Fingerprinting of chlorinated paraffins and their transformation products in plastic consumer products

Chlorinated paraffins (CPs) can be classified according to their length as short-chain (SC, C10-C13), medium-chain (MC, C14-C17) and long-chain (LC, C ≥ 18) CPs. Technical CP-mixtures can contain a wide range of carbon- (C-, nC = 10-30) and chlorine- (Cl-, nCl = 3-19) homologues. CPs are high-production volume chemicals (>106 t/y). They are used as flame-retardants, plasticizers and coolant fluids. Due to the persistence, bioaccumulation, long-range environmental transport potential and adverse effects, SCCPs are regulated as persistent organic pollutants (POPs) by the Stockholm Convention. Transformation of CPs can lead to the formation of unsaturated compounds such as chlorinated mono- (CO), di- (CdiO) and tri-olefins (CtriO). Such transformation reactions can occur at different stages of CP manipulation providing characteristic C-/Cl-homologue distributions. All this results in unique patterns that collectively create a fingerprint, which can be distinguished from CP-containing samples. Therefore, CP-fingerprinting can develop into a promising tool for future source apportionment studies and with it, the reduction of environmental burden of CPs and hazards to humans. Herein, CP-containing plastics were studied to establish fingerprints and develop this method. We analyzed four household items by reverse-phase liquid-chromatography coupled with a mass spectrometer with an atmospheric pressure chemical ionization source and an Orbitrap mass analyzer (RP-LC-APCI-Orbitrap-MS) operated at a resolution of 120000 (FWHM at m/z 200). MS-data of different CP-, CO-, CdiO- and CtriO-homologues were efficiently processed with an R-based automatic mass spectra evaluation routine (RASER). From the 16720 ions searched for, up to 4300 ions per sample were assigned to 340 C-/Cl-homologues of CPs and their transformation products. Specific fingerprints were deduced from the C-/Cl-homologues distributions, the carbon- (nC) and chlorine- (nCl) numbers and saturation degree. These fingerprints were compared with the ones obtained by a GC-ECNI-Orbitrap-MS method.

Imaging the Chemistry of Materials Kinetics

The kinetics of most of chemical energy storage and conversion processes is rate-limited by the mass transport through matter. There is an uncertainty on the corresponding kinetic models, especially if based solely on kinetic theory. Henceforth analytical strategies coupled to setups, in order to capture data for overcoming this limitation are essential. Operando chemical imaging of the kinetics process supports the identification of rate-limiting barriers and definition of actionable kinetic insights. After an overview of the chemical and physical processes in various energy storage/conversion systems, and examples of chemical imaging applied on them, analytical challenges are discussed with particular focus on novel methods and fundamental limitations. Despite convincing success technologies, various scientific challenges of operando chemical kinetics await solution. Apart from technical improvements of the analysis instrumentation, promising developments are seen in advanced digital science.

Impurities in technical mixtures of chlorinated paraffins show AhR agonist properties as determined by the DR-CALUX bioassay

Chlorinated paraffins (CPs) are produced at more than one million tons per year. Technical CPs mixtures may contain impurities, which end up in consumer products. In the present study, 17 technical CPs mixtures were investigated for the potential occurrence of potential impurities. By applying the DR-CALUX bioassay, 3 out of 17 technical mixtures were shown to elicit responses at 4 h exposure time, but much lower at 48 h. Constitutional defined CPs materials did not show responses. Subsequently different groups of known AhR-agonists and compounds suspected to be present in technical CPs mixtures were investigated. Benzene, (poly)chlorobenzene, non-dioxin like polychlorinated naphthalenes (PCNs), and three-ringed polyaromatic hydrocarbons (PAHs) did not result in a significant response at 4 h or 48 h. TCDD, non-ortho PCBs, dioxin-like PCNs, four or five ringed PAHs and their chlorinated analogues resulted in a significant response. TCDD and the non-ortho PCBs showed the highest potency and stability, while dioxin-like PCNs, PAHs, and the chlorinated PAHs were clearly inactivated (metabolized) at longer incubation. Altogether, the present findings substantiate that AhR-mediated responses of CPs technical mixtures in the DR-CALUX bioassay are caused by impurities, most likely some intermediate stable AhR-agonists such as dioxin-like PCNs or (chlorinated) PAHs. The current study shows that impurities in CPs technical mixtures need to be investigated for assessing the safety of technical CPs mixtures.

Hemodialysis / hemofiltration: A report of a controlled cross-over study

In 14 stable ESRD patients an ABA cross-over study comparing conventional hemodialysis with post-dilution hemofiltration was performed in order to test the validity of clinical benefits reported for hemofiltration. No effect on blood-pressure could be observed in hypertensive hemofiltration patients when body weight was kept constant. The claimed positive effect of hemofiltration on hyperphosphatemia in dialysis patients could not be confirmed. A treatment with 3x18 I infusate per week seems to be insufficient treatment in regard to small molecule removal especially in heavy patients without any residual renal function. The decrease in urea nitrogen generation rate during the hemofiltration period might be the result of the lower small molecule removal in hemofiltration when compared to hemodialysis. The main clinical benefit of hemofiltration results from improved tolerance to volume removal due to improved hemodynamic stability during treatment.

Characterization of synthetic single-chain CP standard materials - Removal of interfering side products

The photolytic chlorination of n-alkanes in presence of sulfuryl chloride (SO₂Cl₂) was explored to produce new standard materials. Five mixtures of chlorinated tetradecanes were synthesized with chlorination degrees (m_Cl,EA) varying from 43.7% to 59.4% (m/m) based on elemental analysis. Chlorine-enhanced negative chemical ionization mass spectrometry (CE-NCI-MS) forcing the formation of chloride-adduct ions [M+Cl]^- was applied to characterize these materials which all contained tetra-to deca-chlorinated paraffins. Deconvolution of respective mass spectra revealed the presence of chlorinated olefins (COs). CO levels were highest in materials, which were exposed longest. All synthesized materials also contained two classes of polar impurities, tentatively assigned as sulfite- and sulfate-diesters with molecular formulas of C₁₄H_28-xO₃SCl_x (x = 1-4) and C₁₄H_28-xO₄SCl_x (x = 3-6), respectively. MS data were in accordance with the proposed structures but further work is needed to deduce their constitutions. These compounds are thermolabile and were not detected with GC-MS methods. We could remove these sulfur-containing impurities from the CPs with normal-phase liquid chromatography. In conclusion, single-chain CP materials were synthesized via chlorination of n-alkanes with sulfuryl chloride, but these materials contained reactive side products which should be removed to gain non-reactive and stable CP materials suitable as standards and for fate and toxicity studies.

Transformation of chlorinated paraffins to olefins during metal work and thermal exposure - Deconvolution of mass spectra and kinetics

Chlorinated paraffins (CPs) are high production volume chemicals widely used as additives in metal working fluids. Thereby, CPs are exposed to hot metal surfaces which may induce degradation processes. We hypothesized that the elimination of hydrochloric acid would transform CPs into chlorinated olefins (COs). Mass spectrometry is widely used to detect CPs, mostly in the selected ion monitoring mode (SIM) evaluating 2-3 ions at mass resolutions R < 20'000. This approach is not suited to detected COs, because their mass spectra strongly overlap with CPs. We applied a mathematical deconvolution method based on full-scan MS data to separate interfered CP/CO spectra. Metal drilling indeed induced HCl-losses. CO proportions in exposed mixtures of chlorotridecanes increased. Thermal exposure of chlorotridecanes at 160, 180, 200 and 220 °C also induced dehydrohalogenation reactions and CO proportions also increased. Deconvolution of respective mass spectra is needed to study the CP transformation kinetics without bias from CO interferences. Apparent first-order rate constants (k_app) increased up to 0.17, 0.29 and 0.46 h^-1 for penta-, hexa- and heptachloro-tridecanes exposed at 220 °C. Respective half-life times (τ_1/2) decreased from 4.0 to 2.4 and 1.5 h. Thus, higher chlorinated paraffins degrade faster than lower chlorinated ones. In conclusion, exposure of CPs during metal drilling and thermal treatment induced HCl losses and CO formation. It is expected that CPs and COs are co-released from such processes. Full-scan mass spectra and subsequent deconvolution of interfered signals is a promising approach to tackle the CP/CO problem, in case of insufficient mass resolution.

Stereoselective pharmacokinetics of ketamine and norketamine after racemic ketamine or S-ketamine administration during isoflurane anaesthesia in Shetland ponies

BACKGROUND

The arterial pharmacokinetics of ketamine and norketamine enantiomers after racemic ketamine or S-ketamine i.v. administration were evaluated in seven gelding ponies in a crossover study (2-month interval).

METHODS

Anaesthesia was induced with isoflurane in oxygen via a face-mask and then maintained at each pony's individual MAC. Racemic ketamine (2.2 mg kg(-1)) or S-ketamine (1.1 mg kg(-1)) was injected in the right jugular vein. Blood samples were collected from the right carotid artery before and at 1, 2, 4, 8, 16, 32, 64, and 128 min after ketamine administration. Ketamine and norketamine enantiomer plasma concentrations were determined by capillary electrophoresis. Individual R-ketamine and S-ketamine concentration vs time curves were analysed by non-linear least square regression two-compartment model analysis using PCNonlin. Plasma disposition curves for R-norketamine and S-norketamine were described by estimating AUC, C(max), and T(max). Pulse rate (PR), respiratory rate (R(f)), tidal volume (V(T)), minute volume ventilation (V(E)), end-tidal partial pressure of carbon dioxide (PE'(CO(2))), and mean arterial blood pressure (MAP) were also evaluated.

RESULTS

The pharmacokinetic parameters of S- and R-ketamine administered in the racemic mixture or S-ketamine administered separately did not differ significantly. Statistically significant higher AUC and C(max) were found for S-norketamine compared with R-norketamine in the racemic group. Overall, R(f), V(E), PE'(CO(2)), and MAP were significantly higher in the racemic group, whereas PR was higher in the S-ketamine group.

CONCLUSIONS

Norketamine enantiomers showed different pharmacokinetic profiles after single i.v. administration of racemic ketamine in ponies anaesthetised with isoflurane in oxygen (1 MAC). Cardiopulmonary variables require further investigation.

Antinociceptive effects, metabolism and disposition of ketamine in ponies under target-controlled drug infusion

Ketamine is widely used as an anesthetic in a variety of drug combinations in human and veterinary medicine. Recently, it gained new interest for use in long-term pain therapy administered in sub-anesthetic doses in humans and animals. The purpose of this study was to develop a physiologically based pharmacokinetic (PBPk) model for ketamine in ponies and to investigate the effect of low-dose ketamine infusion on the amplitude and the duration of the nociceptive withdrawal reflex (NWR). A target-controlled infusion (TCI) of ketamine with a target plasma level of 1 microg/ml S-ketamine over 120 min under isoflurane anesthesia was performed in Shetland ponies. A quantitative electromyographic assessment of the NWR was done before, during and after the TCI. Plasma levels of R-/S-ketamine and R-/S-norketamine were determined by enantioselective capillary electrophoresis. These data and two additional data sets from bolus studies were used to build a PBPk model for ketamine in ponies. The peak-to-peak amplitude and the duration of the NWR decreased significantly during TCI and returned slowly toward baseline values after the end of TCI. The PBPk model provides reliable prediction of plasma and tissue levels of R- and S-ketamine and R- and S-norketamine. Furthermore, biotransformation of ketamine takes place in the liver and in the lung via first-pass metabolism. Plasma concentrations of S-norketamine were higher compared to R-norketamine during TCI at all time points. Analysis of the data suggested identical biotransformation rates from the parent compounds to the principle metabolites (R- and S-norketamine) but different downstream metabolism to further metabolites. The PBPk model can provide predictions of R- and S-ketamine and norketamine concentrations in other clinical settings (e.g. horses).

Mass-spectrometry-linked screening of protein fractions for enzymatic activities--a tool for functional genomics

A simple and rapid strategy is described to screen protein fractions for defined enzymatic activity. A protein fraction from a porcine kidney extract was immobilized by covalent coupling to activated affinity beads. The immobilized proteins were incubated with probes specific for different enzyme activities. The reaction products were analyzed by matrix-assisted laser desorption/ionization (MALDI)-mass spectrometry. The MALDI spectra indicate the presence of 5'-nucleotidase, phosphatase, kinase, glutathione reductase, and renin activities in the kidney protein extract. Furthermore, the method can be used to screen for inhibitors of enzymatic reactions. The method is adaptable to high-throughput sample handling and automated mass spectrometric analysis and therefore suited for functional genomics.

Identification and characterization of diadenosine 5',5"'-P1,P2 -diphosphate and diadenosine 5',5"'-P1,P3-triphosphate in human myocardial tissue

We examined whether human cardiac tissue contains diadenosine polyphosphates and investigated their physiological role. Extracts from human cardiac tissue from transplant recipients were fractionated by size exclusion-, affinity-, anion exchange- and reversed-phase chromatography. MALDI-MS analysis of two absorbing fractions revealed molecular masses of 676.2 Da and 756.0 Da. The UV spectra of both fractions were identical to that of adenosine. Postsource decay MALDI mass spectrometry indicated that the molecules with a mass of 676.2 Da and 757.0 Da contained AMP and ATP, respectively. As shown by enzymatic cleavage, both molecules consist of two adenosines interconnected by either two or three phosphates in 5'-positions of the riboses. Two substances can be identified as 5',5"'-P1,P2-diphosphate (Ap2A) and 5',5"'-P1, P3-triphosphate (Ap3A). Ap2A and Ap3A, together with ATP and ADP, are stored in myocardial-specific granules in biologically active concentrations. In the isolated perfused rat heart, Ap2A and Ap3A caused dose-dependent coronary vasodilations. In myocardial preparations, Ap2A and Ap3A attenuated the effect of isoproterenol, exerting a negative inotropic effect. The calcium current of guinea pig ventricular myocytes, stimulated by isoproterenol, was also attenuated by Ap2A and Ap3A. The presence of Ap2A and Ap3A in cardiac-specific granules and the actions of these substances on the myocardium and coronary vessels indicate a role for these substances as endogenous modulators of myocardial functions and coronary perfusion.

T cell activation and thymic tolerance induction require different adhesion intensities of the CD8 co-receptor

Activation of mature lymphocytes requires in addition to the TCR contact with the corresponding antigen the binding of the CD8 or CD4 co-receptors to MHC class I or class II proteins respectively. To investigate the contribution of the CD8-class I interaction to the elimination of autoreactive T cells during negative selection in the thymus we generated two types of transgenic mice. One set expressed a modified Kb molecule which contained a human HLA-A2 alpha 3 domain, thereby missing the binding residues for the murine CD8 molecules. The second set of mice expressed an anti-Kb specific TCR. Both lines were crossed and in the resulting double transgenic mice the development of Kb-reactive T cells was followed with an anti-clonotypic antibody. Surprisingly, efficient clonal deletion in the thymus was still observed, although the reduced CD8-class I adhesion abrogated effector functions in vivo and in vitro. These results imply that even T cells with intermediate affinity for self are negatively selected in the thymus despite the fact that they are not able to react against self antigens in the periphery. Thus a safety window is created which decreases the risk of autoaggression.

[Subjective health and career status of former top athletes. A controlled 15-year follow-up study]

36 former Swiss elite athletes, all of them members of the National team in 1973, were re-examined in 1988 at an average age of 42 years, together with a control group of 23 normally active men. In 1988, maximum oxygen uptake (VO2max) was 68 +/- 5 ml/kg.min in the 18 still active runners, 55 +/- 8 ml/kg.min in the 9 inactive former runners, 45 +/- 6 ml/kg.min in bobsledders, and 44 +/- 6 ml/kg.min in controls. In 1988, the 27 runners had modest but significantly more frequent radiological signs of degenerative hip disease than non-runners, while no influence of long-term physical training on the radiological state of the ankle joint was found. In 1988, runners tended to report themselves healthier; subgroup analyses revealed 1) that this superior self-rated health was confined to those runners still active in 1988 (p less than 0.05) and that VO2max in 1988 was associated with subjective wellbeing (p less than 0.05), and 2) that body fat content was the strongest negative predictor of self-rated health (p = 0.001). 22% of former elite athletes indicated chronic, sports-related complaints but nevertheless rated their health as good as their athletic counterparts free of complaints. 53% of the elite athletes felt that the "benefits" of their own sports career outweighed its "costs", and in two of five of all athletes even "by far". This attitude was neither significantly influenced by the existence of chronic sports-related complaints nor by radiological signs of degenerative hip disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Fifteen-year changes in exercise, aerobic power, abdominal fat, and serum lipids in runners and controls

To describe effects of past as well as current exercise, aerobic power, and subcutaneous fat on the serum lipid profile, two groups of former elite athletes (N = 27 runners, N = 9 bobsledders) and a control group of normal men (N = 23) were investigated. Analysis of variance indicated a significant effect of the type of sports activity on HDL cholesterol, apolipoprotein A-I, and triglyceride levels and on the LDL/HDL cholesterol and apolipoprotein B/A-I ratios, with the most favorable values seen in runners and the least favorable values seen in controls. Of the 27 former elite runners, one third (N = 9) had given up or strongly reduced training. This subgroup showed the steepest 15-yr decrease (from 1973 to 1988) in maximum aerobic power and the largest 15-yr increase in subcutaneous fat, and the lipid profile (measured in 1988) corresponded more to the one of bobsledders and controls than to the one of runners who had remained active. Separate correlational analyses of all runners (N = 27) and nonrunners (N = 32) showed that, in both cohorts, i) the 1988 measurements of exercise, aerobic power, and subcutaneous fat were more predictive for the lipid profile in 1988 than the corresponding 1973 values, ii) anthropometric characteristics, especially abdominal fat, had a stronger relation with serum lipid concentrations than exercise and aerobic power, and iii) 15-yr changes in anthropometric characteristics were, but 15-yr changes in exercise and aerobic power were not, associated with triglyceride, lipoprotein, and apolipoprotein levels in 1988.(ABSTRACT TRUNCATED AT 250 WORDS)

[Risk of arthrosis of the upper ankle joint in long distance runners: controlled follow-up of former elite athletes]

To study the potential influence of long-term, high-intensity physical training on premature osteoarthrosis of the ankle joint, we re-examined former members of the Swiss National team from 1973 in retrospective cohort study in 1988. Twenty-seven track and field long-distance runners and orienteers (mean age 42 [95% confidence interval 41-43] years), 9 bobsledders (42 [39-46] years) and a control group of 23 healthy normal men (35 [33-36] years) were investigated. Physiological and exercise characteristics of all subjects had been recorded in 1973, and in 1988 these measurements were repeated together with a rheumatological and radiological examination of the ankle joint. A four-point scale of radiological joint state was used, taking into account the degree of subchondral sclerosis, osteophyte formation and joint space narrowing. In univariate analysis, the long-distance runners, and among them especially the orienteers (n = 10), showed significantly (both p less than 0.05) more radiological signs of degenerative ankle disease than controls. After adjustment for age, this difference disappeared. Age was itself significantly and positively related to radiological degenerative ankle disease (r less than 0.38; p less than 0.01). Orienteers reported significantly more frequently (60 vs 12%; p less than 0,01) functional instability of the ankle joint than track and field runners. Functional and mechanical (clinical) instability were interrelated in our material (r = 0.33; p less than 0.05) but neither of them was significantly related to radiological signs of degenerative ankle disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Is excessive running predictive of degenerative hip disease? Controlled study of former elite athletes

OBJECTIVE

To determine the effects of regular long distance running on the state of the hips in later life.

DESIGN

Retrospective study of a cohort of elite athletes and a group of normal, healthy, untrained controls examined 15 years after initial testing.

SETTING

Research project at school for physical education and sports.

SUBJECTS

27 Former long distance runners (mean age 42), nine former bobsleigh riders (mean age 42), and 23 normal, healthy, untrained men (mean age 35) who had been examined in 1973 and who agreed to re-examination in 1988.

MAIN OUTCOME MEASURE

Radiological evidence of degenerative hip disease in 1988.

RESULTS

Physiological and exercise characteristics of all subjects had been recorded in 1973, and in 1988 these measurements were repeated together with radiological examination of the hips. An additive radiological index of hip disease based on grades of subchondral sclerosis, osteophyte formation, and joint space narrowing was significantly increased among runners as compared with bobsleigh riders and untrained controls. After adjustment for age the significant effect of type of sports activity remained (p = 0.032). In multivariate analyses age and milage run in 1973 (97 km/week) emerged as independent, significant, and positive predictors of radiological signs of degenerative hip disease in 1988 (p = 0.017 and p = 0.024 respectively). Among runners alone running pace in 1973 rather than milage run was the stronger predictor of subsequent degenerative hip disease. The milage run in 1988 was not particularly predictive of the radiological index, but endurance in 1988 was inversely related to degenerative hip disease seen radiologically.

CONCLUSION

Long term, high intensity, high milage running should not be dismissed as a potential risk factor for premature osteoarthritis of the hip.

POMC in rhesus anterior pituitary and plasma: evidence of N-acetylated beta-endorphin and alpha-MSH

Pro-opiomelanocortin (POMC) related peptides have been studied in rat tissue and plasma, but they have not been well characterized in the rhesus monkey. Since monkey pituitary may be more similar to the human pituitary than the rat, we have characterized POMC related peptides by immunocytochemical, multiple radioimmunoassays (RIA's) and molecular sieving chromatography. Immunocytochemical staining demonstrated N-acetylated- beta-endorphin (N-Ac- beta-End) and alpha-MSH in a few corticotrophs. RIA's of crude anterior pituitary extract and molecular sieving chromatography demonstrates that the major portion is beta-End sized with a significant proportion being N-acetylated and an alpha-MSH peak. Molecular sieving chromatography of extracted plasma demonstrated a similar pattern to that seen in the anterior pituitary. These data suggest that rhesus monkey processes POMC differently than rat or man.

Some of the alpha-NH2-acetylated beta-endorphin-like material in rat and monkey pituitary and brain is acetylated alpha- and beta-endorphin

There are several studies demonstrating the existence of alpha-NH2-acetylated (N-Ac) forms of beta-endorphin in the intermediate lobe of several species (1,4,6). These include N-Ac-beta-endorphin (1-31), N-Ac-beta-endorphin (1-27) and N-Ac-beta-endorphin (1-26). The existence of N-acetylation of brain beta-endorphin is more controversial (5,6). Using molecular sieving, HPLC, and several radioimmunoassays, either directed at the midportion of beta-endorphin or at only N-acetylated opioids, we have studied brain multiple forms (cf. Akil, 1982). We have noted that little or no acetylation of beta-endorphin-sized material occurs in hypothalamus, and a small amount of N-acetylation appears to take place in the midbrain and the medulla. These results will be described in detail elsewhere (Akil et al., in preparation), but point the fact that processing of beta-endorphin (1-31) in brain is different than either lobe, with the production of beta-endorphin (1-27) and beta-endorphin (1-26) being more predominant in brain terminal areas than in the neuro-intermediate lobe. In the course of these experiments we noted the existence of a smaller-sized material which reacted with our N-acetyl-beta-endorphin antibody. The following study describes the partial characterization of this material as N-Ac-alpha- and N-Ac-beta-endorphin (i.e., the N-acetylated forms of beta-endorphin (1-17) and beta-endorphin (1-16).

Pharmacokinetics of ceftizoxime in patients undergoing hemodialysis

Serum pharmacokinetics of 1 g ceftizoxime were studied in eight patients undergoing chronic haemodialysis. Arterial blood samples were collected at 3, 60, 120, 180 and 240 minutes and before the next dialysis 2-3 days after injection of ceftizoxime. Three minutes after injection the serum levels were 122 +/- 8.4 microgram/ml and 19.4 +/- 1.7 microgram/ml at the end of the dialysis. Mean elimination half-life under haemodialysis was 2.1 hours. Serum concentrations ranged from 4.9 to 13 microgram/ml two to three days after the haemodialysis.

Hemodialysis/hemofiltration: a report of a controlled cross-over study

In 14 stable ESRD patients an ABA cross-over study comparing conventional hemodialysis with post-dilution hemofiltration was performed in order to test the validity of clinical benefits reported for hemofiltration. No effect on blood-pressure could be observed in hypertensive hemofiltration patients when body weight was kept constant. The claimed positive effect of hemofiltration on hyperphosphatemia in dialysis patients could not be confirmed. A treatment with 3x81 I infusate per week seems to be insufficient treatment in regard to small molecule removal especially in heavy patients without any residual renal function. The decrease in urea nitrogen generation rate during the hemofiltration period might be the result of the lower small molecule removal in hemofiltration when compared to hemodialysis. The main clinical benefit of hemofiltration results from improved tolerance to volume removal due to improved hemodynamic stability during treatment.

Evaluation of eight fluorochrome combinations for simultaneous DNA-protein flow analyses

Eight fluorescent dye combinations for simultaneous DNA-protein staining have been evaluated spectroscopically and flow microfluorometrically: propidium iodide (PI) with fluoresceinisothiocyanate (FITC), fluorescamine (FC), and dansylchloride (DANS); diamidinophenylindole (DAPII) with sulphorhodamin (SR101), tetramethylrhodamin isothiocyanate (TRITC), and nitrobenzodiazole (NBD); acriflavine (AF) with stilbene isothiocyanate sulphonic acid (SITS), and DAPI. Three different experimental tumor cell lines have been employed in the investigations. Simultaneous DNA-protein analyses have been carried out with the newly developed HEIFAS instrument. Spectroscopically two groups of dyes were distinguishable according to their excitation maximum below 400 nm and above 450 nm respectively. DANS and NBD were found to be unsatisfactory with respect to their protein distributions obtained by flow analysis. The remaining stains involved in the dye combination revealed comparable flow distributions of the cellular DNA and protein content. With respect to preparation time and number of centrifugal steps involved in the staining protocols, and in connection with the stability of the dye used, the DAPI-SR101 method proved to be fastest and easiest. With this combination DNA and protein flow analysis can be performed simultaneously within 30 min.