Matrix interference free determination of perchlorate in urine by ion association-ion chromatography-mass spectrometry

Quantitative measurement of perchlorate in biological fluids is of importance to assess its toxicity and to study its effects on the thyroid gland. Whenever possible, urine samples are preferred in toxicologic/epidemiologic studies because sample collection is non-invasive. We present here a pretreatment method for the determination of perchlorate in urine samples that lead to a clean matrix. Urine samples, spiked with isotopically labeled perchlorate, are exposed to UV to destroy/decompose organic molecules and then sequentially treated with an H⁺-form cation exchange resin to remove protolyzable compounds, with ammonia to raise the pH to 10-11 and finally passed through a mini-column of basic alumina to remove the color and other organic matter. After filtration through a 0.45 μm syringe filter, the sample thus prepared can be directly injected into an ion chromatograph (IC). We use ion association-electrospray ionization-mass spectrometry (ESI-MS) to detect and quantify perchlorate. The proposed sample preparation method leads to excellent limits of detection (LOD's) for perchlorate since there is essentially no dilution of sample and the matrix effects are eliminated. Results of urine samples from both men and women volunteers are reported for perchlorate, as well as for iodide and thiocyanate, which are generally present at much higher concentrations and for which a “dilute and shoot” approach is adequate. The limit of detection (S/N = 3) for iodide, thiocyanate and perchlorate by the present method was 0.40, 0.10 and 0.080 μg l⁻¹, respectively.     

Challenges in determining perchlorate in biological tissues and fluids: implications for characterizing perchlorate exposure

The ability to measure environmental contaminants in biological tissues and fluids is important in the characterization of exposure. However, the analysis of certain contaminants in these matrices presents significant challenges. Perchlorate (ClO₄⁻) has emerged as a potential contaminant of concern primarily in drinking water and also in contaminated food. Significant advances have been made in the analysis of perchlorate in environmental matrices (water, soil) by ion chromatography (IC). In contrast, the analysis of perchlorate in extracts of biological tissues and fluids (vegetation, organs, milk, blood, urine, etc.) presents several challenges including small sample sizes, extracts with high matrix conductivity, and co-elution of other ions during IC analysis. To be able to detect low concentrations of perchlorate in biological samples, interferences must be removed or minimized, such as through the use of preparative chromatography cleanup techniques and/or alternative analytical methods less susceptible to common interferences (preconcentration or mass spectrometric detection). We present discussion and examples of the challenges encountered in the analysis of tissue extracts and fluids for perchlorate by IC and how some of those analytical challenges have been overcome.     

Preconcentration/preelution ion chromatography for the determination of perchlorate in complex samples

The determination of perchlorate in complex matrices by ion chromatography (IC) with an online preconcentration and preelution technique is discussed. The method was applied to different sample types containing large concentrations of matrix anions that would otherwise interfere with analysis via conventional IC. The present approach was highly effective in removing most of the matrix anions and was thus resistant to the interferences commonly encountered in a high ionic strength background. Method performance was evaluated by analyzing for low-level perchlorate in synthetic high ionic strength solutions, tissue extracts, and hydroponic nitrate fertilizer samples. Not only is it easier to practice the present method compared to USEPA Method 314.0, but for most of these samples the present approach provided equal to or better recovery of perchlorate than Method 314.0. With a sample of specific conductance 12,650 μS cm⁻¹, for example, the present method provided a perchlorate recovery of 101% at the 25 μg L⁻¹ level versus 89% by EPA Method 314.0. Method detection limits of perchlorate in hydroponic fertilizer samples with this method (130-190 μg kg⁻¹) are the lowest thus far reported.     

Ion chromatographic determination of chloride,chlorate, and perchlorate in sulfuric acid solutions

Summary The determination of chloride and perchlorate by non-suppressed ion chromatography in aqueous process solutions containing a high sulfate background is described. The method is reliable and fast. The sensitivity for perchlorate is lower than for other anions like nitrate, nitrite and chlorate. The detection limits are about 0.3 g/ml with linear calibration curves within a concentration range from 1 to 50 g/ml.     

Approaches to sample pretreatment in the determination of perchlorate in real world samples

Perchlorate can be determined by the tandem technique of ion chromatography (IC) coupled to electrospray ionization mass spectrometry (ESI-MS). However, detection by ESI-MS can be compromised by the coelution of matrix components that can suppress the analyte signal. In addition, the presence of surface-active and other types of matrix components can cause fouling of the electrospray inlet, reducing overall signal and requiring frequent maintenance. The influences of matrix components can be minimized by using analytical columns with different selectivities, in-line diversion of separated matrix components, and off-line selective removal of matrix components via ion exchange or adsorption. This paper will discuss these sample preparation approaches for samples containing anionic species including surfactants and inorganic ions that elute in the vicinity of perchlorate.     

Development and validation of a high-throughput double solid phase extraction-liquid chromatography-tandem mass spectrometry method for the determination of tetrodotoxin in human urine and plasma

A sensitive analytical method for the determination of tetrodotoxin (TTX) in urine and plasma matrices was developed using double solid phase extraction (C18 and hydrophilic interaction liquid chromatography) and subsequent analysis by HPLC coupled with tandem mass spectrometry. The double SPE sample cleanup efficiently reduced matrix and ion suppression effects. Together with the use of ion pair reagent in the mobile phase, isocratic elution became possible which enabled a shorter analysis time of 5.5 min per sample. The assay results were linear up to 500 ng mL⁻¹ for urine and 20 ng mL⁻¹ for plasma. The limit of detection and limit of quantification were 0.13 ng mL⁻¹ and 2.5 ng mL⁻¹, respectively, for both biological matrices. Recoveries were in the range of 75-81%. To eliminate the effect of dehydration and variations in urinary output, urinary creatinine-adjustment was made. TTX was quantified in eight urine samples and seven plasma samples from eight patients suspected of having TTX poisoning. TTX was detected in all urine samples, with concentrations ranging from 17.6 to 460.5 ng mL⁻¹, but was not detected in any of the plasma samples. The creatinine-adjusted TTX concentration in urine (ranging from 7.4 to 41.1 ng μmol⁻¹ creatinine) correlated well with the degree of poisoning as observed from clinical symptoms.     

Simultaneous determination of fluorine and iodine in urine by ion chromatography with electrochemical pretreatment

A new method for the simultaneous determination of fluorine and iodine in urine by ion chromatography(IC) with electrochemical pretreatment has been developed.The pretreatment was performed in a novel electrochemical oxidation-neutralization device(EOND),in which iodide of the sample was oxidized to iodate and the alkaline digestion sample solution was neutralized.Under the optimized conditions,the limits of detection(LOD,S/N = 3) were 2.5μg/L for fluoride and 20μg/L for iodate,respectively.The recoverie...     

Enzymatic reverse FIA method for total phenols determination in urine samples

A reverse flow injection spectrophotometric enzymatic method is proposed to quantify total phenols in urine samples. The polyphenol oxidase (PPO; EC 1.14.18.1) obtained as a crude extract from sweet potato root (Ipomoea batatas) was used as enzymatic catalyze. The detection limit, the sample throughput and relative standard deviation were 7.7 mg l⁻¹ of total phenols, 49 h⁻¹ and 0.9%, respectively. The method was applied to real samples and a recovery study was carried out in order to its validation.     

Determination of trace level of perchlorate in Antarctic snow and ice by ion chromatography coupled with tandem mass spectrometry using an automated sample on-line preconcentration method

A new ion chromatography coupled with tandem mass spectrometry（IC-ESI-MS/MS） method,with automated sampling and on-line preconcentration,has been developed for the determination of perchlorate in Antarctic snow and ice at low part-per-trillion（ng/L） levels.To the best of our knowledge, this is the first time that an analytical method is used for the determination of perchlorate in Antarctic snow and ice.The IC-ESI-MS/MS instrumentation consisted of an ICS2000 ion chromatography（IC） system coupled to an API3200 electrospray tandem mass spectrometer（ESI-MS/MS）.On-line preconcentration was realized through a six-port injector valve,a TAC-ULP1 concentrator column and an AS auto-sampler.Multiple reaction monitoring（MRM） mode was used to quantify the perchlorate anion.The transition of ³⁵Cl¹⁶O₄^-（m/z 98.9） into ³⁵Cl¹⁶O₃^-（m/z 82.9） was monitored for quantifying the main analyte,and the transition of ³⁷Cl¹⁶O₄^-（m/z 100.9） into ³⁷Cl¹⁶O₃^-（m/z 84.9） was monitored for examining a proper isotopic abundance ratio of ³⁵Cl to ³⁷Cl,which was used as a confirmation tool.The limit of detection（LOD） and limit of quantitation（LOQ） for the method was 0.2 ng/ L and 0.5 ng/L,respectively.And this new method exhibited acceptable accuracy and precision for samples at ng/L levels.All the tested snow and ice samples were found to contain measurable amount of perchlorate,ranging from 10 ng/L to 340 ng/L.     

Comparison of different cleanup procedures for oil crops based on the development of a trace analytical method for the determination of pyraclostrobin and epoxiconazole

The effects of different cleanup procedures in removing high‐molecular‐mass lipids and natural colorants from oil‐crop extracts, including dispersive solid‐phase extraction, low‐temperature precipitation and gel permeation chromatography, were studied. The pigment removal, lipid quantity, and matrix effects of the three cleanup methods were evaluated. Results indicated that the gel permeation chromatography method is the most effective way to compare the dispersive solid‐phase extraction and low‐temperature precipitation. Pyraclostrobin and epoxiconazole applied extensively in oil‐crop production were selected as typical pesticides to study and a trace analytical method was developed by gel permeation chromatography and ultra high performance liquid chromatography with tandem mass spectrometry. Average recoveries of the target pesticides at three levels (10, 50, and 100 μg/kg) were in the range of 74.7–96.8% with relative standard deviation values below 9.2%. The limits of detection did not exceed 0.46 μg/kg, whereas the limits of quantification were below 1.54 μg/kg and much lower than maximum residue limit in all matrices. This study may provide the essential data for optimizing the analytical method of pesticides in oil‐crop samples.     

Rapid on-line preconcentration and suppressed micro-bore ion chromatography of part per trillion levels of perchlorate in rainwater samples

The development of a rapid method for the determination of perchlorate in rain and drinking waters is presented. In the optimised method, an on-line preconcentration technique was employed utilising a 10 mm × 4.6 mm Phenomenex Onyx monolithic guard cartridge coated with (N-dodecyl-N,N-dimethylammonio)undecanoate for selective preconcentration, with subsequent elution into a fixed volume injection loop (‘heart-cut’ of the concentrator column eluate) and separation using an IonPac AS16 (250 mm × 2 mm) anion exchange column and a potassium hydroxide concentration gradient. Off-line optimisation studies showed that the coated monolith displayed near quantitative recovery up to 50 μg/L perchlorate level from standards prepared in reagent water. On-line preconcentration of perchlorate obtained detection limits down to 56 ng/L in reagent water, between 70 and 80 ng/L in rainwater samples and 2.5 μg/L in non-pretreated drinking water. After an additional sample sulphate/carbonate removal step, low ng/L perchlorate concentrations could also be observed in drinking water. The complete on-line method exhibited reproducibility for n = 10 replicate runs of R.S.D. ≤ 3% for peak height/area and R.S.D. = 0.08% for retention time. The optimised method, of 20 min total duration, was applied to the determination of perchlorate by standard addition in 10 rainwater samples and one drinking water sample. Concentrations of perchlorate present ranged from below the detection limit for four rainwater samples, with another three samples showing perchlorate present at between 70 and 100 ng/L, and one sample showing perchlorate present at 2.8 μg/L. Levels of 1.1 μg/L in the drinking water sample were also recorded.     

Determination of uric acid in human urine by ion chromatography with conductivity detector

A simple,fast,precise and eco-friendly analytical method for the determination of uric acid(UA) in human urine by ion chromatography(IC) was established.The sample pretreatment was not required,only needed centrifugation and filtration.The separation was carried out on a cation exchange column with 2.0 mmol/L nitric acid as mobile phase at the flow-rate 1.0 mL/min.A non-suppressed conductivity detector was used.The IC analysis time for one run was within 10 min under the optimized IC condition.The detection limits were 0.5μg/L(S/N = 3) for uric acid.The recovery was 100.1%while the relative standard deviation (RSD) was 1.8%from 10 measurements.     

Development of an analytical method based on microwave-assisted extraction and solid phase extraction cleanup for the determination of organochlorine pesticides in animal feed

A method to determine 21 organochlorine pesticides in animal feed samples using microwave assisted extraction and solid phase extraction cleanup was optimised regarding its main parameters. After extraction with hexane-acetone (50:50), three different sorbents (alumina/ENVI-Florisil, ENVI-Carb and ENVI-Carb II/PSA) were assayed for the cleanup step. Analytes were eluted with hexane-ethyl acetate (80:20) and determined by gas chromatography and electron capture detection followed by gas chromatography-mass spectrometry. ENVI-Carb and ENVI-Carb II/PSA provided colourless eluates but fewer interferent compounds were found in ENVI-Carb II/PSA chromatograms, so this system was selected to carry out the purification of the extracts. The analytical recoveries obtained with this method were close to 100% in most cases with relative standard deviations lower than 10%. These percentages were similar to those obtained with the Soxhlet extraction procedure, which shows the method suitable for the determination of organochlorine pesticides in animal feed material. The method was also validated with the analysis of a certified reference material (CRM-115 BCR), and the results obtained were in good accordance with the certified values.     

Stability of low levels of perchlorate in drinking water and natural water samples

Perchlorate ion (ClO₄⁻) is an environmental contaminant of growing concern due to its potential human health effects, impact on aquatic and land animals, and widespread occurrence throughout the United States. The determination of perchlorate cannot normally be carried out in the field. As such, water samples for perchlorate analysis are often shipped to a central laboratory, where they may be stored for a significant period before analysis. The stability of perchlorate ion in various types of commonly encountered water samples has not been generally examined—the effect of such storage is thus not known. In the present study, the long-term stability of perchlorate ion in deionized water, tap water, ground water, and surface water was examined. Sample sets containing approximately 1000, 100, 1.0, and 0.5 μg l⁻¹ perchlorate ion in deionized water and also in local tap water were formulated. These samples were analyzed by ion chromatography for perchlorate ion concentration against freshly prepared standards every 24 h for the first 7 days, biweekly for the next 4 weeks, and periodically after that for a total of 400 or 610 days for the two lowest concentrations and a total of 428 or 638 days for the high concentrations. Ground and surface water samples containing perchlorate were collected, held and analyzed for perchlorate concentration periodically over at least 360 days. All samples except for the surface water samples were found to be stable for the duration of the study, allowing for holding times of at least 300 days for ground water samples and at least 90 days for surface water samples.     

Quantitative analysis of perchlorate in extracts of whole fish homogenates by ion chromatography: comparison of suppressed conductivity detection and electrospray ionization mass spectrometry

The perchlorate anion (ClO ₄ ^– ) is an anthropogenic contaminant of increasing concern in water supplies, and has been shown to disrupt thyroid activity. Most perchlorate analyses are currently carried out by ion chromatography (IC) with suppressed conductivity detection (SCD). While this procedure has been demonstrated to provide acceptable performance for analysis of water samples, the determination of perchlorate in high-conductivity aqueous extracts of plant or animal material is not readily accomplished by IC-SCD unless lengthy cleanup protocols are applied. With the addition of electrospray ionization mass spectrometry (ESI-MS) to IC, it was hypothesized that the interference imposed by various ionic species could be significantly reduced without the need for purification; however, the analysis of perchlorate in relatively unpurified extracts of biologically derived homogenates by IC-ESI-MS has not previously been described in the literature. The research presented here represents a comparison of the capabilities of IC-SCD and IC-ESI-MS to detect perchlorate in reagent water and in crude extracts of perchlorate-exposed fish (threespine stickleback, Gasterosteus aculeatus). ESI-MS was found to compare favorably to SCD for the detection of perchlorate in deionized water, and to exceed SCD performance in perchlorate analysis of fish-derived extracts.     

改进的离子色谱法测定环境水样中的高氯酸盐

以亲水性阴离子交换柱IonPac AS16为分析柱, 以NaOH、乙腈和水的混合溶液为淋洗液, 采用电导检测法测定了环境水样中的痕量高氯酸盐. 通过添加有机改进剂有效地解决了4-氯苯磺酸和高氯酸盐共淋洗的问题. 实验考察了4种有机溶剂对高氯酸盐和4-氯苯磺酸保留时间的影响, 最终选定乙腈作为有机改进剂. 为了提高方法的灵敏度, 以AG19为浓缩柱对样品进行在线预浓缩. 采用预浓缩技术可使方法的检出限低至0.1 μg/L. 在0.2~200 μg/L线性范围内线性相关系数为0.9989, 将0.5 μg/L 高氯酸盐溶液连续进样测定11次, 所得峰面积的相对标准偏差(RSD)为4.2%. 将该方法应用于环境水样的测定, 加标回收率为93%~113%.     

离子色谱法测定化肥中高氯酸盐

本文研究了化肥中高氯酸盐含量的离子色谱分析方法.选择超声波萃取为样品提取方法并优化了萃取时间.筛选了离子色谱柱,确定使用IonPac AG21+AS21为分离柱;优化了淋洗液浓度和流速,确定以10 mmol/L NaOH为淋洗液,流速为0.3mL/min;进样体积为200μL.方法线性范围为0.1～10 mg/L,相关...     

Optimized cleanup methods of organic extracts for the determination of organic pollutants in biological samples

The analytical performances of various adsorbents used to clean up an organic extract of biological samples, particularly for the determination of polycyclic aromatic hydrocarbons (PAHs), polychlorobiphenyls (PCBs), both in mussel tissue and in krill samples, are critically compared. DDT and its degradation products, namely DDE and DDD, are also considered. Silica gel, alumina, aminopropyl-silica, cyanopropyl-silica, florisil, graphitized nonporous carbon and silica gel–alumina mixture (3:1) were used for column chromatography cleanup in combination with modified supercritical CO₂ as a mobile phase. Recovery and reproducibility were evaluated by analyzing standard solutions and standard reference materials containing various classes of pollutants. A silica gel–alumina mixture was found to be the most effective in the cleanup of organic extracts, allowing quantitative recoveries of all analytes to be obtained. Finally, the application of the optimized procedure to the determination of PCBs in Antarctic krill samples is presented.     

Ion‐pair cloud‐point extraction: A new method for the determination of water‐soluble vitamins in plasma and urine

A novel, simple, and effective ion‐pair cloud‐point extraction coupled with a gradient high‐performance liquid chromatography method was developed for determination of thiamine (vitamin B₁), niacinamide (vitamin B₃), pyridoxine (vitamin B₆), and riboflavin (vitamin B₂) in plasma and urine samples. The extraction and separation of vitamins were achieved based on an ion‐pair formation approach between these ionizable analytes and 1‐heptanesulfonic acid sodium salt as an ion‐pairing agent. Influential variables on the ion‐pair cloud‐point extraction efficiency, such as the ion‐pairing agent concentration, ionic strength, pH, volume of Triton X‐100, extraction temperature, and incubation time have been fully evaluated and optimized. Water‐soluble vitamins were successfully extracted by 1‐heptanesulfonic acid sodium salt (0.2% w/v) as ion‐pairing agent with Triton X‐100 (4% w/v) as surfactant phase at 50°C for 10 min. The calibration curves showed good linearity (r² > 0.9916) and precision in the concentration ranges of 1‐50 μg/mL for thiamine and niacinamide, 5–100 μg/mL for pyridoxine, and 0.5–20 μg/mL for riboflavin. The recoveries were in the range of 78.0–88.0% with relative standard deviations ranging from 6.2 to 8.2%.     

A rapid fluorimetric screening method for the 1,4-benzodiazepines: determination of their metabolite oxazepam in urine

Oxazepam is the major metabolite screened in urine samples for the evidence of the use of benzodiazepine drugs. The methods currently used, however, are laborious and time consuming. This paper proposes an oxazepam detection method based on its hydrolysis and cyclization - a reaction catalysed by cerium (IV) in an ortho-phosphoric acid-containing medium - to form 2-chloro-9(10H)-acridinone, a strongly fluorescent molecule. The variables involved in the hydrolysis and cyclization stages were optimised. Oxazepam was detectable in the 5-900 ng mL⁻¹ range, with a detection limit of 4.15 ng mL⁻¹ for k = 3. The method was successfully used for the determination of oxazepam in urine samples collected at different times after the oral administration of Valium^® and Tranxilium^®.