Measurement of diffusive flux of ammonia from water

An instrument was developed for the measurement of gaseous ammonia concentration, NH(3(sw,eq)), in equilibrium with surface waters, notably ocean water. The instrument measures the ammonia flux from a flowing water surface under defined conditions and allows the calculation of NH(3(sw,eq)) from the principles of Fickian diffusion. The flux collector resembles a wetted parallel plate denuder previously developed for air sampling. The sample under study runs on one plate of the device; the ammonia released from the sample is collected by a slow flow of a receptor liquid on the other plate. The NH(3) + NH(4)(+) (hereinafter called N(T)) in the effluent receptor liquid is preconcentrated on a silica gel column and subsequently measured by a fluorometric flow injection analysis (FIA) system. With a 6-min cycle (4-min load, 2-min inject), the analytical system can measure down to 0.3 nM N(T) in the receptor liquid. Coupled with the flux collector, it is sufficiently sensitive to measure the ammonia flux from seawater. The instrument design is such that it is little affected by ambient ammonia. In both laboratory (N(T) 0.2-50 μM), and field investigations (N(T) 0.18-1.7 μM) good linearity between the ammonia flux and the N(T) concentration in seawater (spiked, synthetic, natural) was observed, although aged seawater, with depleted N(T) content, behaves in an unusual fashion upon N(T) addition, showing the existence of an "ammonia demand". NH(3(sw,eq)) levels from ocean water measured in the Coconut Island Laboratory, HI, ranged from 6.6 to 33 nmol/m(3) with an average of 17.4 ± 6.9 nmol/m(3), in comparison to 2.8-21 nmol/m(3) (average 10 ± 7 nmol/m(3)) NH(3(sw,eq)) values previously reported for the Central Pacific Ocean (Quinn, P. K.; et al. J. Geophys. Res. 1990, 95, 16405-16416).     

Preparation, characterization, and application of an enzyme-immobilized magnetic microreactor for flow injection analysis

Enzyme-immobilized magnetic microparticles (EMMP) have been prepared for use as a microreactor in flow injection analysis (FI). The microparticles were directly injected into the FI system. Their retention occurred within the flow line by small permanent magnets located near the detector. The analytical utility of this concept was illustrated by the assay of glucose using glucose oxidase (GOx), immobilized microparticles, and amperometric detection of liberated hydrogen peroxide. The microparticles were derived from silica gel (nominal pore diameter, 15-80 nm) by impregnation with a citric acid/ethanol solution and a ferric nitrate/ethanol solution and then by calcination in a nitrogen atmosphere to produce ferrimagnetic fine particles of spinel-type iron oxide (gamma-Fe(2)O(3)) inside the pore. They were characterized by X-ray diffraction. The calibration curve of the glucose sample (2 microL injected) was linear between 2.5 x 10(-6) and 5 x 10(-4) mol/L (R = 0.9995), and the detection limit was 1.0 x 10(-6) mol/L or 0.36 ng of injected glucose (S/N = 3). The repeatability for a 5 x 10(-4) mol/L glucose solution was RSD = 1.5% (n = 6). Application to the assay of glucose in a fermentation broth is illustrated. The GOx MMP were stable and active for more than eight months when kept at 10 degrees C.     

Ammonia detection by using quantum-cascade laser photoacoustic spectroscopy

A pulsed quantum-cascade distributed-feedback laser, temperature tunable from -41 degrees C to +31.6 degrees C, and a resonant differential photoacoustic detector are used to measure trace-gas concentrations to as low as 66 parts per 10(9) by volume (ppbv) ammonia at a low laser power of 2 mW. Good agreement between the experimental spectrum and the simulated HITRAN spectrum of NH3 is found in the spectral range between 1046 and 1052 cm(-1). A detection limit of 30 ppbv ammonia at a signal-to-noise ratio of 1 was obtained with the quantum-cascade laser (QCL) photoacoustic (PA) setup. Concentration changes of approximately 50 ppbv were detectable with this compact and versatile QCL-based PA detection system. The performance of the PA detector, characterized by the product of the incident laser power and the minimum detectable absorption coefficient, was 4.7 x 10-9 W cm(-1).     

A flow injection on-line multiplexed sorption preconcentration procedure coupled with flame atomic absorption spectrometry for determination of trace lead in water, tea, and herb medicines

One of the limitations in previous flow injection (FI) sorption preconcentration procedures in a knotted reactor (KR), which have been carried out exclusively with a single continuous sample injection over a certain period, is the relatively low retention efficiency (typically 40-50%). Although the sensitivity of such systems could be improved by properly increasing sample preconcentration time, sample loading flow rate, or both, further improvement of the sensitivity has been limited by the narrow linearity of the relationship between signal intensity and preconcentration time or sample loading time. In this work, a novel on-line FI multiplexed sorption preconcentration procedure with repetitive sample injections was developed to overcome the above problems in the previous systems. In contrast to previous FI preconcentration systems, the proposed multiplexed preconcentration procedure evenly divides a single longer sample injection step into several shorter substeps while the total preconcentration time is still kept constant. To demonstrate its merits, the proposed FI on-line KR multiplexed sorption preconcentration system was combined with flame atomic absorption spectrometry (FAAS) for determination of trace lead in water, tea, and herb medicines. The lead in the sample solution on-line reacted with ammonium pyrrolidine dithiocarbamate, and the resultant analyte complex was sorbed on the inner walls of the KR. The residual sample solution was then removed from the KR with an air flow. The above two steps were repeated eight times with a total preconcentration time of 120 s. The sorbed analyte was eluted from the KR with 4.5 mol L(-1) HCl for on-line FAAS detection. The present multiplexed preconcentration procedure with eight repetitive sample injections for a total preconcentration time of 120 s gave a retention efficiency of 92%, twice that obtained by one single sample injection preconcentration (47%). In addition, the linear ranges of the diagrams of absorbance against sample loading flow rate and sample loading time were extended, offering more potential for achieving high sensitivity by increasing sample loading rates or sample loading time compared to the previous one single continuous sample injection preconcentration procedure. At a sample loading flow rate of 3.6 mL min(-1) for a total preconcentration period of 120 s, an enhancement factor of 57 and a detection limit (3sigma) of 8 microg L(-1) were obtained. The precision was 1.4% (RSD, n = 11) at the 200 microg L(-1) level. The developed method was successfully applied to the determination of trace lead in various water samples, herb medicines, and a certified tea reference material.     

Optimization and characterization of a flow injection electrochemical system for pentachlorophenol assay

A flow injection (FI) electrochemical detection system has been developed and optimized for the determination of pentachlorophenol (PCP) in contaminated soil. PCP was oxidized to tetrachloro-1,4-benzoquinone (1,4-TCBQ) with a high yield using bis(trifluoroacetoxy)iodobenzene in 0.1 M tartaric acid, pH 2.0, at ambient temperature. Upon rapid reaction with immobilized glucose oxidase, the detection and amplification scheme was completed as the reduced form of 1,4-TCBQ or tetrachloro-1,4-hydroquinone was reoxidized to 1,4-TCBQ at the surface of the glassy carbon electrode (+ 0.40 V vs Ag/AgCl). Rapid electron exchange between the enzyme and its glucose substrate provided a non-rate-limiting current toward the electrode. The FI electrochemical system was linear up to 1 μM oxidized PCP with a detection limit of 10 nM and exhibited a reproducibility of ±0.6% over 165 repeated analyses during 14 h of continuous operation. When applied to PCP-contaminated soil samples, the results obtained from the FI electrochemical system compared well with those of the HPLC standard method.     

Miniature Personal Ozone Monitor Based on UV Absorbance

A new portable instrument has been developed that offers rapid detection of ozone at the ppb level for personal exposure monitoring. The Personal Ozone Monitor is based on the EPA Federal Reference Method of UV absorbance and has the advantage of being small (10 × 7.6 × 3.8 cm), light-weight (0.3 kg), low power (2.9 watts), and battery-operated. The instrument can be worn by an individual during normal daily activities because it is unaffected by humidity, physical orientation, temperature, and vibration. In order to eliminate any significant interference from water vapor, Nafion(?) tubing was installed before the detection cell, and the optical path was lined with quartz. A precision of 1.5 ppbv and limit of detection of 4.5 ppbv (S/N = 3) was demonstrated with the instrument making measurements every 10 seconds.     

A miniaturized liquid core waveguide-capillary electrophoresis system with flow injection sample introduction and fluorometric detection using light-emitting diodes

A novel miniaturized capillary electrophoresis (CE) system is described where a Teflon AF-coated silica capillary serves both as the separation channel and as a transversely illuminated liquid core waveguide. This device uniquely uses flow injection (FI)-based split-flow sample introduction through a falling-drop interface. An H-channel structure fixed on a microscope glass slide utilizes a horizontal separation capillary with tubular sidearms on each end that serve as inlet and outlet flow-through electrode reservoirs. The inlet reservoir also functions as a falling-drop interface for coupling to the FI system. A blue LED is used as excitation source. A large-core optical fiber takes the emitted fluorescence to an inexpensive PMT with two layers of green plastic used for optical filtering. No focusing arrangement is needed. Continuous FI introduction of a series of 30-microL samples containing a mixture of of fluorescein isothiocyanate (FITC)-labeled amino acids allowed a throughput rate up to 144 samples/ h, with approximately 2% carryover and good precision (3.2% RSD). Baseline separation was achieved for FITC-labeled arginine, phenylalanine, glycine, and FITC in sodium tetraborate buffer (pH 9.5) with plate heights of 5.4-5.5 microm and plate numbers of 2.34 x 10(4)-2.37 x 10(4) under electrical field strengths of 214 V/cm for injection and 500 V/cm for separation (14-cm capillary, 48-microm i.d.). Detection limits (S/N = 3) were 1.3 microM for arginine and 1.9 microM for phenylalanine and glycine.     

Capillary electrochromatography-mass spectrometry of nonionic surfactants

The Triton X (TX)-series are alkylphenol polyethoxylates -type nonionic surfactants of varying numbers of ethylene oxide units. Applications include industrial and household detergent formulations as well as emulsifying agents. For analysis of these surfactants, capillary electrochromatography-electrospray ionization-mass spectrometry (CEC-ESI-MS) offers several unique advantages over the traditional hyphenation methods based on HPLC-MS. These include higher plate numbers attainable in CEC-MS, as well as more compatible flow rate (submicroliter) when coupled to ESI-MS and, perhaps most importantly, less consumption of toxic and costly organic solvents. In this work, different CEC-ESI-MS parameters such as mobile-phase composition, sheath liquid, and spray chamber parameters were optimized to provide suitable and sensitive analysis of short-, medium-, and long-chain length (e.g., n = 1-16) TX-series nonionic surfactants. The optimized CEC-ESI-MS conditions were mobile phase containing 90/10 ACN/2.5 mM Tris, pH 8, sheath liquid containing 50/50 MeOH/10 mM HCO(2)NH(4) delivered at 5 microL/min, spray chamber set to drying gas flow of 6 mL/min, nebulizer pressure of 5 psi, and drying gas temperature set to 200 degrees C. This optimization is followed by the more challenging separation of very long chain TX-series with a large number (n = 30-70) of ethoxy units, which were initially found to exhibit extreme retention using the developed method. It was observed that through the addition of small volume fraction of polar-aprotic tetrahydrofuran solvent to the running buffer, the retention time could be significantly reduced thus enhancing the feasibility for CEC-ESI-MS analysis of these very long chain nonionic surfactants for the first time. The detection limit was approximately 37 microg/mL total octylphenol ethoxylate for TX-45; acceptable precision of migration time (<1% RSD, n = 3) and peak area ( approximately 4% RSD, n = 3) were achieved.     

Feasibility of collection and analysis of airborne carbonyls by on-sorbent derivatization and thermal desorption

The most commonly used method for analysis of airborne carbonyls is to collect the analytes on solid sorbents coated with a suitable derivatization agent, followed by solvent desorption and liquid injection for analysis by high-pressure liquid chromatography. We have explored a new approach by combining on-sorbent derivatization and thermal desorption to measure airborne carbonyls. More specifically, carbonyls in the air are collected onto an O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA)-coated Tenax sorbent packed in a tube with dimensions identical to those of a gas chromatography (GC) injector liner. The derivatives are then released by in-injection port thermal desorption to a GC column for analysis. Gaseous carbonyls, including formaldehyde, acetaldehyde, benzaldehyde, glyoxal, and methylglyoxal, at ppbv levels are shown to be effectively collected (> or = 92% collection efficiency) onto the sampling tubes at a flow rate of 20 mL/min under both < 1% and 71% relative humidity. The collection efficiency drops as the sampling flow rate increases, and the degree of decrease is compound dependent. The derivatization agent, at a level of approximately 127 nmol/tube, is thermally desorbed and eluted from the GC column without compromising the determination of any carbonyl-PFBHA derivatives. Detection limits of low ppbv to sub-ppbv are achieved for a sample air volume of 4.8 L. Using this new method, we have measured formaldehyde, acetaldehyde, benzaldehyde, glyoxal, and methylglyoxal to be 4.9-16.3, 0.6-8.2, <5.9, 0.5-4.1, and <2.4 ppbv, respectively, in the ambient atmosphere at the university bus stop. This method is less labor intensive than the solvent desorption technique and avoids use of organic solvents. Other classes of airborne polar species can be measured through the same approach by selecting an appropriate derivatization agent.     

流动注射—超声雾化器—电感耦合等离子体原子发射光谱(FI-ICP/AES)联用技术同时测定头发中多种元素

建立了 FI-UN-ICP/AES 联用技术,用所发展技术进行了头发中多种微量元素的同时测定。与常规气动雾化器 ICP/AES 技术相比,尽管是用流动注射方法引入样品,测定的检出限仍有较大改进(2—23倍)。多次注射测定的再现性(RSD)在0.6—5.0%范围内。同时进行了标准加入回收试验,获得了很好的结果(90—110%)。     

Trace detection of atmospheric NO2 by laser-induced fluorescence using a GaN diode laser and a diode-pumped YAG laser

We report on the development of a highly sensitive detection system for measuring atmospheric NO(2) by means of a laser-induced fluorescence (LIF) technique at 473 nm using a diode-pumped Nd:YAG laser. A GaN-based laser diode emitting at 410 nm is also used as an alternative fluorescence-excitation source. For laboratory calibrations, standard NO(2) gas is diluted with synthetic air and is introduced into a fluorescence-detection cell. The NO(2) LIF signal is detected by a photomultiplier tube and processed by a photon-counting method. The minimum detectable limits of the NO(2) instrument developed have been estimated to be 0.14 ppbv and 0.39 ppbv (parts per billion, 10(-9), by volume) in 60 s integration time (signal-to-noise ratio of 2) for 473 and 410 nm excitation systems, respectively. Practical performance of the instrument has been demonstrated by the 24 hour continuous measurements of ambient NO(2) in a suburban area.     

Synthesis of an ammonium ionophore and its application in a planar ion-selective electrode

A modular technique was used to synthesize an ammonium-selective ionophore based on a cyclic depsipeptide structure. The ionophore was incorporated into a planar ion-selective electrode sensor format and the selectivity tested versus a range of metal cations in a commercial clinical diagnostic "point-of-care" instrument. Four sensor membrane formulations were tested, all of which consisted of plasticized PVC. Formulations differed as to the type of plasticizer used and whether an ionic additive was present. It was found that the membrane containing the polar plasticizer nitrophenyl octyl ether in the absence of ionic additive exhibited near-Nernstian behavior (slope, 60.1 mV/decade at 37 degrees C) and possessed high selectivity for ammonium ion over lithium and the divalent cations, calcium and magnesium (log K(POT)NH4+(j) = -7.3, -4.4, and -7.1 for lithium, calcium, and magnesium ions, respectively). The same membrane also exhibited sodium and potassium selectivity that was comparable to that reported for nonactin (log K(POT)NH4+(j) = -2.1 and -0.6 for sodium and potassium, respectively, compared to -2.4 and -0.9 in the case of nonactin). Membranes containing the less polar plasticizer, dioctyl phthalate, showed sub-Nernstian behavior (slope, <50 mV/decade at 37 degrees C). In all cases, the presence of the ionic additive potassium tetrakis(4-chlorophenyl)borate substantially reduced the selectivity observed. The flexible modular synthetic technique developed and reported here will allow the cyclic depsipeptide structure to be tuned for optimum selectivity.     

A photothermal interferometer for gas-phase ammonia detection

Detection of gas-phase ammonia is particularly challenging because ambient ammonia concentrations may be less than 1 ppb (molecules of NH(3) per 10(9) molecules of air), ammonia sticks to many materials commonly used to sample air, and particles containing ammonium may interfere with gas-phase measurements. We have built a new and sensitive photothermal interferometer to detect gas-phase ammonia in situ, under typical atmospheric conditions. Ammonia molecules in sampled air absorb infrared radiation from a CO(2) laser at 9.22 μm, with consequent collisional heating, expansion, and refractive index change. This change in refractive index is detected as a phase shift in one arm of a homodyne interferometer. Measurements of vibrational and electrical noise in the interferometer correlate to an instrumental lower limit of detection of 6.6 ppt ammonia in 1 s. The CO(2) laser output is modulated at 1.2 kHz, and the ac signal from the interferometer is measured with a lock-in amplifier. The detector is zeroed by sampling through a H(3)PO(4)-coated denuder tube and is calibrated by dynamic dilution of two permeation tube outputs and by standard addition. Signal gain is insensitive to CO(2) or H(2)O in the sample, and the signal is linear over 5 orders of magnitude. The instrument 2σ precision is 31 ppt when the signal is integrated for 100 s and 250 ppt with a 1-s integration time. The windowless sample cell and inlet is fabricated entirely of glass to minimize sample loss and hysteresis. The instrument response time is demonstrated to be about 1 s.     

Surfactant-assisted synthesis of Keggin-type polyoxometalates nanorods

It was demonstrated that Keggin-type polyoxometalates nanorods (POMs-nanorods) were prepared from a solution containing a surfactant polyethylene glycol (PEG), when heteropolyanions [X(n+)M12O40](-(8-n)) (X(n+) = P5+ and Si4+; M = W and Mo) were precipitated by ammonia ion obtained by hydrolysis of urea at 373 K. In this method, PEG was used as a template and ammonia ion (NH4+) was a counterion. In an oil bath kept at 373 K without stirring, three kinds of ammonium salts of POMs, i.e., (NH4)3PW12O40, (NH4)4SiW12O40, and (NH4)3PMo12O40 nanorods were obtained. The POMs-nanorods were characterized by transmission electron microscopy (TEM), selected area electron diffraction (SAED), infrared spectra (IR), inductively coupled plasma atomic emission spectrometry (ICP-AES) and X-ray powder diffraction (XRD). TEM showed that nanorods were 0.5-1.5 microm in length, and 50-150 nm in diameter. The results of IR, ICP-AES and XRD proved the existence of Keggin structure. The formation process of POMs-nanorods, (NH4)(8-n) [X(n+)M12O40](-(8-n)) (X(n+) = P5+ and Si4+; M = W and Mo) in a H2O/PEG system was discussed.     

High-throughput nanoliter sample introduction microfluidic chip-based flow injection analysis system with gravity-driven flows

In this work, a simple, robust, and automated microfluidic chip-based FIA system with gravity-driven flows and liquid-core waveguide (LCW) spectrometric detection was developed. The high-throughput sample introduction system was composed of a capillary sampling probe and an array of horizontally positioned microsample vials with a slot fabricated on the bottom of each vial. FI sample loading and injection were performed by linearly moving the array of vials filled alternately with 50-microL samples and carrier, allowing the probe inlet to enter the solutions in the vials through the slots sequentially and the sample and carrier solution to be introduced into the chip driven by gravity. The performance of the system was demonstrated using the complexation of o-phenanthroline with Fe(II) as a model reaction. A 20-mm-long Teflon AF 2400 capillary (50-microm i.d., 375-microm o.d.) was connected to the chip to function as a LCW detection flow cell with a cell volume of 40 nL and effective path length of 1.7 cm. Linear absorbance response was obtained in the range of 1.0-100 microM Fe(II) (r2=0.9967), and a good reproducibility of 0.6% RSD (n=18) was achieved. The sensitivity was comparable with that obtained using conventional FIA systems, which typically consume 10,000-fold more sample. The highest sampling throughput of 1000 h-1 was obtained by using injection times of 0.08 and 3.4 s for sample and carrier solution, respectively, with a sample consumption of only 0.6 nL for each cycle.     

GaAs表面硫钝化工艺新研究

为得到GaAs表面稳定的钝化层,以(NH4)2S为主要对象,首先研究不同溶剂对钝化效果的影响,得出溶液极性越小,钝化效果越好的结论;研制出一种新的钝化溶液:Se+(NH4)2S+叔丁醇。通过光致发光(PL)谱对比(NH4)2S+去离子水、(NH4)S2+异丙醇、(NH4)2S+叔丁醇、Se+(NH4)2S+叔丁醇等几种不同含硫溶液钝化GaAs(100)表面的发光特性。通过测试PL发光谱发现,Se+(NH4)2S+叔丁醇溶液处理的GaAs(100)表面发光强度最强,是未做钝化处理的25倍左右。钝化处理后的基片在空气中放置数小时,PL谱未见明显退化。得出Se+(NH4)2S+叔丁醇不论从发光强度还是稳定性来说,都是较为理想的钝化溶液。     

Comprehensive on-line characterization of complex gas mixtures by quasi-simultaneous resonance-enhanced multiphoton ionization, vacuum-UV single-photon ionization, and electron impact ionization in a time-of-flight mass spectrometer: setup and instrument characterization

This paper reports on a newly developed mobile mass spectrometer for comprehensive on-line analysis of complex gas mixtures such as ambient air or industrial process gases. Three ionization methods, namely, the resonance-enhanced multiphoton ionization (REMPI), vacuum-ultraviolet single-photon ionization (SPI), and electron impact ionization (EI) are implemented in this instrument and can be operated (quasi-) simultaneously. By means of this setup, a wide range of compounds can be analyzed due to the unique ionization selectivitiy and sensitivity profiles provided by the different ionization techniques. The mass spectrometer is designed for field application even under severe conditions. The REMPI technique is suitable for the selective and soft ionization (without fragmentation) of aromatic compounds at trace level (ppbv/pptv). The also soft but less selective SPI technique with 118-nm vacuum-ultraviolet laser pulses is used as a second laser-based ionization method. Mass spectra obtained by this technique show profiles of most organic compounds (aliphatic and aromatic species) and of some low IP inorganic substances (e.g., ammonia, nitrogen oxide) down to ppbv concentrations. In addition to the laser-based ionization techniques, EI ionization can be used for analysis of the bulk components such as water, oxygen, nitrogen, and carbon dioxide as well as for detection of inorganic minor components such as HCN or HCl from combustion flue gases at ppmv concentration levels. Each method yields specific mass spectrometric information of the sample composition. Special techniques have been developed to combine the three ionization methods in a single mass spectrometer and to allow the quasi-parallel application of all three ionization techniques.     

Ultrasensitive, visible tunable diode laser detection of NO(2)

Recent advances in room-temperature visible diode lasers and ultrasensitive detection techniques have been exploited to create a highly sensitive tunable diode laser absorption technique for in situ monitoring of NO(2) in the lower troposphere. High sensitivity to NO(2) is achieved by probing the visible absorption band of NO(2) with an AlGalnP diode laser at 640 or 670 nm combined with a balanced ratiometric electronic detection technique. We have demonstrated a sensitivity of 3.5 × 10(10) cm(-3) for neat NO(2) in a 1-m path at 640 nm and have estimated a sensitivity for ambient operation of 5 ppbv m (l0 ppbv m at 670 nm), where ppbvm is parts in 10(9) by volume per meter of absorption path length, from measured pressure-broadening coefficients.     

Ammonia detection and monitoring with photofragmentation fluorescence

Excimer laser fragmentation-fluorescence spectroscopy is an effective detection strategy for NH(3) in combustion exhausts at atmospheric pressure and high temperatures. Two-photon photofragmentation of NH(3) with 193-nm light yields emission from the NH(A-X) band at 336 nm. There are no major interferences in this spectral region, and the sensitivity is at the parts per billion (ppb) level. Quenching of the NH(A) state radical by the major combustion products is measured and does not limit the applicability of the detection method. Detection limits in practical situations are of the order of 100 ppb for a 100-shot (1-s) average. This technique could prove useful in monitoring ammonia emissions from catalytic and noncatalytic NO(x) reduction processes involving ammonia injection.     

The determination of iridium in photographic emulsions by flow injection micro-emulsion sampling inductively coupled plasma mass spectrometry

Abstract

Flow injection micro-emulsion sampling inductively coupled plasma mass spectrometry (FI-MES-ICP-MS) was used for the determination of iridium in in-house made emulsion reference materials. The sample was stabilized by a surfactant (Triton X-100) to ensure homogeneous sampling and to prevent sedimentation. A commercially available flow injection analysis system (FIAS) was modified and easily connected to the inductively coupled plasma mass spectrometer (ICP-MS) after optimization of conditions (instrument, flow injection, concentration of surfactant, etc.). The final result is a quantitative determination of iridium in photographic emulsions with a determination limit of 0.07 μg/kg and an accuracy of 3 per cent relative standard deviations (RSD) and a precision of ±0.2 μg/kg (n = 3). The precision and accuracy of the results obtained show the applicability of this method to the determination of iridium at ultratrace levels in various photographic emulsions.