Aplikace

Research laboratories must expand their capabilities to routinely analyze candidate microplastics from environmental samples to determine their origin and help predict biological impacts. Spectroscopic techniques are well suited to polymer identification. Laboratory Raman spectroscopy is an alternative to confocal Raman microscopes and Fourier transform infrared (FTIR) microscopes for quick identification of polymer materials. Raman microscopy was used to identify very small microplastic particles in this Application Note.

The coupling of highly efficient ion chromatography (IC) to multi-dimensional detectors such as a mass spectrometer (MS) or an inductively coupled plasma mass spectrometer (ICP/MS) significantly increases sensitivity while simultaneously reducing possible matrix interference to the absolute minimum. By means of IC/MS several oxyhalides such as bromate and perchlorate can be detected in the sub-ppb range. Additionally, organic acids can be precisely quantified through mass-based determination even in the presence of high salt matrices. By means of IC-ICP/MS different valence states of the potentially hazardous chromium, arsenic and selenium in the form of inorganic and organic species can be sensitively and unambiguously identified in one single run.

The analytical challenge treated in the present work consists in detecting trace concentrations (ppb) of bromide in the presence of a strong chloride matrix. This problem was overcome by separating the bromide ions from the main fraction of the early eluting chloride matrix (several g/L) by applying two sequential chromatographic separations on the same column. After the first separation, the main fraction of the interfering chloride matrix is flushed to waste, while the later eluting anions are diverted to an anion-retaining preconcentration column. After elution in counter flow, the bromide ions are efficiently separated from the marginal chloride residues. The four-point calibration curves for bromide and sulfate are linear in the range of 10…100 µg/L and 200…800 µg/L and yield correlation coefficients of 0.99988 and 0.99953 respectively. For the method shown here, a second injection valve and a preconcentration column are the only additional devices needed to master this demanding separation problem.

In modern days, a new breed of energetic (explosive) materials is emerging. Traditional aromatic nitrates are still in use, but there is dire need of analytical techniques for energetic materials in the chemical class of peroxides, azo etc. This presentation will demonstrate the use of a modern HPLC system with traditional detector (DAD) and also coupled with mass spectrometry for the analysis of abovementioned various classes of energetic materials.

This poster describes a simple and sensitive method for the determination of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) in water samples by suppressed conductivity detection. Separation was achieved by isocratic elution on a reversed-phase column thermostated at 35 °C using an aqueous mobile phase containing boric acid and acetonitrile. The PFOA and PFOS content in the water matrix was quantified by direct injection applying a 1000 μL loop. For the concentration range of 2 to 50 μg/mL and 10 to 250 μg/mL, the linear calibration curve for PFOA and PFOS yielded correlation coefficients (R) of 0.99990 and 0.9991, respectively. The relative standard deviations were smaller than 5.8%.The presence of high concentrations of mono and divalent anions such as chloride and sulfate has no significant influence on the determination of the perfluorinated alkyl substances (PFAS). In contrast, the presence of divalent cations, such as calcium and magnesium, which are normally present in water matrices, impairs PFOS recovery. This drawback was overcome by applying Metrohm`s Inline Cation Removal. While the interfering divalent cations are exchanged for non-interfering sodium cations, PFOA and PFOS are directly transferred to the sample loop. After inline cation removal, PFAS recovery in water samples containing 350 mg/mL of Ca2+ and Mg2+ improved from 90…115% to 93…107%.While PFAS determination of low salt-containing water samples is best performed by straightforward direct-injection IC, water rich in alkaline-earth metals are best analyzed using Metrohm`s Inline Cation Removal.

Because of its toxicity, the World Health Organization recommends a maximum arsenic content in drinking water of 10 μg/L. Anodic stripping voltammetry with the scTRACE Gold offers a straightforward, highly affordable alternative to spectroscopic determination.

Ion chromatography tackles difficult separation problems of various ionic species and typically works with conductivity detection. Mass detection as a secondary independent detector significantly lowers the detection limits and confirms the identity of analytes even when coeluting. This poster describes how the combination of IC-MS and automated sample preparation techniques cope with the analysis of anions and oxoanions in challenging matrices such as soil or explosion residues.

This poster demonstrates the feasibility of coupling a Metrohm IC system to a PerkinElmer NexION ICP-MS, operated under Empower 3 Software.Using a Metrosep Carb 2 column, the chromatographic separation of both species was achieved with a high resolution. Low background and high sensitivity allow determination in the low ng/L range.Optimal separation and full complexation of Cr(III) is already possible with EDTA concentrations from 40 μmol/L in low matrix solutions and may need to be increased depending on the sample matrix.Handling of the system was easy and user friendly. It was shown that speciation of Cr(III) and Cr(VI) can be carried out on this system utilizing a professional data system for acquisition, processing, and reporting.

If chloride and bromide are present in approximately equal molar concentrations they can be titrated directly with silver nitrate solution after addition of barium acetate. If, however, the molar ratio n(Br-) : n(Cl-) changes from 1 : 1 to 1 : 5, 1 : 10, 5 : 1 or 10 : 1 then greater relative errors must be expected with this method. The Bulletin describes an additional titration method that allows bromide to be determined in the presence of a large excess of chloride. The determination of small chloride concentrations in the presence of a large excess of bromide is not possible by titration.

The determination of cyanide is very important not only in electroplating baths and when decontaminating wastewater but, due to its high toxicity, also in water samples in general. Concentrations of 0.05 mg/L CN- can already be lethal for fish.This Bulletin describes the determination of cyanide in samples of different concentrations by potentiometric titration.Chemical reactions:2 CN- + Ag+ → [Ag(CN)2]-[Ag(CN)2]- + Ag+ → 2 AgCN

The potentiometric titration of Kjeldahl nitrogen is one of the most common analytic procedures. It is referenced in numerous standards, ranging from the food and animal feed industries through sewage and waste analysis and all the way to the fertilizer industry. As a rule, the samples are digested with concentrated sulfuric acid with the addition of a catalyst. The ammonium sulfate that is formed is distilled as ammonia in alkali solution, collected in an absorption solution and titrated there.This Bulletin provides a detailed description of potentiometric nitrogen determination following distillation of the digestion solution, followed by a discussion of the possibilities of coulometric titration (without distillation).

The quantitative determination of the alkaloid nicotine, which is an essential constituent of the tobacco plant, can be carried out by polarography. The quantification limit is less than 0.1 mg/L in the polarographic vessel.

The photometric determination of nitrate is limited by the fact that the respective methods (salicylic acid, brucine, 2,6-dimethyl phenol, Nesslers reagent after reduction of nitrate to ammonium) are subject to interferences. The direct potentiometric determination using an ion-selective nitrate electrode causes problems in the presence of fairly large amounts of chloride or organic compounds with carboxyl groups. The polarographic method, on the other hand, is not only more rapid, but also practically insensitive to chemical interference, thus ensuring more accurate results. The limit of quantification depends on the matrix of the sample and is approximately 1 mg/L.

This Application Bulletin describes the voltammetric determination of the elements antimony, bismuth, and copper. The limit of detection for the three elements is 0.5 ... 1 µg/L.

According to the described method, NTA and EDTA can be determined in mass concentrations of 0.05 mg/L up to 25 mg/L in polluted water and wastewater.At first NTA and EDTA are converted to the corresponding Bi complexes by addition of Bi3+ ions at a pH value of 2.0. As these Bi complexes have significantly different peak potentials, they can be determined simultaneously by DP polarography. The interfering anions nitrite, sulfite, and sulfide are removed from the sample by acidification and purging. Interfering cations are removed by cation exchange; any NTA or EDTA heavy metal complexes present in the sample are disintegrated during this procedure. To remove surfactants and other organic components interfering with the analysis, the sample solution is run through a column filled with non-polar adsorber resin.

This document explains how to measure Na ion concentration in diverse matrices with a sodium ion-selective electrode (Na-ISE) using direct measurement and standard addition.

This Application Bulletin describes the determination of mercury by anodic stripping voltammetry (ASV) at the rotating gold electrode. With a deposition time of 90 s, the calibration curve is linear from 0.4 to 15 μg/L; the limit of quantification is 0.4 μg/L.The method has primarily been drawn up for investigating water samples. After appropriate digestion, the determination of mercury is possible even in samples with a high load of organic substances (wastewater, food and semi-luxuries, biological fluids, pharmaceuticals).

This bulletin contains two parts. The first part gives a short theoretical overview while more details are offered in the Metrohm Monograph Conductometry. The second, practice-oriented part deals with the following subjects:Conductivity measurements in general; Determination of the cell constant; Determination of the temperature coefficient; Conductivity measurement in water samples; TDS – Total Dissolved Solids; Conductometric titrations;

This Application Bulletin describes a polarographic method for the determination of cyanide that allows to determine free cyanide fast and accurately. The determination also succeeds in solutions containing sulfides, where other methods fail. Cyanide concentrations in the range b(CN–) = 0.01...10 mg/L cause no problems. Interference caused by anions and complexed cyanides has been investigated.

Cadmium, lead, and copper can be determined simultaneously in oxalate buffer by anodic stripping voltammetry (ASV) after digestion with sulfuric acid and hydrogen peroxide. Tin present in the sample does not interfere with the determination of lead.For the voltammetric determination of tin please refer to Application Bulletin no. 176.

Cu2+, Co2+, Ni2+, Zn2+, and Fe2+/Fe3+ are determined simultaneously. Interference due to the presence of other metals is mentioned, and methods given to eliminate it. The threshold of determination is ρ = 20 µg/L for Co and Ni, and ρ = 50 µg/L each for Cu, Zn, and Fe.

This Application Bulletin describes methods for the polarographic and voltammetric determination of small quantities of chromium in water, effluent water and biological samples. Methods for the sample preparation for various matrices are given.

In the past, selenium determinations have always been either unreliable or have required complicated methods. However, as selenium is on the one hand an essential trace element (vegetable and animal tissues contain about 10 μg/kg), while on the other hand it is very toxic (threshold value 0.1 mg/m3), it is very important to cover determinations in the micro range. Cathodic stripping voltammetry (CSV) enables selenium to be determined in mass concentrations down to ρ(Se(IV)) = 0.3 μg/L.

Bromide is removed from the sample as BrCN by distillation. The BrCN is absorbed in sodium hydroxide solution and decomposed with concentrated sulfuric acid, then the released bromide ions are determined by potentiometric titration with silver nitrate solution. Iodide does not interfere with the determination.Iodide is oxidized to iodate by hypobromite. After destruction of the excess hypobromite, the potentiometric titration (of the iodine released from iodate) is carried out with sodium thiosulfate solution. Bromide does not interfere, even in great excess.The described methods allow the determination of bromide and iodide in the presence of a large excess of chloride (e.g., in brine, seawater, sodium chloride, etc.).

It has been known for years that consuming too much nitrates from foodstuffs can result in cyanosis, particularly for small children and susceptible adults. According to the WHO standard, the hazard level lies at a mass concentration c(NO3-) ≥ 50 mg/L. However, more recent studies have shown that when nitrate concentrations in the human body are too high, they can (via nitrite) result in the formation of carcinogenic and even more hazardous nitrosamines.Known photometric methods for the determination of the nitrate anion are time-consuming and prone to a wide range of interferences. With nitrate analysis continually increasing in importance, the demand for a selective, rapid, and relatively accurate method has also increased. Such a method is described in this Application Bulletin. The Appendix contains a cselection of application examples where nitrate concentrations have been determined in water samples, soil extracts, fertilizers, vegetables, and beverages.

"A sensitive methods to determine manganese is described. It is primarily suitable for the investigation of ground, drinking and surface waters, in which the concentration of manganese is important. The method can naturally also be used for trace analysis in other matrices.Manganese is determined in an alkaline borate buffer by the anodic stripping voltammetry (ASV). Interference by intermetallic compounds is prevented by the addition of zinc ions in the sample. The limit of determination lies at b(Mn) = 2 µg/L."

This bulletin describes the determination of calcium, magnesium, and alkalinity in water by complexometric titration with EDTA as titrant. It is grouped into two parts, the potentiometric determination and the photometric determination.There are multiple definitions of the different types of water hardness. In this Application Bulletin, the following definitions are used: alkalinity, calcium hardness, magnesium hardness, total hardness, and permanent hardness. Explanations of these definitions and other expressions are provided in the Appendix.Determination of alkalinity during the photometric part is carried out in a separate acid-base titration before the complexometric titration of calcium and magnesium in water. Permanent hardness can be calculated from these values. The determination of calcium and magnesium in beverages (fruit and vegetable juices, wine) is also described.The photometric part includes the determinations of total and calcium hardness and thereby indirectly magnesium hardness using Eriochrome Black T and calconcarboxylic acid as indicators (in accordance with DIN 38406-3).

After acid digestion, the sample solution is neutralized with sodium hydroxide to form sodium dihydrogen phosphate. An excess of lanthanum nitrate is added and the released nitric acid is then titrated with sodium hydroxide solution.NaH2PO4 + La(NO3)3 → LaPO4 + 2 HNO3 + NaNO3This determination method is suitable for higher phosphate concentrations.

Although the known photometric methods for the determination of ammonia/ammonium are accurate, they require a considerable amount of time (Nessler method 30 min, indophenol method 90 min reaction time). A further disadvantage of these methods is that only clear solutions can be measured. Opaque solutions must first be clarified by time-consuming procedures. These problems do not exist with the ion-selective ammonia electrode. Measurements can be easily performed in waste water, liquid fertilizer, and urine as well as in soil extracts. Especially for fresh water and waste water samples several standards, such as ISO 6778, EPA 350.2, EPA 305.3 and ASTM D1426, describe the analysis of ammonium by ion measurement. In this Application Bulletin, the determination according to these standards is described besides the determination of other samples as well as some general tips and tricks on how to handle the ammonia ion selective electrode. Determination of ammonia in ammonium salts, of the nitric acid content in nitrates, and of the nitrogen content of organic compounds with the ion-selective ammonia electrode is based on the principle that the ammonium ion is released as ammonia gas upon addition of excess caustic soda:NH4+ + OH- = NH3 + H2OThe outer membrane of the electrode allows the ammonia to diffuse through. The change in the pH value of the inner electrolyte solution is monitored by a combined glass electrode. If the substance to be measured is not present in the form of an ammonium salt, it must first be converted into one. Organic nitrogen compounds, especially amino compounds are digested according to Kjeldahl by heating with concentrated sulfuric acid. The carbon is oxidized to carbon dioxide in the process while the organic nitrogen is transformed quantitatively into ammonium sulfate.

Potassium is one of the most common elements and can be found in many different minerals and other potassium compounds. It is of importance for humans, animals and plants as it is an essential mineral nutrient and involved in many cellular functions like cell metabolism and cell growth. For these reasons, it is important to be able to declare the potassium content of food or soil to reduce problems that may arise by a potassium deficiency or extensive consumption.This bulletin describes an alternative to flame photometric method using an ion selective electrode and direct measurement or standard addition technique. Several potassium determinations in different matrices using the combined potassium ion-selective electrode (ISE) are presented here. Additionally, general hints, tips and tricks for best measurement practice are given.

"Molybdenum is an essential trace element for plant growth. Since it occurs in natural waters only in trace amount, a very sensitive method of determination is needed. Using the following polarographic method, it is possible to determine 5·10-10 mol/L resp. 50 ng/L.The principle of the method is based on the reaction between the molybdate ion MoO42- and the complexing agent 8-hydroxy-7-iodo-quinoline-5-sulfonic acid (H2L) to form a MoO2L22- complex, which is adsorbed on the mercury electrode. The adsorbed Mo(VI) is reduced electrochemically to the Mo(V) complex. The hydrogen ions present in the solution oxidize Mo(V) again spontaneously to form the Mo(VI) complex, which is thus newly available for electrochemical reduction. This catalytic reaction is the reason for the high sensitivity of the method.Tungsten W(VI) exhibits practically the same electrochemical behavior as molybdenum, but is not described in detail in this Application Bulletin."

In most electrolytes the peak potentials of lead and tin are so close together, that a voltammetric determination is impossible. Difficulties occur especially if one of the metals is present in excess.Method 1 describes the determination of Pb and Sn. Anodic stripping voltammetry (ASV) is used under addition of cetyltrimethylammonium bromide. This method is used when:• one is mainly interested in Pb• Pb is in excess• Sn/Pb ratio is not higher than 200:1According to method 1, Sn and Pb can be determined simultaneously if the difference in the concentrations is not too high and Cd is absent.Method 2 is applied when traces of Sn and Pb are found or interfering TI and/or Cd ions are present. This method also uses DPASV in an oxalate buffer with methylene blue addition.

The determination of the physical and chemical parameters as electrical conductivity, pH value, p and m value (alkalinity), chloride content, the calcium and magnesium hardness, the total hardness, as well as fluoride content are necessary for evaluating the water quality. This bulletin describes how to determine the above mentioned parameters in a single analytical run.Further important parameters in water analysis are the permanganate index (PMI) and the chemical oxygen deman (COD). Therefore, this Bulletin additionally describes the fully automated determination of the PMI according to EN ISO 8467 as well as the determination of the COD according to DIN 38409-44.

This Bulletin describes the voltammetric determination of aluminum in water samples down to a concentration of 1 μg/L. An aluminum complex is formed with alizarin red S (DASA) and enriched at the HMDE. The following determination employs differential pulse adsorptive stripping voltammetry (DP-AdSV). Disturbing Zn ions are eliminated by addition of CaEDTA.

This Bulletin, using practical examples, indicates how the user can achieve optimum pH measurements. As this Bulletin is intended for actual practice, the fundamentals - which can be found in numerous books and publications - are treated only briefly.

Sulfide and sulfite can be determined polarographically without any problems. For sulfide, polarography is performed in an alkaline solution, for sulfite in a slightly acidic primary solution. The method is suitable for the analysis of pharmaceuticals (infusion solutions), wastewater/flue gas water, photographic solutions, etc.

This Application Bulletin describes the stripping analysis of Ag at the rotating disk electrode (RDE) with glassy carbon tip (GC) or Ultra Trace graphite tip. In routine operation, the determination limit lies at approx. 10 μg/L Ag, with careful work 5 μg/L Ag can be obtained. After appropriate digestion, silver determination is also possible with samples containing a relatively high proportion of organic substances (e.g. wine, foodstuffs etc.). The method has been developed primarily for water samples (well, ground and wastewater, desilvering solutions of the photographic industry).

This Application Bulletin describes …

This Bulletin gives a survey of standard methods from the field of water analysis. You will also find the analytical instruments required for the respective determinations and references to the corresponding Metrohm Application Bulletins and Application Notes. The following parameters are dealt with: electrical conductivity, pH value, fluoride, ammonium and Kjeldahl nitrogen, anions and cations by means of ion chromatography, heavy metals by means of voltammetry, chemical oxygen demand (COD), water hardness, free chlorine as well as a few other water constituents.

This Bulletin describes the determination of arsenic by anodic stripping voltammetry (ASV) at the rotating gold electrode. A determination limit of 0.5 μg/L can be achieved with 10 mL sample solution. A differentiation between the As(III) concentration and the total arsenic concentration can be made by appropriate selection of the deposition potential. The analyses are performed with a special gold electrode whose active surface is located laterally; c(HCl) = 5 mol/L is used as supporting electrolyte. For the determination of the total arsenic content, As(III) and As(V) are reduced at -1200 mV by nascent hydrogen to As0, which is preconcentrated on the electrode surface. If the deposition is carried out at -200 mV then only As(III) is reduced; this allows the differentiation between total arsenic and As(III). During the subsequent voltammetric determination the preconcentrated As0 is again oxidized to As(III).

The standard method postulated by DIN 38406 Part 16 describes the determination of Zn, Cd, Pb, Cu, Tl, Ni, and Co in drinking, ground, surface and precipitation (e.g. rain) water. Because the presence of organic substances in the water samples can strongly interfere with the voltammetric determination, a pretreatment with UV digestion using hydrogen peroxide is necessary. This digestion ensures the elimination of all organic substances without introduction of blank values. These methods can, of course, also be applied for trace analysis in other materials, e.g. trace analysis in the production of semiconductor chips based on silicon. Zn, Cd, Pb, Cu, and Tl are determined on the HMDE by means of anodic stripping voltammetry (ASV), Ni and Co by means of adsorptive stripping voltammetry (AdSV).

This Application Bulletin describes the determination of cadmium and lead at a mercury film electrode (MFE) by anodic stripping voltammetry (ASV). The mercury film is plated ex situ on a glassy carbon electrode and can be used for up to one day. With a deposition time of 30 s, the limit of detection is ß(Cd2+) = 0.02 µg/L and ß(Pb2+) = 0.05 µg/L. The linear working range for both elements goes up to approx. 50 μg/L using the same deposition time.

The method described allows the determination of W(VI) traces in the range 0.2 to 50 µg/L (ppb). Traces of organic compounds present in the samples (e.g. natural waters) interfere. They have to be removed by UV digestion (e.g. 705 UV Digester). Interference by Fe(III) up to a concentration of 100 mg/L is eliminated by reduction to Fe(lI) with ascorbic acid. If the amount of Cu(II) in the sample exceeds the amount of W(VI) by a factor of 200 or more, the Cu ions have to be bound with thiourea. Moreover, the concentration of Cu(II) should not exceed 5 mg/L. The determination is made by adsorptive stripping analysis in the DP mode.

The method describes the determination of Cr traces in a range between 1 ... 250 μg/L. The method is based on the adsorption of a Cr(lll)-diphenylcarbazonate complex on the Ultra Trace graphite rotating disk electrode (RDE). Organic compounds present in samples (e.g. natural waters) have a strong interfering effect. So they have to be removed by e.g. UV digestion. The determination is made by adsorptive stripping voltammetry in the DC (direct current) measuring mode. Purging with nitrogen is not necessary. The determinations work well also in high salt concentration solutions.

Chlorine is frequently added to drinking water for disinfection. Depending on the reactivity and the concentration of chlorine, toxic disinfection by-products (DBPs) can thereby be released. Therefore, it is necessary to strictly control the chlorine concentration in the drinking water. This Application Bulletin shows how to determine the chlorine concentration according to three standard methods: DIN EN ISO 7939-1, APHA 4500-Cl Method B, and APHA 4500-Cl Method I.

This Application Bulletin describes the determination of zinc at a mercury film electrode (MFE). Zinc can also be determined simultaneously with cadmium and lead. The determination of copper at the MFE is not possible. The mercury film is plated ex-situ on a glassy carbon electrode and can be used for half a day up to one day.Zinc can be determined at the mercury film electrode by anodic stripping voltammetry (ASV). The presence of copper, which is naturally present in many samples, affects the determination of zinc due to the formation of an intermetallic compound. As a result the determined concentrations of zinc are too low. The addition of gallium can eliminate the interference to a certain extent since the intermetallic complex of gallium and copper is more stable than the complex of zinc and copper.With a deposition time of 10 s, the limit of detection is β(Zn2+) = 0.15 μg/L. The linear working range goes up to approx. 300 μg/L.With the deposition time of 10 s the method is suitable for samples between 10 μg/L and 150 μg/L Zn content. For samples with lower concentrations the results are more reliable if the deposition time is increased to e.g. 30 s. Samples with higher concentrations have to be diluted.

This Application Bulletin describes the determination of titanium by adsorptive stripping voltammetry (AdSV) using mandelic acid as complexing agent. The method is suitable for the analysis of ground, drinking, sea, surface and cooling waters, in which the concentration of titanium is of importance. The methods can, of course, also be used for the trace analysis in other matrices.The limit of detection is approx. 0.5 µg/L.

This Application Bulletin describes two methods for the determination of iron at the Multi Mode Electrode.Method 1, the polarographic determination at the DME, is recommended for concentrations of β(Fe) > 200 μg/L. For this method the linear range is up to β(Fe) = 800 μg/L.For concentrations < 200 μg/LMethod 2, the voltammetric determination at the HMDE, is to be preferred. The detection limit for this method is β(Fe) = 2 μg/L, the limit of quantification is β(Fe) = 6 μg/L. The sensitivity of the method cannot be increased by deposition.Iron(II) and iron(III) have the same sensitivity for both methods.These methods have been elaborated for the determination of iron in water samples. For water samples with high calcium and magnesium concentrations such as, for example, seawater, a slightly modified electrolyte is used in order to prevent precipitation of the corresponding metal hydroxides. The methods can also be used for samples with organic loading (wastewater, beverages, biological fluids, pharmaceutical or crude oil products) after appropriate digestion.

This Application Bulletin describes the determination of arsenic in water samples by anodic stripping voltammetry using the scTRACE Gold sensor. This method makes it possible to distinguish between As(total) and As(III). With a deposition time of 60 s, the limit of detection for As(total) is 0.9 µg/L, for As(III) it is 0.3 µg/L.

This Application Bulletin describes the determination of inorganic mercury in water samples by anodic stripping voltammetry using the scTRACE Gold sensor. With a deposition time of 90 s, calibration is linear up to a concentration of 30 µg/L; the limit of detection lies at 0.5 µg/L.