Dithiothreitol

154.25

154.25

1719757

222-468-7

DTXSID5041017

Needles from ether|Solid

29309099

118.06000

log Kow = -0.48 (est)

White Powder

1.3±0.1 g/cm3

42.5 °C

127.5 °C

>230 °F

1.579

H2O: freely soluble

2-8°C

1.28X10-4 mm Hg at 25 °C (est)

Characteristic

Henry's Law constant = 2.9X10-10 atm-cu m/mol at 25 °C (est)

Slightly hygroscopic|When heated to decomposition, it emits toxic fumes of SOx.|Hydroxyl radical reaction rate constant = 1.04X10-10 cu cm/molec-sec at 25 °C (est)

UN 3335

3

25-36/37/38-22-20/21/22

26-45-37/39-36

EK1610000

Xn

Stability Stable, but heat sensitive. Incompatible with strong oxidizing agents. Keep frozen at -20 to -10 C.

P261-P305 + P351 + P338

H302-H315-H319-H335

SRP: Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in air, soil or water; effects on animal, aquatic and plant life; and conformance with environmental and public health regulations. If it is possible or reasonable use an alternative chemical product with less inherent propensity for occupational harm/injury/toxicity or environmental contamination.|Product: Offer surplus and non-recyclable solutions to a licensed disposal company. Contact a licensed professional waste disposal service to dispose of this material. Dissolve or mix the material with a combustible solvent and burn in a chemical incinerator equipped with an afterburner and scrubber. Contaminated packaging: Dispose of as unused product.

|Warning|H302 (100%): Harmful if swallowed [Warning Acute toxicity, oral]|P261, P264, P270, P271, P280, P301+P312, P302+P352, P304+P340, P305+P351+P338, P312, P321, P330, P332+P313, P337+P313, P362, P403+P233, P405, and P501|Aggregated GHS information provided by 245 companies from 18 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.|H302 (97.83%): Harmful if swallowed [Warning Acute toxicity, oral]|Aggregated GHS information provided by 92 companies from 5 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.|H302: Harmful if swallowed [Warning Acute toxicity, oral]|P264, P270, P280, P301+P312, P302+P352, P305+P351+P338, P321, P330, P332+P313, P337+P313, P362, and P501

Eye/face protection: Safety glasses with side-shields conforming to EN166 Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).|Skin protection: Handle with gloves.|Body Protection: Complete suit protecting against chemicals, The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.|Respiratory protection: For nuisance exposures use type P95 (US) or type P1 (EU EN 143) particle respirator. For higher level protection use type OV/AG/P99 (US) or type ABEK-P2 (EU EN 143) respirator cartridges. Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).

Suitable extinguishing media: Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide. Advice for firefighters: Wear self-contained breathing apparatus for firefighting if necessary.

ACCIDENTAL RELEASE MEASURES; Personal precautions, protective equipment and emergency procedures: Use personal protective equipment. Avoid dust formation. Avoid breathing vapors, mist or gas. Ensure adequate ventilation. Avoid breathing dust. Environmental precautions: Do not let product enter drains. Methods and materials for containment and cleaning up: Pick up and arrange disposal without creating dust. Sweep up and shovel. Keep in suitable, closed containers for disposal.

Gloves must be inspected prior to use. Use proper glove removal technique (without touching glove's outer surface) to avoid skin contact with this product. Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices. Wash and dry hands|Further processing of solid materials may result in the formation of combustible dusts. The potential for combustible dust formation should be taken into consideration before additional processing occurs. Avoid contact with skin and eyes. Avoid formation of dust and aerosols. Provide appropriate exhaust ventilation at places where dust is formed.|ACCIDENTAL RELEASE MEASURES; Personal precautions, protective equipment and emergency procedures: Use personal protective equipment. Avoid dust formation. Avoid breathing vapors, mist or gas. Ensure adequate ventilation. Avoid breathing dust. Environmental precautions: Do not let product enter drains.|Handle in accordance with good industrial hygiene and safety practice. Wash hands before breaks and at the end of workday.|SRP: Local exhaust ventilation should be applied wherever there is an incidence of point source emissions or dispersion of regulated contaminants in the work area. Ventilation control of the contaminant as close to its point of generation is both the most economical and safest method to minimize personnel exposure to airborne contaminants. Ensure that the local ventilation moves the contaminant away from the worker.

IDENTIFICATION AND USE: 1,4-Dithiothreitol (DTT) is frequently used in biochemical experiments that involve proteins or peptides, protecting sulfhydryl groups from oxidation and reducing disulfide bonds between cysteines. It is also used in the study of disulfide exchange reactions of protein disulfides, and DTT is able to keep glutathione in the reduced state. It has been tested as experimental therapy in cystinosis or medical conditions resulting from ion or metal toxicity. HUMAN STUDIES: DTT triggers apoptosis in HL-60 cells. DTT is used in the liquefication of sputum recovered from asthma patients. Two male patients with late stage (uremic) infantile nephropathic cystinosis were treated by mouth with the reducing agent DTT, at doses not exceeding 25 mg/kg body weight three times per day. Other than nausea and vomiting at the maximum dose range, no apparent toxicity was observed. One subject died in uremia in the 24th month of the study. ANIMAL STUDIES: Depression of rat's heart and intestinal tissues by DTT severely limits its use as antioxidant to protect readily air oxidizable drugs during pharmacological testing with these standard tissue preparations. Treatment with dithiothreitol can mimic intracellular activation of the potent cytotoxin of Clostridium difficile, toxin B.

The extensively used thiol antioxidants (dithiothreitol, glutathione, and N-acetylcysteine) in combination with hydroxycobalamine (vitamin B12) gain toxic activity in relation to human lymphocytic leukemia cell line HL60. Combined treatment with thiol and vitamin B12 was followed by early destabilization of lysosomes and apoptotic death of cells. The cytotoxic effect was abolished by caspase inhibitors. An iron-chelating agent deferoxamine partly prevented cell death, while lysosomal protease inhibitor pepstatin produced no protective effect.|Arsenic is naturally occurring toxic metalloid and drinking As2 O3 containing water are recognized to be related to increased risk of neurotoxicity, liver injury, blackfoot disease, hypertension, and cancer. On the contrary, As2 O3 has been an ancient drug used in traditional Chinese medicine with substantial anticancer activities, especially in the treatment of acute promyelocytic leukemia as well as chronic wound healing. However, the cytotoxicity and detail mechanisms of As2 O3 action in solid cancer cells, such as oral cancer cells, are largely unknown. In this study, we have primarily cultured four pairs of tumor and nontumor cells from the oral cancer patients and treated the cells with As2 O3 alone or combined with dithiothreitol (DTT). The results showed that 0.5 uM As2 O3 plus 20 uM DTT caused a significant cell death of oral cancer cells but not the nontumor cells. Also As2 O3 plus DTT upregulated Bax and Bak, downregulated Bcl-2 and p53, caused a loss of mitochondria membrane potential in oral cancer cells. On the other way, As2 O3 also triggered endoplasmic reticulum stress and increased the levels of glucose-regulated protein 78, calpain 1 and 2. Our results suggest that DTT could synergistically enhance the effects of As2 O3 on killing oral cancer cells while nontoxic to the nontumor cells. The combination is promising for clinical practice in oral cancer therapy and worth further investigations.|It has been found previously that vitamin B12b amplifies significantly the cytotoxic effects of ascorbic acid by catalyzing the formation of reactive oxygen species, and the antioxidant dithiothreitol (DTT), in contrast to catalase, does not prevent the cytotoxicity. Therefore, in this study we examined whether B12b is able to enhance the cytotoxicity of DTT. It was revealed that B12b strongly increases the cytotoxic effect of DTT. Vitamin B12b added to DTT catalyzed the generation and drastic accumulation of hydrogen peroxide in culture medium to a concentration of 260 microM within 7 min. The extracellular oxidative burst induced by the combination of B12b and DTT (DTT + B12b) was accompanied by intracellular oxidative stress, the destabilization of lysosomes, and damage to DNA. The accumulation of DNA lesions led to the initiation of apoptotic cell death, including the activation of caspase-3 and the release of cytochrome c. The antioxidants pyruvate and catalase completely prevented the DTT + B12b-induced oxidative stress and cell death. The iron chelators desferrioxamine and phenanthroline prevented the geno- and cytotoxic action of the combination although they did not reduce the exogenous oxidative burst, indicating a key role for intracellular iron in the cytotoxicity of the combination. Thus, vitamin B12b dramatically enhances the cytotoxicity of DTT, catalyzing the generation of hydrogen peroxide and inducing extra- and intracellular oxidative stress, early destabilization of lysosomes, and iron-dependent DNA damage.|Inorganic trivalent arsenicals are vicinal thiol-reacting agents, and dithiothreitol (DTT) is a well-known dithiol agent. Interestingly, both decreasing and increasing effects of DTT on arsenic trioxide-induced apoptosis have been reported. We now provide data to show that, at high concentrations, DTT, dimercaptosuccinic acid (DMSA), and dimercaptopropanesulfonic acid (DMPS) decreased arsenic trioxide-induced apoptosis in NB4 cells, a human promyelocytic leukemia cell line. In contrast, at low concentrations DTT, DMSA, and DMPS increased the arsenic trioxide-induced apoptosis. DTT at a high concentration (3 mM) decreased, whereas at a low concentration (0.1 mM), it increased the cell growth inhibition of arsenic trioxide, methylarsonous acid (MMA(III)), and dimethylarsinous acid (DMA(III)) in NB4 cells. DMSA and DMPS are currently used as antidotes for acute arsenic poisoning. These two dithiol compounds also show an inverse-hormetic effect on arsenic toxicity in terms of DNA damage, micronucleus induction, apoptosis, and colony formation in experiments using human epithelial cell lines derived from arsenic target tissues such as the kidney and bladder. With the oral administration of dithiols, the concentrations of these dithiol compounds in the human body are likely to be low. Therefore, the present results suggest the necessity of reevaluating the therapeutic effect of these dithiol compounds for arsenic poisoning.|For more Interactions (Complete) data for 1,4-Dithiothreitol (7 total), please visit the HSDB record page.

LD50 Mice im 108 mg/kg|LD50 Mice ip 154 mg/kg

1,4-Dithiothreitol's production and use as a laboratory reagent(1) may result in its release to the environment through various waste streams(SRC).

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 1(SRC), determined from a structure estimation method(2), indicates that 1,4-dithiothreitol is expected to have very high mobility in soil(SRC). Volatilization of 1,4-dithiothreitol from moist soil surfaces is not expected to be an important fate process(SRC) given an estimated Henry's Law constant of 2.9X10-10 atm-cu m/mole(SRC), developed using a fragment constant estimation method(2). 1,4-Dithiothreitol is not expected to volatilize from dry soil surfaces(SRC) based upon an estimated vapor pressure of 1.3X10-4 mm Hg at 25 °C(SRC), determined from a fragment constant method(2). Biodegradation data in soil were not available(SRC, 2018).|AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 1(SRC), determined from a structure estimation method(2), indicates that 1,4-dithiothreitol is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is not expected(3) based upon an estimated Henry's Law constant of 2.9X10-10 atm-cu m/mole(SRC), developed using a fragment constant estimation method(2). According to a classification scheme(4), an estimated BCF of 3(SRC), from an estimated log Kow of -0.48(2) and a regression-derived equation(2), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Biodegradation data in water were not available(SRC, 2018).|ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), 1,4-dithiothreitol, which has an estimated vapor pressure of 1.3X10-4 mm Hg at 25 °C(SRC), determined from a fragment constant method(2), will exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase 1,4-dithiothreitol is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 4 hours(SRC), calculated from its rate constant of 1.0X10-10 cu cm/molecule-sec at 25 °C(SRC) that was derived using a structure estimation method(2). Particulate-phase 1,4-dithiothreitol may be removed from the air by wet and dry deposition(SRC). 1,4-Dithiothreitol does not contain chromophores that absorb at wavelengths >290 nm(3) and, therefore, is not expected to be susceptible to direct photolysis by sunlight(SRC).

The rate constant for the vapor-phase reaction of 1,4-dithiothreitol with photochemically-produced hydroxyl radicals has been estimated as 1.0X10-10 cu cm/molecule-sec at 25 °C(SRC) using a structure estimation method(1). This corresponds to an atmospheric half-life of about 4 hours at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). 1,4-Dithiothreitol is not expected to undergo hydrolysis in the environment due to the lack of functional groups that hydrolyze under environmental conditions(2). 1,4-Dithiothreitol does not contain chromophores that absorb at wavelengths >290 nm(2) and, therefore, is not expected to be susceptible to direct photolysis by sunlight(SRC).

An estimated BCF of 3 was calculated in fish for 1,4-dithiothreitol(SRC), using an estimated log Kow of -0.48(1) and a regression-derived equation(1). According to a classification scheme(2), this BCF suggests the potential for bioconcentration in aquatic organisms is low(SRC).

Using a structure estimation method based on molecular connectivity indices(1), the Koc of 1,4-dithiothreitol can be estimated to be 1(SRC). According to a classification scheme(2), this estimated Koc value suggests that 1,4-dithiothreitol is expected to have very high mobility in soil(SRC).

The Henry's Law constant for 1,4-dithiothreitol is estimated as 2.9X10-10 atm-cu m/mole(SRC) developed using a fragment constant estimation method(1). This Henry's Law constant indicates that 1,4-dithiothreitol is expected to be essentially nonvolatile from water and moist soil surfaces(2). 1,4-Dithiothreitol is not expected to volatilize from dry soil surfaces(SRC) based upon an estimated vapor pressure of 1.3X10-4 mm Hg(SRC), determined from a fragment constant method(1).

NIOSH (NOES Survey 1981-1983) has statistically estimated that 1,196 workers (906 of these are female) were potentially exposed to 1,4-dithiothreitol in the US(1). Occupational exposure to 1,4-dithiothreitol may occur through inhalation and dermal contact with this compound at workplaces where 1,4-dithiothreitol is produced or used. Use data indicate that the general population is not likely to be exposed to 1,4-dithiothreitol(SRC).

Two male patients with late stage (uremic) infantile nephropathic cystinosis (INC) were treated by mouth with the reducing agent dithiothreitol (DTT), at doses not exceeding 25 mg/kg body weight three times per day. Three sequential periods of observation were obtained in both patients: on thiol (8.5 months); off thiol (8-9 months); on thiol again (7 months or longer)... Whereas chemical methods are not reliable for detecting and measuring DTT in biologic fluids, preliminary evidence indicates that a silylated derivative of oxidized DTT can be detected in the urine of patients receiving DTT by mouth. This finding suggests that the thiol is absorbed and excreted.

Two male patients with late stage (uremic) infantile nephropathic cystinosis (INC) were treated by mouth with the reducing agent dithiothreitol (DTT), at doses not exceeding 25 mg/kg body weight three times per day. Three sequential periods of observation were obtained in both patients: on thiol (8.5 months); off thiol (8-9 months); on thiol again (7 months or longer)... Whereas chemical methods are not reliable for detecting and measuring DTT in biologic fluids, preliminary evidence indicates that a silylated derivative of oxidized DTT can be detected in the urine of patients receiving DTT by mouth. This finding suggests that the thiol is absorbed and excreted.

Oxidized form: <2.5% (absorbance at 283nm)

/SRP:/ Immediate first aid: Ensure that adequate decontamination has been carried out. If patient is not breathing, start artificial respiration, preferably with a demand valve resuscitator, bag-valve-mask device, or pocket mask, as trained. Perform CPR if necessary. Immediately flush contaminated eyes with gently flowing water. Do not induce vomiting. If vomiting occurs, lean patient forward or place on left side (head-down position, if possible) to maintain an open airway and prevent aspiration. Keep patient quiet and maintain normal body temperature. Obtain medical attention. /Poisons A and B/|/SRP:/ Basic treatment: Establish a patent airway (oropharyngeal or nasopharyngeal airway, if needed). Suction if necessary. Watch for signs of respiratory insufficiency and assist ventilations if needed. Administer oxygen by nonrebreather mask at 10 to 15 L/min. Monitor for pulmonary edema and treat if necessary ... . Monitor for shock and treat if necessary ... . Anticipate seizures and treat if necessary ... . For eye contamination, flush eyes immediately with water. Irrigate each eye continuously with 0.9% saline (NS) during transport ... . Do not use emetics. For ingestion, rinse mouth and administer 5 mL/kg up to 200 mL of water for dilution if the patient can swallow, has a strong gag reflex, and does not drool ... . Cover skin burns with dry sterile dressings after decontamination ... . /Poisons A and B/|/SRP:/ Advanced treatment: Consider orotracheal or nasotracheal intubation for airway control in the patient who is unconscious, has severe pulmonary edema, or is in severe respiratory distress. Positive-pressure ventilation techniques with a bag valve mask device may be beneficial. Consider drug therapy for pulmonary edema ... . Consider administering a beta agonist such as albuterol for severe bronchospasm ... . Monitor cardiac rhythm and treat arrhythmias as necessary ... . Start IV administration of D5W TKO /SRP: "To keep open", minimal flow rate/. Use 0.9% saline (NS) or lactated Ringer's (LR) if signs of hypovolemia are present. For hypotension with signs of hypovolemia, administer fluid cautiously. Watch for signs of fluid overload ... . Treat seizures with diazepam (Valium) or lorazepam (Ativan) ... . Use proparacaine hydrochloride to assist eye irrigation ... . /Poisons A and B/

/HUMAN EXPOSURE STUDIES/ Two male patients with late stage (uremic) infantile nephropathic cystinosis (INC) were treated by mouth with the reducing agent dithiothreitol (DTT), at doses not exceeding 25 mg/kg body weight three times per day. Three sequential periods of observation were obtained in both patients: on thiol (8.5 months); off thiol (8-9 months); on thiol again (7 months or longer). Other than nausea and vomiting at the maximum dose range, no apparent toxicity was observed. One subject died in uremia in the 24th month of the study.|/ALTERNATIVE and IN VITRO TESTS/ Previous studies have shown that under certain conditions some thiol-containing compounds can cause apoptosis in a number of different cell lines. Herein, we investigated the apoptotic pathways in HL-60 cells triggered by dithiothreitol (DTT), used as a model thiol compound, and tested the hypothesis that thiols cause apoptosis via production of hydrogen peroxide (H2O2) during thiol oxidation. The results show that, unlike H2O2, DTT does not induce apoptosis via a mitochondrial pathway. This is demonstrated by the absence of early cytochrome c release from mitochondria into the cytosol, the lack of mitochondrial membrane depolarization at early times, and the minor role of caspase 9 in DTT-induced apoptosis. The first caspase activity detectable in DTT-treated cells is caspase 3, which is increased significantly 1 - 2 hr after the start of DTT treatment. This was shown by following the cleavage of both a natural substrate, DFF-45/ICAD, and a synthetic fluorescent substrate, z-DEVD-AFC. Cleavage of substrates of caspases 2 and 8, known as initiator caspases, does not start until 3 - 4 hr after DTT exposure, well after caspase 3 has become active and at a time when apoptosis is in late stages, as shown by the occurrence of DNA fragmentation to oligonucleosomal-sized pieces. Although oxidizing DTT can produce H2O2, data presented here indicate that DTT-induced apoptosis is not mediated by production of H2O2 and occurs via a novel pathway that involves activation of caspase 3 at early stages, prior to activation of the common 'initiator' caspases 2, 8 and 9.|/ALTERNATIVE and IN VITRO TESTS/ BACKGROUND: Dithiothreitol (DTT), which is used for sputum homogenization, may split S-S bonds of the bronchial mucins as well as other proteins and, thus, may have a detrimental effect on inflammatory mediators that are present in sputum. OBJECTIVE: To evaluate the effects of physical sputum homogenization, using ultrasonic and chemical (ie, DTT) means, on the concentrations of eosinophil cationic protein (ECP), eosinophil protein X (EPX), eosinophil peroxidase (EPO), and myeloperoxidase (MPO) in the sputum of patients with asthma. METHODS: The collection of sputum samples from nine patients with asthma was induced by their inhaling a sterile 3% saline solution for 10 min from an ultrasonic nebulizer. One half of the sputum sample was homogenized by ultrasound, and the other half was liquefied by DTT. The supernatant of the ultrasonically homogenized specimen was divided into the following three portions: (1) immediately frozen; (2) stored for 15 min at 37 degrees C; and (3) additionally treated with DTT. The supernatant of the sputum sample that was liquefied by DTT was divided into the following two portions: (1) immediately frozen; and (2) additionally subjected to ultrasound. The concentrations of ECP, EPO, EPX, and MPO in the sputum samples were measured using immunoassays. RESULTS: Statistically significant differences were found between the ultrasonically homogenized specimens that had been either processed immediately or stored at 37 degrees C and those treated by DTT, but only for concentrations of EPO and MPO (p < 0.005). No effect of temperature on the mediators in the ultrasonically homogenized specimens could be detected. Ultrasonic homogenization had no influence on the mediators in the samples liquefied by DTT. However, the addition of DTT to the cell-free supernatant of the ultrasonically homogenized sputum samples caused a significant fall in measured EPO and MPO concentrations. CONCLUSIONS: The sputum processing by DTT caused a statistically significant fall in EPO and MPO concentrations but did not significantly influence the measured concentrations of ECP and EPX.|/ALTERNATIVE and IN VITRO TESTS/ BACKGROUND: The use of Dithiothreitol (DTT) to improve cell dispersion is an integral step in induced sputum examination, which has become an important noninvasive method of assessing airway inflammation. Several studies have shown that sputum treatment with DTT does not affect cell morphology, differential cell counts, and cytokine levels in the supernatant. However, the effect of DTT on cell surface marker expression has not been systematically studied. OBJECTIVE: We have investigated the effect of different DTT concentrations on antigen expression on peripheral blood cells compared with antigen expression on PBS-treated cells. METHODS: Peripheral blood from different healthy donors was incubated with either DTT or PBS, washed, and then incubated with different fluorescence-labeled antibodies. Analysis was performed after lysis of erythrocytes on a calibrated flow cytometer. Respective cell populations were identified, and the mean fluorescence intensity of surface-marker expression for each cell population was compared between DTT- and PBS-treated cells. RESULTS: We found that DTT decreased the expression of CD11a and CD49d on lymphocytes and eosinophils. The expression of CD11a on neutrophils was also decreased after DTT treatment. DTT increased CD11b expression on lymphocytes, neutrophils, and eosinophils. DTT might also have a mild effect on cell activation. It decreased the expression of CD2 on lymphocytes and variably affected the expression of EG2 in eosinophils, although it had no significant effect on HLA-DR expression on lymphocytes. CONCLUSION: Our findings show that DTT can affect antigen expression on lymphocytes, neutrophils, and eosinophils and suggest the need for further investigation of similar consequences on induced sputum analysis.|For more Human Toxicity Excerpts (Complete) data for 1,4-Dithiothreitol (6 total), please visit the HSDB record page.

Cleland Reagent

2,3-Butanediol, 1,4-dimercapto-, (2R,3R)-rel-: ACTIVE|DTT-preparation is optically inactive, i.e. it is the D,L-DTT.|1,4-dithiothreitol is commonly known as Cleland's reagent. It confers protection to thiol groups and reduces disulfide bonds in peptides and proteins. It reduces disulfide bonds to sulfhydryl group and is commonly used in receptor studies, to determine the functional importance of disulfide bonds during receptor occupancy and functionality.

Dithiothreitol (DTT) and other reducing agents are typically used in refolding processes of recombinant human proteins during their purification from inclusion bodies. Due to its toxicity, it is essential to monitor the clearance of DTT throughout the analytical flow from the refolding phase to the final formulated product. Here we report a direct, simple, and fast liquid chromatography method using UV and tandem mass spectrometry (MS/MS) detection for DTT evaluation in complex protein mixtures. In aqueous solution DTT exists as an equilibrium mixture of the oxidized and the reduced form (H(2)DTT --> DTT(ox)) and the quantitation tools should therefore be applicable to both forms in a single step or in multiple steps. Oxidation of DTT with aqueous copper(II) nitrate trihydrate solution was introduced to determine a single oxidized compound, i. e. DTT(ox). Proteins and other components of high molecular masses were separated from DTT(ox) by ultrafiltration. Consequently, efficient separation of the DTT(ox )from other flow-through mixture components (sugars, polymers, salts, protein stabilizers) was achieved on an Atlantis dC(18) column. After chromatographic separation, DTT(ox) was selectively identified by UV absorbance at 285 nm or by selected reaction monitoring, measuring signal transition between m/z 151 --> 105. The method was validated in terms of specificity, accuracy, precision, linearity, and limit of quantification and detection. A reversed-phase HPLC separation method with atmospheric pressure chemical ionization and MS/MS detection in negative ion mode is highlighted as a viable alternative to currently existing quantitation methods involving DTT derivatization and HPLC fluorescence detection. The described approach offers simple, straightforward, selective, and high-throughput DTT quantitation in protein mixtures.