Recommended Sampling Time Research Articles

Effect of different soluble potassium fertilizers on yield, yield components and quality properties of different tomato cultivars irrigated by a drip system

Tomato (Solanum lycopersicum) is one of the main crops grown in Turkey for fresh consumption and for paste industry. The objective of this study was to examine the single and combined effects of some soluble potassium (K) fertilizers as nitrate of potash (NOP), sulfate of potash (SOP) and their combination (NOP+SOP) on marketable yield, yield components, some quality properties of a greenhouse tomato for table and a field cultivar for paste industry which were irrigated by a drip system. Results in relation to paste tomato showed that the highest yield was obtained from the SOP treatment. The highest EC, titratable acidity (TA), firmness, total soluble solids (brix), fruit width, height and weight (FW, FH, FW1) were found high in the NOP+SOP treatment. It is important to highlight that SOP receiving tomatoes are found high in their leaf K contents and NOP for many of the micro elements of the leaves. Table tomato results indicated that fertilizers applied by fertigation significantly affected the fruit yield, the highest being in the NOP+SOP treatment parcels. Firmness and TA were found high in the NOP+SOP treatment but the highest EC and brix in the SOP treatment. Likewise, the paste tomato, the leaf K and some of the micro elements in the leaves of table tomatoes are relatively high in the SOP treatment. It can be concluded that yield is important for both of the cultivar but brix yield obtained from per unit area is as well important. Marketable yield with attractive and tasteful fruits in the case of table cultivars are significant and needed to be highlighted. In this regard, economic analysis between SOP and NOP+SOP fertilization should be made before deciding on a recommendation. Most significant of all, nutritional status of tomato plants should be studied via their leaves at the recommended sampling time.

A New Method for Workplace Monitoring of Airborne Diacetyl and 2,3-Pentanedione Using Thermal Desorption Tubes and Gas Chromatography-Mass Spectrometry.

Diacetyl is a potentially harmful chemical that is used as an artificial flavouring in the food industry and may also be generated during processing of some natural products including coffee. In Europe, an 8-h time weighted average occupational exposure limit (TWA-OEL) of 20 ppb has been adopted for diacetyl, together with a short-term exposure limit (STEL) of 100 ppb. A sensitive new measurement method for diacetyl, and the related compound 2,3-pentanedione has been developed and evaluated. The new method uses Tenax TA sorbent tubes as the sampling media with analysis by thermal desorption (TD) and gas chromatography-mass spectrometry (GC-MS). The sample tubes are suitable for both active (pumped) and passive (diffusive) sampling. Diacetyl is stable on the sample tubes for at least 3 months but 2,3-pentanedione requires analysis within a month. Sample recovery is unaffected by changes in relative humidity and the presence of acetic acid. For short-term sampling, active sampling is recommended. The safe sampling volume for diacetyl is 3 litres which, at a flow rate of 100 ml min-1, equates to a maximum recommended sampling time of 30 min. For long-term samples, in particular collection of personal samples, passive sampling is recommended. Diffusive uptake rates have been determined for both diacetyl and 2,3-pentanedione on Tenax TA tubes fitted with standard diffusion heads over sampling periods of 1 to 8 h. Analytical limits of detection are approximately 0.2 ng for diacetyl and 0.1 ng for 2,3-pentanedione. These values equate to airborne concentrations of around 0.04 ppb of diacetyl and 0.02 ppb of 2,3-pentanedione for a 1.5-litre active sample and 0.3 ppb of diacetyl and 0.1 ppb of 2,3-pentanedione for an 8-h passive sample. In the case of passive sampling, this limit of detection is less than 1/50th of the new European TWA-OEL for diacetyl of 20 ppb. The method can also be used to identify the presence of other volatile organic compounds at sub-ppm concentrations.

Performance and uncertainties of TSS stormwater sampling strategies from online time series.

The event mean concentrations (EMCs) that would have been obtained by four different stormwater sampling strategies are simulated by using total suspended solids (TSS) and flowrate time series (about one minute time-step and one year of data). These EMCs are compared to the reference EMCs calculated by considering the complete time series. The sampling strategies are assessed with datasets from four catchments: (i) Berlin, Germany, combined sewer overflow (CSO); (ii) Graz, Austria, CSO; (iii) Chassieu, France, separate sewer system; and (iv) Ecully, France, CSO. A sampling strategy in which samples are collected at constant time intervals over the rainfall event and sampling volumes are pre-set as proportional to the runoff volume discharged between two consecutive sample leads to the most representative results. Recommended sampling time intervals are of 5 min for Berlin and Chassieu (resp. 100 and 185 ha area) and 10 min for Graz and Ecully (resp. 335 and 245 ha area), with relative sampling errors between 7% and 20% and uncertainties in sampling errors of about 5%. Uncertainties related to sampling volumes, TSS laboratory analyses and beginning/ending of rainstorm events are reported as the most influent sources in the uncertainties of sampling errors and EMCs.

Impacts of Insufficient Observations on the Monitoring of Short- and Long-Term Suspended Solids Variations in Highly Dynamic Waters, and Implications for an Optimal Observation Strategy

Coastal water regions represent some of the most fragile ecosystems, exposed to both climate change and human activities. While remote sensing provides unprecedented amounts of data for water quality monitoring on regional to global scales, the performance of satellite observations is frequently impeded by revisiting intervals and unfavorable conditions, such as cloud coverage and sun glint. Therefore, it is crucial to evaluate the impacts of varied sampling strategies (time and frequency) and insufficient observations on the monitoring of short-term and long-term tendencies of water quality parameters, such as suspended solids (SS), in highly dynamic coastal waters. Taking advantage of the first high-frequency in situ SS dataset (at 30 min sampling intervals from 2007 to 2008), collected in Deep Bay, China, this paper presents a quantitative analysis of the influences of sampling strategies on the monitoring of SS, in terms of sampling frequency and time of day. Dramatic variations of SS were observed, with standard deviation coefficients of 48.9% and 54.1%, at two fixed stations; in addition, significant uncertainties were revealed, with the average absolute percent difference of approximately 13%, related to sampling frequency and time, using nonlinear optimization and random simulation methods. For a sampling frequency of less than two observations per day, the relative error of SS was higher than 50%, and stabilized at approximately 10%, when at least four or five samplings were conducted per day. The optimal recommended sampling times for SS were at around 9:00, 12:00, 14:00, and 16:00 in Deep Bay. The “pseudo” MODIS SS dataset was obtained from high-frequency in situ SS measurements at 10:30 and 14:00, masked by the temporal gap distribution of MODIS coverage to avoid uncertainties propagated from atmospheric correction and SS models. Noteworthy uncertainties of daily observations from the Terra/Aqua MODIS were found, with mean relative errors of 19.2% and 17.8%, respectively, whereas at the monthly level, the mean relative error of Terra/Aqua MODIS observations was approximately 10.7% (standard deviation of 8.4%). Sensitivity analysis between MODIS coverage and SS relative errors indicated that temporal coverage (the percentage of valid MODIS observations for a month) of more than 70% is required to obtain high-precision SS measurements at a 5% error level. Furthermore, approximately 20% of relative errors were found with the coverage of 30%, which was the average coverage of satellite observations over global coastal waters. These results highlight the need for high-frequency measurements of geostationary satellites like GOCI and multi-source ocean color sensors to capture the dynamic process of coastal waters in both the short and long term.

Seasonal Variation in Mineral Nutrient Concentration of Primocane and Floricane Leaves in Trailing, Erect, and Semierect Blackberry Cultivars

Floricane-fruiting blackberry (Rubus L. subgenus Rubus, Watson) cultivars, ‘Marion’, ‘Black Diamond’, ‘Onyx’, ‘Columbia Star’ (early-season trailing types), ‘Ouachita’ (erect, midseason), and ‘Triple Crown’ and ‘Chester Thornless’ (semierect, late season) were studied for 2 years to determine whether these cultivars and types of blackberry should be sampled at a certain stage of development or time of season to best evaluate plant nutrient status. Leaf nutrient standards are based on primocane leaves in most countries, but there is interest in using floricane leaves. Primocane leaves were sampled every 2 weeks from late May through early October, whereas leaves on fruiting laterals (floricane) were sampled every 2 weeks from early May through fruit harvest. Leaves were analyzed to determine the concentration of macronutrients and micronutrients. The pattern of change in primocane leaf nutrient concentration varied between the trailing and the later-fruiting erect and semierect types, particularly for P, K, Ca, Mg, B, and Mn, where leaf levels were higher in the late season for the erect and semierect cultivars (except for P and K which were lower). Nutrient concentrations in floricane leaves decreased during growth and development of the lateral and fruiting season for N, P, K, and S, but increased for most other nutrients in all blackberry types. Floricane leaf N and K declined most rapidly during the fruit development period in all cultivars. Sampling of floricane leaves is not recommended, particularly for trailing types, as there are no sufficiency standards. In primocane leaves, the nutrients that did not show significant changes in concentration during the currently recommended sampling period of late July to early August were N, Mg, K, Ca, S, B, Mn, and Zn, but only in 2014. Leaf P, Fe, and Al were stable during this period in both years. In contrast, when sampling in mid to late August, leaf N, Mg, Fe, Mn, and Al were stable in both years and leaf K, Ca, S, B, Cu, and Zn were stable in one of the 2 years. We thus propose changing the recommended sampling time to mid to late August for these diverse blackberry cultivars. The current sufficiency standards for primocanes did not encompass the blackberry types and cultivars studied here, suggesting the standards may need to be revised for this region.

Seasonal Variation in Leaf Nutrient Concentration of Northern Highbush Blueberry Cultivars Grown in Conventional and Organic Production Systems

Northern highbush blueberry (Vaccinium corymbosum L.) cultivars were evaluated for leaf and fruit nutrient concentration at two production sites in 2013–14. The treatments included cultivar (Duke, Bluecrop, Draper, Legacy, Liberty, and Aurora), site [“conventional” (conventionally managed, grower-collaborator site) and “organic” (certified organic research site)], and amendment–mulch [at the organic site only; “organic mulch” (included preplant amendment and a surface mulch of yard debris compost and sawdust); and “weed mat” (no preplant amendments but with a sawdust mulch topped with weed mat)]. Leaf samples were collected every 2 weeks in all treatment plots from late April through early October of each year. Ripe fruit were subsampled from the second harvest for each cultivar. Fruiting season varied from 22 June to 19 Sept. and the highest yielding cultivar, Legacy, had 114% to 330% greater yield than the lowest, Duke, depending on year and site. Cultivar had a significant effect on all fruit nutrients except for phosphorus (P) at the conventional site. Nitrogen (N) and potassium (K) accounted for the largest proportion of nutrient content in the fruit, with 10 to 52 kg·ha–1 and 7 to 34 kg·ha–1 removed in the harvested fruit, respectively, depending on cultivar and site. Fruit carbon concentration ranged from 32% to 44% dry weight with 0.5 to 3.2 t·ha–1 removed in harvested fruit. There were significant year, site, and cultivar effects on leaf nutrient concentrations on many sample dates throughout the season. Despite relatively large differences in management between sites and yield and fruiting season among cultivars, the pattern in leaf nutrient concentration over sampling time was relatively similar between sites and years. Leaf manganese (Mn) and aluminum (Al) concentrations were higher when plants were grown with weed mat as compared with the organic mulch treatment, because soil pH was lower under weed mat than in the organic mulch treatment. ‘Liberty’ had the highest leaf N throughout much of the season at the conventional site. There were relatively large differences among cultivars in leaf magnesium (Mg), calcium (Ca), and K when sampling from mid-July to autumn at both sites. ‘Duke’ and ‘Bluecrop’ tended to have the highest leaf K during this period, whereas ‘Legacy’ and ‘Liberty’ had the lowest. There were greater differences in leaf Ca among cultivars at the conventional site than at the organic site. ‘Draper’ and ‘Legacy’ had higher leaf Ca than ‘Duke’. Leaf nutrient concentrations were within the current published sufficiency levels on many sample dates throughout the season for P, Mg, sulfur (S), Mn, and zinc (Zn), on many dates in midseason for K and Ca, and from mid- to late-season for boron (B) and iron (Fe). However, only when sampled in late July to early August, the current recommended sampling time, was leaf N within sufficiency range. Moreover, there was an effect of cultivar on the concentration of most leaf nutrients at both sites when sampled in late July to early August. The recommended sampling time to determine plant nutrient status in northern highbush blueberry should remain at late July to mid-August, regardless of cultivar, when most nutrients are relatively stable. We recommend lowering the leaf sufficiency range for P and copper (Cu) based on our findings.

Uptake and Partitioning of Nutrients in Blackberry and Raspberry and Evaluating Plant Nutrient Status for Accurate Assessment of Fertilizer Requirements

Raspberry and blackberry (Rubus sp.) plantings have a relatively low nutrient requirement compared with many other perennial fruit crops. Knowledge of annual accumulation of nutrients and periods of rapid uptake allows for better management of fertilization programs. Annual total nitrogen (N) accumulation in the aboveground plant ranged from 62 to 110 and 33 to 39 lb/acre in field-grown red raspberry (Rubus idaeus) and blackberry (Rubus ssp. rubus), respectively. Research on the fate of applied 15N (a naturally occurring istope of N) has shown that primocanes rely primarily on fertilizer N for growth, whereas floricane growth is highly dependent on stored N in the over-wintering primocanes, crown, and roots; from 30% to 40% of stored N was allocated to new growth. Plants receiving higher rates of N fertilizer took up more N, often leading to higher N concentrations in the tissues, including the fruit. Reallocation of N from senescing floricanes and primocane leaves to canes, crown, and roots has been documented. Accumulation of other macro- and micronutrients in plant parts usually preceded growth. Primocanes generally contained the highest concentration of most nutrients during the growing season, except calcium (Ca), copper (Cu), and zinc (Zn), which often were more concentrated in roots. Roots typically contained the highest concentration of all nutrients during winter dormancy. Nutrient partitioning varied considerably among elements due to different nutrient concentrations and requirements in each raspberry and blackberry plant part. This difference not only affected the proportion of each nutrient allocated to plant parts, but also the relative amount of each nutrient lost or removed during harvest, leaf senescence, and pruning. Macro- and micronutrient concentrations are similar for raspberry and blackberry fruit, resulting in a similar quantity of nutrient removed with each ton of fruit at harvest; however, yield may differ among cultivars and production systems. Nutrient removal in harvested red raspberry and blackberry fruit ranged from 11 to 18 lb/acre N, 10 to 19 lb/acre potassium (K), 2 to 4 lb/acre phosphorus (P), 1 to 2 lb/acre Ca, and 1 to 4 lb/acre magnesium (Mg). Pruning senescing floricanes in August led to greater plant nutrient losses than pruning in autumn. Primocane leaf nutrient status is often used in nutrient management programs. Leaf nutrient concentrations differ with primocane leaf sampling time and cultivar. In Oregon, the present recommended sampling time of late July to early August is acceptable for floricane-fruiting raspberry and blackberry types, and primocane-fruiting raspberry, but not for primocane-fruiting blackberry, where sampling leaves on primocane branches during the green fruit stage is recommended. Presently published leaf tissue standards appear to be too high for K in primocane-fruiting raspberry and blackberry, which is not surprising since the primocanes are producing fruit at the time of sampling and fruit contain a substantial amount of K.

A Preliminary Study to Predict the Ingested Dose of Doxylamine from its Plasma Concentration in the Korean Patients with Doxylamine Intoxication

Background: Doxylamine succinate, over-the-counter antihistamine, is commonly used as a nighttime sleep-aid and is world-wide ingested in overdoses when one attempts a suicide because of its easy accessibility. The objective of this study was aimed to find out models to predict the ingested amount of doxylamine from its blood concentrations of thirty Korean patients with doxylamine intoxication. Method: Thirty patients who were admitted to two emergency centers through Jul, 2006 to Jul, 2008 due to doxylamine overdose were recruited. In all patients, demographic information and clinical variables, arrival time to the hospital after doxylmamine overdose, amount of doxylamine ingested, and vomiting were evaluated. Results: Of these thirty patients, average ingestion amount of doxylamine was 750 mg (range, 200~2500 mg). The mean arrival time to the hospital after the doxylamine ingestion was 4.5 h (range, <1.0~24 h) and its mean blood level at arrival time was 3.15 μg/mL (range, 0.64~11.31 μg/mL). Ingested doxylamine dose was predicted by determining the coefficient of plasma drug concentration using stepwise regression analysis. The linear regression formula calculated was: y=241.769(x)+217.117 (y=ingested doxylamine dose, x=its plasma concentration, p=0.001). Conclusion: Close clinical observation, laboratory follow-up and analysis of blood doxylamine concentration were required for patients, who intoxicated doxylamine and admitted emergency department, to estimate ingested dose and time of doxylamine, and to prevent the clinical toxicity. We suggested that recommended sampling time for analysis of plasma doxylamine concentration was 1~3 h after the ingestion, and its plasma level at the arrival time was a statistically significant factor to predict the ingested dose of doxylamine in the 30 Korean patients with doxylamine intoxication.

Evaluation of a multi-endpoint assay in rats, combining the bone-marrow micronucleus test, the Comet assay and the flow-cytometric peripheral blood micronucleus test

With the publication of revised draft ICH guidelines (Draft ICH S2), there is scope and potential to establish a combined multi-end point in vivo assay to alleviate the need for multiple in vivo assays, thereby reducing time, cost and use of animals.Presented here are the results of an evaluation trial in which the bone-marrow and peripheral blood (via MicroFlow® flow cytometry) micronucleus tests (looking at potential chromosome breakage and whole chromosome loss) in developing erythrocytes or young reticulocytes were combined with the Comet assay (measuring DNA strand-breakage), in stomach, liver and blood lymphocytes. This allowed a variety of potential target tissues (site of contact, site of metabolism and peripheral distribution) to be assessed for DNA damage. This combination approach was performed with minimal changes to the standard and regulatory recommended sampling times for the stand-alone assays.A series of eight in vivo genotoxins (2-acetylaminofluorene, benzo[a]pyrene, carbendazim, cyclophosphamide, dimethylnitrosamine, ethyl methanesulfonate, ethyl nitrosourea and mitomycin C), which are known to act via different modes of action (direct- and indirect-acting clastogens, alkylating agents, gene mutagens, cross-linking and aneugenic compounds) were tested. Male rats were dosed at 0, 24 and 45h, and bone marrow and peripheral blood (micronucleus endpoint), liver, whole blood and stomach (Comet endpoint) were sampled at three hours after the last dose. Comet and micronucleus responses were as expected based on available data for conventional (acute) stand-alone assays.All compounds were detected as genotoxic in at least one of the endpoints. The importance of evaluating both endpoints was highlighted by the uniquely positive responses for certain chemicals (benzo[a]pyrene and 2-acetylaminofluorene) with the Comet endpoint and certain other chemicals (carbendazim and mitomycin C) with the micronucleus endpoint.The data generated from these investigations demonstrate the suitability of the multi-endpoint design.

Testing for Plant-parasitic Nematodes that Feed on Corn in Iowa 2000-2010

The Iowa State University Plant and Insect Diagnostic Clinic analyzes soil and root samples for plant-parasitic nematodes. The results of samples associated with corn that were submitted from 2000 through 2010 were summarized. One or more genera of plant-parasitic nematodes were found in 92% of the samples. Spiral nematode and root-lesion nematode were most commonly found. Other nematodes recovered were dagger, lance, needle, pin, ring, and stunt nematodes. Nematodes recovered at damaging population densities were dagger, needle, ring, and spiral nematodes. An average of 15 samples were submitted per year from 2000 to 2004. Sample numbers increased nearly threefold since 2005, but overall sample numbers were low every year from 2000 through 2010. Samples were received from 53 of the 99 Iowa counties, and most samples were received in June and July, which is the recommended sampling time. Nematodes that have been associated with corn in Iowa in the past that were not recovered from the samples were sheath, sting, and stubby-root nematodes. The methods used to extract the nematodes from soil and roots and how the samples were handled during collection and processing may have affected the species and population densities recovered. Much more frequent and widespread sampling is needed in Iowa for plant-parasitic nematodes that feed on corn. Accepted for publication 28 October 2011. Published 5 December 2011.

Seasonal reproductive patterns and recommended sampling times for sentinel fish species used in environmental effects monitoring programs in Canada

Canada’s environmental effects monitoring (EEM) program is currently in its fifth cycle of monitoring for the pulp and paper industry and second cycle of monitoring for the metal mining industry. More than 60 different sentinel fish species have been used in the EEM fish population surveys and reproductive impacts have been identified as an issue of concern in the pulp and paper program. A review of the literature was conducted to obtain details of the reproductive biology of each fish species that has been used in EEM studies in Canada. Using available data on seasonal changes in gonadosomatic indices, the seasonal reproductive patterns of Canadian fish species were divided into categories based on reproductive strategy and the timing of initiation of gonadal recrudescence. Recommended sampling times were developed for each reproductive pattern based on periods of temporal stability, minimum variability, and maximum value in gonadosomatic indices within a reproductive cycle. The reproductive strategy, spawning time, spawning temperature, and recommended sampling time were provided for the each sentinel fish species as well as life history characteristics including longevity, age and size at maturity, and mobility. Examination of the fish surveys using small bodied forage species from the EEM pulp and paper program revealed that approximately 72% of these studies were not conducted at the developed recommended sampling times and the magnitude of impacts may be underestimated by failing to sample at the recommended time.

확산길이에 따른 수동식 유기용제 시료채취기의 시료채취성능에 관한 연구

Passive samplers have been used for many years for the sampling of organic vapors in work environment atmospheres. Currently, all passive samplers used in domestic occupational monitoring are foreign products. This study was performed to evaluate variable parameters for the development of passive organic samplers, which include the geometry of the device and diffusive length for the sampler design. Four prototype diffusive lengths; A-1(4.5 mm), A-2(7.0 mm), A-3(9.5 mm), A-4(12.0 mm) were tested for adsorption performances to a chemical mixture (benzene, toluene, trichloroethylene, and n-hexane) according to the US-OSHA's evaluation protocol. A dynamic vapor exposure chamber developed and verified by related research was used for this study. The results of study are as follows. The results in terms of sampling rate and recommended sampling time test indicate that the most suitable model was A-3 (9.5 mm diffusive lengths on both sides) for passive sampler design in time weighted average (TWA) assessment. Sampling rates of this A-3 model were 45.8, 41.5, 41.4, and 40.3 ml/min for benzene, toluene, trichloroethylene, and n-hexane, respectively. The A-3 models were tested on reverse diffusion and conditions of low humidity air (35% RH) and low concentrations (0.2 times of TLV). These conditions had no affect on the diffusion capacity of samplers. In conclusion, the most suitable design parameters of passive sampler are: 1) Geometry and structure - 25 mm diameter and 490 cross sectional area of diffusion face with cylindrical form of two-sided opposite diffusion direction; 2) Diffusive length - 9.5 mm in both faces; 3) Amount of adsorbent - 300 mg of coconut shell charcoal; 4) Wind screen - using nylon net filters (11 pore size).

Circadian and Stimulated Thyrotropin Secretion in Cranially Irradiated Adult Cancer Survivors

It has been claimed that with the use of the TRH test and knowledge of the nocturnal TSH surge, the diagnosis of so-called hidden central hypothyroidism might be uncovered in a substantial proportion of euthyroid cranially irradiated children. We conducted 24-h TSH profiles and TRH tests in 37 euthyroid adult cancer survivors 2-29 yr (median, 11.5) after irradiation (18-64 Gy) and in 33 matched normal controls. Basal and stimulated TSH levels (during the TRH test) were significantly (P < 0.05) higher in the patients who had received craniospinal irradiation, more so in those with severe GH deficiency. Six patients (16%) had a hypothalamic TSH response to TRH. The maximum TSH surge calculated from the highest peak (average of the highest three sequential samples) and the smallest nadir (average of the smallest three sequential samples) in the whole 24-h profile period was above the cutoff value of 50% in all except one control subject and two patients. However, the nocturnal TSH surge was greatly reduced or absent in eight normal subjects (24%) and six patients (16%), not due to a genuine loss of diurnal rhythm, but simply to a shift in the timing of the peak TSH and/or the nadir TSH to outside the recommended sampling times (for the nocturnal surge) of 2200-0400 and 1400-1800 h, respectively; thereby potentially leading to an erroneous diagnosis of hidden central hypothyroidism. Overall, the maximum TSH surge was significantly (P = 0.01) reduced only in the GH-deficient patients (100.7 +/- 11%) compared with normal subjects (154.9 +/- 18.2%). Free T4 levels did not correlate with TSH surge results. The normality of free T4 levels and the wide discrepancy between the high rate of these TSH abnormalities and the very low rate of overt secondary hypothyroidism (3-6%) after prolonged periods of postirradiation follow-up strongly suggest that in the vast majority of patients, these abnormalities in TSH dynamics represent subtle functional disturbances in the hypothalamic-pituitary axis rather than genuine pathology that may progress with time. We suggest that in this context, use of the term hidden central hypothyroidism is inappropriate, because these subtle changes may not have any clinical significance.

Nondestructive, minimal-disturbance, direct-burial solid-phase microextraction fiber technique for measuring TNT in sediment.

We explored a novel technique to deploy solid-phase microextraction (SPME) fibers to nondestructively measure the explosive compound 2,4,6-trinitrotoluene (TNT) and its nitroaromatic (NA) degradation products in laboratory sediment toxicity tests and field sediments in situ. SPME fibers within steel mesh envelopes were exposed statically via direct burial within sediment. Six fiber types (polymer coatings) were tested. Polyacrylate (PA) SPME fiber was sufficiently durable for this application, yielded the lowest detection limits, and exhibited a linear uptake relationship across toxicologically relevant sediment NA concentrations (100-2000 nmol/g dw (20-500 microg/g dw)). Temperature greatly influenced SPME absorption kinetics. Via evaluation of absorption at different temperatures, recommended sampling times needed to achieve steady-state equilibrium were 48 h for room temperatures (23-25 degrees C) and up to 7 d for cold (5 degrees C) temperatures. Although a comparison of TNT residues by SPMEs and TNT bioavailability and toxicity in sediments has not been completed, differences in SPME availability of TNT and its degradation products were found between two different TNT-spiked sediments. Our disposable SPME technique was slightly less expensive and as precise as the conventional extraction for total NAs and may prove to be a powerful exposure evaluation tool for assessing the ecological risk of these compounds.

Use of Matrix Designs in Stability Studies: A Simulation Study

A stability study is designed to study the degradation profile of a drug product over time. It is required that at least three batches of the drug product in its finished form be studied over time. Often it is desired to manufacture the product in various forms, using a variety of packaging options. If three batches of product are studied for each combination of these experimental conditions at each of the recommended sampling times, the cost of the study can be substantial. Simulation studies are used to examine the effect of matrix designs; it is shown that the performance of these reduced testing plans is similar to the full sampling plan in terms of power to detect slope differences and estimation of the expiration dating period.

Effect of plumbing systems on lead content of drinking water and contribution to lead body burden

Stable lead isotopes and lead contents in drinking water from a number of Australian cities have been measured to determine the contribution of drinking water to body burden. Lead contents are generally < 2 μg/l and thus contribute an insignificant amount to the lead budget in humans in Australia. First-flush and running water samples taken at intervals of up to 10 min show that equilibrium is reached within 1 min or ∼ 10 1 by volume. There is, however, large variability in both lead content and isotopic composition within the first minute which brings into question the reliability of the recommended sampling time of 30 s. Extremely large isotopic differences between individual dwellings within the one city and between dwellings and the storage tanks for the water supply are attributed to differences in lead residing in the plumbing within the dwellings, usually from lead solder in brass fittings. Isotopic analysis of solder and water from two dwellings confirm this relationship.

A New Audit Method for EPA Reference Method 6

A simple, inexpensive, and accurate method for evaluating and/or auditing sampling and analytical phases of the EPA Source Reference Method 6 was developed. The method uses a known amount of a chemical compound in the form of a tablet or pill (or placed in a capsule) to generate sulfur dioxide quantitatively by reaction with an acid. The reaction takes place in a compact glass impinger system that can be taken to the field. The S02 generated in test runs was collected and analyzed using the Method 6 procedure. The SO2 generation was quantitative and recoveries were found to be 94 ± 5 %. The time to complete the reaction was less than 15 min at a flow rate of 1 L/min, but the recommended sampling time was 45 min. The tablets prepared gravimetrically were found to be stable over a sixmonth period. The interlaboratory results obtained showed close agreement with the expected concentrations based on calculations from the stoichiometric reaction. The estimates of repeatability (or within-laboratory precision) ...