NIOSH Manual of Analytical Methods (NMAM), Fifth Edition

NIOSH Manual of Analytical Methods (NMAM) 5th Edition 

BACKUP DATA REPORT 

NIOSH Method No. 8320

Title: Butyltin trichloride in urine

Analyte: Butyltin Trichloride

Author/developer:Don C. Wickman, James B. Perkins

Date: June 24, 2016 

NOTE: Method developed under contract #CDC-200-2001-0800

Disclaimer: Mention of any company or product does not constitute endorsement by the National 

Institute for Occupational Safety and Health, Centers for Disease Control and Prevention. In addition, 

citations to websites external to NIOSH do not constitute NIOSH endorsement of the sponsoring 

organizations or their programs or products. Furthermore, NIOSH is not responsible for the content of 

these websites. All web addresses referenced in this document were accessible as of the publication 

date. 
2 

BUTYLTIN TRICHLORIDE IN URINE

I. Introduction:

Butyltin compounds have been used extensively as antifouling coatings on ships and as a

consequence, much work has been done on analyzing organotins in sediments, biota, and aqueous 

samples [1-13]. Included in this body of work are reviews of analytical methods [4, 10]. 

Of the three butyltin chlorides, monobutyl tin is the least toxic and tributyl tin the most. 

This trend is also true of other alkyl tins. A single alkyl chain compound is generally less toxic 

than the di- or tri-alkyltin. Of alkyl tins, the shorter the chain, e.g. ethyltins and methyltins, the 

more toxic the compound; the longer chain compounds are less toxic. A number of reviews of 

toxicological data on organotins are available [14-17]. 

There have been several reported incidences of human fatalities after exposure to organotin 

compounds. In France, in 1954, a pharmaceutical preparation called Stalinon caused a number of 

deaths. Stalinon was an oral capsule containing 15 mg of diethyltin diiodide prescribed for boils, 

staphylococcal skin infections, osteomyelitis, anthrax and acne. The main impurities were 

monoethyltin triiodide and triethyltin iodide. The triethyltin iodide was about 1.5 mg/capsule and 

was believed to be the main cause of the poisoning. Over 100 of the known 217 cases of poisoning 

died after an estimated dose of 3 g triethyltin iodide over 6-8 weeks. Triethyltin iodide as low as 70 

mg over eight days appeared toxic in adults. Symptoms appeared after four days. If death occurred, 

it was often preceded by a coma or was during convulsions or from respiratory or cardiac failure 

[16]. 

In a separate incident, one worker out of six died twelve days after an industrial exposure to 

50:50 dimethyltin and trimethyltin chloride vapor. Exposure was 1.5 hours total over three days. 

No exposure levels were given. Lethal doses for mono-organotins, however, ranging from 1500 - 
3

6000 mg/kg for rodents have been reported suggesting these compounds have relatively low 

toxicity [15]. More recently, three died and over a thousand were poisoned by lard contaminated 

with tri- and di-methyltin in China [18].

Butyltin compounds are also used as stabilizers in plastics, catalysts, and biocides. Butyltin 

trichloride is increasingly used in the glass industry [19]. A thin coating of tin oxide is deposited on 

glass bottles by the decomposition of butyltin trichloride at elevated temperatures. Workers in this 

phase of bottle production may be exposed to the unreacted tin chloride. Because of the expanding 

industrial processes employing organotin compounds, a number of papers have recently quantified 

these compounds in urine, blood and air [18, 20-22]. While there are exposure limits for tin and 

organic tin compounds in air, there are currently no such exposure limits for tin or butyltin 

compounds in urine or blood.

Due to the organometallic nature of these compounds, a wide variety of analytical 

techniques can be employed to analyze these compounds. Atomic emission and absorption 

spectroscopy as well as inductively-coupled plasma mass spectrometry (ICP-MS) have been used 

to quantitate tin from an inorganic perspective [3, 5, 6, 9, 11, 18, 20, 21, 23, 24]. Because of the 

ionic behavior of the alkyltin halides, derivatization procedures such as Grignard reagents (which 

are alkyl, vinyl, or aryl-magnesium halides), sodium tetraethylborate or sodium borohydride have 

been used to convert the tin halides to pure alkyltin or alkyltin hydrides which are then 

chromatographically separated and detected often utilizing a flame photometric detector (FPD) or 

mass spectrometry [1, 3, 4, 12, 13, 18, 22, 25, 28, 29].
4

II. Reagents:

Reagent Vendor Purity (%)

 Butyltin trichloride Aldrich Chemical 95

Dibutyltin dichloride Aldrich Chemical 96

Tributyltin chloride Aldrich Chemical 96

Tetraethyl tin Acros Chemical 97

Tetrabutyl tin Acros Chemical 96

Sodium tetraethylborate Aldrich Chemical 97

Ethylmagnesium bromide Aldrich Chemical 1.0 M solution in tetrahydrofuran

Hexane Burdick & Jackson Pesticide Grade

Sulfuric acid Fisher Scientific 95-98

Sodium acetate, acetic acid

buffer, pH 4

Fisher Scientific Reagent Grade

Sodium citrate dihydrate J.T. Baker 99.6

Citric acid monohydrate Mallinckrodt 100

Toluene Burdick & Jackson Pesticide Grade

Tropolone Lancaster 98 

Alumina, acid, Brockman activity 

1, 80-200 mesh

Fisher Scientific Chromatographic Grade 

Sodium sulfate, anhydrous Fisher Scientific Reagent Grade

UriSub® synthetic urine CST Technologies, Inc. N/A

Florisil® Sigma Chromatographic Grade 

III. Solutions Preparation:

1% Sodium tetraethylborate was prepared by weighing typically less than 350 mg sodium

tetra-ethylborate into a 40-mL VOA glass vial with a PTFE septum. This weighing must be done in 

an inert atmosphere of nitrogen. Cap the vial and store in a freezer until use. For use, add sufficient 

water to prepare a 1% w/v solution by syringe through the septum. Once the solution is prepared, 

the cap can be removed. Prepare fresh daily. 

To prepare the citric acid/sodium citrate buffer, dissolve 20.554 g citric acid and 0.652 g 

sodium citrate (~pH 2.3) in 1 L deionized water. Additional buffers at pH 3 and 4 were prepared 

for method development experiments. See Table 3 in section VI. B. for buffer composition. 

0.1% tropolone in toluene was prepared by dissolving 100 mg tropolone in 100 mL toluene. 
5

To prepare the 1 M sulfuric acid solution, dilute 5.6 mL concentrated sulfuric acid with 

water to 100 mL final volume.

IV. Materials:

o 15-mL Polypropylene centrifuge tubes with screw cap. VWR Cat. # 21008-089 or 

equivalent

o Centrifuge capable of at least 2400 RPM

o Disposable Pasteur pipettes, 14.6 cm (53⁄4 in) & 22.9 cm (9 in)

o ~8-mL Test or culture tubes, screw tops with PFTE-lined caps

o 40-mL VOA glass vials, caps to fit with holes and PFTE septa

o GC-MS capable of selected ion monitoring with autosampler and data collection 

system

o Microliter syringes for making standard solutions and GC injections

o 5-mL Glass volumetric flasks

o 1-5-mL Adjustable pipettor with tips

o Glass wool

o Vortex mixer

o Tumbler for centrifuge tubes, approximately 20 RPM

V. Analysis:

All of the method development was performed on an HP 5890 Gas Chromatograph (GC) 

coupled to an HP 5972 Mass Selective Detector and 7673B autosampler. The column used was 30 

m x 0.32 mm ID with a 0.5 μm film DB-5ms. The mass spectrometer used electron impact 

ionization and was operated in the selected ion monitoring (SIM) mode. The following ions were 

monitored: 178.9, 234.9, 262.9, and 290.9. These were determined from the total ion scans of 

individual derivatized analytes (see Figures 1-3 below). The ions chosen were xxx.9 because tin 

and its isotopes have a negative mass defect of approximately 0.1 amu. Consequently, the masses 

(m/z) monitored have the units xxx.9 amu. For quantitation of the three analytes, all four ions were 

used to determine the peak in the chromatogram. Peak areas were used for quantitation.

Two microliters were injected in a 230 °C injector, splitless for 0.75 minutes. The initial 

oven temperature was 75 °C, held for one minute and then ramped to 225 °C at 12 °C/min. The 

final temperature was held for 5 minutes.
6

Experimentally obtained total ion spectra for the three butyltin derivatives are displayed in 

Figures 1-3. Following the spectra in Figure 4 is a typical chromatogram of all three derivatives in 

a mix.

Figure 1. Mass Spectrum of Butyltin Trichloride Derivative: Butyltriethyltin.
7

Figure 2. Mass Spectrum of Dibutyltin Dichloride Derivative: Dibutyldiethyltin.

Figure 3. Mass Spectrum of Tributyltin Chloride Derivative: Tributylethyltin.
8

Figure 4. Chromatogram of the Three Butyltin Derivatives.

During method development, experimental conditions and parameters were evaluated that do not 

appear in the final version of the method. Data are presented from these experiments in the following 

sections. This chronological presentation has led to confusion on the part of some readers. To go directly to 

the experimental conditions and evaluation data found in the method, please click the appropriate 

following links: Final procedure, LOD/LOQ determination, Recoveries at various concentration levels, 

precision and accuracy, long-term storage.
9

VI. Method Development Experiments:

A. Sodium Tetraethylborate in situ Derivatization:

A sodium tetraethylborate derivatization protocol has been employed in methods for chlorinated 

alkyl tins in air [22, 28, 29] as well as by a number of researchers quantifying organotin compounds in 

sediment and biota [1, 3, 5-8, 10, 13]. Rapsomanikis et al. used an in situ aqueous ethylation to analyze 

lead and methyllead [23]. Since in situ procedures were successfully used to prepare lead and tin 

compounds for analysis in aqueous or biological samples using aqueous sodium tetraethylborate, this 

procedure was considered first. To improve recovery of the derivatized alkyl tin, the final extraction step 

was repeated. Due to the limited volume of sample available, a five mL aliquot was used for derivatization.

Five mL urine was placed in a 15-mL centrifuge tube. Three mL of a pH 4 buffer was added plus 

one mL of 1% sodium tetraethylborate solution in water. The tube was capped, mixed, and allowed to 

stand for at least 30 minutes. To extract the alkyl tin compounds, 1.2 mL hexane was added and vortexed 

for 30 seconds. The tube was then centrifuged for 10 minutes and the hexane layer withdrawn and placed 

in a 5-mL volumetric flask. The hexane extraction of the sample was repeated two more times with the 

extracts added to the 5-mL volumetric flask. After the last extraction, the sample was brought to volume 

with additional hexane and mixed.

Total tin had been analyzed in urine samples previously at DataChem Laboratories (DCL) by ICPMS. Total tin concentrations were found to be quite low, typically in the 5-50 μg/L (as Sn) range. Analysis 

of butyltin trichloride in air samples at DCL on OVS-2 tubes using sodium tetraethylborate derivatization 

followed by quantification by GC-FPD in the tin mode with cool on-column injection gave a limit of 

detection (LOD) of 2-5 μg butyltin trichloride per 5-mL sample. This would compare to an LOD of 

approximately 200 μg/L as Sn, which would be too high for the GC-FPD to be the instrument of choice for 

the vast majority of samples. Since the cool on-column injector is not necessary for alkyltins other than to 
10

increase the amount of sample on column, GC-MS in the SIM mode was used. With either derivatization 

reagent, sodium tetraethylborate or ethylmagnesium bromide, the compounds formed from the butyltin 

chlorides are the same, each chloride is replaced by an ethyl group. For example, the derivatization of 

butyltin trichloride would yield triethyl butyltin. No physical properties for these alkyltin derivatives could 

be located, nor were they commercially available for purchase. Consequently, the completeness of the 

reaction could not be determined.

Experiment 1. LOD/LOQ Determination:

Initial LOD/LOQ determinations were conducted by derivatizing a concentrated stock of the 

butyltin chlorides, then making serial dilutions followed by GC-MS analysis in the SIM mode. Peaks at 

the low end were manually re-integrated as needed. Peak areas were used to calculate the LOD and LOQ 

by Burkart's method [30]. Results were as follows:

Table 1. LOD/LOQ Determination Results

Analyte μg/5 mL sample 

LOD

μg/5 mL sample 

LOQ

μg/L as Sn

LOD

μg/L as Sn

LOQ

Tributyltin 

chloride

0.03 0.1 6 20

Dibutyltin 

dichloride

0.02 0.08 5 20

Butyltin 

trichloride

0.04 0.1 8 30

Experiment 2. Derivatization of Spiked Urine and Aqueous Standards with Sodium 

Tetraethylborate; Recovery Study:

Five mL urine samples, each from a different subject and previously determined by ICP-MS analysis to 

have no tin, were spiked at approximately 10X LOQ and 30X LOQ. Six replicates at each level were 

prepared as were tin spikes in deionized water bracketing the urine spike range. The aqueous spikes were 
11

to serve as standards for extraction recovery purposes. An additional spike was prepared in UriSub©

synthetic urine. This spike was at the same level as the second highest standard. Samples were derivatized 

as described above. During the extraction step, it was noted that several urine samples had emulsions that 

would not clear. Some were so thick the tube could be upended and the emulsion acted as a cap on the 

liquid. Adding several hundred milligrams of sodium sulfate, mixing, and centrifuging the samples helped 

to clear these emulsions. Results are summarized below. Concentrations were determined using a 

calibration curve prepared from the aqueous spikes and concentrations were calculated using the response 

factor determined from the single spike in UriSub© synthetic urine.

Table 2a. Recovery Study Results (Results using the Aqueous Spike Calibration Curve) (n=6)

Analyte 10X LOQ

Result Avg. 

% Recovery

10X LOQ

Result

% RSD

30X LOQ

Result Avg. % 

Recovery

30X LOQ

Result

% RSD

Tributyltin 

chloride

83.6 7.6 84.0 4.2

Dibutyltin 

dichloride

85.4 8.1 84.7 4.2

Butyltin 

trichloride

82.5 10.8 85.4 3.3

Table 2b. Recovery Study Results (Results using the UriSub© Synthetic Urine Response Factor )

Analyte 10X LOQ

Result Avg. 

% Recovery

10X LOQ

Result

% RSD

30X LOQ

Result Avg. % 

Recovery

30X LOQ

Result

% RSD

Tributyltin 

chloride

85.6 8.5 94.2 4.5

Dibutyltin 

dichloride

90.7 9.1 98.5 4.4

Butyltin 

trichloride

90.2 11.1 98.4 3.6
12

Conclusions Concerning Sodium Tetraethylborate in situ Derivatization:

The % RSD at 10X LOQ was a factor of two to three times the % RSD at 30X LOQ. While 

experiments at 3X LOQ were not conducted, the concern was at that level the method would fail. Noted

too was the fact that apparent recoveries were higher when quantitating using the synthetic urine response 

factor than when quantitating against standards prepared from aqueous spikes. It was decided to try the 

tropolone extraction protocol instead of the in situ derivatization to see if recoveries and precision at lower 

levels could be improved.

B. Derivatization with Ethylmagnesium Bromide Following Tropolone Extraction:

Tropolone (2-hydroxy-2,4,6-cycloheptatrienone) has been used by a number of researchers to 

complex butyltin chlorides in a variety of polar matrices to allow extraction into a non-polar solvent [5-9, 

12, 18, 20, 21, 26, 27]. Derivatization is typically done by employing a Grignard reagent, although sodium 

tetraethylborate can be used [5-7]. Chau et al., with an emphasis on extracting monobutyltin trichloride, 

felt toluene gave the best recoveries [9]. For the next series of experiments, tropolone in toluene was used 

to extract the butyltin chlorides followed by derivatization with ethylmagnesium bromide as the Grignard 

reagent. The procedure used was based on the procedures outlined in the journal articles.

A number of experiments were performed to test various aspects of the tentative protocol before the 

final procedure was settled on. These were either suggested by the literature or deemed necessary to 

provide the best recoveries.

In the experiments described below, 15-mL centrifuge tubes were prepared containing 5 mL urine 

previously determined at DCL to contain no tin. The source of the urine is described for each experiment 

and could be either pooled urine or urine from different subjects. The tubes were spiked with the 

previously prepared tin mix described above at a level of 10X LOQ.
13

Experiment 1. Buffers: Three urine samples, known to contain no tin, were pooled.

From this supply, six spiked tubes and a blank were prepared. These tubes tested the effectiveness of 

different buffers. With the sodium tetraethylborate derivatization, the reaction was carried out at pH 4.0 -

4.5. A pH of about 2 was recommended for Grignard reactions. Both the pH 4 acetate buffer and newly 

prepared citrate buffers were tried at different pHs.

Three citric acid/sodium citrate buffers were prepared. Amounts listed in Table 3 below are grams 

added per liter of water.

Table 3. Buffer Composition

Buffer ~pH 2 ~pH 3 ~pH 4

Citric acid monohydrate 20.544 17.96 13.115

Sodium citrate dihydrate 0.652 4.265 11.051

In all cases, 3 mL buffer was added to the 5 mL spiked urine. Samples were then extracted and 

derivatized with Grignard reagent as described above. Peak areas are tabulated in Table 4.

Table 4: Results for Buffers

Sample type Peak area Butyltin 

Trichloride

Peak area Dibutyltin 

Dichloride

Peak area Tributyltin 

Chloride

pH 4 Acetate buffer -

tropolone extract

7728 4642 6440

pH 4 Citrate buffer -

tropolone extract

20866 9486 12061

pH 3 Citrate buffer -

tropolone extract

21916 9625 12492

pH 2 Citrate buffer -

tropolone extract

21389 9284 12520

The highest peak areas were obtained for both the pH 2 & pH 3citrate buffers. The pH 2 buffer was 

selected for use in the method. No tin compounds were observed in the blank.

Experiment 2. Reproducibility Experiment: Three sets of three spiked replicate samples were 
14

prepared from three different NIOSH supplied urine samples. These three sets were prepared and analyzed 

the same way to see how reproducible results are. Additionally, a set of three replicate samples containing 

pooled urine from the buffer experiment above were analyzed. Peak areas for the four sets of samples are 

averaged and presented in Table 5.

Table 5. Results for Reproducibility Experiment

Urine source Butyltin 

Trichloride avg 

peak area

Butyltin 

Trichloride

%RSD

Dibutyltin 

dichloride avg 

peak area

Dibutyltin 

dichloride

%RSD

Tributyltin 

chloride avg 

peak area

Tributyltin 

chloride

%RSD

NIOSH 12-6-B 24654 0.45 10198 0.90 14189 3.31

NIOSH 12-5-B 26832 0.78 9127 2.46 14055 0.55

NIOSH 6-5-B 24656 2.62 10044 1.82 13901 1.21

Pooled 2al 22216 3.23 9724 4.06 12831 2.54

Similar peak areas were observed for all sets of samples with the largest variation in average areas 

with dibutyltin dichloride, approximately 9%. Overall, this was not viewed as a significant problem.

Experiment 3. Extraction and Cleanup Experiments: The amount of tin extracted from the 

urine matrix by the tropolone-toluene extraction solution was tested. The first tropolone extract from four 

spiked samples was combined, derivatized and analyzed; the second extraction was similarly prepared and 

analyzed.

A number of journal articles recommended a cleanup procedure before analysis [2, 4, 6, 8, 9, 12, 

18, 21]. Florisil and alumina cleanups were tried on aliquots of the combined first and second extractions.

Extraction and Cleanup Experiment Results: The efficiency of the first extraction was 

determined by dividing the peak area of the first extract analysis by the sum of the areas for both extracts. 

For the cleanup experiment, 1.5 mL aliquots of the first and second extracts were each passed through a 1-
15

cm column of either florisil, alumina, or sodium sulfate in a 14.6 cm (53⁄4 in) Pasteur pipette prior to 

analysis. The column was rinsed with small portions of toluene and the volume brought to 2 mL. Peak 

areas for each analyte are tabulated with the cleanup procedure used.

Table 6. Second Extraction and Sample Cleanup Results

Sample type/Cleanup Step Butyltin Trichloride Dibutyltin Dichloride Tributyltin Chloride

First extract as % of total 

area (average)

87% 89% 82%

First extract peak areaflorisil

51077 16418 26148

First extract peak area -

alumina

57462 18861 28385

First extract peak area -

sodium sulfate

60634 19900 29599

Second extract peak area -

florisil

8117 2217 6323

Second extract peak area -

alumina

8652 2249 5410

Second extract peak area -

sodium sulfate

8737 2219 6781

Extraction and Cleanup Experiment Conclusions: The efficiency of the first extraction was 

overall approximately 86%. The second extraction was believed necessary because of the low butyltin

concentrations expected in the field samples. Alumina appeared to be a better cleanup media than florisil 

as evidenced by the slightly higher peak areas for the alumina aliquot. To eliminate any traces of water 

prior to analysis, a small quantity of sodium sulfate will be used in addition. The sodium sulfate did not 

seem to have a detrimental effect of the analysis results.

Experiment 4. Derivatization Kinetics: Fifteen mL of toluene-tropolone was spiked with butyltin 

chlorides and mixed thoroughly. To this, 1.25 mL ethylmagnesium bromide solution was added and 

vortexed. At timed intervals, 3-mL aliquots were removed and transferred to another tube containing one 

mL sulfuric acid solution to quench the reaction. The alkyltins were subsequently analyzed. 
16

Derivatization Kinetics Results: Peak areas vs. time of reaction quenching are shown in graphic 

form in Figure 5 and in tabular form in Table 7.

Figure 5. Butyltin Kinetics

Table 7. Tabulated Peak Areas for Reaction Kinetics

Time (minutes) Peak area Butyltin 

Trichloride

Peak area Dibutyltin 

Dichloride

Peak area Tributyltin 

Chloride

3 71304 85909 47553

15 70850 85947 47670

30 71345 88264 48258

45 72396 87604 48034

60 72353 88762 48682
17

Derivatization Kinetics Conclusions:

The reaction occurs very quickly and the reaction products appear stable in the sulfuric acid 

environment. A derivatization time of 15-20 minutes at a minimum will be adequate.

Longer times are not a detriment.

VII. Final Procedure:

Incorporating the results of these experiments, the final experimental protocol for the remainder of 

the method development and field sample analysis was as follows.

Thaw the urine samples. Place five mL of the urine sample in a 15-mL polypropylene centrifuge 

tube. Add three mL of ~pH 2.3 citric acid-sodium citrate buffer, 1.5 mL 0.1 % tropolone in toluene 

solution, and about 350 mg anhydrous sodium sulfate. Some urine samples can form emulsions during 

tumbling that are difficult to break down. For this reason, the samples should have the sodium sulfate 

added prior to tumbling at about 20 rpm for one hour. This is followed by centrifuging for at least 10 

minutes at 2400 rpm (1050 G). The upper toluene layer is transferred to an 8-mL glass culture tube with a 

PTFE-lined cap. An additional tropolone extraction procedure is conducted on the urine sample and the 

extracts combined. To the combined extracts, 350 mg anhydrous sodium sulfate is added to remove any of 

the aqueous phase that may have been inadvertently transferred and to dry the toluene. The dried sample is 

decanted into a second 8-mL glass culture tube with a PTFE-lined cap. The sodium sulfate residue in the 

first tube is rinsed twice with a small (~300 μL) quantity of toluene which is then combined with the dried 

extract in the second tube. A 250 μL quantity of the ethylmagnesium bromide solution is added to the 

toluene, mixed, and the mixture allowed to react for 15-20 minutes at a minimum. After the allotted 

reaction time, 1 mL of 1 M sulfuric acid is added to quench the remaining ethylmagnesium bromide and 

the tube is vortexed for approximately 30 seconds. After the layers separate, the top toluene layer is eluted 

through a clean-up column that is prepared in a 14.6 cm (53⁄4") disposable Pasteur pipette. The pipette
18

contains, in order from bottom to top: 1) a glass wool plug; 2) alumina, acid, Brockman activity I, 80-200 

mesh, enough to form a column of approximately 1 cm and; 3) ~100 mg of anhydrous sodium sulfate. The 

eluate is collected in a 5-mL volumetric flask. The tube with the sulfuric acid solution is rinsed several 

times with small amounts of toluene and the rinses eluted through the clean-up column. The remaining 

sample is flushed from the column by adding small portions of toluene to the top of the column. The final 

volume is adjusted to 5.0 mL with toluene as needed. Analysis is by the instrument conditions described 

previously.

VIII. Limit of Detection and Limit of Quantitation Determination for Method 

Spiking Levels:

The LOD and LOQ were determined by spiking 5 mL of urine in 15-mL centrifuge tubes with 

known concentrations of the three butyltin chlorides. A mixed standard was prepared as follows; the 

solvent used in all cases was 1% acetic acid in acetonitrile. For tributyltin chloride (96%, d = 1.200 

mg/μL), 10 μL were diluted in 10 mL to give a concentration of 1.152 μg/μL. For dibutyltin dichloride 

(96%), 16.05 mg were dissolved in 10 mL giving a concentration of 1.54 μg/μL. For butyltin trichloride 

(95%, d = 1.693 mg/μL), 10 μL were diluted in 10 mL to give a concentration of 1.608 μg/μL.

In previous work with these particular chemicals, it was found that dibutyltin dichloride was 

contaminated with butyltin trichloride. The concentration of butyltin trichloride was determined in the 

dibutyltin dichloride by peak area determination against a separate butyltin trichloride series of standards 

and found to be 0.04987 μg butyltin trichloride per 1 μg dibutyltin dichloride.

Table 8. Stock Standard Mix Concentrations

Analyte μg/μL Volume (μL) Final Volume 

(mL)

Final Conc. 

(μg/μL)

Tributyltin chloride 1.152 17.5 5 0.004032

Dibutyltin dichloride 1.54 14 5 0.004312

Butyltin trichloride 1.608 10 5 0.003431*

* includes contribution by dibutyltin contaminant.
19

Microliter amounts of the solution were spiked into 5 mL urine according to the 

following schedule:

Table 9. Working Standard Spiking Schedule (Concentration in μg/ 5 mL Sample)

Standard Spiked Volume 

(μL)

Butyltin 

Trichloride 

Concentration

Dibutyltin 

Dichloride 

Concentration

Tributyltin 

Chloride 

Concentration

1 250 0.85775 1.078 1.008

2 175 0.600425 0.7546 0.7056

3 100 0.3431 0.4312 0.4032

4 50 0.1716 0.2156 0.2016

5 24 0.085775 0.1078 0.1008

6 10 0.03431 0.04312 0.04032

7 5 0.01716 0.02156 0.02016

8 2 0.006862 0.008624 0.008064

Spiked samples were extracted with toluene-tropolone and then derivatized with ethylmagnesium 

bromide followed by the column cleanup as described in the previously described procedure. An aliquot of 

each sample was transferred to a GC vial for analysis by GC-MS in the SIM mode. Peak areas for butyltin 

and dibutyltin were tabulated and the LOD/LOQ determined by Burkart’s method [30]. An interfering 

peak was observed which prevented accurate quantitation of the tributyltin peak. This peak was composed 

of the m/z 179 ion. This had not been noticed previously because the LOD/LOQ was determined by a 

derivatization of a high standard followed by serial dilution of this stock. Additionally, sodium 

tetraethylborate was used instead of the ethylmagnesium bromide. It is unknown if this had an effect or 

not. Monitoring the m/z 179 ion was stopped prior to the retention time of the tributyltin peak. This seemed 

to solve the problem and allow good quantitation of the tributyltin peak in later analyses. This would have 

also required the reanalysis of the LOD/LOQ standards to determine the LOD and LOQ of tributyltin 

chloride. For further method development purposes, the LOD and LOQ were estimated for this compound. 

It should be noted that LODs/LOQs for this procedure are lower by about half than LOQs for the sodium 

tetraethylborate derivatization. The LODs were determined to be 0.01 μg/5 mL for tributyltin chloride 
20

(estimated), 0.02 μg/5 mL for dibutyltin dichloride, and 0.01 μg/5 mL for butyltin trichloride. Spiking 

levels for the method development were then determined to be:

Table 10. Method Development Urine Spiking Levels (Spiking Levels in μg/5 mL Sample)

Analyte LOQ 3X LOQ 10X LOQ 30X LOQ 100X LOQ

Tributyltin chloride 0.05* 0.15 0.5 1.5 5

Dibutyltin dichloride 0.06 0.18 0.6 1.8 6

Butyltin trichloride 0.04 0.12 0.4 1.2 4

*Estimated LOQ

IX. Extraction Efficiency at 3X, 10X, 30X, and 100X LOQ:

A new mix of analytes based on the previously determined LOD/LOQ was prepared from the 

concentrated stocks as described below:

Table 11. Extraction Efficiency Spiking Mix

Analyte μg/μL Volume (μL) Final Volume 

(mL)

Final Conc. 

(μg/μL)

Tributyltin chloride 1.152 110 5 0.025344

Dibutyltin dichloride 1.54 98 5 0.030184

Butyltin trichloride 1.608 58 5 0.020158*

* includes contribution by dibutyltin contaminant.

Aliquots of this solution were spiked into 5 mL urine in 15-mL centrifuge tubes at the 

four spiking levels. Six replicate samples were prepared at each level.

Table 12. Target Concentrations (Concentration Levels in μg/ 5 mL Sample)

LOQ level Spiked Volume 

(μL)

Butyltin 

Trichloride 

Concentration

Dibutyltin 

Dichloride 

Concentration

Tributyltin 

Chloride 

Concentration

100 X 200 4.03156 6.0368 5.0688

30X 60 1.20947 1.8110 1.5206

10X 20 0.40316 0.6037 0.5069

3X 6 0.12095 031811 0.1521
21

Samples were refrigerated overnight and extracted the following day. An aliquot of each 

derivatized sample was transferred to a GC vial for analysis by GC-MS. Peak areas for all analytes were 

tabulated and concentrations determined using calibration curves made from analytes in spiked urine. A 

summary of the recovery data is shown in Table 13.

Table 13. Recovery Summary

LOQ Level Butyltin 

Trichloride avg 

recovery

Butyltin 

Trichloride

%RSD

Dibutyltin 

dichloride avg 

recovery

Dibutyltin 

dichloride

%RSD

Tributyltin 

chloride avg 

recovery

Tributyltin 

chloride

%RSD

100X 106.1 1.75 91.6 1.24 95.9 0.97

30X 109.6 6.28 88.1 2.55 94.5 2.78

10X 105.9 4.22 93.9 1.61 94.2 1.96

3X 102.8 4.14 90.1 3.5 95.1 2.01

All data are presented in Table 14.
22

Table 14. Extraction Efficiency at 3X, 10X, 30X, and 100X LOQ
23

X. Precision and Accuracy: [31]

Butyltin Trichloride:

When all values are used, the Chi2 value was found to be 5.9304, the overall precision (Ŝrt) 

was 0.04114 and the bias was 0.06251 (see Appendix 1 detailing results for all cases). Accuracy was 

calculated to be 13.02% from these values.

Dibutyltin Dichloride:

When all values are used, the Chi2 value was found to be 6.1235, the overall precision (Ŝrt) 

was 0.02656 and the bias was -0.09108 (see Appendix 2 detailing results for all cases). Accuracy 

was calculated to be 13.48% from these values.

Tributyltin Chloride:

When all values are used, the Chi2 value was found to be 4.6069, the overall precision (Ŝrt) 

was 0.02150 and the bias was -0.05083 (see Appendix 3 detailing results for all cases). Accuracy 

was calculated to be 8.62% from these values.

XI. Long Term Storage:

A long term storage study was done by spiking 5 mL aliquots of urine with all three analytes 

at 10X LOQ. That level was chosen because most of the butyltin trichloride found in urine samples 

collected for a NIOSH study was close to this concentration. Since the urine samples had been stored 

frozen for an extended period of time, the storage study was conducted for ten months with the 

samples frozen at -20 °C. During the course of the study, samples were removed, thawed, extracted, 

derivatized, and analyzed against freshly spiked urine samples. The unspiked urine used for 

standards had been frozen with the spiked samples and was spiked prior to sample preparation.

To determine the effects, if any, on the butyltin recoveries due to the use of preserving agents, 

eight tubes spiked at 10X LOQ were prepared with: 1) ascorbic acid, 100 mg/5 mL aliquot; four 
24

tubes and 2) nitric acid, 200 μL/5 mL aliquot; four tubes. Two each of the two preserved sets were 

prepared and analyzed with the 127 and 315 day storage samples.

Tables 15a-c give a summary of the storage study. Tables 16-18 give the complete data set 

for each of the three analytes. Figure 6 is a graphical representation of the data for all three analytes 

while no preservative was being used.

Table 15a. Long Term Storage* Recovery Summaries (recoveries as % ± std deviation)

Analyte Target 

(μg/5mL)

Day 1 Day 7 Day 32 Day 127 Day 315

Tributyltin chloride 0.5069 94.5±3.7 98.1±2.4 93.5±1.0 111.6±3.6 97.4±8.5

Dibutyltin dichloride 0.5982 99.6±2.6 103.6±0.5 100.3±1.2 107.8±2.0 92.9±1.9

Butyltin trichloride 0.3977 95.8±2.3 104.0±1.5 97.7±1.6 103.6±3.6 96.1±3.6

*samples unpreserved

Table 15b. Long Term Storage* Recovery Summaries (recoveries as %)

Analyte Target 

(μg/5mL)

Day 127 Day 315

Tributyltin chloride 0.5069 115.6 97.4

Dibutyltin dichloride 0.5982 103.6 92.9

Butyltin trichloride 0.3977 110.6 96.1

*samples ascorbic acid preserved

Table 15c. Long Term Storage* Recovery Summaries (recoveries as %)

Analyte Target 

(μg/5mL)

Day 127 Day 315

Tributyltin chloride 0.5069 115.1 87.5

Dibutyltin dichloride 0.5982 120 91.8

Butyltin trichloride 0.3977 116.3 90.2

*samples nitric acid preserved
25

Table 16. Long Term Storage: All Data; Butyltin Trichloride
26

Table 17. Long Term Storage: All Data; Dibutyltin Dichloride
27

Table 18. Long Term Storage: All Data; Tributyltin Chloride
28

Figure 6. Butyltin Long-Term Storage Results

XII. Conclusions:

The butyltin chloride analysis protocol involving complexation and extraction by tropolonetoluene followed by derivatization with ethylmagnesium bromide and GC-MS in the SIM mode has 

been demonstrated to be both a precise and accurate [31] method of determining butyltins in urine,

with limits of detection low enough to detect alkyltin concentrations in urine that would be 

typically found following exposure to butyltin chlorides in an industrial setting. The analytes have 

been found to be stable for at least 315 days, frozen. No sample preservation other than freezing 

was deemed necessary.
29

XIII. References:

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phenyltin compounds in biological material by gas chromatography with flame 

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sediment using gas chromatography-atomic absorption spectrometry: comparison of 

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4. Abalos M., Bayona JM, Compañó R, Granados M, Leal C, Prat MD [1997]. Analytical 

procedures for the determination of organotin compounds in sediment and biota: a critical 

review. J Chrom A 788:1-49.

5. Ashby JR, Craig PJ [1989]. New method for the production of volatile organometallic 

species for analysis from the environment; some butyl tin levels in U.K. sediments. Sci 

Total Environ 78:219-232

6. Ceulemans M, Adams FC [1995]. Evaluation of sample preparation methods for 

organotin speciation analysis in sediments - focus on monobutyltin extraction. Anal Chim 

Acta 317:161-170.

7. Ceulemans M, Slaets S, Adams FC [1998]. Speciation of organotin in environmental 

sediment samples. Talanta 46:395-405.

8. Chau YK, Yang F, Brown M [1997]. Evaluation of derivatization techniques for the 

analysis of organotin compounds in biological tissue. Anal Chim Acta 338:51-55.

9. Chau YK, Yang F, Maguire RJ [1996]. Improvement of extraction recovery forthe 

monobutyltin species from sediment. Anal Chim Acta 320:165-169.

10. Rapsomanikis S [1994]. Derivatization by ethylation with sodium tetraethylborate for the 

speciation of metals and organometallics in environmental samples: a review. Analyst 

119:1429-1439.
30

11. Iwai H, Wada O, Arakawa Y [1981]. Determination of tri-, di-, and monobutyltin and 

inorganic tin in biological materials and some aspects of their metabolism in rats. J Anal 

Tox 5:300-306.

12. Müller M [1987]. Comprehensive trace level determination of organotin compounds in 

environmental samples using high-resolution gas chromatography with flame photometric 

detection. Anal Chem 59:617-623.

13. Looser PW, Berg M, Fent K, Muhlemann J, Schwarzenbach R.P [2000]. Phenyl- and 

butyltin analysis in small biological samples by cold methanolic digestion and GC/MS. 

Anal Chem 72:5136-5141.

14. Kimbrough RD [1976]. Toxicity and health effects of selected organotin compounds:A 

eeview. Env Health Perspect 14:51-56.

15. Syracuse Research Corporation [2003]. Toxicological Profile for Tin and Compounds. 

Syracuse Research Corporation, CDC contract # 205-1999-00024.

16. Boyer I J[1989] Toxicity of dibutyltin, tributyltin and other organotin compounds to 

humans and to experimental animals Tox 55(3):253-298.

17. Life Systems, Inc [1992]. Toxicological profile for tin and compounds. Under contract to 

Agency for Toxic Substances and Disease Registry.

18. Gui-bin J, Qun-fang Z, Bin H, Liu J [2000]. Speciation analysis of organotin compounds 

in lard poisoning accident in Jiangxi Province, China. Sci in China 43:531-539.

19. Gitlitz MH, Dirkx R, Russo DA [1992]. Letting light in; keeping heat out. Chemtech

22:552-556.

20. Dyne D, Chana BS, Smith NJ, Cocker J [1991]. Determination of triutyltin oxide and its 

di- and monobutyl metabolites in urine using combined gas chromatography-atomic 

absorption spectrometry. Anal Chim Acta 246:351-357.

21. Gui-bin J, Qun-fang Z, Bin H [2000]. Tin compounds and major trace metal elements in 

organotin-poisoned patient’s urine and blood measured by gas chromatography with 

flame photometric detector and inductively coupled plasma-mass spectrometry. Bull 

Environ Contam Tox 65:277-284.

22. Boraiko C, Yoder R, Cooper J, Lieckfield Jr. R, Remski M [2004]. Sampling and analysis 

of organotin compounds in air using gas chromatography and flame photometric 

detection. J Occup Environ Hyg 1:50-56.

23. Rapsomanikis S, Donard OFX, Weber JH [1986]. Speciation of lead and methyllead ions
31

in water by chromatography/atomic absorption spectrometry after ethylation with sodium 

tetraethylborate. Anal Chem 58:35-38.

24. Clark S, Ashby J, Craig PJ [1987]. On-column hydride generation method for the 

production of volatile hydrides of tin, arsenic, and antimony for the gas chromatographic 

analysis of dilute solutions. Analyst 112:1781-1782.

25. Jiang GB, Liu JY [2000]. Determination of butyltin compounds in aqueous samples by 

gas chromatography with flame photometric detector and headspace solid-phase 

microextraction after in-situ hydride derivatization. Anal Sci 16:585-588.

26. Plzák Z, Polanská M, Suchánek M [1995]. Identification and determination of butyltin 

compounds in water by ion trap gas chromatography-mass spectrometry after conversion 

to methyl or hydride derivatives. J Chrom A 699:241-252.

27. Meinema HA, Burger-Wiersma T, Versluis-de Haan G, Gevers EC [1978]. 

Determination of trace amounts of butyltin compounds in aqueous systems by gas 

chromatography/mass spectrometry. Environ Sci Tech 12:288-293.

28. NIOSH [1994]. Methyltin Chlorides:Method 5526 In: Eller PM, Cassinelli ME, eds. 

NIOSH manual of analytical methods, 4th ed. Cincinnati, OH: U.S. Department of Health 

and Human Services, Centers for Disease Control and Prevention, National Institute for 

Occupational Safety and Health, DHHS (NIOSH) Publication No. 94-113.

29. ORTEP [1995]. Method: Butyltin chlorides in air. Bergkamen, Germany: Organotin 

Environmental Programme Association.

30. Burkart JA [1986]. General procedures for limit of detection calculations in industrial 

hygiene chemistry laboratory. Appl Ind Hyg 1(3):153-155.

31. NIOSH [1995]. Guidelines for air and analytical method development and evaluation. By 

Kennedy ER, Fishbach TJ, Song R, Eller PM, Shulman, SA. Cincinnati, OH: U.S. 

Department of Health and Human Services, Centers for Disease Control and Prevention, 

National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 

95-117.
32

Appendix 1. Precision and Accuracy for Butyltin Trichloride
33

Appendix 2. Precision and Accuracy for Dibutyltin Dichloride
34

Appendix 3. Precision and Accuracy for Tributyltin Chloride
35

Appendix 4

Review of User Check for NMAM Method 8320 (Butyltin trichloride in urine)

User check samples were prepared by a NIOSH researcher (Dr. Clayton B’Hymer) to be analyzed by 

ALS Environmental using draft NIOSH Method 8320. A total of 25 urine samples were prepared. The 

urine was obtained from volunteers at NIOSH and then combined and mixed into a single pool of urine 

from which all samples were prepared. The final volume of each sample was 20 mL. Five samples were 

left blank. Five samples were prepared containing each of the analytes at the levels shown in the 

following table.

Compound Level 1 (μg/5 mL) Level 2 (μg/5 mL) Level 3 (μg/5 mL) Level 4 (μg/5 mL)

Butyltin 

trichloride

0.128 0.250 12.5 60.5

Dibutyltin 

dichloride

0.121 0.237 11.85 57.5

Tributyltin 

chloride

0.123 0.240 12.0 58.5

The samples were shipped frozen to ALS Environmental on October 27, 2015 and arrived there the next 

day. The samples were analyzed on November 16, 2015. No significant deviations from the analytical 

procedure in NIOSH Method 8320 were noted.

For this analysis, the Reporting Limit (RL, which is equivalent to the limit of quantitation, LOQ) was 

determined by ALS to be 0.012 μg/5 mL for all three compounds. As mentioned above, the spike levels 

ranged from 0.121 to 60.5 μg/5 mL, which is 10 to 5000 times the RL and fall within the range of the 

calibration curve. The calibration curve covers concentrations from 0.012 to 120.0 μg/5 mL.

None of the butyltin chloride compounds was detected in the blank urines, which is to be expected. 

Summary tables for each analyte at each level are shown below and tables of data for all the samples can 

be found at the end of this report.

Compound Target conc. 

(μg/5 mL)

Average Recovery 

(%)

RSD (%)

Butyltin trichloride 0.128 79.2 4.9

Butyltin trichloride 0.250 83.5 5.8

Butyltin trichloride 12.5 90.2 4.0

Butyltin trichloride 60.5 92.7 3.8

Overall 86.4 7.6
36

Compound Target conc. (μg/5 

mL)

Average Recovery 

(%)

RSD (%)

Dibutyltin dichloride 0.121 68.8 7.1

Dibutyltin dichloride 0.237 74.3 1.9

Dibutyltin dichloride 11.85 80.7 6.1

Dibutyltin dichloride 57.5 76.0 5.7

Overall 74.9 7.7

Compound Target conc. (μg/5 

mL)

Average Recovery 

(%)

RSD (%)

Tributyltin chloride 0.123 54.2 8.9

Tributyltin chloride 0.240 56.1 5.0

Tributyltin chloride 12.0 72.0 5.3

Tributyltin chloride 58.5 78.3 3.0

Overall 65.1 17.0

The average recovery for butyltin trichloride is very near the ± 15% accuracy (± 20% at the lowest level) 

recommended for bioanalytical methods by the US Food and Drug Administration [1]. The relative 

standard deviation (RSD, which is a measure of precision) for all levels ranged from 3.8 to 5.8 per cent, 

which is also well within acceptable limits. The average recoveries for dibutyltin dichloride and 

tributyltin chloride are outside of the recommended criteria. In the case of tributyltin chloride, values of 

roughly 50% recovery were found at the lower two levels. The contract lab reported no difficulties 

understanding the draft method nor in setting it up or analyzing the User Check samples. The User 

Check laboratory followed the procedure and the method has been shown to have adequate precision 

and accuracy for butyltin trichloride while showing less than adequate precision and accuracy for 

dibutyltin dichloride and tributyltin chloride. Therefore, the method was rewritten as a single analyte 

method. Fortunately, butyltin trichloride is the most commonly used and occupationally relevant of 

these three butyltin chloride compounds. It is recommended that the method, NIOSH Method 8320 

(Butyltin trichloride in urine) be approved and accepted for inclusion in the NIOSH Manual of 

Analytical Methods.

Dale Shoemaker, PhD

Research Chemist

June 24, 2016

[1] U.S. Food and Drug Administration. “Guidance for Industry: Bioanalytical Method Validation.” 

US FDA, May 2001.
37

Data table for butyltin trichloride

Spike 

ID

Target conc 

(μg/5 mL)

Analyzed conc 

(μg/5 mL)

Recovery 

(%)

Avg

recovery Std. Dev. RSD

6 0 ND

9 0 ND

12 0 ND

19 0 ND

24 0 ND

4 0.128 0.10 78.91

5 0.128 0.10 77.34

10 0.128 0.11 85.94

11 0.128 0.10 77.34

20 0.128 0.10 76.56 79.22 3.85 4.86

3 0.25 0.23 91.20

7 0.25 0.20 81.60

8 0.25 0.20 80.40

17 0.25 0.21 85.20

22 0.25 0.20 79.20 83.52 4.84 5.80

2 12.5 11.8 94.40

14 12.5 10.6 84.80

18 12.5 11.4 91.20

21 12.5 11.5 92.00

23 12.5 11.1 88.80 90.24 3.64 4.03

1 60.5 57.6 95.21

13 60.5 53.2 87.93

15 60.5 57.4 94.88

16 60.5 54.7 90.41

25 60.5 57.4 94.88 92.66 3.30 3.57

Overall average 86.41

Std. Dev. 6.57

RSD 7.60
38

Data table for dibutyltin dichloride

Spike 

ID

Target conc

(μg/5 mL)

Analyzed conc 

(μg/5 mL)

Recovery 

(%)

Avg

recovery

Std. 

Dev. RSD

6 0 ND

9 0 ND

12 0 ND

19 0 ND

24 0 ND

4 0.121 0.08 63.64

5 0.121 0.08 64.46

10 0.121 0.09 75.21

11 0.121 0.08 68.60

20 0.121 0.09 71.90 68.76 4.90 7.13

3 0.237 0.18 75.53

7 0.237 0.17 72.57

8 0.237 0.17 73.00

17 0.237 0.18 74.68

22 0.237 0.18 75.53 74.26 1.40 1.88

2 11.85 9.4 79.24

14 11.85 8.6 72.83

18 11.85 9.8 82.70

21 11.85 10.0 84.39

23 11.85 10.0 84.39 80.71 4.88 6.05

1 57.5 41.7 72.52

13 57.5 42.0 73.04

15 57.5 46.5 80.87

16 57.5 42.0 73.04

25 57.5 46.3 80.52 76.00 4.29 5.65

Overall average 74.93

Std. Dev. 5.80

RSD 7.74
39

Data table for tributyltin chloride

Spike 

ID

Target conc 

(μg/5 mL)

Analyzed conc 

(μg/5 mL)

Recovery 

(%)

Avg

recovery

Std. 

Dev. RSD

6 0 ND

9 0 ND

12 0 ND

19 0 ND

24 0 ND

4 0.123 0.06 46.34

5 0.123 0.07 54.47

10 0.123 0.07 57.72

11 0.123 0.07 58.54

20 0.123 0.07 53.66 54.15 4.83 8.92

3 0.24 0.14 56.25

7 0.24 0.13 55.00

8 0.24 0.13 53.75

17 0.24 0.15 60.83

22 0.24 0.13 54.58 56.08 2.80 5.00

2 12 8.5 71.00

14 12 7.9 65.83

18 12 9.0 75.33

21 12 8.9 74.33

23 12 8.8 73.67 72.03 3.82 5.30

1 58.5 46.0 78.63

13 58.5 43.5 74.36

15 58.5 47.2 80.68

16 58.5 45.9 78.46

25 58.5 46.3 79.15 78.26 2.35 3.00

Overall average 65.13

Std. Dev. 11.04

RSD 16.96