Nine prohibited stimulants found in sports and weight loss supplements: deterenol, phenpromethamine (Vonedrine), oxilofrine, octodrine, beta-methylphenylethylamine (BMPEA), 1,3-dimethylamylamine (1,3-DMAA), 1,4-dimethylamylamine (1,4-DMAA), 1,3-dimethylbutylamine (1,3-DMBA) and higenamine.

BACKGROUND: Weight loss and sports supplements containing deterenol have been associated with serious adverse events including cardiac arrest. OBJECTIVE: To determine the presence and quantity of experimental stimulants in dietary supplements labeled as containing deterenol sold in the United States. METHODS: Dietary supplements available for sale in the US and labeled as containing deterenol or one of its synonyms (e.g., isopropylnorsynephrine and isopropyloctopamine) were purchased online. For each brand, one container or subsample was analyzed by NSF International (Ann Arbor, MI) and one container or subsample by the Netherland's National Institute for Public Health and the Environment (RIVM, Bilthoven, The Netherlands). When differences existed between the two containers or subsamples of the same brand, both products were reanalyzed by Sciensano (Brussels, Belgium). NSF International carried out qualitative and quantitative analyses using ultra-high-performance liquid chromatography (UHPLC) quadrupole-Orbitrap mass spectrometry. RIVM performed qualitative and quantitative analysis using UHPLC quadrupole time-of-flight mass spectrometry. Sciensano carried out qualitative analysis using UHPLC quadrupole-Orbitrap mass spectrometry. RESULTS: Seventeen brands of supplements were analyzed. Many brands included more than one prohibited stimulant in the same product: 4 brands (24%, 4/17) included 2 stimulants, 2 (12%, 2/17) combined 3 stimulants, and 2 (12%, 2/17) combined 4 stimulants. The range of quantities per recommended serving size of the 9 stimulants detected were 2.7 mg to 17 mg of deterenol; 1.3 mg to 20 mg of phenpromethamine (Vonedrine); 5.7 mg to 92 mg of beta-methylphenylethylamine (BMPEA); 18 mg to 73 mg of octodrine; 18 mg to 55 mg of oxilofrine; 48 mg of higenamine; 17 mg of 1,3-dimethylamylamine (1,3-DMAA); 1.8 mg to 6.6 mg of 1,3-dimethylbutylamine (1,3-DMBA); and 5.3 mg of 1,4-dimethylamylamine (1,4-DMAA). CONCLUSION: Weight loss and sports supplements listing deterenol as an ingredient contained 9 prohibited stimulants and 8 different mixtures of stimulants, with as many as 4 experimental stimulants per product. These cocktails of stimulants have never been tested in humans and their safety is unknown.

Conformational study of octopamine in gas phase and effect of hydrochloride.

This work deals with the molecular modeling and vibrational spectra of all the twenty conformers of an important biomolecule octopamine which have been investigated using the DFT/B3LYP level of theory in combination with the 6-31++g(d,p) as a suitable basis set. The experimental FTIR and FTRaman spectra of octopamine neurotransmitter were recorded in the spectral region 400-4000 cm-1 and 50-4000 cm-1 respectively and correlated with the calculated spectra of the most stable conformer. The effect of hydrochloride on the important geometrical parameters of most stable conformer of octopamine was also studied. The normal coordinate analysis was performed to scale the theoretical frequencies and to calculate potential energy distributions for precise normal mode assignment. Most of the frequencies were in good agreement with experimental one. However, some have been modified. Natural bond orbital analysis was performed in order to confirm the stability of electronic structure of octopamine molecule. HOMO-LUMO analysis for all the twenty conformers was also performed to give the transition profile and to study the chemical reactivity of octopamine.

High sensitivity deep-UV LED-based z-cell photometric detector for capillary liquid chromatography.

A new high sensitivity deep-UV LED photometric detector with a z-type flow cell (45 nL or 180 nL) for miniaturised and portable capillary liquid chromatography (LC) was designed and fabricated to overcome sensitivity limitations due to short pathlength in on-capillary detectors. The new detector has a 10 mm geometric pathlength and uses high intensity light-emitting diodes (LED) as light sources in the deep-UV range (254 nm and 280 nm). No optical reference was necessary due to the low drift in the signal. Stray light was minimized by the use of an adjustable slit with a 0.5 mm pinhole. The direct relationship between absorbance and concentration was obtained using dichromate to evaluate the sensitivity and the linearity range of the detector. Performance of the miniaturised version was compared with that obtained from a commercial benchtop detector for capillary LC under the same conditions using the same optical z-cell. The miniaturised version exhibited a superior performance across all parameters, including 3 times higher effective pathlength, 4 times higher upper limit of detector linearity, and 2-5 times lower stray light levels. An application of the new detector was shown with the detection of l-dopa, l-tyrosine, norfenefrine, phenylephrine and tyramine, separated using capillary LC. The baseline noise level recorded was as low as 3.9 µAU. Further, the detector was applied in a miniaturised capillary LC for the indirect detection of common inorganic anions. In comparison to an on-capillary LED detector applied under similar chromatographic conditions, there was a 50 times higher signal to noise (S/N) ratio.

Quantification of Biogenic Amines from Individual GFP-Labeled Drosophila Cells by MALDI-TOF Mass Spectrometry.

Cell-cell communication plays a crucial role in orchestrating and modulating neural circuits. To understand such interactions, it is vital to determine and quantify the involved messenger molecules such as neuropeptides and biogenic amines on the level of single cells. In this study, we used single-cell mass spectrometry (SCMS) to qualify and quantify octopamine (OA) and tyramine (TA) from isolated single cells from intact brains of the fruit fly Drosophila melanogaster. Our workflow involved targeted GFP-guided single-cell microdissection, on-plate chemical derivatization with 4-hydroxy-3-methoxycinnamaldehyde (CA) or 2,5-dimethyl-1 H-pyrrole-3,4-dicarbaldehyde (DPD) for increasing ion stability and ion signal intensity, and isotopically marked internal standards for quantification by MALDI-TOF MS. We were able to determine a limit of detection for OA of 1 fmol/µL, for TA of 2.5 fmol/µL and a lower limit of quantification (LLOQ) of 10 fmol/µL for both substances. SCMS of GFP-labeled somata from ventral midline neurons of the labial neuromere (VMlb) of the gnathal ganglion revealed an OA titer of 17.38 fmol/µL and a TA titer (∼2.5 fmol/µL) lower than the LLOQ, independent of sex. However, using a genetically altered driver line devoid of OA, TßhnM18/Tdc2 > GFP, we confirmed TA in these cells. Furthermore, cold-anesthetization of flies caused a significant increase in OA content in VMlb somata. We compared OA titers of somata from two different OA/TA cell clusters to demonstrate the usefulness of targeted SCMS in advancing our understanding of OA/TA signaling in behavior and physiology. An influence on the detection of neuropeptides by our derivatized SCMS method could be excluded.

Octopamine and tyramine modulate the thermoregulatory fanning response in honey bees (Apis mellifera).

Biogenic amines regulate the proximate mechanisms underlying most behavior, including those that contribute to the overall success of complex societies. For honey bees, one crucial set of behaviors contributing to the welfare of a colony is involved with nest thermoregulation. Worker honeybees cool the colony by performing a fanning behavior, the expression of which is largely influenced by response thresholds modulated by the social environment. Here, we examined how changes in biogenic amines affect this group-performed thermoregulatory fanning behavior in honeybees. Concentrations of two biogenic amines, octopamine and tyramine, are significantly lower in active fanners than in non-fanners, but there is no difference in dopamine and serotonin concentrations. Direct feeding of octopamine and tyramine induced a decrease in fanning responses, but only when both amines were included in the treatment. This is the first evidence that fanning behavior is influenced by these two biogenic amines, and this result is consistent with the typical role of these neurotransmitters in regulating locomotor activity in other insects. Individual variation in amine expression also provides a mechanistic link that helps to explain how this group behavior might be coordinated within a colony.

Learning, gustatory responsiveness and tyramine differences across nurse and forager honeybees.

Honeybees are well known for their complex division of labor. Each bee sequentially performs a series of social tasks during its life. The changes in social task performance are linked to gross differences in behavior and physiology. We tested whether honeybees performing different social tasks (nursing versus foraging) would differ in their gustatory responsiveness and associative learning behavior in addition to their daily tasks in the colony. Further, we investigated the role of the biogenic amine tyramine and its receptors in the behavior of nurse bees and foragers. Tyramine is an important insect neurotransmitter, which has long been neglected in behavioral studies as it was believed to only act as the metabolic precursor of the better-known amine octopamine. With the increasing number of characterized tyramine receptors in diverse insects, we need to understand the functions of tyramine on its own account. Our findings suggest an important role for tyramine and its two receptors in regulating honeybee gustatory responsiveness, social organization and learning behavior. Foragers, which were more responsive to gustatory stimuli than nurse bees and performed better in appetitive learning, also differed from nurse bees in their tyramine brain titers and in the mRNA expression of a tyramine receptor in the brain. Pharmacological activation of tyramine receptors increased gustatory responsiveness of nurse bees and foragers and improved appetitive learning in nurse bees. These data suggest that a large part of the behavioral differences between honeybees may be directly linked to tyramine signaling in the brain.

Predator exposure-induced immunosuppression: trade-off, immune redistribution or immune reconfiguration?

Although predator exposure increases the risk of wound infections, it typically induces immunosuppression. A number of non-mutually exclusive hypotheses have been put forward to explain this immunosuppression, including: trade-offs between the immune system and other systems required for anti-predator behaviour, redistribution of immune resources towards mechanisms needed to defend against wound infections, and reconfiguration of the immune system to optimize defence under the physiological state of fight-or-flight readiness. We tested the ability of each hypothesis to explain the effects of chronic predator stress on the immune system of the caterpillar Manduca sexta Predator exposure induced defensive behaviours, reduced mass gain, increased development time and increased the concentration of the stress neurohormone octopamine. It had no significant effect on haemocyte number, melanization rate, phenoloxidase activity, lysozyme-like activity or nodule production. Predator stress reduced haemolymph glutathione concentrations. It also increased constitutive expression of the antimicrobial peptide attacin-1 but reduced attacin-1 expression in response to an immune challenge. These results best fit the immune reconfiguration hypothesis, although the other hypotheses are also consistent with some results. Interpreting stress-related changes in immune function may require an examination at the level of the whole organism.

Variability of Stimulant Levels in Nine Sports Supplements Over a 9-Month Period.

Many studies have found that some dietary supplement product labels do not accurately reflect the actual ingredients. However, studies have not been performed to determine if ingredients in the same dietary supplement product vary over time. The objective of this study was to assess the consistency of stimulant ingredients in popular sports supplements sold in the United States over a 9-month period. Three samples of nine popular sports supplements were purchased over the 9-month period. The 27 samples were analyzed for caffeine and several other stimulants (including adulterants). The identity and quantity of stimulants were compared with stimulants listed on the label and stimulants found at earlier time points to determine the variability in individual products over the 9-month period. The primary outcome measure was the variability of stimulant amounts in the products examined. Many supplements did not contain the same number and quantity of stimulants at all time points over the 9-month period. Caffeine content varied widely in five of the six caffeinated supplements compared with the initial measurement (-7% to +266%). In addition, the stimulants-synephrine, octopamine, cathine, ephedrine, pseudoephedrine, strychnine, and methylephedrine-occurred in variable amounts in eight of the nine products. The significance of these findings is uncertain: the sample size was insufficient to support statistical analysis. In our sample of nine popular sports supplements, the presence and quantity of stimulants varied over a 9-month period. However, future studies are warranted to determine if the variability found is significant and generalizable to other supplements.

Direct and mediated electrochemistry of peroxidase and its electrocatalysis on a variety of screen-printed carbon electrodes: amperometric hydrogen peroxide and phenols biosensor.

This study compares the behaviour of direct and mediated electrochemistry of horseradish peroxidase (HRP) immobilised on screen-printed carbon electrodes (SPCEs), screen-printed carbon electrodes modified with carboxyl-functionalised multi-wall carbon nanotubes (MWCNT-SPCEs) and screen-printed carbon electrodes modified with carboxyl-functionalised single-wall carbon nanotubes (SWCNT-SPCEs). The techniques of cyclic voltammetry and amperometry in the flow mode were used to characterise the properties of the HRP immobilised on screen-printed electrodes. From measurements of the mediated and mediatorless currents of hydrogen peroxide reduction at the HRP-modified electrodes, it was concluded that the fraction of enzyme molecules in direct electron transfer (DET) contact with the electrode varies substantially for the different electrodes. It was observed that the screen-printed carbon electrodes modified with carbon nanotubes (MWCNT-SPCEs and SWCNT-SPCEs) demonstrated a substantially higher percentage (≈100 %) of HRP molecules in DET contact than the screen-printed carbon electrodes (≈60 %). The HRP-modified electrodes were used for determination of hydrogen peroxide in mediatorless mode. The SWCNT-SPCE gave the lowest detection limit (0.40 ± 0.09 µM) followed by MWCNT-SPCE (0.48 ± 0.07 µM) and SPCE (0.98 ± 0.2 µM). These modified electrodes were additionally developed for amperometric determination of phenolic compounds. It was found that the SWCNT-SPCE gave a detection limit for catechol of 110.2 ± 3.6 nM, dopamine of 640.2 ± 9.2 nM, octopamine of 3341 ± 15 nM, pyrogallol of 50.10 ± 2.9 nM and 3,4-dihydroxy-L-phenylalanine of 980.7 ± 8.7 nM using 50 µM H2O2 in the flow carrier.

Monoclonal antibody-based immunoassay for analysis of octopamine in housefly.

Octopamine (OA) is one of the biogenic monoamines in the housefly, which acts as an important neurohormone in the physiological process of this pest. In this study, a new hapten of OA was synthesized via aldol condensation. With the hapten, monoclonal antibodies (MAb) were generated and their characterizations were investigated. An indirect competitive enzyme-linked immunosorbent assay (icELISA) based on MAb 3C11-E3 was established, which required simple sample pre-treatments and had low cross-reactivity with OA structural analogise. The half maximal inhibition concentration (IC50) and the detected range (IC20-IC80) of the icELISA were 128 ng/mL and 12-1438 ng/mL, respectively. Average recoveries of OA ranged from 73 to 129% in the housefly.

3D-printed and CNC milled flow-cells for chemiluminescence detection.

Herein we explore modern fabrication techniques for the development of chemiluminescence detection flow-cells with features not attainable using the traditional coiled tubing approach. This includes the first 3D-printed chemiluminescence flow-cells, and a milled flow-cell designed to split the analyte stream into two separate detection zones within the same polymer chip. The flow-cells are compared to conventional detection systems using flow injection analysis (FIA) and high performance liquid chromatography (HPLC), with the fast chemiluminescence reactions of an acidic potassium permanganate reagent with morphine and a series of adrenergic phenolic amines.

Determination of synephrine and octopamine in bitter orange peel by HPTLC with densitometry.

This paper presents the development and validation of an improved method for the simultaneous analysis of synephrine and octopamine using high-performance thin-layer chromatography with densitometric detection. Separation was performed on silica gel 60F254 plates. The mobile phase is comprised of methanol, ethylacetate, methylene chloride and concentrated ammonia (2:2:1:0.05, v:v:v:v). The Rf values were 0.292 ± 0.0083 and 0.413 ± 0.0089 for synephrine and octopamine, respectively (n = 9). Ultraviolet absorbance detection at 277 nm was used for the alkaloids detection. Specificity, accuracy (recovery rates were between 96 and 99%) and precision (in both cases intra-day precision and inter-day precision were ≤ 2.0%) of the method were determined. Their amounts were calculated using the regression equations of the calibration curves which were linear in the range 0.2-1.2 µg/spot. The amounts of alkaloids in basic methanolic extracts of bitter orange peel measured by the method were 0.253 and 0.142% for synephrine and octopamine, respectively. Most of the factors evaluated in the robustness test were found to have an insignificant effect on the selected responses at 95% confidence level. The method was validated giving rise to a dependable and high-throughput procedure well suited to routine application.

Determination of octopamine and tyramine traces in dietary supplements and phytoextracts by high performance liquid chromatography after derivatization with 2,5-dimethyl-1H-pyrrole-3,4-dicarbaldehyde.

The use of 2,5-dimethyl-1H-pyrrole-3,4-dicarbaldehyde (DPD) as a pre-column derivatization reagent for HPLC (high performance liquid chromatography) analysis of octopamine (oct) and tyramine (tyr) is proposed. The compound reacts under mild conditions (2 min at ambient temperature) with primary amino groups. The derivatization conditions were optimized by considering different parameters (temperature, time and reagent concentration). The synthesized oct and tyr adducts were characterized by (1)H NMR (nuclear magnetic resonance), ESI-MS (electrospray ionization mass spectrometry), IR (infrared) and UV (ultraviolet). Derivative chromatographic separations were performed on a Sinergy Hydro-RP column (150 mm × 4.6 mm i.d.) using a mobile phase consisting of methanol and triethylammonium phosphate buffer (pH 3; 10mM) at varying composition gradient elution and at a flow rate of 0.8 mL/min. Detection was set at λ=320 nm. The obtained results were compared with those achieved by a validated direct HPLC method with detection at λ=275 nm using a Sinergy Polar-RP column (250 mm × 3 mm i.d.) by isocratic elution conditions with a mobile phase consisting of methanol/acetonitrile/sodium pentanesulphonate (SPS; pH 3; 10mM), 7.5:7.5:85 (v/v/v) at a flow rate of 0.3 mL/min. Derivatization method sensitivity proved to be ten times higher than direct method. Limit of detection of oct and tyr was 0.010 and 0.008 µg/mL, respectively. The reliability of the pre-column method was satisfactory also in terms of linearity (from 0.028 to 1.255 and 0.024 to 1.244 µg/mL for oct and tyr, respectively), precision (relative standard deviation ≤2, without significant differences between intra-day and inter-day data) and recovery (from 98.9 to 101.2%). The proposed method showed to be suitable for a reliable determination of oct and tyr traces in commercially available phytoproducts using the instrumentation usually present in any analytical laboratory.

Development of an ionic liquid-based ultrasonic-assisted liquid-liquid microextraction method for sensitive determination of biogenic amines: application to the analysis of octopamine, tyramine and phenethylamine in beer samples.

A simple and efficient method, ionic liquid-based ultrasound-assisted liquid-liquid microextraction, has been developed for the determination of three biogenic amines including octopamine (OCT), tyramine (TYR) and phenethylamine (PHE). Fluorescence probe 2,6-dimethyl-4-quinolinecarboxylic acid N-hydroxysuccinimide ester was applied for derivatization of biogenic amines and high-performance liquid chromatography coupled with fluorescence detection was used for the determination of the derivatives. The factors affecting the extraction efficiency, such as the type and volume of ionic liquid, ultrasonication time and centrifugation time have been investigated in detail. Under the optimum conditions, linearity of the method was observed in the range of 0.5-50 µgmL(-1) for OCT and TYR, and 0.025-2.5 µgmL(-1) for PHE, respectively, with correlation coefficients (γ)>0.996. The limits of detection ranged from 0.25-50 ngmL(-1) (S/N=3). The spiked recoveries of three target compounds in beer samples were in the range of 90.2-114%. As a result, this method has been successfully applied for the sensitive determination of OCT, TYR and PHE in beer samples.

Biogenic amines, caffeine and tonic immobility in Tribolium castaneum.

Biogenic amines are physiologically neuroactive substances that affect behavioural and physiological traits in invertebrates. In the present study, the effects of dopamine, octopamine, tyramine and serotonin on tonic immobility, or death-feigning, were investigated in Tribolium castaneum. These amines were injected into the abdomens of beetles artificially selected for long or short duration of tonic immobility. In beetles of the long strains, the durations of tonic immobility were shortened by injection of dopamine, octopamine and tyramine, and the effects of these amines were dose-dependent. On the other hand, serotonin injection did not affect the duration of tonic immobility. In the short-strain beetles that rarely feign death, no significant effects of the amines were found on the duration of tonic immobility. Brain expression levels of octopamine, tyramine and serotonin did not differ between long- and short-strain beetles, in contrast to the higher dopamine levels in short strains previously reported. Caffeine decreased the duration of death-feigning in both oral absorption and injection experiments. It is known that caffeine activates dopamine. Therefore, the present results suggest that the duration of tonic immobility is affected by dopamine via the dopamine receptor in T. castaneum.

Descending unpaired median neurons with bilaterally symmetrical axons in the suboesophageal ganglion of Manduca sexta larvae.

Three large median cell bodies with a diameter between 40 and 70 microm that exhibit octopamine immunoreactivity were identified in the posterior part of the suboesophageal ganglion of the tobacco hawkmoth larva, Manduca sexta. These neurons possess bilaterally symmetrical axons in the posterior neck connectives, and at least one of them extends through the whole ventral nerve cord to the terminal abdominal ganglion. Therefore, these neurons belong to the class of descending ventral unpaired median neurons. From each cell body, a primary neurite ascends anteriorly, which after bending dorsally turns posteriorly and then bifurcates to give rise to two descending axons. From the primary neurite two main dendritic branches ascend anteriorly, and four characteristic branches can be distinguished originating from them: two descending dendritic branches and two ascending dendritic branches. Dense arborizations from all these branches exist in all neuromeres of the suboesophageal ganglion. Intracellular recordings from these neurons show that in contrast to the ventral unpaired median neurons of thoracic and abdominal ganglia, they do not produce overshooting action potentials but exhibit passive soma spikes only. During pharmacologically evoked fictive motor patterns these neurons show coupling to various motor patterns such as crawling, feeding and molting.

Fast-scan cyclic voltammetry for the detection of tyramine and octopamine.

Tyramine and octopamine are biogenic amine neurotransmitters in invertebrates that have functions analogous to those of the adrenergic system in vertebrates. Trace amounts of these neurotransmitters have also been identified in mammals. The purpose of this study was to develop an electrochemical method using fast-scan cyclic voltammetry at carbon-fiber microelectrodes to detect fast changes in tyramine and octopamine. Because tyramine is known to polymerize and passivate electrode surfaces, waveform parameters were optimized to prevent passivation. No fouling was observed for octopamine when the electrode was scanned from 0.1 to 1.3 V and back at 600 V/s, while a small decrease of less than 10% of the signal was seen for 15 repeated exposures to tyramine. The technique has limits of detection of 18 nM for tyramine and 30 nM for octopamine, much lower than expected levels in insects and lower than basal levels in some brain regions of mammals. Current was linear with concentration up to 5 microM. This voltammetry technique should be useful for measuring tyramine and octopamine changes in insects, such as the fruit fly, Drosophila melanogaster.

Dendritic projections of different types of octopaminergic unpaired median neurons in the locust metathoracic ganglion.

Octopaminergic dorsal unpaired median (DUM) neurons of locust thoracic ganglia are important components of motor networks and are divided into various sub-populations. We have examined individually stained metathoracic DUM neurons, their dendritic projection patterns, and their relationship to specific architectural features of the metathoracic ganglion, such as longitudinal tracts, transverse commissures, and well-defined sensory neuropils. The detailed branching patterns of individually characterized DUM neurons of various types were analyzed in vibratome sections in which architectural features were revealed by using antibodies against tubulin and synapsin. Whereas DUM3,4,5 and DUM5 neurons (the group innervating leg and "non-wing-power" muscles) had many ventral and dorsal branches, DUM1 and DUM3,4 neurons (innervating "wing-power" muscles) branched extensively only in dorsal areas. The structure of DUM3 neurons differed markedly from that of the other DUM neurons examined in that they sent branches into dorsal areas and had differently structured side branches that mostly extended laterally. The differences between the branching patterns of these neurons were quantified by using currently available new reconstruction algorithms. These structural differences between the various classes of DUM neurons corresponded to differences in their function and biophysical properties.

Determination of Bitter Orange alkaloids in dietary supplements standard reference materials by liquid chromatography with ultraviolet absorbance and fluorescence detection.

Four adrenergic amines [synephrine, octopamine, tyramine, and n-methyltyramine] were determined in a variety of Bitter Orange containing dietary supplements. Two extraction techniques were evaluated in detail: Soxhlet extraction and sonication extraction. A liquid chromatographic separation using a reversed-phase C(18) stationary phase and the ion-pairing reagent sodium dodecyl sulfate was developed to separate the Bitter Orange alkaloids. Ultraviolet absorbance detection at 220 nm and fluorescence detection with excitation at 273 nm and emission at 304 nm were used for the alkaloid detection. The method described was used for the assignment of the levels of the predominant alkaloids in three candidate standard reference materials containing Bitter Orange.

A multichannel native fluorescence detection system for capillary electrophoretic analysis of neurotransmitters in single neurons.

A laser-induced native fluorescence detection system optimized for analysis of indolamines and catecholamines by capillary electrophoresis is described. A hollow-cathode metal vapor laser emitting at 224 nm is used for fluorescence excitation, and the emitted fluorescence is spectrally distributed by a series of dichroic beam-splitters into three wavelength channels: 250-310 nm, 310-400 nm, and >400 nm. A separate photomultiplier tube is used for detection of the fluorescence in each of the three wavelength ranges. The instrument provides more information than a single-channel system, without the complexity associated with a spectrograph/charge-coupled device-based detector. With this instrument, analytes can be separated and identified not only on the basis of their electrophoretic migration time but also on the basis of their multichannel signature, which consists of the ratios of relative fluorescence intensities detected in each wavelength channel. The 224-nm excitation channel resulted in a detection limit of 40 nmol L-1 for dopamine. The utility of this instrument for single-cell analysis was demonstrated by the detection and identification of the neurotransmitters in serotonergic LPeD1 and dopaminergic RPeD1 neurons, isolated from the central nervous system of the well-established neurobiological model Lymnaea stagnalis. Not only can this system detect neurotransmitters in these individual neurons with S/N>50, but analyte identity is confirmed on the basis of spectral characteristics.