New monolith technology for automated anion-exchange purification of nucleic acids

Synthetic nucleic acid analysis often employs pellicular anion-exchange (AE) chromatography because it supports very high efficiency separations while offering means to control secondary structure, retention and resolution by readily modifiable chromatographic conditions. However, these pellicular anion-exchange (pAE) phases do not offer capacity sufficient for lab-scale oligonucleotide (ON) purification. In contrast, monolithic phases produce fast separations at capacities exceeding their pellicular counterparts, but do not exhibit capacities typical of fully porous, bead-based, anion-exchangers. In order to further increase monolith capacity and obtain the selectivity and mass transfer characteristics of pellicular phases, a surface-functionalized monolith was coated with pAE nanobeads (latexes) usually employed on the pellicular DNAPac phase. The nanobead-coated monolith exhibited chromatographic behaviors typical of polymer AE phases. Based on this observation the monolithic substrate surface porosity and latex diameters were co-optimized to produce a hybrid monolith harboring capacity similar to that of fully porous bead-based phases and peak shape approaching that of the pAE phases. We tested the hybrid monolith on a variety of previously developed pAE capabilities including control of ON selectivity, resolution of derivatized ONs, the ability to resolve RNA ONs harboring aberrant linkages at different positions in a single sequence and separation of phosphorothioate diastereoisomers. We compared the yield and purity of an 8 mg ON sample purified on both the new hybrid monolith and a benchmark AE column based on fully porous monodisperse beads. This comparison included an assessment of the relative selectivities of both columns. Finally, we demonstrated the ability to couple AE ON separations with ESI-MS using an automated desalting protocol. This protocol is also useful for preparing ONs for other assays, such as enzyme treatments, that may be sensitive to high salt levels.

US Environmental Protection Agency Method 314.1, an automated sample preconcentration/matrix elimination suppressed conductivity method for the analysis of trace levels (0.50μg/L) of perchlorate in drinking water

Since 1997 there has been increasing interest in the development of analytical methods for the analysis of perchlorate. The US Environmental Protection Agency (EPA) Method 314.0, which was used during the first Unregulated Contaminant Monitoring Regulation (UCMR) cycle, supports a method reporting limit (MRL) of 4.0 microg/L. The non-selective nature of conductivity detection, combined with very high ionic strength matrices, can create conditions that make the determination of perchlorate difficult. The objective of this work was to develop an automated, suppressed conductivity method with improved sensitivity for use in the second UCMR cycle. The new method, EPA Method 314.1, uses a 35 mm x 4 mm cryptand concentrator column in the sample loop position to concentrate perchlorate from a 2 mL sample volume, which is subsequently rinsed with 10 mM NaOH to remove interfering anions. The cryptand concentrator column is combined with a primary AS16 analytical column and a confirmation AS20 analytical column. Unique characteristics of the cryptand column allow perchlorate to be desorbed from the cryptand trap and refocused on the head of the guard column for subsequent separation and analysis. EPA Method 314.1 has a perchlorate lowest concentration minimum reporting level (LCMRL) of 0.13 microg/L in both drinking water and laboratory synthetic sample matrices (LSSM) containing up to 1,000 microg/L each of chloride, bicarbonate and sulfate.

Comparison of two Cryptand separator columns for the determination of trace chloride in semiconductor-grade nitric acid

Improved ion-chromatographic approaches for measuring trace chloride in nitric acid are presented. Two columns, the IonPac Cryptand A1 and a higher-capacity Cryptand prototype, were tested and compared. Also, the use of a Continuously Regenerated Anion Trap Column (CR-ATC) was evaluated for its ability to purify electrolytically generated eluent. Nitric acid (70%) was used as the test matrix and chloride was used as the test analyte; prior to injection, the nitric acid was diluted to 0.7% for the A1 column and to 2.8% for the prototype column. Chloride could be quantified in only 20 min on either column; detection limits computed for 70% HNO3 (at 95% confidence, alpha = beta = 2.5%) were 1.8 and 1.5 ppm for the A1 and prototype columns, respectively. Results also showed that the CR-ATC was necessary for obtaining acceptable acid blanks.

Determination of chloride and sulfate in semiconductor-grade etchants comprised of acetic acid, nitric acid and phosphoric acid

The variable-capacity Dionex Cryptand A1 column was used for the determination of low-ppm levels of chloride and sulfate in etchants comprised of acetic acid, nitric acid and phosphoric acid. All possible ratios of the three acids could be analyzed for chloride and sulfate, if the samples were first diluted 1:100. However, a suitable eluent program was found to be needed for each mixture. A proprietary formulation was chosen to undergo this suitability determination. The resulting gradient was 10 mM KOH with a step to 30 mM NaOH at 15 min, flow-rate=0.5 ml/min; column temperature=29 degrees C; sample loop=7.5 microl. Under these conditions, a low-ppm calibration study (using the proprietary mix as the matrix) was performed and the associated prediction intervals were determined. At 50 ppm (in the original etchant), the +/- prediction interval was +/- 7 ppm for chloride and +/- 20 ppm for sulfate, both at the 95% confidence level. This step gradient was found to be a good starting place for separating the five components in all other ratios of these three acids.

Breast cancer screening behaviors and intentions among asymptomatic women 50 years of age and older

We examined predictors of (1) compliance with yearly mammography and clinical breast examination (CBE) and (2) intention to obtain mammography and CBE within the following year. Subjects were 312 asymptomatic female hospital employees, 50 years or older, who had participated in a free worksite breast cancer screening program. Mammograms and CBEs had been obtained by 79% and 76% of the subjects, respectively, during the preceding 12 months. The majority of the subjects indicated that they were very/extremely likely to obtain a mammogram and CBE in the next 12 months (88% and 87%, respectively). Multivariate analyses showed that perceived barriers to and physician recommendation of mammography were the strongest predictors of both breast cancer screening behaviors and intentions. Recency of participation in the educational component of the screening program was related to both compliance with mammography in the past 12 months and intention to obtain CBE in the next year. Having a first-degree female relative with a history of breast cancer was related to compliance with CBE in the past 12 months. Perceived efficacy of mammography was related to intention to obtain both mammography and CBE in the next year, and number of reasons for mammography was related to intention to obtain mammography in the next year. Our results suggest that physicians play a key role in motivating women to comply with breast cancer screening and that reducing barriers to obtaining mammography may increase use further.

Breast cancer screening: racial/ethnic differences in behaviors and beliefs

Racial/ethnic differences in breast cancer screening behaviors and beliefs were examined in 259 asymptomatic women, 50 years old or older, who participated in a no-cost worksite breast cancer screening program. Hispanics were more likely than African Americans to report having had mammography in the past year. Caucasians and Hispanics were more likely than African Americans to report having had a clinical breast examination in the past year. African Americans to report having had a clinical breast examination in the past year. African Americans and Hispanics were more likely to practice monthly breast self-examination than were Caucasians. African Americans were more likely to report cancer-related fears and worries as barriers to mammography, whereas Caucasians were more likely to report being too busy, inconvenience, and procrastination as barriers. African Americans also were more likely to evaluate their physicians and other health professionals positively than were Caucasians. These results suggest a need to make a special effort to address cancer-related fears as barriers to screening among African Americans, and time-related barriers to screening among Caucasians.

Color Doppler imaging in the subclavian-axillary region and upper extremity

Thirty-three patients were examined by color-coded Doppler ultrasound of the thoracoaxillary region or upper arm to review the utility of the method in this local area. The subclavian artery and vein were identified in all but one patient, in whom the subclavian vein was occluded and collateral vessels had developed. Masses and foreign bodies were easily distinguished from vascular abnormalities. Sonographic cephalic/basilic vein mapping was effective in seven patients. Carotid subclavian grafts were noted and evaluated appropriately in two patients. Color-coded sonography offered advantages in speed of localization of vessels and visual assessment of vessel location, direction of flow, turbulence, relationship to adjacent soft tissues, and detection of collateralization. Foreign body detection was not enhanced by color coding.

The effect of radiopharmaceutical incubation time on bone scan quality

Clinical variability in the quality of bone scans led to an evaluation of the effect of incubation time on the bone scanning agent as it affects the background quality of the scan. Results of the study suggest that an incubation time of 30 minutes produces optimal bone to soft-tissue ratios with 99mtechnetium methylene diphosphonate.

Unilateral pulmonary edema

Unilateral pulmonary edema was found to occur following or in conjunction with 18 different clinical situations. In half of them the edema developed on the same side as the causative factor and was related to conditions altering the delicate balance at the alveolar-capillary interface. In the other situations, pulmonary capillary perfusion was deficient on the opposite side prior to the onset of edema.