Arsenic

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2010-03 to 2010-05

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

yes

Remarks:

conducted unter inert gas to exclude oxidative processes (based on experience with other metals)

Principles of method if other than guideline:

- Based on experience and in view of the poor solubility of other metal substances, it has been considered to conduct the test under inert gas (Argon) to exclude oxidative processes.
- Deviant to the study plan two vessels were set up in a parallel design at 20 ± 1.0 °C instead of 20 ± 0.5 °C. This deviation was regarded to be uncritical. Each vessel has been sampled several times instead of preparing and sampling one vessel at every point in time. This modification helps to avoid weighing errors.

GLP compliance:

yes (incl. QA statement)

Remarks:

2007-03-21

Type of method:

flask method

Water solubility:

10 610 µg/L

Temp.:

20 °C

pH:

>= 5.9 - <= 6.2

Remarks on result:

other: Mean result of dissolved As from two flasks and two time points (168 and 192h). The water solubility is expected to vary based on various parameters, such as particle size, surface area, loading and stirring time.

Preliminary test:

- Loading of 100 mg As in 1L: 267.9 µg/L As

- Loading of 100 mg As in 100 mL: 2014 µg/L As

The recovery of the certified reference material TMDA-70 was 101% and the recalibration sample exhibited 104%.

Main test:

Filtrated solutions were visually clear, and the absence of undissolved particles in the filtrates was proved by turbidity measurements .

The temperature of the water bath was held at 20.0 ± 0.5°C.

After adding the test substance, the pHs of all loaded test media were in the range of 5.8 – 6.5.

The temperature in the test flasks ranged from 20.5 – 20.8°C.

The O₂levels in the experimental setup at sampling times were very low (0.2 - < 0.1 ppm)

The pH of test solutions and blanks were measured after 24, 48, 72, 144, 168, 192, 216h. The method control blanks had relatively constant pH levels ranging from 5.9 – 6.5; the pHs of aqueous solutions of arsenic metal (grain size 2 – 15 mm) were in the range of pH 5.8 – 6.2.

Measured arsenic (III) concentrations (given in µg/L) in test samples

stirring time [h]	Dilution	mean As (III) conc. flask A [µg/L]	variation flask A [%]	mean As (III) conc. flask B [µg/L]	variation flask B [%]	mean As (III) conc. (all values) [µg/L]	variation mean both flasks [%]
24	1:30	4928±63	-	4368±122	-	4648±396	-
48	1:30	7271±68	48	6745±151	54	7008±372	51
72	1:30	7927±28	9	6872±37	2	7400±746	6
144	1:30	10881±131	37	8302±98	21	9592±1824	30
168	1:30	11694±83	8	8934±130	8	10314±1952	8
192	1:30	11985±238	3	9137±60	2	10561±2014	2

Measured arsenic (V) concentrations (given in mg/L) in test samples

stirring time [h]	Dilution	mean As (V) conc. flask A [µg/L]	variation flask A [%]	mean As (V) conc. flask B [µg/L]	variation flask B [%]	mean As (V) conc. (all values) [µg/L]	mean variation both flasks [%]
24	1:3	26.4±2.6	-	20.9±2.7	-	23.6±3.9	-
48	1:3	46.1±2.9	75	51.3±4.2	145	48.7±3.7	106
72	1:3	71.2±8.2	55	49.3±1.4	-4	60.3±15.5	24
144	1:3	69.3±12	-3	45.6±3.8	-8	57.5±16.8	-5
168	1:3	95.5±3.0	38	66.7±0.1	46	81.1±20.4	41
192	1:3	101±14.6	6	43.0±3.0	-36	72.2±41.3	-11

Measured total arsenic concentration (given in µg/L) in test samples

stirring time [h]	Dilution	total As conc. flask A [µg/L]	variation flask A [%]	total As conc. flask B [µg/L]	variation flask B [%]	mean total As conc. [µg/L]	variation mean both flasks [%]
24	1:50	4479	-	3891	-	4185±146	-
48	1:50	7115	59	6365	64	6740±530	61
72	1:100	8505	20	6447	1	7476±1455	11
144	1:100	10610	25	8176	27	9393±1721	26
168	1:100	11850	12	8717	7	10284±2215	9
192	1:100	12630	7	9239	6	10935±2398	6

Comparison of As (III), As (V) and total As in solution

	Stirring time
	24h	48h	72h	144h	168h	192h
As(III) conc. [µg/L] (mean from flask A+B)	4648 ± 396	7008 ± 372	7400 ± 746	9592 ± 1824	10314 ± 1952	10561 ± 2014
As(V) conc. [µg/L] (mean from flask A+B)	23.6 ± 3.9	48.7 ± 3.8	60.3 ± 15.5	57.5 ± 16.8	81.1 ± 20.4	72.2 ± 41.3
∑ As(III)+As(V)	4672	7057	7460	9649	10395	10633
total As conc. [µg/L] (mean from flask A+B)	4185 ± 416	6740 ± 530	7476 ± 1455	9393 ± 1721	10284 ± 2215	10935 ± 2398
∑ (As(III)+As(V)) / total As [%]	1.12	1.05	1.00	1.03	1.01	0.97
ratio As(III)/ As(V)	195	143	123	166	127	147

Test evaluation

A high variation in measured total arsenic concentrations were observed in samples taken after 24, 48, 72 and 144h (between 11 and 61%). After 168 and 192h the observed variation of amount of dissolved arsenic metal in measured samples was between 9 and 6% (below the limit of 15 % as required by the test guideline).In consequence, the applied equilibration times are considered to be sufficient and meet the requirements of the test guideline. Therefore, the water solubility of arsenic metal (grain size 2 – 15 mm) was determined using mean dissolved As concentrations (Flask A and B) as follows:

As (III) and As (V) were separated by solid phase extraction tubes followed by arsenic analysis. Total arsenic concentration was also determined by this analytical method.

Mean total As concentration after 168 and 192h (n = 2) = 10610 ± 460 µg/L, thus:

Water solubility of arsenic metal (grain size 2 – 15 mm) on the solved concentration of As: 10610 ± 460 µg/L (mean As conc.)

The measured As (III) concentrations showed higher variations between 24h, 48h, 72h and 144h samples than between 168h and 192h. In contrast, the As (V) concentration exhibited high variations in all measured samples:

                  As(III):                                                   As(V):

                  24h:    4648 ± 396 µg/L                 24h:        23.6 ± 3.9 µg/L

                  48h:    7008 ± 372 µg/L                   48h:        48.7 ± 3.7 µg/L

                  72h:    7400 ± 746 µg/L                   72h:        60.3 ± 15.5 µg/L

                  144h:  9592 ± 1824 µg/L               144h:      57.5 ± 16.8 µg/L

                  168h:  10314 ± 1952 µg/L              168h:      81.1 ± 20.4 µg/L

                  192h:  10561 ± 2014 µg/L             192h:      72.2 ± 41.3 µg/L

The amount of As (III) in solution was always considerably higher than As (V). After 24h, 48h, 72h, 144h, 168h and 192h the ratio As (III)/As (V) was 197, 144, 123, 167, 127 and 146, respectively. Consequently, only ca. 0.5 – 0.8 % of dissolved Arsenic were present as As (V).

Method validation summary ICP-OES/ICP-MS

Validation parameter	ICP-OES		ICP-MS
	results	comment	results	comment
selectivity	similar data with two different As wavelengths for ICP-OES method	no interferences due to test media observed	selectivity given by used isotope/mass	no interference due using He mode
linearity	applied calibration functions were linear	correlation coefficient (r) at least 0.9996	applied calibration functions were linear	correlation coefficient (r) at least 0.9992
limits of detection (LOD)	4.7 – 17 µg/L		0.08 – 1.98 µg/L
limits of quantification (LOQ)	15 - 55 µg/L		0.25 – 5.9 µg/L
method control blanks	below < LOD = < 4.7 - < 17µg/L	-	Below < LOD 0.08 - < 1.98 µg/L	-
accuracy and precision	mean recovery for TMDA-70:96 ± 9.6 % (n = 26)	corresponds to lower concentration range of samples (40.70 µg/L)	mean recovery of TM 26.3: 101 ± 9.8 % (n = 12)	corresponds to lower concentration range of As(V) in samples (7.9 µg/L)
trueness	mean recovery from fortification of samples: 101 ± 0.8 % (n = 6)	corresponds to concentration range of samples	-	-
repeatability	mean recovery for recalibration standard 100 µg/L:103 ± 3.9 % (n = 22)	corresponds to concentration range of samples	mean recovery for TMDA-70: 103 ± 6.1 % (n = 13)	corresponds to concentration range of As(V) in samples (40.7 µg/L)
repeatability	mean recovery from diluted CPI: 102 ± 1.3 % (n = 22)	corresponds to concentration range of samples	-	-
reproducibility	mean recovery for TMDA-70: 96 ± 9.6 % (n = 26)	for lower concentration range of samples (40.70 µg/L)	mean recovery for TMDA-70 and TM 26.3: 103 ± 6.1 % (n =13),101 ± 9.8 % (n = 12)	for lower and higher concentration in the range of As(V) in samples

Conclusions:

Interpretation of results (migrated information): slightly soluble (0.1-100 mg/L)
Under the conditions of this test (flask method; loading of 437,1 mg/L and 530.2 mg/L , flask A and B), the water solubility of arsenic metal (grain size 2 – 15 mm) at 20.0 ± 1.0°C was determined as
10610 ± 460 µg/L

(based on dissolved total As measured by ICP-OES, separated by filtration (0.2 µm) from undissolved test material).

The resulting solution pH was measured to be in the range of 5.9 – 6.2.

The concentrations of As (V) in solution were 20.9 – 101.4 µg/L and the concentrations of As (III) in solution ranged from 4368 – 11985 µg/L during the test. Almost all (99.2-99.5%) dissolved arsenic was present in the form of As (III).

Under the conditions of an experimental study (OECD TG 105), using a loading of ca. 0.5 g/L of granular As (2-15mm) , the solubility of arsenic metal has been determined to be ca. 10.6 mg/L after stirring for 8 days under an argon atmosphere to exclude oxidative processes. This is the mean result of dissolved As from two flasks and two time points (168 and 192h). However, the water solubility is expected to vary based on various parameters, such as particle size, surface area, loading and stirring time, and a single figure for a “saturation water solubility” cannot be given.

Reference 2

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2012-01-10 to 2012-09-26

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

The deviations of the guideline did not effect the results

Qualifier:

according to guideline

Guideline:

OECD Series on Testing and Assessment No. 29 (23-Jul-2001): Guidance document on transformation/dissolution of metals and metal compounds in aqueous media

Version / remarks:

2003

Deviations:

yes

Remarks:

reduced protocol: only one loading (1 mg/L) and a pH of 6 and 8 instead of a range from 5.5 to 8.5 was used.

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2011-02-07

Type of method:

other: transformation/ dissolution

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

300.3 µg/L

Element analysed:

As

Loading of aqueous phase:

1 mg/L

Incubation duration:

1 d

Test conditions:

pH 8

Remarks on result:

other: SD: 92.2 µg/L

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

231.7 µg/L

Element analysed:

As

Loading of aqueous phase:

1 mg/L

Incubation duration:

1 d

Test conditions:

pH 6

Remarks on result:

other: SD: 17.0 µg/L

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

663.2 µg/L

Element analysed:

As

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 8

Remarks on result:

other: SD: 285.3 µg/L

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

782.3 µg/L

Element analysed:

As

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 6

Remarks on result:

other: SD: 78.2 µg/L

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

741.6 µg/L

Element analysed:

As

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 6

Remarks on result:

other: SD: 55.0 µg/L

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

750.7 µg/L

Element analysed:

As

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 8

Remarks on result:

other: SD: 326.4 µg/L

Details on results:

Temperature:
During the 28 d of the test, the mean temperature was 21.7 ± 0.6 °C and in agreement with the OECD guidance document 29.

Solution pH and oxygen levels:
The solution pH of test media TM1 (pH 8) and TM1:20 (pH 6) loaded with the test item and of method blanks remained stable, i.e. 7.8 – 8.2 for the target pH of 8 and 5.8 – 6.2 for the target pH of 6, during the whole test.
Oxygen levels of all test solutions were in the range recommended by the OECD Test Guidance 29 during the test: above 70 % of oxygen saturation at 8.5 mg/L (70 % of 8.5 mg/L = 6 mg/L).

Analytical measurements
The total dissolved arsenic concentrations of method blanks were always below the respective limit of detection (LODs ranged from 4.92 µg/L to 9.01 µg/L).
The concentrations of As (III) and (V) species of method blanks were below the LOD or LOQ of the HPLC-ICP-MS system. Mean recoveries were calculated by comparing measured total arsenic concentrations and the corresponding sums of As (III) and (V) concentrations.
The LODs of ICP-OES measurements of As concentrations in test solutions and method blanks ranged from 4.92 to 10 µg/L with corresponding LOQs ranging from 16.4 to 33.3 µg/L. The LODs and LOQs of HPLC-ICP-MS measurements of As speciation in test solutions and method blanks ranged from 0.18 to 0.22 µg/L and from 0.66 to 0.78 µg/L for As (III); for As (V) LODs and LOQs range from 0.12 to 0.35 µg/L and from 0.45 to 1.26 µg/L, respectively.

Results:

The decrease of measured dissolved arsenic concentrations over time starting after 168 h at pH 8 and after 336 h at pH 6 might be explained with the dilution of the media during the test due to the sampling, i.e. replacement of sampled volumewith fresh media (i.e., 150 mL after 24 h and respectively 50 mL at every subsequent sampling) in accordance with the guidance document. However, accounting for the As removed by sampling, average amounts of 69.8 ± 33.5 % and 82.1 ± 9.7 % of the initial loading of 1 mg/L arsenic metal grains went into solution at pH 8 and pH 6 after 28 d, respectively. Recovery of total dissolved arsenic expressed as the sum of measured dissolved tri - and pentavalent arsenic species ranged from 93.1 to 115 %. The concentrations of dissolved As (total), As (III) and As (V) of replicate 1 and 2 over time are different from levels measured in the third replicate at pH 6 and pH 8 (i.e. vessel 3 at pH 8 and vessel 6 at pH 6). Over the course of the test, mainly trivalent arsenic species were detected in the majority of test solutions with the exception of predominantly pentavalent arsenic species in solutions from replicate 3 at pH 8 after 336 h until test end and at pH 6 after 96 h until test end. Only small differences (mainly of the same magnitude as SD and measurement uncertainty) between pH, temperature and O2 concentration of test solutions in vessels 1 and 2 to those of vessel 3 were observed. Further, all vessels were randomized on the laboratory shaker. Therefore, an experimental artifact can be excluded. The measured solution pH, temperature and oxygen levels meet the requirements of the OECD-Guidance document 29.

Measured As concentrations (target pH = 8)

Sample, sampling time	mean As conc. per vessel ± SD [µg/L]	mean As conc. all vessels ± SD [µg/L]	As(III) conc. [µg/L]	As (V) conc. [µg/L]#	mean ∑ As (III) + As (V) [µg/L]	recovery mean ∑ As (III) + As (V) related to mean As conc. all vessels [%]
1 2h	78.6 ± 0.6	59.5 ± 19.8	78.0	0.8	60.2 ± 21.7	101.5
2 2h	64.7 ± 2.5		64.8	0.7
3 2h	35.3 ± 1.3		35.8	0.6
1 6h	130.9 ± 0.8	105.2 ± 30.9	138.0	0.8	111.9 ± 36.8	106.3
2 6h	118.7 ± 0.6		126.0	0.9
3 6h	66.0 ± 1.3		69.1	0.8
1 24h	339.4 ± 25.2	300.3 ± 92.2	345.2	2.0	305.1± 101.0	101.7
2 24h	374.8 ± 36.3		373.8	4.4
3 24h	186.6 ± 24.3		188.1	1.8
1 96h	809.6 ± 1.1	670.0 ± 236.8	755.6	4.7	628.8 ± 261.2	93.1
2 96h	835.7 ± 2.7		794.4	3.7
3 96h	364.7 ± 2.8		323.5	4.4
1 168h	980.1 ± 13.5	750.7 ± 326.4	979.9	21.4	770.2 ± 372.8	102.7
2 168h	942.1 ± 4.3		959.9	9.4
3 168h	329.9 ± 1.7		263.6	76.5
1 336h	965.5 ± 1.7	738.0 ± 323.5	975.4	89.4	815.4 ± 408.9	109.7
2 336h	927.5 ± 13.5		1012.4	25.5
3 336h	321.0 ± 10.9		117.4	226.0
1 504h	916.5 ± 15.3	693.2 ± 302.6	813.0	184.8	760.4 ± 387.6	108.3
2 504h	858.9 ± 18.7		934.6	35.7
3 504h	304.2 ± 1.7		20.6	292.6
1 672h	866.0 ± 20.4	663.2 ± 285.3	652.2	323.5	746.1 ± 378.5	110.8
2 672h	827.9 ± 9.69		905.9	47.6
3 672h	295.9 ± 12.0		18.5	290.8

Measured As concentrations (target pH = 6)

Sample, Sampling time	mean As conc. per vessel ± SD [µg/L]	mean As conc. all vessels ± SD [µg/L]	As(III) conc. [µg/L]	As (V) conc. [µg/L]	mean ∑ As (III) + As (V) [µg/L]	recovery mean ∑ As (III) + As (V) related to mean As conc. all vessels [%]
4 2h	37.3 ± 0.3	35.7 ± 4.3	36.6	0.5	35.1 ± 5.3	98.0
5 2h	30.3 ± 0.3		28.5	0.5
6 2h	39.7 ± 0.1		38.6	0.5
4 6h	69.5 ± 1.6	67.8 ± 6.6	72.9	0.6	70.7 ± 8.5	104.2
5 6h	59.9 ± 0.3		60.7	0.5
6 6h	73.9 ± 2.7		76.8	0.8
4 24h	241.2 ± 0.9	231.7 ± 17.0	231.6	1.4	225.3 ± 18.2	97.2
5 24h	209.9 ± 1.6		203.3	1.1
6 24h	244.1 ± 0.8		236.6	1.7
4 96h	603.6 ± 6.1	558.8 ± 46.1	560.1	0.9	519.8 ± 44.1	93.1
5 96h	502.8 ± 7.6		473.3	<LOD (see 1)
6 96h	569.9 ± 4.0		424.6	100.5
4 168h	811.2 ± 10.0	741.6 ± 55.0	783.8	1.6	732.6 ± 46.8	98.9
5 168h	695.5 ± 1.6		696.2	1.9
6 168h	718.2 ± 4.0		120.0	596.2
4 336h	907.2 ± 0.1	855.0 ± 75.3	1037.6	8.8	977.9 ± 122.7	114.2
5 336h	899.0 ± 11.5		1048.3	2.8
6 336h	758.9 ± 21.4		8.4	827.8
4 504h	855.3 ± 6.7	810.0 ± 74.0	966.8	22.5	917.3 ± 123.1	113.0
5 504h	860.0 ± 3.3		987.3	<LOQ (see 2)
6 504h	714.8 ± 11.7		<LOQ (see 2)	775.2
4 672h	826.5 ± 1.5	782.3 ± 78.2	940.6	31.4	900.8 ± 127.8	114.9
5 672h	838.5 ± 2.7		977.1	<LOQ (see 2)
6 672h	681.8 ± 13.2		1.5	751.7

LOD:     

1. Limit of detection (HPLC coupled to ICP-MS 7700) LOD As (III) = 0.18 µg/L, LOD As (V) = 0.12 µg/L;

2. Limit of detection (HPLC coupled to ICP-MS 7500) LOD As (III) = 0.22 µg/L, LOD As (V) = 0.35 µg/L

LOQ:

1. Limit of quantification (HPLC coupled to ICP-MS 7700) LOQ As (III) = 0.66 µg/L, LOQ As (V) = 0.45 µg/L;

2. Limit of detection (HPLC coupled to ICP-MS 7500) LOQ As (III) = 0.78 µg/L, LOQ As (V) = 1.26 µg/L

Conclusions:

Under the described conditions of this test with arsenic metal (grain size approx. 1 mm) at a loading of 1 mg/L, mean dissolved arsenic concentrations after 7 days amounted to 750.7 ± 326.4 µg/L at pH 8 and 741.6 ± 55.0 µg/L at pH 6 whereas mean dissolved arsenic concentrations after 28 days amounted to 663.2 ± 285.3 µg/L and 782.3 ± 78.2 µg/L at pH 8 and pH 6, respectively. Whereas predominantly trivalent arsenic species (As (III)) were identified in two replicates, predominantly pentavalent arsenic species (As (V)) were found in the respective third replicate at pH 8 and pH 6. Based on these results, it can be concluded that arsenic metal is soluble with arsenate and arsenite species being the bioavailable forms of arsenic in environmental media.

Description of key information

The solubility of arsenic metal was investigated in water and in artificial physiological media, as well as the transformation/dissolution behaviour of arsenic metal in environmental media.

The data on water solubility (for details see endpoint study record for reference Klawonn (2010)) are presented in detail in the technical dossier section 4.8: under the conditions of an experimental study in accordance with OECD TG 105 and at a loading of ca. 0.5 g/L of granular As (2-15 mm), the solubility of arsenic metal was determined to ca. 10.6 mg/L after stirring for 8 days under an argon atmosphere to exclude oxidation processes. This is the mean result of dissolved As from two flasks and two time points (168 and 192h). In other words, only ca. 2% (by weight) of the arsenic dissolved under these conditions. However, the water solubility may be expected to vary based on various parameters such as particle size, surface area, loading and stirring time, so that a single figure for a “saturation water solubility” cannot be given.

 The bioaccessibility of granular As (ca. 1 mm grains) in artificial physiological media (see reference Knopf, 2012) is presented in the technical dossier section 7.1.1. (basic toxicokinetics): in an attempt to quantify the risk of systemic exposure to arsenic via any ingestion of granular arsenic, the solubility in artificial gastric juice (hydrochloric acid at pH=1.5) was investigated. Under the conditions of this test (flasks with artificial gastric fluid; loadings of 100 mg As metal per litre, grain size approx. 1 mm, 37°C, sampling after 2 and 24 h), the dissolved fractions of arsenic were 0.7 % and 3.8 % after 2 and 24 h, respectively. In conclusion, all dissolved As was effectively present in trivalent form As(III) at both time points.

 

The bioaccessibility of arsenic metal powder (D50 ca. 41µm) in artificial physiological media (reference Kirby, 2012) is presented in the technical dossier section 7.1.1. (basic toxicokinetics): in addition to the tests on larger, granular arsenic grains as described above, the solubility of arsenic metal powder in artificial biological fluids was also studied. Whereas arsenic is usually marketed and used in granular form, a powder sample prepared specifically for this test by crushing the grains and sieving through a 200µm sieved was subjected to the conditions of this test. The particle size distribution of this sample was determined by laser diffraction, yielding D10 = 9 µm, D50 = 41 µm and D90=104 µm. The dissolution of this arsenic metal powder in four different artificial physiological fluids after various test times is described in terms of the dissolved fraction (% As dissolved of As added) as follows: gastric fluid, pH=1.5: 2 h: 36.85 %, 24 h: 105 %; Interstitial fluid, pH= 7.4: 72 h: 10.065 %, 168 h: 25.35 %; Lysosomal fluid, pH= 4.5-5.0: 72 h: 99.8 %, 168 h: 106 %; Artificial perspiration, pH=6.5:72 h: 25.55 %, 168 h: 42.2 %.

 

For the sake of completeness, also the results of a transformation/dissolution test (for details see endpoint study record for reference Knopf (2014) in the technical dossier section 4.8) are summarised here briefly: in lieu of a harmonised guideline for in-vitro bioaccessibility test, the test was conducted in adaptation of guidance for OECD-Series on testing and assessment Number 29 and according test protocols discussed with the sponsor. Under the described conditions of this test with arsenic metal (grain size approx. 1 mm) at a loading of 1 mg/L, the mean dissolved arsenic concentrations after 7 days amounted to 750.7±326.4 µg/L at pH 8 and 741.6±55.0 µg/L at pH 6, whereas mean dissolved arsenic concentrations after 28 days amounted to 663.2±285.3 µg/L and 782.3±78.2 µg/L at pH 8 and pH 6, respectively. Mainly trivalent arsenic species (As (III)) were detected in the majority of test solutions with two exceptions, where predominantly pentavalent arsenic species (As (V)) were found.