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PubMed2005

Sporicidal activity in liquid chemical products to sterilize or high-level disinfect medical and dental instruments.

BACKGROUND: Various liquid chemical products are commercially available in Mexico under sporicidal label claims. Frequently, information provided on their labels conflicts with published data on active ingredients, use concentrations, or exposure times. OBJECTIVE: To evaluate sporicidal activity in 8 chemical products sold for the sterilization or high-level disinfection of medical and dental instruments. METHODS: Bacillus atrophaeus ATCC 9372 spores were suspended (10 6 spores in 50 mL) in each of 4 glutaraldehyde solutions: a super oxidized solution, a hydrogen peroxide formulation, a quaternary ammonium compound, and an ortho -phthalaldehyde solution. After up to a 10-hour exposure, the solutions were passed through 0.22-mum filters, which were then rinsed with 1% sodium bisulfite, washed, and incubated on tryptic soy agar for 5 days at 37 degrees C. RESULTS: At the use concentrations stipulated on their labels, only 2 of 6 products registered as sterilants showed sporicidal activity when challenged with 6 log 10 : a 2% glutaraldehyde in 10 hours and the hydrogen peroxide solution in 6 hours. Of 2 products registered as high-level disinfectants, only the ortho -phthalaldehyde showed noticeable sporicidal activity after 10-hour exposure. CONCLUSION: The results show that some chemical products, commercially available in Mexico as "Liquid Chemical Sterilants/High-Level Disinfectants" cannot be used reliably to process instruments between patients.

Disinfectants↗
PubMed2003

Mutagenesis of SugE, a small multidrug resistance protein.

The small multidrug resistance protein family has two subclasses. In this study we used a mutation approach to see what is necessary to convert a SUG subgroup member into a quaternary ammonium compound (QAC) transporter. We chose four key residues (H24, M39, I43, and A44) conserved within SUGs but conserved differently within the QAC transporters. Altogether, seven mutants were generated in Citrobacter freundii SugE. Surprisingly, the mutated SugE demonstrated an increased sensitivity to representative QACs. Additionally, ethidium uptake is found to be more prominent in the hypersensitive mutants. We conducted orientation studies using topology reporter gene fusions which indicated that SugE and the QAC transporter EmrE both have their N- and C-termini in the cytoplasm as predicted. The results imply that SugE can be converted to a QAC transporter with only a single mutation. However, because hypersensitivity was observed, the SugE mutant proteins are behaving as importers rather than as exporters.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed2005

SMR proteins SugE and EmrE bind ligand with similar affinity and stoichiometry.

Suppressor of a groEL mutation protein E (SugE) is a small multidrug resistance (SMR) homologue. In comparison with other SMR proteins, SugE promotes bacterial resistance to a narrow range of quaternary ammonium compounds (QACs). Isothermal titration calorimetry was used to study the binding of QACs to Escherichia coli SugE in different membrane mimetic environments. In this study, the binding stoichiometry of SugE to drug was found to be 1:1, and the binding of SugE to drug was observed with the dissociation constant (K(D)) in the micromolar range for each of the drugs in the membrane mimetic environments explored. This interaction appears to be enthalpy-driven with enthalpies of 8-12 kcal/mol for each of the drugs. These results are similar to those found with drug binding to the SMR protein EmrE in an earlier study.

Amino Acid Sequence↗
PubMed2006

Synergistic effects of the anti-cholinergic R,R-glycopyrrolate with anti-inflammatory drugs.

Currently, much effort is geared towards developing therapies that impact on the inflammation in respiratory diseases such as asthma and COPD, assuming that this will improve disease pathology. R,R-Glycopyrrolate, a quaternary ammonium compound, is a muscarinic receptor antagonist with the potential to be used as a long-acting bronchodilator in patients with asthma and COPD. In this study we evaluated whether the combination of R,R-glycopyrrolate with known anti-inflammatory drugs results in synergistic effects. Human primary monocytes were used as an in vitro model system. M3, M4, M1 and M2 receptors were expressed in these cells in descending order. The combinatory effects of the drugs on the release of TNF-alpha after lipopolysaccharide stimulation were analyzed. R,R-Glycopyrrolate alone did not affect LPS induced TNF-alpha release. The PDE4 inhibitor rolipram dose dependently inhibited the TNF-alpha release. Maximum inhibition was around 70%. The IC(35) for rolipram was 68.9+/-15.2 nM. The simultaneous administration of 10 microM R,R-glycopyrrolate reduced the IC(35) to 1.70+/-1.18 nM. The anti-histamine azelastine inhibited TNF-alpha release dose dependently. The simultaneous administration of R,R-glycopyrrolate did not influence the action of azelastine. The corticosteroid budesonide inhibited the TNF-alpha release dose dependently with an IC(50) of 0.55+/-0.13 nM. The simultaneous administration of 10 microM R,R-glycopyrrolate reduced the IC(50) to 0.13+/-0.03 nM. Finally, R,R-glycopyrrolate was most effective in the triple combination with budesonide and rolipram in the reduction of TNF-alpha release. In conclusion, R,R-glycopyrrolate acts synergistically with the PDE4 inhibitor rolipram and the steroid budesonide in inhibiting inflammatory mediators.

Anti-Inflammatory Agents↗
PubMed2005

Determination of total and free plasma carnitine concentrations on the Dade Behring Dimension RxL: integrated chemistry system.

BACKGROUND: L-carnitine is a naturally occurring quaternary ammonium compound present in all mammalian species. Its major function is to facilitate the passage of long-chain fatty acids through the mitochondrial membrane for subsequent beta-oxidation and ketone synthesis. Clinical interest in carnitine disorders relates particularly to possible deficiency states that may result in a phenotypic spectrum that includes cardiomyopathy, skeletal myopathy, hypoglycemia and hyperammonemia. The objective of this study was to develop a method on the Dade Behring Dimension RxL analyzer for measuring free and total carnitine levels in plasma. METHODS: Plasma samples were deproteinized by ultrafiltration to remove interference by endogenous thiols. Filtrates were measured directly on the RxL for free carnitine or after alkaline hydrolysis for total carnitine by an endpoint enzymatic assay that uses carnitine acetyltransferase. RESULTS: Within-run imprecision was <5% at high and low levels for both free and total carnitine while between-day imprecision was <15%. Recovery of free carnitine from spiked plasma >90%. The method was linear between 5.0 and 150.0 micromol/l and the limit of quantification was 5.0 micromol/l. Comparison of our method with another automated procedure developed on the Hitachi 917 system using Deming regression analysis resulted in the following equations: Dimension=1.034(Hitachi)-7.44 for total carnitine (r=0.955) and Dimension=0.805(Hitachi)+1.96 for free carnitine (r=0.951), respectively. CONCLUSIONS: Our method is suitable for analyzer platforms where the level of imprecision is lower and the throughput is higher than manual methods. It also avoids the use of radioisotopes and is appropriate in labs where access to reference methods such as tandem mass spectrometry and HPLC is limited or unavailable.

Carnitine↗
PubMed2004

Rationalisation of unusual changes in efficiency and retention with temperature shown for bases in reversed-phase high-performance liquid chromatography at intermediate pH.

Despite the possibility of poorer peak shapes, analysis of pharmaceuticals and other bases using reversed-phase high-performance liquid chromatography (RP-HPLC) at intermediate pH gives useful increases in retention, selectivity and column loading capacity compared with low pH. Retention times of some bases showed anomalous increases with column temperature. Peak shapes for bases improved significantly at elevated temperature (up to 70 degrees C), with the weakest bases studied (pKa approximately 8) giving greater improvement than the strongest bases (pKa approximately 10). In contrast, quaternary ammonium compounds showed reduced retention with increasing column temperature (normal behaviour) and only modest improvements in peak shape. Considering these results, and pKa measurements of the bases made using capillary electrophoresis, it appears that increases in retention and improvement in efficiency may be influenced significantly by reduction in the pKa of bases with temperature, leading to reduction in protonation. It is less likely that efficiency improvements are due to the speeding up of the kinetics of silanol ion exchange, at least in the temperature range studied here.

Chromatography, High Pressure Liquid↗
PubMed2005

Effect of L-carnitine on nucleic acid status of aged rat brain.

The accumulation of damage to DNA plays a significant role in the etiology of the aging process. The importance of nutrition in delaying the aging process is well recognized. L-carnitine is a quaternary ammonium compound heterogeneously distributed in the brain. In the present study the effect of L-carnitine on DNA damage of various brain regions was investigated in a duration dependent way. Male albino rats aged 4 and 24 months were administered L-carnitine (300 mg/kg body weight/day) for 7,14 and 21 days. The activities of antioxidant enzymes, the levels of nucleic acids and the extent of DNA damage were measured in cortex, hippocampus, striatum, hypothalamus and cerebellum. Our results clearly showed that the activities of super oxide dismutase, glutathione peroxidase and the levels of DNA and RNA were significantly low in cortex, hippocampus and striatum of aged rat brain when compared with that of young rats. The regions that have lower antioxidants status are highly susceptible to oxidative DNA damage. Treatment with L-carnitine in aged rats enhanced the nucleic acid, antioxidant activity in a duration dependent manner with maximal effect after 21 days whereas no significant changes could be observed in the brain of young rats. These results suggest that that L-carnitine administration prevents age-related increment of DNA damage, thereby confirming the neuroprotective action of L-carnitine against aging.

Aging↗
PubMed2006

Effect of preinoculation growth media and fat levels on thermal inactivation of a serotype 4b strain of Listeria monocytogenes in frankfurter slurries.

Preinoculation growth conditions and fat levels were evaluated for effects on the heat resistance of Listeria monocytogenes strain MFS 102 in formulated frankfurter slurries and on frankfurter surfaces. Comparison of linear inactivation rates (D-values) for cells heated in frankfurter slurry showed that growth conditions were significant (P<0.05) factors affecting subsequent thermal resistance. The average D(60 degrees C)-values for the five preinoculation growth media tested from most resistant to least heat resistant were: tryptic soy broth with 0.6% yeast extract (TSBYE) (2.2 min) and 8.5% fat slurry (2.2 min), followed by 23% fat slurry (1.7 min) and 11% fat slurry (1.7 min), and then TSYBE with quaternary ammonium compounds added (TSBYE+Q) (1 min). The fat level in the frankfurter heating media also had a significant (P<0.05) effect on the thermal death rate of L. monocytogenes. Cells heated in 8.5% fat slurry had a significantly higher (P<0.05) D(60 degrees C)-value (2.2 min) than those heated in 11% fat (1.0 min) and 23% fat slurry (0.9 min). Growth media (TSBYE, 8.5% fat slurry, and TSBYE+Q), and fat level (15% and 20%), however, were not significant factors (P>0.05) affecting thermal inactivation rates on frankfurter surfaces. Heat inactivation rates were consistently higher on frankfurter surfaces compared to similar treatments done in frankfurter slurry. On frankfurter surfaces, a 2.3- to 5.1-log(10) reduction was achieved after 15 min depending on frankfurter surface type. The time necessary to achieve a 3-log(10) reduction using post-processing pasteurization of frankfurters in a hot water-bath at 60 degrees C almost doubled for cells grown in TSBYE and heated in 23% fat frankfurter slurry (19.6 min) versus cells grown and heated in 8.5% fat frankfurter slurry (10.8 min).

Animals↗
PubMed2004

Household cleaning and surface disinfection: new insights and strategies.

Recently, new insights into the persistence of pathogens, their transfer from inanimate surfaces to humans and the risk of contamination and dissemination of pathogens by detergents have been gained. Furthermore, new experimental data on the interruption of chains of infection by disinfectants as well as results of outbreak-control studies are now available. Hence it has become necessary to reassess the potential benefits using disinfectants to prevent and control nosocomial infections. Based on the new findings and in view of the increasing incidence of nosocomial infections and antibiotic resistances, the German Robert-Koch-Institut has issued completely revised recommendations on Household Cleaning and Surface Disinfection. With respect to these recommendations we developed a new test method, which allows comparison of the efficacy of disinfection in reducing the microbial loads and their dissemination with that of cleaning procedures under practical conditions. In a multi-factor approach, mechanical properties (wet mop technique), utensils (different mop materials) and active agents (disinfectant, detergent) were taken into consideration. We found that under the given conditions, dissemination of the test organism Staphylococcus aureus did not take place when using aldehydes and peroxides, it did take place, however, when water, surfactants, and the disinfectants glycol derivatives, quaternary ammonium compounds and alkylamines were used.

Colony Count, Microbial↗
PubMed2006

Using an efficient biofilm detaching agent: an essential step for the improvement of endoscope reprocessing protocols.

Biofilms develop inside endoscope channels even when valid endoscope reprocessing protocols are applied. The use of an efficient biocide is not sufficient if the channels are not cleaned thoroughly prior to disinfection. This study compared new anti-biofilm combinations of detachment promoting agents with a cleaning product in current use. Tests were performed using Teflon tubing and a contamination device that reproduces conditions that are prevalent during endoscopy. Products were subjected to static+brushing or dynamic treatments, and their ability to remove a preformed biofilm was assessed. The residual biofilm after treatment was assessed and compared with untreated controls. The percentage of surface covered by biofilm was measured after staining with crystal violet. Culturable bacteria levels were determined by plating the bacteria scraped from the tubing surface and counting the colony-forming units (CFU). Further tests were performed on actual endoscopes that had been contaminated artificially. Biofilm removal was confirmed by scanning electron microscopy. This study showed that the new anti-biofilm products prevented the build-up of biofilm and removed a mature biofilm (approximately 10(8)CFU/cm(2)), whereas protocols based on detergent-disinfectants containing quaternary ammonium compounds showed low efficacy as these protocols and products fixed the biofilm on the endoscope surfaces. The new procedure and agents represent a new approach to biofilm control that may improve the efficacy of endoscope reprocessing, and reduce the risk of transmitting infections.

Biofilms↗
PubMedDate not supplied

Role of carnitine esters in brain neuropathology.

L-Carnitine (L-C) is a naturally occurring quaternary ammonium compound endogenous in all mammalian species and is a vital cofactor for the mitochondrial oxidation of fatty acids. Fatty acids are utilized as an energy substrate in all tissues, and although glucose is the main energetic substrate in adult brain, fatty acids have also been shown to be utilized by brain as an energy substrate. L-C also participates in the control of the mitochondrial acyl-CoA/CoA ratio, peroxisomal oxidation of fatty acids, and the production of ketone bodies. Due to their intrinsic interaction with the bioenergetic processes, they play an important role in diseases associated with metabolic compromise, especially mitochondrial-related disorders. A deficiency of carnitine is known to have major deleterious effects on the CNS. Several syndromes of secondary carnitine deficiency have been described that may result from defects in intermediary metabolism and alterations principally involving mitochondrial oxidative pathways. Mitochondrial superoxide formation resulting from disturbed electron transfer within the respiratory chain may affect the activities of respiratory chain complexes I, II, III, IV, and V and underlie some CNS pathologies. This mitochondrial dysfunction may be ameliorated by L-C and its esters. In addition to its metabolic role, L-C and its esters such as acetyl-L-carnitine (ALC) poses unique neuroprotective, neuromodulatory, and neurotrophic properties which may play an important role in counteracting various disease processes. Neural dysfunction and metabolic imbalances underlie many diseases, and the inclusion of metabolic modifiers may provide an alternative and early intervention approach, which may limit further developmental damage, cognitive loss, and improve long-term therapeutic outcomes. The neurophysiological and neuroprotective actions of L-C and ALC on cellular processes in the central and peripheral nervous system show such effects. Indeed, many studies have shown improvement in processes, such as memory and learning, and are discussed in this review.

Brain↗
PubMed2005

Plasmid pB8 is closely related to the prototype IncP-1beta plasmid R751 but transfers poorly to Escherichia coli and carries a new transposon encoding a small multidrug resistance efflux protein.

The IncP-1beta plasmid pB8, which confers resistance to amoxicillin, spectinomycin, streptomycin, and sulfonamides, was previously isolated from a sewage treatment plant. It was found to possess abnormal conjugative transfer properties, i.e., transfer to Escherichia coli by conjugation or electroporation could not be detected. We showed in this study that plasmid pB8 is transferable to E. coli by conjugation, but only at low frequencies and under specific experimental conditions, a phenomenon that is very unusual for IncP-1 plasmids. Determination of the complete 57,198bp pB8 nucleotide sequence revealed that the backbone of the plasmid consists of a complete set of IncP-1beta-specific genes for replication initiation, conjugative plasmid transfer, stable inheritance, and plasmid control with an organisation identical to that of the prototype IncP-1beta plasmid R751. All of the minor differences in the pB8 backbone sequence compared to that of R751 were also found in other IncP-1beta plasmids known to transfer to and replicate in E. coli. Plasmids pB8 and R751 can be distinguished with respect to their accessory genetic elements. First, the pB8 region downstream of the replication initiation gene trfA contains two transposable elements one of which is similar to Tn5501. The latter transposon encodes a putative post-segregational-killing system and the small multidrug resistance (SMR) protein QacF, mediating quaternary ammonium compound resistance. The accessory genes in this region are not responsible for the poor plasmid transfer to E. coli since a pB8 deletion derivative devoid of all genes in that region showed the same conjugative transfer properties as pB8. A Tn5090/Tn402 derivative carrying a class 1 integron is located between the conjugative transfer modules. The Tn5090/Tn402 integration-sites are exactly identical on pB8 and R751 but in contrast to R751 the pB8 element carries the resistance gene cassettes oxa-2 for amoxicillin resistance and aadA4 for streptomycin/spectinomycin resistance, the integron-specific conserved segment consisting of the genes qacEDelta1, sul1, and orf5, and a truncated tni transposition module (tniAB). Although future work will have to determine the molecular basis for the poor transfer of pB8 to E. coli, our findings demonstrate that the host-range of typical IncP-1 plasmids may be less broad than expected.

Conjugation, Genetic↗
PubMed2006

The smr gene resides on a novel plasmid pSP187 identified in a Staphylococcus pasteuri isolate recovered from unpasteurized milk.

UNLABELLED: This work describes a novel plasmid pSP187 (5550 bp) carrying the small multidrug resistance determinant smr encoding resistance to quaternary ammonium compounds (QACs). pSP187 was identified in a Staphylococcus pasteuri isolate recovered from bulk milk in a dairy cattle herd in Norway. Sequence analysis revealed 6 putative ORFs in addition to the smr gene within a cassette with identical genetic organization to that found in the pSK41-like Staphylococcus aureus plasmid pTZ22. A protein homology search suggested the gene product of ORF7 to be a putative replication initiation protein, while ORF2 was predicted to encode a protein homologous to members of FtsK/SpoIIIE cell division-DNA segregation protein families. Sequence similarities to some initiator proteins of rolling circle replicons (RCR) indicated that pSP187 uses a RCR mode of replication, supported by the detection of intermediate ssDNA using S1 nuclease treatment and hybridization analysis. Interestingly, a 30-bp sequence found upstream from ORF7 showed high similarity to other dyad symmetry motifs proposed as putative double-strand origins of replication in the plasmids pGI3 (Bacillus thuringiensis), pSTK1 (Bacillus stearothermophilus), and pER1-2 (Streptococcus thermophilus). IN CONCLUSION: The novel smr-containing plasmid pSP187 is the first member of RCR group VI to be identified in a Staphylococcus sp.

Amino Acid Motifs↗
PubMed2007

Recycling of waste PET into useful textile auxiliaries.

Polyethylene terephthalate (PET) waste fibers were initially depolymerized using a glycolysis route in the presence of sodium sulfate as a catalyst, which is a commonly used chemical and ecofriendly as compared to heavy metal catalysts. Good yield of the pure monomer bis(2-hydroxyethylene terephthalate) (BHET) was obtained. Further, to attempt its reuse, the purified BHET was converted to different fatty amide derivatives to obtain quaternary ammonium compounds that have a potential for use as softener in the textile finishing process. The products were characterized by infrared spectroscopy. Application of these synthesized compounds was carried out on cotton fabric; they were evaluated for performance and were found to give good results. The chemicals used during depolymerization and reuse of PET are inexpensive and comparatively less harmful to the environment, and thus offer advantages in the chemical recycling of polyester waste fibers.

Conservation of Natural Resources↗
PubMed1997

Human placental cholinergic system.

The occurrence of acetylcholine (ACh)-like activity in human placenta, a tissue without innervation, has been known for more than 60 years. However, the non-neuronal functions of ACh in human placenta are not clearly understood. The components of the cholinergic system-ACh, choline acetyltransferase, acetylcholinesterase, butyrylcholinesterase, muscarinic receptors, and nicotinic receptors--in human placenta have been demonstrated by unequivocal methods. Primate placentae store and release ACh by mechanisms similar to those of nervous tissue. However, there are many gaps in our knowledge, which include: (a) endogenous quaternary ammonium compounds other than ACh in human placental extracts; (b) the specificity of placental enzymes; (c) the subtypes and structures of placental muscarinic and nicotinic receptors; and (d) the significance of placental alpha-bungarotoxin binding proteins, ACh receptor stimulation-cellular signaling by second messengers, and activation of immediate early target genes (C-fos, C-jun) encoding transcription factors. Several hypothetical non-neuronal functions of ACh in placenta have been postulated based upon available experimental evidence. These include: (a) regulation of blood flow and fluid volume in placental vessels; (b) opening and closing of trophoblastic channels; (c) induction of contractile properties to myofibroblasts; (d) facilitation of amino acid transport necessary for fetal growth across placenta; (e) release of placental hormones; and (f) modulation of the formation of myometrial and placental prostaglandins in human parturition. All of these roles are reasonable, and some of these roles mav turn out to be linked to one another to influence or maintain placental function.

Acetyl Coenzyme A↗
PubMed1999

Inactivation of Cryptosporidium parvum oocyst infectivity by disinfection and sterilization processes.

BACKGROUND: Cryptosporidium parvum is a common cause of self-limited gastroenteritis in the normal host but may cause severe disease in immunocompromised persons. Person-to-person transmission has been well documented in households, child care centers, and hospitals. Because contaminated environmental surfaces and medical devices such as endoscopes may play a role in disease transmission, we studied the susceptibility of C parvum to chemical agents commonly used for disinfection and evaluated the efficacy of sterilization processes. METHODS: Seven disinfectants were studied at their use dilution using a suspension test. Antimicrobial activity was assessed with the use of a cell infectivity assay. RESULTS: All sterilization processes tested (steam, ethylene oxide, Sterrad 100) inactivated 3 logs or greater of C parvum. The only liquid disinfectant/sterilant able to inactivate greater than 3 logs of C parvum was 6% and 7.5% hydrogen peroxide. Agents that did not completely inactivate C parvum included hydrogen peroxide at lower concentrations or exposure times, peracetic acid, sodium hypochlorite, a phenolic, a quaternary ammonium compound, 2% glutaraldehyde, and ortho-phthalaldehyde. CONCLUSIONS: Most high-level disinfectants used on endoscopes have limited efficacy against C parvum. However, the infectivity of C parvum on dry surfaces decreases rapidly. Therefore, current cleaning and high-level disinfection guidelines are adequate to prevent nosocomial transmission of C parvum by means of endoscopes.

Animals↗
PubMed2001

Quantitative determination of rocuronium in human plasma by liquid chromatography-electrospray ionization mass spectrometry.

Liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) was used for the quantification of the neuromuscular blocking agent rocuronium in human plasma. Verapamil was used as internal standard. The samples were subjected to a dichloromethane liquid-liquid extraction after ion pairing of the positively charged ammonium compound with iodide prior to LC-MS. Optimized conditions involved separation on a Symmetry Shield RP-18 column (50 x 2.1 mm, 3.5 microm) using a 15-min gradient from 10 to 90% acetonitrile in water containing 0.1% trifluoroacetic acid at 250 microl/min. Linear detector responses for standards were observed from 25 to 2,000 ng/ml. The extraction recovery averaged 59% for rocuronium and 83% for the internal standard. The limit of quantification (LOQ), using 500 microl of plasma, was 25 ng/ml. Precision ranged from 1.3 to 19% (LOQ), and accuracy was between 92 and 112%. In plasma samples, at 20 and 4 degrees C, rocuronium was stable at physiological pH for 4 h; frozen at -30 degrees C it was stable for at least 75 days. The method was found suitable for the analysis of samples collected during pharmacokinetic investigations in humans.

Androstanols↗
PubMed1980

Reverse-phase liquid chromatography of 5-fluorouracil nucleosides and nucleotides in the presence of quaternary ammonium ions.

Reversed-phase liquid chromatography is used for the separation of 5-fluorouracil, its deoxyribo- and ribonucleosides and nucleotides. The bases and nucleosides are easily separated from their naturally occurring analogues on an octadecyl silica column eluted with 2.10(-2) M KH2PO4 (pH 5.0) containing 5% (v/v) of methanol. This system can be applied to the measurement of 5-fluoro-2'-deoxyuridine serum levels down to 0.1 microgram/ml. Addition of small amounts (10(-3) M) of tetrabutylammonium phosphate to the eluent results in a large retention increase for the nucleotides, while the capacity ratios of the bases and nucleosides remain unchanged. The influence of the tetrabutylammonium phosphate and ammonium phosphate concentrations and pH of the eluent on the various k' values was investigated. Evidence is presented indicating that the quaternary ammonium compound is adsorbed onto the octadecyl silica surface: nucleotides are probably retained as adsorbed tetrabutylammonium ion-pairs.

Chromatography, Liquid↗