Sample Uptake Research Articles

Polyurethane foam (PUF) disks passive air samplers: Wind effect on sampling rates

Different passive sampler housings were evaluated for their wind dampening ability and how this might translate to variability in sampler uptake rates. Polyurethane foam (PUF) disk samplers were used as the sampling medium and were exposed to a PCB-contaminated atmosphere in a wind tunnel. The effect of outside wind speed on PUF disk sampling rates was evaluated by exposing polyurethane foam (PUF) disks to a PCB-contaminated air stream in a wind tunnel over air velocities in the range 0 to 1.75 m s −1. PUF disk sampling rates increased gradually over the range 0–0.9 m s −1 at ∼4.5–14.6 m 3 d −1 and then increased sharply to ∼42 m 3 d −1 at ∼1.75 m s −1 (sum of PCBs). The results indicate that for most field deployments the conventional ‘flying saucer’ housing adequately dampens the wind effect and will yield approximately time-weighted air concentrations.

Introduction of organic solvent solutions into inductively coupled plasma-atomic emission spectrometry using a microwave assisted sample introduction system

A microwave assisted sample introduction system based on the use of a TM010 cavity (MWDS2) has been employed for the introduction of 10% w/w organic solvent solutions in inductively coupled plasma atomic emission spectrometry (ICP-AES). Ethanol, propan-2-ol, formic and acetic acids have been used. Firstly, the effect of the incident microwave power and the sample uptake rate on the emission signal was evaluated. For all matrices tested, the higher emission signals were obtained when operating at the highest microwave power (i.e., 290 W) and sample uptake rate (400 μL min−1). Results with the MWDS2 were compared with those afforded by a desolvation system based on the use of a domestic microwave oven (MWDS) and by a conventional sample introduction system (CS). The MWDS2 provides the highest emission signals (up to 7 and 17 times higher than those with the MWDS and the CS, respectively). As regards the matrix effects originated by the organic solutions, results demonstrate that the use of a microwave-based sample introduction system, mainly the MWDS2, affords a noticeable reduction in the matrix effects originated by the use of organic solvent solutions in ICP-AES with a conventional sample introduction system. This behaviour can be explained by taking into account the solution transport rates afforded by the different sample introduction systems. For all the analytical lines and matrices tested and operating at 400 μL min−1, the MWDS2 gives rise to signal values that are, on average, 1.2 ± 0.2 times the signal obtained with water. For the MWDS and the CS, this factor takes values of 1.6 ± 0.2 and 2.0 ± 0.5, respectively. Transient matrix effects have been observed operating with the MWDS2 when switching between water and an organic matrix solution. These transient effects result in a drift time about 4.5 times higher than those with a CS.

Development of a Nebulizer for a Sheathless Interfacing of NanoHPLC and ICPMS

A novel nebulizer (nDS-200) working at sample uptake rates of less than 500 nL min(-1) was developed for a sheathless interfacing of nanoHPLC (75-microm column i.d.) with ICPMS. It was based on a hollow fused-silica needle of which the tip (i.d. 10 microm, o.d. 20 microm) centered in a 254-microm-i.d. sapphire orifice. The nebulizer, equipped with a 3-cm(3) drain-free vaporization chamber, enabled a stable introduction into an ICP of aqueous mobile phases containing up to 95% acetonitrile at eluent flow rates between 50 and 450 nL min(-1). The low dead volume of the interface resulted in a peak width of 1.3 s (at half-height) and the entirely preserved chromatographic resolution. An example application of the coupling to the analysis of a tryptic digest of a SIP18 protein containing two to nine selenomethionine residues was described. The absolute detection limit was 25 fg (80Se), which allowed the detection of low-abundant selenopeptides at the femtomole level. In contrast to electrospray MS, the ICPMS detection in nanoHPLC is unaffected by the coeluting matrix and concomitant compounds and offers an elegant method for the detection and quantification of minor heteroelement-containing species prior to or in parallel with ESI MS analysis.

Passive Air Sampling of Polychlorinated Biphenyls, Organochlorine Compounds, and Polybrominated Diphenyl Ethers Across Asia

Asia is of global importance economically, yet data on ambient persistent organic pollutant levels are still sparse for the region, despite international efforts under the Stockholm Convention to identify and reduce emissions. A large-scale passive air sampling survey was therefore conducted in Asia, specifically in China, Japan, South Korea, and Singapore. Polyurethane foam disks were deployed simultaneously at 77 sites, between Sept 21 and Nov 16, 2004, and analyzed for polychlorinated biphenyls (PCBs), organochlorine compounds (hexachlorobenzene (HCB), dichlorodiphenyltrichloroethanes (DDTs), chlordane), and polybrominated diphenyl ethers (PBDEs). The meteorological conditions prevailing in the region at this time facilitated the assessment of local/regional differences in atmospheric emissions, because large-scale advection effects due to monsoons or dust storms did not occur. Air concentrations estimated assuming an average sampler uptake rate of 3.5 m3/day ranged as follows (pg m(-3)): PCBs, 5-340; HCB, 10-460; DDTs, 0.4-1800; chlordanes, 1-660; PBDEs, < 0.13-340. South Korea and Singapore generally had regionally low concentrations. Elevated concentrations of PCBs, DDTs, and HCB occurred at sites in China, higher than reported in a similar recent sampling campaign in Europe. Chlordane was highest in samples from Japan (which also had elevated levels of PCBs and DDTs) and was also elevated in some Chinese locations. PBDE levels were generally low in the region.

A new laboratory test chamber for the determination of diffusive sampler uptake rates

Abstract Diffusive samplers are today widely used for air quality control in indoor and outdoor environments and for personal exposure studies as well. The uptake rate is a fundamental parameter of a sampler for the calculation of the concentration of the substance to be monitored depends directly on it. Uptake rates can be affected by numerous factors. Their values and the range of validity have to be determined in an appropriate exposure chamber. The laboratory test chamber presented here consists of a loop made of glass, stainless steel and PTFE containing the generated atmosphere in which diffusive samplers can be tested. It is possible to accommodate several samplers simultaneously and simulate various environmental conditions such as temperature, wind speed, wind direction, humidity, atmospheric composition, total pressure and exposure duration. All working parameters have to be monitored including the concentrations of the components of the generated atmosphere. It is shown that the expected concentration of a volatile compound like benzene can be reached very quickly whereas those of less volatile compounds like toluene or xylenes takes longer. The procedure for overcoming this difficulty is described in this paper. By means of an application it is also shown that exposure duration can unequally affect diffusive sampler uptake rates depending on sampler geometry and the nature of the adsorbent. It appears that a radial high-uptake rate diffusive sampler packed with a thermally desorbable material may be unsuitable for long-term monitoring of a volatile compound like benzene. However an axial low-uptake rate diffusive sampler, also packed with a thermally desorbable material, seems more appropriate for this application due to the higher stability of its uptake rate.

A microwave assisted desolvation system based on the use of a TM010 cavity for inductively coupled plasma based analytical techniques

A new microwave assisted desolvation system based on the use of a TM010 cavity (MWDS2) has been developed and evaluated in plasma based analytical techniques: inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). The new design overcomes the main experimental drawbacks shown by previous designs based on the use of domestic ovens: (i) lack of control on microwave generation and application; and (ii) inappropriate MW cavity characteristics. The evaluation has been performed in terms of the effect of the incident microwave power and the sample uptake rate and the results obtained has been compared with those afforded by a conventional sample introduction system (nebulizer and double pass spray chamber) and a desolvation system based on the use of a domestic microwave oven (MWDS). The new MWDS2 give rise to higher analytical signals and lower limits of detection and stabilization times (2–3 times) than those obtained with the MWDS in ICP-AES and ICP-MS.

The study of the selection of emission lines and plasma operating conditions for efficient internal standardization in inductively coupled plasma optical emission spectrometry

In inductively coupled plasma optical emission spectrometry matrix effects and drift are usually caused by two major factors, namely changes in the energy transfer between the plasma and sample, and changes in the efficiency of sample aerosol formation and transport. Mathematical model was developed for the behavior of the emission lines as the function of the sample uptake rate and the forward power. This model was utilized to study efficiency of internal standardization in non-robust, semi-robust and robust operating conditions. It was shown that in non-robust conditions internal standardization is extremely difficult, whereas in semi-robust and robust conditions it can be used efficiently. These results are in good agreement with those obtained by other authors previously. It was also shown that in general case using only single correction coefficient ‘perfect’ correction is impossible using traditional internal standardization. Model developed can be used to quantitatively evaluate the efficiency of internal standardization to reduce matrix effects and drift.

Evaluation of the simultaneous use of standard additions and internal standards calibration techniques for inductively coupled plasma mass spectrometry

The use of internal standards combined with standard additions calibration for inductively coupled plasma mass spectrometry (ICP-MS) is discussed. Yttrium, rhodium, magnesium, cobalt, copper, nickel, silver, thallium, molybdenum and lead were analyzed in solutions of known composition with a 500 mg ml−1 Na matrix. Additionally, the Mg, Co, Y, Rh and Pb signals were used as internal standards for the other elements in the same matrix. Severe drift effects were simulated by drastically altering the liquid sample uptake rate. The signals were used to compare the results obtained using four different calibration methods: external standards, standard additions, internal standards and standard additions in combination with an internal standard. The average errors for external standards varied from 23 to 41% while the average errors for internal standards ranged from 1 to 71%. The error for standard additions was 45%. The use of standard additions with an internal standard produced an average error of 0.7–5%, suggesting that this is a powerful calibration technique.

Preliminary characterization and fundamental properties of aerosols generated by a flow focusing pneumatic nebulizer

A new pneumatic concentric nebulizer (flow focusing pneumatic nebulizer, FFPN), based on the capillary flow focusing effect which produces highly controllable fine aerosols, is presented for the first time for analytical applications. The key aerosol diagnostic data and analytical figures of merit obtained using ICP-AES are presented for the FFPN and compared with a commercially available glass concentric nebulizer (conical nebulizer, CK). To perform a fair comparison, both nebulizers have been run under their own standard working conditions. Under all the conditions studied, the FFPN produces a finer primary aerosol than the conventional pneumatic nebulizer. At a solution uptake rate of 2.0 mL min−1 and a nebulizer gas flow rate of 1.0 L min−1 for the CK, and at a solution uptake rate of 0.2 mL min−1 and a nebulizer gas flow rate of 0.7 L min−1 for the FFPN, the median diameter (D50) values of the primary aerosol are 24.64 μm and 3.82 μm with the CK and FFPN, respectively. The tertiary aerosols of the CK and FFPN studied do not show a substantial difference, the D50 values, under the same operating conditions stated above, being 2.89 μm and 2.87 μm for the CK and FFPN, respectively. Under most of the studied conditions, all the primary aerosols produced by FFPN are contained on droplets smaller than 10 μm. For example, under the above experimental conditions, nearly 22% and 98% of primary aerosol volume is contained on droplets having sizes less than 10 μm for the CK and FFPN, respectively. However, approximately all the tertiary aerosol volume is contained on droplets smaller than this diameter with both nebulizers. This is the result of strong filtering action of the cyclonic spray chamber used, with a cut-off diameter of 15 μm, when CK is used. In general, sensitivities, precision and limits of detection with the FFPN are similar or better than those of the CK, yet with a sample uptake rate of only one-tenth the CK rate.

Characterization of microconcentric nebulizer uptake rates for capillary electrophoresis inductively coupled plasma mass spectrometry

There is demonstrated interest in combining capillary electrophoresis (CE) with inductively coupled plasma mass spectrometry (ICP-MS) for speciation determinations. When self-aspirating nebulizers are used for this application, it is important to offset the suction effect to avoid degradation of the separation. In this study, sample uptake rates for three microconcentric nebulizers of the same model, in combination with a cyclonic spray chamber, were characterized and compared for future utilization in CE–ICP-MS interfaces. The specific model studied was a MicroMist with a nominal uptake rate of 100 μl/min at 1 l/min argon gas flow rate per the manufacturer's specifications. Sample uptake rates at various nebulizer gas flows were measured by aspirating water from a weighed container and calculating the uptake rate in microliter per minute. The nebulizers studied provided good reproducibility from day to day, but a comparison of the different nebulizers reflected a significant difference in performance. A characteristic observed during the study was that uptake rates decreased with increasing nebulizer gas flow. This can be used for sample introduction for CE–ICP-MS. Interestingly, very different performance was observed when comparing the three different nebulizers of the same model. Uptake rates showed strong dependence on argon gas flow rates and the dimensions of the sample uptake tubing.

Determination of Fourteen Elements in Bone Samples Using Inductively Coupled Plasma (ICP) Analysis

Objective. There have been many studies of the concentrations of elements in blood and urine, but few studies have focused on the concentrations of elements in bone. The elements in bone play, important roles in a variety of physiological processes. The objective of this study was to assess the optimum conditions for measuring the concentrations of 14 elements in human bone samples. Methods. Seventy-seven bone samples were collected from bone surgery patients and pretreated using a microwave digest. Inductively couple plasma-atomic emission spectroscopy (ICP-AES) analysis was used to determine the optimal conditions for three variables: sample uptake rate, flow rate of Argon gas (Ar) into the nebulizer and concentrations of nitric acid. Results. The detection limit of elements ranged from 1μg/L (Co, Mn and Mg) to 55μg/L (Pb). The optimal sample uptake rate and the optimal flow rate of Ar into the nebulizer were found to be 1.33 m1/min and 0.351/min, respectively The optimum nitric acid concentration was 1M. Mn (0.7 μg/g) and Cd (1.2 μg/g) in bone samples were present in the lowest concentrations, and Ca (82007.9 μg/g) and Mg (3005.2 μg/g) had the highest concentrations. Except for Cu, there were no significant differences in element concentrations between males and females. There was a high variation in element concentrations among the bone samples. Conclusions. Further research is needed to investigate the factors that influence the concentrations of elements in bone. The optimal conditions for bone-element analysis using ICPAES as recommended by the authors was confirmed in this study.

A high-efficiency cross-flow micronebulizer for inductively coupled plasma mass spectrometry.

A pneumatically driven, high-efficiency cross-flow micronebulizer (HECFMN) is introduced for inductively coupled plasma (ICP) spectrometries. The HECFMN uses a smaller nozzle orifice for nebulizer gas (75 microm in diameter) and a replaceable and adjustable fused-silica capillary for sample uptake. The HECFMN is optimally operated over a wide range of sample uptake rate (5-120 microL/min) at a rf power of 1100 W and nebulizer gas flow rates of 0.8-1.0 L/min when a 50 microm i.d. by 150 microm o.d. capillary is used. The aerosol quality is qualitatively examined in a simple manner, and the transport efficiencies are determined by direct filter collection. Compared with conventional cross-flow nebulizers (CFNs), the HECFMN produces much smaller and more uniform droplets and thus provides much higher analyte transport efficiencies (generally 24-95%) at the sample uptake rates of 5-100 microL/min. Several analytical performance indexes are acquired using an Ar ICPMS system. The sensitivities and detection limits measured with the HECFMN at 50 microL/min sample uptake rate are comparable to or improved over those obtained with a conventional CFN consuming 1 mL/min sample, and the precisions with the HECFMN (typically 1.1-1.7% RSDs) are slightly better than those with the CFN (1.6-2.3% RSDs). The ratios of refractory oxide ion-to-singly charged ion (CeO+/Ce+) are typically in the range from 0.7 to 3.3% for the sample uptake rates of 5-100 microL/min. The free aspiration rate of the HECFMN is 8.9 microL/min for distilled deionized water at the nebulizer gas flow rate of 1.0 L/min without any effect of pressure. The features of the HECFMN suggest good potential for HECFMN use in interfacing ICPMS with capillary electrophoresis and microcolumn high-performance liquid chromatography.

Interfacing capillary electrophoresis with inductively coupled plasma mass spectrometry by direct injection nebulization for selenium speciation

A demountable direct injection high efficiency nebulizer operating at low sample uptake rates was developed and used for coupling of capillary electrophoresis (CE) with inductively coupled plasma mass spectrometry (ICP-MS). When the nebulizer was used for continuous sample introduction, detection limits of 20 and 1 ng L−1 were obtained for 82Se and 103Rh, respectively, at sample uptake rates of 10–30 μL min−1, based on three times the standard deviation of blank solution (3σb, n = 10). The nebulizer was used as part of the interface for coupling of CE with ICP-MS and applied for speciation of aqueous selenium standards. The interface was operated in the self-aspirating mode with a sheath liquid uptake of 10 μL min−1. The CE-ICP-MS system resulted in baseline separation of selenate, selenite, selenocystine and selenomethionine within a total analysis time of 5.4 min. Detection limits were in the sub µg Se L−1 range, corresponding to absolute detection limits in the range 25–125 fg selenium. Repeatability (n = 6) expressed as relative standard deviations with respect to migration times, peak heights and peak areas were better than 1.6, 6.7 and 6.0%, respectively.

Determining picogram quantities of uranium in urine by isotope dilution inductively coupled plasma mass spectrometry. Comparison with α-spectrometry

An accurate and simple method has been developed for the determination of uranium in urine using inductively coupled plasma mass spectrometry (ICP-MS). Isotope dilution analysis was applied using the long-lived uranium nuclide 233U as a spike in 1.3-fold diluted urine samples. To avoid matrix effects and salt depositions in the interface region of the instrument a prototype concentric-flow nebulizer with a mini cyclonic spray chamber was used at a reduced sample uptake rate of 0.3 ml min−1. The method was evaluated by comparison with α-spectrometry, as well as by analysis of National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 2670, Toxic Metals in Freeze Dried Urine, for which published results of isotope dilution thermal ionization mass spectrometry (TIMS) and radiochemical neutron activation analysis (RNAA) measurements are available. ICP-MS and α-spectrometry yielded consistent results (Wilcoxon, p = 0.87). The ICP-MS mean value (±95% confidence interval) of 143 ± 10 pg ml−1 obtained for the SRM 2670 agreed with the reported RNAA value of 130 ± 18 pg ml−1 at the 95% confidence interval; however, they exceeded the reported TIMS value of 113 ± 3 pg ml−1. The proposed method provides a means for determining uranium in unexposed subjects as well as in those considered to be exposed. Potential exposure to uranium amongst employees of UNHCR in western Kosovo was assessed.

Preliminary study on a vapor generation technique for nickel without using carbon monoxide by inductively coupled plasma atomic emission spectrometry

The authors found that volatile nickel species could be generated by reaction in an aqueous solution with sodium or potassium borohydride under appropriate conditions at room temperature without using carbon monoxide. After vapor generation and gas–liquid separation, the volatile species was carried into an inductively coupled plasma (ICP) by argon gas, and the quantity of nickel determined by atomic emission spectrometry. The intensities of the Ni lines were strongly affected by the acidity of samples, the flow rate of argon carrier gas and the length of the transfer tube between the gas–liquid separator and ICP. A detection limit of 0.5 ng/ml and a precision of <5% was obtained under the following conditions: 0.12 M HCl acidified sample solution; 3% potassium borohydride solution with 0.5% potassium hydroxide added; sample uptake rate 2.8 ml/min; argon carrier gas flow 500 ml/min; and the length of the transfer tube kept as short as possible.

A multimicrospray nebulizer for microwave-induced plasma mass spectrometry

We have developed a nebulizer, called a multimicrospray nebulizer (MMSN), that efficiently introduces analytes for plasma mass spectrometry and plasma emission spectrometry. In this nebulizer, both the sample solution and the nebulizer gas are divided into several streams to produce a multispray. That is, the MMSN is a nebulizer that contains several micronebulization units, each unit including an orifice for passing the nebulizer gas and a capillary for introducing a sample solution. The microspray from each micronebulization unit can be operated at a microliter per minute sample uptake rate to achieve high nebulization efficiency. The multimicrospray nebulizer is capable of introducing more analyte to the plasma compared with a single-orifice micronebulizer, which has a very low sample uptake rate. In this work, an MMSN with three orifices was found to be suitable for microwave-induced plasma mass spectrometry (MIP-MS). The sample uptake rate can be varied within a range of 5-250 microL/min. Therefore, the nebulizer is unique in its ability to deal with various sample volumes and provide high nebulization efficiency. The sensitivity for all elements obtained with the MMSN was higher than that obtained with a conventional concentric nebulizer (CCN), which is difficult to achieve with other types of microintroduction nebulizers. For most elements, the MIP-MS sensitivity was improved about 2-fold at a sample uptake rate of 150 microL/min, a much lower rate than that for the CCN (usually 0.5-1.5 mL/min). The sensitivity for arsenic was improved by a factor of 5. The relative standard deviation was found to be less than 2.0%.

A low-powered microwave thermospray nebulizer for inductively coupled plasma atomic emission spectrometry

A novel microwave thermospray nebulizer (MWTN), using a TM010 resonant cavity as the energy coupling device, is described in this paper. The nebulizer consists of a knotted PTFE capillary (od, 1.3 mm, id, 0.5 mm) and a thinner quartz outlet capillary located in a TM010 cavity. A microwave power of 60 W is enough to nebulize the sample solution. Because of the big diameter of the PTFE capillary, a peristaltic pump, instead of the necessary high-pressure pump in a traditional thermospray nebulizer, could be used to transfer the solution. The nebulizer was successfully coupled to an inductively coupled plasma atomic emission spectrometry (ICP-AES) instrument. The effect of various parameters, such as the nature and concentration of the medium, carrier gas flow rate, sample uptake rate and so on, on the emission intensity of Fe, Mg, V and Cu was studied. Compared with a pneumatic nebulizer, the detection limits for Cu, Fe, Mg, and V were improved by a factor of 2–4.

Double membrane desolvator for direct analysis of isopropyl alcohol in inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS)

A double membrane desolvator (DMD) with an MCN was built and tested for the analysis of isopropyl alcohol using ICP-AES and ICP-MS. Unlike a conventional membrane desolvator, two different concentric membrane tubes were used for the DMD. Additionally, the length of the membrane was reduced in half and the total area was increased. Influence of sweep gas flow on analyte intensities in ICP-AES was studied. Approximately 70–90% of C(I) signal was reduced by using the DMD and this reduction was the largest among the emission lines measured, for example Cr(II), Ca(II), and Mn(II) showed the reduction in the range of 30–50%. The use of DMD also reduced the background level, and heating the spray chamber enhanced the signal intensity of Cr(II) significantly in ICP-AES. For ICP-MS, the reduction of molecular interference was demonstrated when MCN-DMD was used. The ratio of CeO +/Ce + was approximately 0.16 at the sample uptake rate of 210 μl/min and it was reduced by a factor of 3 for 110 μl/min.

Desolvation of acid solutions in inductively coupled plasma atomic emission spectrometry by infrared radiation. Comparison with a system based on microwave radiation

The behaviour of an infrared desolvation system with acid solutions in inductively coupled plasma atomic emission spectrometry (ICP-AES) is evaluated, and the influence of the liquid uptake rate and of the nature and concentration of the acid on the solvent and analyte transport rates and on the analytical figures of merit is studied. The results are compared with those obtained with a desolvation system based on the absorption of microwave radiation. The infrared desolvation system performs best at low sample uptake rates (0.4 ml min −1) and its behaviour strongly depends on the nature and concentration of the solution used. With nitric and hydrochloric solutions, there is almost no effect of the acid concentration on the emission intensity, while for sulfuric and perchloric acids the signal decreases as the acid concentration is increased. These effects seem to be related with the different capability of the acid aerosols to be heated in an IR field. The microwave desolvation system seems to be more prone to matrix (acid) effects, specially when using sulfuric and perchloric acids, resulting in emission intensities which are usually lower than those obtained with the infrared desolvation system, though their limits of detection are quite similar.

Microwave desolvation for acid sample introduction in inductively coupled plasma atomic emission spectrometry

This study deals with the behaviour of a microwave desolvation system (MWDS) with acid solutions in inductively coupled plasma atomic emission spectrometry. Hydrochloric, nitric, sulphuric and perchloric acids at different concentrations (up to 0.6 mol l −1) have been tested. Sample uptake rate ( Q l) was also varied. The parameters evaluated for each variable were analyte and solvent transport rates and emission intensity. The combination of low acid concentrations (0.05–0.1 mol l −1) and low liquid flows (0.4 ml min −1) leads to the highest analyte transport rate and emission signal and to the lowest solvent transport rate. For Q l higher than 1.9 ml min −1, the use of an impact bead is advisable. Among the acids tested, sulphuric and perchloric acids give rise to higher emission intensities than hydrochloric acid and nitric acid. Nonetheless, the limits of detection (LODs) obtained with the MWDS are about the same magnitude irrespective of the solution employed. The LODs reached when using the MWDS are similar to those obtained with a desolvation system based on infrared heating of the aerosol.