. Four TNAs without electrolytes and four TNAs with electrolytes were prepared; each type of TNA was prepared with Liposyn II and with Intralipid. Particle size was measured in the < 1-micron range by using photon correlation spectroscopy and in the 2-60-microns range by using light blockage. Admixtures with or without electrolytes were stored for two or nine days at 4 degrees C followed by one day at 25 degrees C. For the fraction of fat particles of < 1 micron in diameter, Intralipid and Liposyn II had a mean particle size of 374 and 313 nm, respectively. The admixtures containing electrolytes showed a decrease in mean particle size of about 7%. Admixtures with Intralipid contained 2 x 10(7) particles larger than 2 microns per milliliter (1.7% of total fat), compared with 1 x 10(6) particles per milliliter (0.05-0.15% of total fat) for admixtures with Liposyn II. The addition of electrolytes increased the particle counts for Liposyn II-containing admixtures. Upon storage, Intralipid-containing admixtures with electrolytes showed an initial increase followed by a decrease in the mean diameter of particles of < 1 micron. All the admixtures were stable in terms of pH and visual appearance. Intralipid-containing admixtures with electrolytes showed a decrease in the number of particles in the 2-60-microns size range, while Liposyn II-containing admixtures with electrolytes showed an increase.(ABSTRACT TRUNCATED AT 250 WORDS)

Drug Incompatibility↗

PubMed2001

Screening of soil evidence by a combination of simple techniques: validity of particle size distribution.

The validity of the determination of particle size distribution for forensic soil identification was studied using 73 soil samples collected from a 20 km x 15 km area. Soil particles were first divided into two fractions by wet sieving with a sieve with a 0.05 mm aperture size. Dry sieving was used to analyze the coarse particle fraction and a particle size analyzer was used for the fine particle fraction. The number of particle size classes measured by sieving could be reduced to three, <0.05, 0.05-0.2, and 0.2-2 mm, which enabled 87.9% of the soil samples to be discriminated. Measurements made with the particle size analyzer on the fine particle fraction increased the discriminating power to 95.9%. The use of particle size analysis by sieving in combination with color examination allowed us to discriminate 99.5% of the soil samples, even when particle size analysis of the fine particle fraction was not carried out.

Forensic Medicine↗

PubMedDate not supplied

Evaluation of macroaggregated albumin particle sizes for use in pulmonary shunt patient studies.

OBJECTIVE: To assess commercial macroaggregated albumin (MAA) reagent kits for compliance with particle-size parameters needed for proper clinical evaluation of pulmonary shunts (right-to-left). DESIGN: Comparative trial. SETTING: Nuclear pharmacy (laboratory setting). PATIENTS AND OTHER PARTICIPANTS: Not applicable. INTERVENTIONS: Minimally, 90% of the particles contained within an MAA reagent kit should be within the 10 to 90 microns range with minimal variation in particle size distribution and as few small particles (i.e., < 10 microns) as possible. Five separate vials from five commercial brands of MAA reagent kits were obtained, and 500 to 517 particles were analyzed for each sample. An additional study was performed on one of the MAA reagent kit brands, using five vials from each of five different lot numbers to determine the variability between lots. MAIN OUTCOME MEASURES: Long axis (maximum, micron), short axis (minimum, micron), and the area (micron 2) of each MAA particle. RESULTS: One MAA brand had the lowest percentage of unacceptable MAA particle sizes and maintained consistent particle sizes between vials. However, the same MAA reagent kit brand showed that only two of five lots had a low percentage of MAA particle sizes below the 10-micron limit. CONCLUSION: Particle sizes varied among the five different brands of MAA reagent kits, as did different lots of the best-performing kit. This variability in particle sizes may affect the accuracy and reproducibility of pulmonary shunt patient studies.

Humans↗

PubMed1996

Guidance in the setting of drug particle size specifications to minimize variability in absorption.

PURPOSE: To provide guidance in setting particle size specifications for poorly soluble drugs to minimize variability in absorption. METHODS: A previously reported computer method was used to simulate the percent of dose absorbed as a function of solubility, absorption rate constant, dose, and particle size. RESULTS: The simulated percent of dose absorbed was tabulated over a realistic range of solubilities, absorption rate constants, and doses using drug particle sizes that might be typically found in a dosage form. CONCLUSIONS: The greatest effect of particle size on absorption was simulated for low dose- low solubility drugs. In general, the sensitivity of absorption to particle size decreased with increasing dose or solubility. At a solubility of 1 mg/mL, particle size had practically no effect on the percent of dose absorbed over the range of doses simulated (1-250 mg).

Computer Simulation↗

PubMed2001

Lipid particle size effect on water vapor permeability and mechanical properties of whey protein/beeswax emulsion films.

Lipid particle size effects on water vapor permeability (WVP) and mechanical properties of whey protein isolate (WPI)/beeswax (BW) emulsion films were investigated. Emulsion films containing 20 and 60% BW (dry basis) and mean lipid particle sizes ranging from 0.5 to 2.0 microm were prepared. BW particle size effects on WVP and mechanical properties were observed only in films containing 60% BW. WVP of these films decreased as lipid particle size decreased. As drying temperature increased, film WVPs decreased significantly. Meanwhile, tensile strength and elongation increased as BW particle size decreased. However, for 20% BW emulsion films, properties were not affected by lipid particle size. Results suggest that increased protein-lipid interactions at the BW particle interfaces, as particle size decreased and resulting interfacial area increased, result in stronger films with lower WVPs. Observing this effect depends on a large lipid content within the protein matrix. At low lipid content, the effect of interactions at the protein-lipid interfaces is not observed, due to the presence of large protein-matrix regions of the film without lipid, which are not influenced by protein-lipid interactions.

Animals↗

PubMed2006

Relationship of low-density lipoprotein particle size to insulin resistance and intima-media thickness in nondiabetic Koreans.

The aim of this study was to investigate whether low-density lipoprotein (LDL) particle size is associated with insulin resistance and to explore the association between LDL particle size and preclinical atherosclerosis in nondiabetic Korean population. We measured the carotid intima-media thickness (IMT), LDL particle size, and insulin resistance in 136 nondiabetic subjects. Low-density lipoprotein particle size was significantly correlated with insulin resistance, but the independent risk factors of LDL particle size determined by the multiple regression analysis were age, triglyceride, and high-density lipoprotein cholesterol (HDL-C). Carotid IMT was associated with traditional risk factors of atherosclerosis, which are age, HDL-C, LDL cholesterol, systolic and diastolic blood pressure, but LDL particle size was not correlated with carotid IMT. We conclude that LDL particle size was associated with insulin resistance, but age, triglyceride, and HDL-C contributed independently to the variability in LDL particle size, and LDL particle size was not a predictor of preclinical atherosclerosis in nondiabetic Koreans.

Adult↗

PubMed2005

Particle size and surface charge affect particle uptake by human dendritic cells in an in vitro model.

Current vaccine development includes optimization of antigen delivery to antigen presenting cells, such as dendritic cells (DC). Particulate systems have attracted increasing attention in the development of vaccine delivery systems. In the present study, we investigated DC uptake of model fluorescent polystyrene particles with a broad size range and variable surface properties. Localization of particles was investigated using confocal laser scanning microscopy and uptake was quantified by flow cytometry. Immature DC were generated from mononuclear cells isolated from human blood. The polystyrene particles interacted with the DC throughout the tested diameter range of 0.04-15 microm in a time- and concentration-dependent manner. The optimal particle diameter for fast and efficient acquisition by a substantial percentage of the DC was 0.5 microm and below. The surface of 1 and 0.1 microm polystyrene particles was covalently modified with different polyaminoacids/proteins, yielding particles with varying surface charge. Uptake of 1 microm particles was greatly enhanced when particles displayed a positive surface charge. In general, the present findings establish that particle diameters of 0.5 microm and below were optimal for DC uptake; however uptake of larger particles could be greatly enhanced by rendering the particle surface positive. Whether increased particle uptake is correlated with increased immune responses, remains to be established.

Chemical Phenomena↗

PubMed1995

Effects of particle size and pelleting on growth performance, nutrient digestibility, and stomach morphology in finishing pigs.

The effects of particle size and pelleting on growth performance, carcass characteristics, nutrient digestibility, and stomach morphology were determined using 160 finishing pigs. The pigs were fed a corn-soybean meal-based diet with the corn milled to particle sizes of 1,000, 800, 600, or 400 microns. The diets were fed in meal or pellet form. Pelleting the diets resulted in 5% greater ADG (P < .01) and 7% greater grain/feed (P < .001). Also, pelleting increased digestibilities of DM, N, and GE by 5 to 8% (P < .001). Reducing particle size increased electrical energy required for milling and decreased milling production rates, especially as particle size was decreased from 600 to 400 microns. Reducing particle size of the corn from 1,000 to 400 microns increased gain/feed by 8% (linear effect, P < .001) and digestibility of GE by 7% (quadratic effect, P < .03). Improved nutrient digestibility and lower ADFI resulted in 26% less daily excretion of DM and 27% less daily excretion of N in the feces as particle size was reduced from 1,000 to 400 microns (linear effects, P < .001). Stomach lesions and keratinization increased with reduced particle size (P < .003) and keratinization increased with pelleting (P < .02), although they were unrelated to growth performance (i.e., gain/feed actually improved as lesion scores increased). Considering milling energy, growth performance, stomach morphology, nutrient digestibility, and nutrient excretion, a particle size of 600 microns, or slightly less, is an acceptable compromise for corn in both meal and pelleted diets for finishing pigs.

Animal Feed↗

PubMed2000

Chemical precipitation of apolipoprotein B-containing lipoproteins facilitates determination of LDL particle size.

OBJECTIVES: To simplify the determination of low-density lipoprotein (LDL) particle size by eliminating the need for ultracentrifugation. DESIGN AND METHODS: We compared LDL particle size determination by gradient gel electrophoresis using two different methods for separation of LDL: (a) by ultracentrifugation with a density between 1.019 and 1.063 g/mL, and (b) by precipitation of the apolipoprotein B-containing lipoproteins from plasma. LDL particle size was determined for 41 individuals using both methods. RESULTS: The correlation between these two methods was r = 0.98; peak particle diameter (nm) was reproducible with a coefficient of variation of 1. 3% for LDL separated by ultracentrifugation and 1.4% for LDL prepared by precipitation. The intra-assay variation within a single gel was 0.2%. CONCLUSION: Elimination of the need for ultracentrifugation or lipid staining significantly reduces the cost and simplifies the procedure of LDL particle sizing. As a result, larger patient populations can be more readily screened for the determination of LDL particle size.

Adult↗

PubMed2002

Does a powder surface contain all necessary information for particle size distribution analysis?

The aim of this study was to utilise a new approach where digital image information is used in the characterisation of particle size distributions of a large set of pharmaceutical powders. A novel optical set-up was employed to create images and calculate a stereometric parameter from the digital images of powder surfaces. Analysis was made of 40 granule batches with varying particle sizes and compositions prepared with fluidised bed granulation. The extracted digital image information was then connected to particle size using multivariate modelling. The modelled particle size distributions were compared to particle size determinations with sieve analysis and laser diffraction. The results revealed that the created models corresponded well with the particle size distributions measured with sieve analysis and laser diffraction. This study shows that digital images taken from powder surfaces contain all necessary data that is needed for particle size distribution analysis. To obtain this information from images careful consideration has to be given on the imaging conditions. In conclusion, the results of this study suggest that the new approach is a powerful means of analysis in particle size determination. The method is fast, the sample size needed is very small and the technique enables non-destructive analysis of samples. The method is suitable in the particle size range of approximately 20-1500 microm. However, further investigations with a broad range of powders have to be made to obtain information of the possibilities and limitations of the introduced method in powder characterisation.

Particle Size↗

PubMed2005

Use of mineral magnetic concentration data as a particle size proxy: a case study using marine, estuarine and fluvial sediments in the Carmarthen Bay area, South Wales, U.K.

Compositional (non-magnetic) data can correlate strongly with particle size, which deems it appropriate as a particle size proxy and, therefore, a reliable means of normalising analytical data for particle size effects. Previous studies suggest magnetic concentration parameters represent an alternative means of normalising for these effects and, given the speed, low-cost and sensitivity of the measurements may, therefore, offer some advantages over other compositional signals. In this work, contemporary sediments from a range of depositional environments have been analysed with regard to their mineral magnetic concentration and textural characteristics, to observe if the strength and nature of the relationship identified in previous studies is universal. Our data shows magnetic parameters (chi(LF), chi(ARM) and SIRM) possess contrasting relationships with standard textural parameters for sediment samples collected from marine (Carmarthen Bay), estuarine (Gwendraeth Estuary) and fluvial (Rivers Gwendraeth Fach and Gwendraeth Fawr) settings. Magnetic concentrations of sediments from both the marine and estuarine environments are highly influenced by the magnetic contribution of finer particle sizes; Gwendraeth Fawr River sediments are influenced by the magnetic contribution of coarser particle sizes, while sediments from the Gwendraeth Fach River are not influenced significantly by any variations in textural properties. These results indicate mineral magnetic measurements have considerable potential as a particle size proxy for particular sedimentary environments, which in certain instances could be useful for geochemical, sediment transport, and sediment provenance studies. However, the data also highlight the importance of fully determining the nature of the relationship between sediment particle size and magnetic properties before applying mineral magnetic data as a particle size proxy.

Aluminum Silicates↗

PubMed2005

A new approach in the prediction of the dissolution behavior of suspended particles by means of their particle size distribution.

Though various attempts have been made in literature to model the particle size distribution of an active pharmaceutical ingredient (API) in function of the required release profile of the pharmaceutical product, so far one has not succeeded to develop a universal approach in the correlation of particle size distribution and in vitro dissolution data. In this publication, a new approach is presented on the use of particle size distribution data in the prediction of the in vitro dissolution profile of a suspension formulation. For this purpose, various theoretical experiments were done simply on paper and based on the Noyes-Whitney [A.A. Noyes, W.R. Whitney, J. Am. Chem. Soc. 19 (1897) 930-934] equation, the normalized dissolution profiles of various imaginary size distributions were calculated. For each size distribution, its weighted mean diameters were then calculated. Based on these theoretical data, a model could be developed which scientifically explains the dissolution profile of a suspension in function of its volume-weighted mean particle size (D[4, 3]). The applicability of this correlation model could experimentally be confirmed by evaluation of laser diffraction and in vitro dissolution data as they were obtained for different batches of a suspension formulation. This new approach in the correlation between particle size and dissolution may be an important analytical tool in the engineering of the particle size distribution of drug substance, and more precisely monitoring the D[4, 3] volume-weighted mean diameter may allow one to model the dissolution profile of a suspension formulation and thereby its in vivo release profile.

Algorithms↗

PubMed2003

A computational model for particle size influence on drug absorption during controlled-release colonic delivery.

The effect of particle size on the percent drug absorbed is computationally modeled for controlled-release dosage forms that deliver drug particles to the colon. The relative benefit of reducing particle size is mapped on a diagram of the drug's absorption rate constant (estimated from rat intestinal perfusion, CACO-2 or human intubation permeation rates) versus the drug's solubility. Some drugs fall into a limit of high percentage absorption even with large particles such that particle size reduction has little impact. Another group of drugs is solubility limited such that even with small particles, absorption is negligible. Between the two regions, only drugs with sufficiently high absorption rates are influenced by the drug dissolution rate and thereby the particle size. The size of this region is a function of dosing rate. Comparisons between calculated particle size effects on colon absorption as a function of colon volume suggest caution when using animal models to predict bioavailability from colonic drug delivery. This volume dependence also suggests that the particle size influence will vary as a function of the digestive cycle.

Colon↗

PubMed1998

The application of multiple linear regression to the measurement of the median particle size of drugs and pharmaceutical excipients by near-infrared spectroscopy.

A number of powdered drugs and pharmaceutical excipients were used to demonstrate the ability of near-infrared spectroscopy to measure median particle size (d50). Sieved fractions and bulk samples of aspirin, anhydrous caffeine, paracetamol, lactose monohydrate and microcrystalline cellulose were particle sized by forward angle laser light scattering (FALLS) and scanned by fibre-optic probe FT-NIR spectroscopy. Two-wavenumber multiple linear regression (MLR) calibrations were produced using: NIR reflectance; absorbance and Kubelka-Munk function data with each of median particle size, reciprocal median particle size and the logarithm of median particle size. Best calibrations were obtained using reflectance data versus the logarithm of median particle size (NIR predicted lnd50 versus ln(FALLS d50) for microcrystalline cellulose and lactose monohydrate sieve fraction calibrations: r = 0.99 in each case). Working calibrations for lactose monohydrate (median particle size range: 19.2-183 microns) and microcrystalline cellulose (median particle size range: 24-406 microns) were set-up using combinations of machine sieve-fractions and bulk samples. This approach was found to produce more robust calibrations than just the use of sieved fractions. The method has been compared with single wavenumber quadratic least squares regression using reflectance and mean-corrected reflectance data with median particle size. Correlation between NIR predicted and FALLS values was significantly better using the MLR method.

Calibration↗

PubMed2002

Coagulation-flocculation of beech condensate: particles size distribution.

Beech wood (Fagus sylvatica L.) condensate from a steaming operation was studied. The objective of our work was to study the precipitation of these wood extracts in presence of calcium ion after autoxidation at basic pH (8). The autoxidation was carried out at 250 rpm for 30 min, and flocculation was followed up for 30 min. An investigation with a laser sizer Mastersizer of Malvern has been done in order to study the influence of the agitation on the state of aggregation of the condensate. A negative correlation was observed between the mean size of particles and the agitation rate. Without stirring, flocculation rapidly occurred and the mean size of particles was high. Calcium-induced aggregation of the condensate was also found to be reversible toward agitation.

Journal Article↗