Determination of thiocyanate in human saliva and urine by ion chromatography

Microextraction with smartphone detection of thiocyanate in saliva of tobacco smokers using paper-based analytical method

This study presents a novel, cost-effective approach involving spectrophotometric and smartphone paper-based (SPB) methods and a distinctive salting-out air-assisted dispersive microextraction procedure to quantify thiocyanate in saliva samples. The method relies on the inhibitory effect of thiocyanate on quinoneimine dye formation during the Emerson reaction with sodium hypochlorite. Spectrophotometry quantifies the extracted dye by monitoring quinoneimine color intensity reduction at 525 nm. In the SPB method, extracted dye is applied to a paper strip, a smartphone captures the colored paper, and an application analyzes red, green, and blue components. All analyte determination and extraction variables were explored. Both methods exhibit good linearity (10-100 μg/L) with a coefficient of determination of 0.9991 and a limit of detection of 7.5 μg/L for the spectrophotometric method, and a coefficient of determination of 0.9988 and a limit of detection of 8.8 μg/L for the SPB method. The calculated values for the enrichment factor and extraction recovery of the developed extraction methodology were 46% and 93%, respectively. The methods detect thiocyanate in saliva samples, producing results comparable to a validated method.

Applications of ion chromatography in urine analysis: A review

Ion chromatography (IC) plays a crucial role in urine analysis for diverse medical diagnoses. This paper reviews a comprehensive investigation into urine pretreatment techniques, as well as the design and development of IC systems for the measurement of various chemicals. Prior to analysis, urine samples commonly undergo pretreatment procedures such as dilution, filtration, purification, and concentration. These steps effectively eliminate interfering factors and facilitate the accurate and sensitive analysis of ultra-trace components. To separate and quantify different chemical elements or ions present in urine, a range of homemade or commercially available columns coupled with various detectors were employed. This study focuses on the analysis of chemicals such as heavy metals, halogens, pesticides, drugs, and other essential or toxic substances by IC methods.

Unlocking the potential of forensic traces: Analytical approaches to generate investigative leads

Forensic investigation involves gathering the information necessary to understand the criminal events as well as linking objects or individuals to an item, location or other individual(s) for investigative purposes. For years techniques such as presumptive chemical tests, DNA profiling or fingermark analysis have been of great value to this process. However, these techniques have their limitations, whether it is a lack of confidence in the results obtained due to cross-reactivity, subjectivity and low sensitivity; or because they are dependent on holding reference samples in a pre-existing database. There is currently a need to devise new ways to gather as much information as possible from a single trace, particularly from biological traces commonly encountered in forensic casework. This review outlines the most recent advancements in the forensic analysis of biological fluids, fingermarks and hair. Special emphasis is placed on analytical methods that can expand the information obtained from the trace beyond what is achieved in the usual practices. Special attention is paid to those methods that accurately determine the nature of the sample, as well as how long it has been at the crime scene, along with individualising information regarding the donor source of the trace.

Potentiometric Solid-Contact Ion-Selective Electrode for Determination of Thiocyanate in Human Saliva

A new solid-contact potentiometric ion-selective electrode for the determination of SCN- (SCN-ISE) has been described. Synthesized phosphonium derivative of calix[4]arene was used as a charged ionophore. The research included selection of the ion-selective membrane composition, determination of the ISEs metrological parameters and SCN-ISE application for thiocyanate determination in human saliva. Preparation of the ISEs included selection of a plasticizer for the ion-selective membrane composition and type of the electrode material. The study was carried out using ISE with liquid internal electrolyte (LE-ISE) and solid-contact electrodes made of glassy carbon (GC-ISE) and gold rods (Au-ISE). The best parameters were found for GC sensors for which the ion-selective membrane contained chloroparaffin as a plasticizer (S = 59.9 mV/dec, LOD = 1.6 ´ 10-6 M). The study of potentiometric selectivity coefficients has shown that the thiocyanate-selective sensor could be applied in biomedical research for determination of SCN- concentration in human saliva. The accuracy of the SCN- determination was verified by testing 59 samples of volunteers' saliva by potentiometric sensors and UV-Vis spectrophotometry as a reference technique. Moreover, SCN- concentrations in the smokers' and non-smokers' saliva were compared. In order to investigate the influence of various factors (sex, health status, taken medications) on the thiocyanate level in the saliva, more extensive studies on a group of 100 volunteers were carried out. Additionally, for a group of 18 volunteers, individual profiles of SCN- concentration in saliva measured on a daily basis for over a month were collected.

Nano-fluorescent probes based on DNA-templated copper nanoclusters for fast sensing of thiocyanate

A fast and label-free fluorescent sensor was developed to determine SCN⁻via inhibiting the formation of DNA-templated copper nanoclusters (CuNCs).

The effects of varieties and levels of rapeseed expeller cake on egg production performance, egg quality, nutrient digestibility, and duodenum morphology in laying hens

The objective of this study was to evaluate the effects of rapeseed expeller cake (REC) derived from Brassica napus rapeseed with different concentrations of glucosinolate (Gls) and erucic acid (EA) on the egg-production performance, egg quality, apparent nutrient digestibility, and intestinal morphology in laying hens. At 33 wk of age, a total of 1,080 laying hens were randomly divided into 9 treatment groups in a completely randomized design involving a control treatment without REC (a corn-soybean diet) and a 2 × 4 factorial arrangement with 2 concentrations of REC (at 7 and 14%) from 4varieties of rapeseed varying in Gls and EA concentrations [DY6 REC: 22.67 μmol/g (Gls, relative to rapeseed meal), 0.7% (EA, relative to total fatty acids); MB1 REC: 43.23 μmol/g, 3.5%; DY5 REC: 74.66 μmol/g, 16.20%; XH3 REC: 132.83 μmol/g, 44.60%]. The trial lasted for 8 wk. Compared with the control group, REC addition decreased the ADFI, egg production, egg weight, and egg mass of laying hens during wk1 to wk4, wk5 to wk8, and wk1 to wk8 (P < 0.05), and REC did not affect FCR, mortality during wk1 to wk4, wk5 to wk8, and wk1 to wk8 (P > 0.05). The XH3 REC group had a trend to lower egg weight when compared with the DY6 REC group during wk1 to wk8 (P = 0.07).REC decreased AME and DM digestibility at wk8 (P < 0.01), and REC addition in diet did not affect apparent nitrogen digestibility (P = 0.6). REC decreased villi height (P < 0.01) and increased crypt depth (P < 0.01). The XH3 REC group had a lower crude fat digestibility than the DY6 REC group, and the crude fat digestibility of the DY5 and MB1 REC groups was lower than the XH3 REC group (P < 0.01). The DY6 REC group had a higher villi height than the DY5, MB1, and XH3 REC groups (P < 0.01). The XH3 REC group had a higher crypt depth than the DY6, DY5, and MB1 REC groups (P < 0.01). The DY6 REC group had a higher value of the ratio of villi height to crypt depth than the DY5 and MB1 REC groups, and the DY5 and MB1 REC groups had a higher value of the ratio of villi height to crypt depth than the XH3 REC group (P < 0.01).REC decreased albumen height and Haugh unit during wk1 to wk8 (P < 0.01 and P = 0.004), and increased yolk color during wk1 to wk8 (P < 0.01).The XH3, MB1, and DY5 REC groups had a lower albumen height than the DY6 REC group during wk1 to wk8 (P < 0.01), and the XH3 and DY5 REC groups had a lower Haugh unit than the DY6 REC group during wk1 to wk8 (P < 0.01). The DY6 REC group had the highest value of yolk color than other three varieties of REC (DY5, MB1, XH3) at wk6 and wk8 (P < 0.01 and P < 0.01). It can be concluded that the exposure of laying hens to REC with higher Gls and EA (DY5, MB1, XH3) led to a lower egg weight, nutrient digestibility, intestinal absorptive area, and egg internal quality than those with lower Gls and EA (DY6).

The Effects of Low-Dose Irradiation on Human Saliva: A Surface-Enhanced Raman Spectroscopy Study

Biological effects of low-dose ionizing radiation (IR) have been unclear until now. Saliva, because of the ease of collection, could be valuable in studying low-dose IR effects by means of surface-enhanced Raman spectroscopy (SERS). The objective of our study was to compare the salivary SER spectra recorded before and after low-dose IR exposure in the case of pediatric patients (PP). Unstimulated saliva was collected from ten PP before and after irradiation with a cone beam computed tomography (CBCT) machine used for diagnostic purposes. The SERS measurements have been recorded on dried saliva samples using a solid nanosilver plasmonic substrate synthesized using an original method developed in our laboratory. The experimental results showed that salivary SER spectra are dominated by three vibrational bands (441,735 and 2107 cm^-1) that can be assigned to bending and stretching vibrations of salivary thiocyanate (SCN-). After exposure, an immediate increase of vibrational bands assigned to SCN- has been recorded in the case of all samples, probably as a result of IR interaction with oral cavity. This finding suggests that SCN- could be used as a valuable biomarker for the detection and identification of low-dose radiation effects.

A two-in-one device for online monitoring of direct immersion single-drop microextraction: an optical probe as both microdrop holder and measuring cell

For the first time an optical probe is proposed as the microdrop holder and simultaneously the measuring cell in a direct immersion single-drop microextraction (DI-SDME) procedure.

Organic anion composition of human whole saliva as determined by ion chromatography

BACKGROUND

The majority of studies examining anionic composition in human saliva have focused on inorganic anions only, and accompanying organic anion concentration has often been overlooked in the development of artificial salivas. The purpose of this study was to examine the major organic anionic species profile of human saliva, with a view to gaining further insight into human salivary chemistry.

METHODS

Unstimulated whole saliva was collected from 11 healthy volunteers over a period of 18months. Samples were subjected to ion chromatography for detection and quantification of organic and inorganic anions.

RESULTS

Among organic anions, acetate was predominant (0.24±0.38mmol/l), with lactate (0.01±0.04mmol/l), propionate (0.03±0.07mmol/l), and formate (0.02±0.03mmol/l) detected at lower levels. Acetate, propionate, and formate were detected in at least 80% of the saliva samples. Positive partial correlations were found between phosphate and sulfate (r=0.510, p-value=1.545×10(-4)), and between propionate and acetate (r=0.836, p-value=7.510×10(-14)).

CONCLUSION

Organic anionic species were consistently detected at low levels in saliva samples collected longitudinally over a period of 18months. These salivary components must be considered in order to understand saliva chemistry, and should not be neglected during the continuing development of artificial salivas.

Validation of urinary thiocyanate as a biomarker of tobacco smoking

Thiocyanate ion (SCN) is the major detoxication product of cyanide, which is converted to SCN by a thiosulphate sulphurtransferase, mainly in hepatic mitochondria. Low-level cyanide exposure for man is caused by factors such as dietary intake of cyanogenic glucosides, tobacco smoking, drug administration and occupational exposure to organic nitriles. Urinary SCN concentration was determined through a commercial kit for the analysis of cyanide in water. Spot urine samples were collected at 7:30 h and 12:30 h, from 99 healthy male white-collar office workers (non-smokers n=72, smokers n=27). Comparison of SCN excretion values did not show any difference between the morning and midday samples. The SCN median value of non-smokers was 24 μmol l(-1) (range 9-24 μmol l(-1)) and was statistically different from that of smokers (SCN = 92 μmol l(-1), range 33-275 μmol l(-1)) (p<0.001). In smokers median levels of SCN increased with the intensity of tobacco smoking and SCN individual excretion rose in relation to the number of cigarettes smoked daily (r=0.78, p<0.0001, n=16). In the whole group of investigated subjects SCN excretion was correlated with urinary cotinine, a well know biomarker of tobacco consumption (r=0.86, p<0.001, n=99). When the assay was applied as a smoking habit screening test, with a cut-off value of SCN=38 μmol l(-1) adopted to discriminate between non-smokers and smokers, the following smoker track-down predictive values resulted: 93% negative for non-smokers and 96% positive for smokers.

Determination of trace amounts of thiocyanate by a new kinetic procedure based on an induction period

A new, simple and sensitive kinetic spectrophotometric method with no need for removing of interfering substances is proposed for the determination of thiocyanate ion in biological and water samples. The procedure is based on the inhibiting effect of thiocyanate on the sodium periodate-potassium bromide-meta cresol purple (MCP) system in acidic media. The induction period of the reaction is proportional to the SCN- concentration. The decolorization of meta cresol purple by the reaction products was used to monitor the reaction spectrophotometrically at 525 nm. Under optimum conditions, thiocyanate can be determined in the range of 0.02-0.8 microg ml(-1) with a 3sigma detection limit of 5 ng ml(-1). The relative standard deviations for 10 replicate determinations of 0.060, 0.10 and 0.50 microg ml(-1) thiocyanate are 3.7, 2.4 and 1.0%, respectively. This method has been successfully used to the determination of thiocyanate content in smokers and non-smokers saliva and spiked water sample.

Extractive liquid–liquid spectrophotometric procedure for the determination of thiocyanate ions employing the ion pair reagent amiloride monohydrochloride

An accurate, inexpensive and less laborious liquid-liquid extractive spectrophotometric procedure for the determination of thiocyanate ions in aqueous media has been developed. The method has been based upon the formation of a yellow colored complex ion associate of the ion-pairing reagent 1-(3, 5-diamino-6-chloropyrazinecarboxyl) guanidine hydrochloride monohydrate, namely amiloride hydrochloride, DPG+.Cl- and the thiocyanate ions in aqueous media containing HNO3 (0.5 mol L(-1)) and subsequent extraction with 4-methyl-2-pentanone. The absorption electronic spectrum of the ion associate showed one well-defined peak at lambda(max) 366 nm. The stoichiometric mole ratio of DPG+.Cl- to the thiocyanate ions is 1:1. The effective molar absorptivity (epsilon) of the ion associate at lambda(max) 366 nm is 1.1+/-0.1x10(4) L mol(-1) cm(-1). The extraction constants (K(d), K(ex), and beta) enabled a simple and convenient use of the developed binary ion associate for the extractive spectrophotometric determination of traces of thiocyanate ions in the aqueous media. Beer's law and Ringbom's plots are obeyed in the concentration range 0.05-10 and 0.1-7 microg mL(-1) of the thiocyanate ions, respectively with a relative standard deviation of +/-2.3%. The calculated lower limits of detection (LOD) and quantitation (LOQ) of the developed procedure for the thiocyanate ions were found equal to 0.02 and 0.066 microg mL(-1), respectively. The developed method has been applied for the determination of trace amounts of thiocyanate ions in tap-, waste- and natural water samples and compared successfully with the reported methods at the 95% confidence level. The proposed method was also applied successfully for the determination of thiocyanate ions in saliva samples.

Determination of trace thiocyanate with nano-silver coated multi-walled carbon nanotubes modified glassy carbon electrode

Novel nano-silver coated multi-walled carbon nanotube composites were prepared and used to fabricate a modified electrode. The application of the nano-silver coated multi-walled carbon nanotube composites modified electrode for determination of trace thiocyanate is demonstrated for the first time. The influence of substrate, pH and interference of coexisting substances was investigated for response properties of the electrode. There was a linear relationship at the range 2.5 x 10(-9) to 5 x 10(-8) mol L(-1) and 5 x 10(-8) to 1 x 10(-6) mol L(-1) of thiocyanate with the decrement of anodic DPV peak currents. The limit of detection was 1 x 10(-9) mol L(-1)(S/N=3). The constructed electrode showed excellent reproducibility and stability. Actual urine and saliva samples of smoker and non-smoker were analyzed and satisfactory results were obtained. This method provides a new way to construct any electrode for biological and environmental analysis.

Carboxyhemoglobin and thiocyanate as biomarkers of exposure to carbon monoxide and hydrogen cyanide in tobacco smoke

The determination of biomarkers in human body fluids is a useful tool, which allows the quantitative assessment of the exposure to chemicals or complex mixtures of chemicals and of early biological effects as a result of the exposure. Biomarkers require validation before their successful application in human studies. This review describes some general purposes of human biomonitoring and biomarkers including the requirements for validation. Risk assessment and harm reduction of smoking and tobacco products, respectively, is a very suitable field for the application of biomarkers. A brief historical review shows that the application of biomarkers of exposure and effect in human smoking goes back more than 150 years. Two 'classical' biomarkers of exposure to tobacco, namely carboxyhemoglobin (COHb and its equivalent carbon monoxide in exhalate, COex) and thiocyanate (SCN) in body fluids are discussed in terms of sources of exposure, metabolism, disposition kinetics and influencing host factors. Data on COHb/COex and SCN in nonsmokers and smokers as well as the power to discriminate between smokers and nonsmokers are presented. Both biomarkers are significantly correlated with the daily cigarette consumption. Smoking machine-derived yields of the precursors carbon monoxide and hydrogen cyanide were not correlated with COHb/COex and SCN, respectively. It is concluded that, while COHb/COex is a useful biomarker for assessing the smoke inhalation, preferably in controlled studies, the application of SCN in body fluids as a biomarker for smoking is limited, mainly due to the abundance of other sources for SCN.

Validation of ion chromatography for human salivary anionic analysis

OBJECTIVE

Assess the applicability of ion chromatography (IC) for human saliva studies.

MATERIALS AND METHODS

The behaviour of an ion chromatograph (DX-100, Dionex) in the analysis of human saliva was examined in the following respects: calibration, reproducibility, recovery, and effect of pre-treatment conditions (dilution, temperature). The eluents used were 1.7 mM NaHCO3 + 1.8 mM Na2CO3 + 100 mg/L p-cyanophenol (2 mL/min) and 1.6 mM perfluorobutyric acid + 0.3 mM sodium hydroxide (0.3 mL/min) for inorganic and organic anions, respectively.

RESULTS

The calibration curves were satisfactorily linear, but did not have unit slope (log-log plot) in the case of chloride, phosphate, sulphate and acetate. No significant effects were detected for centrifugation temperature, or between runs on the same occasion.

CONCLUSION

IC appears to be a valuable technique well-suited to the efficient analysis of several salivary anions.

Kinetic Determination of Thiocyanate on the Basis of Its Catalytic Effect on the Oxidation of Methylene Blue with Potassium Bromate

This study reports a sensitive kinetic spectrophotometric method for the determination of trace amounts of thiocyanate. In acidic solution, Methylene Blue (MB) is oxidized by bromate to form a colorless compound. The reaction is accelerated by trace amounts of thiocyanate and can be followed by measuring the absorbance at 664 nm. The absorbance of the reaction decreased with an increase in the reaction time. Under the optimum experimental conditions (0.56 M of sulfuric acid, 3.9 x 10(-5) M of MB, 3.0 x 10(-3) M of bromate, 180 s, 25 degrees C), thiocyanate can be determined in the range 5.0 - 180 ng/ml. The relative standard deviations (n = 8) are 2.81 and 1.43% for 10.0 and 150 ng/ml thiocyanate, respectively. The detection limit of this method is (3sigma) 3.8 ng/ml. This method was successfully applied to the determination of thiocyanate in real samples.

Simultaneous determination of the tobacco smoke uptake parameters nicotine, cotinine and thiocyanate in urine, saliva and hair, using gas chromatography-mass spectrometry for characterisation of smoking status of recently exposed subjects

A method using gas chromatography (GC)-mass spectrometry (MS) for the simultaneous determination of the smoke uptake parameters thiocyanate, nicotine and cotinine in human tissues is reported. Nicotine, cotinine and thiocyanate, in combination with a phase-transfer catalyst, were extracted from urine, saliva and hair into dichloromethane (DCM). Thiocyanate was alkylated in the DCM-layer to form a pentafluorobenzyl derivative. The biochemical markers in DCM were directly injected into the GC system and separated on a DB-1MS column using a 9.4 min temperature program. The method was validated in urine and saliva between the limits of quantitation (1.0-15 microg ml(-1) thiocyanate, 0.010-3.0 microg ml(-1) nicotine and cotinine in urine, 0.010-1.0 microg ml(-1) nicotine and cotinine in saliva). The calibration curves were found to be linear (r > 0.996), the within- and between-day accuracy's were 83-120%, the repeatability coefficients of variation were 3-20% and the limits of detection were 0.060 ng ml(-1) thiocyanate and 0.60 ng ml(-1) nicotine and cotinine. The results of the analysis of the biomarkers in the urine of 44 volunteers were used to develop a predictive model for smoking status, using discriminant analysis. The classification model correctly classified 93.2% of cross-validated grouped cases. Saliva samples were used to confirm the results of the classification method.

Determination of urinary thiocyanate and nitrate using fast ion-interaction chromatography

A simple and rapid chromatographic method for determination of nitrite, nitrate and thiocyanate is reported, and applied to the analysis of non-, medium and heavy smokers' urine samples. Ion-interaction liquid chromatography was carried out on a short 30 mm x 4.6 mm C18 column (3 microm particle size) with a mobile phase of 10 mM tetrabutylammonium phosphate in 20% MeOH. The chromatography was performed at an elevated temperature of 45 degrees C, at a flow-rate of 1 ml/min. Detection was by direct UV absorption at 230 nm. Sample preparation involved centrifugation and dilution, followed by sample clean-up on a C18 solid-phase extraction cartridge. The developed method proved both precise (% RSD <2%) and sensitive (standard detection limits <0.1 mg/l), and yielded total run times of under 10 min when applied to urine analysis of smokers and non-smokers, with thiocyanate eluting in under 5 min.

Evaluation and application of liquid chromatographic columns coated with 'intelligent' ligands. II. Phospholipid column

The stationary phases of octadecylsilica (ODS) coated with phospholipid have been developed as a model of artificial lipid membranes for liquid chromatographic columns. An ODS column coated with phospholipid can be readily prepared by recycling a solution containing L-alpha-dipalmitoyl-phosphatidylcholine (DPPC) through an ODS column in a closed loop. DPPC becomes absorbed on the ODS surfaces by hydrophobic interaction between the acyl group of DPPC and the octadecyl group of the ODS surfaces. The DPPC column was usable when a mobile phase containing 30% (v/v) acetonitrile was delivered without detachment of the DPPC from the ODS surfaces. The retention behavior of ionic solutes on the DPPC column suggested that the retention was based on both ionic and electrostatic interactions between the solutes and the stationary phase. The retention factors on the DPPC column correlated well with the partition coefficients in liposome systems for alpha-adrenoceptor agonists and beta-blockers, indicating that the partition of solutes between the coated phase and buffer was similar to that in the liposome/water system. The DPPC column can be used in screening studies to predict the binding properties of drugs onto lipid membranes.

Evaluation and application of liquid chromatographic columns coated with 'intelligent' ligands: (I) acylcarnitine column

Unique stationary phases of octadecylsilica (ODS) coated with acylcarnitines have been developed for liquid chromatographic columns. The ODS column coated with acylcarnitine was readily prepared by recycling the solution containing acylcarnitine through an ODS column in a closed loop. Acylcarnitine was adsorbed on the ODS surfaces by hydrophobic interaction between the acyl group of acylcarnitine and the octadecyl group of the ODS phases. The ODS column coated with stearoylcarnitine (CN-18 column) was the most stable among the four columns coated with acylcarnitines of various acyl chain lengths (decanoylcarnitine, lauroylcarnitine, myristoylcarnitine, and stearoylcarnitine) under the condition of delivery of the mobile phase, indicating that adsorption of acylcarnitine on the ODS surfaces depended on the length of acyl chains. The CN-18 column was usable for delivering the mobile phase contained less than 20% (v/v) acetonitrile, retaining almost the same separation efficiency as the intact ODS column. The retention behavior of ionic solutes on the CN-18 column could be explained by both ionic and electrostatic interactions between the solutes and the stationary phase. The CN-18 column enabled efficient separation of inorganic anions, nicotinic acids, amino acids, and nucleotides. The chiral ODS column coated with enantiomer of stearoylcarnitine, L-stearoylcarnitine (L-CN-18 column) could achieve direct enantiomeric separation of DL-tryptophan, alpha-methyl-DL-tryptophan and DL-3-indolelactic acid using 100% water as the mobile phase. The L-CN-18 column could also separate enantiomers of amino acids and alpha-hydroxycarboxylic acids by ligand-exchange chromatographic mode using a mobile phase containing copper(II) ion. The chiral recognition is discussed for enantiomeric separation on the L-CN-18 column.

Ion chromatographic characterization of toxic solutions: analysis and ion chemistry of biological liquids

The literature on the analysis of biological fluids by ion chromatography is reviewed herein. It has been demonstrated that ion chromatography is the method of choice for the determination of anions such as chloride, nitrite, bromide, phosphate, nitrate, sulfate, oxalate, thiocyanate, thiosulfate, citrate, isocitrate, carbonate, and similar species. Cations such as sodium, ammonium, potassium, magnesium, and calcium in various biological solutions have also been successfully identified and quantified. The technique fulfils several requirements of a reliable microanalytical method by providing sufficient speed, automation, case of use, and accuracy. For many types of analyses, very little or even no sample preparation is required. Because of this, as presented in this review, ion chromatography is widely used not only to obtain reliable clinical data, but also to study ion chemistry. It has been an invaluable tool in nephrolithiasis and dental research. This review should provide a useful reference for analysts and researchers involved in clinical studies. The review is presented in four sections: (1) introduction, (2) methods of analysis, (3) ion chemistry and (4) critical comments and concluding remarks. Section 1, as usual, deals with the general introduction of the subject and objectives. Section 2 includes the review of the literature on ion chromatography (IC) methods developed for routine analysis of various analytes present in biological fluids. Section 3 deals with the applications of IC used in the understanding of ion chemistry of biological fluids. Specifically, it deals with the physical chemistry aspects related to nephrolithiasis and dental research, such as speciation, driving force for crystals formation and crystallization, and pathophysiology. Section 4 contains critical comments and concluding remarks.