Celite Column Research Articles

The Detection of Trace Metal Contaminants in Organic Products Using Ion Current Rectifying Quartz Nanopipettes.

While ion current rectification (ICR) in aprotic solvent has been fundamentally studied, its application in sensing devices lacks exploration. The development of sensors operable in these solvents is highly beneficial to the chemical industry, where polar aprotic solvents, such as acetonitrile, are widely used. Currently, this industry relies on the use of inductively coupled plasma mass spectrometry (ICP-MS) and optical emission spectroscopy (OES) for the detection of metal contamination in organic products. Herein, we present the detection of trace amounts of Pd2+ and Co2+ using ion current rectification, in cyclam-functionalized quartz nanopipettes, with tetraethylammonium tetrafluoroborate (TEATFB) in MeCN as supporting electrolyte. This methodology is employed to determine the concentration of Pd in organic products, before and after purification by Celite filtration and column chromatography, obtaining comparable results to ICP-MS within minutes and without complex sample preparation. Finite element simulations are used to support our experimental findings, which reveal that the formation of double-junction diodes in the nanopore enables trace detection of these metals, with a significant response from baseline even at picomolar concentrations.

Effects of treatments with nigerosylmaltooligosaccharide, glucose and sucrose on the vase life of cut snapdragon flowers

Nigerosylmaltooligosaccharide (Nmo) has different degrees of polymerarization (DP) of nigerosyl oligosaccharides and maltooligosaccharides. We investigated the effects of treatments with Nmo, glucose, sucrose, and their combinations on the vase life of cut snapdragon (Antirrhinum majus) flowers. To apply these sugars, the cut ends of flower spikes were dipped into these sugar solutions. Treatment with 30 g L−1 Nmo promoted bud development, resulting in flower opening at the upper part of the spikes. The Nmo treatment also extended the vase life of cut snapdragons more than glucose and sucrose treatments when vase life was evaluated as the time to when all flowers wilted. However, there were few open flowers, flowers were smaller and aurone levels were lower in the Nmo treatment, suggesting that treatment with Nmo alone is not sufficient for improving the vase life of cut snapdragons. Combined treatments of Nmo with glucose and sucrose increased the number of open flowers and significantly extended vase life more than treatment with glucose or sucrose alone. The deleterious effects of Nmo, such as the reduction in flower size and suppression of pigmentation, were alleviated by these combined treatments. Nmo was fractionated using a carbon celite column into DP2, DP3, DP4, and DP> 4. Spike length was significantly increased by fractions DP4 and DP>4, suggesting that oligosaccharides containing these fractions largely contribute to the development of spikes. In conclusion, Nmo is a readily available oligosaccharide that could be used in the manufacture of preservatives to improve the vase life of cut snapdragons.

Structural characterization and antioxidant activity of oligosaccharides from Panax ginseng C. A. Meyer

The purpose of present work was to investigate the antioxidant activity of oligosaccharides from mountain-cultivated ginseng (MCG) and cultivated ginseng (CG). The antioxidant activity of total oligosaccharides from MCG and CG were compared preliminary. And then, the total oligosaccharides of MCG, which displayed stronger activity than that of CG, were separated by Carbon–Celite column and eluted with water and ethanol of different concentrations (30%, 50%, 70%, 95%, v/v). Five fractions, MCGOS-H2O, MCGOS-30, MCGOS-50, MCGOS-70, MCGOS-95, were obtained. Seven oligosaccharides were purified from MCGOS-30–MCGOS-95. The structure features of oligosaccharides (MCGO-1–MCGO-7) were characterized using high performance liquid chromatography (HPLC), methylation and gas chromatography-mass (GC–MS), as well as nuclear magnetic resonance spectroscopy. ABTS radical scavenging assay, DPPH radical scavenging assay as well as ferric reducing antioxidant power assay were adopted for antioxidant activity of all the different oligosaccharides sub-fraction. The result showed that the fractions of MCGOS-70 and MCGOS-95 exhibited significant radical scavenging activity with DPPH and ABTS. In conclusion, the oligosaccharides from MCG possessed the significant antioxidant activity. Therefore, we propose that the oligosaccharides from Panax ginseng can be developed as natural antioxidants in food and pharmaceutical fields.

Do metabolites account for higher serum steroid hormone levels measured by RIA compared to mass spectrometry?

Higher circulating estradiol levels are generally obtained using conventional radioimmunoassays (RIA) compared to liquid chromatography/tandem mass spectrometry (LC-MS/MS) assays, and this has been attributed to the presence of estradiol metabolites that cross-react with the antibody used in the RIA. This study aimed to determine which estradiol metabolites may contribute to this effect. LC-MS/MS analysis was performed on 70 serum samples from premenopausal women, after purification by extraction and Celite column partition chromatography as would be used prior to conventional RIA for estradiol. The metabolites estrone and 2-methoxyestradiol accounted for 6.9% and 2.1% of the estradiol fractions in the purified samples overall, but the extent of contamination with these metabolites was greater in the samples containing <50 pg/mL estradiol (14.6% and 3.8% respectively) than in those containing >50 pg/mL estradiol. However, since these metabolites have a < 1% cross-reactivity to the antibody in the estradiol RIA, this level of contamination is too small to account for the differences between RIA and LC-MS/MS measurements of estradiol.

Congener specific determination of polychlorinated naphthalenes in sediment and biota by gas chromatography high resolution mass spectrometry

An isotope dilution congener-specific method for the determination of the most abundant and most toxic polychlorinated naphthalenes (PCNs) was developed using gas chromatography with high resolution mass spectrometry (GC-HRMS). The method was used to determine the concentration of 24 target congeners and total PCN concentrations in fish and sediment samples. Tissue samples were extracted using pressurized liquid extraction (PLE) and sediment samples were extracted using Soxhlet extraction. Sample extracts were cleaned up using either a manual two-stage open column procedure or an automated FMS Power Prep System with multi-analyte and multi-sample capability using a three-column cleanup procedure. Sediment extracts were cleaned up with a dual open column cleanup technique involving the use of both a multi-layered silica (silver nitrate/acid/base/neutral silica) column followed by column containing carbon-activated silica. Fish tissue extracts were cleaned up on the automated system involving the use of a high capacity ABN (acid/base/neutral column), carbon celite column, and a basic alumina column. The method is capable of producing instrument detection limits (IDLs) between 0.06 and 0.13pg for each PCN (on column), with method detection limits (MDLs) for the fish extracts ranging from 1.3 to 3.4pg/g (wet weight) and 0.46 to 1.2pg/g (dry weight) for sediments. The average accuracy of 34 spiked fish samples analysed over a period of several months was 100% with a precision (%RSD) of 12%. Similarly, the average accuracy for 28 spiked sediment samples was 104% with a precision (%RSD) of 12%. The application of the method to environmental samples was demonstrated through the analysis of sediment and fish samples obtained from Lake Ontario, Canada. The method is used both for the determination of 24 PCNs and to perform non-targeted screening for the remaining 51 PCN congeners, which are included in the total PCN quantification result. It is currently one of the most comprehensive and accurate congener-specific methods available and was developed from the existing techniques used for the determination of polychlorinated dioxins and furans to produce high quality data with only minor modifications in the clean-up procedure. It can therefore be readily adopted by other laboratories performing dioxin and POP analyses.

Structural analysis of novel kestose isomers isolated from sugar beet molasses

Eight kestose isomers were isolated from sugar beet molasses by carbon–Celite column chromatography and HPLC. GC–FID and GC–MS analyses of methyl derivatives, MALD-TOF-MS measurements and NMR spectra were used to confirm the structural characteristics of the isomers. The 1H and 13C NMR signals of each isomer saccharide were assigned using COSY, E-HSQC, HSQC–TOCSY, HMBC and H2BC techniques. These kestose isomers were identified as α-D-fructofuranosyl-(2- > 2)-α-D-glucopyranosyl-(1 < ->2)-β-D-fructofuranoside, α-D-fructofuranosyl-(2- > 3)-β-D-fructofuranosyl-(2 < ->1)-α-D-glucopyranoside, α-D-fructofuranosyl-(2- > 4)-β-D-fructofuranosyl-(2 < ->1)-α-D-glucopyranoside, β-D-fructofuranosyl-(2- > 4)-β-D-fructofuranosyl-(2 < ->1)-α-D-glucopyranoside, β-D-fructofuranosyl-(2- > 3)-α-D-glucopyranosyl-(1 < ->2)-β-D-fructofuranoside, α-D-fructofuranosyl-(2- > 1)-β-D-fructofuranosyl-(2 < ->1)-α-D-glucopyranoside, α-D-fructofuranosyl-(2- > 6)-α-D-glucopyranosyl-(1 < ->2)-β-D-fructofuranoside, and α-D-fructofuranosyl-(2- > 6)-β-D-fructofuranosyl-(2 < ->1)-α-D-glucopyranoside. The former five compounds are novel saccharides.

Structural confirmation of novel oligosaccharides isolated from sugar beet molasses

Eleven oligosaccharides were isolated from sugar beet molasses using carbon–Celite column chromatography and HPLC. The constituent sugars and linkage positions were determined using methylation analysis, MALDI–TOF-MS, and NMR measurements. The configurations of isolated oligosaccharides were confirmed based on detailed NMR analysis. Based on our results, three of the 11 oligosaccharides were novel.

Isolation of sophorose during sophorolipid production and studies of its stability in aqueous alkali: epimerisation of sophorose to 2-O-β-d-glucopyranosyl-d-mannose

NMR and anion exchange chromatography analysis of the waste streams generated during the commercial production of sophorolipids by the yeast Candida bombicola identified the presence of small but significant quantities (1% w/v) of free sophorose. Sophorose, a valuable disaccharide, was isolated from the aqueous wastes using a simple extraction procedure and was purified by chromatography on a carbon celite column providing easy access to large quantities of the disaccharide. Experiments were undertaken to identify the origin of sophorose and it is likely that acetylated sophorose derivatives were produced by an enzyme catalysed hydrolysis of the glucosyl-lipid bond of sophorolipids; the acetylated sophorose derivatives then undergo hydrolysis to release the parent disaccharide.Treatment of sophorose with aqueous alkali at elevated temperatures (0.1M NaOH at 50 °C) resulted in C2-epimerisation of the terminal reducing sugar and its conversion to the corresponding 2-O-β-d-glucopyranosyl-d-mannose which was isolated and characterised. In aqueous alkaline solution β-(1,2)-linked glycosidic bonds do not undergo either hydrolysis or peeling reactions.

Association between self-report adherence measures and oestrogen suppression among breast cancer survivors on aromatase inhibitors

PurposePoor adherence to oral adjuvant hormonal therapy for breast cancer is a common problem, but little is known about the relationship between self-report adherence measures and hormonal suppression. We evaluated the relationship of three self-report measures of medication adherence and oestrogen among patients on aromatase inhibitors (AIs). Materials and methodsWe recruited 235 women with breast cancer who were prescribed AI therapy. Participants self-reported AI adherence by completing the following: (1) a single item asking whether they took an AI in the last month, (2) a modified Morisky Medication Adherence Scale-8 (MMAS-8) and (3) the Visual Analog Scale (VAS). Serum estrone and estradiol were analysed using organic solvent extraction and Celite column partition chromatography, followed by radioimmunoassay. ResultsTen percent of participants reported they had not taken an AI in the last month and among this group, median estrone (33.2pg/ml [interquartile range (IQR)=22.3]) and estradiol levels (7.2pg/mL [IQR=3.3]) were significantly higher than those in participants who reported AI use (median estrone=11.5pg/mL [IQR=4.9]; median estradiol=3.4pg/mL [IQR=2.1]; p<0.001). This relationship held when controlling for race and AI drug type. ConclusionsA single-item monthly-recall adherence measure for AIs was associated with oestrogen serum levels. This suggests that patient-reported monthly adherence may be a useful measure to identify early non-adherence behaviour and guide interventions to improve patient adherence to hormonal treatment.

Tomato Pomace Pigment : Extraction and Use as Food Colorant

Tomato pomace pigment was extracted with organic solvents and corn oil,purified and fractionated on MgO: Celite (1:1 wt/wt) column. Results showed that among the solvents used the extraction of the pigment, carbon tetra chloride: ethanol (1:1) was the most efficient one yielding 166.3 mg pigment extract/ kg tomato pomace. The major carotenoid fractions were : lycopene 71.37%, phytoene 13.3%, phytofluene 5.55%, β-carotene 4.46%, γ-carotene 3.13 and δ- carotene 2.39. Stability of the corn oil extract was poor to heat and light, moderate to oxygen and high to pH in the range of 3.0-9.0. Sensory evaluation of the coloured foods with the same extract indicated that the pigment can be used successfully in the coloration of such foods as ice cream, margarine, potato chips and cooked rice as it imparted no off flavour or objectionable colour.

Women with acute intermittent porphyria have a defect in 5α-steroid production during the menstrual cycle

To measure serum concentrations of progesterone, estradiol and 5α- and 5β-reduced progesterone metabolites in the follicular and luteal phases of the menstrual cycle in women with latent acute intermittent porphyria and manifest acute intermittent porphyria in comparison with healthy control women. A descriptive study with repeated measurements during a complete, ovulatory menstrual cycle. University hospital out-patient clinic. Thirty-two women with DNA-diagnosed acute intermittent porphyria and 20 healthy control women. Blood samples for serum progesterone, estradiol, allopregnanolone and pregnanolone were drawn on predefined menstrual cycle days, twice in the follicular phase and three times in the luteal phase. Serum levels of estradiol and progesterone were analysed with commercial kits. Allopregnanolone and pregnanolone levels were analysed with radioimmunoassay following diethylether extraction and celite column chromatography. Changes in serum levels of progesterone, estradiol, allopregnanolone and pregnanolone throughout the menstrual cycle. Women with acute intermittent porphyria displayed lower serum concentrations of allopregnanolone in comparison with healthy control women, the difference being most prominent in the luteal phase (p < 0.001). Levels of pregnanolone did not differ significantly between groups. No significant difference was found between women with latent acute intermittent porphyria and manifest acute intermittent porphyria. Decreased levels of the 5α-reduced progesterone metabolite allopregnanolone were found in the menstrual cycle of women with acute intermittent porphyria. This has not been reported previously and could indicate a reduced 5α-reductase type 1 capacity in the ovary and liver among these women.

Assessment of theca cell function: a prerequisite to androgen or luteinizing hormone supplementation in poor responders

Poor responders are a heterogeneous population, with some patients displaying a diminished ovarian reserve and others a poor ovarian reserve with preserved granulosa cell function. Androgen and LH/hCG supplementation has been advocated for poor responders, mainly those >40 years old. Although androgens synergistically act with FSH to support folliculogenesis, and ovarian androgen secretion declines with age, there is still no evidence that androgen therapy is actually effective to improve ovarian FSH sensitivity. The main reason seems to be that theca cell function has not been appropriately assessed in patients at risk of poor response. The definition of theca insufficiency is hampered by methodologic shortcomings in routine bioassays. Provocative tests for theca cells might help to identify those patients who could benefit from androgen supplementation. The lack of data regarding theca cells in these patients might contribute to explaining the absence of evidence for a positive effect of androgen therapy.

P4-02-12: Plasma Estradiol Levels and Degree of Estrogen Receptor Positivity by Image Analysis in a Large Cohort of Breast Cancer Cases: Results from the Nurses' Health Study.

Abstract Background Breast cancer risk is strongly associated with endogenous reproductive hormones. There is also good evidence to suggest that endogenous estradiol levels are more strongly associated with the development of estrogen receptor (ER) positive breast cancers than with ER negative cancers. However, the degree of ER positivity in those cancers that develop is not yet established. Therefore, we sought to evaluate the proportion and intensity of tumor cells demonstrating ER positivity using image analysis in a large cohort of breast cancers for which we also had plasma estradiol levels. Design: Tissue microarray (TMA) sections of breast cancers from women enrolled in the Nurses’ Health Study were immunostained for ER (1D5, Dako Corporation, Carpinteria, CA). Slides were then scanned using the ScanScope slide scanning system (Aperio Technologies Inc., Vista, CA) and ER staining was assessed for both intensity and percent of nuclei staining positively using a specific algorithm, Nuclear v9, which evaluates nuclear size, intensity, roundness, curvature, compactness, and elongation. Plasma samples were collected prior to the date of diagnosis for all women in the study and estradiol levels were determined by radioimmunoassay following extraction and celite column chromatography. Result: Image analysis data for ER was available for 691 breast cancers. The mean percent of tumor cell positivity was approximately uniformly distributed, with a mean of 44.5%, (median=41.3%, max=99.6%). The proportion of tumor cells staining for ER from the TMA cores was positively associated with patient age (p&amp;lt;0.0001), and postmenopausal status (p=0.008), while inversely associated with tumor grade (p&amp;lt;0.0001). Among women with image analysis data for ER, plasma estradiol data were also available for 320 postmenopausal women. Estrogen receptor positivity (by proportion or intensity) did not vary according to plasma estradiol levels (p=0.17). Conclusion: While high concentrations of plasma estradiol are more strongly associated with the development of estrogen receptor positive breast cancer versus estrogen receptor negative cancers, the degree of estrogen receptor positivity in the breast cancers that develop is not influenced by this variable. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-02-12.

Isolation and structural confirmation of the oligosaccharides containing α- d-fructofuranoside linkages isolated from fermented beverage of plant extracts

Fermented beverage of plant extracts was prepared from the extracts of approximately 50 types of vegetables and fruits. Natural fermentation was carried out mainly by lactic acid bacteria ( Leuconostoc spp.) and yeast ( Zygosaccharomyces spp. and Pichia spp.). Two oligosaccharides containing an α-fructofuranoside linkage were detected in this beverage and isolated using carbon–Celite column chromatography and preparative HPLC. The structural confirmation of the saccharides was determined by methylation analysis, MALDI-TOF-MS, and NMR measurements. These saccharides were identified as α- d-fructofuranosyl-(2→6)- d-glucopyranose, which was isolated from a natural source for the first time, and a novel saccharide β- d-fructopyranosyl-(2→6)-α- d-fructofuranosyl-(2↔1)-α- d-glucopyranoside.

Plasma sex hormone concentrations and breast cancer risk in an ethnically diverse population of postmenopausal women: the Multiethnic Cohort Study

To add to the existing evidence that comes mostly from White populations, we conducted a nested case-control study to examine the association between sex hormones and breast cancer risk within the Multiethnic Cohort that includes Japanese American, White, Native Hawaiian, African American, and Latina women. Of the postmenopausal women for whom we had a plasma sample, 132 developed breast cancer during follow-up. Two controls per case, matched on study area (Hawaii, Los Angeles), ethnicity/race, birth year, date and time of blood draw and time fasting, were randomly selected from the women who had not developed breast cancer. Levels of estradiol (E(2)), estrone (E(1)), androstenedione, dehydroepiandrosterone (DHEA), and testosterone were quantified by RIA after organic extraction and Celite column partition chromatography. E(1) sulfate, DHEA sulfate (DHEAS), and sex hormone-binding globulin (SHBG) were quantified by direct immunoassays. Based on conditional logistic regression, the sex hormones were positively associated and SHBG was negatively associated with breast cancer risk. All associations, except those with DHEAS and testosterone showed a significant linear trend. The odds ratio (OR) associated with a doubling of E(2) levels was 2.26 (95% confidence interval (CI) 1.58-3.25), and the OR associated with a doubling of testosterone levels was 1.34 (95% CI 0.98-1.82). The associations in Japanese American women, who constituted 54% of our sample, were similar to or nonsignificantly stronger than in the overall group. This study provides the best evidence to date that the association between sex hormones and breast cancer risk is generalizable to an ethnically diverse population.

Structural and enhanced memory activity studies of extracts from Panax ginseng root

Abstract The aim of this paper is to study low molecular mass carbohydrate polymer from Panax ginseng root. The aqueous extracts of P. ginseng root were loaded onto a macroporous resin, then forced through a Cellulose Super Filtration System, and loaded onto a Carbon–Celite column and eluted with water, 5% ethanol, 30% ethanol and 95% ethanol. To determine if 30% ethanol elution from a Carbon–Celite column could enhance memory in scopolamine-induced memory deficit rats, Mirros water maze task was used. The purification of the 30% ethanol elution was performed on Sephadex G-15 and Bio-gel P2 columns. GC–MS analysis of methylated derivatives as well as ESI-MS measurement were used for structural confirmation. Results showed that 30% ethanol elution could enhance memory in scopolamine-induced memory deficit rats with intraperitoneal administration. Oligosaccharides and peptides were isolated from 30% ethanol elution. The oligosaccharides were identified as maltose, maltotriose, maltotetraose, maltopentaose, maltohexaose, maltoheptaose.

Two novel oligosaccharides isolated from a beverage produced by fermentation of a plant extract

An extract from 50 kinds of fruits and vegetables was fermented to produce a new beverage. Natural fermentation of the extract was carried out mainly by lactic acid bacteria ( Leuconostoc spp.) and yeast ( Zygosaccharomyces spp. and Pichia spp.). Two new saccharides were found in this fermented beverage. The saccharides were isolated using carbon–Celite column chromatography and preparative high performance liquid chromatography. Gas liquid chromatography analysis of methylated derivatives as well as MALDI-TOF MS and NMR measurements were used for structural confirmation. The 1H and 13C NMR signals of each saccharide were assigned using 2D-NMR including COSY, HSQC, HSQC-TOCSY, CH 2-HSQC-TOCSY, and CT-HMBC experiments. The saccharides were identified as β- d-fructopyranosyl-(2→6)-β- d-glucopyranosyl-(1→3)- d-glucopyranose and β- d-fructopyranosyl-(2→6)-[β- d-glucopyranosyl-(1→3)]- d-glucopyranose.

Ovarian Androgen Production in Postmenopausal Women

Context: Several studies previously reported that the postmenopausal ovary produces androgens. However, these findings have recently been questioned in a group of women with adrenal insufficiency. Objective: We sought to use contemporary assay methodologies to investigate whether the postmenopausal ovary is hormonally active and contributes to the circulating pool of androgens. Design and Patients: Serum was collected from the ovarian veins of 13 postmenopausal women undergoing total abdominal hysterectomy and bilateral oophorectomy, with sufficient quantities obtained to allow for measurement of several hormones. Serum was also analyzed from peripheral blood collected preoperatively, intraoperatively, and postoperatively. Setting: The study took place at the Los Angeles County Women’s and Children’s Hospital, University of Southern California Keck School of Medicine. Main Outcome Measures: Testosterone (T), androstenedione (A), dehydroepiandrosterone (DHEA), estrone (E1), and estradiol (E2) were measured by RIA with preceding organic solvent extraction and Celite column chromatography. Results: Statistically significant gradients were seen between the ovarian venous and peripheral samples for T, A, DHEA, E1, and E2. Postoperative levels of T and E1, but not A, DHEA, or E2, were statistically significantly lower than preoperative levels. A gradient for T between the ovarian venous and peripheral blood was present in four of five women who were menopausal for more than 10 yr. Conclusions: The postmenopausal ovary is hormonally active, contributing significantly to the circulating pool of T. Furthermore, this contribution appears to persist in women as long as 10 yr beyond the menopause. (J Clin Endocrinol Metab 92: 3040–3043, 2007)

Ovarian Androgen Production in Postmenopausal Women

Several studies previously reported that the postmenopausal ovary produces androgens. However, these findings have recently been questioned in a group of women with adrenal insufficiency. We sought to use contemporary assay methodologies to investigate whether the postmenopausal ovary is hormonally active and contributes to the circulating pool of androgens. Serum was collected from the ovarian veins of 13 postmenopausal women undergoing total abdominal hysterectomy and bilateral oophorectomy, with sufficient quantities obtained to allow for measurement of several hormones. Serum was also analyzed from peripheral blood collected preoperatively, intraoperatively, and postoperatively. The study took place at the Los Angeles County Women's and Children's Hospital, University of Southern California Keck School of Medicine. Testosterone (T), androstenedione (A), dehydroepiandrosterone (DHEA), estrone (E1), and estradiol (E2) were measured by RIA with preceding organic solvent extraction and Celite column chromatography. Statistically significant gradients were seen between the ovarian venous and peripheral samples for T, A, DHEA, E1, and E2. Postoperative levels of T and E1, but not A, DHEA, or E2, were statistically significantly lower than preoperative levels. A gradient for T between the ovarian venous and peripheral blood was present in four of five women who were menopausal for more than 10 yr. The postmenopausal ovary is hormonally active, contributing significantly to the circulating pool of T. Furthermore, this contribution appears to persist in women as long as 10 yr beyond the menopause.

Measurement of total testosterone in women: comparison of a direct radioimmunoassay versus radioimmunoassay after organic solvent extraction and celite column partition chromatography

To evaluate the clinical usefulness for the measurement of testosterone (T) values in the "low" female range with a direct radioimmunoassay (RIA) for total T by comparing total T values measured by this assay with values determined by conventional RIA after organic solvent extraction/column chromatography. Cross-sectional study. Victoria, Australia. Two hundred fifty-nine healthy women, aged 18-75 years, recruited from the community. Fasting serum samples were obtained and stored at -80 degrees C. Total T measurement. Total T was measured by the direct RIA method using antibody-coated tubes and iodine-labeled T tracer. For comparison, total T levels were also measured using the conventional RIA method after organic solvent (ethyl acetate:hexane [3:2]) extraction and celite column partition chromatography before RIA. The mean T level by direct RIA was 0.76 nmol/L (median, 0.70; SD, 0.54; minimum, 0.10; maximum, 3.2). The mean difference between the two measurements (direct RIA - conventional RIA) was -0.28 (SD, 0.3). The direct RIA value was 63% (95% confidence interval, 26%-155%) of the conventional RIA estimate. For the classification of values at the lower end of the range, there was very good agreement beyond chance (kappa = 0.68-0.74) for values in approximately the lowest 10th-40th percentiles. The direct RIA is a clinically useful assay for the study of the issue of "low" T within the female population.