Frequency Of Sample Collection Research Articles

Ant Colony Based Artificial Neural Network for Predicting Spatial and Temporal Variation in Groundwater Quality

The quality of groundwater is of utmost importance, as it directly impacts human health and the environment. In major parts of the world, groundwater is the main source of drinking water, hence it is essential to periodically monitor its quality. Conventional water-quality monitoring techniques involve the periodical collection of water samples and subsequent analysis in the laboratory. This process is expensive, time-consuming and involves a lot of manual labor, whereas data-driven models based on artificial intelligence can offer an alternative and more efficient way to predict groundwater quality. In spite of the advantages of such models based on artificial neural network (ANN) and ant colony optimization (ACO), no studies have been carried out on the applications of these in the field of groundwater contamination. The aim of our study is to build an ant colony optimized neural network for predicting groundwater quality parameters. We have proposed ANN comprising of six hidden layers. The approach was validated using our groundwater quality dataset of a hard rock region located in the northern part of Karnataka, India. Groundwater samples were collected by us once every 4 months from March 2014 to October 2020 from 50 wells in this region. These samples were analyzed for the pH, electrical conductivity, Na+, Ca+, K+, Mg2+, HCO3−, F−, Cl− and U+. This temporal dataset was split for training, testing and validation of our model. Metrics such as R2 (Coefficient of Determination), RMSE (Root Mean Squared Error), NSE (Nash–Sutcliffe efficiencies) and MAE (Mean Absolute Error) were used to evaluate the prediction error and model performance. These performance evaluation metrics indicated the efficiency of our model in predicting the temporal variation in groundwater quality parameters. The method proposed can be used for prediction and it will aid in modifying or reducing the temporal frequency of sample collection to save time and cost. The study confirms that the combination of ANN with ACO is a promising tool to optimize weights while training the network, and for prediction of groundwater quality.

Equine blood cultures: Can we do better?

Blood culture is considered the gold standard test for documenting bacteraemia in patients with suspected bacterial sepsis in veterinary and human medicine. However, blood culture often fails to yield bacterial growth even though the clinical picture is strongly suggestive of bacterial sepsis, or contaminating organisms can overgrow the true pathogen, making accurate diagnosis and appropriate management of this life-threatening condition very challenging. Methodology for collecting blood cultures in equine medicine, and even in human hospitals, is not standardised, and many variables can affect the yield and type of microorganisms cultured. Microbiological culture techniques used in the laboratory and specific sample collection techniques, including volume of blood collected, aseptic technique utilised, and the site, timing and frequency of sample collection, all have substantial impact on the accuracy of blood culture results. In addition, patient-specific factors such as husbandry factors, the anatomical site of the primary infection, and changing microflora in different geographic locations, also can impact blood cultures. Thus, blood cultures obtained in practice may not always accurately define the presence or absence of, or specific organisms causing, bacteraemia in horses and foals with suspected sepsis. Erroneous blood culture results can lead to inappropriate antimicrobial use, which can result in poor outcomes for individual patients and contribute to the development of antimicrobial resistance in the patient's microflora and the environmental microcosm. This review summarises current indications and methodology, and specific factors that may be optimised, for equine blood culture, with particular focus on available literature from neonatal foals with suspected bacterial sepsis. To standardise and optimise blood culture techniques in horses and foals, future research in this area should be aimed at determining the optimal volume of blood that should be collected for culture, and the ideal site, timing, and frequency of sample collection.

Lessons learned from SARS-CoV-2 measurements in wastewater

Standardized protocols for wastewater-based surveillance (WBS) for the RNA of SARS-CoV-2, the virus responsible for the current COVID-19 pandemic, are being developed and refined worldwide for early detection of disease outbreaks. We report here on lessons learned from establishing a WBS program for SARS-CoV-2 integrated with a human surveillance program for COVID-19. We have established WBS at three campuses of a university, including student residential dormitories and a hospital that treats COVID-19 patients. Lessons learned from this WBS program address the variability of water quality, new detection technologies, the range of detectable viral loads in wastewater, and the predictive value of integrating environmental and human surveillance data. Data from our WBS program indicated that water quality was statistically different between sewer sampling sites, with more variability observed in wastewater coming from individual buildings compared to clusters of buildings. A new detection technology was developed based upon the use of a novel polymerase called V2G. Detectable levels of SARS-CoV-2 in wastewater varied from 102 to 106 genomic copies (gc) per liter of raw wastewater (L). Integration of environmental and human surveillance data indicate that WBS detection of 100 gc/L of SARS-CoV-2 RNA in wastewater was associated with a positivity rate of 4% as detected by human surveillance in the wastewater catchment area, though confidence intervals were wide (β ~ 8.99 ∗ ln(100); 95% CI = 0.90–17.08; p < 0.05). Our data also suggest that early detection of COVID-19 surges based on correlations between viral load in wastewater and human disease incidence could benefit by increasing the wastewater sample collection frequency from weekly to daily. Coupling simpler and faster detection technology with more frequent sampling has the potential to improve the predictive potential of using WBS of SARS-CoV-2 for early detection of the onset of COVID-19.

Quantitative analysis of amino acids by HPLC in dried blood and urine in the neonatal period: Establishment of reference values.

Quantitative analysis of amino acids in blood and urine is primarily indicated for the diagnosis of amino acid disorders. The high-performance liquid chromatography (HPLC) technique is frequently used for this detection. The frequency of sample collection on filter paper has been increasing exponentially, and there are many advantages attributed to processing biological samples in this way. The aim of this study was to validate a quantitative analysis of amino acids by HPLC in blood and urine collected on filter paper and to establish reference values in the neonatal period. Dried blood and dried urine samples of respectively 58 and 45 healthy newborns (2-9 days) were collected. Pre-treatment and extraction of samples were done according to the literature. Separation and analysis of amino acids were carried out by HPLC with fluorescence detection. The developed method demonstrated excellent separation, linearity, limits of detection and quantification, repeatability and recovery. The reference values for 17 amino acids were defined in dried blood and urine samples of newborns. This work presents a simple, fast and effective method for the simultaneous analysis of 17 amino acids in blood and urine collected on filter paper in a single run. The reference values were established and validated.

Development of a simple selection protocol for optimizing the harvest of mesenchymal stem cells from explanted human umbilical cord Wharton’s jelly

Background: Human umbilical cord Wharton's jelly (hUCWJ) derived Mesenchymal stem cells (MSCs) is a non-controversial, easily available source of human tissue which has a close association with embryonic tissue. Explant culture technique of isolating MSCs do not require any proteolytic enzymes giving an edge when compared to enzymatic methods.&#x0D; Aims and Objective: This study was designed to develop a suitable protocol to optimize the number of primary cells by transferring the explants after a successful migration and before trypsinizing of MSCs from primary culture plate to new culture plates.&#x0D; Materials and Methods: For defining the isolated cells as MSCs, the cells were studied by colony forming assay, semiquantitative two steps reverse transcriptase polymerase chain reaction (RT-PCR) and International Society for Cellular Therapy (ISCT) criteria to determine the purity of the lineage.&#x0D; Results: The explant cultured cells fulfil the defining criteria by ISCT. Further, they form colony and RT-PCR confirmed the presence of thy-1, endoglin and β-actin. The incubated explant shows successful cells migration after transferring from one culture plate to another for five consecutive times. Further, it was seen that the migrated cells can be cultured for more than 18 passages. However, a reduction was seen in the migration of the cells after the 3rd transfer of the explants.&#x0D; Conclusion: This study found that the transferred explant has the potential to yield cells for 5 consecutive explant transfers. Further, this technique optimized the yield of primary cells and thereby reducing the quantity and frequency of sample collection, processing time and cost.

Seasonal variability of phytoplankton in the shallow waters of the southern Baltic Sea

The Baltic Sea is characterized by a seasonal variation of phytoplankton structure. These organisms are particularly sensitive to changes in various environmental parameters. Cyclic, recurring annually fluctuation of species composition, abundance and biomass of phytoplankton is a consequence of these changes. Spatial and temporal variability of particular groups of phytoplankton is not the same in different areas of the Baltic Sea. The purpose of this work was to determine the spatial and temporal distribution of phytoplankton in three chosen areas of the coastal zone of the southern Baltic Sea (Ustka, Poddąbie and Rowy) in the period of November 2014 - September 2016. Mean values of abundance and biomass of phytoplankton for the surveyed areas were typical for this type of coastal waters. In each of the surveyed areas the same dominat species in terms of the abundance and biomass were observed. A growth of diatoms was recorded only in the area of Ustka, which could have been caused by the inflow of river waters. Seasonal surveys of phytoplankton indicated that in the case of the studies regarding this parameter – taxonomic composition, abundance and biomass in the same surveyed area were similar at the three research stations (e.g. 75-80%), depending on the season of the year. On this basis, it was concluded that, whether carrying out the monitoring of phytoplankton or planned investments, the sample collection frequency had a greater significance than the number of research stations.

Evaluation of performance of water quality models for a tropical lake system

AbstractThe ability to predict water quality is a major requirement for planning and execution of developmental projects. It helps entrepreneurs to effectively plan and implement pollution control measures. This study evaluates the ability of different water quality models (statistical; remote sensing; mathematical) to predict salinity in Akkulam–Veli Lake, a tropical lake system. The performance of these three water quality models was evaluated. Prediction of salinity was made accurately with the mathematical model (WASP), compared to the other models. WASP facilitates prediction of daily water quality variations, which is not possible with the other models. A limitation of this model, however, was its ability to predict only a few water quality parameters. The statistical methods are reliable when the number of sampling sites and frequency of sample collection are high, making this method exhaustive and expensive. Remote sensing techniques proved to be less tedious, but are suitable only under specific situations, and not able to produce a high level of accuracy. Nevertheless, this method provides a continuous picture of spatial variations of different water quality parameters to a reasonable level of accuracy. The choice of the ‘best’ model varies on the basis of climatic and field conditions of the lake system of concern. Thus, a combination of water quality models was found to be the most ideal approach for analysing water quality data.

How 'Optimal' are Optimal Sampling Times for Tyrosine Kinase Inhibitors in Cancer? Practical Considerations.

Tyrosine kinase inhibitors have been marketed as a fixed dose, 'one size fits all' treatment strategy. Physicians have also been interested in this method of dosing, knowing the complex planning of other current cancer therapies administered on a mg/m(2) or mg/kg basis and subsequent occurrence of dosing error or concern for underdosing. The 'simple and safe' strategy of a single dose of tyrosine kinase inhibitor for cancer has thus been widely adopted. However, the benefits purported to exist in the clinical trials do not appear to be borne out in clinical practice, particularly in solid tumours. In order to investigate whether pharmacokinetic variability is a contributor to the variable outcomes, pharmacokinetic targets to enable individualisation of tyrosine kinase inhibitor administration are now emerging. Evidence suggests there is not a clear relationship of a single dose to maximum plasma concentration (C max), steady-state trough concentration (C trough) or area under the curve (AUC). Furthermore, a significant number of questions remain related to the specific timing and frequency of sample collection required to achieve optimal outcomes. This article reviews the wide variability in the literature on this topic, specifically the different pharmacokinetic targets of the same drug for different cancers, for different states of cancer, and changing pharmacokinetic parameters over a treatment interval in cancer. It appears the optimal sampling times to enable appropriate dose recommendations across patients and diseases may vary, and are not always trough concentrations at steady state. Importantly, the need to be pragmatic in a clinical setting is paramount. Lastly, international collaborations to increase sample size are highly recommended to ensure enough patients are sampled to be sure of a clinical benefit from this concentration-directed methodology.

Reductions in urinary collection frequency for assessment of reproductive hormones provide physiologically representative exposure and mean concentrations when compared with daily collection.

To determine if reducing the frequency of urinary sample collection from daily to 5, 3, or 2 days per week during a menstrual cycle or 28-day amenorrheic monitoring period provide accurate representations of the reproductive hormone metabolites estrone-1-glucuronide (E1G) and pregnanediol glucuronide (PdG) exposure and mean concentrations. Exercising women presenting with eumenorrhea or exercise-associated menstrual disturbances collected daily urine samples for the assessment of E1G and PdG concentrations. After enzyme immunoassay analysis of the daily samples, E1G and PdG data were systematically removed from each menstrual cycle or amenorrheic monitoring period to mimic three reduced collection frequencies, representing 5, 3, and 2 days per week. Exposure and mean concentration were calculated for both hormones and all four urinary collection frequencies. E1G and PdG exposure and mean cycle concentrations derived from reduced collection frequencies were not different from daily collection (P > 0.05), independent of whether menstrual cycles and monitoring periods were analyzed together or separately. Bland-Altman analysis indicated acceptable agreement between each reduced collection frequency and daily collection. Compared with daily urinary collection, a reduced collection frequency of 5, 3, or 2 days each week provides accurate E1G and PdG profiles of collection periods of various lengths and types of menstrual function. Reduction of urinary sample collection frequency may enable researchers to reduce participant burden and costs, increase compliance, and study a wider range of study populations.

Detection issues in two-dimensional on-line chromatography

The dilution of analytes during their migration through two-dimensional liquid chromatographic systems was investigated. Simplified equations for the calculation of the dilution factors in the first and second dimension columns were derived considering the variance of the injected sample, the flow rates, the split ratio, the volume of the intermediate sample loop and the sampling time of the first-dimension effluent. The net dilution factor is the product of the dilution factors in the two single dimensions. It is between 200 and 300 in typical two-dimensional liquid chromatographic (2D-LC) separations. These values are less pessimistic than those reported previously [1]. It was shown that the fraction of organic modifier or stronger eluent component in the injected sample has a significant effect on the widths and heights of the eluted peaks. Analytes with high retention factors and high molecular weights are less sensitive toward this effect than those having small retention factors. These results suggest that the optimization of the experimental conditions of two dimension separations must be made from the points of view of both the retention factor and the detector response factor. The frequency of sampling of the eluent of the first-dimension separation does not have a significant effect on the detection limit of a 2D system if the split ratio is adjusted in the ratio of the frequency of sample collection.

Recent trends in paralytic shellfish toxins in Puget Sound, relationships to climate, and capacity for prediction of toxic events

Temporal and spatial trends in paralytic shellfish toxins (PSTs) in Puget Sound shellfish and their relationships with climate are investigated using long-term monitoring data since 1957. Data are selected for trend analyses based on the sensitivity of shellfish species to PSTs and their depuration rates, and the frequency of sample collection at individual sites. These criteria limit the analyses to the shellfish species Mytilus edulis at 20 sites from 1993 to 2007. Blue mussel toxicity is highly variable, but typically exceeds the regulatory limit for human consumption from July to November annually, with most closures occurring early in fall. Using blue mussel data only, we find no robust evidence to suggest that the frequency, magnitude, duration, or geographic scope of PST events in Puget Sound increased between 1993 and 2007. However, there is a significant basin-wide trend for closures to occur earlier in the year. There are no significant correlations between annual indices of mussel toxicity and aspects of the local and large-scale climate. Case studies of daily variations in local environmental factors leading up to exceptionally toxic events identify a combination of conditions that generally precedes most closures from 1993 to 2007. These results suggest that periods of warm air and water temperatures and low streamflow on sub-seasonal timescales may facilitate toxin accumulation in mussels. No relationships were found between water residence times in the surface layer and either streamflow or mussel toxicity. Recommendations are made for future monitoring to improve forecasting of PST risks in Puget Sound, an important region for recreational, commercial, and tribal subsistence shellfish harvesting.

Excretion patterns of titanium dioxide and chromic oxide in duodenal digesta and feces of ewes

Our objective was to examine differences in marker excretion patterns between Cr 2O 3 and TiO 2 in mature ewes fed diets varying in level of forage. Three experiments were conducted using an all forage diet, a 50% forage diet, and a 25% forage diet. In all three experiments, ewes were dosed intraruminally twice daily at feeding with gelatin boluses containing 2.5 g Cr 2O 3 and 2.5 g TiO 2. Following 7 days of adaptation to markers, fecal grab samples were collected at 6-h intervals for 6 days, representing every 1-h interval in a theoretical 24-h clock. On days 14–16 of each experiment, spot samples of duodenal digesta were collected at times representing 0, 2, 4, 6, 8, and 10 h after the morning feeding. Duodenal TiO 2 and Cr 2O 3 concentrations exhibited a diurnal pattern after feeding in all three experiments, but there were no marker × time interactions. Although fecal concentrations of TiO 2 were higher than Cr 2O 3 in all three experiments, there were no significant marker × time interactions observed. The lack of significant marker × time interactions resulted in little effect of sample collection frequency on mean concentrations of either marker, and as such, the frequency with which either duodenal or fecal samples are collected may be reduced in animals dosed twice daily without markedly affecting mean marker concentrations. Although estimates of digesta flow may differ between markers, the patterns of marker excretion observed suggest that TiO 2 behaves similarly to Cr 2O 3 within the gastrointestinal tract, and thus is an acceptable alternative to Cr 2O 3 for use in site and extent of digestion studies with ruminants.

A review of some tracer-test design equations for tracer-mass estimation and sample-collection frequency

A review of some tracer-test design equations for tracer-mass estimation and sample-collection frequency

A review of some tracer-test design equations for tracer-mass estimation and sample-collection frequency

Determination of necessary tracer mass, initial sample-collection time, and subsequent sample-collection frequency are the three most difficult aspects to estimate for a proposed tracer test prior to conducting the tracer test. To facilitate tracer-mass estimation, 33 mass-estimation equations have been developed over the past century. These 33 equations are reviewed here, 32 of which were evaluated using previously published tracer-test design examination parameters. Comparison of the results produced a wide range of estimated tracer mass, but no means is available by which one equation may be reasonably selected over the others. Each equation produces a simple approximation for tracer mass. Most of the equations are based primarily on estimates or measurements of discharge, transport distance, and suspected transport times. Although the basic field parameters commonly employed are appropriate for estimating tracer mass, the 33 equations are problematic in that they were all probably based on the original developers experience in a particular field area and not necessarily on measured hydraulic parameters or solute-transport theory. Suggested sampling frequencies are typically based primarily on probable transport distance, but with little regard to expected travel times. This too is problematic in that tracer sampling remains a haphazard process that tends to result in false negatives or data aliasing. Simulations from the recently developed efficient hydrologic tracer-test design methodology (EHTD) were compared with those obtained from 32 of the 33 published tracer-mass estimation equations and suggested sampling frequencies. EHTD applies functional relationships developed from hydrologic measurements in a solute-transport model to develop a preliminary tracer-breakthrough curve that has been shown to reasonably predict actual tracer-test results.

Optimizing minirhizotron sample frequency for an evergreen and deciduous tree species

• When using minirhizotrons to study fine dynamics in natural ecosystems, it is important to determine how sample collection frequency influences estimates of fine root production and mortality. Minirhizotron images were collected twice per week from mature Pseudotsuga menziesii and Tilia cordata trees and analyzed to estimate fine root production and mortality. These data were used to create data sets reflecting sample frequencies of 1, 2, 4 or 8wk. • When the sampling interval is long, fine roots can appear and disappear between samplings, leading to underestimates of production and mortality. For example, with an 8-wk sample frequency, 24 and 35% of the fine root production in P. menziesii and T. cordata , respectively, is not measured. Fine root mortality displays the same sensitivity to sample frequency. • Our experimental observations supported the previously published simulation analysis, which provides an estimate of the proportion of fine roots missed at different sample frequencies and is a tool that can be used to select a sample frequency to balance production and mortality accuracy with sampling and analytical effort.

Efficient hydrologic tracer-test design for tracer-mass estimation and sample-collection frequency. 2. Experimental results

Effective tracer-test design requires that the likely results be predicted in advance of test initiation to ensure tracer-test success. EHTD-predicted breakthrough curves (BTCs) for various hydrological conditions were compared with measured BTCs obtained from actual tracer tests. The hydrological conditions for the tracer tests ranged from flowing streams to porous-media systems. Tracer tests evaluated included flowing streams tracer tests conducted in small and large surface-water streams, a karst solution conduit, and a glacial-meltwater stream and porous-media systems conducted as natural-gradient, forced-gradient, injection-withdrawal, and recirculation tracer tests. Comparisons between the actual tracer tests and the predicted results showed that tracer breakthrough, hydraulic characteristics, and sample-collection frequency may be forecasted sufficiently well in most instances as to facilitate good tracer-test design. Comparisons were generally improved by including tracer decay and/or retardation in the simulations. Inclusion of tracer decay in the simulations also tended to require an increase in set average tracer concentration to facilitate matching peak concentrations in the measured BTCs, however. Both nonreactive tracer and reactive tracer predictions produced recommended sample-collection frequencies that would adequately define the actual BTCs, but estimated tracer-mass estimates were less precise.

Efficient hydrologic tracer-test design for tracer-mass estimation and sample-collection frequency, 1, method development

Hydrological tracer testing is the most reliable diagnostic technique available for the determination of basic hydraulic and geometric parameters necessary for establishing operative solute-transport processes. Tracer-test design can be difficult because of a lack of prior knowledge of the basic hydraulic and geometric parameters desired and the appropriate tracer mass to release. A new efficient hydrologic tracer-test design (EHTD) methodology has been developed to facilitate the design of tracer tests by root determination of the one-dimensional advection–dispersion equation (ADE) using a preset average tracer concentration which provides a theoretical basis for an estimate of necessary tracer mass. The method uses basic measured field parameters (e.g., discharge, distance, cross-sectional area) that are combined in functional relationships that describe solute-transport processes related to flow velocity and time of travel. These initial estimates for time of travel and velocity are then applied to a hypothetical continuous stirred tank reactor (CSTR) as an analog for the hydrological-flow system to develop initial estimates for tracer concentration, tracer mass, and axial dispersion. Application of the predicted tracer mass with the hydraulic and geometric parameters in the ADE allows for an approximation of initial sample-collection time and subsequent sample-collection frequency where a maximum of 65 samples were determined to be necessary for describing the predicted tracer-breakthrough curve (BTC). Inclusion of tracer retardation and decay cause a net increase in tracer-mass estimates so that the preset average tracer concentration will be maintained and there will be a consequent steepening of the BTC, but retardation also causes BTC spreading and a delay in tracer arrival.

How Effective is the TCR in Assessing Outbreak Vulnerability?

Previous studies have shown that waterborne disease outbreaks can occur in systems that have not exceeded the maximum contaminant level (MCL) regulations for coliform bacteria. The utility of the revised Total Coliform Rule (TCR), which has been in effect since Dec. 31, 1990, was evaluated as an indicator of outbreak vulnerability of public water systems. This study compared TCR violations for water systems that had and had not reported an outbreak during 1991–98. Few outbreak systems had violated the MCL in the 12‐month period before the outbreak, and MCL and monitoring violations did not differ significantly for the outbreak and nonoutbreak systems studied. These findings suggest that the TCR is not able to identify those water systems that are vulnerable to an outbreak. Requirements may need to be supplemented by an additional indicator and additional monitoring for systems that currently collect few samples. When evaluating the adequacy of an indicator, it is important to consider waterborne agents and the frequency of sample collection. The thoroughness of a sanitary survey is also important to detect and correct deficiencies that might lead to an outbreak. Current TCR monitoring focuses on the detection of coliforms in the distribution system after treatment; however, it may be more effective—especially for small groundwater systems—to monitor source water quality and assess the potential for contamination from sewage discharges and surface water runoff rather than to increase distribution system monitoring.

Effect of the stage of the oestrous cycle and the frequency of sample collection on the composition of ovine uterine fluids

Surgical procedures were employed to collect ovine uterine fluids on days 0, 3, 6, 9, 12 and 15 of the oestrous cycle, and at the subsequent return to oestrus. Samples from both uterine horns were collected from each ewe on two separate occasions, 3 days apart. Each group of ewes received its first uterine flush at one of the 6 days of the cycle indicated above. Uterine flushes were analysed for total protein, alkaline phosphatase, β-glucuronidase, leucine aminopeptidase and albumin. There were significant differences in the levels of leucine aminopeptidase, alkaline phosphatase, total protein and albumin between ewes experiencing their first collection of uterine fluid, and ewes at the same stage of the cycle which had been sampled 3 days previously. Investigation of the first sample collected from each ewe revealed cyclic changes in the levels of each of the five proteins. This experiment supports the view that ovarian steroids influence uterine fluid composition and indicates that serial samples of uterine flushings within a ewe may not give a valid representation of uterine function during the oestrous cycle.

Systemic availability of chloramphenicol from tablets and capsules in cats

Five adult cats were given 100 mg chloramphenicol per os on five occasions: twice in tablet form, twice in capsules which also contained barium sulphate, and once in capsules without barium. Plasma samples for chloramphenicol assay were obtained on either a ‘standard’ schedule (four samples collected within 8 h of dosing with tablet, plain capsule or capsule including barium) or a ‘frequent’ schedule (nine samples collected within 8 h of dosing with tablet or capsule including barium). With frequent sampling, abdominal radiographs were taken at intervals after administration of capsules. No differences were found with the frequent schedule between tablet and capsule with regard to antibiotic concentrations at each sampling, peak concentrations, or area under the curve of plasma concentration versus time. Standard sampling gave similar drug concentrations to those obtained with frequent sampling. Delayed absorption (defined as plasma chloramphenicol concentration &lt; 5 μg/ml for 1.5 h after dosing) occurred after six of the twenty‐five administrations: it was not related to the frequency of sample collection or the use of capsules rather than tablets, but occurred mainly in certain cats. Poor absorption was shown radiographically in one cat to be associated with delayed dispersal of capsular contents in the gut.